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Toby A Gardner,
Joice Ferreira,
Jos Barlow,
Alexander C Lees,
Luke Parry,
Ima Célia Guimarães Vieira,
Erika Berenguer,
Ricardo Abramovay,
Alexandre Aleixo,
Christian Andretti, [......],
Nicola Savério Holanda Tancredi,
James R Thomson,
Patrícia Carignano Torres,
Fernando Zagury Vaz-de-Mello,
Ruan Carlo Stulpen Veiga,
Adriano Venturieri,
Cecília Viana,
Diana Weinhold,
Ronald Zanetti,
Jansen Zuanon
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ABSTRACT: Science has a critical role to play in guiding more sustainable development trajectories. Here, we present the Sustainable Amazon Network (Rede Amazônia Sustentável, RAS): a multidisciplinary research initiative involving more than 30 partner organizations working to assess both social and ecological dimensions of land-use sustainability in eastern Brazilian Amazonia. The research approach adopted by RAS offers three advantages for addressing land-use sustainability problems: (i) the collection of synchronized and co-located ecological and socioeconomic data across broad gradients of past and present human use; (ii) a nested sampling design to aid comparison of ecological and socioeconomic conditions associated with different land uses across local, landscape and regional scales; and (iii) a strong engagement with a wide variety of actors and non-research institutions. Here, we elaborate on these key features, and identify the ways in which RAS can help in highlighting those problems in most urgent need of attention, and in guiding improvements in land-use sustainability in Amazonia and elsewhere in the tropics. We also discuss some of the practical lessons, limitations and realities faced during the development of the RAS initiative so far.
Philosophical Transactions of The Royal Society B Biological Sciences 01/2013; 368(1619):20120166. · 6.40 Impact Factor
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ABSTRACT: With the expected increase in the spread of invasive species, examination of factors controlling distributions at multiple
spatial scales and ecological modelling of their potential distributions are important analyses for informed decision-making.
The scale-dependence of mechanisms influencing invasion by non-native species has been shown previously, indicating that studies
of key factors affecting invasive species distributions at multiple spatial scales are critical for successful management.
Freshwater systems are particularly vulnerable to invasive species, yet few studies have examined the environmental factors
influencing distributions of invasive species at multiple spatial scales. We examined the effect of environmental variables
on the predicted distribution of the invasive aquatic grass Glyceriamaxima over continental, regional and local scales in Australia. We undertook an initial critical evaluation of which predictor
variables were most appropriate to use at each scale, largely considering prior knowledge. On a continental scale, climatic,
topographic and hydrological variables predicted well the potential distribution of G.maxima, identifying temperate regions as most susceptible to invasion. The regional analysis found that dense, woody, riparian vegetation has a strong negative impact on the occurrence of G.maxima, especially at intermediate elevations. The invasive grass was found less often on biotite granite and on fluvial geology.
At a local scale, occurrence of G.maxima was related positively to soil phosphorus and nitrogen, and negatively related to soil organic carbon. The identification
of key factors affecting invasive species distributions at multiple spatial scales will inform prevention schemes, assist
targeted field sampling for the development of monitoring programs, and allow prioritization of control methods.
Biological Invasions 04/2012; 11(8):1903-1912. · 2.90 Impact Factor
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ABSTRACT: Humans have altered many floodplain ecosystems around the world by clearing vegetation, building towns and regulating river
flows. Studies discerning gene flow and population structure of floodplain-dwelling animals are rare yet are necessary for
understanding the effects of human actions on native populations. In south-eastern Australia, the yellow-footed antechinus
(Antechinus flavipes) is the only carnivorous marsupial on many lowland floodplains, yet our knowledge of impacts of human activities is limited.
