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Decline of disjunct green salamander (Aneides aeneus) populations in the southern Appalachians
Abstract
Coincident with other amphibians around the world Aneides aeneus, a terrestrial plethodontid salamander, suffered a population collapse in a disjunct portion of its range in the mid–late 1970s. Long-term monitoring of seven historical green salamander populations throughout the 1990s showed a 98% decline in relative abundance since 1970. Three out of six populations first discovered in 1991 also crashed in 1996–1997. The synchronized suddenness of the declines, their region-wide impact, and effects on both small and larger populations, suggest the role of a novel agent of mortality beginning in the mid–late 1970s. Acting alone, but more likely in concert, habitat loss, overcollecting, epidemic disease and climate change could account for this region-wide decline.
... Prior to the mid-1970s, Green Salamanders occurred at relatively high densities on the Blue Ridge Escarpment (Bruce, 1968;Gordon, 1952;Snyder, 1971). However, a dramatic decline occurred in the mid-1970s (Snyder, 1991) and continued at least through the 1990s (Corser, 2001;Wilson, 2001) with no definitive known causes (Corser, 2001). Populations have continued to decline on the Blue Ridge Escarpment through the last 2 decades (Williams, unpubl. ...
... Prior to the mid-1970s, Green Salamanders occurred at relatively high densities on the Blue Ridge Escarpment (Bruce, 1968;Gordon, 1952;Snyder, 1971). However, a dramatic decline occurred in the mid-1970s (Snyder, 1991) and continued at least through the 1990s (Corser, 2001;Wilson, 2001) with no definitive known causes (Corser, 2001). Populations have continued to decline on the Blue Ridge Escarpment through the last 2 decades (Williams, unpubl. ...
... report). Numerous authors have speculated that seasonal drought during the brooding period is a possible factor for breeding failure (e.g., Corser, 2001;Petranka, 1998;Snyder, 1971). However, these speculations are based on few observations. ...
... Widespread declines in amphibians have been reported in the Appalachian Mountain region since the 1970s (Mitchell et al. 1999, Corser 2001, Muletz et al. 2014. Corser (2001) reported that of the 71 species of amphibians that inhabit the five-state region of the Appalachian Mountains almost half were listed as being of conservation concern by federal, state and Natural Heritage programmes in all or a portion of their ranges regionally. ...
... Widespread declines in amphibians have been reported in the Appalachian Mountain region since the 1970s (Mitchell et al. 1999, Corser 2001, Muletz et al. 2014. Corser (2001) reported that of the 71 species of amphibians that inhabit the five-state region of the Appalachian Mountains almost half were listed as being of conservation concern by federal, state and Natural Heritage programmes in all or a portion of their ranges regionally. Identified threats include habitat loss, collection for the wildlife trade, acid precipitation and introduced species, including harmful pathogens (Mitchell et al. 1999, Corser 2001. ...
... Corser (2001) reported that of the 71 species of amphibians that inhabit the five-state region of the Appalachian Mountains almost half were listed as being of conservation concern by federal, state and Natural Heritage programmes in all or a portion of their ranges regionally. Identified threats include habitat loss, collection for the wildlife trade, acid precipitation and introduced species, including harmful pathogens (Mitchell et al. 1999, Corser 2001. ...
The anthropogenic spread of disease from captive to wild amphibian populations (referred to as spillover) is linked to global amphibian declines. Disinfecting procedures and protocols exist to mitigate pathogen transmission to and within natural areas, but understanding of visitor attitudes and behaviour regarding their adoption is limited. We surveyed visitors in two natural areas in a global amphibian biodiversity hotspot to assess their attitudes regarding pathogen spread in such areas and analysed the factors influencing their behavioural intentions to take specific actions to prevent pathogen spillover. Visitors’ willingness to take action was influenced by their attitudes, behavioural control and trust in wildlife/land managers, whereas socio-demographic characteristics were less influential. These findings help us to understand visitor behaviour with respect to amphibian biosecurity in natural areas and inform enhanced biosecurity measures and strategic messaging to reduce pathogen spillover.
... We used green salamanders, Aneides aeneus (Cope and Packard 1881), to assess the influence of adding physiological mechanisms to correlative SDMs. Green salamanders are a near threatened species that have experienced population declines in the Blue Ridge Escarpment (BRE) portion of their range (North Carolina, South Carolina and Georgia) beginning in the 1970s (Snyder 1983, Corser 2001. In addition to habitat loss, over-collection and disease, climate change has also been implicated as a threat to this species due to the direct effects of warmer, drier environments limiting their ability to forage and find mates (Corser 2001, Riddell et al. 2018. ...
... Green salamanders are a near threatened species that have experienced population declines in the Blue Ridge Escarpment (BRE) portion of their range (North Carolina, South Carolina and Georgia) beginning in the 1970s (Snyder 1983, Corser 2001. In addition to habitat loss, over-collection and disease, climate change has also been implicated as a threat to this species due to the direct effects of warmer, drier environments limiting their ability to forage and find mates (Corser 2001, Riddell et al. 2018. Several correlative models have been applied to green salamanders in all or parts of their range (Lipps 2005, Barrett et al. 2014, Hardman 2014. ...
... It is also commonly used to generate distribution models of climate vulnerability (Pearson et al. 2007, Loarie et al. 2008, Puschendorf et al. 2009, Bradley et al. 2010. We focused on the disjunct population of green salamanders (North Carolina, South Carolina and Eastern Georgia), excluding the recently described Hickory Nut Gorge green salamander Aneides caryaensis (Patton et al. 2019), due to evidence of their recent population declines (Snyder 1983, Corser 2001. Genetic studies have revealed that this disjunct population is an evolutionarily significant unit from the mainland population (Patton et al. 2019). ...
Rapid global change has increased interest in developing ways to identify suitable refugia for species of conservation concern. Correlative and mechanistic species distribution models (SDMs) represent two approaches to generate spatially‐explicit estimates of climate vulnerability. Correlative SDMs generate distributions using statistical associations between environmental variables and species presence data. In contrast, mechanistic SDMs use physiological traits and tolerances to identify areas that meet the conditions required for growth, survival and reproduction. Correlative approaches assume modeled environmental variables influence species distributions directly or indirectly; however, the mechanisms underlying these associations are rarely verified empirically. We compared habitat suitability predictions between a correlative‐only SDM, a mechanistic SDM and a correlative framework that incorporated mechanistic layers (‘hybrid models'). Our comparison focused on green salamanders Aneides aeneus, a priority amphibian threatened by climate change throughout their disjunct range. We developed mechanistic SDMs using experiments to measure the thermal sensitivity of resistance to water loss (ri) and metabolism. Under current climate conditions, correlative‐only, hybrid and mechanistic SDMs predicted similar overlap in habitat suitability; however, mechanistic SDMs predicted habitat suitability to extend into regions without green salamanders but known to harbor many lungless salamanders. Under future warming scenarios, habitat suitability depended on climate scenario and SDM type. Correlative and hybrid models predicted a 42% reduction or 260% increase in area considered to be suitable depending on the climate scenario. In mechanistic SDMs, energetically suitable habitat declined with both climate scenarios and was driven by the thermal sensitivity of ri. Our study indicates that correlative‐only and hybrid approaches produce similar predictions of habitat suitability; however, discrepancies can arise for species that do not occupy their entire fundamental niche, which may hold consequences of conservation planning of threatened species.
... Populations in the BRE have been the subject of long-term study. Before the 1970s, high densities of the green salamander were reported in the BRE (Snyder 1983;Corser 2001). Subsequently, the BRE population in South Carolina likely dramatically declined during (Mitchell et al. 1999). ...
... Subsequently, the BRE population in South Carolina likely dramatically declined during (Mitchell et al. 1999). In the 1990s, further study of 7 sites in the BRE observed a 98% decline in relative abundance compared to reports of the same sites in the 1970s (Corser 2001). ...
... Results determined that the declines had no correlation with initial population size, elevation, or forest community type. Instead, the decline was attributed to habitat loss, epidemic disease, collection, and/or climate conditions (Corser 2001). ...
The Conservation Action Plan (CAP) offers a comprehensive overview of the Green Salamander (Aneides aeneus) species, encompassing its taxonomy, distribution, and ecology. Designed to support the petition to the U.S. Fish and Wildlife Service for an elevated listing of the Green Salamander under the Endangered Species Act, this report is a pivotal component of our broader effort within the Partners in Amphibian and Reptile Conservation initiative. The aim is to provide specific management practices that can function as practical guidelines for land managers, enabling the effective implementation of conservation and management actions that yield positive benefits for this remarkable species.
... Plethodontid salamanders in North America are known to be susceptible to the pathogens of several emerging infectious diseases such as Batrachochytrium dendrobatidis (Bd; Vasquez et al. 2009), Batrachochytrium salamandrivorans (Bsal; Martel et al 2014), and Ranavirus (Gray et al. 2009a). In the eastern United States, disease was suggested as a threat to Green Salamanders (Aneides aeneus) in the early 2000s (Corser 2001), and more recently it was recognized that Green Salamanders may be vulnerable to several emerging infectious diseases (Blackburn et al. 2015;Moffitt et al. 2015). Further, Green Salamanders have experienced population declines, particularly in the Carolinas and Georgia (known as the disjunct range of this species ;Snyder 1983;Corser 2001;Wilson 2001). ...
... In the eastern United States, disease was suggested as a threat to Green Salamanders (Aneides aeneus) in the early 2000s (Corser 2001), and more recently it was recognized that Green Salamanders may be vulnerable to several emerging infectious diseases (Blackburn et al. 2015;Moffitt et al. 2015). Further, Green Salamanders have experienced population declines, particularly in the Carolinas and Georgia (known as the disjunct range of this species ;Snyder 1983;Corser 2001;Wilson 2001). Threats to salamander populations in this disjunct range include habitat loss, climate change, disease, and over-collection (Corser 2001). ...
... Further, Green Salamanders have experienced population declines, particularly in the Carolinas and Georgia (known as the disjunct range of this species ;Snyder 1983;Corser 2001;Wilson 2001). Threats to salamander populations in this disjunct range include habitat loss, climate change, disease, and over-collection (Corser 2001). NatureServe (2018) categorized Green Salamanders as "critically imperiled" in South Carolina, USA. ...
... Although they have been observed to exhibit arboreal tendencies, they typically are restricted to areas harboring rock outcrops (Gordon, 1952;Waldron and Humphries, 2005;Smith et al., 2017). A large number of nesting sites have been detected on rock faces (but see Pope, 1928), which may in turn lead breeding populations to be patchily distributed (Petranka, 1998;Corser, 2001). In the 1970s, green salamander populations collapsed in the disjunct Blue Ridge Escarpment (Snyder, 1983(Snyder, , 1991Corser, 2001). ...
... A large number of nesting sites have been detected on rock faces (but see Pope, 1928), which may in turn lead breeding populations to be patchily distributed (Petranka, 1998;Corser, 2001). In the 1970s, green salamander populations collapsed in the disjunct Blue Ridge Escarpment (Snyder, 1983(Snyder, , 1991Corser, 2001). However, those outside of the escarpment within the western portion of their range remained stable (Snyder, 1991). ...
... However, those outside of the escarpment within the western portion of their range remained stable (Snyder, 1991). Corser (2001) studied trends in several populations in the Blue Ridge Escarpment throughout the 1990s and found a 98% decline in relative abundance since 1970; extensive surveys over the last 30 years by the North Carolina Wildlife Resources Commission (NCWRC) indicate that declines appear to have continued in these populations over the last decade and a half. ...
Green salamanders (Plethodontidae: Aneides aeneus) are rock outcrop habitat specialists, possessing numerous unique morphological adaptations (e.g., prehensile tail and squared toe-pads) for climbing. Some authors believe A. aeneus, which is widely distributed across the Appalachian Mountains of the inland eastern United States, comprises a species complex due to substantial karyotypic variation among populations. We conducted a population genetic and phylogenetic study across the range of A. aeneus and discovered substantial genetic structure, including four distinct lineages, one of which we describe as Aneides caryaensis, new species. Restricted to a narrow geographic distribution in western North Carolina, this species faces pressing conservation threats due to rapid real estate and tourism development in the area. We also recommend the recognition of three geographically distinct and reciprocally monophyletic lineages as evolutionarily significant units due to strong mitochondrial and nuclear differentiation among them. Aneides aeneus has been petitioned for listing under the Endangered Species Act, and our study further highlights the need for conservation management of this complex. Our formal recognition of the extent of genetic and evolutionary diversification of the complex is a critical step in establishing conservation strategies.
... The green salamander is listed as a Federal Species of Concern (LeGrand et al., 2014), and is currently under status review because of its continual decline throughout its range (Federal Register, 2015). Threats to the species include loss and alteration of habitat, over-collecting, epidemic disease, and climate change (Corser, 2001;Wilson, 2001). ...
... Prior to the mid-1970s, green salamanders occurred at relatively high densities on the escarpment (Gordon, 1952;Bruce, 1968;Snyder, 1971). However, a dramatic decline in populations occurred in the mid-late 1970s (Snyder, 1991), and continued at least through the 1990s (Corser, 2001;Wilson, 2001), with no definitive causes known (Corser, 2001). Since Corser (2001), no quantitative studies have been published regarding the reproductive success of this species. ...
... Prior to the mid-1970s, green salamanders occurred at relatively high densities on the escarpment (Gordon, 1952;Bruce, 1968;Snyder, 1971). However, a dramatic decline in populations occurred in the mid-late 1970s (Snyder, 1991), and continued at least through the 1990s (Corser, 2001;Wilson, 2001), with no definitive causes known (Corser, 2001). Since Corser (2001), no quantitative studies have been published regarding the reproductive success of this species. ...
