Journal of Heredity Advance Access published online on December 16, 2008
Journal of Heredity, doi:10.1093/jhered/esn107
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The Comparative Phylogeography of East Coast Estuarine Fishes in Formerly Glaciated Sites: Persistence versus Recolonization in Cyprinodon variegatus ovinus and Fundulus heteroclitus macrolepidotus
From the Department of Ecology and Evolutionary Biology, Box G-W, Brown University, Providence, RI 02912 (Haney and Rand); the Wells National Estuarine Research Reserve, 342 Laudholm Farm Road, Wells, ME 04090 (Dionne); the Department of Zoology, University of Hawai'i at Manoa, 2538 McCarthy Mall, Edmondson 152, Honolulu, HI 96822 (Puritz); and the Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637 (Haney)
Address correspondence to Robert A. Haney at the address above, e-mail: robert.a.haney{at}gmail.com.
Species distributions may be dramatically affected by climatic variability, such as occurred during Pleistocene glaciation. Populations of coastal organisms could have been affected directly by ice movement or through sea level change. Response could involve shifts in distribution southwards or persistence through the full range or in limited high-latitude refugia. Comparative studies of the response of ecologically similar species can provide a useful complement to those examining response across disparate species in defining what parameters influence persistence. Patterns of mitochondrial genetic variation in 2 estuarine fish subspecies from the Northwest Atlantic, Fundulus heteroclitus macrolepidotus and Cyprinodon variegatus ovinus, indicate that ecological similarity does not necessarily predict propensity for glacial persistence. Fundulus heteroclitus macrolepidotus is highly diverse in glaciated regions, with isolated populations whose origins predate the last glacial maximum and may have recently expanded it's range to the south from New England. However, within glaciated regions, signals of population growth and distributional shifts indicate a dynamic Pleistocene history for F. h. macrolepidotus, in contrast with recent studies involving microsatellites. A different pattern is found in C. v. ovinus, which is depauperate in formerly glaciated sites, with a clear signal of recent recolonization of glaciated regions from the south. Genetic differentiation in glaciated areas is consistent with isolation after glacial withdrawal. In C. v. ovinus, rapidly evolving microsatellite loci show a similar pattern to mitochondrial DNA but may be reaching equilibrium on small spatial scales. These contrasting patterns of variation illustrate how ecologically similar species can respond to large-scale environmental change in distinct ways.
Key Words: Cyprinodon • Fundulus • glaciation • mitochondrial • phylogeography
Corresponding Editor: Adalgisa Caccone
Received June 4, 2008
Revised November 2, 2008
Accepted November 18, 2008