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The Integration of climate change, spatial dynamics, and habitat fragmentation: a conceptual overview

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The Integration of climate change, spatial dynamics, and habitat fragmentation: a conceptual overview

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Abstract

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.

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... With the rapid advance of both, one of the most central questions in the contemporary research on biodiversity, conservation and ecology is how these two facets of global change jointly influence natural populations (Eigenbrod, Gonzalez, Dash, & Steyl, 2015;Holyoak & Heath, 2016;Mantyka-Pringle, Martin, & Rhodes, 2012;McGill, Dornelas, Gotelli, & Magurran, 2015;Oliver & Morecroft, 2014). ...
... However, as detailed long-term data on the dynamics of spatially structured metapopulations in fragmented landscapes are available for only a few systems, the exact mechanisms by which climate change modifies the effects of habitat fragmentation are not well understood (Holyoak & Heath, 2016;Oliver & Morecroft, 2014). ...
... With increasing habitat fragmentation and advancing climate change there is a need for understanding the interactions between the two, and the ways one facet of global change might influence that of the other (Holyoak & Heath, 2016;Oliver & Morecroft, 2014 ...
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Habitat fragmentation and climate change are both prominent manifestations of global change, but there is little knowledge on the specific mechanisms of how climate change may modify the effects of habitat fragmentation, e.g. by altering dynamics of spatially structured populations. The long‐term viability of metapopulations is dependent on independent dynamics of local populations, because it mitigates fluctuations in the size of the metapopulation as a whole. Metapopulation viability will be compromised if climate change increases spatial synchrony in weather conditions associated with population growth rates. We studied a recently reported increase in metapopulation synchrony of the Glanville fritillary butterfly (Melitaea cinxia) in the Finnish archipelago, to see if it could be explained by an increase in synchrony of weather conditions. For this, we used 23 years of butterfly survey data together with monthly weather records for the same period. We first examined the associations between population growth rates within different regions of the metapopulation and weather conditions during different life‐history stages of the butterfly. We then examined the association between the trends in the synchrony of the weather conditions and the synchrony of the butterfly metapopulation dynamics. We found that precipitation from spring to late summer are associated with the M. cinxia per capita growth rate, with early summer conditions being most important. We further found that the increase in metapopulation synchrony is paralleled by an increase in the synchrony of weather conditions. Alternative explanations for spatial synchrony, such as increased dispersal or trophic interactions with a specialist parasitoid, did not show paralleled trends and are not supported. The climate driven increase in M. cinxia metapopulation synchrony suggests that climate change can increase extinction risk of spatially structured populations living in fragmented landscapes by altering their dynamics. This article is protected by copyright. All rights reserved.
... Such variation may be explained by the varying region-specific niche characteristic, which is driven by factors extrinsic to the species, such as the spatial distribution of climatic conditions . Holyoak and Heath (2016) and Kupika et al. (2018) also suggested that temperature and rainfall display complex temporal variation changing from place to place across geographies and climate variables, particularly rainfall and temperature, generally influenced habitat quantity and quality. The GTDR of India is an intensively used landscape due to urban development and economically driven land use as suggested by Teeffelen et al. (2012). ...
... However, the proactive management of such areas might be one solution, if the new occurrence of a species of high conservation concern and/ or climatic risk can be predicted with high certainty (Trautmann, 2018). Holyoak and Heath (2016) hypothesised that climate change may impact the abundance and occupancy of a population directly and indirectly through change in habitat quality, quantity and distribution and habitat dynamics. Therefore, one of the conservation requirements of biodiversity could be the precise assessment of species ranges or suitable habitat availability and knowing the distribution limiting factors to mitigate their negative impact (Fourcade et al., 2014). ...
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Ecologically and economically important obligate scavengers like vultures are under threat of extinction in the old world. Several resident and migratory vulture sites and individuals are hosted by the Gangetic-Thar-Deccan region of India with varied landscapes. The landscape is under threat from anthropogenic activities and climate change impacting the habitat. Therefore, habitat suitability of vultures was analysed using species distribution model, MaxEnt, ensemble of global circulation models (CCSM4, HadGEM2AO and MIROC5), citizen science and expert collected data. Altogether, 51 models were developed and their robustness was assessed to be good for conservation purpose (AUC range 0.719–0.906). Predicted unsuitable and suitable area categories of all vultures, resident vultures and migratory vultures were identified for the present and future years (2050 and 2070) under moderate and extreme emission scenarios (RCP 4.5 and RCP 8.5). The short-term and long-term area suitability change varied between 1 and 3%. Area suitability differences were also noticed among larger (global) and smaller (local) geographical areas. The bioenvironmental parameters (land use, land cover and human footprint) played a major role in habitat determination in the current scenario. Bioclimatic factors, like precipitation parameters (precipitation seasonality bio 15 and annual precipitation bio12) and temperature parameters (isothermality bio 3 and temperature seasonality bio04), were the main model determining covariates for future prediction. An earlier hypothesis of higher suitability of forest and lower suitability of agriculture area tested in this study stood modified. Implications of the results are discussed, and conservation strategies are suggested with an advice of global strategy and local execution.
... Amphibian meta-populations in the PPR are ideal for studying biotic connectedness among prairiepothole wetlands because of their need for an intact mosaic of grassland and wetland habitats (Mushet et al. 2014;Holm 2020). Because amphibians are often dispersal-limited, habitat fragmentation poses a high risk to amphibian metapopulations and communities (Lehtinen et al. 1999;Funk et al. 2005;Belasen et al. 2019). ...
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Context Agricultural land-use conversion has fragmented prairie wetland habitats in the Prairie Pothole Region (PPR), an area with one of the most wetland dense regions in the world. This fragmentation can lead to negative consequences for wetland obligate organisms, heightening risk of local extinction and reducing evolutionary potential for populations to adapt to changing environments. Objectives This study models biotic connectivity of prairie-pothole wetlands using landscape genetic analyses of the northern leopard frog ( Rana pipiens ) to (1) identify population structure and (2) determine landscape factors driving genetic differentiation and possibly leading to population fragmentation. Methods Frogs from 22 sites in the James River and Lake Oahe river basins in North Dakota were genotyped using Best-RAD sequencing at 2868 bi-allelic single nucleotide polymorphisms (SNPs). Population structure was assessed using STRUCTURE, DAPC, and fineSTRUCTURE. Circuitscape was used to model resistance values for ten landscape variables that could affect habitat connectivity. Results STRUCTURE results suggested a panmictic population, but other more sensitive clustering methods identified six spatially organized clusters. Circuit theory-based landscape resistance analysis suggested land use, including cultivated crop agriculture, and topography were the primary influences on genetic differentiation. Conclusion While the R. pipiens populations appear to have high gene flow, we found a difference in the patterns of connectivity between the eastern portion of our study area which was dominated by cultivated crop agriculture, versus the western portion where topographic roughness played a greater role. This information can help identify amphibian dispersal corridors and prioritize lands for conservation or restoration.
... Animals were likely not able to move freely among habitat fragments under the influence of climate warming, or if they were prone to drought stress (or dehydration). Such affects may explain the significant interaction between human population change and temperature (on all vertebrate species) or precipitation (on birds) in causing local extinction or population decline of species [48]. ...
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Human-induced environmental and climate change are widely blamed for causing rapid global biodiversity loss, but direct estimation of the proportion of biodiversity lost at local or regional scales are still infrequent. This prevents us from quantifying the main and interactive effects of anthropogenic environmental and climate change on species loss. Here, we demonstrate that the estimated proportion of species loss of 252 key protected vertebrate species at a county level of China during the past half century was 27.2% for all taxa, 47.7% for mammals, 28.8% for amphibians and reptiles and 19.8% for birds. Both human population increase and species richness showed significant positive correlations with species loss of all taxa combined, mammals, birds, and amphibians and reptiles. Temperature increase was positively correlated with all-taxa and bird species loss. Precipitation increase was negatively correlated with species loss of birds. Human population change and species richness showed more significant interactions with the other correlates of species loss. High species richness regions had higher species loss under the drivers of human environmental and climate change than low-richness regions. Consequently, ongoing human environmental and climate changes are expected to perpetuate more negative effects on the survival of key vertebrate species, particularly in high-biodiversity regions.
... Degradation and destruction of natural forest ecosystems are primary causes of biodiversity loss, thus compromising not only species composition but also ecosystem function (Chen et al. 2016;Holyoak and Heath 2016;Pogson 2015;Tylianakis et al. 2008). In East Asia, many natural forests were destroyed by local residents due to economic development (Foley et al. 2005;Haddad et al. 2015;Wiederholt et al. 2015), thus affecting the pattern of plant-animal interactions in remnant fragmented forests (Cordeiro and Howe 2003;Markl et al. 2012;Tylianakis et al. 2008). ...
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Most endangered plant populations in a fragmented forest behave as unique source populations for that species, and are strongly dependent on frugivorous birds for seedling recruitment and persistence. In this study, we combined field data on the seed dispersal behaviour of birds and GIS information of patch attributes to estimate how frugivorous birds could affect the effective dispersal pattern of Chinese yew (Taxus chinensis) in a fragmented and disturbed forest. Nine bird species were observed to visit T. chinensis trees, with Urocissa erythrorhyncha, Zoothera dauma and Picus canus being the most common seed dispersers. After foraging, six disperser species exhibited different perching patterns. Three specialist species, P. canus, Turdus hortulorum and Z. dauma stayed in the source patch during observation, while three generalist species, U. erythrorhyncha, Hypsipetes mcclellandii and H. castanonotus, were observed to perch in bamboo patches and varied in their distance moved because of their relatively large body size. As a consequence of perching, dispersers contributed significantly to the seed bank, and indirectly affected seedling recruitment. Moreover, the recruitment of T. chinensis was also affected by patch attributes in a fragmented forest (distances to source patch, patch type, size). Our results highlight the ability of unique source population regeneration of T. chinensis in a fragmented forest, with high dependence on both frugivorous birds and patch attributes, which should be considered in future planning for forest management and conservation of Chinese yew.
... Climate change, human impacts or a combination of the two have been proposed to explain the massive extinction, with explanations commonly invoking hunting, habitat loss coinciding with expansion of human populations [2][3][4][5], and/or landscape modification by human-set fires [6]. However, in some cases megafauna disappeared before the arrival of humans [7,8], and in others, climate change probably drove extinctions by causing range shifts and/or habitat loss [2,[9][10][11][12][13][14]. Evidence from ancient DNA and the distribution of archaeological and palaeontological records highlights the combined impacts of climate and humans as precipitating extinctions [11,15,16]. ...
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Climate change and humans are proposed as the two key drivers of total extinction of many largemammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal- spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates ofwarming and range shifts of species aremuch faster than those fromthe Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period-and regionspecific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming.
... Climate change associated with suitable habitat fragmentation would present another conservation challenge for this species (Holyoak & Heath, 2016;Li, Clinton, et al., 2015). Current habitat connectivity in southwestern portion of Qinling Mountains is relatively low, and these areas are predicted to experience greatest loss by the 2050s due to climate change, thereby emphasizing the need for a regional conservation strategy for giant panda conservation to protect these areas, and con- An assessment of the impact of climate change on species is a critical initial step in implementing the adaptation planning process (Rowland et al., 2011). ...
