MORPHOLOGICAL VARIABILITY OF HOLOCENE CANARIUM FOSSIL ENDOCARPS FROM MADAGASCAR

Many plants rely on animal dispersers to eat fruit and spread seeds via feces; this process helps plants colonize new areas and maintain ranges by reducing competition, increasing gene flow, and facilitating successful germination. On the island of Madagascar, the large-seeded genus Canarium is thought to have been dispersed by large-bodied lemurs that since went extinct ~500-2000 years ago. After large disperser loss, some plants may evolve smaller seeds to ensure viable dispersal from smaller extant animals, but these adaptations have never been witnessed directly in the fossil record. Fossils of Canarium endocarps from Ampiriaka, Madagascar, (18°56'S, 46°38’E) can act as proxies for seeds and allow us to study trait change before and after disperser extinction. Fossils at this site are early to mid-Holocene in age and found in situ with extinct lemur fossils, and thus pre-date Holocene lemur extinction.

In order to constrain morphological variability typical for this genus, we present 3D morphometric analyses from micro-CT scans of 20 radiocarbon-dated fossil Canarium endocarps. Preliminary work suggests little morphological variation among fossils of varying ages. Our results help constrain the variability in Canarium endocarp morphology in the time frame before large lemur extinction, improving our ability to identify true morphological change across the extinction interval. Studying endocarp size adaptations after disperser loss can help us prioritize resources for large-seeded species that have not or cannot adapt smaller seeds to target smaller dispersers. As defaunation of large animals continues in the present-day worldwide, it is essential to understand the consequences to co-evolved species, such as plants, and how they may adapt.