title: Lack of genetic isolation by distance, similar genetic structuring but different demographic histories in a fig-pollinating wasp mutualism.
abstract: Historical abiotic factors such as climatic oscillations and extreme climatic events as well as biotic factors have shaped the structuring of species' genetic diversity. In obligate species-specific mutualisms, the biogeographic histories of the interacting species are tightly linked. This could be particularly true for nuclear genes in the Ficus-pollinating wasp mutualistic association as the insects disperse pollen from their natal tree. In this study, we compare spatial genetic structure of plant and pollinator for the Ficus hirta-Valisia javana association throughout southeast China including Hainan Island, for both nuclear and cytoplasmic markers. We show that dispersal of the insect leads to plant and insect presenting similar signatures of lack of genetic isolation by distance for nuclear genes on the continent over a distance of 1000 km. But we also show that the demographic histories of plant and insect are strikingly different. This is in agreement with extreme climatic events leading to transient regional extinctions of the insects, associated with local survival of the plants. We also observe evidence of genetic differentiation for both wasps and fig-tree between the continent and Hainan Island, although the Qiongzhou Strait is only on average 30 km wide, suggesting that geographic isolation by itself has not been sufficient to generate this differentiation. Hence, our results suggest that in highly dispersive mutualistic systems, isolation-by-dispersal limitation across a geographic barrier could be supplemented by isolation by adaptation, and maybe by coevolution, allowing further genetic divergence. In such systems, species may frequently be composed of a single population.
authors.affiliation: Key Laboratory of Plant Resource Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Enwei
authors.initials: E
authors.lastname: Tian
authors.affiliation: Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Nason
authors.affiliation: Department of Biology, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Machado
authors.affiliation: Key Laboratory of Plant Resource Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Linna
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Plant Resource Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Yu
authors.affiliation: CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, Montpellier, France.
authors.forename: Finn
authors.initials: F
authors.lastname: Kjellberg
mesh_terms: D000818:Animals; D002681:China; D004272:DNA, Mitochondrial / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D030681:Ficus / Q000235:genetics*; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D054817:Pollination; D060047:Reproductive Isolation; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D014863:Wasps / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial
keywords: Ficus hirta; Valisia javana; mutualism; phylogeography