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Climate change might pose an additional threat to the already vulnerable giant panda (Ailuropoda melanoleuca). Effective conservation efforts require projections of vulnerability of the giant panda in facing climate change and proactive strategies to reduce emerging climate-related threats. We used the maximum entropy model to assess the vulnerability of giant panda to climate change in the Qinling Mountains of China. The results of modeling included the following findings: (1) the area of suitable habitat for giant pandas was projected to decrease by 281 km2 from climate change by the 2050s; (2) the mean elevation of suitable habitat of giant panda was predicted to shift 30 m higher due to climate change over this period; (3) the network of nature reserves protect 61.73% of current suitable habitat for the species, and 59.23% of future suitable habitat; (4) current suitable habitat mainly located in Chenggu, Taibai, and Yangxian counties (with a total area of 987 km2) was predicted to be vulnerable. Assessing the vulnerability of giant panda provided adaptive strategies for conservation programs and national park construction. We proposed adaptation strategies to ameliorate the predicted impacts of climate change on giant panda, including establishing and adjusting reserves, establishing habitat corridors, improving adaptive capacity to climate change, and strengthening monitoring of giant panda.
... Human disturbance has recently caused a nearcontinuous loss of natural coastal habitats worldwide (Holyoak & Heath, 2016); these habitats ultimately form a patchy network of semi-natural environments comprised of only remnants of the formerly prevailing natural coastal wetlands (Ma et al., 2014). This habitat modification can lead to a need to change animal conservation techniques in the remnant natural coastal wetlands (Baudains & Lloyd, 2007). ...
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Exploring how suitable habitat and population size of Red-crowned crane Grus japonensis respond to long-term coastal reclamation plays an important role in species conservation and in related coastal management. Here, we combined field data for suitable habitats and wintering population size of G. japonensis with GIS-based information to elucidate the influence of long-term coastal reclamation on this species and related conservation efforts. During 1975-2013, the intensity and spatial extent of coastal reclamation exhibited a temporal change, increasing dramatically in 1975–2000 and lessening considerably in 2000–2013. Under the pressure of long-term coastal reclamation, the decline of suitable habitat of G. japonensis was affected by increasing levels of human disturbance and decreasing availability of natural habitat. Moreover, the wintering population size of G. japonensis exhibited a decreasing trend during 1975–2013 as a result of the decreasing availability of fish ponds, bare tidal flats and increasing spatial extent of residential areas and P. australis habitat, which were indirectly affected by long-term reclamation. Our results highlight the importance of considering the long-term effects of coastal reclamation on both populations and suitable habitat of G. japonensis, which should be considered in future plans for coastal management and conservation.
... The most dominant global threat to natural forests and their biodiversity is land-cover change, which has negative impacts on both species persistence and ecosystem functions (Fahrig 2003;Tylianakis et al. 2008;Pogson 2015;Holyoak and Heath 2016). In Asia, many natural forests have been transformed to farmlands by local residents, resulting in several natural patches of forest within highly human-disturbed habitats (Foley et al. 2005;Haddad et al. 2015). ...
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Background The most dominant global threat to natural forests and their biodiversity is land-cover change, which has negative impacts on both species persistence and ecosystem functions. Land-cover change could alter animal behaviour and disrupt seed dispersal mutualisms. However, its effects on the role of bird functional traits in seed dispersal are not well studied. Methods In the present study, we assessed the contributions of bird functional traits (behavioural traits: food habit, foraging pattern, foraging frequency, and habitat specialisation; morphological traits: weight, body length, wing length, and tail length) to both seed removal patterns and seed dispersal distances of an endangered and native tree species, Chinese yew (Taxus chinensis), in farmland, patchy habitat, and natural habitat, of southeast China. Results We found that the ability of T. chinensis trees to form seed dispersal mutualisms with local birds varied across the different disturbed habitats. As a consequence of these mutualisms, more seeds were removed by birds from the patchy habitat than from the other two habitats. The number of seeds removed increased with bird foraging frequency. Moreover, the dispersal distance from the three habitats differed, and the longest dispersal distances were observed at both the patchy habitat and the farmland site. Seed dispersal distance increased with bird tail and wing length. Conclusions Our results highlight the importance of bird functional traits in the seed dispersal patterns of endangered trees across disturbed forest habitats, which should be considered for tree conservation and management.
... Understanding population dynamics is a central goal in ecology (Andreo et al. 2009;Wang et al. 2013Wang et al. , 2016Xiao et al. 2016). The role of endogenous and exogenous factors in population dynamics of animals is well-studied (Previtali et al. 2009;Wang et al. 2009;Ernest et al. 2010;Yan et al. 2013;Selås 2016a, b), but it is often difficult to determine exactly which factor or set of factors regulate natural populations (Stenseth et al. 2003;Ratikainen et al. 2008;Holyoak and Heath 2016;Bastille-Rousseau et al. 2018). For granivorous species, seeds are an important resource that significantly influences population cycles of seedeating small mammals (Wolff 1996;Selonen et al. 2015). ...
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Chemical compounds in seeds exert negative and even lethal effects on seed-consuming animals. Tannin-degrading bacteria in the guts of small mammals have been associated with the ability to digest seeds high in tannins. At the population level, it is not known if tannins influence rodent species differently according to the composition of their gut microbiota. Here, we test the hypothesis that sympatric tree species with different tannins exert contrasting effects on population fluctuations of seed-eating rodents. We collected a 10-year dataset of seed crops and rodent population sizes and sequenced 16S rRNA of gut microbes. The abundance of Apodemus peninsulae was not correlated with seed crop of either high-tannin Quercus mongolica or low-tannin Corylus mandshurica, but positively correlated with their total seed crops. Abundance of Tamias sibiricus was negatively correlated with seed crop of Q. mongolica but positively correlated with C. mandshurica. Body masses of A. peninsulae and T. sibiricus decreased when given high-tannin food; however, only the survival of T. sibiricus was reduced. The abundance of microbial genus Lactobacillus exhibiting potential tannin-degrading activity was significantly higher in A. peninsulae than in T. sibiricus. Our results suggest that masting tree species with different tannin concentrations may differentially influence population fluctuations of seed predators hosting different gut microbial communities. Although the conclusion is based on just correlational analysis of a short time-series, seeds with different chemical composition may influence rodent populations differently. Future work should examine these questions further to understand the complex interactions among seeds, gut microbes, and animal populations.
... The species gained and lost may bring new challenges, such as the introduction of new pathogen and pest species (Cable et al. 2017). Further, these changes are occurring in the context of other human-caused stresses, such as habitat loss and pollution, which may exacerbate climate-related stresses (Holyoak and Heath 2016;Noyes et al. 2009). A summary of existing data, tools, and research on this topic in Georgia can further inform decisionmakers and can serve as a basis for further research. ...
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Climate change has far-reaching effects on human and ecological systems, requiring collaboration across sectors and disciplines to determine effective responses. To inform regional responses to climate change, decision-makers need credible and relevant information representing a wide swath of knowledge and perspectives. The southeastern U. S. State of Georgia is a valuable focal area for study because it contains multiple ecological zones that vary greatly in land use and economic activities, and it is vulnerable to diverse climate change impacts. We identified 40 important research questions that, if answered, could lay the groundwork for effective, science-based climate action in Georgia. Top research priorities were identified through a broad solicitation of candidate research questions (180 were received). A group of experts across sectors and disciplines gathered for a workshop to categorize, prioritize, and filter the candidate questions, identify missing topics, and rewrite questions. Participants then collectively chose the 40 most important questions. This cross-sectoral effort ensured the inclusion of a diversity of topics and questions (e.g., coastal hazards, agricultural production, ecosystem functioning, urban infrastructure, and human health) likely to be important to Georgia policy-makers, practitioners, and scientists. Several cross-cutting themes emerged, including the need for long-term data collection and consideration of at-risk Georgia citizens and communities. Workshop participants defined effective responses as those that take economic cost, environmental impacts, and social justice into consideration. Our research highlights the importance of collaborators across disciplines and sectors, and discussing challenges and opportunities that will require transdisciplinary solutions.
... The species gained and lost may bring new challenges, such as the introduction of new pathogen and pest species (Cable et al. 2017). Further, these changes are occurring in the context of other human-caused stresses, such as habitat loss and pollution, which may exacerbate climate-related stresses (Holyoak and Heath 2016;Noyes et al. 2009). A summary of existing data, tools, and research on this topic in Georgia can further inform decisionmakers and can serve as a basis for further research. ...
Article
Full-text available
Climate change has far-reaching effects on human and ecological systems, requiring collaboration across sectors and disciplines to determine effective responses. To inform regional responses to climate change, decision-makers need credible and relevant information representing a wide swath of knowledge and perspectives. The southeastern U. S. State of Georgia is a valuable focal area for study because it contains multiple ecological zones that vary greatly in land use and economic activities, and it is vulnerable to diverse climate change impacts. We identified 40 important research questions that, if answered, could lay the groundwork for effective, science-based climate action in Georgia. Top research priorities were identified through a broad solicitation of candidate research questions (180 were received). A group of experts across sectors and disciplines gathered for a workshop to categorize, prioritize, and filter the candidate questions, identify missing topics, and rewrite questions. Participants then collectively chose the 40 most important questions. This cross-sectoral effort ensured the inclusion of a diversity of topics and questions (e.g., coastal hazards, agricultural production, ecosystem functioning, urban infrastructure, and human health) likely to be important to Georgia policy-makers, practitioners, and scientists. Several cross-cutting themes emerged, including the need for long-term data collection and consideration of at-risk Georgia citizens and communities. Workshop participants defined effective responses as those that take economic cost, environmental impacts, and social justice into consideration. Our research highlights the importance of collaborators across disciplines and sectors, and discussing challenges and opportunities that will require transdisciplinary solutions.
... Research on animal movement behavior, in particular how landscape features affect dispersal, is essential for predicting, understanding, and managing the impacts of ongoing changes in climate and landscape structure on animal populations (Hanski, 2001;Holyoak & Heath, 2016;Knowlton & Graham, 2010;van Strien et al., 2014). ...
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Anthropogenic alterations to landscape structure and composition can have significant impacts on biodiversity, potentially leading to species extinctions. Population‐level impacts of landscape change are mediated by animal behaviors, in particular dispersal behavior. Little is known about the dispersal habits of rails (Rallidae) due to their cryptic behavior and tendency to occupy densely vegetated habitats. The effects of landscape structure on the movement behavior of waterbirds in general are poorly studied due to their reputation for having high dispersal abilities. We used a landscape genetic approach to test hypotheses of landscape effects on dispersal behavior of the Hawaiian gallinule (Gallinula galeata sandvicensis), an endangered subspecies endemic to the Hawaiian Islands. We created a suite of alternative resistance surfaces representing biologically plausible a priori hypotheses of how gallinules might navigate the landscape matrix and ranked these surfaces by their ability to explain observed patterns in genetic distance among 12 populations on the island of O`ahu. We modeled effective distance among wetland locations on all surfaces using both cumulative least‐cost‐path and resistance‐distance approaches and evaluated relative model performance using Mantel tests, a causal modeling approach, and the mixed‐model maximum‐likelihood population‐effects framework. Across all genetic markers, simulation methods, and model comparison metrics, surfaces that treated linear water features like streams, ditches, and canals as corridors for gallinule movement outperformed all other models. This is the first landscape genetic study on the movement behavior of any waterbird species to our knowledge. Our results indicate that lotic water features, including drainage infrastructure previously thought to be of minimal habitat value, contribute to habitat connectivity in this listed subspecies.
