Publications

Research manuscripts from students and faculty in the Center for Environmental Studies.  Student co-authors are indicated with (§) for undergraduates and () for graduates.

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Kramer GR, Andersen DE, Buehler DA, Wood PB, Peterson SM, Lehman JA, Aldinger KR, Bulluck LP, Harding S, Jones JA, Loegering JP, Smalling C, Vallender R, Streby HM.2018Population trends in Vermivora warblers are linked to strong migratory connectivity Proceedings of the National Academy of Sciences 14:E3192-E3200. https://doi.org/10.1073/pnas.1718985115.

Migratory species can experience limiting factors at different locations and during different periods of their annual cycle. In migratory birds, these factors may even occur in different hemispheres. Therefore, identifying the distribution of populations throughout their annual cycle (i.e., migratory connectivity) can reveal the complex ecological and evolutionary relationships that link species and ecosystems across the globe and illuminate where and how limiting factors influence population trends. A growing body of literature continues to identify species that exhibit weak connectivity wherein individuals from distinct breeding areas co-occur during the nonbreeding period. A detailed account of a broadly distributed species exhibiting strong migratory connectivity in which nonbreeding isolation of populations is associated with differential population trends remains undescribed. Here, we present a range-wide assessment of the nonbreeding distribution and migratory connectivity of two broadly dispersed Nearctic-Neotropical migratory songbirds. We used geolocators to track the movements of 70 Vermivora warblers from sites spanning their breeding distribution in eastern North America and identified links between breeding populations and nonbreeding areas. Unlike blue-winged warblers (Vermivora cyanoptera), breeding populations of golden-winged warblers (Vermivora chrysoptera) exhibited strong migratory connectivity, which was associated with historical trends in breeding populations: stable for populations that winter in Central America and declining for those that winter in northern South America.
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DeSaix MG2018Migratory patterns and population genetic structure in a declining wetland-dependent songbird MS Thesis https://scholarscompass.vcu.edu/etd/5432/.

Graduate Author(s)
Understanding migratory connectivity is essential for assessing the drivers behind population dynamics and for implementing effective management in migratory species. Genetic markers provide a means to describe migratory connectivity, as well as incorporate population genetic analyses, however genetic markers can be uninformative for species with weak genetic structure. In this study, we evaluate range-wide population genetic structure and migratory connectivity in the prothonotary warbler, Protonotaria citrea, a wetland-dependent neotropical migratory songbird, using high-resolution genetic markers. We reveal regional genetic structure between sampling sites in the Mississippi River Valley and the Atlantic Seaboard with overall weak genetic differentiation among populations (FST = 0.0051). By ranking loci by FST and using subsets of the most differentiated genetic markers (200 – 3000), we identify a maximum assignment accuracy (89.7% to site, 94.3% to region) using 600 single nucleotide polymorphisms. We assign samples from unknown origin nonbreeding sites to a breeding region, illustrating weak migratory connectivity between prothonotary warbler breeding and nonbreeding grounds. Our results highlight the importance of using high-resolution markers in studies of migratory connectivity with species exhibiting weak genetic structure. Using similar techniques, studies may begin to describe population genetic structure that was previously undocumented, allowing us to infer the migratory patterns of an increasing number of species.
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Fernandez L, Mukherjee M, Scott T2018The effect of conservation policy and varied open space on residential property values: A dynamic hedonic analysis Land User and Policy 73:480-487. https://doi.org/10.1016/j.landusepol.2017.12.058.

We investigate open space value in an ideal setting for a natural experiment between Riverside County, with an open space conservation policy, and neighboring San Bernardino County without the policy. With spatial econometrics, time series and spatial data, this study accounts for both spatial and temporal variation of open space values. The novelty of our paper is that we combine an investigation of the effect of open space proximity on residential property value with an analysis of the effect of endangered species habitat preservation policy distinguishing between types of open space (wild habitat for endangered species versus developed parks) in a two county study. We find that proximity to open space has a positive and statistically significant influence on increased value of residential real estate, with some distinction among type of open space between the counties. Conservation policy for open space with wild habitats contributes to increased value of this amenity in Riverside County.
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Miles LS, Johnson JC, Dyer RJ, Verrelli BC2018Urbanization as a facilitator of gene flow in a human health pest. Molecular Ecology https://doi.org/10.1111/mec.14783.

