Studies have shown that most new species arise from geographically, and therefore genetically, isolated populations. But some seahorses likely diversify in a process called sympatric speciation, in which new species arise from a single population that has no geographic barriers to inhibit gene flow, according to a paper published this week in the Proceedings of the National Academy of Sciences (PNAS).
We think theres a fairly strong case that sympatric speciation may have occurred in seahorses, said Georgia Institute of Technology Assistant Professor of Biology Adam Jones, the lead author on the PNAS paper. Were not arguing that all speciation in seahorses is sympatric. The majority of speciation is probably due to some geographic barrier to genetic migration. But in some instances it looks like sympatric speciation occurred.
Driving the sympatric speciation process in seahorses is the fishs size-similar mating practice imposed by male pregnancy, extended male parental care and monogamy, Jones said. Seahorses choose similar-size mates to have the best chances for successful reproduction. The female inserts ripe eggs into the males brood pouch, where the eggs are fertilized, embed and incubate for 10 days to six weeks, depending on the species.
Male reproductive rates, the size of the brood pouch and the number of eggs that a female produces all increase with the size of the seahorse, Jones explained. So if youre a large seahorse, you want to mate with another large seahorse so youre not wasting your eggs or your brood pouch space. So this kind of mating is the real mechanism for sympatric speciation. A lot of forms of parental care might not cause that size-specific restraint in mating, but this one does.
In addition to size-specific mating, a process
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Contact: Jane Sanders
jane.sanders@edi.gatech.edu
404-894-2214
Georgia Institute of Technology Research News
5-May-2003