... Habitat fragmentation is one of the most important drivers of global changes in biodiversity (Fahrig 2003;Haddad et al. 2015;Holyoak & Heath 2016) due to habitat loss, edge effects and an increase in the degree of isolation of remnant patches (Tylianakis et al. 2008;Haddad et al. 2015). Given that small habitat patches cannot support as many individuals as natural habitats, fragmentation not only leads to the extinction of frugivores but also disrupts frugivore-plant interactions in patchy forests (Cordeiro & Howe 2003;Bregman et al. 2016;Farwig et al. 2017). ...
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Habitat fragmentation is one of the most important drivers of change in biodiversity globally. Seed dispersal by birds is crucial for tree regeneration in remnant patchy forests, yet how bird traits could affect seed dispersal pattern in patchy forests is still not understood. We studied to what extent bird traits affect seed‐removal networks and whether these traits affect seed deposition and seedling recruitment for three co‐fruiting tree species—Taxus chinensis, Cinnamomum bodinieri, and Machilus thunbergii—in a patchy forest. Seventeen, eight, and ten bird species were recorded foraging seeds of T. chinensis, M. thunbergii, and C. bodinieri, respectively. Frequency of bird visitation increased with tail length, wing length and body length. Furthermore, bird body length, bill length, body weight, and wing length were important in the strength of the seed removal network. After foraging, six bird species exhibited different microhabitat utilization and their perching frequency increased with bird weight and tarsus length. As a consequence, frequency of habitat use, bird length and tarsus length were important in determining the number of deposited seeds. For seedling recruitment, seedling number increased with bird tarsus length and weight, but decreased with wing length. Overall, our results showed that various bird traits not only affected seed removal, but also influenced the subsequent processes of seed deposition and seedling distribution in a patchy forest. It also highlighted the importance of large‐bodied birds for a seed removal network and for plant recruitment and points toward the prioritization of these birds for protection in remnant patchy forests. This article is protected by copyright. All rights reserved.
... The IPCC reported this concern with high confidence. Many species in Asia could face extinction due to the synergistic effects of climate change and habitat degradation (Holyoak and Heath 2016). There will be more threats to the ecological health of wetlands, mangroves, and coral reefs in Asia. ...
Chapter
Climate change is affecting global natural resources, including forests. It has also affected the Indian Himalayan forests by influencing ecosystem services derived from it. The majority of the Indian population depends directly or indirectly on these services, ultimately affecting Himalayan communities. The climate change impacts may alter the structure, function, and composition of the Himalayan forest and are expected to influence the region's biodiversity. The assessment suggests a more significant rise in temperature of the western parts compared to the eastern part of the Indian Himalayas. Climate change effects are manifested as species range shift, phenological changes, changes in growth patterns, host-parasite interactions, insect pest incidence, habitat adaptability, biogeochemical interactions, and plant-animal-resource interactions, and hydrological behavior, etc. This chapter focuses on the issues of climate change and its implications on the forest ecosystem of the Indian Himalayas. It also covers the key issues, research gaps, and future research needs for the region concerning climate change studies. The constructed state of knowledge about the climate change impacts may provide insight into the forest ecosystem of the region. It will help researchers and decision-makers to formulate and prioritize adaptation and mitigation-related research to reduce climate change effects in the present and future.
... Often, only single, static time-period measures are available to link up current conditions with the biological data; these measures lack the dynamism (daily to annual variability) that is key to our understanding, given that we are accelerating climate change and grossly modifying the landscape (Holyoak and Heath, 2016). For example, urbanization and forest management each impact biodiversity (Paillet et al., 2010;Dvořák et al., 2017), with interactions between land-use change and climate (Mair et al., 2018) as well as tree species diversity (Spake et al., 2016). ...
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Premise of the Study Fungal diversity (richness) trends at large scales are in urgent need of investigation, especially through novel situations that combine long‐term observational with environmental and remotely sensed open‐source data. Methods We modeled fungal richness, with collections‐based records of saprotrophic (decaying) and ectomycorrhizal (plant mutualistic) fungi, using an array of environmental variables across geographical gradients from northern to central Europe. Temporal differences in covariables granted insight into the impacts of the shorter‐ versus longer‐term environment on fungal richness. Results Fungal richness varied significantly across different land‐use types, with highest richness in forests and lowest in urban areas. Latitudinal trends supported a unimodal pattern in diversity across Europe. Temperature, both annual mean and range, was positively correlated with richness, indicating the importance of seasonality in increasing richness amounts. Precipitation seasonality notably affected saprotrophic fungal diversity (a unimodal relationship), as did daily precipitation of the collection day (negatively correlated). Ectomycorrhizal fungal richness differed from that of saprotrophs by being positively associated with tree species richness. Discussion Our results demonstrate that fungal richness is strongly correlated with land use and climate conditions, especially concerning seasonality, and that ongoing global change processes will affect fungal richness patterns at large scales.
... The expansion of organisms from one temperature zone of Earth to another is a spectacular example of adaptive evolution (review: Hoffmann, Parsons, 1997). Adaptive changes occur in numerous modern populations as a response to global ecosystem and climate changes (reviewed in Pauls et al., 2013;Jaeschke et al., 2014;Holyoak, Heath, 2016;De Meester et al., 2018). ...
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In this study, we tried to understand why the biota of northern regions is similar to that of southern mountain regions. Phylogeographic studies of several Arctic-alpine plants (Arabis alpina, Bistorta vivipara, Carex atrofusca, Gentiana sect. Cruciata, Koenigia islandica, Oxyria digyna, Ranunculus glacialis, Saxifraga oppositifolia, Sibbaldia procumbens, Trollius europaeus, Veronica alpina, Lagotis spp., and Pedicularis spp.), insects (Oeneis spp. and Arcynopteryx dichroa), and a mammal species (Ovibos moschatus) indicate that the respective groups emerged in the mountains of the temperate climatic zone and then migrated to the Arctic. As paleontological findings indicate, the mountains of the temperate and tropical zones provided habitats for the ancestors of several Salmonidae genera and at least some of the mammalian species common to the Eurasian mammoth steppe (Mammuthus primigenius, Coelodonta antiquitatis, Bos (Poëphagus) baikalensis, Alopex lagopus, and Panthera spelaea). A hypothesis is suggested to explain the crucial role of mountain regions in the evolution of northern forms. Additionally, colonization events by Arctic taxa in the mountains of temperate climatic zones have been demonstrated in a few studies.
... For example, when 12 open-pollinated families of Picea glauca Moench seedlings were exposed to high temperatures of 42 °C to 50 °C for 30 min., the stability of photosystem II, as determined by chlorophyll fluorescence, decreased as temperature is increased [8]. To overcome the effects of high temperature, plants also have evolved to adapt/acclimate and survive in stressful environmental situations [3,6,20]. It is important to identify these heat tolerant lines so that breeding programs can be used these plants to improve thermal tolerance of new releases [15]. ...
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Reed plants were grown in a controlled laboratory environment. The aim of study is explain the effect of heat stress to anatomical feature of vascular system in Phragmites australis. The results show that high temperature increasing the diameter and density of xylem vessels. However, high temperature decreases the density of xylem vessels. There are differences in development of vascular bundle at 25 °C. It is represented as optimum degree for growing. When the temperature increased to 35 °C and 45 °C, the diameter of the metaxilem vessels and the diameter of the phloem are decreased over time until 18 weeks to the lower diameter. The diameter and vascular distances are showed an increase in the thickness of cell walls with increased thermal stress. Sclerenchyma cells are increased in number with increased exposure to heat stress. A comprehensive study of the temperature effects on plant vascular tissues and water can help us to understand plant responses to climate change. Thus improving breeding programs for climate-resistant types.
... Likewise, the connectivity of habitat plays a key role in maintaining the population structure, gene flow and persistence of species with large distributions, and is also an important component of metapopulation and landscape ecology (Kool et al. 2013). In the past, many species had large continuous distributions but changing climate, habitat fragmentation, pressure from introduced predators (Greenville et al. 2017), urbanisation, land management practices and resource extraction practices have contributed to the reduced distributions, with many species now occupying habitat patches that are disjunct (Mills et al. 2004;Holyoak and Heath 2016). This fragmentation influences fundamental population processes including population dynamics, evolution and their compensatory mechanisms (Marrotte et al. 2017). ...
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Understanding the spatial structure of populations is important in developing effective management options for threatened species, and for managing habitat connectivity for metapopulation function, demographic and genetic heterogeneity. We used genetic information to investigate the structure of populations of the quokka, Setonix brachyurus, in south-west Western Australia. We hypothesized that movement between known populations would be relatively rare and result in significant genetic structuring. Genetic analyses from 412 adult individuals at 14 nuclear markers (microsatellite) from 33 sampling locations identified structure, diversity and spatial separation of quokkas across their mainland distribution and on two islands. We identified nine inferred (K = 9) populations of quokka that would be otherwise difficult to define with standard ecological techniques. The highest genetic diversity was evident in a large central population of quokka in the southern forest area and genetic diversity was lower at the peripheries of the distribution. The Rottnest Island population contained 70 % of the genetic diversity of the mainland populations but the genetic diversity of animals on Bald Island was markedly lower. Populations of quokka in the northern jarrah forest were the only ones to show evidence of recent or long-term population bottlenecking. Of particular interest was the recently identified population at the Muddy Lakes area (the only remaining locality on the Swan Coastal Plain), which was identified as being genetically associated with the southern forest population. Overall, spatial and population cluster analysis showed small insular populations in the northern jarrah forest area, but in the southern forests, there appears to be a large panmictic population.
... We find that increasing the nonlinearity of the hare and lynx growth did not improve the fit of the model, contrary to the general belief that neural networks can easily overfit. This strongly suggests that the residual variation is attributable to state variables that are not modelled in the present system, such as climatic variables (Holyoak & Heath, 2016), fluctuations in hunting pressures (Deng, 2018) or age structure (Stenseth et al., 2002), and that increasing the complexity of the functional relationship between the hare and lynx population alone is insufficient to explain those residual dynamics. If nothing else, our study demonstrates that there seems to be a limit to the amount of variation that can be explained with di-trophic interactions as it accounts for up to 40% of the variation in the dynamics of the system, no matter how complicated the driving functions are. ...
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Inferring the functional shape of ecological and evolutionary processes from time series data can be challenging because processes are often not describable with simple equations. The dynamical coupling between variables in time series further complicates the identification of equations through model selection as the inference of a given process is contingent on the accurate depiction of all other processes. We present a novel method neural ordinary differential equations (NODEs) for learning ecological and evolutionary processes from time series data by modelling dynamical systems as ordinary differential equations (ODEs) and dynamical functions with artificial neural networks (ANNs). Upon successful training the ANNs converge to functional shapes that best describe the biological processes underlying the dynamics observed in a way that is robust to mathematical misspecifications of the dynamical model. We demonstrate NODEs in a population dynamics context and show how they can be used to infer ecological interactions dynamical causation and equilibrium points. We tested NODEs by analysing well understood hare and lynx time series data which revealed that prey‐predator oscillations were mainly driven by the inter‐specific interaction as well as intra‐specific density‐dependence and characterised by a single equilibrium point at the center of the oscillation. Our approach is applicable to any system that can be modelled with differential equations and particularly suitable for linking ecological evolutionary and environmental dynamics where parametric approaches are too challenging to implement opening new avenues for theoretical and empirical investigations.
... The simultaneous pressures of climate change and habitat fragmentation may also result in worse than additive impacts on demography (Holyoak & Heath, 2016;Oliver et al., 2015). For example, if fragments have a reduced capacity to buffer changes in microclimate (Didham & Lawton, 1999;Ewers & Banks-Leite, 2013) or if fragment connectivity is climate dependent (Honnay et al., 2002), populations experiencing habitat fragmentation will fare worse under climate change. ...
