Get access

Polyploidy and microsatellite variation in the relict tree Prunus lusitanica L.: how effective are refugia in preserving genotypic diversity of clonal taxa?

Authors

  • C. García-Verdugo,

    Corresponding author
    1. Department of Integrative Biology and Jepson Herbarium, University of California, Berkeley, Berkeley, CA, USA
    2. Departamento de Biodiversidad Molecular y Banco de ADN, Jardín Botánico Canario “Viera y Clavijo”, Cabildo de Gran Canaria, Las Palmas de Gran Canaria, Spain
    Search for more papers by this author
  • J. A. Calleja,

    1. Departamento de Biología (Botánica), Universidad Autónoma de Madrid, Madrid, Spain
    Search for more papers by this author
  • P. Vargas,

    1. Real Jardín Botánico de Madrid, CSIC, Madrid, Spain
    Search for more papers by this author
  • L. Silva,

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores – Departamento de biologia da Universidade dos Açores, Portugal
    Search for more papers by this author
  • O. Moreira,

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores – Departamento de biologia da Universidade dos Açores, Portugal
    Search for more papers by this author
  • F. Pulido

    1. Grupo de Investigación Forestal, EUIT Forestal, Universidad de Extremadura, Plasencia, Spain
    Search for more papers by this author

Abstract

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 Prunus lusitanica, a polyploid species with clonal reproduction that is considered a paradigmatic example of a Tertiary relict. Sampling in this study considered a total of 20 populations of three subspecies: mainland lusitanica (Iberian Peninsula and Morocco), and island azorica (Azores) and hixa (Canary Islands and Madeira). 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.

Get access to the full text of this article

Ancillary