Island isolation and habitat heterogeneity correlate with DNA variation in a marine snail (Littorina saxatilis)
Johannesson, K.; Lundberg, J.; André, C.; Nilsson, P.G. (2004). Island isolation and habitat heterogeneity correlate with DNA variation in a marine snail (Littorina saxatilis). Biol. J. Linn. Soc. 82(3): 377-384. https://dx.doi.org/10.1111/j.1095-8312.2004.00365.x
In: Biological Journal of the Linnean Society. Academic Press: London; New York. ISSN 0024-4066; e-ISSN 1095-8312, more
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| Keywords |
Littorina saxatilis (Olivi, 1792) [WoRMS]
Marine/Coastal |
| Authors | | Top |
- Johannesson, K.
- Lundberg, J.
- André, C.
- Nilsson, P.G.
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| Abstract |
The null assumption of molecular variation is that most of it is neutral to natural selection. This is in contrast to variation in morphological traits that we generally assume is maintained by selection, and therefore often by selection coupled to environmental heterogeneity in time and space. Examples of molecular variation that vary over habitat-shifts, particularly in allozymes, show that the relative impact of non-neutral variation as compared to neutral variation might be substantial in some systems. To assess the importance of habitat-generated variation in relation to variation generated by random processes in nuclear DNA markers at small spatial scales, we compared the effects of island isolation and habitat heterogeneity on genetic substructuring in a rocky shore snail (Littorina saxatilis). This species has a restricted migration among islands owing to the lack of free-floating larvae. Earlier studies show that allozymes vary extensively as a consequence of isolation by water barriers among islands, but also as a consequence of divergent selection among different microhabitats within islands. In the DNA markers we observed genetic differentiation owing to island isolation at three of nine loci. In addition, variation at three loci correlated with habitat type, but the correlation for two of the loci was weak. Overall, isolation contributed slightly more to the genetic variation among populations than did habitat-related factors but the difference was small. It is concluded that both island isolation, which interrupts gene flow, and a heterogeneous habitat cause genetic substructuring at the DNA level in L. saxatilis in the studied area, and thus in this species we need to be somewhat concerned about habitat heterogeneity also at DNA loci. |
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