Search

Dryad Logo
Continent-wide effects of urbanization on bird and mammal genetic diversity
Schmidt, Chloé; Domaratzki, Michael; Kinnunen, Riikka; Bowman, Jeff; Garroway, Colin — 2020-01-20 <p>Urbanization and associated<b> </b>environmental changes are causing global declines in vertebrate populations. In general, population declines of the magnitudes now detected should lead to reduced effective population sizes for animals living in proximity to humans and disturbed lands. This is cause for concern because effective population sizes set the rate of genetic diversity loss due to genetic drift, the rate of increase in inbreeding, and the efficiency with which selection can act on beneficial alleles. We predicted that the effects of urbanization should decrease effective population size and genetic diversity, and increase population-level genetic differentiation. To test for such patterns, we repurposed and reanalyzed publicly archived genetic data sets for North American birds and mammals. After filtering, we had usable raw genotype data from 85 studies and 41,023 individuals, sampled from 1,008 locations spanning 41 mammal and 25 bird species. We used census-based urban-rural designations, human population density, and the Human Footprint Index as measures of urbanization and habitat disturbance. As predicted, mammals sampled in more disturbed environments had lower effective population sizes and genetic diversity, and were more genetically differentiated from those in more natural environments. There were no consistent relationships detectable for birds. This suggests that, in general, mammal populations living near humans may have less capacity to respond adaptively to further environmental changes, and be more likely to suffer from effects of inbreeding.</p>
Dryad Logo
The population genetics of urban and rural amphibians in North America
Dryad
Schmidt, Chloé; Garroway, Colin — 2021-06-04 <p>Human land transformation is one of the leading causes of vertebrate population declines. These declines are thought to be partly due to decreased connectivity and habitat loss reducing animal population sizes in disturbed habitats. With time, this can lead to declines in effective population size and genetic diversity which restricts the ability of wildlife to efficiently cope with environmental change through genetic adaptation. However, it is not well understood whether these effects generally hold across taxa. We address this question by repurposing and synthesizing raw microsatellite data from online repositories for 19 amphibian species sampled at 554 georeferenced sites in North America. For each site, we estimated gene diversity, allelic richness, effective population size, and population differentiation. Using binary urban-rural census designations, and continuous measures of human population density, the Human Footprint Index, and impervious surface cover, we tested for generalizable effects of human land use on amphibian genetic diversity. We found minimal evidence, either positive or negative, for relationships between genetic metrics and urbanization in our repurposed data. Together with previous work on focal species that also found varying effects of urbanization on genetic composition, it seems likely that the consequences of urbanization are not easily generalizable within or across amphibian species. Questions about the genetic consequences of urbanization for amphibians should be addressed on a case-by-case basis. This contrasts with general negative effects of urbanization in mammals and consistent, but species-specific, positive and negative effects in birds.</p>
Dryad Logo
Structural and socioeconomic features of cities predict migratory bird species richness
Dryad
Kinnunen, Riikka; Fraser, Kevin; Schmidt, Chloé; Garroway, Colin — 2023-12-10 <p>Cities are aggregates of human activities where our decisions shape the environment creating heterogeneity across urban centers that can have significant ecological effects on wildlife. Many bird species are found in cities during the breeding season, which implies they find sufficient resources in cities to support them during this energetically costly time. As populations of many migratory bird species are declining, knowledge of how they are affected by urbanization is needed. Yet, we know little about how the species richness of migratory birds varies across different types of cities. Here we ask if cities' structural and socioeconomic features can predict the species richness of migratory birds that generally select different breeding habitats during the breeding season. We used eBird data from census-designated urban areas in the United States to model the relationship between features of cities (housing density, median income, city age, and commuting time), environmental disturbance (measured by the human footprint index) and species richness by fitting generalized linear models to data. We show that commuting time was the most important factor determining species richness across cities and the rest of the city features were weakly associated with species richness. Overall species were responding to city variation in similar ways.  While we expected that cities with more disturbance would have lower species richness, our results indicate that some species are able to tolerate even highly disturbed cities and that cities in certain regions may act as a refuge to birds. This knowledge is important for our general understanding of cities as habitat for birds and how migratory birds respond to across-city variation during the breeding season.</p>
Dryad Logo
Determinants of genetic diversity and species richness of North American amphibians
Dryad
Schmidt, Chloé; Munshi-South, Jason; Dray, Stéphane; Garroway, Colin J. — 2022-08-11 <p><strong>Aim:</strong> Ecological limits on population sizes and the number of species a region can sustain are thought to simultaneously produce spatial patterns in population genetic diversity and species richness due to the effects of random drift operating in parallel across population and community levels. Here, we test the extent to which resource-based environmental limits jointly determine these patterns of biodiversity in amphibians.</p> <p><strong>Location:</strong> North America.</p> <p><strong>Taxon:</strong> Amphibians.</p> <p><strong>Methods:</strong> We repurposed open, raw microsatellite data from 19 species sampled at 554 sites in North America and mapped nuclear genetic diversity at the continental scale. We then tested whether ecological limits defined by resource availability and environmental heterogeneity could simultaneously shape biogeographic patterns in genetic diversity and species richness with structural equation modeling.</p> <p><strong>Results:</strong> Spatial patterns of population genetic diversity run opposite patterns of species richness and genetic differentiation. However, while measures of resource availability and niche heterogeneity predict 89% of the variation in species richness, these landscape metrics were poor predictors of genetic diversity.</p> <p><strong>Main conclusions:</strong> Although heterogeneity appears to be an important driver of genetic and species biodiversity patterns in amphibians, variation in genetic diversity both within and across species makes it difficult to infer general processes producing spatial patterns of amphibian genetic diversity. This result differs from those found in endotherms and may be due to the considerable life history variation found across amphibians.</p>
Dryad Logo
Genetic and species-level biodiversity patterns are linked by demography and ecological opportunity
Dryad
Schmidt, Chloé; Dray, Stéphane; Garroway, Colin J — 2022-03-28 <p>The processes that give rise to species richness gradients are not well understood, but may be linked to resource-based limits on the number of species a region can support. Ecological limits placed on regional species richness should also affect population demography, suggesting that these processes could also generate genetic diversity gradients. If true, we might better understand how broad-scale biodiversity patterns are formed by identifying the common causes of genetic diversity and species richness. We develop a hypothetical framework based on the consequences of regional variation in ecological limits set by resource availability and heterogeneity to simultaneously explain spatial patterns of species richness and neutral genetic diversity. Repurposing raw genotypic data spanning 38 mammal species sampled across 801 sites in North America, we show that estimates of genome-wide genetic diversity and species richness share spatial structure. Notably, species richness hotspots tend to harbor lower levels of within-species genetic variation. A structural equation model encompassing eco-evolutionary processes related to resource availability, habitat heterogeneity, and contemporary human disturbance supports the spatial patterns we detect. These results suggest broad-scale patterns of species richness and genetic diversity could both partly be caused by intraspecific demographic and evolutionary processes acting simultaneously across species.</p>

Map search instructions

1.Turn on the map filter by clicking the “Limit by map area” toggle.
2.Move the map to display your area of interest. Holding the shift key and clicking to draw a box allows for zooming in on a specific area. Search results change as the map moves.
3.Access a record by clicking on an item in the search results or by clicking on a location pin and the linked record title.
Note: Clusters are intended to provide a visual preview of data location. Because there is a maximum of 50 records displayed on the map, they may not be a completely accurate reflection of the total number of search results.

(Author: Schmidt, Chloé)

Limit by:

Clear all

to