Sacha Spector

Remote sensing for biodiversity science and conservation

Remote-sensing systems typically produce imagery that averages information over tens or even hundreds of square meters – far too coarse to detect most organisms – so the remote sensing of biodiversity would appear to be a fool’s errand. However, advances in the spatial and spectral resolutions of sensors now available to ecologists are making the direct remote sensing of certain aspects of biodiversity increasingly feasible; for example, distinguishing species assemblages or even identifying species of individual trees. In cases where direct detection of individual organisms or assemblages is still beyond our grasp, indirect approaches offer valuable information about diversity patterns. Such approaches derive meaningful environmental parameters from biophysical characteristics that

Elevational Distribution and Conservation Biogeography of Phanaeine Dung Beetles (Coleoptera: Scarabaeinae) in Bolivia

Insect macroecology and conservation biogeography studies are disproportionately scarce, especially in the Neotropics. Dung beetles are an ideal focal taxon for biodiversity research and conservation. Using distribution and body size data on the ecologically important Phanaeini, the best-known Neotropical dung beetle tribe, we determined elevational patterns of species richness, endemism, body size, and elevational range in Bolivia, specifically testing Bergmann’s and Rapoport’s rule. Richness of all 39 species and of 15 ecoregional endemics showed a hump-shaped pattern peaking at 400 m, but overall declined strongly with elevation up to 4000 m. The relationship between endemic and total species richness appeared to be curvilinear, providing only partial support for the null hypothesis that species-rich areas are more likely to be centers of endemism by chance alone. An elevational increase in the proportion of ecoregional endemics suggests that deterministic factors also appear to influence endemism in the Andes. When controlling for the effect of area using different species-area relationships, the statistically significant richness peak became more pronounced and shifted upslope to 750 m. Larger species did not have higher elevational mid-points, and mean body size decreased significantly with elevation, contradicting Bergmann’s rule. Rapoport’s rule was supported: species with higher elevational mid-points had broader elevational ranges, and mean elevational range increased significantly with elevation. The elevational decrease of phanaeine richness is in accordance with studies that demonstrated the combined influence of temperature and water availability on species diversity, but also is consistent with niche conservatism. For invertebrates, confirmation of Rapoport’s and refutation of Bergmann’s rule appear to be scale-invariant general patterns. Analyses of biogeographic patterns across elevational gradients can provide important insights for identifying conservation priorities. Phanaeines with narrow elevational ranges on isolated low-elevation mountains in eastern Bolivia are at greatest climate-change related extinction risk from range-shift gaps and mountaintop extinctions.

Simulating the Effects of Sea Level Rise on the Resilience and Migration of Tidal Wetlands along the Hudson River

Sea Level Rise (SLR) caused by climate change is impacting coastal wetlands around the globe. Due to their distinctive biophysical characteristics and unique plant communities, freshwater tidal wetlands are expected to exhibit a different response to SLR as compared with the better studied salt marshes. In this study we employed the Sea Level Affecting Marshes Model (SLAMM), which simulates regional- or local-scale changes in tidal wetland habitats in response to SLR, and adapted it for application in a freshwater-dominated tidal river system, the Hudson River Estuary. Using regionally-specific estimated ranges of SLR and accretion rates, we produced simulations for a spectrum of possible future wetland distributions and quantified the projected wetland resilience, migration or loss in the HRE through the end of the 21st century. Projections of total wetland extent and migration were more strongly determined by the rate of SLR than the rate of accretion. Surprisingly, an increase in net tidal wetland area was projected under all scenarios, with newly-formed tidal wetlands expected to comprise at least 33% of the HRE’s wetland area by year 2100. Model simulations with high rates of SLR and/or low rates of accretion resulted in broad shifts in wetland composition with widespread conversion of high marsh habitat to low marsh, tidal flat or permanent inundation. Wetland expansion and resilience were not equally distributed through the estuary, with just three of 48 primary wetland areas encompassing >50% of projected new wetland by the year 2100. Our results open an avenue for improving predictive models of the response of freshwater tidal wetlands to sea level rise, and broadly inform the planning of conservation measures of this critical resource in the Hudson River Estuary.

Biogeographic patterns and conservation priorities for the dung beetle tribe Phanaeini (Coleoptera: Scarabaeidae: Scarabaeinae) in Bolivia

The New World Phanaeini are the best known Neotropical dung beetle tribe and a conservation priority among the Scarabaeinae, an ideal focal taxon for biodiversity research and conservation. We compiled a comprehensive distributional database for 39 phanaeine species in Bolivia and assessed patterns of species richness, body size and endemism in relation to abiotic variables and species richness and body mass of medium to large mammals across nine ecoregions. Pair‐wise linear regressions indicated that phanaeine richness, mean size and endemism are determined by different factors. In all cases mammal body mass had greater explanatory power than abiotic variables or mammal richness. Phanaeine richness was greater in ecoregions with on average smaller mammals and greater mammal richness. Mean phanaeine size increased with mean body mass of the largest herbivorous and omnivorous mammals. Endemism was greater in ecoregions with on average smaller herbivorous and omnivorous mammals. On average, smaller phanaeines had more restricted distributions than larger species; ecoregional endemism and mean body size were negatively correlated. Large phanaeines probably depend on large mammals to provide adequate food resources. Greater richness of smaller mammal species may allow for greater temporal and spatial resource partitioning and therefore greater phanaeine species richness. Low numbers of large mammal species may favour the persistence of geographically restricted phanaeine species by reducing interspecific competition with larger, more geographically widespread and presumably dominant phanaeines. Cerrado, Southwest Amazonia and Yungas are priority ecoregions for phanaeine conservation due to high total and endemic species richness.