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Deforestation often results in landscapes where remaining forest habitat is highly fragmented, with remnants of different sizes embedded in an often highly contrasting matrix. Local extinction of species from individual fragments is common, but the demographic mechanisms underlying these extinctions are poorly understood. It is often hypothesized that altered environmental conditions in fragments drive declines in reproduction, recruitment, or survivorship. The Amazon basin, in addition to experiencing continuing fragmentation, is experiencing climate change-related increases in the frequency and intensity of droughts and unusually wet periods. Whether plant populations in tropical forest fragments are particularly susceptible to extremes in precipitation remains unclear. Most studies of plants in fragments are relatively short (1–6 years), focus on a single life-history stage, and often do not compare to populations in continuous forest. Even fewer studies consider delayed effects of climate on demographic vital rates despite the importance of delayed effects in studies that consider them. Using a decade of demographic and climate data from an experimentally fragmented landscape in the Central Amazon, we assess the effects of climate on populations of an understory herb (Heliconia acuminata, Heliconiaceae). We used distributed lag nonlinear models to understand the delayed effects of climate (measured as standardized precipitation evapotranspiration index, SPEI) on survival, growth, and flowering. We detected delayed effects of climate up to 36 months. Extremes in SPEI in the previous year reduced survival, drought in the wet season 8–11 months prior to the February census increased growth, and drought two dry seasons prior increased flowering probability. Effects of extremes in precipitation on survival and growth were more pronounced in forest fragments compared to continuous forest. The complex delayed effects of climate and habitat fragmentation in our study point to the importance of long-term demography experiments in understanding the effects of anthropogenic change on plant populations.
... In the wild, the temperatures experienced during development may reliably indicate the future conditions encountered by adults (Nettle and Bateson, 2015). For instance, hot developmental conditions might be a cue to fragmented resource availability encountered at adulthood (Holyoak and Heath, 2016;Piessens et al., 2009). We therefore predicted that abnormally warm developmental conditions may signal poor and stressful environmental conditions that adult individuals may subsequently have to resist (by activating self-maintenance mechanisms: Günter et al., 2020a) or to escape (by enhancing flight performance: Battisti et al., 2006;Kuussaari et al., 2016). ...
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Within populations, phenotypic plasticity may allow adaptive phenotypic variation in response to selection generated by environmental heterogeneity. For instance, in multivoltine species, seasonal changes between and within generations may trigger morphological and physiological variation enhancing fitness under different environmental conditions. These seasonal changes may irreversibly affect adult phenotypes when experienced during development. Yet, the irreversible effects of developmental plasticity on adult morphology have rarely been linked to life-history traits even though they may affect different fitness components such as reproduction, mobility and self-maintenance. To address this issue, we raised larvae of Pieris napi butterflies under warm or cool conditions to subsequently compare adult performance in terms of reproduction performance (as assessed through fecundity), displacement capacity (as assessed through flight propensity and endurance) and self-maintenance (as assessed through the measurement of oxidative markers). As expected in ectotherms, individuals developed faster under warm conditions and were smaller than individuals developing under cool conditions. They also had more slender wings and showed a higher wing surface ratio. These morphological differences were associated with changes in the reproductive and flight performances of adults, as individuals developing under warm conditions laid fewer eggs and flew larger distances. Accordingly, the examination of their oxidative status suggested that individuals developing under warm conditions invested more strongly into self-maintenance than individuals developing under cool conditions (possibly at the expense of reproduction). Overall, our results indicate that developmental conditions have long-term consequences on several adult traits in butterflies. This plasticity likely acts on life history strategies for each generation to keep pace with seasonal variations and may facilitate acclimation processes in the context of climate change.
... The IPCC reported this concern with high confidence. Many species in Asia could face extinction due to the synergistic effects of climate change and habitat degradation (Holyoak and Heath 2016). There will be more threats to the ecological health of wetlands, mangroves, and coral reefs in Asia. ...
Chapter
Climate change poses threats to humans and brings the toughest challenges for economic development in the twenty-first century. The scientific communities warn the world leaders regarding the threats of climate change and its inevitable impacts on the physical and cultural environment. The Intergovernmental Panel on Climate Change (IPCC) reported global warming of 1.5 °C which is a matter of great concern for all the stakeholders around the world. The manifestation of recent climate change is increasing flooding events, shrinking of the cryosphere (mass loss from ice sheets/glaciers, reductions in snow cover), vegetation changes, and loss of biodiversity which are having adverse effects on available resources and aesthetic/cultural aspects of the Indian Himalayas (IH). Hence, it is imperative to study the impacts and responses of the mountainous region towards climate change for sustainable planning and adaptability. This chapter aims to review the scientific works on emerging trends in climate change, its impacts, and sustainability issues in the IH. The review work suggests the need for more research on innovative ideas for better adaptation and to combat the increasingly adverse impacts of climate change. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
... Habitat degradation can be seen as a change in states between one where the provision of resources leads to an ecosystem with high complexity and species diversity, to a state where the resources do not support communities of high diversity (Doak, 1995). The drivers of degradation include land clearing and sedimentation, eutrophication and pollution, and these are compounded by the broader-scale issues of changing global weather patterns caused by increasing levels of atmospheric CO 2 (Holyoak & Heath, 2016). Regardless of the causes of the change in habitat resources, habitat degradation is a gradual process that occurs on time scales relevant to both ecological (Alvarez-Filip et al., 2015;Wong & Candolin, 2015) and evolutionary processes (Munday et al., 2013;Santos et al., 2015). ...
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Habitat degradation not only disrupts habitat-forming species, but alters the sensory landscape within which most species must balance behavioural activities against predation risk. Rapidly developing a cautious behavioural phenotype, a condition known as neophobia, is advantageous when entering a novel risky habitat. Many aquatic organisms rely on damage-released conspecific cues (i.e. alarm cues) as an indicator of impending danger and use them to assess general risk and develop neophobia. This study tested whether settlement-stage damselfish associated with degraded coral reef habitats were able to use alarm cues as an indicator of risk and, in turn, develop a neophobic response at the end of their larval phase. Our results indicate that fish in live coral habitats that were exposed to alarm cues developed neophobia, and, in situ, were found to be more cautious, more closely associated with their coral shelters and survived four-times better than non-neophobic control fish. In contrast, fish that settled onto degraded coral habitats did not exhibit neophobia and consequently suffered much greater mortality on the reef, regardless of their history of exposure to alarm cues. Our results show that habitat degradation alters the efficacy of alarm cues with phenotypic and survival consequences for newly settled recruits.
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Dispersal and migration can be important drivers of species distributions. Because the paths followed by individuals of many species are curvilinear, spatial statistical models based on rectilinear coordinates systems would fail to predict population connectivity or the ecological consequences of migration or species invasions. I propose that we view migration/dispersal as if organisms were moving along curvilinear geometrical objects called smooth manifolds. In that view, the curvilinear pathways become the “shortest realised paths” arising from the necessity to minimise mortality risks and energy costs. One can then define curvilinear coordinate systems on such manifolds. I describe a procedure to incorporate manifolds and define appropriate coordinate systems, with focus on trajectories (1D manifolds), as parts of mechanistic ecological models. I show how a statistical method, known as “manifold learning”, enables one to define the manifold and the appropriate coordinate systems needed to calculate population connectivity or study the effects of migrations (e.g. in aquatic invertebrates, fish, insects and birds). This approach may help in the design of networks of protected areas, in studying the consequences of invasion, range expansions, or transfer of parasites/diseases. Overall, a geometrical view to animal movement gives a novel perspective to the understanding of the ecological role of dispersal and migration. This article is protected by copyright. All rights reserved.
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Deforestation often results in landscapes where remaining forest habitat is highly fragmented, with remnants of different sizes embedded in an often highly contrasting matrix. Local extinction of species from individual fragments is common, but the demographic mechanisms underlying these extinctions are poorly understood. It is often hypothesized that altered environmental conditions in fragments drive declines in reproduction, recruitment, or survivorship. The Amazon basin, in addition to experiencing continuing fragmentation, is warming and experiencing changes in precipitation leading to altered frequency and intensity of droughts and unusually wet periods. Whether plant populations in tropical forest fragments are particularly susceptible to extremes in precipitation remains unclear. Most studies of plants in fragments are relatively short (1-6 years), focus on a single life-history stage, and often do not compare to populations in continuous forest. Even fewer studies consider delayed effects of climate on demographic vital rates despite the importance of delayed effects in studies that consider them. Using a decade of demographic and climate data from an experimentally fragmented landscape in the Central Amazon, we assess the effects of climate on populations of an understory herb (Heliconia acuminata, Heliconiaceae). We used distributed lag non-linear models to understand the delayed effects of temperature and precipitation on survival, growth, and flowering. We detected delayed effects of climate up to 36 months. Drought two dry seasons prior to the February census decreased survival and increased flowering probability while drought in the wet season a year prior to the census decreased flowering probability and increased growth. The effects of extremes in precipitation on survival and growth were more pronounced in forest fragments compared to continuous forest. The complex delayed effects of climate and habitat fragmentation in our study point to the importance of long-term demography experiments in understanding the effects of anthropogenic change on plant populations.
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Our work aims to assess how butterfly communities in the Italian Maritime Alps changed over the past 40 years, in parallel with altitudinal shifts occurring in plant communities. In 2019, we sampled butterflies at 7 grassland sites, between 1300–1900 m, previously investigated in 2009 and 1978, by semi-quantitative linear transects. Fine-scale temperature and precipitation data elaborated by optimal interpolation techniques were used to quantify climate changes. The changes in the vegetation cover and main habitat alterations were assessed by inspection of aerial photographs (1978–2018/1978–2006–2015). The vegetation structure showed a marked decrease of grassland habitats and an increase of woods (1978–2009). Plant physiognomy has remained stable in recent years (2009–2019) with some local exceptions due to geomorphic disturbance. We observed butterfly ‘species substitution’ indicating a general loss in the more specialised and a general gain in more tolerant elements. We did not observe any decrease in species richness, but rather a change in guild compositions, with (i) an overall increased abundance in some widespread and common lowland species and (ii) the disappearance (or strong decrease) of some alpine (high elevation) species, so that ‘resilience’ could be just delusive. Changes in butterfly community composition were consistent with predicted impacts of local warming.
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For vertebrates, annual cycles are organized into a series of breeding and non-breeding periods that vary in duration and location but are inextricably linked biologically. Here, we show that our understanding of the fundamental ecology of four vertebrate classes has been limited by a severe breeding season research bias and that studies of individual and population-level responses to natural and anthropogenic change would benefit from a full annual cycle perspective. Recent emergence of new analytical and technological tools for studying individual and population-level animal movement could help reverse this bias. To improve understanding of species biology and reverse the population declines of many vertebrate species, a concerted effort to move beyond single season research is vital. © 2015 The Author(s).
