Limited evidence of cloning and selfing within wild populations of coral-eating crown-of thorns seastar (Acanthaster cf. solaris)

Population outbreaks of crown-of-thorns seastars (CoTS; Acanthaster spp.)
are contributing to extensive coral loss and reef degradation throughout
the Indo west-Pacific, but the causes and underlying mechanisms of
population maintenance and outbreaks are equivocal. Two recent
publications suggest that, in addition to outbreeding sexual reproduction,
asexual reproduction through larval fission and selfing may contribute to
rapid increases in the local abundance of Acanthaster spp. We re-analysed
two large microsatellite datasets (collectively representing 3,714
individuals) that investigated connectivity in the Great Barrier Reef and
Pacific region to investigate if potential cloning or selfing can be
evidenced in the population genetic structure. Within this dataset we
identified only a small number (18, < 0.5%) of putative clones
(repeated multi locus genotypes). We argue that several of these are due
to sampling and processing errors rather than direct evidence of cloning.
Analysis of the population genetic structure (i.e., pairwise genetic
differences between individuals, deviations from
Hardy-Weinberg-Equilibrium, and linkage disequilibrium) also yielded no
genetic evidence for asexual reproduction. There was a tendency towards
slight heterozygote deficits, so we cannot refute that selfing does occur,
but this is mostly likely attributable to sampling artefacts. Although we
cannot exclude that asexual reproduction occurs to some extent in
Acanthaster populations, we find no evidence that these processes make
a contribution to population structure or directly enhance larval
supply.