Univariate and multivariate statistical analyses of 39 meristic characters recorded for 12 samples of the lizard Liolaemus monticola were used to compare geographical variation in morphology with chromosomal races north and south of the Maipo River in central Chile. This extends a previous morphological study in the Andes Range and confirms that the Maipo River is a biogeographical barrier that also separates chromosomal races in the Coast Range. The phenetic variation among samples is sufficient to differentiate the chromosomal races, and also distinguishes populations of the Coast Range from those of the Andes within chromosomal races. A possible historical sequence of events that accounts for the pattern of morphological differentiation is advanced.

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Univariate and multivariate statistical analyses of 28 meristic characters recorded for 19 samples of the lizard Liolaemus monticola monticola were used to compare geographical variation in morphology with chromosomal races north and south of the Maipo River, and north and south of the Aconcagua River in central Chile, plus some affluent. This extends a previous morphological study that confirmed that the Maipo River is a biogeographical barrier that separates chromosomal races "Southern, 2n=34" and "Northern, 2n=38-40", and reports for the first time the importance of the Aconcagua River as another biogeographical barrier between the chromosomal races "Northern, 2n=38-40" and the "Multiple Fission, 2n=42-44". The phenetic variation among samples is sufficient to differentiate the three chromosomal races, and also distinguishes populations within the chromosomal races such as the ones separated by the Colorado River, an affluent of the Aconcagua River. A possible historical sequence of events that accounts for the pattern of morphological differentiation is advanced.

Intra-and interpopulation morphological variation in 14 meristic characters was assessed in twelve previously karyotyped population samples of Liolaemus monticola monticola, representing two chromosomal races: the Southern race (2 n = 34) and the Northern race (2 n = 38 to 40), plus a zone of secondary contact where both races and hybrids between them occur. The phenetic analyses were performed to investigate the effect of chromosomal changes and riverine barriers to gene flow on the differentiation of these lizard populations.The morphological similarities of populations determined by multivariate analysis coincides exactly with the separation into chromosomal races, and thus confirms the riverine barriers. The first principal component clearly separates the two chromosome races, based on at least 7 characters, with the zone of secondary contact in an intermediate position. Within races, there was not a close correspondence between phenetic similarity and geographic location. There was no evidence for reduced nor increased morphological variability in the derived (Northern) chromosomal race.These results are consistent both with the major expectations of several models of chromosome evolution and with the model of alloyatric isolation; we cannot discriminate between these alternatives. However, the morphologica variability of the Northern race argues against the hypothesis that the derived karyotypes originated by recent bottleneck events.

Agr. 36(2):229-238. Random Amplifi ed Polymorphic DNA (RAPD) markers were used to assess the genetic diversity of 587 individuals, belonging to 22 populations of Nothofagus nervosa that were distributed through the Coastal (38°S to 41°S) and Andes Mountains in CentralSouthern Chile (36°S to 40°S). The objective of this study was to complement the genetic inferences previously determined by isozyme analysis, in order to obtain more accurate genetic diversity estimations. We scored 81.8% of the polymorphic loci of the samples tested. The average incidence of genetic polymorphism within populations was high, with values ranging between 33% and 63%. Analysis of molecular variance (AMOVA) showed most of the genetic variation was distributed within populations (87.6%), but F ST values (F ST = 0.124; p < 0.00001) indicated that there was also a signifi cant difference among populations. A discriminant analysis revealed three geographically defi ned groups and showed that 14 loci explained 87.2% of the genetic differentiation among N. nervosa populations. Watterson's neutrality test and Ohta's two-locus analysis of linkage disequilibrium (LD) both suggested that stochastic demographic and environmental factors can partially explain the loci variation observed in the RAPDs. The role of the last glaciations, as well as some conservation and breeding strategies, may have infl uenced current genetic variation and fragmentation in this species.