Influence of climate and land use on ecological patterns & population processes
Wetland gradient modeling |
Wetlands are highly dynamic ecosystem components that fluctuate dramatically in inundation and persistence of water both within and across years. However, these systems are commonly classified in a deterministic, discrete manner that does not reflect inherent spatial and temporal variation. We developed a methodology that applies probabilistic estimates, derived from a nonparametric model, to predict wetlands along a gradient in ephemerality, or degree of water inundation. We applied this model across four sampling areas in the Plains and Prairie Pothole Region (PPPR) in the U.S. Northern Great Plains. We developed a model relationship between high-resolution (RapidEye) and moderate resolution (Landsat) satellite sensor data. This allowed us leverage the benefits of high spatial resolution data and a long temporal series of freely available mid-resolution data to characterize water persistence in wetlands. Probabilistic predictions of wetland ephemerality contribute valuable information needed for management and policy decisions, especially given potential alterations to wetland ephemerality and ecosystem services under climate change. Using predicted gradients in wetland ephemerality over time will enable researchers and land managers to more effectively capture nuance in ecosystem condition, function, and change.
Climate change effects on wetland ephemeralityClimate change is a major landscape stressor predicted to substantially alter ecosystem characteristics. In semi-arid regions where water availability is a crucial concern, wetlands constitute a critical, though highly sensitive, ecosystem component. Altered temperature and precipitation regimes under climate change may affect wetland ephemerality, the degree of surface water inundation. We aim to assess the influence of climate on wetland ephemerality by (1) modeling wetland stochasticity over time through the characterization of variability in probability of surface water inundation over time; (2) linking wetland ephemerality to climatic variation across (a) a 30 year time series, and (b) across each year within the time series; and (3) predicting wetland ephemerality under a range of potential climate change scenarios representing potential changes to temperature, and precipitation amount and timing. By predicting flux in wetland persistence under numerous projected climatic conditions, this research seeks to identify the nature and degree to which wetland changes manifest due to climate change.
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Assessments of diversity across spatiotemporal scales
Integrating eDNA analyses & remote sensing to characterize amphibian diversity in spatiotemporally dynamic ecosystems
Habitat heterogeneity is a key driver of biodiversity. However, the relative importance of spatial and temporal variation on species diversity is poorly understood, particularly in highly dynamic landscapes, including wetland complexes. By integrating species diversity measurements from environmental DNA (eDNA) analyses of 315 wetlands with remotely sensed estimates of surface water inundation, this research evaluated the influence of wetland permanence and stochasticity on amphibian occurrence and abundance across four separate spatial–temporal scales: (i) wetland; (ii) landscape context; (iii) wetland across time, and (iv) landscape context across time. To examine these questions, we used a model system consisting of three co-occurring amphibian species that collectively occupy wetlands spanning a gradient in permanence: boreal chorus frogs (Pseudacris maculata, highly ephemeral), northern leopard frogs (Lithobates pipiens, generally semi-permanent), and barred tiger salamanders (Ambystoma mavortium, primarily permanent water bodies).
We found that habitat heterogeneity in both space and time yielded higher species richness and abundance, and that individual species responded to landscape heterogeneity consistent with a priori expectations based on species’ life history strategies. Our results support the habitat heterogeneity hypothesis by demonstrating that both spatial and temporal heterogeneity – caused by fluctuations in wetland permanence – drive species diversity in dynamic wetland-dominated ecosystems. Maintaining a diversity of habitats that vary both spatially and temporally across the landscape is critical to species conservation and ecosystem function, particularly in light of projected climate change.
We found that habitat heterogeneity in both space and time yielded higher species richness and abundance, and that individual species responded to landscape heterogeneity consistent with a priori expectations based on species’ life history strategies. Our results support the habitat heterogeneity hypothesis by demonstrating that both spatial and temporal heterogeneity – caused by fluctuations in wetland permanence – drive species diversity in dynamic wetland-dominated ecosystems. Maintaining a diversity of habitats that vary both spatially and temporally across the landscape is critical to species conservation and ecosystem function, particularly in light of projected climate change.
Genetic diversity of a vernal-pool breeding amphibian along a gradient of fragmentation |
My master's research characterized the effects of forest fragmentation, water quality, and hydroperiod on the genetic structure of a vernal pool-breeding amphibian, the wood frog (Lithobates sylvaticus) between two landscape types: an unfragmented, forested landscape, and a landscape fragmented by moderate suburban development.
The results of this study indicated that wood frog populations are well connected, with high gene flow, across the landscape of southeastern New Hampshire, and that fragmenting features of suburbanization (e.g., roads, suburban development) to date have a small but detectable impact on fine-scale genetic structure. Our findings also highlighted the importance of replication in landscape genetic studies, as the genetic response we detected varied with a gradient of fragmentation.
The results of this study indicated that wood frog populations are well connected, with high gene flow, across the landscape of southeastern New Hampshire, and that fragmenting features of suburbanization (e.g., roads, suburban development) to date have a small but detectable impact on fine-scale genetic structure. Our findings also highlighted the importance of replication in landscape genetic studies, as the genetic response we detected varied with a gradient of fragmentation.
Comparative landscape genetics of three amphibians with varied hydroperiod requirements
The goal of this study is to characterize gene flow and functional connectivity of two amphibian species (Pseudacris maculata, Lithobates pipiens) and relate connectivity metrics to wetland ephemerality at at-site species diversity using a landscape genetics approach. Despite overlapping ranges, the species’ hydroperiod requirements differ, which may cause unique responses to climate-induced hydroperiod changes. Within each sampling area, I will visit 20 wetlands, in each case collecting 20-30 individual tissue samples per species from adult buccal swabs and tadpole tail clips. I will extract DNA and genotype each species at 12 polymorphic, species-specific microsatellite loci. I will relate genetic distance between individual species’ populations to classified ephemerality, topography, landscape composition, and landscape configuration. Using gravity models, I will characterize functional connectivity with respect to current and projected wetland persistence.
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Landscape-scale genetic response to road fragmentation across taxonomic groups
Roads have many significant ecological impacts that affect a disproportionately large area of the landscape. As roads extend over large distances, they are likely to have greater landscape-level impacts than other sources of habitat fragmentation and habitat loss. We aim to address two questions: (1) how does landscape fragmentation by roads influence genetic diversity and genetic structure of plant and animal populations at the “landscape” scale?, and (2) how do genetic responses to fragmentation by roads vary across taxa? To do so, we review existing literature and accompanying genetic and spatial datasets, as well as detailed road data for North America, in order to characterize genetic diversity of several species in relation to fragmentation by roads calculated across landscape scales.
This study is in collaboration with members of the Landscape Genetics Distributed Graduate Seminar. |
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