The Ghost Fruits of Madagascar: Identifying Dysfunctional Seed Dispersal in Madagascar's Endemic Flora

Document Type

Article

Publication Date

2-2020

Abstract

Madagascar lost a large number of large-bodied animal species during the Holocene. Many of them played important roles as seed dispersers. In the case of the largest-seeded species, giant lemurs or elephant birds may have been the sole dispersers because no extant frugivore has a gape size large enough to ingest those seeds. These plant species now show all the hallmarks of anachronistic species. The consequences of dispersal gaps caused by megafaunal extinctions are exacerbated by the continuing decline of the range distribution of extant dispersers, particularly lemurs. In this paper, we identify dispersal gaps in Madagascar and highlight dysfunctional seed dispersal – systems in which plants have lost animal mutualists. We obtained data on seed dispersal, traits and distribution of plants and frugivores in Madagascar from the literature, online databases, and using herbarium specimens. We estimated the number of potential dispersers for each endemic endozoochorous plant species, by comparing the seed size of each plant species to the size of the largest seed that each frugivore can swallow whole. We estimated the number of available lemur dispersers by matching the distribution of plant species to the distribution of potential dispersers. We found that, out of the 3018 studied endozoochorous plant species, two species have experienced the complete extinction of their main dispersers while 487 species suffer from the local extinction of their suitable dispersers. A limited number of dispersers could be one of the main reasons why most of these plant species are now on the edge of extinction.

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