Data from: Back from the brink: potential for genetic rescue in a critically endangered tree

Rare plant species are vulnerable to genetic erosion and inbreeding
associated with small population size and isolation due to increasing
fragmentation, though the degree to which these problems undermine
population viability remains debated. We explore genetic and reproductive
processes in the critically endangered long-lived tropical tree Medusagyne
oppositifolia, an endemic to the Seychelles with a naturally patchy
distribution. This species is failing to recruit in three of its four
populations. We evaluate whether recruitment failure is linked to genetic
problems associated with fragmentation, and if genetic rescue can mitigate
such problems. Medusagyne oppositifolia comprises 90 extant trees in four
populations, with only the largest (78 trees) having successful
recruitment. Using 10 microsatellite loci we demonstrated that genetic
diversity is high (HE: 0.48 – 0.63; HO: 0.56 – 0.78) in three populations,
with only the smallest population having relatively low diversity (HE:
0.26 and HO: 0.30). All populations have unique alleles, high genetic
differentiation, and significant within population structure. Pollen and
seed dispersal distances were mostly less than 100 m. Individuals in small
populations were more related than individuals in the large population,
thus inbreeding might explain recruitment failure in small populations.
Indeed, inter-population pollination crosses from the large donor
population to a small recipient population resulted in higher reproductive
success relative to within-population crosses. Our study highlights the
importance of maintaining gene flow between populations even in species
that have naturally patchy distributions. We demonstrate the potential for
genetic and ecological rescue to support conservation of plant species
with limited gene flow.