The control region of mitochondrial DNA and 11 microsatellite DNA markers were used to explore historic and current gene flow
in A. flavipes across and along the Murray River. Simulations were carried out to test different migration models. We found evidence for
historic gene flow along and across the river but inferred that small towns and farmland or cleared floodplain sections restricted
current gene flow along the river. Populations along the river appear to be isolated, and should be maintained at large enough
sizes to avoid genetic problems such as inbreeding depression and loss of evolutionary potential. We also investigated whether
50-year-long maintenance of high water levels for irrigation in summer, at the time of juvenile dispersal, has led to restrictions
in gene flow across the river. We found no evidence for restrictions to gene flow across the river and suggest that large
floods and dropping tree branches may aid dispersal across the river.
Conservation Genetics 04/2012; 9(3):569-580. · 1.61 Impact Factor
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ABSTRACT: In many environmental management problems, the construction of occurrence maps of species of interest is a prerequisite to
their effective management. However, the construction of occurrence maps is a challenging problem because observations are
often costly to obtain (thus incomplete) and noisy (thus imperfect). It is therefore critical to develop tools for designing
efficient spatial sampling strategies and for addressing data uncertainty. Adaptive sampling strategies are known to be more
efficient than non-adaptive strategies. Here, we develop a model-based adaptive spatial sampling method for the construction
of occurrence maps. We apply the method to estimate the occurrence of one of the world’s worst invasive species, the red imported
fire ant, in and around the city of Brisbane, Australia. Our contribution is threefold: (i)amodel of uncertainty about invasion
maps using the classical image analysis probabilistic framework of Hidden Markov Random Fields (HMRF), (ii)an original exact
method for optimal spatial sampling with HMRF and approximate solution algorithms for this problem, both in the static and
adaptive sampling cases, (iii)an empirical evaluation of these methods on simulated problems inspired by the fire ants case
study. Our analysis demonstrates that the adaptive strategy can lead to substantial improvement in occurrence mapping.
KeywordsHidden Markov random fields–Optimal sampling approximation–Fire ant sampling for mapping
Statistics and Computing 04/2012; · 1.43 Impact Factor
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ABSTRACT: In multiply invaded ecosystems, introduced species should interact with each other as well as with native species. Invader-invader interactions may affect the success of further invaders by altering attributes of recipient communities and propagule pressure. The invasional meltdown hypothesis (IMH) posits that positive interactions among invaders initiate positive population-level feedback that intensifies impacts and promotes secondary invasions. IMH remains controversial: few studies show feedback between invaders that amplifies their effects, and none yet demonstrate facilitation of entry and spread of secondary invaders. Our results show that supercolonies of an alien ant, promoted by mutualism with introduced honeydew-secreting scale insects, permitted invasion by an exotic land snail on Christmas Island, Indian Ocean. Modeling of land snail spread over 750 sites across 135 km2 over seven years showed that the probability of land snail invasion was facilitated 253-fold in ant supercolonies but impeded in intact forest where predaceous native land crabs remained abundant. Land snail occurrence at neighboring sites, a measure of propagule pressure, also promoted land snail spread. Site comparisons and experiments revealed that ant supercolonies, by killing land crabs but not land snails, disrupted biotic resistance and provided enemy-free space. Predation pressure on land snails was lower (28.6%), survival 115 times longer, and abundance 20-fold greater in supercolonies than in intact forest. Whole-ecosystem suppression of supercolonies reversed the probability of land snail invasion by allowing recolonization of land crabs; land snails were much less likely (0.79%) to invade sites where supercolonies were suppressed than where they remained intact. Our results provide strong empirical evidence for IMH by demonstrating that mutualism between invaders reconfigures key interactions in the recipient community. This facilitates entry of secondary invaders and elevates propagule pressure, propagating their spread at the whole-ecosystem level. We show that identification and management of key facilitative interactions in invaded ecosystems can be used to reverse impacts and restore resistance to further invasions.