ABSTRACT.—We examined relationships between nest success and attributes of brood
crevices in rock outcrops used by green salamanders (Aneides aeneus) on the Blue Ridge
Escarpment from 2010 to 2015. We used data from a long-term monitoring program by the
North Carolina Wildlife Resources Commission and defined nest success as evidence of at
least one egg hatching in a clutch. We georeferenced all rock outcrops with nesting green
salamanders and calculated straight-line distances to closest outcrops with nesting green
salamanders using ArcGIS. A total of 2578 rock outcrops during six nesting seasons were
surveyed to determine nest success for 168 nests in 88 crevices from 74 outcrops. Where all
crevices could be thoroughly surveyed, attributes of brood crevices (N=29) and
corresponding random crevices at 29 rock outcrops were quantified. Nest success during
the 6 y period ranged from 73–92% and was not related to year or any crevice attribute. There
was a negative relationship between nest success and straight-line distance to outcrop with
nesting green salamanders, and crevices that contained one successful nest were more likely
to have a successful nest in another year. Females selected brood crevices that were higher
above the ground and shorter in length than those randomly available on the outcrop. These
results suggest that the odds of a green salamander having a successful nest decrease as the
distance to the closest rock outcrop with other nesting individuals increases. Female green
salamanders select brood crevices with attributes that likely minimize direct competition and
nest predation from other species of salamanders as well as other predators in genera.
... Snyder (1983) noted that Green Salamanders in the Carolinas are close to extirpation. Corser (2001) acknowledges four major threats facing Green Salamanders: habitat loss, climate change, overcollection of the species, and disease. Researchers have documented that this species is capable of dispersing between 42 and 54 m from the nearest rock outcrop (Waldron and Humphries, 2005;Riedel et al., 2006); therefore, researchers think leaving forested buffers around outcrops during clearcutting is important (Petranka, 1998;Wilson, 2001;Waldron and Humphries, 2005). ...
... Researchers have documented that this species is capable of dispersing between 42 and 54 m from the nearest rock outcrop (Waldron and Humphries, 2005;Riedel et al., 2006); therefore, researchers think leaving forested buffers around outcrops during clearcutting is important (Petranka, 1998;Wilson, 2001;Waldron and Humphries, 2005). The BRE has experienced warmer summer temperatures and colder winter temperatures since the 1960s, and like many other amphibians of high conservation priority, the Green Salamander is expected to lose a significant amount of its climatically suitable habitat in the next half-century (Snyder, 1991;Corser, 2001;Barrett et al., 2014). Nevertheless, the Carolinas have been identified as an area of resilience to climatic change relative to many other parts of the range (Barrett et al., 2014). ...
... Nevertheless, the Carolinas have been identified as an area of resilience to climatic change relative to many other parts of the range (Barrett et al., 2014). Overcollection of Green Salamanders (which are collected for their attractiveness) could potentially lead to population declines (Corser, 2001;Wilson, 2001). For example, continual collection of egg-brooding Green Salamanders from the same site over consecutive years can result in population decline (Wilson, 2001). ...
Green Salamanders, Aneides aeneus, are habitat specialists found in narrow crevices of rock outcrops and under flaky bark of trees. The species has a high conservation priority throughout its range and has been negatively affected by habitat loss, climate change, disease, and overcollection. In portions of the Blue Ridge Escarpment population, many historical locations for this species have not been visited since the 1980s or earlier. Across three counties in South Carolina, we conducted visual encounter surveys of known rock outcrops that were accessible, and used binoculars to conduct arboreal surveys in the adjacent forest. We detected Green Salamanders at 30 of the 61 sites surveyed (49.2%). We collected a variety of habitat variables and compared a suite of N-mixture models using an Akaike information criterion framework. Detection probability was positively influenced by time of day. A model of abundance that included aspect, habitat size, and elevation had the most support. Specifically, Green Salamanders were more abundant at larger sites at lower elevations with south-facing slopes. Knowledge of factors that influence population abundance will help guide future efforts to protect the species in the southern portion of its range.
... Ponds are often taken as a survey unit, and fewer occupied ponds over time may be interpreted as an indicator of decline. Concern over amphibian decline has led to numerous investigators revisiting old survey data to establish a baseline for evaluating historic occupancy and rate of decline (e.g., Cassani et al., 2015;Corser 2001;Drost and Fellers 1996;Fellers and Drost 1993;Fisher and Shaffer 1996;Graham et al., 2011;Highton 2005;Johnson et al., 2011;Marsh and Trenham 2008;Moskwik 2014;Palis 1997;Skelly et al., 2003). Such retrospective studies pose unique challenges for inference. ...
... Studies that utilized all historic sites (not just those initially occupied) in their resurvey include Cassani et al. (2015), Drost and Fellers (1996), Fellers and Drost (1993), and Moskwik (2014). Surveys potentially confounded by only focusing on initially occupied sites include Bradford et al. (1994), Corser (2001), Fisher and Shaffer (1996), Graham et al. (2011), Highton (2005, Johnson et al. (2011), andPalis (1997). These lists are by no means exhaustive. ...
... This approach, however, may lead to a false inference of decline because of the turnover/detectability effect which can result from colonization/extinction processes, population fluctuations, and detectability issues. In several studies noted here, expanded sampling located additional occupied sites (e.g., Corser 2001;Drost and Fellers 1996;Palis 1997). Only longer-term and spatially-extensive data can allow determination of the dynamics of such potential metapopulations. ...
In retrospective studies, discrete population units such as ponds may be resurveyed at a later time using only the set of initially occupied sites. There are possible confoundings that affect estimates of occupancy change under these conditions. For most possible parameter values for a metapopulation, simulations and analytical results show that turnover leads to a tendency to observe a decline in the proportion of initially occupied sites that are occupied at a later time even when the overall metapopulation is stable or increasing. For a given time interval, the spurious decline will be greater when metapopulation turnover is higher. If site-level detectability d is <1, a single resurvey of only the initially occupied sites will show a decline of 1-d even if no change has taken place. Finally, volatile populations can be difficult to resurvey, especially if sample units are chosen based on having an abundance of the species at the earlier survey. All three issues can exist simultaneously and their influence on trend estimates can be difficult to distinguish based on samples at only two points in time. A sample of literature illustrates clear cases where these biases could exist, even though a variety of survey methods were used. Suggestions are made for improved sampling, including resampling the entire original set of sites and conducting multi-year resurveys.
... There are more than two hundred salamander taxa identified in the United States, and at least 29% are ranked by NatureServe as "imperiled or critically imperiled" in a portion of their ranges (roughly equivalent to the IUCN's Red List designation of "critically endangered," "endangered," and "vulnerable") [33]. Potential and established reasons for their decline include forest fragmentation and habitat alteration [41], land use disturbance and urbanization [42,43], epidemic disease [44,45], climate change [44,46], pollutants/contaminants [44,45], acidic deposition [47,48], harvest/predation [45,49], and interactions between these factors [50]. To direct conservation and management efforts in the United States and worldwide, it is important to understand, as thoroughly and holistically as possible, the roles of environmental parameters and the impacts of human activities on salamander abundance and diversity. ...
... There are more than two hundred salamander taxa identified in the United States, and at least 29% are ranked by NatureServe as "imperiled or critically imperiled" in a portion of their ranges (roughly equivalent to the IUCN's Red List designation of "critically endangered," "endangered," and "vulnerable") [33]. Potential and established reasons for their decline include forest fragmentation and habitat alteration [41], land use disturbance and urbanization [42,43], epidemic disease [44,45], climate change [44,46], pollutants/contaminants [44,45], acidic deposition [47,48], harvest/predation [45,49], and interactions between these factors [50]. To direct conservation and management efforts in the United States and worldwide, it is important to understand, as thoroughly and holistically as possible, the roles of environmental parameters and the impacts of human activities on salamander abundance and diversity. ...
... There are more than two hundred salamander taxa identified in the United States, and at least 29% are ranked by NatureServe as "imperiled or critically imperiled" in a portion of their ranges (roughly equivalent to the IUCN's Red List designation of "critically endangered," "endangered," and "vulnerable") [33]. Potential and established reasons for their decline include forest fragmentation and habitat alteration [41], land use disturbance and urbanization [42,43], epidemic disease [44,45], climate change [44,46], pollutants/contaminants [44,45], acidic deposition [47,48], harvest/predation [45,49], and interactions between these factors [50]. To direct conservation and management efforts in the United States and worldwide, it is important to understand, as thoroughly and holistically as possible, the roles of environmental parameters and the impacts of human activities on salamander abundance and diversity. ...
Salamanders and riparian forests are intimately interconnected. Salamanders are integral to ecosystem functions, contributing to vertebrate biomass and complex food webs in riparian forests. In turn, these forests are critical ecosystems that perform many environmental services, facilitate high biodiversity and species richness, and provide habitat to salamander populations. Due to the global decline of amphibians, it is important to understand, as thoroughly and holistically as possible, the roles of environmental parameters and the impact of human activities on salamander abundance and diversity in riparian forests. To determine the population responses of salamanders to a variety of environmental factors and anthropogenic activities, we conducted a review of published literature that compared salamander abundance and diversity, and then summarized and synthesized the data into general patterns. We identify stream quality, leaf litter and woody debris, riparian buffer width, and soil characteristics as major environmental factors influencing salamander populations in riparian forests, describe and explain salamander responses to those factors, and discuss the effects of anthropogenic activities such as timber harvest, prescribed fires, urbanization, road construction, and habitat fragmentation. This review can assist land and natural resource managers in anticipating the consequences of human activities and preparing strategic conservation plans.
... The Green Salamander (Aneides aeneus) is distributed from extreme southwest Pennsylvania, USA to northern Alabama and Mississippi with a disjunct population in southern North Carolina, northeastern Georgia, and northern South Carolina (Petranka 1998). Because of unique habitat requirements, Green Salamanders are thought to be at risk of range-wide declines and extirpations (Corser 2001). Green Salamanders primarily dwell in rock crevices within rock outcrops (Gordon 1952;Rossell et al. 2009). ...
... Green Salamander populations, especially those in the disjunct Carolina populations, have experienced declines and extirpations (Snyder 1991;Corser 2001). From the 1970s to 1980s local extirpations occurred in once-abundant North Carolina populations (Snyder 1991), and since the 1980s reductions of up to 98% have occurred in remaining populations (Corser 2001). ...
... Green Salamander populations, especially those in the disjunct Carolina populations, have experienced declines and extirpations (Snyder 1991;Corser 2001). From the 1970s to 1980s local extirpations occurred in once-abundant North Carolina populations (Snyder 1991), and since the 1980s reductions of up to 98% have occurred in remaining populations (Corser 2001). One of the most-studied Blue Ridge escarpment populations was located at Biscuit Rock (Highlands, North Carolina;Gordon 1952;Snyder 1991;Corser 2001), and in the past five years this population became extirpated without a definitive cause (Lori Williams, unpubl. ...
... Green Salamanders have experienced historic declines associated with habitat disturbance (Snyder 1991;Corser 2001;Staudt et al. 2013), leading many researchers to recommend the preservation of intact buffers of undisturbed woody vegetation directly adjacent to rock outcrops as a best management practice (Petranka 1998;Waldron and Humphries 2005;Miloski 2010;Hinkle et al. 2018). Although the widths of recommended buffers vary, these recommendations assume that woody Smith-Crevice salamander microclimate. ...
... The effect that less destructive activities, such as less intensive vegetation removal, has on the microclimatic characteristics of crevices is unknown. Several researchers have also implicated timber harvesting adjacent to or near rock outcrops as a contributor to Green Salamander declines (Corser 2001;Wilson 2003), although the potential impacts of these more expansive vegetation manipulations on temperature and moisture levels in and around Smith-Crevice salamander microclimate. ...
Anthropogenic vegetation removal is a major source of disturbance for rock outcrops embedded within forest habitats, particularly for rock outcrop specialists of high conservation concern such as those in the Green Salamander (Aneides aeneus) complex. Researchers have long advocated for the preservation of forested buffers around rock outcrop habitat to safeguard crevices used by Green Salamanders against extreme temperatures and to maintain high moisture levels, although scant empirical data exists in the literature to support these recommendations. I performed a season-long survey of microclimatic characteristics within crevice refugia at a rock outcrop complex in the Cumberland Mountains of southwestern Virginia, USA, experiencing recent Green Salamander declines coincident with woody understory removal for rock climbing development. Crevices in outcrops experiencing adjacent understory vegetation removal were up to three times warmer and six times drier than crevices not impacted by the development of climbing routes. The forest canopy remained intact at both sites, which suggests the potential for negative impacts of understory vegetation removal on resident salamanders.
... Numerous outcrop-specialized plant species exhibit low levels of genetic diversity and population size across portions of the Appalachian Mountain region of North America (Godt et al. 1996), while outcrop-specialized vertebrate taxa from the same region harbor cryptic, microendemic diversity (Patton et al. 2019). Such species are accordingly receiving an increasing focus in regional conservation monitoring and management efforts (Wiser and White 1999;Corser 2001;Ford et al. 2006;Ulrey et al. 2016). In particular, researchers across multiple states are currently in the midst of efforts to survey rock outcrops for outcropspecialist amphibians, such as green salamanders Aneides aeneus ( Figure 1A), that are undergoing review for possible listing as threatened or endangered pursuant to the U.S. Endangered Species Act (ESA 1973, as amended; Giese et al. 2012;Smith et al. 2015;Newman et al. 2018;John et al. 2019). ...
... This particular outcrop feature (an erosional remnant) was isolated from other outcrops, harbored a nesting site for green salamanders, and was only detected by LiDAR data. salamanders have high conservation priority across their range, especially in terms of public forest management activities, due to their high degree of habitat specificity (Gordon 1952;Petranka 1998), past observed population declines (Snyder 1983), and ongoing threats to existing populations (Corser 2001;Hinkle et al. 2018). As a result, multiple state wildlife agencies and federal land management agencies are engaged in inventory and monitoring for green salamanders throughout the species' range (Newman et al. 2018;Rossell et al. 2019;Smith et al. 2019). ...
