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.
Palmé
A E
AE
Department of Conservation Biology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, 752 36 Uppsala, Sweden. anna.palme@ebc.uu.se
Semerikov
V
V
Lascoux
M
M
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