TITLE	Genetic divergence among natural populations of Alstroemeria aurea D. Don: A dominant clonal herb of the understory in subalpine Nothofagus forests
AUTHOR	Cintia P. Souto* Laboratorio Ecotono, Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Argentina A.C. Premoli Laboratorio Ecotono, Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Argentina
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ABSTRACT	Alstroemeria aurea is a perennial herb with clonal rhizomatous growth, insect pollination, and ballistic seed dispersal that inhabits a range of different environments in the southern Andes. We evaluated the hypothesis that differential selective pressures act together with restricted among-population gene flow result in genetically divergent populations of A. aurea. Study sites were located within Nahuel Huapi National Park (41°8'S, 71°19'W) at two mountain ranges and two different elevations. These were Chall Huaco Valley, a pristine site, with populations at 1,250 and 1,100 m, respectively, and Cerro Otto, a disturbed site, with populations at 1,250 and 950 m, respectively. Seeds at each of the four populations were harvested from 20, 1 × 1 m plots. These seeds were counted, weighed, and germinated after a cold and humid stratification for 4 months. Within- and between-mountain ranges differences in seed traits were evaluated by ANOVA. We genetically characterized 30 plants of each population by allozyme electrophoresis and estimated levels of genetic variation and divergence. Seed traits showed different responses to elevation and site conditions. Total number of seeds was greater at low-elevation populations even though they had a higher number of undeveloped seeds. Reduced seed yield at high-elevation populations may result from a short growing season at higher altitudes. Additionally, seed weight, germination rates, and early vegetative spread were significantly greater at Otto, which may suggest a selective strategy to colonize disturbed sites under favorable physical conditions. These between-site differences were supported by allozyme data. High genetic divergence, and thus low gene flow, was estimated among Otto and Chall Huaco whereas within each mountain range among-population divergence depended upon site characteristics. Higher gene flow rates were found in the disturbed site Otto. Our results indicate that restricted pollen and seed dispersal, together with selective forces acting in different habitats, may produce genetic differentiation in populations of A. aurea.
KEYWORD	Alstroemeriaceae; Allozyme electrophoresis; Gene flow; Genetic structure; Germination; Patagonia; Seeds;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 44 Number 4 October 2003, page 329-336, 8 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China