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Levels and patterns of genetic variation in the endangered species Abronia macrocarpa (Nyctaginaceae)
Author(s) -
Williamson Paula S.,
Werth Charles R.
Publication year - 1999
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2656946
Subject(s) - biology , population , outcrossing , isolation by distance , genetic variation , gene flow , ecology , zoology , genetics , gene , pollen , demography , sociology
Genetic variation was evaluated in the federally endangered species Abronia macrocarpa (large‐fruited sand‐verbena), an herbaceous perennial restricted to deep sandy soils and endemic to three counties of east‐central Texas. Seven of the ten known populations were sampled and analyzed using starch gel electrophoresis of eight enzymes coded by 18 interpretable loci. Duplicate gene expression was observed for four loci, suggesting polyploid ancestry for the lineage that includes A. macrocarpa . Values for estimators of genetic polymorphism within populations (ranges: P = 38.9%–61.1%, A = 1.7–2.1, H = 0.122–0.279) exceeded average values for seed plants (P = 34.2%, A = 1.53, H = 0.113). Genotype proportions at most loci in most populations were in Hardy‐Weinberg equilibrium, consistent with obligate outcrossing previously documented for this species; exceptions could be attributed to population substructure. Values of F ST tended to be high, ranging from 0.021 to 0.481 for individual loci (mean F ST = 0.272), indicating substantial divergence and limited gene flow among populations, despite their close geographic proximity. Pairwise values of Nei's genetic identity between populations ranged from 0.799 to 0.975 and tended to be influenced by geographic proximity of population pairs. Collectively, these data suggest a long history of isolation among populations that have not been subjected to bottlenecks. Isolation of A. macrocarpa populations apparently results from the disjunct occurrence of suitable habitat and perhaps has been accentuated by human disturbance.