Ecology 09/2011; 92(9):1758-68. · 4.85 Impact Factor
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ABSTRACT: Environmental perturbation, climate change and international commerce are important drivers for biological invasions. Climate anomalies can further increase levels of habitat disturbance and act synergistically to elevate invasion risk. Herein, we use a historical data set from the upper San Francisco Estuary to provide the first empirical evidence for facilitation of invasions by climate extremes. Invasive zooplankton species did not become established in this estuary until the 1970s when increasing propagule pressure from Asia coincided with extended drought periods. Hydrological management exacerbated the effects of post-1960 droughts and reduced freshwater inflow even further, increasing drought severity and allowing unusually extreme salinity intrusions. Native zooplankton experienced unprecedented conditions of high salinity and intensified benthic grazing, and life history attributes of invasive zooplankton were advantageous enough during droughts to outcompete native species and colonise the system. Extreme climatic events can therefore act synergistically with environmental perturbation to facilitate the establishment of invasive species.
Ecology Letters 06/2011; 14(8):749-57. · 17.56 Impact Factor
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William J Sutherland,
Sarah Bardsley,
Leon Bennun,
Mick Clout,
Isabelle M Côté,
Michael H Depledge,
Lynn V Dicks,
Andrew P Dobson,
Liz Fellman,
Erica Fleishman, [......],
Thomas E Lovejoy, Ralph Mac Nally,
Jane Madgwick,
Lloyd S Peck,
Jules Pretty,
Stephanie V Prior,
Kent H Redford,
Jörn P W Scharlemann,
Mark Spalding,
Andrew R Watkinson
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ABSTRACT: This review describes outcomes of a 2010 horizon-scanning exercise building upon the first exercise conducted in 2009. The aim of both horizon scans was to identify emerging issues that could have substantial impacts on the conservation of biological diversity, and to do so sufficiently early to encourage policy-relevant, practical research on those issues. Our group included professional horizon scanners and researchers affiliated with universities and non- and inter-governmental organizations, including specialists on topics such as invasive species, wildlife diseases and coral reefs. We identified 15 nascent issues, including new greenhouse gases, genetic techniques to eradicate mosquitoes, milk consumption in Asia and societal pessimism.
Trends in Ecology & Evolution 01/2011; 26(1):10-6. · 15.75 Impact Factor
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ABSTRACT: Drying can be a common disturbance affecting macroinvertebrate communities in headwater streams. Whether intermittent and ephemeral streams have a lower diversity and (or) unique assemblage structure relative to physically similar and nearby perennial streams is still debated. We investigated changes in the diversity and assemblage composition of aquatic macroinvertebrates occupying debris dams in three headwater streams with a gradient of flow permanence (perennial, intermittent, and ephemeral) during a dry period in the austral summer of 2007 and a wet period in the spring of 2008. In the dry period, mean taxon richness and abundance in debris dams were lower in the intermittent and ephemeral streams than in the perennial stream, and the length of time without connected surface flow appeared to produce different patterns in community composition. However, during the wet period, mean taxon richness, abundance, and community composition of macroinvertebrates were very similar among the three streams. Hierarchical Bayesian modeling showed evidence for a strong effect of permanence on taxon richness, abundance, and evenness within debris dams. Taxa from the perennial stream were extremely efficient at colonizing seasonally dry nearby streams. Differences in assemblage structure between these temporary and permanent headwater streams may only arise seasonally and also appear related to flow permanence.La sécheresse peut être une perturbation qui affecte fréquemment les communautés de macroinvertébrés dans les cours d'eau d'amont. Il existe encore un débat à savoir si les cours d'eau temporaires et éphémères possèdent une diversité réduite et (ou) une structure de peuplement particulière par rapport aux cours d'eau permanents physiquement semblables et situés à proximité. Nous avons étudié les changements de diversité et de composition des peuplements de macroinvertébrés aquatiques dans les barrages de débris dans trois cours d'eau d'amont présentant un gradient de permanence du débit (permanent, intermittent et éphémère) durant une période de sécheresse pendant l'été austral en 2007 et une période de précipitations au printemps 2008. Durant la période sèche, la richesse moyenne en taxons et l'abondance dans les barrages de débris étaient plus basses dans les cours d'eau intermittent et éphémère que dans le permanent et la durée de la période sans écoulement continu en surface semble déterminer des patrons différents de composition de la communauté. Cependant, durant la période humide, la richesse moyenne en taxons, ainsi que l'abondance et la composition de la communauté de macroinvertébrés, sont très semblables dans les trois cours d'eau. Une modélisation hiérarchique bayésienne donne des indications d'un effet important de la permanence sur la richesse taxonomique, l'abondance et l'équitabilité dans les barrages de débris. Les taxons provenant du ruisseau permanent sont extrêmement efficaces pour coloniser les ruisseaux à sécheresse saisonnière situés à proximité. Les différences de structure de peuplement entre les cours d'eau d'amont temporaires et permanents peuvent n'exister que saisonnièrement et semblent reliées à la persistance de l'écoulement.
