Parentage analyses identify local dispersal events and sibling aggregations in a natural population of Millepora hydrocorals, a free-spawning marine invertebrate

Dispersal is a critical process for the persistence and productivity of
marine populations. For many reef species, there is increasing evidence
that local demography and self-recruitment have major consequences on
their genetic diversity and adaptation to environmental change. Yet
empirical data of dispersal patterns in reef-building species remain
scarce. Here, we document the first genetic estimates of self-recruitment
and dispersal distances in a free-spawning marine invertebrate, the
hydrocoral Millepora platyphylla. Using twelve microsatellite
markers, we gathered genotypic information from 3,160 georeferenced
colonies collected over 9,000 m2 of a single reef in three
adjacent habitats in Moorea, French Polynesia; the mid slope, upper slope,
and back reef. Although the adult population was predominantly clonal (85%
were clones), our parentage analysis revealed a moderate self-recruitment
rate with 8 to 37% of sexual propagules produced locally. Assigned
offspring often settled at less than 10 meters from their parents and
dispersal events decrease with increasing geographic distance. There were
no discrepancies between the dispersal distances of offspring assigned to
parents belonging to clonal versus non-clonal
genotypes. Inter-habitat dispersal events via cross-reef transport were
also detected for sexual and asexual propagules. Sibship analysis showed
that full siblings recruit together on the reef (more than 40% settled at
< 30 m), resulting in sibling aggregations. Our findings highlight
the importance of self-recruitment together with clonality in stabilizing
population dynamics, which may ultimately enhance local sustainability and
resilience to disturbance.