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Polyploidy and microsatellite variation in the relict tree P runus lusitanica L .: how effective are refugia in preserving genotypic diversity of clonal taxa?
Author(s) -
GarcíaVerdugo C.,
Calleja J. A.,
Vargas P.,
Silva L.,
Moreira O.,
Pulido F.
Publication year - 2013
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.12194
Subject(s) - biology , polyploid , gene flow , genetic diversity , microsatellite , genetic variation , population , genetic variability , gene pool , allele , evolutionary biology , ploidy , genotype , genetics , gene , demography , sociology
Refugia are expected to preserve genetic variation of relict taxa, especially in polyploids, because high gene dosages could prevent genetic erosion in small isolated populations. However, other attributes linked to polyploidy, such as asexual reproduction, may strongly limit the levels of genetic variability in relict populations. Here, ploidy levels and patterns of genetic variation at nuclear microsatellite loci were analysed in P runus lusitanica , a polyploid species with clonal reproduction that is considered a paradigmatic example of a T ertiary relict. Sampling in this study considered a total of 20 populations of three subspecies: mainland lusitanica ( I berian P eninsula and M orocco), and island azorica ( A zores) and hixa ( C anary I slands and M adeira). Flow cytometry results supported an octoploid genome for lusitanica and hixa , whereas a 16‐ploid level was inferred for azorica . Fixed heterozygosity of a few allele variants at most microsatellite loci resulted in levels of allelic diversity much lower than those expected for a high‐order polyploid. Islands as a whole did not contain higher levels of genetic variation (allelic or genotypic) than mainland refuges, but island populations displayed more private alleles and higher genotypic diversity in old volcanic areas. Patterns of microsatellite variation were compatible with the occurrence of clonal individuals in all but two island populations, and the incidence of clonality within populations negatively correlated with the estimated timing of colonization. Our results also suggest that gene flow has been very rare among populations, and thus population growth following founder events was apparently mediated by clonality rather than seed recruitment, especially in mainland areas. This study extends to clonal taxa the idea of oceanic islands as important refugia for biodiversity, since the conditions for generation and maintenance of clonal diversity (i.e. occasional events of sexual reproduction, mutation and/or seed immigration) appear to have been more frequent in these enclaves than in mainland areas.