Canadian Journal of Fisheries and Aquatic Sciences 09/2010; 67(10):1649-1657. · 2.21 Impact Factor
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ABSTRACT: We explored how a woody plant invader affected riparian bird assemblages. We surveyed 15 200-m-long transects in riparian zones in a much-changed landscape of eastern Victoria, Australia. Abundance, species-richness, foraging-guild richness and composition of birds were compared in transects in three habitat types: (i) riparian zones dominated by the invasive willow Salix × rubens; (ii) riparian zones lined with native woody species; and (iii) riparian zones cleared of almost all woody vegetation. We also measured abundance and richness of arthropods and habitat structure to explore further the effects of food resources and habitat on the avifauna. We observed 67 bird species from 14 foraging guilds. Native riparian transects had more birds, bird species and foraging guilds than willow-invaded or cleared transects. Habitat complexity increased from cleared to willow-invaded to native riparian transects, as did abundance of native and woodland-dependent birds. Native shrub and trees species had more foliage and branch-associated arthropods than did willows, consistent with a greater abundance and variety of foraging guilds of birds dependent on this resource. Willow spread into cleared areas is unlikely to facilitate greatly native bird abundance and diversity even though habitat complexity is increased. Willow invasion into the native riparian zone, by decreasing food resources and altering habitat, is likely to reduce native bird biodiversity and further disrupt connectivity of the riparian zone.
Austral Ecology 09/2010; 36(5):511 - 520. · 1.82 Impact Factor
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ABSTRACT: Aim We investigated partitioning of aquatic macroinvertebrate diversity in eight headwater streams to determine the relative contributions of α and β diversity to γ diversity, and the scale dependence of α and β components.Location Great Dividing Range, Victoria, Australia.Methods We used the method of Jost (Ecology, 2007, 88, 2427–2439) to partition γ diversity into its α and β components. We undertook the analyses at both reach and catchment scales to explore whether inferences depended on scale of observation.Results We hypothesized that β diversity would make a large contribution to the γ diversity of macroinvertebrates in our dendritic riverine landscape, particularly at the larger spatial scale (among catchments) because of limited dispersal among sites and especially among catchments. However, reaches each had relatively high taxon richness and high α diversity, while β diversity made only a small contribution to γ diversity at both the reach and catchment scales.Main conclusions Dendritic riverine landscapes have been thought to generate high β diversity as a consequence of limited dispersal and high heterogeneity among individual streams, but this may not hold for all headwater stream systems. Here, α diversity was high and β diversity low, with individual headwater stream reaches each containing a large portion of γ diversity. Thus, each stream could be considered to have low irreplaceability since losing the option to use one of these sites in a representative reserve network does not greatly diminish the options available for completing the reserve network. Where limited information on individual taxonomic distributions is available, or time and money for modelling approaches are limited, diversity partitioning may provide a useful ‘first-cut’ for obtaining information about the irreplaceability of individual streams or subcatchments when establishing representative freshwater reserves.
