title: Genetic variability within and among populations of an invasive, exotic orchid.
abstract: Despite the fact that invasive species are of great evolutionary interest because of their success in colonizing and spreading into new areas, the factors underlying this success often remain obscure. In this sense, studies on population genetics and phylogenetic relationships of invasive species could offer insights into mechanisms of invasions. Originally from Africa, the terrestrial orchid Oeceoclades maculata, considered an invasive plant, is the only species of the genus throughout the Americas. Considering the lack of information on population genetics of this species, the aim of this study was to evaluate the genetic diversity and structure of Brazilian populations of O. maculata. We used 13 inter-simple sequence repeat primers to assess the genetic diversity of 152 individuals of O. maculata distributed in five sampled sites from three Brazilian states (São Paulo, Mato Grosso and Paraná). Low diversity was found within samples, with estimates of the Shannon index (H) ranging from 0.0094 to 0.1054 and estimates of Nei's gene diversity (He) ranging from 0.0054 to 0.0668. However, when evaluated together, the sampling locations showed substantially higher diversity estimates (H = 0.3869, He = 0.2556), and most of the genetic diversity was found among populations (ΦST = 0.933). Both clustering and principal coordinate analysis indicate the existence of five distinct groups, corresponding to the sampled localities, and which were also recovered in the Bayesian analysis. A substructure was observed in one of the localities, suggesting a lack of gene flow even between very small distances. The patterns of genetic structure found in this study may be understood considering the interaction of several probable reproductive strategies with its history of colonization involving possible genetic drift, selective pressures and multiple introductions.
authors.affiliation: Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiroz', Universidade de São Paulo, CP 83, Piracicaba, São Paulo 13418-900, Brazil.
authors.forename: Sueme
authors.initials: S
authors.lastname: Ueno
authors.affiliation: Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiroz', Universidade de São Paulo, CP 83, Piracicaba, São Paulo 13418-900, Brazil.
authors.forename: Jucelene Fernandes
authors.initials: JF
authors.lastname: Rodrigues
authors.affiliation: Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiroz', Universidade de São Paulo, CP 83, Piracicaba, São Paulo 13418-900, Brazil.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Alves-Pereira
authors.affiliation: Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil.
authors.forename: Emerson Ricardo
authors.initials: ER
authors.lastname: Pansarin
authors.affiliation: Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiroz', Universidade de São Paulo, CP 83, Piracicaba, São Paulo 13418-900, Brazil eaveasey@usp.br.
authors.forename: Elizabeth Ann
authors.initials: EA
authors.lastname: Veasey
keywords: Genetic diversity; ISSR markers; Oeceoclades maculata; Orchidaceae; invasive plants; population genetic structure