Long-term genetic consequences of habitat fragmentation: A study of isozyme variation in the alpine plants; Carex bigelowii Torr., Diapensia lapponica L., and Minuartia groenlandica Retz.

摘要

This study uses habitats that have been naturally fragmented throughout the Holocene to examine the effects of habitat fragmentation on a much longer time scale. To investigate the long-term effects of habitat fragmentation on population genetic structure of Carex bigelowii, Diapensia lapponica , and Minuartia groenlandica, isozyme variation in fragmented patches of alpine tundra was compared to variation in sites from continuous alpine tundra.; The questions posed by this study include: Is genetic variation reduced in fragmented habitat? Does gene flow occur between habitat fragments? What is the effect of fragment size on genetic variation? Have populations from fragments diverged more than populations separated by a similar distance in continuous habitat?; Some of the results agree with the predictions of population genetic theory, and some do not. Dipensia lapponica and C. bigelowii have significantly less genetic variation in fragmented habitat. Contrary to theoretical predictions, M. groenlandica has significantly more genetic variation in fragmented habitat.; Gene flow between populations of D. lapponica and C. bigelowii in fragmented habitat appears to be absent or reduced compared to unfragmented habitat. Gene flow between populations of M. groenlandica does not seem to have been affected by the scale of habitat fragmentation in this study.; Correlation of genetic variation with fragment size is positive for C. bigelowii, not significant for D. lapponica and negative for M. groenlandica. Contrary to theoretical predictions, populations of M. groenlandica have significantly more genetic variation in small habitat patches than in large ones.; Populations of D. lapponica and C. bigelowii have diverged more in fragmented habitat than in unfragmented habitat, possibly as a result of genetic drift. Minuartia groenlandica populations have not diverged more in fragmented than in unfragmented habitat.; Diapensia lapponica, C. bigelowii, and M. groenlandica have virtually identical distributions in the northeast, and must have migrated into the region contemporaneously (on a geologic time scale) from southern refugia, yet have strikingly different patterns of genetic variation. This observation should serve as a cautionary note in attempts to infer past migration patterns from current patterns of genetic variation. (Abstract shortened by UMI.)