Graduate Author(s)
Urban fragmentation can reduce gene flow that isolates populations, reduces genetic diversity and increases population differentiation, all of which have negative conservation implications. Alternatively, gene flow may actually be increased among urban areas consistent with an urban facilitation model. In fact, urban adapter pests are able to thrive in the urban environment and may be experiencing human‐mediated transport. Here, we used social network theory with a population genetic approach to investigate the impact of urbanization on genetic connectivity in the Western black widow spider, as an urban pest model of human health concern. We collected genomewide SNP variation from mitochondrial and nuclear ddRAD sequence datasets from 210 individuals sampled from 11 urban and 10 non‐urban locales across its distribution of the Western U.S. From urban and non‐urban contrasts of population, phylogenetic, and network analyses, urban locales have higher within‐population genetic diversity, lower between‐population genetic differentiation, and higher estimates of genetic connectivity. Social network analyses show that urban locales not only have more connections, but can act as hubs that drive connectivity among non‐urban locales, which show signatures of historical isolation. These results are consistent with an urban facilitation model of gene flow, and demonstrate the importance of sampling multiple cities and markers to identify the role that urbanization has had on larger spatial scales. As the urban landscape continues to grow, this approach will help determine what factors influence the spread and adaptation of pests, like the venomous black widow spider, in building policies for human and biodiversity health.
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Bertrand‡ P, Bowman J, Dyer RJ, Manseau M, Wilson P.2017Sex-specific graphs: Relating group-specific topology to demographic and landscape data. Molecular Ecology 15:3898-3912. https://doi.org/10.1111/mec.14174.

Graduate Author(s)
Sex‐specific genetic structure is a commonly observed pattern among vertebrate species. Facing differential selective pressures, individuals may adopt sex‐specific life history traits that ultimately shape genetic variation among populations. Although differential dispersal dynamics are commonly detected in the literature, few studies have used genetic structure to investigate sex‐specific functional connectivity. The recent use of graph theoretic approaches in landscape genetics has demonstrated network capacities to describe complex system behaviours where network topology represents genetic interaction among subunits. Here, we partition the overall genetic structure into sex‐specific graphs, revealing different male and female dispersal dynamics of a fisher (Pekania [Martespennanti) metapopulation in southern Ontario. Our analyses based on network topologies supported the hypothesis of male‐biased dispersal. Furthermore, we demonstrated that the effect of the landscape, identified at the population level, could be partitioned among sex‐specific strata. We found that female connectivity was negatively correlated with snow depth, whereas connectivity among males was not. Our findings underscore the potential of conducting sex‐specific analysis by identifying landscape elements or configuration that differentially promotes or impedes functional connectivity between sexes, revealing processes that may otherwise remain cryptic. We propose that the sex‐specific graph approach would be applicable to other vagile species where differential sex‐specific processes are expected to occur.
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Salica‡ MJ, Vonesh JR, Warkentin KM2017Egg clutch dehydration induces early hatching in red-eyed treefrogs, Agalychnis callidryas PeerJ 5:e3549. https://dx.doi.org/10.7717%2Fpeerj.3549.

Graduate Author(s)
Terrestrial eggs have evolved repeatedly in tropical anurans exposing embryos to the new threat of dehydration. Red-eyed treefrogs, Agalychnis callidryas, lay eggs on plants over water. Maternally provided water allows shaded eggs in humid sites to develop to hatching without rainfall, but unshaded eggs and those in less humid sites can die from dehydration. Hatching responses of amphibian eggs to dry conditions are known from two lineages with independent origins of terrestrial eggs. Here, we experimentally tested for dehydration-induced early hatching in another lineage (Agalychnis callidryas, Phyllomedusidae), representing a third independent origin of terrestrial eggs. We also investigated how dehydration affected egg and clutch structure, and egg mortality. We collected clutches from a pond in Gamboa, Panama, and randomly allocated them to wet or dry treatments at age 1 day. Embryos hatched earlier from dry clutches than from wet clutches, accelerating hatching by ∼11%. Clutch thickness and egg diameter were affected by dehydration, diverging between treatments over time. Meanwhile, mortality in dry clutches was six-fold higher than in control clutches. With this study, early hatching responses to escape mortality from egg dehydration are now known from three anuran lineages with independent origins of terrestrial eggs, suggesting they may be widespread. Further studies are needed to understand how terrestrial amphibian eggs can respond to, or will be affected by, rapid changes in climate over the next decades.
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Sikder, AM, Hossain T, Kahn MH, Hasan MA, Fakhruzzaman M, Turner JB, Pestov D, McCallister LS, Elahi KM2017Toxicity assessment of ash and dust from handmade gold jewelry manufacturing workshops in Bangladesh Environmental Monitoring and Assessment 189: https://doi.org/10.1007/s10661-017-5978-3.

Traditionally, handmade gold jewelry played a very important role in the cultural heritage of Bangladesh. Goldsmiths still are partially using ancient manufacturing process with coal fire, candle flame blowing, and nitric and sulfuric acid treatments. Such process leads to the contamination of workplace with the dust of toxic metals, acidic vapors, and particles of different natures. To evaluate contamination by particulate matter (PM), the passive particle collectors were installed in different manufacturing units for a period of 85 days at Tanti Bazar, Dhaka, Bangladesh. The laser diffraction analysis of the samples collected at the soldering units showed significant amounts of particulates, both PM10 and PM 2.5, and also nanoparticles in both nucleation and accumulation mode. SEM/EDS analysis revealed partially melted micro blebs that contain a very high concentration of Fe along with Cu. The toxic elements were detected with ICP analysis and include higher concentrations of cadmium (Cd), chromium (Cr), lead (Pb), and arsenic (As). It is notable that detection of arsenic contamination was unexpected since raw materials used for jewelry making should not have any arsenic.

 

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