A seasonal cycle in the frequency of electrophoretically distinguishable clones has been followed from late July 1985 to early August 1987 in an obligate parthenogenetic population of Heterocypris incongruens (Ramdohr) in a rice field located in the Po plain (Italy). Different clones predominate at different seasons. Summer and winter allozyme clones show size differences: otherwise the clones show no distinctive morphological features. The dimensional nature of the observed differences has been confirmed by multivariate analysis of 19 quantitative morphological traits. The electrophoretic clones reared in the laboratory at different temperatures (4?, 16?, 24?, 28?, 32?C) have survival curves and relative abundances that vary with temperature. In the laboratory, the clone dominant in the field in winter fares better at low temperatures while the clone dominant in the summer does so at high temperatures. Temperature is a likely selective factor responsible for the observed seasonal cycles in the field.
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Reference 4 in the article "Demic expansions and human evolution" by L. L. Cavalli-Sforza et al. (29 Jan., p. 639) was incorrect. It should have read as follows: "F. Weidenreich, Evolution 1, 221 (1947); C. Coon, The Living Races of Man (Knopf, New York, 1965); M. H. Wolpoff, in (2), pp. 62-108."
We report the genetic structure of 47 all-female populations of Heterocypris incongruens from Italy. Most populations (34) were collected from ricefields in the Po Plain (Northern Italy). Using three polymorphic allozyme markers (MPI, PGM and GPI) we found 125 different multilocus genotypes (clones) in a total of 3235 studied females. One clone was present almost everywhere (66 % localities) and in about a third (35 %) of all analysed females. Only a few clones (9 or 7 %) were found in more than ten localities while the majority (77 or 62 %) were found in only one population (private clones). Almost half (48 %) of all private clones were from the eight ricefields with the highest clonal richness while 16 % were from isolated temporary pools sampled for comparison. Clonal diversity seems to be the result of the presence of at least two different clonal lineages. One of the two, made up of the largest number of clones, probably had an autochthonous origin, a condition that probably favoured adaptation to local conditions. The other lineage was possibly introduced with imported rice seeds and its descendants carry adaptations to warm ricefield conditions. The weak relationship between genetic and geographic distance and the lack of spatial patterns in genetic variability might be due to the species' long-distance dispersal ability and to the persistence of founder effects sustained by large resting egg banks, conditions that blur isolation by distance. The lack of phylogeography in genetic variation may also be due to the spatially stochastic process of initiation and cessation of local ricefield cultivation known to have happened since the 15 th Century in this area of Northern Italy.
Abstract Small and isolated silver fir populations from the Emilian Apennines (northern Italy) were studied to assess their level of genetic variation and their relationship with Alpine populations. We investigated the variability of two chloroplast microsatellites to analyse the within‐population genetic variability of four peripheral and fragmented Apennine populations and to determine their phylogenetic relatedness to seven Alpine populations covering the entire distribution of silver fir in the Alps. Haplotypic richness and haplotype diversity as well as the fraction of private haplotypes were lower in Apennine populations, evidencing the genetic impoverishment of these stands. The among‐population genetic variability analysis revealed the genetic peculiarity of Apennine populations. Analysis of molecular variance showed that the highest level of the among‐population variation occurs between Alpine and Apennine regions. A neighbour‐joining dendrogram revealed a distinct Apennine cluster that included the closest Alpine population. Our genetic analysis supports a common origin for Emilian Apennine populations, suggesting that these populations are relicts of past large silver fir populations in the northern Apennines. Our results point to a relevant conservation value for these stands, to be considered in their management. Keywords: cpSSR markersfragmentationgenetic variabilityperipheral populationspost‐glacial re‐colonisation Acknowledgements This study was supported by a Life Nature LIFE97NAT/2 IT/4163 grant, co‐financed by the European Union and by the Emilia‐Romagna Region (Italy) project "Conservazione di abetaie e faggete appenniniche". The authors wish to thank all the people who contributed to this project, in particular Giuseppe Vignali, Lamberto Baratozzi, Federica Frattini, Federica Arduini, Antonia Cavalieri, Barbara Ferrari and Susi Carboni and W. Wilde‐Menozzi for language revision. We would like to thank Marta Scalfi and an anonymous reviewer for helpful comments on the manuscript.