The identification of small habitat features embedded within forest ecosystems is a challenge for many wildlifeinventory and monitoring programs, especially for those involving rock outcrop specialist taxa. Rock outcrops are oftendifficult to remotely detect in dense Appalachian hardwood forests, as most outcrops remain hidden under the forestcanopy and therefore invisible when relying on aerial orthoimagery to pinpoint habitat features. We investigated theability for light detection and ranging point cloud data to identify small rock outcrops during the environmentalassessment phase of a proposed management project on the Jefferson National Forest in Virginia. We specifically compared this approach with the visual identification of rock outcrops across the same area using aerial orthoimagery. Our light detection and ranging-based approach identified three times as many rock outcrop sites as aerial orthoimagery, resulting in the field verification of four times as many previously unknown populations of green salamanders Aneides aeneus (a rock outcrop specialist amphibian of high conservation concern) than would have been possible if relying on aerial orthoimagery alone to guide surveys. Our results indicate that light detection and ranging-based methods may provide an effective, efficient, and low-error approach that can remotely identify below-canopy rock outcrops embedded within Appalachian forests, especially when researchers lack pre-existing knowledge of local terrain and the location of habitat features.
... Numerous outcrop-specialized plant species exhibit low levels of genetic diversity and population size across portions of the Appalachian Mountain region of North America (Godt et al. 1996), while outcrop-specialized vertebrate taxa from the same region harbor cryptic, microendemic diversity (Patton et al. 2019). Such species are accordingly receiving an increasing focus in regional conservation monitoring and management efforts (Wiser and White 1999;Corser 2001;Ford et al. 2006;Ulrey et al. 2016). In particular, researchers across multiple states are currently in the midst of efforts to survey rock outcrops for outcropspecialist amphibians, such as green salamanders Aneides aeneus ( Figure 1A), that are undergoing review for possible listing as threatened or endangered pursuant to the U.S. Endangered Species Act (ESA 1973, as amended; Giese et al. 2012;Smith et al. 2015;Newman et al. 2018;John et al. 2019). ...
... We initiated an effort in early 2020 to survey rock outcrops within a densely forested portion of the Jefferson National Forest in southwest Virginia for green salamanders (a rock outcrop specialist of high conservation concern [Giese et al. 2012]) as part of the environmental assessment of an area proposed for timber management activities by the United States Department of Agriculture (USDA) Forest Service. Green salamanders have high conservation priority across their range, especially in terms of public forest management activities, due to their high degree of habitat specificity (Gordon 1952;Petranka 1998), past observed population declines (Snyder 1983), and ongoing threats to existing populations (Corser 2001;Hinkle et al. 2018). As a result, multiple state wildlife agencies and federal land management agencies are engaged in inventory and monitoring for green salamanders throughout the species' range (Newman et al. 2018;Rossell et al. 2019;Smith et al. 2019). ...
The identification of small habitat features embedded within forest ecosystems is a challenge for many wildlife inventory and monitoring programs, especially for those involving rock outcrop specialist taxa. Rock outcrops are often difficult to remotely detect in dense Appalachian hardwood forests, as most outcrops remain hidden under the forest canopy and therefore invisible when relying on aerial orthoimagery to pinpoint habitat features. We investigated the ability for light detection and ranging (LiDAR) point cloud data to identify small rock outcrops during the environmental assessment phase of a proposed management project on the Jefferson National Forest in Virginia, USA. We specifically compared this approach to the visual identification of rock outcrops across the same area using aerial orthoimagery. Our LiDAR-based approach identified three times as many rock outcrop sites as aerial orthoimagery, resulting in the field-verification of four times as many previously-unknown populations of green salamanders Aneides aeneus, a rock outcrop specialist amphibian of high conservation concern, than would have been possible if relying on aerial orthoimagery alone to guide surveys. Our results indicate that LiDAR-based methods may provide an effective, efficient, and low-error approach that can remotely identify below-canopy rock outcrops embedded within Appalachian forests, especially when researchers lack pre-existing knowledge of local terrain and the location of habitat features.
... 15 They have experienced a 98% decline in relative abundance since the 1970s, and a causative agent of those declines has not been definitely identified. 7 The terrestrial behavior of the species is thought to be an attribute that could limit their exposure to Bd, which is a waterborne pathogen. 7 However, that may also lead to naivety to the pathogen and increased susceptibility when exposed. ...
... 7 The terrestrial behavior of the species is thought to be an attribute that could limit their exposure to Bd, which is a waterborne pathogen. 7 However, that may also lead to naivety to the pathogen and increased susceptibility when exposed. In the wild, relatively few reports are recorded in this species. ...
A chytridiomycosis outbreak from Batrachochytrium dendrobatidis ( Bd) in a mixed-species plethodontid salamander exhibit resulted in four green salamander ( Aneides aeneus) deaths. One green salamander died before treatment, and three died during treatment with daily 0.005% itraconazole baths. All salamanders had evidence of severe Bd infections via cytology, histopathology, and/or polymerase chain reaction (PCR) at the time of death. Ten long-tailed salamanders ( Eurycea longicauda) and one two-lined salamander ( Eurycea bislineata) that shared the enclosure were initially negative for Bd on quantitative PCR but were prophylactically treated with daily 0.01% itraconazole baths for 11 days. Posttreatment testing yielded eight long-tailed salamanders and one two-lined salamander positive for Bd with low gene equivalents. All salamanders were negative after two to three treatment courses, and there were no additional mortalities. The difference in mortality and fungal load suggested that genus Aneides salamanders may be more susceptible to Bd than genus Eurycea salamanders.
... Disjunct populations occur along the Blue Ridge Escarpment in North Carolina, South Carolina, and Georgia, as well as in southern Indiana. Documented local declines and extirpations of this species (Snyder 1991;Corser 2001), coupled with its presumed rarity and sensitivity to anthropogenic disturbance, have resulted in A. aeneus having formal protected status in six states (MDNR 2005;MMNS 2005;IDNR 2006;NCWRC 2014;ODNR 2014;PGCPBFC 2015), with all other remaining states across its range listing the species as of special conservation concern (GDNR 2005;SCDNR 2005;TWRA 2005;VDGIF 2005;ADCNR 2005;WVDNR 2005;KDFWR 2013). The species' preferred habitats (steep, isolated cliff and bluff systems; Fig. 2) and solitary behavior of seeking refugia in deep, inaccessible rock crevices have also predisposed this species to local data deficiency that hinders conservation efforts, especially in the Cumberland Mountains Province of the central Appalachian Mountains. ...
... Perhaps of most direct importance is the risk of citizen science efforts accidentally disseminating knowledge on the specific location of species of concern, especially those that are considered at risk of poaching and overcollecting. Aneides aeneus is a species that has been cited as being at-risk of localized overcollecting (Snyder 1991;Corser 2001), even leading some researchers to obscure the location of study sites in the scientific literature (Waldron and Humphries 2005). We were sensitive to these concerns in the design of our project and ensured that participants were not informed of specific A. aeneus localities in educational materials and that the locations of citizen observations were obscured in the online platform for submitting observations, therefore making the exact location of A. aeneus reports known only to the principal investigators and the individual(s) contributing each observation. ...
The Green Salamander (Aneides aeneus) is a secretive, arboreal cliff specialist distributed discontinuously across the southern and central Appalachian Mountains, USA. While intensively studied in some parts of its range in the Appalachian Plateau and Blue Ridge Provinces, the distribution of A. aeneus is still poorly understood, particularly in the Cumberland Mountains physiographic province of the Appalachian region. This data deficiency is partly the result of a lack of formal historic surveys across this region, coupled with a high amount of privately owned land that is inaccessible to traditional biotic surveys. We used a combination of citizen science efforts and traditional field surveys to investigate the distribution and status of A. aeneus across the Cumberland Mountains of southwestern Virginia, USA. Local landowners and outdoor recreation enthusiasts reported a relatively high rate of encounters with A. aeneus, verifying the species' persistence at four historic localities and leading to the discovery of 36 previously unknown populations. Although we are cautious about making inferences about the true conservation status of A. aeneus across this region given the scarcity of current data, these findings suggest that the distribution of A. aeneus in Virginia has been vastly underestimated and that expanded monitoring programs are needed to further ascertain this species' status. More broadly, our results illustrate the utility of coupling public initiatives with more traditional field surveys to expand the biogeographic knowledge of secretive, difficult-to-study amphibian species.
... We followed Highton's nomenclature based on his field notes when assigning populations to species (Table 1). From 1960to 2001, Highton (2005 repeatedly visited thousands of sites throughout the eastern United States. He collected over 17,000 plethodontid salamanders at 402 sites throughout the Park (Fig. 1) and deposited those animals and associated field notes at the U.S. National Museum of Natural History (USNM). ...
... Hunsaker & Potter, 1960;Houlahan et al., 2000). Recently, Corser (2001), Highton (2005) and Means & Travis (2007) have reported enigmatic population declines during the mid-1970s to 1980s in three genera of salamanders in three regions of the eastern United States. In no case have populations recovered or a cause been definitively identified. ...
Aim
Woodland salamanders (genus: P lethodon ) declined synchronously across many protected areas in E astern N orth A merica by the mid‐1980s, but no cause was attributed to these declines. We hypothesized that the rapid, synchronous loss of several populations of many species was consistent with the invasive pathogen B atrachochytrium dendrobatidis ( B d ), and we resurveyed historic sites to search for Bd in current populations.
Location
G reat S moky M ountains N ational P ark.
Methods
We surveyed 35 sites 2–4 times between M arch and N ovember 2009, quantified community composition and abundance of 72 populations of six species and three hybrids of P lethodon salamanders, and collected 665 skin swabs to detect B d .
Results
At 22 of the 35 sites, we were unable to find one or more species that were historically present. P lethodon glutinosus and P . teyahalee and their hybrids were less abundant than historically found, P . jordani x metcalfi and P . ventralis were more abundant and the remaining three species fluctuated but showed no net change. Yet, only one of the 665 salamanders was positive for B d .
Main conclusions
Declines were not associated with particular localities, but occurred in particular species. We conclude that over collecting, logging, and acid rain are unlikely to have caused these population declines, but we were unable to rule out disease or climate change as contributing factors. Population declines of P lethodon salamanders in the Park are substantial and have persisted for 30 years. Determining the cause and the extent of these declines is important for managing this area of global salamander biodiversity.
... It is listed as critically imperiled, imperiled, or vulnerable in 10 of the 13 states in which it occurs. Interest in conservation of Green Salamanders piqued following a publication by Corser (2001), which reported a 98% decline of some populations within the Blue Ridge Escarpment since 1970. Speculation about why these populations declined has centered on synergistic effects of overcollection by researchers, fungal pathogens, climate change, and habitat loss (Corser, 2001). ...
... Interest in conservation of Green Salamanders piqued following a publication by Corser (2001), which reported a 98% decline of some populations within the Blue Ridge Escarpment since 1970. Speculation about why these populations declined has centered on synergistic effects of overcollection by researchers, fungal pathogens, climate change, and habitat loss (Corser, 2001). It is the latter component of such speculation that is of interest to this study. ...
Green Salamander (Aneides aeneus) habitat has been described traditionally as rock outcrop formations that contain moist, but not wet, crevices. Early studies of Green Salamander natural history claimed arboreal habitat was used secondarily to rock outcrops and in situations where more suitable habitat was unavailable. Although arboreal behavior of western Aneides has been well established, arboreal habitat has been deemed “not typical” for Green Salamanders. This study examined the extent to which Green Salamanders use arboreal habitat. Surveys were conducted between August 2001 and July 2004 at a study area in Pickens County, South Carolina. Salamander size influenced arboreal habitat use, but gender and reproductive condition did not. There was a positive relationship between tree diameter at breast height (DBH) and Green Salamander observations and a negative relationship between tree distance to rock outcrop and salamander observations. Tree selection did not reflect tree species relative dominance, and salamanders favored hardwoods over conifers. Seasonal use of arboreal habitat was distinct, implying that salamanders overwinter in rock outcrops and move into trees and logs at the onset of spring. Salamanders observed during summer were primarily arboreal, but they returned to rock outcrops in late fall. Researchers have largely overlooked arboreal habitat use by Green Salamanders, and consequently, the importance of arboreal habitat near rock outcrops has been underestimated. Arboreal habitat appears to be an important component of the life history of this declining species, and future survey and monitoring efforts should include searches of arboreal habitat.
... It is listed as critically imperiled, imperiled, or vulnerable in 10 of the 13 states in which it occurs. Interest in conservation of Green Salamanders piqued following a publication by Corser (2001), which reported a 98% decline of some populations within the Blue Ridge Escarpment since 1970. Speculation about why these populations declined has centered on synergistic effects of overcollection by researchers, fungal pathogens, climate change, and habitat loss (Corser, 2001). ...
... Interest in conservation of Green Salamanders piqued following a publication by Corser (2001), which reported a 98% decline of some populations within the Blue Ridge Escarpment since 1970. Speculation about why these populations declined has centered on synergistic effects of overcollection by researchers, fungal pathogens, climate change, and habitat loss (Corser, 2001). It is the latter component of such speculation that is of interest to this study. ...
Removal of vegetation directly surrounding a breeding pond has the potential to significantly alter the environmental conditions experienced by larval amphibians during development and, therefore, may affect the life history of this and subsequent life stages. In this study, we investigated growth, development, and survivorship of Litoria ewingii as a result of different shading conditions in a commercially logged forest in Tasmania, Australia. We specifically investigated responses in two types of breeding ponds available to the species: permanent ponds, and smaller ephemeral ponds. Increased shading in permanent ponds resulted in reduced survival. Larval growth and development did not respond significantly to shading treatment in permanent ponds but were significantly affected by pond elevation. In ephemeral ponds, increased shading resulted in decreased developmental rate and a higher coefficient of variation for size at metamorphosis. Our findings suggest that the larval success of L. ewingii is not likely to be enhanced by vegetative buffer zones around permanent pond margins but may be enhanced by ensuring heterogeneity of shading conditions around ephemeral ponds.
