Population structure is not a simple function of reproductive mode and larval type: insights from tropical corals
Miller, KJ and Ayre, DJ, Population structure is not a simple function of reproductive mode and larval type: insights from tropical corals, Journal of Animal Ecology, 77, (4) pp. 713-724. ISSN 0021-8790 (2008) [Refereed Article]
For a wide range of organisms, heritable variation in life-history characteristics has been shown
to be strongly subject to selection, reflecting the impact that variation in characters such as genotypic
diversity, duration of larval development and adaptations for dispersal can have on the fitness
of offspring and the make-up of populations. Indeed, variation in life-history characteristics,
especially reproduction and larval type, have often been used to predict patterns of dispersal and
resultant population structures in marine invertebrates.
Scleractinian corals are excellent models with which to test this relationship, as they exhibit
almost every possible combination of reproductive mode and larval type. Some general patterns are
emerging but, contrary to expectations, genetic data suggest that while populations of broadcast
spawning species may be genotypically diverse they may be heavily reliant on localized recruitment
rather than widespread dispersal of larvae.
Here we use microsatellites to test the importance of localized recruitment by comparing the genetic
structure of populations of two broadcast spawning corals with contrasting modes of reproduction
and larval development;
is self-compatible, has sticky, negatively buoyant eggs and
larvae and is expected to have restricted dispersal of gametes and larvae. In contrast,
is self-incompatibile, spawns positively buoyant egg-sperm bundles and has planktonic development.
Surprisingly, spatial-autocorrelation revealed no fine-scale clustering of similar genotypes within
, but showed a non-random distribution of genotypes in
. Both species
showed similar levels of genetic subdivision among sites separated by 50100 m (
suggesting that larval dispersal may be equivalent in both species.
Interestingly, as fragmentation has been considered rare in massive corals, our sample of 284
colonies included 28 replicated genotypes that were each unlikely (
0·05) to have
been derived independently from sexual reproduction.
We conclude that the extreme life history of
does not produce unusually fine-scale
genetic structure and subsequently, that reproductive mode and larval type may not be not good
predictors of population structure or dispersal ability.
microsatellite DNA population genetics sexual and asexual reproduction spatial autocorrelation larval dispersal