The role of seed dispersal, pollination and historical effects on genetic patterns of an insular plant that has lost its only seed disperser

Aim The genetic structure of many plant species is heavily dependent on their pollinators and seed dispersers, and can thus be altered if either of the associated mutualistic interactions is disrupted. In this study we assess the genetic diversity and structure and infer the seed/pollen gene-flow patterns among insular populations of Daphne rodriguezii, a shrub pollinated and dispersed by animals that has lost its only disperser (the lizard Podarcis lilfordi) in most of its populations. Location The island of Menorca and the islet of Colom (Balearic Islands, Western Mediterranean). Methods To assess the contribution of gene flow via pollen and seeds to the genetic structure of D.rodriguezii we used amplified fragment length polymorphisms (AFLPs; seeds and pollen) and plastid DNA sequences (cpDNA; seeds). We sampled individuals from all population nuclei of the species (12-19 adults per population): one population in Colom, where the plant-lizard interaction persists, and four in Menorca, where the seed dispersal mutualism disappeared with the extinction of the lizard. Results The highest heterozygosity values were found in Colom and in its closest population (Favàritx), whereas values were lower in the smallest Menorcan populations, which also had higher relatedness among individuals. We found distinct genetic signals between AFLP and cpDNA analyses. While AFLP markers showed low differentiation between populations, cpDNA showed a clear differentiation between them. Main conclusions Our results point to negative impacts of the disperser loss on genetic diversity and relatedness in the smaller and more isolated populations. They also suggest an old isolation by seeds, probably occurring well before the extinction of the lizard (c.2000years ago). Gene flow was maintained via pollination; however, the seed disperser loss may ultimately hinder pollinator-mediated gene flow, as a result of reduced probabilities of effective pollination among increasingly distant and scarce individuals. © 2012 Blackwell Publishing Ltd.The study was partially financed by projects BOS2011-0610 and GL2004-04884-C02-01/BOS from the Spanish Government and by a satellite project from the Consell Insular de Menorca (LIFE 2000 NAT/E/7355) financed to A.T., and by grant FP-2001-1819 (Dirección General de Investigación Científica y Técnica, Ministerio de Educación y Ciencia) to J.R.P. G.V.-A. is currently supported by a postdoctoral fellowship from the Portuguese Fundaçao para a Ciência e a Tecnologia (FCT) (Ref: SFRH/BPD/74834/2010). M.C.-C. was supported by an Isidro Parga Pondal contract (Xunta de Galicia)Peer Reviewe