Diversity and Distributions 08/2010; 16(5):725 - 736. · 4.83 Impact Factor
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ABSTRACT: To eradicate or effectively contain a biological invasion, all or most reproductive individuals of the invasion must be found and destroyed. To help find individual invading organisms, predictions of probable locations can be made with statistical models. We estimated spread dynamics based on time-series data and then used model-derived predictions of probable locations of individuals. We considered one of the largest data sets available for an eradication program: the campaign to eradicate the red imported fire ant (Solenopsis invicta) from around Brisbane, Australia. After estimating within-site growth (local growth) and intersite dispersal (saltatory spread) of fire ant nests, we modeled probabilities of fire ant presence for >600000 1-ha sites, including uncertainties about fire ant population and spatial dynamics. Such a high level of spatial detail is required to assist surveillance efforts but is difficult to incorporate into common modeling methods because of high computational costs. More than twice as many fire ant nests would have been found in 2008 using predictions made with our method rather than those made with the method currently used in the study region. Our method is suited to considering invasions in which a large area is occupied by the invader at low density. Improved predictions of such invasions can dramatically reduce the area that needs to be searched to find the majority of individuals, assisting containment efforts and potentially making eradication a realistic goal for many invasions previously thought to be ineradicable.
Ecological Applications 07/2010; 20(5):1217-27. · 5.10 Impact Factor
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ABSTRACT: We examined trends in abundance of four pelagic fish species (delta smelt, longfin smelt, striped bass, and threadfin shad) in the upper San Francisco Estuary, California, USA, over 40 years using Bayesian change point models. Change point models identify times of abrupt or unusual changes in absolute abundance (step changes) or in rates of change in abundance (trend changes). We coupled Bayesian model selection with linear regression splines to identify biotic or abiotic covariates with the strongest associations with abundances of each species. We then refitted change point models conditional on the selected covariates to explore whether those covariates could explain statistical trends or change points in species abundances. We also fitted a multispecies change point model that identified change points common to all species. All models included hierarchical structures to model data uncertainties, including observation errors and missing covariate values. There were step declines in abundances of all four species in the early 2000s, with a likely common decline in 2002. Abiotic variables, including water clarity, position of the 2 per thousand isohaline (X2), and the volume of freshwater exported from the estuary, explained some variation in species' abundances over the time series, but no selected covariates could explain statistically the post-2000 change points for any species.
Ecological Applications 07/2010; 20(5):1431-48. · 5.10 Impact Factor
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Ralph Mac Nally,
James R Thomson,
Wim J Kimmerer,
Frederick Feyrer,
Ken B Newman,
Andy Sih,
William A Bennett,
Larry Brown,
Erica Fleishman,
Steven D Culberson,
Gonzalo Castillo
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ABSTRACT: Four species of pelagic fish of particular management concern in the upper San Francisco Estuary, California, USA, have declined precipitously since ca. 2002: delta smelt (Hypomesus transpacificus), longfin smelt (Spirinchus thaleichthys), striped bass (Morone saxatilis), and threadfin shad (Dorosoma petenense). The estuary has been monitored since the late 1960s with extensive collection of data on the fishes, their pelagic prey, phytoplankton biomass, invasive species, and physical factors. We used multivariate autoregressive (MAR) modeling to discern the main factors responsible for the declines. An expert-elicited model was built to describe the system. Fifty-four relationships were built into the model, only one of which was of uncertain direction a priori. Twenty-eight of the proposed relationships were strongly supported by or consistent with the data, while 26 were close to zero (not supported by the data but not contrary to expectations). The position of the 2 per thousand isohaline (a measure of the physical response of the estuary to freshwater flow) and increased water clarity over the period of analyses were two factors affecting multiple declining taxa (including fishes and the fishes' main zooplankton prey): Our results were relatively robust with respect to the form of stock-recruitment model used and to inclusion of subsidiary covariates but may be enhanced by using detailed state-space models that describe more fully the life-history dynamics of the declining species.
Ecological Applications 07/2010; 20(5):1417-30. · 5.10 Impact Factor
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ABSTRACT: Habitat connectivity is required at large spatial scales to facilitate movement of biota in response to climatic changes and to maintain viable populations of wide-ranging species. Nevertheless, it may require decades to acquire habitat linkages at such scales, and areas that could provide linkages are often developed before they can be reserved. Reserve scheduling methods usually consider only current threats, but threats change over time as development spreads and reaches presently secure areas. We investigated the importance of considering future threats when implementing projects to maintain habitat connectivity at a regional scale. To do so, we compared forward-looking scheduling strategies with strategies that consider only current threats. The strategies were applied to a Costa Rican case study, where many reserves face imminent isolation and other reserves will probably become isolated in the more distant future. We evaluated strategies in terms of two landscape-scale connectivity metrics, a pure connectivity metric and a metric of connected habitat diversity. Those strategies that considered only current threats were unreliable because they often failed to complete planned habitat linkage projects. The most reliable and effective strategies considered the future spread of development and its impact on the likelihood of completing planned habitat linkage projects. Our analyses highlight the critical need to consider future threats when building connected reserve networks over time.