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Abstract A challenge for conservation management is to understand how population and habitat dynamics interact to affect species persistence. In real landscapes, timing and duration of disturbances can vary, and species' responses to habitat changes will depend on how timing of dispersal and reproduction events relate to the landscape temporal structure. For instance, increasing disturbance frequency may promote extinction of species that are unable to appropriately time their reproduction in an ever-changing habitat and favor species that are able to track habitat changes. We developed a mathematical model to compare the effects of pulsed dispersal, initiated by shifts in habitat quality, with temporally continuous dispersal. We tested the effects of habitat (and population) turnover rates on metapopulation establishment, persistence, and long-term patch occupancy. Pulsed dispersal reduced patch occupancy and metapopulation longevity when habitat patches are relatively permanent. In such cases, demographic extinction was the primary form of local extinction. Conversely, when habitat patches are short-lived and new ones are frequently formed, pulsed dispersal promoted rapid colonization, increased occupancy, and prolonged metapopulation persistence. Our results show that species responsiveness to habitat disturbance is critical to metapopulation persistence, having profound implications for the species likely to persist in landscapes with altered disturbance regimes.
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Bachman’s Sparrow (Peucaea aestivalis), an endemic North American passerine, requires frequent (≤ 3 yr) prescribed fires to maintain preferred habitat conditions. Prescribed fires that coincide with the sparrow’s nesting season are increasingly used to manage sparrow habitat, but concerns exist regarding the effects that nesting-season fires may pose to this understory-dwelling species. Previous studies suggested that threats posed by fires might be lessened by reducing the extent of prescribed fires, thereby providing unburned areas close to the areas where fires eliminate ground-cover vegetation. To assess this hypothesis, we monitored color-marked male Bachman’s Sparrows on 2 sites where the extent of nesting-season fires differed 5-fold (>70 ha vs. <15 ha). Monthly survival for males did not differ between the large- and small-extent treatments, and survival rates exceeded 90% for all months except one during the second year of our study when fires were applied later in the season. Male densities also did not differ between treatments, but treatment-by-year interactions pointed to effects relating to the specific time that fires were applied. The distances separating observations of marked males before and after burns were smaller on small-extent treatments in the first year of study but larger on the small-extent treatments in the second year of study. Burn extents also had no consistent effect on postburn reproductive status. The largest extent we examined could have been too small to affect sparrow populations, but responses may also reflect sustainable metapopulation dynamics in a setting where a large sparrow population is maintained at a regional scale (> 100,000 ha) using frequent prescribed fire (≤ 2-yr return intervals). Additional research is needed regarding the effects that nesting-season fires may have on small, isolated populations as well as sites where much larger burn extents (> 100 ha) or longer burn intervals (>2 yr) are used.
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Weather and climate extremes have been varying and changing on many different time scales. In recent decades, heat waves have generally become more frequent across the United States, while cold waves have been decreasing. While this is in keeping with expectations in a warming climate, it turns out that decadal variations in the number of U.S. heat and cold waves do not correlate well with the observed U.S. warming during the last century. Annual peak flow data reveal that river flooding trends on the century scale do not show uniform changes across the country. While flood magnitudes in the Southwest have been decreasing, flood magnitudes in the Northeast and north-central United States have been increasing. Confounding the analysis of trends in river flooding is multiyear and even multidecadal variability likely caused by both large-scale atmospheric circulation changes and basin-scale “memory” in the form of soil moisture. Droughts also have long-term trends as well as multiyear and decadal variability. Instrumental data indicate that the Dust Bowl of the 1930s and the drought in the 1950s were the most significant twentieth-century droughts in the United States, while tree ring data indicate that the megadroughts over the twelfth century exceeded anything in the twentieth century in both spatial extent and duration. The state of knowledge of the factors that cause heat waves, cold waves, floods, and drought to change is fairly good with heat waves being the best understood.
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In contrast to well-studied Northern Hemisphere birds with spatially and temporally predictable seasonal migrations, waterbirds in desert biomes face major challenges in exploiting stochastic, rich, yet short-lived resource pulses in vast arid landscapes, leading to the evolution of nomadic behaviour. An extreme example is the banded stilt (Cladorhynchus leucocephalus), an opportunistic colonial breeder at remote inland salt lakes after infrequent rain events. Using satellite telemetry on 21 birds (tracked for a mean of 196.2 days), we reveal extensive, rapid and synchronized movement among individuals to and from salt lakes. Two birds left coastal refugia for the inland following rain, flying 1000-2000 km, while 12 others rapidly moved a mean of 684 km (range 357-1298 km) away from drying inland sites to the coast. Two individuals moved longitudinally across the continent, departing and arriving at the same points, yet travelling very different routes; one bird moving more than 2200 km in less than 2.5 days, the other more than 1500 km in 6 days. Our findings reveal movements nearly twice as long and rapid as recorded in other desert waterbirds. We reveal capability to rapidly detect and exploit ephemeral wetland resource pulses across the stochastic Australian desert.
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Migratory vertebrates adjust their movements in response to environmental change. Throughout their migrations, they gather information, integrate environmental and internal state data, and make decisions about the timing and orientation of migratory movements. Understanding this class of animal decision-making has both basic and applied interest because migratory animals face unique challenges adjusting to anthropogenic environmental changes worldwide. Evolved changes in decision mechanisms necessarily lag behind environmental changes because their evolution is driven by the consequences of resulting actions, and this raises the possibility of major mismatches between behaviour and environmental circumstances when the latter change faster than the pace of natural selection. Yet, migration-decision systems have the capacity for considerable flexibility at the phenotypic level. Distinguishing the evolution of fixed genetic changes from changes that can occur in individual phenotypes requires a better understanding of the mechanisms underlying organismal response. We reflect on such issues, hoping to engender new thinking about the special difficulties that seasonally migrating animals face in times of rapid environmental change. We focus on three key aspects: (1) We distinguish between variations in migratory timing forced upon migrants by overwhelming environmental changes and those that arise from individual “strategic” variation in decision-making. (2) We examine how the availability and reliability of information about environmental quality determine optimal cue choice and cue-response. (3) We highlight how adjustments of individual migration strategies can be made by changes in the decision-making machinery during development, dramatically increasing the rate at which migratory strategies can adjust to environmental change.
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Aim Species ranges have adapted during the Holocene to altering climate conditions, but it remains unclear if species will be able to keep pace with recent and future climate change. The goal of our study is to assess the influence of changing macroclimate, competition and habitat connectivity on the migration rates of 14 tree species. We also compare the projections of range shifts from species distribution models (SDMs) that incorporate realistic migration rates with classical models that assume no or unlimited migration. Location Europe. Methods We calibrated SDMs with species abundance data from 5768 forest plots from ICP Forest Level 1 in relation to climate, topography, soil and land-use data to predict current and future tree distributions. To predict future species ranges from these models, we applied three migration scenarios: no migration, unlimited migration and realistic migration. The migration rates for the SDMs incorporating realistic migration were estimated according to macroclimate, inter-specific competition and habitat connectivity from simulation experiments with a spatially explicit process model (TreeMig). From these relationships, we then developed a migration cost surface to constrain the predicted distributions of the SDMs. Results The distributions of early-successional species during the 21st century predicted by SDMs that incorporate realistic migration matched quite well with the unlimited migration assumption (mean migration rate over Europe for A1fi/GRAS climate and land-use change scenario 156.7 ± 79.1 m year−1 and for B1/SEDG 164.3 ± 84.2 m year−1). The predicted distributions of mid- to late-successional species matched better with the no migration assumption (A1fi/GRAS, 15.2 ± 24.5 m year−1 and B1/SEDG, 16.0 ± 25.6 m year−1). Inter-specific competition, which is higher under favourable growing conditions, reduced range shift velocity more than did adverse macroclimatic conditions (i.e. very cold or dry climate). Habitat fragmentation also led to considerable time lags in range shifts. Main conclusions Migration rates depend on species traits, competition, spatial habitat configuration and climatic conditions. As a result, re-adjustments of species ranges to climate and land-use change are complex and very individualistic, yet still quite predictable. Early-successional species track climate change almost instantaneously while mid- to late- successional species were predicted to migrate very slowly.
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Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive succes fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capit deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats as by the resources and other conditions at the site. -Author
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Evidence is accumulating that species' responses to climate changes are best predicted by modelling the interaction of physiological limits, biotic processes and the effects of dispersal-limitation. Using commercially harvested blacklip (Haliotis rubra) and greenlip abalone (H. laevigata) as case studies, we determine the relative importance of accounting for interactions among physiology, metapopulation dynamics and exploitation in predictions of range (geographical occupancy) and abundance (spatially explicit density) under various climate change scenarios. Traditional correlative ecological niche models (ENM) predict that climate change will benefit the commercial exploitation of abalone by promoting increased abundances without any reduction in range size. However, models that account simultaneously for demographic processes and physiological responses to climate-related factors result in future (and present) estimates of area of occupancy and abundance that differ from those generated by ENMs alone. Range expansion and population growth are unlikely for blacklip abalone because of important interactions between climate-dependent mortality and metapopulation processes; in contrast, greenlip abalone should increase in abundance despite a contraction in area of occupancy. The strongly non-linear relationship between abalone population size and area of occupancy has important ramifications for the use of ENM predictions that rely on metrics describing change in habitat area as proxies for extinction risk. These results show that predicting species' responses to climate change often require physiological information to understand climatic range determinants, and a metapopulation model that can make full use of this data to more realistically account for processes such as local extirpation, demographic rescue, source-sink dynamics and dispersal-limitation. This article is protected by copyright. All rights reserved.
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The effects of the experimental fragmentation of native eucalypt forest on the beetle community were tested, in a controlled, replicated, long-term experiment. In- cluded in our design were three fragment sizes, fragment edge and interior sites, and sites in the surrounding exotic pine plantation matrix. We followed 325 species through 28 sampling periods over seven years, including two years pre-fragmentation. We examined effects of fragmentation on four attributes of community structure: (1) species richness, (2) species composition, (3) relative abundance, and (4) the changes in occurrence of all species individually by the traits of rarity, degree of isolation (dispersal ability), and trophic group. We also considered how changes in these attributes altered community dynamics (turnover). We used both community-level and species-level responses to determine the relative importance of processes acting at the within-patch and between-patch scales. At the within-patch scale there were two findings. (1) There was no evidence of an increase in the extinction rate on fragments, as was hypothesized. Neither species richness nor the occurrence of rare species declined on fragments compared to continuous forest. (2) Edge effects altered species occurrences and abundances on fragments compared to continuous forest. There was evidence of two edge effects, with different penetration dis- tances. Species richness increased at fragment edges in response to a shallowly penetrating edge effect. Species relative abundance and composition changed on fragments in response to a deeply penetrating edge effect, which also caused increases in the occurrences of detritivores and fungivores. At the between-patch scale there were three findings. (1) There was no evidence of a reduction in the colonization rate of fragments. There was no reduction in species richness or in the occurrence of individual species with poor dispersal abilities on fragments com- pared to continuous forest. (2) The matrix between fragments altered between-patch pro- cesses by providing alternative habitat for some species. These species increased in oc- currence on fragments compared to continuous forest, supporting the predictions of recent metacommunity theory. However, the matrix did not act as a source of invading species. (3) Turnover was reduced in fragments compared to continuous forest. Thus, the effect of fragmentation was to stabilize community dynamics.
