Extinctions, traits and phylogenetic community structure: insights from primate assemblages in Madagascar

Understanding the origin and maintenance of community composition through ecological and evolutionary time has been a central challenge in ecology. However little is known about how extinction may alter patterns of phylogenetic and phenotypic structure within communities. To address this, we used past and present primate communities in Madagascar as our model system to explore how a large extinction event within a taxon may alter evolutionary relationships and phenotypic distributions within communities. We also explored the influence of environment on the structure of present-day lemur communities. We found a phylogenetic pattern of overdispersion in both past and present-day communities. However, trait structures, including relative dispersion of body masses and trophic niches were altered following extinction. We posit that the overdispersed phylogenetic patterns have resulted from the unique ecological and evolutionary history of Madagascar's primates including a rapid adaptive radiation in the presence of a broad niche-space available during colonization. Differences in trait structures between present and past primate communities may be reflective of the selective extinction process that eliminated the largest primates from the island. Habitat also appeared to influence the structure of present-day lemur communities. Lower divergence in patterns of phylogeny, body mass and activity rhythms were found in dry relative to wet habitats. This may be due to potential advantages of being small and nocturnal in environments with low productivity and hot dry climates. We suggest current studies exploring community processes should consider potential effects of past extinction events. Such work is important for understanding community assembly, coexistence, and mechanisms driving extinctions, particularly given the current extinction crisis facing ecosystems globally.