Biogeographical patterns in liana abundance and diversity

Abstract

Liana abundance and species diversity are higher in tropical than temperate forests, but substantial variation exists in liana community structure within tropical forests, among biogeographical regions, and along gradients in altitude, precipitation, and edaphic characteristics. Liana surveys from across the world compiled into the Global Liana Database (GLD) allowed examination of patterns in liana abundance and diversity among continents, between islands and continental regions, and in relation to mean annual precipitation and dry season length, which could be strong predictors of liana community structure. Sites in the GLD span a rainfall gradient of 850 − 7000 mm/yr and 0 − 7 dry months. The GLD presents an alternative to the global dataset of 0.1 ha transects Alwyn Gentry compiled in the 1980s and 1990s. Using the GLD, we find that neotropical and African forests have almost two-times greater liana density than forests in Asia, and that African liana diversity is 50% greater than sites in South America and 130% greater than sites in Central America and Asia, after accounting for climatic conditions. Within each biogeographical region, liana density declines with increasing mean annual precipitation and increases with seasonality in precipitation. Liana diversity, in contrast, shows a hump-shaped relationship with mean annual precipitation and no relationship with dry season length. Differences in liana density and diversity among biogeographical regions in the GLD mirror those found in Gentry?s global dataset, but patterns in relation to mean annual precipitation and dry season length did not. It is not yet clear why the relationships between these climatic variables and liana diversity and density differ between the two datasets. Documentation of biogeographical patterns in liana abundance and diversity provides a basis for the generation of hypotheses about the drivers of liana proliferation and speciation.