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Complex, human-dominated landscapes provide unique challenges to animals. In landscapes fragmented by human activity, species whose home ranges ordinarily consist of continuous habitat in pristine environments may be forced to forage among multiple smaller habitat patches embedded in an inhospitable environment. Furthermore, foragers often must decide whether to traverse a heterogeneous suite of landscape elements that differ in risk of predation or energetic costs. We modeled population consequences of foraging decisions for animals occupying patches embedded in a heterogeneous landscape. In our simulations, animals were allowed to use three different rules for moving between patches: a) optimal selection resulting from always choosing the least-cost path; b) random selection of a movement path; and c) probabilistic selection in which path choice was proportional to an animal's probability of survival while traversing the path. The resulting distribution of the population throughout the landscape was dependent on the movement rule used. Least-cost movement rules (a) produced landscapes that contained the highest average density of consumers per patch. However, optimal movement resulted in an all-or-none pattern of occupancy and a coupling of occupied patches into pairs that effectively reduced the population to a set of sub-populations. Random and probabilistic rules, (b and c), in relatively safe landscapes produced similar average densities and 100% occupancy of patches. However, as the level of risk associated with travel between patches increased, random movement resulted in an all-or-none occupancy pattern while occupied patches in probabilistic populations went extinct independently of the other patches. Our results demonstrate strong effects of inter-patch heterogeneity and movement decisions on population dynamics, and suggest that models investigating the persistence of species in complex landscapes should take into account the effects of the intervening landscape on behavioral decisions affecting animal movements between patches.
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Climate change vulnerability assessments are becoming mainstream decision support tools for conservation in the US, but they may be doing migratory species a disservice. R ecent predictions suggest that one in ten species could go extinct by the end of this century as a result of anthropogenic climate change 1 . In response, conservation professionals are scrambling to understand how a changing global climate will influence species persistence, and to develop risk management strategies— even as droughts, wildfires, floods, heat waves and violent storms play out around the world 2 . To proactively manage climate risks, the US government and collaborators have developed a National Fish, Wildlife and Plants Climate Adaptation Strategy 3 , to be released early in 2013, which outlines goals for conserving biodiversity in the context of a changing climate. Goals 4 and 5 of the draft plan call for improved support tools to facilitate conservation decisions, along with observation and monitoring to increase empirical knowledge about climate change impacts. Climate change vulnerability assessment (CCVA) frameworks are increasingly popular tools designed to advance understanding of species climate change vulnerability and guide adaptive management. A robust CCVA will examine climate exposure (for example, precipitation and temperature scenarios), climate sensitivity factors (such as population size, range and habitat association) and adaptive capacity (genetic bottlenecks or demographic parameters, for example) 4 , ultimately providing insight into potential causes of vulnerability. They can also be used to systematically develop testable hypotheses to generate new knowledge and identify appropriate conservation responses 5 . Standardized CCVA frameworks provide conservation planners with the ability to assess relative climate change vulnerability for many species; at least five frameworks are in use across the US 6–10 . We believe that the methods available now, although insightful for assessing the relative vulnerability of resident species, fall short and may even be misleading in predicting the vulnerability of migratory species to climate change. Because CCVAs are growing in popularity among North American conservation decision-makers, now is the time to address shortcomings that might otherwise misdirect conservation efforts. We reviewed how five multi-species frameworks used to assess climate change vulnerability in North America treat migratory species, and found their approaches to be varied and incomplete. So far, only three of the frameworks consider a species' migratory status 7,9,10 , and three consider factors on non-breeding grounds 8–10 . No assessment explicitly incorporates migratory connectivity— the specific links among breeding, wintering and migrating populations 11 — which would allow for the examination of climate exposure throughout the year for the same populations, or even acknowledges the value of full-life cycle assessments. Assessments that overlook much of the annual cycle for such a large proportion of species or fail to consider specific linkages between breeding and wintering grounds neglect key aspects of migratory species biology, and should not be considered adequate for guiding conservation policy and management. Conservation decision-makers are regularly faced with trade-offs between certainty and a compelling need for action, and sometimes decisions need to be made with incomplete information. It is nevertheless necessary to identify critical missing data where they exist, as this is the first step in filling such gaps to better inform the decision-making process. In this case, misdirected conservation for migratory species is a significant issue, as many
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Ecological responses to climate change may depend on complex patterns of variability in weather and local microclimate that overlay global increases in mean temperature. Here, we show that high-resolution temporal and spatial variability in temperature drives the dynamics of range expansion for an exemplar species, the butterfly Hesperia comma. Using fine-resolution (5 m) models of vegetation surface microclimate, we estimate the thermal suitability of 906 habitat patches at the species' range margin for 27 years. Population and metapopulation models that incorporate this dynamic microclimate surface improve predictions of observed annual changes to population density and patch occupancy dynamics during the species' range expansion from 1982 to 2009. Our findings reveal how fine-scale, short-term environmental variability drives rates and patterns of range expansion through spatially localised, intermittent episodes of expansion and contraction. Incorporating dynamic microclimates can thus improve models of species range shifts at spatial and temporal scales relevant to conservation interventions.
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Freshwater environments and their fishes are particularly vulnerable to climate change because the persistence and quality of aquatic habitat depend heavily on climatic and hydrologic regimes. In Australia, projections indicate that the rate and magnitude of climate change will vary across the continent. We review the likely effects of these changes on Australian freshwater fishes across geographic regions encompassing a diversity of habitats and climatic variability. Commonalities in the predicted implications of climate change on fish included habitat loss and fragmentation, surpassing of physiological tolerances and spread of alien species. Existing anthropogenic stressors in more developed regions are likely to compound these impacts because of the already reduced resilience of fish assemblages. Many Australian freshwater fish species are adapted to variable or unpredictable flow conditions and, in some cases, this evolutionary history may confer resistance or resilience to the impacts of climate change. However, the rate and magnitude of projected change will outpace the adaptive capacities of many species. Climate change therefore seriously threatens the persistence of many of Australia's freshwater fish species, especially of those with limited ranges or specific habitat requirements, or of those that are already occurring close to physiological tolerance limits. Human responses to climate change should be proactive and focus on maintaining population resilience through the protection of habitat, mitigation of current anthropogenic stressors, adequate planning and provisioning of environmental flows and the consideration of more interventionist options such as managed translocations. © 2011 CSIRO Open Access.
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A growing understanding of the ecology of seed dispersal has so far had little influence on conservation practice, while the needs of conservation practice have had little influence on seed dispersal research. Yet seed dispersal interacts decisively with the major drivers of biodiversity change in the 21st century: habitat fragmentation, overharvesting, biological invasions, and climate change. We synthesize current knowledge of the effects these drivers have on seed dispersal to identify research gaps and to show how this information can be used to improve conservation management. The drivers, either individually, or in combination, have changed the quantity, species composition, and spatial pattern of dispersed seeds in the majority of ecosystems worldwide, with inevitable consequences for species survival in a rapidly changing world. The natural history of seed dispersal is now well-understood in a range of landscapes worldwide. Only a few generalizations that have emerged are directly applicable to conservation man- agement, however, because they are frequently confounded by site-specific and species-specific varia- tion. Potentially synergistic interactions between disturbances are likely to exacerbate the negative impacts, but these are rarely investigated. We recommend that the conservation status of functionally unique dispersers be revised and that the conservation target for key seed dispersers should be a popu- lation size that maintains their ecological function, rather than merely the minimum viable population. Based on our analysis of conservation needs, seed dispersal research should be carried out at larger spa- tial scales in heterogenous landscapes, examining the simultaneous impacts of multiple drivers on com- munity-wide seed dispersal networks.
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Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive success fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capita deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats a...
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1. Many studies have investigated adaptation to climate change. However, the term ‘adaptation’ has been used ambiguously and sometimes included parts of both classic evolutionary processes and conservation planning measures (i.e. human-mediated adaptation). 2. To reduce ambiguity, we define three classes of evolutionary processes involved in adaptation – migrational, novel-variant and plasticity. Migrational adaptation describes the process of redistribution of standing genetic variation among populations. Novel-variant adaptation describes the increase in frequency of beneficial, new genetic variants. Plasticity adaptation refers to adaptive plastic responses of organisms to environmental stressors. Quite separately, human-mediated adaptation aims to maintain these evolutionary processes. 3. Whilst the role of scattered trees in migrational adaptation of fauna may have been neglected in the past, their capacity to assist migrational adaptation of trees has been previously documented. However, their role in novel-variant and plasticity adaptation is generally unrecognised, and warrants further attention. 4. Synthesis and applications. By defining different aspects of adaptation carefully, we show that scattered trees should not be cleared since they may facilitate gene flow across fragmented landscapes. However, they should be avoided as dominant seed sources since their stock may be of poor quality.
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Climate change is expected to alter the range and abundance of many species by influencing habitat qualities. For species living in fragmented populations, not only the quality of the present patches but also access to new habitat patches may be affected. Here, we show that colonization in a metacommunity can be directly influenced by weather changes, and that these observed weather changes are consistent with global climate change models. Using a long-term dataset from a rock pool metacommunity of the three species Daphnia magna, Daphnia longispina and Daphnia pulex with 507 monitored habitat patches, we correlated a four-fold increase in colonization rate with warmer, drier weather for the period from 1982 to 2006. The higher colonization rate after warm and dry summers led to an increase in metacommunity dynamics over time. A mechanistic explanation for the increased colonization rate is that the resting stages have a higher exposure to animal and wind dispersal in desiccated rock pools. Although colonization rates reacted in the same direction in all three species, there were significant species-specific effects that resulted in an overall change in the metacommunity composition. Increased local instability and colonization dynamics may even lead to higher global stability of the metacommunity. Thus, whereas climate change has been reported to cause a unidirectional change in species range for many other species, it changes the dynamics and composition of an entire community in this metacommunity, with winners and losers difficult to predict.
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Capsule The bioclimatic zone and habitat type within which birds winter are the most important determinants of population trends. Aims To investigate whether regional factors on wintering grounds, phenological mismatch, or habitat on breeding or wintering grounds show relationships with population changes of Afro-Palaearctic migrant birds. Methods We modelled breeding bird survey trends of 26 species of Afro-Palaearctic migrant birds that breed in Britain, and assessed the most important variables.We also investigated spatial variation in population trends within the UK. Results Bioclimatic zone and wintering habitat type were the most important determinants of population trend. After accounting for the effects of the other variables, species that spend the winter in southern Africa or the humid tropics of central and western Africa showed more negative population trends than those that winter in the arid zone. Species occupying open and woodland habitats declined and generalist species increased, on average. We also suggest that the effect of bioclimatic zone on population trends may be through constraints on the timing of migration. Conclusion Correlations between population change and both wintering area and winter habitat suggest regional changes in climate or land-use in the humid tropics are driving declines in many long-distance migrant species, possibly partly through migratory constraints.
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Over the next century, climate change will dramatically alter natural resource management. Specifically, historical refer-ence conditions may no longer serve as benchmarks for restoration, which may foster a "why bother?" attitude toward ecological restoration. We review the potential role for riparian restoration to prepare ecological systems for the threats posed by climate change. Riparian ecosystems are naturally resilient, provide linear habitat connectivity, link aquatic and terrestrial ecosystems, and create thermal refugia for wildlife: all characteristics that can contribute to ecological adaptation to climate change. Because riparian systems and the projected impacts of climate change are highly variable geographically, there is a pressing need to develop a place-based understanding of climate change threats to riparian ecosystems. Restoration practitioners should consider how they can modify practices to enhance the resilience of riparian ecosystems to climate change. Such modifications may include accelerating the restoration of private lands, participating in water management decisions, and putting the emerging field of restoration genetics into practice.
