Contrasting patterns of genetic diversity between two endangered palms with overlapping distributions, Voanioala gerardii (Arecoideae) and Lemurophoenix halleuxii (Arecoideae), from North-east Madagascar

Abstract

Madagascar has a high diversity of endemic palm species and the Masoala Peninsula is a hotspot for their diversity. Several species are critically endangered and their populations known to be in decline due to a combination of land clearance, destructive harvesting for heart of palm and potentially unsustainable commercial seed collection. The critically endangered Voanioala gerardii and the endangered Lemurophoenix halleuxii are two palm species from monospecific genera endemic to Madagascar that overlap in their distribution within this region. This project undertook field surveys of all known populations of these two species to document their population sizes and locations. We modelled their area of potentially suitable habitat within the region and undertook genetic analysis to investigate genetic diversity and relatedness among populations of each species. The study found overlapping but contrasting patterns of potential habitat. It also found contrasting levels and patterns of genetic diversity between the two species that were not consistent with the modelled habitat distributions. We found that Voanioala gerardii populations are critically small but contain unexpectedly high levels of genetic diversity, which may indicate as yet undiscovered populations remaining. An active program to change methods of seed collection and to involve local villagers and land managers in the conservation of these species would be required to prevent their extinction.