... In particular, very limited historical data is available for most populations to infer population trends. We do not know whether populations on the southern Cumberland Plateau have experienced declines similar to those reported for A. caryaensis and the Blue Ridge Escarpment populations (Snyder, 1983(Snyder, , 1991Corser, 2001;Patton et al., 2019). Encouragingly, recent surveys in Tennessee and northeastern Alabama confirmed the presence of species at 16 historical sites and discovered 34 new sites (Niemiller et al., 2020, in press). ...
Cryptic species present particular challenges to biodiversity conservation, as true species diversity and distributional boundaries remain obscured. However, modern molecular tools have afforded unparalleled opportunities to elucidate cryptic species, define their distributions, and, ultimately, develop conservation interventions to extend their evolutionary trajectories into the future. The Green Salamander (Aneides aeneus) complex provides an evolutionary focal point and the Appalachian Highlands an ecological context for the exploration of cryptic speciation in an imperiled taxon. A recent study uncovered significant levels of genetic and genomic variation geographically structured across the Appalachian Highlands, including up to four lineages, one of which (A. caryaensis) was described therein. Here we extend the genetic and genomic examination of the Castaneides species complex by intensive sampling of additional populations along Cumberland Plateau and Appalachian Valley and Ridge of Alabama and Tennessee, employing both mtDNA and RADseq species delimitation approaches to delineate cryptic diversity and boundaries in this region. Analyses of two mitochondrial loci (nd4 and cytb) identified two reciprocally monophyletic lineages, which are also supported by population clustering and phylogenetic analyses of SNPs, that identified two population clusters with no evidence of gene flow. Our genetic and genomic results support the recognition of two additional cryptic lineages in the Castaneides species complex. Ultimately, this information is critical in developing successful adaptive management strategies for this important and endemic component of Appalachian Highland biodiversity.
... Reported population declines (from low relative abundance and fewer occupied sites) in the 1970s-1990s in North Carolina and regionally, caused heightened awareness of conservation needs and threats to Green Salamanders and their habitats (Corser 2001). Given the conservation concerns, documented population declines, and pending range-wide status assessment for Green Salamanders, it is vital to have comparable, longterm monitoring data among states and within regions, which hierarchical modeling can provide. ...
Population estimates help detect trends over time and evaluate management responses; however, rare or cryptic animals can be difficult to detect, causing estimates to be lower than their true state. Animals can also change behavior and habitat use seasonally or due to local climatic factors, affecting survey results. Repeated surveys help account for imperfect detection and obtain more accurate population estimates by reducing the chance of failing to detect animals. In North Carolina, USA, during 2016 and 2017, we used N-mixture modeling, a repeated survey technique, to model abundance and detection of Green Salamanders (Aneides aeneus) and Hickory Nut Gorge Green Salamanders (A. caryaensis). We surveyed 57 rock outcrop sites with a history of species occurrence, three times per season (spring, summer, and fall; total n = 854). We examined effects of season and microclimate conditions on detection probability and effects of site characteristics on abundance. Modeling each year separately, season was the most influential variable to explain detection probability with highest detection in the fall (2016: 0.29, 2017:0.40), followed by spring (2016: 0.23, 2017: 0.26) and then summer (2016: 0.06, 2017: 0.19). Reproductive history, rock area, and aspect were the most important factors explaining variation in abundance. Sites with a history of reproduction, particularly those larger in size and more west facing, had a higher mean number of salamanders (2016: 8.43, 2017: 8.00) than non-nest sites (2016: 1.48, 2017: 1.41). For population trend monitoring of these species, we suggest managers use N-mixture models and surveying 31-60 sites three times each in the fall.
... specialist places it in habitats (vertical rock outcrops and surrounding forests) that are often destroyed or substantially altered during mining activities. Habitat loss is one of several potential causes for past declines in populations of Green Salamanders (Corser 2001). In addition, this species is rare across its range, occurring in isolated populations that are vulnerable to anthropogenic disturbance (Petranka 1998;Pauley and Watson 2001). ...
Surface mining practices associated with coal extraction significantly impact assemblages of amphibians in the Appalachian Mountains; however, the impacts of coal extraction on amphibian habitat associated with rock outcrops is poorly understood. We compared habitat at 45 rock outcrops scattered across the Virginia coalfields to examine if and how habitat features associated with the occupancy of Green Salamanders (Aneides aeneus) differ among undisturbed control sites, mined highwalls, and remnant outcrops remaining in small patches of undisturbed habitat on active and former surface mines. An analysis of similarity indicated that the habitat structure of highwalls was significantly different from that of natural outcrops. These habitats did not appear to support populations of Green Salamander, a finding in line with predictions about the impacts of coal extraction on plethodontid salamanders. However, remnant outcrops were not significantly different from natural outcrops with respect to both outcrop structure and surrounding vegetation, despite occurring in highly-fragmented edge habitats located in close proximity to mining activities. We found populations of the Green Salamander at more than 70% of the remnant outcrops, including at sites dominated by invasive vegetation and located within meters of surface extraction activities. Although more work is needed to ascertain the health and status of populations, our data indicate that Green Salamanders occur in small, isolated patches of habitat within a larger disturbed matrix more frequently than previously thought; thus, areas that have been mined may represent an overlooked reservoir of populations potentially crucial to the conservation of the species.
... A pesar de esta amplia distribución y diversidad, son numerosos los trabajos realizados en distintas regiones del planeta documentando regresiones en las poblaciones de anfibios (Campbell, 1999;Lips, 1999;Bosch y col., 2001;Corser, 2001;Parris, 2001;Carrier y Beebee, 2003;Lecis y Norris, 2003;Bell y col., 2004;Davidson, 2004;Lips y col., 2004, por citar unos ejemplos), además de un notable aumento en los índices de mortalidad, e incidencia de malformaciones en estas comunidades (Meteyer, 2000;Lanno, 2008;Peltzer y col., 2011 (Marques y col., 2009), en áreas con gran desarrollo de industrias químicas (Zhelev y col., 2006;Zhelev, 2007) y como así también, en sitios agrícolas (Cabagna y col., 2005;Barni y col., 2007;Attademo y col., 2011), ya que, al presentar un ciclo reproductivo estacional (primaveraverano), en coincidencia con muchos cultivos extensivos, permiten encontrarlos en estos sistemas agrícolas (Peltzer y col., 2006;Peltzer y Lajmanovich, 2007). ...
... For example, forest clearance and fragmentation can cause localized drying and regional rainfall shifts, enhancing fire risk and restraining the capacity of species to move in response to shifting bioclimatic conditions (Brook et al., 2008). A rapid population decline of the green salamander (Aneides aeneus) within a highly fragmented habitat in the southern Appalachians, USA has also been linked with an increase in temperatures since the early 1960s (Corser, 2001). Similar findings have also been reported for butterflies in the United States (McLaughlin et al., 2002) and in the Mediterranean (Stefanescu et al., 2004). ...
... There are several examples of this kind of effect. A rapid decrease in green salamander [Aneides aeneus (Cope and Packaed, 1881)] relative abundance in populations in the USA has been attributed to a synergism of high habitat fragmentation and increased variation in January temperatures since 1970 (Corser 2001). Similar effects of temperature and fragmentation were found for the bay checkerspot butterfly [Euphydras editha bayensis (Sternitzky, 1937)] in the USA (McLaughlin et al. 2002), the tiger moth Artica caja L., 1758 in Britain (Conrad et al. 2002) and Mediterranean butterflies (Stefanescu et al. 2004). ...
A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The literatures on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and climate change require synthesis and a conceptual framework to simplify thinking. We propose a framework that integrates how climate change affects spatial population dynamics and the effects of habitat fragmentation in terms of (1) habitat quality, quantity and distribution, (2) habitat connectivity, and the (3) dynamics of habitat itself. We use the framework to categorize existing autecological studies and investigate how each is affected by anthropogenic climate change. It is clear that a changing climate produces changes in the geographic distribution of climatic conditions, and the amount and quality of habitat. The most thorough published studies show how such changes impact metapopulation persistence, source-sink dynamics, changes in species' geographic range or community composition. Climate-related changes in movement behavior and quantity, quality and distribution of habitat have also produced empirical changes in habitat connectivity for some species. An under-explored area is how habitat dynamics that are driven by climatic processes will affect species that live in dynamic habitats. We end our discussion by suggesting ways to improve current attempts to integrate climate change, spatial population dynamics, and habitat fragmentation effects, and suggest distinct areas of study that might provide opportunities for more fully integrative work. This article is protected by copyright. All rights reserved.
... Nevertheless, since amphibian metapopulation dynamics appear to be common (Marsh and Trenham 2001), and successful dispersal is reduced in disturbed habitats (Gibbs 1998, deMaynadier andHunter 2000), plethodontid salamander populations in more highly fragmented southeruAppalachianlandscapes (Petranka et aI. 1993, Corser 2001, Highton 2001, Ford et aI., 2002, Green 2003) might be more prone to suffer declines than those in large protected reserves. ...
We tested two predictions associated with the hypothesis that certain populations of pond-breeding amphibians are structured into metapopulations using minimum relative abundance estimates of nesting four-toed salamanders (Hemidactylium scutatum Schlegel) from 11 different ponds in the Great Smoky Mountains National Park. Coefficients of variation (CV) for counts at individual ponds ranged from 0.25 to 1.26, and the overall mean CV at all 11 ponds was 0.34. Many pairs of ponds had negative correlations in abundance from 1999-2003, whereas others had various degrees of positive correlation (mean r = 0.29). Thus, nesting population size fluctuated semi-independently among the ponds from year to year, inferring the existence of inter-pond dispersal. The mean number of nesting females at a pond was negatively, but non-significantly, correlated (r = -0.27; P = 0.40; 10 d.f.) to the pond's isolation. Owing to physiological constraints on plethodontid salamander energetics, precipitation during the nesting season (February and March) appeared to play an important role (r = 0.78; P = 0.12; 4 d.f.) in the number of nesting females we observed. Unlike some other plethodontid salamander populations in more fragmented southern Appalachian forest ecosystems, this (meta)population within Great Smoky Mountains National Park does not appear to be declining.
... Specifically, plethodontid salamanders (1) are key components of detrital food webs in forest floor communities and top predators in primary and secondary stream ecosystems (Wyman 1998;Davic and Welsh 2004), (2) reside in high densities in many forested environments and provide an abundant food source for other predatory vertebrates (Petranka and Murray 2001;Davic and Welsh 2004), and (3) are indicators of environmental quality due to physiological adaptations, including moist, permeable skin, and species-specific temperature tolerances (Feder 1983;Wells 2007) that link them physiologically to changes in environmental conditions (Welsh and Droege 2001). Given that some plethodontid salamander species have experienced recent population declines (Corser 2001;Caruso and Lips 2013;Kroschel et al. 2014), it is crucial to evaluate if ranavirus may play a role in further declines of plethodontid salamanders (Gray and Miller 2013). ...
Emerging pathogens are a potential contributor to global amphibian declines. Ranaviruses, which infect ectothermic vertebrates and are common in aquatic environments, have been implicated in die-offs of at least 72 amphibian species worldwide. Most studies on the subject have focused on pool-breeding amphibians, and infection trends in other amphibian species assemblages have been understudied. Our primary study objective was to evaluate hypotheses explaining ranavirus prevalence within a lungless salamander assemblage (Family Plethodontidae) in the Great Smoky Mountains National Park, USA. We sampled 566 total plethodontid salamanders representing 14 species at five sites over a 6-year period (2007-2012). We identified ranavirus-positive individuals in 11 of the 14 (78.6%) sampled species, with salamanders in the genus Desmognathus having greatest infection prevalence. Overall, we found the greatest support for site elevation and sampling year determining infection prevalence. We detected the greatest number of infections in 2007 with 82.5% of sampled individuals testing positive for ranavirus, which we attribute to record drought during this year. Infection prevalence remained relatively high in low-elevation sites in 2008 and 2009. Neither body condition nor aquatic dependence was a significant predictor of ranavirus prevalence. Overall, our results indicate that life history differences among species play a minor role determining ranavirus prevalence compared to the larger effects of site elevation and yearly fluctuations (likely due to environmental stressors) during sampling years.
... Within the southern Appalachian Mountains the steep topography, high rainfall, erosion-resistant rock, and construction of roads have exposed masses of rock on the sides of mountains and gorges. Typically, most of these exposed rock faces are too dry to sustain populations of salamanders, although Green Salamanders (Aneides aeneus) prefer drier rock-faces than do other plethodontid salamanders (Corser, 2001). Exposed rock faces with a constant supply of water can provide suitable habitat for certain species of stream salamanders (Huheey and Brandon, 1973). ...
The importance of plethodontid salamanders in forested ecosystems has been recognized for decades, and studies aimed at quantifying salamander biomass and determining habitat requirements have become more common. However, there is a lack of knowledge on the use and contribution of vertical structures (e.g., wet rock faces) to total salamander biomass within a forested ecosystem. The purpose of our study was to characterize the population density, biomass, and habitat use of a wet rock face by a stream-salamander assemblage. We estimated the population density to be 14.69 salamanders m(-2) and the total biomass estimate to be 27.16 g m(-2), which is more than two times greater than any salamander biomass reported previously in the eastern United States. We also found significant habitat partitioning of the vertical gradient by the three species of salamanders in the assemblage. The stable microclimate and increased protection from other predators (e.g., mammals, snakes, and ground-foraging birds) provided by wet rock faces likely leads to the increased amount of biomass we found in this study. Although the salamanders are likely protected from most noncaudate predators, the spatial structuring in the assemblage still follows an intraguild predation gradient found in horizontal habitats.
... For example, forest clearance and fragmentation can cause localized drying and regional rainfall shifts, enhancing fire risk and restraining the capacity of species to move in response to shifting bioclimatic conditions (Brook et al., 2008). A rapid population decline of the green salamander (Aneides aeneus) within a highly fragmented habitat in the southern Appalachians, USA has also been linked with an increase in temperatures since the early 1960s (Corser, 2001). Similar findings have also been reported for butterflies in the United States (McLaughlin et al., 2002) and in the Mediterranean (Stefanescu et al., 2004). ...
