FORM OF RARITY AFFECTS LEVELS OF WITHIN-POPULATION ISOZYME VARIATION IN AN ENDANGERED CONIFER

PREMOLI, A.; C. SOUTO; A. NEWTON; T. ALLNUT

USA

Congreso; The Society for Conservation Biology’s Annual Meeting; 2000

Society for conservation biology

It has been suggested that the geographic range is a good predictor of the levels of genetic variation in plant populations.  We analyzed the hypothesis that the type of rarity based on the combination of species’ geographic range, habitat specificity, and population size would be a better indicator to explain patterns of genetic variability in populations particularly of endangered species.  We tested this hypothesis analyzing the distribution of isozyme variation of the widespread long-lived conifer Pilgerodendron uviferum (Don.) Flor (Cupressaceae) that inhabits temperate South America from the Valdivian rainforest at 39’30°S to 55°30’S in Tierra del Fuego.   Fresh folliage tissue collected from eighteen populations sampled throughout the species’ entire range was analyzed by horizontal electrophoresis on starch gels.  Fourteen isozyme loci were reliably scored yielding reduced levels of variation with only 1.2 mean number of alleles/locus, 14% of polymorphism, 0.025 and 0.035 observed and expected heterozygosity, respectively. In a multiple regression analysis, genetic variation was significantly correlated with population size, geographic location, elevation, and degree of disturbance (P<0.05).  Relatively high level of among-population differentiation was recorded (GST=17%).  Our results indicate the importance of considering the form of rarity to predict genetic characteristics of plant taxa and to design conservation strategies.