Chapter
On April 28, 1987, a biologist hiking through the remote Alakai swamp on the island of Kauai paused to listen to the sweet, flutelike song of a distant bird. He recognized the song as belonging to a Kauai ’o’o (Moho braccatus), a sleek chocolate-brown bird native to these woods. He was surely aware of the significance of this particular song, for during the past four years this particular ’o’o, the very last of its kind, had been the object of much attention among scientists and conservationists. But he could not have known that he was about to become the last person ever to hear it. The next time biologists visited the Alakai swamp, the ’o’o was gone, and yet another American species had moved from the realm of the living to the realm of the dead. The causes of the Kauai ’o’o’s extinction are reasonably clear, although the precise role each factor played in the species’ demise is debatable. Much of the bird’s forested habitat was destroyed for agriculture, leaving only a relatively few safe havens on steep slopes or in wet, inaccessible places. Most of these places, in turn, were eventually overrun with alien species, including feral pigs that destroyed the native vegetation, as well as plants and songbirds transported to Hawaii from around the world. The introduction of mosquitoes to Hawaii, which occurred in 1826 when the crew of a sailing ship dumped the mosquito larvae—infested dregs from their water barrels, created additional problems for Hawaii’s beleaguered birds. The mosquitoes became a vector for the spread of avian malaria and avian pox, diseases that were probably carried by the introduced birds. The native avifauna, presumably including the ’o’o, lacked resistance to these diseases, and many species quickly succumbed. Soon, only the forests at higher elevations, where cold temperatures kept the mosquitoes at bay, offered a disease free environment for the native birds. Eventually, however, the mosque toes reached even these forests, including the Alakai swamp, abetted by feral pig wallows, which created pools of stagnant water ideal for breeding mosquitoes. Thus a combination of factors, including habitat destruction, alien species, and diseases, contributed to the demise of the Kauai ’o’o.
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Understanding the ability of species to shift their geographic range is of considerable importance given the current period of rapid climate change. Furthermore, a greater understanding of the spatial population dynamics underlying range shifting is required to complement the advances made in climate niche modelling. A simulation model is developed which incorporates three key features that have been largely overlooked in studies of range shifting dynamics: the form of intraspecific competition, density dependent dispersal and the transient dynamics of habitat patches. The results show that the exact shape of the response depends critically on both local and patch dynamics. Species whose intraspecific competition is contest based are more vulnerable than those whose competition is scramble based. Contesters are especially sensitive when combined with density dependent dispersal. Species living in patches whose carrying capacity grows slowly are also susceptible to rapid shifts of environmental conditions. A complementary analytic approach further highlights the importance of intraspecific competition.
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This book had its origin when, about five years ago, an ecologist (MacArthur) and a taxonomist and zoogeographer (Wilson) began a dialogue about common interests in biogeography. The ideas and the language of the two specialties seemed initially so different as to cast doubt on the usefulness of the endeavor. But we had faith in the ultimate unity of population biology, and this book is the result. Now we both call ourselves biogeographers and are unable to see any real distinction between biogeography and ecology.
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The effects of the experimental fragmentation of native eucalypt forest on the beetle community were tested, in a controlled, replicated, long-term experiment. Included in our design were three fragment sizes, fragment edge and interior sites, and sites in the surrounding exotic pine plantation matrix. We followed 325 species through 28 sampling periods over seven years, including two years pre-fragmentation. We examined effects of fragmentation on four attributes of community structure: (1) species richness, (2) species composition, (3) relative abundance, and (4) the changes in occurrence of all species individually by the traits of rarity, degree of isolation (dispersal ability), and trophic group. We also considered how changes in these attributes altered community dynamics (turnover). We used both community-level and species-level responses to determine the relative importance of processes acting at the within-patch and between-patch scales. At the within-patch scale there were two findings. (1) There was no evidence of an increase in the extinction rate on fragments, as was hypothesized. Neither species richness nor the occurrence of rare species declined on fragments compared to continuous forest. (2) Edge effects altered species occurrences and abundances on fragments compared to continuous forest. There was evidence of two edge effects, with different penetration distances. Species richness increased at fragment edges in response to a shallowly penetrating edge effect. Species relative abundance and composition changed on fragments in response to a deeply penetrating edge effect, which also caused increases in the occurrences of detritivores and fungivores. At the between-patch scale there were three findings. (1) There was no evidence of a reduction in the colonization rate of fragments. There was no reduction in species richness or in the occurrence of individual species with poor dispersal abilities on fragments compared to continuous forest. (2) The matrix between fragments altered between-patch processes by providing alternative habitat for some species. These species increased in occurrence on fragments compared to continuous forest, supporting the predictions of recent metacommunity theory. However, the matrix did not act as a source of invading species. (3) Turnover was reduced in fragments compared to continuous forest. Thus, the effect of fragmentation was to stabilize community dynamics.
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We attempt to quantify the relationship between migration and latitude in the avifauna of eastern North America. Progressing northward up the east side of the continent, the proportion of breeding species that moves south for the winter increases steadily, from 12% at 25°N (southern Florida) to 87% at 80°N (Ellesmere Island), a mean increase of 1.4% for every degree of latitude. Conversely, the proportion of wintering species that moves north for the summer decreases with latitude, from 52% at 25°N to none at 70°N, a mean decrease of 1.1% for every degree of latitude. These relationships hold despite the fact that 24% of all species breeding in eastern North America leave the area completely in fall to winter south of 25°N, mostly in Central and South America (including the Caribbean Islands). These trends are similar to those in western Europe, but at any given latitude an average of 17% more breeding species leave for the winter in eastern North America, and 10% more wintering species leave for the summer. This difference is attributed to climate, in that at any given latitude temperatures are cooler in eastern North America than in Europe. We argue that relationships between migration and latitude exist because latitude is a good surrogate measure of factors likely to more directly influence migration, such as climate and daylength, which in turn control the amplitude of seasonal changes in food supplies.
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1. In western Europe, the number of bird species present in summer remains fairly constant at 187-229 between latitudes 35 and 65 degrees N, decreases to 156 by 70 degrees N, and then markedly to 26 and 24 on islands at 75 and 80 degrees N. The number present in winter decreases steadily with latitude from 211 at 35 degrees N to four at 80 degrees N, reflecting the greater withdrawal of species from northern latitudes in winter. 2. The proportion of summer visitors in the local avifauna in summer also increases with latitude from 29% of breeding species at 35 degrees N to 83% of breeding species at 80 degrees N. Conversely, the proportion of winter visitors in the local avifauna in winter decreases with latitude, from 36% of wintering species at 35 degrees N to 8% of wintering species (mostly seabirds) at 70 degrees N to none at 80 degrees N. 3. At most latitudes in the range 35-70 degrees N, while some species leave for the winter, a smaller number of other species move in, mostly from further north. About 23% of breeding species leave western Europe totally in autumn to winter elsewhere, most in Africa south of the Sahara but others in southern Asia and elsewhere. Conversely, 3% of wintering species leave western Europe totally in spring to breed elsewhere, some to the north-west in Iceland-Greenland-Canada and others to the north-east in northern Siberia.
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Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they sup-port remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia – a rela-tively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit – as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Che-lonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized frame-work for assessing the vulnerability of ecosystems to abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contri-bution to this framework.
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Dispersal is difficult to quantify and often treated as purely stochastic and extrinsically controlled. Consequently, there remains uncertainty about how individual traits mediate dispersal and its ecological effects. Addressing this uncertainty is crucial for distinguishing neutral versus non-neutral drivers of community assembly. Neutral theory assumes that dispersal is stochastic and equivalent among species. This assumption can be rejected on principle, but common research approaches tacitly support the 'neutral dispersal' assumption. Theory and empirical evidence that dispersal traits are under selection should be broadly integrated in community-level research, stimulating greater scrutiny of this assumption. A tighter empirical connection between the ecological and evolutionary forces that shape dispersal will enable richer understanding of this fundamental process and its role in community assembly.
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Several models have been suggested to explain variation in parasite richness among populations. Most of these models are based on epidemiological factors (population size, number of host species), biological factors (patch quality, interspecific competition) and the spatial and temporal structure of the host metapopulation. We studied the parasites of 137 rock pool populations of the planktonic crustacean Daphnia magna to determine the factors that account for total parasite richness, richness of endoparasites and epibionts, and the presence/absence patterns of individual parasite species. The rock pools of 86 of these populations have been studied since 1982, and it is known how long these pools have been continuously inhabited by Daphnia. By far the best predictor of total parasite richness was host population age, which explained ∼50% of the variance. While endoparasite richness increased linearly with age over 16 yr, epibiont richness saturated ∼3 yr after pool colonization, which may be explained by the higher dispersal rate of epibionts. After we corrected for host population age, endoparasite richness was positively correlated with the water volume of the rock pool (an estimator for host population size), and epibiont richness was correlated with water conductivity. Pools with lower water conductivity (less influenced by the brackish water of the Baltic Sea) had more epibiont species. The local network size of the host metapopulation (local pool density and number of pools per island) hardly influenced parasite richness. There was also no strong indication of spatial effects (isolation by distance and island effects) on the parasite community. The factors that were correlated with species richness were, however, not the same as those related to the presence of single parasite species. At least for certain epibionts, it appears that presence/absence patterns were influenced by interspecific competition. In conclusion, our analysis shows that predictions derived from epidemiological and temporal models, but not from spatial models, can explain parasite richness patterns, despite apparent conflicting patterns found for individual parasite species. Our analysis extends the scope of these models, which were previously supported mainly with helminths, to bacteria and protozoa.
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Trapping records of the Canadian lynx show a strongly marked 10-year cycle. The logarithms of the numbers trapped are analysed as if they were a random process of autoregressive type. Such a process appears to fit the data reasonably well. The significance of this for the explanation and prediction of the cycle is discussed. The results will be used in a later paper to consider how far meteorological phenomena influence the lynx population and may be responsible for the observed synchronization of the cycle over the whole of Canada.
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Biologists are nearly unanimous in their belief that humanity is in the process of extirpating a significant portion of the earth's spe­ cies. The ways in which we are doing so reflect the magnitude and scale of human enterprise. Everything from highway construction to cattle ranch­ ing to leaky bait buckets has been implicated in the demise or endan­ germent of particular species. Ac­ cording to Wilson (1992), most of these activities fall into four major categories, which he terms "the mind­ less horsemen of the environmental apocalypse": overexploitation, habi­ tat destruction, the introduction of non-native (alien) species, and the spread of diseases carried by alien species. To these categories may be added a fifth, pollution, although it can also be considered a form of habitat destruction. Surprisingly, there have been reIa­ tively few analyses of the extent to which each of these factors-much less the more specific deeds encomDavid S. Wilcove is a senior ecologist at the Environmental Defense Fund, Wash­ ington, DC 20009. David Rothstein re­ ceived his J.D. in 1997 from Northeastern
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The distribution and extinction patterns within a northern metapopulation of the pool frog (Rana lessonae) were analyzed with reference to metapopulation theory. Occupied ponds were permanent and differed from unoccupied ones in terms of higher water temperature during May-June and a closer proximity to neighboring pool-frog lo- calities. but local climate was not spatially autocorrelated. Two types of population ex- tinctions occurred (average rate = 2% per population and year): (I) deterministic extinctions due to succession or draining of pool-frog ponds, and (2) extinctions of populations whose isolation had increased to a critical degree because of Type 1 extinctions of neighboring populations. increasing their susceptibility to predation and combined demographiden- vironmental stochasticity. The Type 2 extinctions were spatially correlated to a moderate degree, which may reflect the great impact of environmental stochasticity in the system. The results confirm and emphasize the importance of interpopulation proximity and con- nectivity for metapopulation persistence.