Climate change and land‐use change are having substantial impacts on biodiversity world‐wide, but few studies have considered the impact of these factors together. If the combined effects of climate and land‐use change are greater than the effects of each threat individually, current conservation management strategies may be inefficient and/or ineffective. This is particularly important with respect to freshwater ecosystems because freshwater biodiversity has declined faster than either terrestrial or marine biodiversity over the last three decades.
This is the first study to model the independent and combined effects of climate change and land‐use change on freshwater macroinvertebrates and fish. Using a case study in south‐east Q ueensland, A ustralia, we built a B ayesian belief network populated with a combination of field data, simulations, existing models and expert judgment. Different land‐use and climate scenarios were used to make predictions on how the richness of freshwater macroinvertebrates and fish is likely to respond in future.
We discovered little change in richness averaged across the region, but identified important impacts and effects at finer scales. High nutrients and high runoff as a result of urbanization combined with high nutrients and high water temperature as a result of climate change and were the leading drivers of potential declines in macroinvertebrates and fish at fine scales.
Synthesis and applications . This is the first study to separate out the constituent drivers of impacts on biodiversity that result from climate change and land‐use change. Mitigation requires management actions that reduce in‐stream nutrients, slows terrestrial runoff and provides shade, to improve the resilience of biodiversity in streams. Encouragingly, the restoration of riparian habitats is identified as an important buffering tool that can mitigate the negative effects of climate change and land‐use change.
... One empirical study of butterflies in the Sierra Nevada of California showed that both habitat loss and climate change had likely contributed to declines in species richness (Forister et al. 2010). The rapid disappearance of the green salamander (Aneides aeneus) from the southern Appalachians of the US has been attributed to changes in temperature coupled with the salamander's limited ability to disperse in landscapes modified by logging, resort development, and dams (Corser 2001). ...
Ecosystems around the world are already threatened by land-use and land-cover change, extraction of natural resources, biological disturbances, and pollution. These environmental stressors have been the primary source of ecosystem degradation to date, and climate change is now exacerbating some of their effects. Ecosystems already under stress are likely to have more rapid and acute reactions to climate change; it is therefore useful to understand how multiple stresses will interact, especially as the magnitude of climate change increases. Understanding these interactions could be critically important in the design of climate adaptation strategies, especially because actions taken by other sectors (eg energy, agriculture, transportation) to address climate change may create new ecosystem stresses.
... Declines in amphibian populations at local, regional, and global scales (Blaustein et al. 1994;Houlahan et al. 2000;Corser 2001;Carrier and Beebee 2003) have recently focused attention of the scientific community on this group of vertebrates. Amphibians have long been used to examine the role of competition and predation on survival, community structure, and the evolution of life-history strategies. ...
Development of appropriate conservation plans relies on life-history information and how life-history traits vary across populations of a species. Such data are lacking for many amphibians, including the Canadian Toad (Bufo hemiophrys Cope, 1886). Here we use skeletochronology to estimate size at age, growth rates, age at maturity, and longevity of toads from nine populations along a latitudinal gradient in Alberta, Canada. Size of individual toads within each year class was highly variable, but age and size (measured as snout-to-urostyle length) were significantly related for almost all populations. The largest individuals were found in the southern-most population, while the smallest toads were found in three populations from the middle of the latitudinal range studied. Growth rates were highest in the southern-most population and lowest at the three populations with relatively small individuals. Maximum age was from 7 to 12 years for the populations sampled. The oldest individuals were found in populations in the middle of the latitudinal range sampled; toads in these populations were smaller than those in all other populations. Age at maturity was 1 year old for males and 2 years old for females in most populations. This study shows that some life-history traits exhibit significant variation between Canadian Toad populations, suggesting that effective conservation of this species will need to include population or area-specific management.
... jordani). Examples of excluded species included the green salamander (Aneides aeneus) that occurred regionally in small disjunct populations in rock crevice habitat (Hafer and Sweeny 1993;Corser 2001) not sampled in the aforementioned surveys and the southern red-backed salamander (P. serratus) that was distributed only in the western portion of the region (Barker 1997, Petranka 1998. ...
Using museum collection records and variables computed by digital terrain modeling in a geographic information system, we examined the relationship of elevation, aspect, and “cove” patch size to the presence or absence of 7 common woodland salamanders in mature cove hardwood and northern hardwood forests in the southern Appalachians of Georgia, North Carolina, and South Carolina. Overall, elevation, aspect and patch size were poor discriminators among salamander species presence or absence at collection sites. Increased elevation was an important variable explaining the presence of Ocoee salamanders (Desmognathus ocoee) and Jordan's salamanders (Plethodon jordani). In contrast, decreased elevation was an important variable explaining the presence of slimy salamanders (Plethodon glutinosus). Our study contrasts with recent research indicating that suitable habitat patch size is an important determinant of woodland salamander species richness and abundance at recently disturbed sites. In these mature stands, we believe that cove patch size as determined by modeling either was well above effect-level thresholds for influencing individual species presence or our modeling failed to reflect true collection site conditions.
... Terrestrial salamanders are considered indicators of environmental health (Welsh and Droege, 2001) and may be sensitive to environmental disturbances. Corser (2001) found that disjunct populations of the terrestrial Green Salamander, Aneides aeneus, had declined 98% in abundance since the 1970s. Richard Highton (unpubl. ...
Effective monitoring of population size is critically important for endemic species with specialized habitat requirements so that timely remedial steps can be taken when declines are detected. We initiated a monitoring study of the endemic plethodontid salamander, Plethodon punctatus, which is generally found in talus habitats over 1000 m in elevation in a narrow range on Shenandoah Mountain on the border of Virginia and West Virginia. We tested congruence of nighttime visual encounter surveys (VES) and mark-recapture estimates of population size. VES was a valid index of the abundances of P. punctatus in the two habitats we surveyed. Sites on the eastern and western sides of Shenandoah Mountain were surveyed, and both methods estimated that population size on the west was approximately twice as high as that on the east. Individuals of this species exhibited a high degree of site fidelity. Cover object searches for species in talus habitats are expected to be of limited value, and we conclude that nighttime visual encounter surveys are most effective for population size monitoring of P. punctatus and other species that live in talus.
... Preliminary surveys suggest, however, that A. aeneus may also be uncommon on areas of Pigeon Mountain where P. petraeus is absent (Jensen, pers. obs.), as it is in other parts of its range (Corser 2001). It is possible, then, that the low densities of A. aeneus on Pigeon Mountain are independent of the presence of P. petraeus. ...
Using previously preserved material, a minimal number of sacrificed specimens, unharmed live individuals, and field observations, we studied the life history and habitat of the Pigeon Mountain salamander (Plethodon petraeus). Individuals of this species are patchily distributed among various habitats including rock outcrops and cave entrances. They were most abundant relative to other species of salamanders where extensive outcrops were associated with cave openings. Females mature at a larger size (mininum of 65 mm SVL) than males (minimum of 56 mm) and grow to a greater maximum size (85 mm for females and 80 mm for males). The minimum age at maturity appears to be three years for males. Our data on testicular variation suggest that mating occurs during late winter and/or spring.
... They also show susceptibility to a variety of natural and anthroprogenic perturbations (see Welsh and Droege [2001] for a review). Amphibian surveys have been initiated for several purposes, including (1) to establish baseline data and techniques for long-term monitoring programs (Gibbons et al. 1997, Corn 2000, Dodd et al. 2000, Hyde and Simons 2001), (2) to compare historical to current species distributions (Fisher and Shaffer 1996, Shaffer et al. 1998, Corser 2001) and (3) to identify and target hot spots of amphibian diversity and abundance for protection (Welsh and Lind 1988). Two important sources of variation, spatial variation and variation in detection probabilities, constrain the inferences drawn from these types of surveys (Yoccoz et al. 2001, Pollock et al. 2002). ...
Recent, worldwide amphibian declines have highlighted a need for more extensive and rigorous monitoring programs to document species occurrence and detect population change. Abundance estimation methods, such as mark–recapture, are often ex-pensive and impractical for large-scale or long-term amphibian monitoring. We apply a new method to estimate proportion of area occupied using detection/nondetection data from a terrestrial salamander system in Great Smoky Mountains National Park. Estimated species-specific detection probabilities were all 1 and varied among seven species and four sampling methods. Time (i.e., sampling occasion) and four large-scale habitat characteristics (previous disturbance history, vegetation type, elevation, and stream presence) were im-portant covariates in estimates of both proportion of area occupied and detection probability. All sampling methods were consistent in their ability to identify important covariates for each salamander species. We believe proportion of area occupied represents a useful state variable for large-scale monitoring programs. However, our results emphasize the impor-tance of estimating detection and occupancy probabilities rather than using an unadjusted proportion of sites where species are observed where actual occupancy probabilities are confounded with detection probabilities. Estimated detection probabilities accommodate variations in sampling effort; thus comparisons of occupancy probabilities are possible among studies with different sampling protocols.
... For example, forest clearance and fragmentation can cause localized drying and regional rainfall shifts, enhancing fire risk and restraining the capacity of species to move in response to shifting bioclimatic conditions (Brook et al., 2008). A rapid population decline of the green salamander (Aneides aeneus) within a highly fragmented habitat in the southern Appalachians, USA has also been linked with an increase in temperatures since the early 1960s (Corser, 2001). Similar findings have also been reported for butterflies in the United States (McLaughlin et al., 2002) and in the Mediterranean (Stefanescu et al., 2004). ...
Climate change and habitat loss are both key threatening processes driving the global loss in biodiversity. Yet little is known about their synergistic effects on biological populations due to the complexity underlying both processes. If the combined effects of habitat loss and climate change are greater than the effects of each threat individually, current conservation management strategies may be inefficient and at worst ineffective. Therefore, there is a pressing need to identify whether interacting effects between climate change and habitat loss exist and, if so, quantify the magnitude of their impact. In this article, we present a meta-analysis of studies that quantify the effect of habitat loss on biological populations and examine whether the magnitude of these effects depends on current climatic conditions and historical rates of climate change. We examined 1319 papers on habitat loss and fragmentation, identified from the past 20 years, representing a range of taxa, landscapes, land-uses, geographic locations and climatic conditions. We find that current climate and climate change are important factors determining the negative effects of habitat loss on species density and/or diversity. The most important determinant of habitat loss and fragmentation effects, averaged across species and geographic regions, was current maximum temperature, with mean precipitation change over the last 100 years of secondary importance. Habitat loss and fragmentation effects were greatest in areas with high maximum temperatures. Conversely, they were lowest in areas where average rainfall has increased over time. To our knowledge, this is the first study to conduct a global terrestrial analysis of existing data to quantify and test for interacting effects between current climate, climatic change and habitat loss on biological populations. Understanding the synergistic effects between climate change and other threatening processes has critical implications for our ability to support and incorporate climate change adaptation measures into policy development and management response.
The long-term monitoring of wildlife populations provides critical data used to inform conservation policy and action. Within the UK, the Goose & Swan Monitoring Programme (GSMP) and affiliated schemes monitor the abundance (i.e. population size) and breeding success of native, migratory species of geese and swans through co-ordinated winter counts and age assessments at key sites. Typically, GSMP reports definitive annual estimates of the total population size based on the numbers of individuals counted, and the breeding success of the population based on the relative numbers of adults and juveniles (i.e. individuals born during the previous breeding season) in the surveyed population. However, to date there have been no attempts to estimate the uncertainty associated with these estimates of abundance or breeding success produced by GSMP.
A widely-used approach to quantifying uncertainty associated with an estimate is to calculate a confidence interval, which indicates the likely range in which the mean estimate would be found if the sampling exercise was repeated. More specifically, if the same population was surveyed on multiple occasions and the 95% confidence intervals were estimated for each occasion, the resulting confidence intervals would contain the true population parameter in approximately 95% of the cases. To date, the estimation of confidence intervals for GSMP data has proven difficult, as for many of the monitored populations only a single survey of each site can be undertaken each winter, and the deployment of additional survey effort to repeat the surveys (which could be used to estimate the variance between surveys) is not practical. Even where multiple surveys are currently undertaken, the use of a consistent approach to the estimation of confidence intervals would facilitate meaningful comparisons among different populations. Approaches that would allow the estimation of comparable confidence intervals for all of the populations would therefore be beneficial.
In this report, we compare two methods of estimating confidence intervals for the breeding success or abundance produced by GSMP. These two methods were (i) simple analytical expressions (based on binomial and Poisson distributions), and (ii) alternative approaches based on simulation (bootstrap resampling or Monte Carlo simulations). Both methods could be used for the data that have been routinely collected by GSMP and affiliated schemes. Comparison of the confidence intervals produced indicated broad similarity between the two methods, for juvenile proportion and abundance estimates. Indeed, the confidence intervals estimated by the two methods for the proportions of juveniles within populations were identical in 7 of the 12 populations considered, given the precision with which such estimates have been typically reported (i.e. a percentage given to one decimal place or a proportion given to three decimal places), with only minor deviations of ≤0.009 in the remaining 5 populations.
Similarly, for annual estimates of total abundance, in all populations we found close matches between the size of the confidence intervals derived by Poisson tests and simulation. The mean difference between the sizes of the 95% CI values produced by the two methods did not exceed 7 individuals for any of the populations considered.
As expected, smaller 95% confidence intervals for the proportion of juveniles within a population were found where greater numbers of birds were aged, indicating a trade-off between sampling effort and uncertainty. Moreover, samples containing higher proportions of juveniles had larger confidence intervals for a given total number of aged birds; hence, for populations with higher breeding success greater sample sizes would be required to achieve more precise confidence intervals. For abundance, the absolute size of the confidence interval increased with population size (i.e. higher population sizes have larger confidence intervals). However, when confidence intervals were expressed as a percentage of the population size, their size decreased as total abundance increased.
