Considering connectivity for multiple species at multiple scales in East Africa

Background/Question/Methods

Conserving connectivity among protected areas is challenging when attempted for multiple species, and its relative importance should be considered carefully with respect to other conservation goals such as preserving core habitat. At larger scales (long effective distances between core populations), connectivity may be irrelevant from a demographic or genetic perspective. Over shorter effective distances, gene flow may occur, and at the finest scales, migration or regular dispersal may affect local population dynamics. However, effective distances among protected areas depend on both the dispersal capability of species and their ability to persist outside of protected areas. We used a combination of field survey data collected on walking transects conducted in and among three protected areas and population genetic data collected in as many as nine protected areas to determine relevant scales for connectivity conservation for multiple species of large herbivores in Tanzania, East Africa. We also contrasted spatial and temporal scales of inference from both types of data.

Results/Conclusions

The relationship of genetic structure with distance or effective distance among core populations varied widely among species with different dispersal abilities, demonstrating that relevant scales for connectivity conservation also vary widely even for large herbivores. Field detections of different species in potential linkages among protected areas also reflected species-specific responses, in this case to current landscape processes (e.g., human population density) and habitat differences. Conclusions from field surveys were limited in scope due to logistic constraints on widespread sampling and sometimes confounded by correlation between human activity and habitat type. Population genetic estimates of gene flow reflected longer term processes on the landscape, specifically, the effect of habitat variation and biogeographic barriers, but did not strongly reflect recent landscape changes. Optimizing models of landscape connectivity for conservation planning should consider both data sources to make the strongest inferences over wide spatial scales. Explicit consideration of scale should help define importance of linkage conservation relative to other conservation goals.