Article
ABSTRACT Benthic marine organisms are characterized by a bipartite life history in which populations of sedentary adults are connected by oceanic transport of planktonic propagules. In contrast with the terrestrial case, where ‘long distance dispersal’ (LDD) has traditionally been viewed as a process involving rare events, this creates the possibility for large numbers of offspring to travel far relative to the spatial scale of adult populations. As a result, the concept of LDD must be examined carefully when applied in a marine context. Any measure of LDD requires reference to an explicit ‘local’ scale, often defined in terms of adult population demography, habitat patchiness, or the average dispersal distance. Terms such as ‘open’ and ‘closed’ are relative, and should be used with caution, especially when compared across different taxa and systems. We use recently synthesized data on marine propagule dispersal potential and the spread of marine invasive species to draw inferences about average and maximum effective dispersal distances for marine taxa. Foremost, our results indicate that dispersal occurs at a wide range of scales in marine communities. The nonrandom distribution of these scales among community members has implications for marine community dynamics, and for the implementation of marine conservation efforts. Second, in agreement with theoretical results, our data illustrate that average and extreme dispersal scales do not necessarily covary. This further confounds simple classifications of ‘short’ and ‘long’ dispersers, because different ecological processes (e.g. range expansion vs. population replenishment) depend on different aspects of the dispersal pattern (e.g. extremes vs. average). Our findings argue for a more rigorous quantitative view of scale in the study of marine dispersal processes, where relative terms such as ‘short’ and ‘long’, ‘open’ and ‘closed’, ‘retained’ and ‘exported’ are defined only in conjunction with explicit definitions of the scale and process of interest. This shift in perspective represents an important step towards unifying theoretical and empirical studies of dispersal processes in marine and terrestrial systems.
Article
Spatially explicit simulation models provide a powerful method for modelling landscape and population changes at large spatial scales and may prove useful as a management tool for mobile animal populations. As an example of this approach, the authors present a model designed to elucidate the effects of landscape-level variation in habitat dispersion on the size and extinction probability of avian populations in a region managed for timber production. In the model, habitat suitability and availability within the landscape change annually as a function of timber harvest and management strategies. The model incorporates life history characteristics of Bachman's sparrow Aimophila aestivalis, a species of management concern in the SE USA, and the landscape characteristics of the Savannah River Site, South Carolina, an area managed for timber production where the sparrow is relatively common. Life history characteristics used in the model include dispersal, survivorship, and reproductive success information reported for Bachmann's sparrow. Variation in demographic variables affect population size more than variation in dispersal ability. Changes in adult and juvenile survivorship have especially large impacts on the probability of population extinction. The presence of habitat types that serve as permanent sources of dispersers increases the total population size in the landscape, and lowers the probability of extinction. -from Authors
Article
Understanding the ability of species to shift their geographic range is of considerable importance given the current period of rapid climate change. Furthermore, a greater understanding of the spatial population dynamics underlying range shifting is required to complement the advances made in climate niche modelling. A simulation model is developed which incorporates three key features that have been largely overlooked in studies of range shifting dynamics: the form of intraspecific competition, density dependent dispersal and the transient dynamics of habitat patches. The results show that the exact shape of the response depends critically on both local and patch dynamics. Species whose intraspecific competition is contest based are more vulnerable than those whose competition is scramble based. Contesters are especially sensitive when combined with density dependent dispersal. Species living in patches whose carrying capacity grows slowly are also susceptible to rapid shifts of environmental conditions. A complementary analytic approach further highlights the importance of intraspecific competition.
Article
Loral extinction along the intrinsic isolation gradient within metapopulations is reviewed with particular reference to a study of the pool frog (Rana lessonaé) on the northern periphery of its geographical range. As in the pool frog, many other different tax a show significantly increased extinction probabilities with increased interpopulation distance. Present data imply that the relative impact of demographic and genetic factors in such stochastic extinctions depends on the genetic history of the metapopulation; data also imply that populations fluctuate more greatly in size than predicted from demographic models which have been commonly referred to. By mitigating such fluctuations and inbreeding, and compensating for emigration, immigration undoubtedly ‘rescues’ local populations from extinction. In this way, and not just in terms of recolonization, connectivity is concluded to be a key to metapopulation persistence. Implications for conservation are also presented.
Article
Mediterranean ecosystems are among the highest in species richness and endemism globally and are also among the most sensitive to climate and land-use change. Fire is an important driver of ecosystem processes in these systems; however, fire regimes have been substantially changed by human activities. Climate change is predicted to further alter fire regimes and species distributions, leading to habitat loss and threatening biodiversity. It is currently unknown what the population-level effects of these landscape-level changes will be. We linked a spatially explicit stochastic population model to dynamic bioclimate envelopes to investigate the effects of climate change, habitat loss and fragm entation and altered fire regime on population abundances of a long-lived obligate seeding shrub, Ceanothus verrucosus, a rare endemic species of southern California. We tested a range of fire return intervals under the present and two future climate scenarios. We also assessed the impact of potential anthropogenic land-use change by excluding land identified as developable by local governments. We found that the 35–50 year fire return interval resulted in the highest population abundances. Expected minimum population abundance (EMA) declined gradually as fire return interval increased, but declined dramatically for shorter fire intervals. Simulated future development resulted in a 33% decline in EMA, but relatively stable population trajectories over the time frame modeled. Relative changes in EMA for alternative fire intervals were similar for all climate and habitat loss scenarios, except under the more severe climate scenario which resulted in a change in the relative ranking of the fire scenarios. Our results show climate change to be the most serious threat facing obligate seeding shrubs embedded in urban landscapes, resulting in population decline and increased local extirpation, and that likely interactions with other threats increase risks to these species. Taking account of parameter uncertainty did not alter our conclusions.
Article
Polewards expansions of species' distributions have been attributed to climate warming, but evidence for climate-driven local extinctions at warm (low latitude/elevation) boundaries is equivocal. We surveyed the four species of butterflies that reach their southern limits in Britain. We visited 421 sites where the species had been recorded previously to determine whether recent extinctions were primarily due to climate or habitat changes. Coenonympha tullia had become extinct at 52% of study sites and all losses were associated with habitat degradation. Aricia artaxerxes was extinct from 50% of sites, with approximately one-third to half of extinctions associated with climate-related factors and the remainder with habitat loss. For Erebia aethiops (extinct from 24% of sites), approximately a quarter of the extinctions were associated with habitat and three-quarters with climate. For Erebia epiphron, extinctions (37% of sites) were attributed mainly to climate with almost no habitat effects. For the three species affected by climate, range boundaries retracted 70-100 km northwards (A. artaxerxes, E. aethiops) and 130-150 m uphill (E. epiphron) in the sample of sites analysed. These shifts are consistent with estimated latitudinal and elevational temperature shifts of 88 km northwards and 98 m uphill over the 19-year study period. These results suggest that the southern/warm range margins of some species are as sensitive to climate change as are northern/cool margins. Our data indicate that climate warming has been of comparable importance to habitat loss in driving local extinctions of northern species over the past few decades; future climate warming is likely to jeopardize the long-term survival of many northern and mountain species.
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We tabulate three measures of rarity: local abundance, breeding range size and elevational extent for the passerine birds of the New World. We determine what fraction of species is threatened with extinction within the combinations of these three measures. Species with smaller ranges, lower abundances and narrower elevational bands suffer higher levels of threat across lowland, montane and island species. For a given range size, lowland species suffer higher levels of threat than island or montane species. (This is counter to the intuition that island species — and those isolated on mountain tops — might be ecologically naïve.) When all three factors are considered together, there is only a slight tendency for lowland species to be disproportionately more threatened. Simply, island and montane species tend to be relatively common within their restricted ranges and their increased abundance reduces their likelihood of being threatened. Elevation is a consistent but relatively unimportant factor in determining threat; abundance and range size are much more important, and have an interactive effect on threatened status. We calculate the number of humans with which each species shares its breeding range, and find that this number does not aid in predicting threat status.
Article
Habitat destruction and fragmentation are the root causes of many conservation problems. We conducted a literature survey and canvassed the ecological community to identify experimental studies of terrestrial habitat fragmentation and to determine whether consistent themes were emerging from these studies. Our survey revealed 20 fragmentation experiments worldwide. Most studies focused on effects of fragmentation on species richness or on the abundance(s) of particular species. Other important themes were the effect of fragmentation in interspecific interactions, the role of corridors and landscape connectivity in individual movements and species richness, and the influences of edge effects on ecosystem services. Our comparisons showed a remarkable lack of consistency in results across studies, especially with regard to species richness and abundance relative to fragment size. Experiments with arthropods showed the best fit with theoretical expectations of greater species richness on larger fragments. Highly mobile taxa such as birds and mammals, early-successional plant species, long-lived species, and generalist predators did not respond in the “expected” manner. Reasons for these discrepancies included edge effects, competitive release in the habitat fragments, and the spatial scale of the experiments. One of the more consistently supported hypotheses was that movement and species richness are positively affected by corridors and connectivity, respectively. Transient effects dominated many systems; for example, crowding of individuals on fragments commonly was observed after fragmentation, followed by a relaxation toward lower abundance in subsequent years. The three long-term studies (14 years) revealed strong patterns that would have been missed in short-term investigations. Our results emphasize the wide range of species-specific responses to fragmentation, the need for elucidation of behavioral mechanisms affecting these responses, and the potential for changing responses to fragmentation over time. Resumen: La destrucción y la fragmentación del hábitat son las causas fundamentales de muchos problemas de conservación. Realizamos un sondeo de la literatura y examinamos de cerca la comunidad ecológica para identificar estudios experimentales sobre la fragmentación de hábitats terrestres y para determinar si emergen temas homogéneos de estos estudios. Nuestro sondeo revela que existen 20 estudios experimentales de fragmentación en el ámbito mundial. La mayoría de los estudios enfocan en los efectos de la fragmentación sobre la riqueza de especies, o en la(s) abundancia(s) de ciertas especies en particular. Otros temas importantes fueron el efecto de la fragmentación sobre las interacciones interespecíficas, el papel de los corredores y la conectividad del paisaje en los movimientos individuales y la riqueza de especies y la influencia de los efectos de bordes sobre los servicios proporcionados por el ecosistema. Nuestras comparaciones muestran una carencia notable de homogeneidad en los resultados de los estudios, especialmente en lo referente a la riqueza y a la abundancia de especies, y su relación con el tamaño de los fragmentos. Experimentos con artrópodos demostraron que existía un mejor ajuste entre los valores teóricos esperados y los valores reales de aumentos en la riqueza de especies en fragmentos grandes. Los taxones altamente móviles ( por ejemplo, aves y mamíferos), las especies de plantas en sucesión temprana, las especies de gran longevidad y los depredadores generalistas no respondieron de la manera “esperada”. Entre las razones que explican estas divergencias se incluyen los efectos de bordes, la liberación competitiva en los fragmentos de hábitat y la escala espacial del experimento. Una de las hipótesis más aceptadas establece que el movimiento y la riqueza de especies son afectadas positivamente por los corredores y la conectividad, respectivamente. Algunos efectos pasajeros dominaron muchos sistemas; por ejemplo, el hacinamiento de individuos en fragmentos se observó a menudo después de la fragmentación, seguido de un disminución de la abundancia en los años posteriores. Los tres estudios a largo plazo (=14 años) revelaron fuertes patrones que hubieran sido ignorados en investigaciones a corto plazo. Nuestros resultados señalan el amplio rango de respuestas especie-específicas, la necesidad de elucidar mecanismos de comportamiento que afectan las respuestas a la fragmentación y el potencial de respuestas cambiantes a la fragmentación a lo largo del tiempo.