Conservation Biology 06/2010; 24(3):691-700. · 4.69 Impact Factor
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Environmental Modelling and Software. 01/2010; 25:444-454.
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ABSTRACT: Aquatic ecosystems around the world have been massively altered through vegetation clearance and changed flow regimes accompanying agricultural development. Impacts may include disrupted dispersal for aquatic species. We investigated this in lentic (standing) waterbodies in agricultural and predominantly forested landscapes of the boxironbark region of central Victoria, Australia. We hypothesised that higher representation in forested than agricultural landscapes (i.e. ‘forest-bias’) for a species may reflect an ability to disperse more easily through the former, resulting in lower genetic structure in forested than in agricultural landscapes. Conversely, ‘cosmopolitan’ species would show no difference in genetic structure between landscape types. Molecular genetic analyses of a forest-biased diving beetle, Necterosoma wollastoni, and a cosmopolitan waterboatman, Micronecta gracilis, revealed the following, for both species: (1) no evidence for long-term barriers to gene flow in the region, (2) lack of contemporary genetic differentiation over 30 000 km2 and (3) random distribution of related genotypes in space, implying that neither forest nor farmland inhibits their dispersal in a concerted fashion. Taken together, these results indicate very high gene flow and dispersal in the past and present for both these species. Massive landscape change may have little impact on movement patterns of lentic invertebrates that have evolved high dispersal capabilities.
Marine and Freshwater Research 01/2010; 61:1318–1326. · 1.60 Impact Factor
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ABSTRACT: Biological invasions can alter direct and indirect interactions between species, generating far-reaching changes in ecological networks that affect key ecological functions. We used model and real fruit assays to show that the invasion and formation of high-density supercolonies by the yellow crazy ant (YCA), Anoplolepis gracilipes, disrupt frugivory by endemic birds on Christmas Island, Indian Ocean. The overall handling rates of model fruits by birds were 2.2-2.4-fold lower in ant-invaded than in uninvaded rainforest, and pecking rates by two bird species declined by 2.6- and 4.5-fold, respectively. YCAs directly interfered with frugivory; their experimental exclusion from fruiting displays increased fruit handling threefold to sixfold, compounding indirect effects of ant invasion on resources and habitat structure that influence bird abundances and behaviours. This invasive ant, whose high densities are sustained through mutualism with introduced scale insects, rapidly decreases fruit handling by endemic island birds and may erode a key ecological function, seed dispersal. Because most other invasive ant species form expansive, high-density supercolonies that depend in part on association with hemipteran mutualists, the effects that we report here on avian frugivore-plant associations may emerge across their introduced ranges.
Biology letters 09/2009; 6(1):85-8. · 3.76 Impact Factor
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ABSTRACT: Aim We explored whether the anuran amphibian faunas differed among landscapes that are relatively intact (largely covered in forests and woodlands) and others that are completely converted to agriculture. We also used historical data sets to assess the current condition of the anuran fauna in a region predicted to experience, and experiencing, severe drying and warming.Location Five pairs of landscapes (each of c. 20 km2) – one in each pair being almost completely wooded and the other cleared for agriculture – across a 30,000 km2 region of northern Victoria, Australia.Methods Sites were repeatedly surveyed in the austral winter–spring breeding seasons of 2006 and 2007, with records collected of numbers of calling males and the presence of egg masses and tadpoles. We characterized the sites using static (e.g. dimensions, surrounding physiognomic characteristics such as tree cover) and labile (e.g. pH, dissolved oxygen) variables. Data were analysed using hierarchical Bayesian models.Results For calling males, landscape type did not affect densities or species richness measures. The availability of a grassy verge around water bodies was an important predictor for most species, but other labile and static variables seemed not to be important. Fewer than half of the species historically known from the region were recorded. There were no important predictors of occurrence of egg masses or tadpoles. Reproduction effectively may have failed over the period, with fewer than one in four sites showing evidence of egg masses or tadpoles.Main conclusions The proportion of sites at which some well-studied species (e.g. Crinia signifera, Limnodynastes dumerilii) were recorded has dropped substantially since the 1970s, as have average densities of calling males of Crinia spp. The remnant anuran fauna appears to be dominated by resilient and hardy species with low current diversity. The on-going (12+ years) drought in these landscapes suggests a bleak long-term prognosis for the few remaining species of anuran amphibians.