Based on the findings in our report, we make a series of recommendations for the future development of GSMP and affiliated monitoring schemes. In particular, we recommend the use of binomial and Poisson 95% confidence intervals for age assessment and abundance data, respectively. These analytical methods can be implemented rapidly and require little prior knowledge of statistics or programming to implement. Furthermore, we recommend that consideration should be given to the trade-off between sampling effort and the size of confidence intervals, based on the information presented in this report, in order to optimise the deployment of survey effort as part of GSMP.
Understanding movement patterns and their biotic and abiotic correlates is crucial to effectively manage and conserve salamander populations of concern. Because information on Green Salamander (Aneides aeneus) movement patterns is limited, we tested several biological hypotheses about factors affecting their movements on the basis of data from 69 salamanders fluorescently tracked during spring of 2015 and 2016 in the Bankhead National Forest, northern Alabama. We found Green Salamanders primarily in rock crevices but also observed use of trees. Green Salamanders traveled through leaf litter but did not use it as a daily refuge. There was a significant difference between salamander body temperatures in daily refugia and ambient temperatures, indicating that refugia effectively buffer the species from ambient conditions. Green Salamanders moved an average of 4.98 m (95% confidence interval [CI] = 3.88–6.08) per night. Total distance traveled overnight increased with increasing body size for males but decreased with increasing size for females. Individual wandering ratios were affected by body size, with larger salamanders moving in more linear paths than smaller individuals. During nightly monitoring, 23% of salamanders did not leave their starting refuge or returned to it after a night of movement. Net distance movements showed selection of crevices averaging 1.94 m (95% CI = 0.90–2.99) from starting refuges. Our short-term movement study suggests that Green Salamanders use multiple neighboring refuges, follow complex paths in moving between them, and exhibit philopatry to those refuges.
The Earth’s climate has warmed by a mean of 0.6 °C over the last 100 years. The observed change in environmental conditions has promoted the re-evaluation of longterm data sets. The studies demonstrate that there has been systematic change in the abundance and distribution of a broad range of species, and provide convincing evidence that recent climate warming has affected biological systems. In this introduction, numerous examples of adapted behaviour and shifting ranges of species related to recent climate change are provided. These observations are neither derived from computer models nor considered as predictions for potential future impacts, but document changes which are actually occurring in the biosphere. They provide ecological evidence that organisms are responding to the recent warming trend of the past three decades and thus represent the biological “fingerprints” of climatic change.
This benchmark volume documents in comprehensive detail a major environmental crisis: rapidly declining amphibian populations and the disturbing developmental problems that are increasingly prevalent within many amphibian species. Horror stories on this topic have been featured in the scientific and popular press over the past fifteen years, invariably asking what amphibian declines are telling us about the state of the environment. Are declines harbingers of devastated ecosystems or simply weird reflections of a peculiar amphibian world? This compendium-presenting new data, reviews of current literature, and comprehensive species accounts-reinforces what scientists have begun to suspect, that amphibians are a lens through which the state of the environment can be viewed more clearly. And, that the view is alarming and presages serious concerns for all life, including that of our own species. The first part of this work consists of more than fifty essays covering topics from the causes of declines to conservation, surveys and monitoring, and education. The second part consists of species accounts describing the life history and natural history of every known amphibian species in the United States.
Aim: Woodland salamanders (genus: Plethodon) declined synchronously across many protected areas in Eastern North America by the mid-1980s, but no cause was attributed to these declines. We hypothesized that the rapid, synchronous loss of several populations of many species was consistent with the invasive pathogen Batrachochytrium dendrobatidis (Bd), and we resurveyed historic sites to search for Bd in current populations. Location: Great Smoky Mountains National Park. Methods: We surveyed 35 sites 2-4 times between March and November 2009, quantified community composition and abundance of 72 populations of six species and three hybrids of Plethodon salamanders, and collected 665 skin swabs to detect Bd. Results: At 22 of the 35 sites, we were unable to find one or more species that were historically present. Plethodon glutinosus and P. teyahalee and their hybrids were less abundant than historically found, P. jordani x metcalfi and P. ventralis were more abundant and the remaining three species fluctuated but showed no net change. Yet, only one of the 665 salamanders was positive for Bd. Main conclusions: Declines were not associated with particular localities, but occurred in particular species. We conclude that over collecting, logging, and acid rain are unlikely to have caused these population declines, but we were unable to rule out disease or climate change as contributing factors. Population declines of Plethodon salamanders in the Park are substantial and have persisted for 30 years. Determining the cause and the extent of these declines is important for managing this area of global salamander biodiversity.
Global population and species-level amphibian declines are attributable to multiple environmental and biological factors including the disease chytridiomycosis caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd). In North America, chytridiomycosis-mediated declines may be severe, but the occurrence of Bd is also patchy. The Southern Appalachian Mountains are a global hotspot for salamander diversity, yet relatively few surveys have focused on the prevalence of Bd in salamanders. From 2008 to 2013, we collected 668 swabs from 603 individual amphibians (some were captured and swabbed twice) of 43 species (seven Anura and 36 Caudata) from the Southeastern Pied-mont and Southern Appalachian Mountains in western North Carolina and northeastern Tennessee. We used replicate PCR-assays and found that Bd was present but extremely uncommon (1.00%) in salamanders of the region and was not detected at all in the four anuran taxa sampled. We detected six Bd-positive salamanders, including five Spotted Salamanders (Ambystoma maculatum; 10% of individuals sampled) from Watauga County, North Carolina, and one Green Salamander (Aneides aeneus; 7.7% of individuals sampled) from Transylvania County, North Carolina. Collectively, our data suggest that Bd is very uncommon in this salamander hotspot. Thus, Bd may not be a cause of current and future declines in this region. These data serve as an important baseline for future studies of amphibian abundance, distribution, and assemblage structure in this region.
I review the primary literature to ascertain the status of amphibian monitoring efforts in the southeastern USA, a “hotspot” for biodiversity in North America. This effort revealed taxonomic, geographic and ecological disparities in studies of amphibian populations in this region. Of the species of anurans and caudates known to occur in the Southeast, 73.8 and 33.3 %, respectively, have been monitored continuously for at least 4 years. Anurans are generally shorter-lived than are caudates and, thus, have been studied for the equivalent of at least one population turnover more than have caudates. The percentage of species (of those occurring in a given state) monitored continuously for at least 4 years was lowest for Alabama and Mississippi and highest for Florida for both taxa. The vast majority of studies (69.6 %) were conducted on species that inhabit natural freshwater wetlands, in contrast to other aquatic and terrestrial habitats. Species considered threatened by the International Union for Conservation of Nature comprised only 7.7 % of 65 species that have been studied consistently. The majority of comparative studies of contemporary versus historical occurrences were potentially biased by the use of “presence-only” historical data and resurveys of short duration. Other issues, such as inadequate temporal and spatial scale and neglect of different sources of error, were common. Awareness of these data gaps and sampling and statistical issues may help facilitate informed decisions in setting future monitoring priorities, particularly with respect to species, habitats and locations that have been largely overlooked in past and ongoing studies.
The National Climate Assessment process gives us an opportunity to determine if the changes in ecosystems, biodiversity and ecosystem services that have been predicted to occur have actually come to pass. Where have we been right? Where have we been wrong? What can we learn from predictions that have not come to pass? An iterative process of prediction and observation will help to develop a comprehensive understanding of the complex changes in ecosystems, biodiversity and ecosystem services that are being driven by climate change.
The Seepage Salamander (Desmognathus aeneus) is a tiny, terrestrial plethodontid with a patchy distribution across the Blue Ridge, Coastal Plain, and Piedmont physiographic provinces of the Southeastern United States. The species is of conservation concern or protected in most states within its limited geographic range, and anecdotal reports of population declines or extirpation have prompted a recent petition for federal listing under the Endangered Species Act. To assess the current status of the Seepage Salamander, we conducted 136 surveys at 101 sites, including 46 historical collection localities. Our survey results provide rare good news in this era of declining amphibian populations: we confirmed the presence of Seepage Salamanders at 78% of the historical locations surveyed and discovered new populations at 35 additional localities. Several of these new sites were within 5 km of historical collection sites where the species was not found. Encounter rates (salamanders/person hour searching) were comparable to encounter rates reported by a previous researcher in 1971. Although this species appears to be common and secure over the majority of its range (i.e., the Blue Ridge physiographic province of Georgia and North Carolina), encounter rates were lower and they occupied fewer sites across the Piedmont and Coastal Plain of Alabama and western Georgia, suggesting conservation may be warranted within these regions.
Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984–86 and from 1993–95) to address the question of whether evidence exists for declines among terrestrial amphibians in northwestern California forests. The majority of amphibians, both species and relative numbers, in these forests are direct-developing salamanders of the family Plethodontidae. We examined amphibian richness and evenness, and the relative abundances of the four most common species of plethodontid salamanders. We examined evidence of differences between years in two ecological provinces (coastal and interior) and across young, mature, and late seral forests and with reference to a moisture gradient from xeric to hydric within late seral forests. We found evidence of declines in species richness across years on late seral mesic stands and in the coastal ecological province, but these differences appeared to be caused by differences in the detection of rarer species, rather than evidence of an overall pattern. We also found differences among specific years in numbers of individuals of the most abundant species, Ensatina eschscholtzii, but these differences also failed to reflect a consistent pattern of declines between the two decadal sample periods. Results showing differences in richness, evenness, and relative abundances along both the seral and moisture continua were consistent with previous research. Overall, we found no compelling evidence of a downward trend in terrestrial plethodontid salamanders. We believe that continued monitoring of terrestrial salamander populations is important to understanding mechanisms of population declines in amphibian species.
Growth and age at reproductive maturity are two life-history parameters that add an important temporal component to species conservation, yet such information is seldom available for plethodontid salamanders. We modeled growth and age at maturity for a northern West Virginia population of Green Salamanders, Aneides aeneus, using snout–vent length (SVL) growth intervals from a five-year mark-recapture study. Growth data were fit to the von Bertalanffy and logistic growth interval models and compared using the residual error mean square. The logistic model provided the best fit to the recapture data, indicating that Green Salamanders grow slowly for plethodontids and that it takes 7–8 yr to reach reproductive maturity. Our results revealed that Green Salamanders mature at a later age than most plethodontid species, indicating that the species might have greater generation time and longevity than previously suspected. Our data may offer insight into why the species is sensitive to population declines. Thus, we suggest that future research focus on Green Salamander longevity and generation time to provide a framework from which comparisons can be made across populations.
Amphibians are frequently characterized as having limited dispersal abilities, strong site fidelity and spatially disjunct breeding habitat. As such, pond-breeding species are often alleged to form metapopulations. Amphibian species worldwide appear to be suffering population level declines caused, at least in part, by the degradation and fragmentation of habitat and the intervening areas between habitat patches. If the simplification of amphibians occupying metapopulations is accurate, then a regionally based conservation strategy, informed by metapopulation theory, is a powerful tool to estimate the isolation and extinction risk of ponds or populations. However, to date no attempt to assess the class-wide generalization of amphibian populations as metapopulations has been made. We reviewed the literature on amphibians as metapopulations (53 journal articles or theses) and amphibian dispersal (166 journal articles or theses for 53 anuran species and 37 salamander species) to evaluate whether the conditions for metapopulation structure had been tested, whether pond isolation was based only on the assumption of limited dispersal, and whether amphibian dispersal was uniformly limited. We found that in the majority of cases (74%) the assumptions of the metapopulation paradigm were not tested. Breeding patch isolation via limited dispersal and/or strong site fidelity was the most frequently implicated or tested metapopulation condition, however we found strong evidence that amphibian dispersal is not as uniformly limited as is often thought. The frequency distribution of maximum movements for anurans and salamanders was well described by an inverse power law. This relationship predicts that distances beneath 11–13 and 8–9 km, respectively, are in a range that they may receive one emigrating individual. Populations isolated by distances approaching this range are perhaps more likely to exhibit metapopulation structure than less isolated populations. Those studies that covered larger areas also tended to report longer maximum movement distances – a pattern with implications for the design of mark-recapture studies. Caution should be exercised in the application of the metapopulation approach to amphibian population conservation. Some amphibian populations are structured as metapopulations – but not all.
Captive and wild frogs from North and Central America and Australia recently have died with epidermal infections by chytridiomycete fungi. We isolated a chytridiomycete into pure culture from a captive, blue poison dart frog that died at the National Zoological Park in Washington, D.C. Using this isolate, we photographed developmental stages on nutrient agar, examined zoospores with transmission electron microscopy, and inoculated test frogs. This inoperculate chytrid develops either monocentrically or colonially and has thread-like rhizoids that arise from single or multiple areas on the developing zoosporangium. The taxonomically important features of the kinetosomal region of the zoospore indicate that this chytrid is a member of the Chytridiales but differs from other chytrids studied with transmission electron microscopy. Its microtubule root, which begins at kinetosome triplets 9-1 and extends parallel to the kinetosome into the aggregation of ribosomes, is distinctive. Histologic examination of test frogs revealed that the pure culture infected the skin of test frogs, whereas the skin of control frogs remained free of infection. The fungus is described as Batrachochytrium dendrobatidis gen. et sp. nov.
the golden toad, is an endangered species endemic to Costa Rica. Every year from the early 1970s through 1987 golden toads have emerged from retreats to breed during April-June. The most recent known breeding episode occurred during April-May 1987; more than 1500 adults were observed at five breeding pools, but a maximum of 29 tadpoles metamorphosed from these sites. During April-June 1988-90, we found only 11 toads during surveys of the breeding habitat. To examine the species' apparent decline, we analyzed data on rainfall, water temperature, and pH of the breeding pools. Our baseline data on weather patterns and characteristics of the breeding habitat suggest that warmer water temperatures and less advective precipitation during dry season post-1987 may have produced adverse breeding conditions. The toads may be alive and hiding in retreats awaiting appropriate weather conditions. The apparent scarcity of toads may reflect a normal population re-sponse to an unpredictable environment. On the other hand, because other an-urans with different breeding specializations seem to be declining from the area as well, one wonders whether warmer temperatures and dry conditions could be responsible for real population declines. Because the habitat is protected and pristine, potential causes of anuran de-clines such as habitat destruction, introduced predators, and collecting seem unlikely. Measurements of pH of the breeding pools, cloud water, and precipi-tation do not suggest acid precipitation effects, although we cannot rule out the possibility of environmental degradation some time prior to our measurements. Long-term monitoring programs combined with carefully controlled field ex-periments are needed to address factors responsible for declining amphibians.
