The heterogeneity-biodiversity relationship across taxa and ecosystems

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Environmental heterogeneity is defined as the spatial and temporal change in resource or structure within a given area. The heterogeneity-diversity hypothesis is a classic of ecology, to the degree that it has become commonplace for conservationists to plead the positive relationship when emphasizing the importance of preserving or restoring different habitat types. However, recent theory and observation suggest that the relationship can be positive, flat, or even negative, depending on the ecological context. While plant and animal diversity intuitively depend on environmental heterogeneity at the landscape-scale, it is unclear whether the relationship generalizes the stand-scale. An alternative view is that the heterogeneity-diversity relationship vanishes and may even be reversed (diversity begets heterogeneity) at the stand-scale. Pioneer work as well as more recent studies have systematically considered one relationship direction; that heterogeneity begets diversity. The question of how plant diversity determines environmental heterogeneity at the stand-scale has, so far, been overlooked. To generalize the heterogeneity-diversity relationship, I propose studying it for two animal groups (open-field orthopterans and forest birds) in eight ecosystems along a gradient of climatic/edaphic conditions. Environmental heterogeneity will be measured using both direct field methods and indirect close-range photographic protocols. Animal communities will be described in terms of species and functional guild richness, as well as through digital recordings. On the method side, we will develop rapid photographic descriptors of plant architecture and light interception patterns, as well as acoustic descriptors of species and functional richness in vocalizing animal groups. On the conceptual side, we will work with worldwide distributed model organisms (birds and orthopterans) that are implicated in trophic transfer and bioregulation processes. The proposed framework bridges the sub-disciplines of landscape ecology, eco-acoustics and community ecology. Generalizing the heterogeneity-diversity relationship across taxa and ecosystems is an important step towards more informed policies for biodiversity conservation. Our work will address questions frequently asked by stakeholders: At what scales should we manage habitats for biodiversity, or is there a level of environmental heterogeneity beyond which biodiversity is expected to saturate? This research program will form new generation of biologists that can use and develop tools for monitoring plant and animal communities at high resolution in space and time.