POSTGLACIAL MIGRATION AND THE LOSS OF ALLOZYME VARIATION IN NORTHERN POPULATIONS OF ASCLEPIAS-EXALTATA (ASCLEPIADACEAE)

Authors
Citation
Sb. Broyles, POSTGLACIAL MIGRATION AND THE LOSS OF ALLOZYME VARIATION IN NORTHERN POPULATIONS OF ASCLEPIAS-EXALTATA (ASCLEPIADACEAE), American journal of botany, 85(8), 1998, pp. 1091-1097
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0002-9122
Volume
85
Issue
8
Year of publication
1998
Pages
1091 - 1097
Database
ISI
SICI code
0002-9122(1998)85:8<1091:PMATLO>2.0.ZU;2-5
Abstract
The recent Wisconsin glaciation has provided opportunities for examini ng the effects of postglacial recolonization on the population genetic s of plant and animal communities. In this study allozyme variation wa s examined in 19 populations of the herbaceous perennial Asclepias exa ltata occurring in previously glaciated regions of North America. Thes e northern populations of A. exaltata possess significantly fewer poly morphic loci (46.3 +/- 2.7; mean +/- 1 SD), alleles per polymorphic lo cus (1.84 +/- 0.24), and expected heterozygosity (0.133 +/- 0.031) tha n populations found in the Pleistocene refugium in the southern Appala chians. Population-level allozyme diversity decreased linearly from so uth to north and from east to west. Nineteen uncommon alleles previous ly observed in southern Appalachian populations were undetected in the northern region. Seven common alleles exhibited a clinal change in al lele frequency. Of these, only Pgd-1a and Mnr-1c were at low-frequency in the southern Appalachians and increased significantly with increas ing latitude and longitude, respectively. Despite this loss of allozym e diversity following postglacial migration, northern populations of A . exaltata have higher allozyme diversity and lower population differe ntiation (G(ST) = 0.117) than mean values for other long-lived herbace ous perennials. Increased habitat fragmentation in northern regions an d potential habitat loss in the southern Appalachians are likely to re duce the historically rich gene pool that has provided the genetic sto ck for postglacial recoveries.