ABSTRACT—Identical observations, conducted 1-4 times per year for 15-20 years at two locations in the southern Appalachians, have,yielded ,quantitative ,data ,on populations ,of six ,species of salamanders.,Although ,the ,numbers ,have ,fluctuated ,for various reasons, there has been no trend in the numbers of any of the species. The "world-wide decline of amphibian,populations" has not occurred,in the two,localities studied. Recently, much attention has been given to a decline in many
Extinctions are normal biological phenomena. Both mass extinctions in geological time and local extinctions in ecological time are well documented, but rates of extinction have increased in recent years—especially in vertebrates, including amphibians—as illustrated by recent reports of their population declines and range reductions. We suggest that long-term population data are necessary for rigorously evaluating the significance of the amphibian declines. Due to the physiological constraints, relatively low mobility, and site fidelity of amphibians, we suggest that many amphibian populations may be unable to recolonize areas after local extinction.
Las extinciones son un fenómeno biológico normal. Extinciones en masa en una escala temporal geológica y extinciones locales en una escala temporal ecológica, están bien documentadas, pero en años recientes las tasas de exinción han incrementado, especialmente en vertebrados, incluyendo a los anfibios tal como ha sido ejemplificado en reportes recientes sobre la declinación de su población y la reducción de su área de distribución. Nosotros sugerimos que datos poblacionales a largo plozo son necesarios para evaluar rigurosamente la significancia de la declinación en anfibios. Nosotros sugerimos que muchas de las poblaciones de anfibios son incapaces de recolonizar áreas después de extinciones locales debido a las restricciones fisiológicas, la relativamente baja movilidad y la filopatría de los anfibios.
Epidermal changes caused by a chytridiomycete fungus (Chytridiomycota; Chytridiales) were found in sick and dead adult anurans
collected from montane rain forests in Queensland (Australia) and Panama during mass mortality events associated with significant
population declines. We also have found this new disease associated with morbidity and mortality in wild and captive anurans
from additional locations in Australia and Central America. This is the first report of parasitism of a vertebrate by a member
of the phylum Chytridiomycota. Experimental data support the conclusion that cutaneous chytridiomycosis is a fatal disease
of anurans, and we hypothesize that it is the proximate cause of these recent amphibian declines.
HABITAT destruction is the major cause of species extinctions13. Dominant species often are considered to be free of this threat because they are abundant in the undisturbed fragments that remain after destruction. Here we describe a model that explains multispecies coexistence in patchy habitats4 and which predicts that their abundance may be fleeting. Even moderate habitat destruction is predicted to cause time-delayed but deterministic extinction of the dominant competitor in remnant patches. Further species are predicted to become extinct, in order from the best to the poorest competitors, as habitat destruction increases. More-over, the more fragmented a habitat already is, the greater is the number of extinctions caused by added destruction. Because such extinctions occur generations after fragmentation, they represent a debta future ecological cost of current habitat destruction.
Natterjack toads Bufo calamita have declined sharply at heathland sites in Britain during the 20th century. A significant feature of these habitats is the predominance of oligotrophic and dystrophic ponds on substrates with low buffering capacities. Acid ponds at one site, Woolmer Forest, were classified into two groups: shallow pools dominated by Sphagnum and high concentrations of organic solutes, and larger bodies of water in which pH was primarily influenced by inorganic anions (especially SO4). Pond pHs responded transiently to episodes of very acid (pH < 4) rain, but acidity in the larger ponds was probably modulated mainly by mobilisation of sulphur accumulated in sedimentary peat over many decades. Rain was significantly acidified (on average about threefold) after passage through pine canopies, but this effect was not observed after percolation through birch foliage. Two large ponds previously used but deserted by natterjacks within the last 50 years were too acid (pH < 4.5) in the 1980s to support embryonic and larval development. Evidence from diatom, macrophyte, heavy metal and soot particle analyses of sediment cores from these ponds indicated that recent acidification has occurred as a consequence of atmospheric pollution. The pH of one acidified pond rose rapidly after removal of recent sedimentary peat. The implications of these observations for heathland conservation are discussed.
We present an analysis of the genetic structures of 22 species of salamanders, with regard to levels of gene flow among populations. We estimate the gene flow parameter, Nm (the product of the effective population number and rate of migration among populations) using two alternative methods described by Wright and Slatkin. For most species, these two methods give approximately congruent estimates of Nm; when estimates differ, the method of Wright produces values slightly larger than those derived by the method of Slatkin. We analyze these results in light of independently derived historical inferences of the fragmentation of populations. This analysis suggests that the Nm values calculated from protein polymorphisms may contain information more relevant to historical patterns of gene exchange than to the current population dynamics; moderately large values of Nm may be calculated for species containing populations known to be no longer exchanging genes. Application of a method for estimating the maximum possible rate of gene exchange among populations indicates that, for most species studied here, gene flow among populations probably is no greater than the mutation rate. We suggest that most plethodontid species cannot be viewed as units whose cohesion is maintained by continuing gene exchange. Furthermore, we suggest that phenotypic uniformity among populations is not easily explained by hypotheses of continual stabilizing selection and propose that future work concentrate upon clarification of the genetic and epigenetic factors conferring self-maintenance or autopoietic properties on living systems.
The populations of many amphibian species, in widely scattered habitats, appear to be in severe decline; other amphibians show no such declines. There is no known single cause for the declines, but their widespread distribution suggests involvement of global agents--increased UV-B radiation, for example. We addressed the hypothesis that differential sensitivity among species to UV radiation contributes to these population declines. We focused on species-specific differences in the abilities of eggs to repair UV radiation damage to DNA and differential hatching success of embryos exposed to solar radiation at natural oviposition sites. Quantitative comparisons of activities of a key UV-damage-specific repair enzyme, photolyase, among oocytes and eggs from 10 amphibian species were reproducibly characteristic for a given species but varied > 80-fold among the species. Levels of photolyase generally correlated with expected exposure of eggs to sunlight. Among the frog and toad species studied, the highest activity was shown by the Pacific treefrog (Hyla regilla), whose populations are not known to be in decline. The Western toad (Bufo boreas) and the Cascades frog (Rana cascadae), whose populations have declined markedly, showed significantly lower photolyase levels. In field experiments, the hatching success of embryos exposed to UV radiation was significantly greater in H. regilla than in R. cascadae and B. boreas. Moreover, in R. cascadae and B. boreas, hatching success was greater in regimes shielded from UV radiation compared with regimes that allowed UV radiation. These observations are thus consistent with the UV-sensitivity hypothesis.
We review recent research on the pathology, ecology, and biogeography of two emerging infectious wildlife diseases, chytridiomycosis and ranaviral disease, in the context of host-parasite population biology. We examine the role of these diseases in the global decline of amphibian populations and propose hypotheses for the origins and impact of these panzootics. Finally, we discuss emerging infectious diseases as a global threat to wildlife populations.
Reports of declining amphibian populations in many parts of the world are numerous, but supporting long-term census data are generally unavailable. Census data from 1979 to 1990 for three salamander species and one frog species at a breeding pond in South Carolina showed fluctuations of substantial magnitude in both the size of breeding populations and in recruitment of juveniles. Breeding population sizes exhibited no overall trend in three species and increased in the fourth. Recent droughts account satisfactorily for an increase in recruitment failures. These data illustrate that to distinguish between natural population fluctuations and declines with anthropogenic causes may require long-term studies.
We present an analysis of the genetic structures of 22 species of salamanders, with regard to levels of gene flow among populations. We estimate the gene flow parameter, Nm (the product of the effective population number and rate of migration among populations) using two alternative methods described by Wright and Slatkin. For most species, these two methods give approximately congruent estimates of Nm; when estimates differ, the method of Wright produces values slightly larger than those derived by the method of Slatkin. We analyze these results in light of independently derived historical inferences of the fragmentation of populations. This analysis suggests that the Nm values calculated from protein polymorphisms may contain information more relevant to historical patterns of gene exchange than to the current population dynamics; moderately large values of Nm may be calculated for species containing populations known to be no longer exchanging genes. Application of a method for estimating the maximum possible rate of gene exchange among populations indicates that, for most species studied here, gene flow among populations probably is no greater than the mutation rate. We suggest that most plethodontid species cannot be viewed as units whose cohesion is maintained by continuing gene exchange. Furthermore, we suggest that phenotypic uniformity among populations is not easily explained by hypotheses of continual stabilizing selection and propose that future work concentrate upon clarification of the genetic and epigenetic factors conferring self-maintenance or autopoietic properties on living systems.
A deme of Eleutherodactylus coqui was followed from 1979 to 1993 at El Verde, Puerto Rico, to determine seasonal and annual variation in numbers and activity patterns. All visible frogs and predatory spiders in a 50 x 2 m transect in the forest were counted for three consecutive nights semi-monthly for two years, then annually or biannually thereafter for a total of 255 evening counts. Ten all-night counts were made at five different times of the year to determine time of maximal activity during the night. Population size varied seasonally, with numbers increasing from June until December followed by a gradual decline until May. The number of adults varied from 1 to 29/100 m(2), whereas the number of juveniles varied from 0 to 221/100 m(2). The maximum single count of all frogs was 244. Counts of >100 juveniles occurred during October through January in the years 1979 to 1982, and in 1989. A marked drop in the numbers of frogs occurred in 1984; from 1979 to 1983, 3-50% of the counts yielded greater than or equal to 15 adults whereas the maximum count from 1984 until 1989 was 11 adults. The drop in numbers was correlated with an increased number of periods of days with less than or equal to 3 mm of rain. Over the period 1979 to 1989, the number of frogs observed was negatively correlated with the longest dry period during the previous year. Population size began to decrease in 1983 and never regained prior levels although numbers were increasing early in 1989 before Hurricane Hugo. Juveniles apparently cannot survive extensive drought, and extended dry periods may be lethal to adults who are inhibited from feeding because of potential desiccation. Predatory ctenid spider populations crashed two years following the decline of frog populations, then disappeared following the hurricane as did other arthropod predators. Rather than total monthly or annual rainfall, it is the distribution of the rain that is important to these subtropical wet forest species.
This study of Aneides aeneus consisted of three parts, (1) determination and mapping of the distribution and habitat choice as revealed by the author's observations, literature and correspondence, (2) an investigation of the life history and ecology carried out intensively on two colonies in the vicinity of Highlands, North Carolina, and less intensively at four other localities in Georgia, North Carolina and South Carolina, (3) preliminary water loss tolerance tests in the laboratory. The distribution of Aneides aeneus coincides with the Appalachian Plateau and Blue Ridge physiographic provinces of Fenneman, there being no known occurrence of the species in the Appalachian Valley. In eastern Kentucky, southwestern Virginia and adjacent portions of Tennessee Aneides aeneus is found to occur in an arboreal or arboreal-rock crevice habitat. Its habitat in all other portions of its range is chiefly rock crevices. The region of arboreal habitat coincides with the undifferentiated mixed mesophytic forest of Braun, while the rock habitat generally occurs in regions of segregated forests of the mixed mesophytic type. Two areas, designated as (1) Highlands Study Area, and (2) South Satulah Area, were visited throughout a complete annual cycle and part of a second breeding season (April 30, 1949 to June 25, 1950). Rock crevices within these two areas were numbered and mapped. Fifty-two individual Aneides were marked by toe clipping and observations were made on the salamander population and on associated fauna and flora. During June, 1950, records were kept on temperature and humidity of the two localities. Data obtained on the crevices containing Aneides indicate two general types of crevice, one used for breeding, another used in a transitory manner. The crevices are moist but not wet, and are always shaded for the major portion of the day. Average daily maximum and minimum temperatures within the crevice were 5.3⚬ F. and 1.3⚬ F. respectively lower than those prevailing in the general area (within eight feet of the crevice) during the period June 8 to June 21, 1950. Relative humidity for the same period averaged 99.1 maximum and 75.3 minimum, with extremes of 100 and 61. This climatic picture is characteristic of the Highlands Plateau and adjacent montane areas. The annual cycle of Aneides aeneus was found to consist of four periods: (1) the breeding period, (2) the dispersal and aggregation period, (3) the hibernation period, (4) the post-hibernation aggregation and dispersal period. The breeding period, late May to late September, includes mating, egg laying and hatching. Egg laying was noted to have occurred prior to June 6 and to have been completed by June 14, 1949 on both study areas. In 1950, it was not completed by June 21 on either study area. Three females required 23, 27.5 and 30 hours to complete laying. The eggs typically form a cluster hanging from the ceiling of the crevice by several cables, but in some cases they are laid as a flattened mass. The color of the freshly laid eggs is whitishyellow and they have an average diameter of 4.5 mm. for the 62 eggs measured. The number of eggs varied from 10 to 26 (mean 17) per clutch in 22 clutches examined. The eggs are guarded by the female at all times, and the guarding period varies, depending on the activity of the newly hatched young. Intraoval development required an average of 86 days and 19 hours from laying to hatching (extremes 84 to 91 days) for five clutches observed. Twenty-eight newly hatched young from both study areas varied in total length from 18.5 to 23.0 mm. (mean 20.0) and in body length from 12.5 to 15 mm. (mean 13.1). The dispersal and aggregation period occurs from late September to November. The young and adult females leave the breeding crevices in most cases during this period. The young apparently choose moss filled crevices and ledges in which they are well concealed. The adults begin to gather in the vicinity of deep interconnecting crevices during October. It is believed that Aneides aeneus spends the winter in this type crevice. This assembling of individuals is spoken of as the pre-hibernation aggregation. Hibernation occurs from November through late April. On the evidence that individuals were more concentrated in deep anastomosing crevices, it is concluded that crevices of this type serve for hibernation purposes. No individuals were found beneath the soil surface or in rotten logs. Post-hibernation aggregation and dispersal occurs in late April and early May when the salamanders reappear and congregate in the vicinity of the "hibernation" crevices. Dispersal to the outlying breeding cervices takes place early in June. Where crevices are utilized for both breeding and "hibernation," Aneides may be sedentary. Since the greater portion of the non-hibernation cycle is spent by the female in egg laying and guarding of the young, they are naturally more sedentary than the male and immature salamanders. Both sexes are more active at night. Males generally remain in or near the crevices where first found, but marked individuals were noted to move as much as 300 feet. Changes in the visible population on the two study areas are shown graphically in figure 6. Fluctuations in the number of visible individuals and in their distribution throughout the areas are the result of difference in the activity of the organism during the four periods of the annual cycle. The fall peak is due to an influx of individuals around the "hibernation" crevices and is considered as the best time for censusing an Aneides population. Collecting at four localities revealed a significant departure from an expected one to one sex ratio when individuals obtained were tested by the chi-square method. This is believed to be due to selective collecting based on the habits of the species. Ptethodon jordani metaventris was frequently seen to occupy the larger and more easily accessible crevices, but rarely to occur in the same crevice with Aneides aeneus. Preliminary experiments comparing the two species with respect to vital limits of water loss were carried out in the laboratory. These indicate that A. aeneus is more capable physiologically to live in the relatively dry crevice habitat than is P. j. melaventris. Morphologically, the former is better adapted for climbing and entering very narrow crevices in the rock. It would seem that Aneides aeneus is able to escape direct competition with P. j. melayentris and other salamanders by selection of its ecologically peripheral niche, and this may be a factor in its continued survival over a large range. The sedentary nature of the species, plus the selection of a more or less specialized habitat, points to a colonial existence over its range, probably with little or no gene flow between colonies. Therefore, a study of geographic variation with this species should be made. Because of the similarity of the mixed mesophytic forest, in which Aneides aeneus is found to lead a semi-arboreal existence, to the transcontinental broad-leafed Tertiary forest (the Arcto-Tertiary Flora of Chaney, Condit and Axelrod), and since two of the western Aneides derived from a former transcontinental migrant are arboreal, the hypothesis that the arboreal habitat is primary and the rock habitat is secondary has been suggested.
