Conservation Genetics

, Volume 17, Issue 3, pp 593–602

Evidence for genetic erosion of a California native tree, Platanus racemosa, via recent, ongoing introgressive hybridization with an introduced ornamental species

  • Matthew G. Johnson
  • Kylene Lang
  • Paul Manos
  • Greg H. Golet
  • Kristina A. Schierenbeck
Research Article

DOI: 10.1007/s10592-015-0808-z

Cite this article as:
Johnson, M.G., Lang, K., Manos, P. et al. Conserv Genet (2016) 17: 593. doi:10.1007/s10592-015-0808-z

Abstract

When non-native, genetically diverse species are introduced, hybridization with native congeners may erode the genetic composition of local species, perhaps even resulting in extinction. While such events may lead to adverse consequences at the community and ecosystem level, few studies exist on ecologically important tree species. In the genus Platanus, introgressive hybridization is widespread, and one common ornamental species, introduced to California during the late 19th century, is itself a hybrid. Our microsatellite analysis of more than 400 Platanus trees from north-central California reveals a complex pattern of invasion and hybridization in an age-structured population. By using size as a proxy for age, we have demonstrated that the Platanus population of north-central California has recently gained genetic diversity and effective population size. Principal coordinate analysis (PCoA) and genetic admixture analysis (STRUCTURE) both reveal a strong differentiation of genotypes into two main genetic clusters, with a large number of admixed genotypes. One of the genetic clusters identified is heavily biased towards younger trees, including samples from locations with relatively recently planted ornamental trees likely to be P. × hispanica (formerly known as P. × acerifolia). We conclude that the two genetic clusters correspond to the native P. racemosa and the introduced invasive hybrid species P. × hispanica. Additional hybridization between the invasive ornamental and the native species has occurred in California, and recent hybrid trees are more likely to be younger than trees without admixture. Our findings suggest that the observed increase in genetic diversity among California Platanus is due to rampant ongoing introgression, which may be threatening the continued genetic distinctiveness of the native species. This is cause for concern from a conservation standpoint, due to a direct loss of genetic distinctiveness, and a potential reduction in habitat value of associated species.

Keywords

Hybrid zone Admixture Sycamore Microsatellite 

Supplementary material

10592_2015_808_MOESM1_ESM.docx (119 kb)
Supplementary material 1 (DOCX 118 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  1. 1.Department of Plant SciencesChicago Botanic GardenGlencoeUSA
  2. 2.Department of Biological SciencesCalifornia State University-ChicoChicoUSA
  3. 3.Biology DepartmentDuke UniversityDurhamUSA
  4. 4.The Nature ConservancyChicoUSA

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