Global Ecology and Biogeography. 08/2009; 18(5):575 - 585.
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ABSTRACT: Fallen timber (logs, large boughs) is recognized as having high ecological significance on forest floors. In floodplain forests, fallen timber potentially has even higher value for supporting biodiversity than upland forests because distinct faunal elements use the timber in the flooded and unflooded conditions. Invertebrates were sampled in logs of the river red gum (Eucalyptus camaldulensis Dehnh.) that had been inundated 1 year earlier and compared with invertebrates in logs that had not been inundated for many years. The invertebrate fauna in river red gum logs was relatively depauperate, probably reflecting the variable, sub-humid conditions on the floodplain. The abundance and taxon richness of invertebrates was highest in logs with greater structural complexity and heterogeneity due to extensive decay. Recent inundation slightly reduced taxon richness. The succession of log-dwelling invertebrates was tracked though transitions between terrestrial fauna and aquatic fauna in a spring/summer flood cycle. Transition between the two faunae was rapid. Logs were colonized by aquatic invertebrates within 2 weeks of immersion by floodwaters and recolonized by terrestrial invertebrates within 4 weeks of emersion. This faunal dynamism highlights the need to consider the entire flood cycle in decisions about the management of fallen timber on floodplains for biodiversity. Copyright © 2009 John Wiley & Sons, Ltd.
River Research and Applications 03/2009; 26(2):207 - 219. · 2.03 Impact Factor
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ABSTRACT: Aim
We explored whether the anuran amphibian faunas differed among landscapes that are relatively intact (largely covered in forests and woodlands) and others that are completely converted to agriculture. We also used historical data sets to assess the current condition of the anuran fauna in a region predicted to experience, and experiencing, severe drying and warming.
Location
Five pairs of landscapes (each of c. 20 km2) – one in each pair being almost completely wooded and the other cleared for agriculture – across a 30,000 km2 region of northern Victoria, Australia.
Methods
Sites were repeatedly surveyed in the austral winter–spring breeding seasons of 2006 and 2007, with records collected of numbers of calling males and the presence of egg masses and tadpoles. We characterized the sites using static (e.g. dimensions, surrounding physiognomic characteristics such as tree cover) and labile (e.g. pH, dissolved oxygen) variables. Data were analysed using hierarchical Bayesian
models.
Results
For calling males, landscape type did not affect densities or species richness measures. The availability of a grassy verge around water bodies was an important predictor for most species, but other labile and static variables seemed not to be important. Fewer than half of the species historically known from the
region were recorded. There were no important predictors of occurrence of egg masses or tadpoles. Reproduction effectively may have failed over the period, with fewer than one in four sites showing evidence of egg masses or tadpoles.
Main conclusions
The proportion of sites at which some well-studied species (e.g. Crinia signifera, Limnodynastes dumerilii) were recorded has dropped substantially since the 1970s, as have average densities of calling males of
Crinia spp. The remnant anuran fauna appears to be dominated by resilient and hardy species
with low current diversity. The on-going (12+ years) drought in these landscapes suggests a bleak long-term prognosis for the few remaining species of anuran amphibians.
Global Ecology and Biogeography 01/2009; 18:575¬–585. · 5.14 Impact Factor