Previous studies showed that the Shenandoah salamander, Plethodon shenandoah, is confined to several dry talus slopes in the Blue Ridge Mountains of Virginia; it is competitively excluded by P. cinereus from moister areas of soil in forests. A 14-year census of the population densities of both species shows that a 28-day drought in 1970 did not affect the density of P cinereus, due to the buffering effect of its deep-soil habitat. However, P shenandoah suffered about 99% mortality during the drought. A population in one talus recovered to its pre-drought density in eight years. This was due to the patchy presence of soil in this talus, which prevented critical dehydration of a small fraction of the population. In another talus, which lacks patches of soil, the drought resulted in the extinction of the P. shenandoah population; no individuals have been found there over nine years since the drought. This demonstrates that interspecific competition acted as the density-dependent ultimate factor leading to extinction while a climatic perturbation acted as the density-independent proximate factor
Field and laboratory studies were conducted to determine the times of mating and egg deposition of Aneides aeneus in West Virginia. Spermatogenic wave studies indicated that mating occurs in the spring (late May and early June) and possibly fall (September or October). Follicle analysis and field observations indicated that eggs are deposited in June. Examination of follicles and observations of non-brooding females disclosed a biennial egg-laying cycle. Comparisons are made to more southern and higher elevation populations of A. aeneus.
The disappearance and return of plethodontid salamanders on clearcuts has been monitored since 1979 in the southern Blue Ridge Mountains at three sites near Highlands, North Carolina. Salamander abundance on 225 m ² plots located on clearcuts and in nearby forest was determined by nightly non‐destructive searches. Abundances on clearcut and forest plots at a given site were compared for each year in which sampling occurred. Numbers of salamanders on clearcut plots decreased to 30–50% of forested plots in the first year after logging and were almost zero by the second year. Decreases in standing crop and moisture content of leaf litter seem responsible for salamander disappearance. Salamanders returned to clearcuts 4–6 years after cutting, and their numbers increased rapidly. Linear regressions estimate that salamander numbers on clearcut plots will equal or exceed numbers on forested plots by 20–24 years after cutting. The pattern of salamander return to clearcuts appears closely correlated with the timing of litter layer reformation. All sex and age classes of the most common species, Plethodon jordani, disappear from clearcuts at equal rates, whereas the earliest colonizers are predominantly large adults. Plethodon oconaluftee, a desiccation‐resistant species, exists on regenerating clearcuts in disproportionately large numbers. Large adults of all species, including Plethodon oconaluftee, may be better able to withstand the drier, sparse litter cover of young, regenerating stands. Adults might move to clearcuts to avoid competition from smaller and immature salamanders restricted to mature forests with abundant, moist litter.
Portions of northern Maine provide an excellent existing field design for studying persistence of DDT in forest ecosystems. DDT was applied from aircraft at the rate of one pound per acre for control of the spruce budworm, Choristoneura fumiferana, in 1967, 64, 63, 61, 60 and 1958. Areas covered in the different programs varied from about I00,000 to 500,000 acres. While there was some overlap in treatments, sizable blocks remain which were treated only once in the years indicated above. Additional areas exist that have been treated two or three times, and there are also surrounding, ecologically similar areas that have no recorded spray history. Within this design, one can obtain within a single season or two samples of organisms or soils that provide data on DDT persistence up to nine years after a single treatment and accumulations of DDT residues following two or three successive treatments.
Previous research has shown that amphibian species have differential sensitivity to ultraviolet-B (UV-B) radiation. In some anuran species, ambient levels of UV-B cause mortality in embryonic stages and hatching success is significantly reduced. Projected increases in UV-B may affect an increasing number of species. The adverse effects of UV-B may eventually be manifested at the population level and may ultimately contribute to population declines. Using field experiments, we investigated the effects of ambient UV-B on salamander (Ambystoma gracile) embryos developing at natural oviposition sites. We show that the hatching success of eggs of A. gracile shielded from UV-B is significantly higher than those not shielded from UV-B. 27 refs., 1 fig.
One goal of conservation biologiy is to explain population declines. We present field survey data and experimental evidence that implicate introduced predators as a possible cause of decline in the California newt (Taricha torosa). In 1994 and 1995 we surveyed 10 streams in the Santa Monica Mountains of southern California for amphibians. These streams contained California newts when surveyed between 1981 and 1986. Of the 10 streams surveyed in 1994, three contained introduced mosquitofish (Gambusia affinis) and/or crayfish (Procambarus clarkii). These three streams contained no California newt eggs, larvae, or adults. The seven streams without introduced predators contained California newts. We conducted laboratory and field experiments to determine if California newt larvae and egg masses are susceptible to predation by mosquitofish and crayfish. Results from these experiments indicate that crayfish consume California newt egg masses and that both mosquitofish and crayfish consume larval newts. In 24-hour field experiments, no newt larvae survived in crayfish enclosures, and only 13% of the larvae survived with mosquitofish. Newt larvae are known to have antipredator adaptations for native predators. Apparently, these adaptations are not adequate for coexistence with introduced crayfish or mosquitofish. Heavy rains in 1995 removed introduced crayfish from one stream. We found newt egg masses, larvae, and adults in that stream the following spring. This same stream showed no evidence of California newts when crayfish were present in matched-date surveys in 1994. These experiments and surveys present evidence that predation by mosquitofish and crayfish may cuase localized decline of newts in mountain streams of southern California. Understanding the effects of nonnative species is an important step in preventing detrimental introductions in the future.
Centre for Applied Conservation Biology, Faculty of Forestry, University of British Columbia, #270-2357 Main Mall, Vancouver, British Columbia, V6T 1Z4, Canada, lthomas@unixg.ubc.ca
There has been much concern about widespread declines among amphibians, but efforts to determine the extent and magnitude of these declines have been hampered by scarcity of comparative inventory data. We resurveyed a transect of the Sierra Nevada mountains in western North America that was carefully studied in the early 1990s. Our comparisons show that at least five of the seven frog and toad species in the area have suffered serious declines. One species has disappeared from the area entirely and a second species, formerly the most abundant amphibian in the area, has dwindled to a few small remnant populations. These declines have occurred in a relatively undisturbed, protected area and show some of the same patterns noted in other reports of amphibian declines. Introduced predatory fish, possibly interacting with drought-induced loss of refuge habitats, have contributed to the decline of some species. However, the overall cause of these dramatic losses remains unknown.
Recent warming has caused changes in species distribution and abundance, but the extent of the effects is unclear. Here we investigate whether such changes in highland forests at Monteverde, Costa Rica, are related to the increase in air temperatures that followed a step-like warming of tropical oceans in 1976 (refs4, 5). Twenty of 50 species of anurans (frogs and toads) in a 30-km2 study area, including the locally endemic golden toad (Bufo periglenes), disappeared following synchronous population crashes in 1987 (refs 6-8). Our results indicate that these crashes probably belong to a constellation of demographic changes that have altered communities of birds, reptiles and amphibians in the area and are linked to recent warming. The changes are all associated with patterns of dry-season mist frequency, which is negatively correlated with sea surface temperatures in the equatorial Pacific and has declined dramatically since the mid-1970s. The biological and climatic patterns suggest that atmospheric warming has raised the average altitude at the base of the orographic cloud bank, as predicted by the lifting-cloud-base hypothesis,.
Spring peepers (Pseudacris crucifer) were analyzed by GC-ECD for 15 organochlorine pesticides of environmental significance. Only DDT, DDE, DDD, and dieldrin showed significant tissue accumulations in spring peepers. The area of collection had a history of extensive DDT application for mosquito control, but the practice of pesticide application was abandoned 26 years ago. Local extinctions of amphibians have been documented in the immediate area, and the long-term effects of organochlorine pesticide exposure are implicated as plausible causes of these extinctions.
Many of the recent, widespread declines and disappearances of amphibian populations have taken place in seemingly undisturbed, montane habitats. The question of whether the observed patterns differ from those expected from natural population dynamics is the subject of an ongoing controversy with important implications for conservation. We examined this issue for the Monteverde region of Costa Rica’s Cordillera de Tilarán, where a multi-species population crash in 1987 led to the disappearance of the endemic golden toad ( Bufo periglenes) and many other species. Focusing on long-term studies of other amphibian assemblages, we developed probabilistic null models for the number of disappearances. Tests of these models at Monteverde suggest that the patterns observed there are highly improbable in the context of normal demographic variability. Twenty species of frogs and toads (40% of the anuran fauna) were missing throughout our 1990–1994 surveys of a 30-km2 area. Not all organisms in this area had declined accordingly: the relative frequency of absences was much greater for anurans than for breeding birds. Nevertheless, anuran habitats, most of which are protected within the Monteverde Cloud Forest Preserve, seemed unchanged, and none of the breeding-bird species known to be sensitive to deforestation was missing. Thus, only factors other than direct, obvious human impacts can explain the amphibian declines. Consistent with our tests of null models, analyses of recent population trends do not support the hypothesis that the 1987 crash was an extreme fluctuation from which populations are recovering. Surviving species for which baseline data are available—stream-breeding glass frogs ( Hyalinobatrachium fleischmanni and Centrolenella prosoblepon) and a pond-breeding treefrog ( Hyla pseudopuma)—remained far less abundant than they were before the crash and showed no increase during 1990-1994. We documented an increase only for one terrestrial-breeding rain frog ( Eleutherodactylus diastema).
Pruebas de Modelos Nulos para Disminuciones de Anfibios en una Montaña Tropical
Muchas de las disminuciones y desapariciones recientes de poblaciones de anfibios en varias partes del mundo se han producido en hábitats que aparentemente no han sido alterados. La pregunta de si los patrones observados difieren de lo que es predicho por la dinámica natural de poblaciones es el tema de una controversia actual que tiene consecuencias importantes para la conservación. Se examinó esta pregunta para la región de Monteverde en la Cordillera de Tilarán, Costa Rica, donde un colapso de poblaciones en 1987 produjo la desaparición del endémico sapo dorado ( Bufo periglenes) y muchas otras especies. Centrándose en estudios a largo plazo sobre anfibios de otras regiones, se desarrollaron modelos nulos probabilísticos con respecto al número de desapariciones. Al probarse estos modelos para Monteverde se sugiere que los patrones observados son poco probables dentro de los parámetros normales de la variabilidad demográfica. Durante 1990-1994 en un área de 30-km2, veinte especies de ranas y sapos (el 40% de los anuros de la región) estuvieron ausentes. No todos los organismos del área disminuyeron de la misma forma: por ejemplo, la frecuencia relativa de especies ausentes fue mucho mayor para los anuros que para las aves que se reproducen en el área de estudio. Sin embargo, la mayoría de los hábitats de anuros están protegidos dentro de la Reserva Biológica Bosque Nuboso de Monteverde, y no parecía que habían cambiado. Además, ninguna de las especies de aves que son afectadas de manera negativa por la deforestación estuvo ausente. Por lo tanto, las disminuciones de anfibios sólo pueden ser explicadas por factores que no son los impactos obvios y directos causados por los seres humanos. De acuerdo con nuestras pruebas de modelos nulos, los análisis de tendencias recientes de abundancia no apoyan la hipótesis de que el colapso de 1987 fuera una fluctuación extrema de la cual las poblaciones están recuperándose. Las especies sobrevivientes de las que existen datos demográficos anteriores al colapso—ranas de vidrio ( Hyalinobatrachium fleischmanni y Centrolenella prosoblepon), que se reproducen en quebradas, y una rana arborícola ( Hyla pseudopuma) que pone huevos en lagunas y pozos—eran mucho menos abundantes durante 1990–1994 de lo que fueron antes de este evento y no se encontró evidencias de aumento. Se documentó un incremento solo en las poblaciones de Eleutherodactylus diastema, que se reproduce en hábitats terrestres.