Habitat loss causes non-linear genetic erosion in specialist species

Habitat loss can lead to non-linear declines in species abundance once the amount of landscape-wide habitat is reduced to a critical value. Previous studies have suggested that such non-linear responses to landscape-wide habitat loss might also exist in genetic variation, and an in-depth understanding of non-linear habitat loss effects on all levels of biodiversity levels is vital to take appropriate conservation actions.Using individual-based simulations we evaluated the existence of generic non-linear responses in three different response variables and across different combinations of traits related to dispersal and population density. We simulated habitat loss scenarios by incrementally reducing the landscape-wide habitat amount within a previously undisturbed landscape and monitored population abundance, genetic diversity and differentiation of populations within constant sampling areas over time. We found aside from population abundance, genetic variation also responded non-linearly to habitat loss across all scenarios. Importantly, the populations that persisted in remaining habitat fragments experienced genetic erosion before a noticeable effect on local abundance occurred. The observed increase in genetic differentiation and the decrease in genetic diversity of remaining populations are likely caused by the indirect effects of landscape-wide habitat loss on effective patch isolation. Thus, genetic data might have the potential to detect indirect effects of landscape-wide habitat loss before it directly affects the size of a population. Since indirect effects of habitat loss might go unnoticed when extinction risk is estimated from abundance data alone, we argue that an improved understanding of genetic effects is crucial to anticipate and ultimately prevent the negative effects of habitat loss. Keywords: Biodiversity, Extinction threshold, Habitat fragmentation, Population decline, Genetic diversity, Genetic structur

An objective approach to select surrogate species for connectivity conservation

International audienceIntroduction Connected landscapes can increase the effectiveness of protected areas by facilitating individual movement and gene flow between populations, thereby increasing the persistence of species even in fragmented habitats. Connectivity planning is often based on modeling connectivity for a limited number of species, i.e., “connectivity umbrellas”, which serve as surrogates for co-occurring species. Connectivity umbrellas are usually selected a priori , based on a few life history traits and often without evaluating other species. Methods We developed a quantitative method to identify connectivity umbrellas at multiple scales. We demonstrate the approach on the terrestrial large mammal community (24 species) in continental Europe at two scales: 13 geographic biomes and 36 ecoregions, and evaluate the interaction of landscape characteristics on the selection of connectivity umbrellas. Results We show that the number, identity, and attributes of connectivity umbrellas are sensitive to spatial scale and human influence on the landscape. Multiple species were selected as connectivity umbrellas in 92% of the geographic biomes (average of 4.15 species) and 83% of the ecoregions (average of 3.16 species). None of the 24 species evaluated is by itself an effective connectivity umbrella across its entire range. We identified significant interactions between species and landscape attributes. Species selected as connectivity umbrellas in regions with low human influence have higher mean body mass, larger home ranges, longer dispersal distances, smaller geographic ranges, occur at lower population densities, and are of higher conservation concern than connectivity umbrellas in more human-influenced regions. More species are required to meet connectivity targets in regions with high human influence (average of three species) in comparison to regions with low human influence (average of 1.67 species). Discussion We conclude that multiple species selected in relation to landscape scale and characteristics are essential to meet connectivity goals. Our approach enhances objectivity in selecting which and how many species are required for connectivity conservation and fosters well-informed decisions, that in turn benefit entire communities and ecosystems