Genetic patterns in Podocarpus parlatorei reveal the long-term persistence of coldtolerant elements in the southern Yungas

M. PAULA QUIROGA, ANDREA C. PREMOLI

JOURNAL OF BIOGEOGRAPHY

Año: 2007 vol. 34 p. 447 - 455

0305-0270

Aim This study analyses long-term responses to climate changes in Podocarpusparlatorei, a cold-tolerant tree species from the subtropics in South America,using distribution patterns of isozyme variation.Location Podocarpus parlatorei characterizes montane forests within the Yungas,a cloud forest of the subtropics of north-western Argentina and southern Bolivia.Podocarpus parlatorei consists of disjunct populations ecologically subdivided intonorthern, central, and southern sectors that we predict will be geneticallydivergent from one another as a result of historical isolation.Methods We collected fresh leaves from a maximum of 30 randomly selectedindividuals from each of 18 populations. We resolved 25 isozyme loci, and scoredthe most consistent 14, 57% of which were polymorphic. Within-populationvariation was tested against latitude, longitude, and elevation using multipleregressions. Genetic structure across populations was analysed using diversityparameters. The relationship between genetic and geographic distances wasexplored with reference to Pearson correlation coefficients.Results The effective number of alleles and observed heterozygosity increaselatitudinally. Southern populations tend to be the most variable and geneticallydistinct. This result suggests that they could represent the location of a long-termrefuge for P. parlatorei. The mean number of alleles per locus decreases withelevation. The total genetic diversity is HT ¼ 0.163, 10% of which is distributedamong populations. A positive association between genetic and geographicdistances was detected.Main conclusions Reductions in genetic diversity towards the north and highelevationmountains are consistent with evidence of patterns of forest migrationresulting from climate change during the Late Quaternary, northern expansionduring episodes of cooling, and range contraction towards the highlands duringwarming trends. Naturally disjunct populations of P. parlatorei are geneticallydivergent from one another, indicating that local genetic stocks should be usedfor restoration of degraded habitats.