Absence of geographical structure of chloroplast DNA variation in sallow, Salix caprea L.
In the present study, we have used PCR-RFLP markers to investigate the chloroplast DNA variation in 24 European populations of Salix caprea L. A subset of these populations has also been analysed with chloroplast microsatellites. The main feature of both markers is the absence of a clear geographic structure (G(ST(PCR-RFLP))=0.090, G(ST(microsatellites))=-0.017) and high levels of variation within populations. This lack of phylogeographic structure in S. caprea is suggested to be the consequence of the joint action of several factors: (i) presence of intermediate latitude refugia with large population sizes during the last glacial maximum, (ii) a high speed of recolonisation and dispersal ability, (iii) a high mutation rate and (iv) extensive hybridisation with other willow species. In addition to the S. caprea samples, a limited number of individuals from several other Salix species were also analysed with PCR-RFLP: S. cinerea, S. aurita, S. purpurea, S. atrocinerea, S. appendiculata, S. elaeagnos, S. fragilis and S. alba. Many of the haplotypes found in Salix caprea were also detected in S. cinerea, S. aurita, S. purpurea, S. atrocinerea and/ or S. appendiculata but not in S. alba, S. elaeagnos or S. fragilis. Our data suggest that hybridisation and gene flow have occurred within these two groups but not between them.
Department of Conservation Biology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, 752 36 Uppsala, Sweden. anna.palme@ebc.uu.se
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Palmé
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Semerikov
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Lascoux
D018742:DNA, Chloroplast / Q000235:genetics*; D004777:Environment; D005060:Europe; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes / Q000235:genetics*; D006824:Hybridization, Genetic; D018895:Microsatellite Repeats / Q000235:genetics; D009154:Mutation / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D012044:Regression Analysis; D032108:Salix / Q000235:genetics*
D018742:DNA, Chloroplast