Supporting code, tables and data for: Megafrugivores as fading shadows of the past: Extant frugivores and the abiotic environment as the most important determinants of the distribution of palms in Madagascar
- 1. German Center for Integrative Biodiversity Research
- 2. Aarhus University
- 3. Institute for Biodiversity and Ecosystem Dynamics (IBED)*
- 4. University of Antananarivo
The extinction of all Madagascar's megafrugivores ca. 1000 years ago, may have left its signature on the current distribution of vertebrate-dispersed plants across the island, due to the loss of effective seed dispersal. In this study, we dissect the roles of extinct and extant frugivore distributions, abiotic variables, human impact and spatial predictors on the compositional turnover, or beta-diversity, of palm (Arecaceae) species and their fruit sizes across 40 assemblages on Madagascar. Variation partitioning showed that palm beta-diversity is mostly shaped by the distribution of extant frugivores (8 lemur, 3 bird, 2 rodent and 1 bat species) and the abiotic environment (e.g., forest cover, slope and temperature), and to a lesser extent by the distribution of extinct frugivores (5 giant lemur and 3 elephant bird species). However, the contribution of these variables differed between dry western assemblages and wet eastern assemblages, with a more prominent role, albeit still small, of extinct megafrugivores in the west. These results suggest that palm distributions in the dry west of Madagascar, where megafrugivores were probably most abundant in the past, still show signatures of past interactions. With a fourth-corner analysis we observed that the distribution of palm species with relatively large fruits and seeds was negatively associated with home range of extant mammalian frugivores and frugivore richness of both past and extant communities, and positively associated with the hand-wing index (HWI) – a proxy for dispersal ability - of extant bird communities. This suggests that palm species with relatively large fruits tend to occur in places with fewer, small-ranged mammalian frugivores, which may indicate dysfunctional seed dispersal, although a few wide-ranging bird species may compensate this loss by dispersing the seeds of small-to medium-sized palm fruits. Our results shed new light on anachronisms in Madagascar, and how defaunation and past interactions may underlie current plant distributions.