Implications of life history for genetic structure and migration rates of southern African coastal invertebrates: planktonic,abbreviated and direct development |
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| Authors: | P R Teske I Papadopoulos G I Zardi C D McQuaid M T Edkins C L Griffiths N P Barker |
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| Institution: | (1) Department of Zoology and Entomology, Rhodes University, Grahamstown, 6140, South Africa;(2) Molecular Ecology and Systematics Group, Botany Department, Rhodes University, Grahamstown, 6140, South Africa;(3) Zoology Department, Nelson Mandela Metropolitan University, P.O. Box 7700, Port Elizabeth, 6031, South Africa;(4) Zoology Department, University of Cape Town, Rondebosch, 7701, South Africa |
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| Abstract: | The amount of genetic structure in marine invertebrates is often thought to be negatively correlated with larval duration.
However, larval retention may increase genetic structure in species with long-lived planktonic larvae, and rafting provides
a means of dispersal for species that lack a larval dispersal phase. We compared genetic structure, demographic histories
and levels of gene flow of regional lineages (in most cases defined by biogeographic region) of five southern African coastal
invertebrates with three main types of larval development: (1) dispersal by long-lived planktonic larvae (mudprawn Upogebia africana and brown mussel Perna perna), (2) abbreviated larval development (crown crab Hymenosoma orbiculare) and (3) direct development (estuarine isopod Exosphaeroma hylecoetes and estuarine cumacean Iphinoe truncata). We hypothesized that H. orbiculare, having abbreviated larval development, would employ a strategy of larval retention, resulting in genetic structure comparable
to that of the direct developers rather than the planktonic dispersers. However, regional population structure was significantly
lower in all species with planktonic larvae, including H. orbiculare, than in the direct developers. Moreover, nested clade analysis identified demographic histories resulting from low levels
of gene flow (isolation by distance and allopatric fragmentation) in the direct developers only, and migration rates were
significantly higher in all three species having planktonic larvae than in the direct developers. We conclude that the amount
of genetic structure within marine biogeographic regions strongly depends on the presence or absence of free-swimming larvae.
Whether such larvae are primarily exported or retained, whether they have long or short larval duration, and whether or not
they are capable of active dispersal seems to have little effect on connectivity among populations. |
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