Seed dispersal syndromes in the Madagascan flora: the unusual importance of primates

Abstract

Madagascar is one of the most threatened biodiversity hotspots, and protection of its biodiversity is becoming increasingly urgent as deforestation of the island continues. For the long-term success of conservation efforts it is essential that key ecological processes, such as seed dispersal, are protected and restored. Therefore, the identification of ecological gaps is a vital task. For Madagascar, only little is known about plant–animal interactions, and traditional methods of ecological research are too time-consuming to provide crucial information about breakdowns in these interactions. To identify likely dispersal gaps we therefore used a theoretical approach to analyse plant–disperser interactions in Madagascar. We used data science tools to impute missing data on relevant plant traits to subsequently predict the most likely dispersal agents for each of Madagascar's endemic plant species. We found that 38% of the endemic species (N = 8,784) are endozoochorous, and among these 26–41% display a primate syndrome and 17–19% a bird syndrome (depending on the definition of syndromes). This lower percentage of endozoochorous species and higher percentage of species with a primate syndrome in Madagascar compared to other tropical areas reflects the unusual disperser guild on the island. Only five bird species but 20 lemur species are frugivorous, and 16 of those lemur species are currently threatened with extinction. The disappearance of frugivorous lemurs would significantly change the vegetation dynamics of Madagascar's ecosystems, and a high proportion of Madagascar's endemic plants would enter an extinction vortex.

Multiple External Seed Dispersers Challenge the Megafaunal Syndrome Anachronism and the Surrogate Ecological Function of Livestock

“…Figures 4B,C), a primate, a squirrel and a corvid species. This highlight how particular animal groups, traditionally neglected as reliable seed dispersers, can promote a crucial mutualistic role for palms and other large-fruited plants (Jansen et al, 2012;Blanco et al, 2015Blanco et al, , 2018Montesinos-Navarro et al, 2017;Albert-Daviaud et al, 2018).…”

Strontium Isotopes Support Small Home Ranges for Extinct Lemurs

“…What is less clear is the extent to which large, fruit-bearing trees and their seed dispersers were better represented in the recent past, the degree to which they face disproportionate extinction risk in the future, and the degree to which that risk depends on the survival of primates. Although Madagascar today has an unusually low number of plant species that disperse their seeds via endozoochory, most of those that do rely on endozoochory have adaptations to attract primates rather than birds (Albert-Daviaud et al, 2018). This is particularly the case for trees with large seeds (Razafindratsima et al, 2018).…”

“…When seed dispersers have limited home ranges, the plant community as a whole may be more vulnerable to habitat disturbance, and therefore at greater risk of entering into an extinction vortex. The problem is not merely that the loss of key seed dispersers may result in an increase in the number of "orphaned" plants (those lacking seed dispersers; Bollen et al, 2004;Godfrey et al, 2008;Crowley et al, 2011;Buerki et al, 2015;Albert-Daviaud et al, 2018), but also that the plant species most likely to become orphaned are the trees with the highest above-ground biomass, and therefore the greatest capacity to store carbon. They are precisely the trees that contribute the most to climate stability and the health of the entire ecosystem (Razafindratsima et al, 2018).…”

Conservation genomic analysis reveals ancient introgression and declining levels of genetic diversity in Madagascar’s hibernating dwarf lemurs

“…Madagascar’s biota is not only largely endemic but also highly diverse (Goodman and Bernstead 2007). The unique geological and evolutionary history of the island, combined with the contemporary degradation of habitats, has led to an urgent need to understand both their evolutionary history and the ecological interactions between lemurs and the ecosystems in which they occur (Albert-Daviaud et al 2018). For example, quaternary climatic variation created periods of glaciation worldwide that resulted in cooler and more arid climates at lower elevations in Madagascar, whereas periods of glacial minima resulted in warmer and more humid climates (Rakotoarinivo et al 2013).…”