Niche occupancy of Jamaican bat caves: Diversity increases isotopic niche packing.

There are over 1000 documented caves across Jamaica, many of them used by diverse communities of bats. Species across these communities fit within the same trophic guilds and families and can be found at the same sites, raising the question of how these species can coexist. We calculated mean isotopic niche breadth and overlap of the communities at these sites and used general linear models to test two hypotheses: in communities with greater species richness, (1) populations will be (a) more specialized and/or (b) overlap between populations will increase (sensu niche packing), or (2) community niche space will increase (sensu niche expansion). We found significant heterogeneity in niche breadth at the population level and significant heterogeneity in overlap across sites. Jamaican cave-roosting bat communities achieve coexistence through niche packing and not through niche expansion. We found support for niche packing through increasing overlap in some groups and no evidence for niche packing through specialization. More speciose sites had greater overlap among populations within the same cave and lower nearest neighbour distance, suggesting packing within the community niche space. Our results demonstrate niche packing as the operative mechanism of coexistence among diverse Jamaican bat caves.