Presented at the Bristol Conservation & Science Foundation 4th Annual Symposium December 2011


Seed dispersal is a pivotal ecological process, underpinning the ecology of terrestrial ecosystems and having a significant impact on forest structure and dynamics. In the tropics, up to 90% of seeds are dispersed by fruit-eating animals, whose behaviour greatly influences seed distribution – for example, dispersal distance depends upon ranging behaviour and activity patterns. Primates are important seed dispersers throughout the tropics, but are particularly crucial on Madagascar, where lemurs have the greatest biomass and species richness of frugivores on the island, and many other seed-dispersing taxa are absent. A previous study on lemur seed dispersal (Moses & Semple 2011) had noted relatively low dispersal distances by lemurs. This study aimed to test the hypothesis that seed dispersal by lemurs occurs over relatively shorter distances in comparison to other primates elsewhere in the tropics. Though only limited dispersal distance data are available (for two lemur species, six New World primate species and three Old World primate species), statistical analysis indicates that seed dispersal by lemurs occurs over significantly shorter distances than seed dispersal by other primate species. This finding supports the hypothesis that seed dispersal on Madagascar is ‘spatially restricted’. Possible explanations are that, just as the present-day lemur assemblage represents the vestiges of a once-broader diversity, seed dispersal may also have become restricted with the extinction of the largest-bodied lemurs. An alternative explanation is that prevalent lemur energy conservation strategies, hypothesised to have evolved in response to the low fruit productivity and high unpredictability of resources that characterise Madagascar’s forests, are incompatible with long dispersal distances. Two scenarios are presented for how limited seed dispersal by lemurs and fruiting phenology on Madagascar may be related. Furthermore, restricted dispersal processes may be one of the many driving mechanisms influencing the development of local endemism in Madagascar.

Poster format

(Here’s a pdf version: spatially-restricted-dispersal-poster_psgb-winter-2011-pdf.pdf_)

Spatially restricted dispersal