Estimating dispersal and gene flow in the neotropical freshwater turtle Hydromedusa maximiliani (Chelidae) by combining ecological and genetic methods

Franco L Souza,Anderson F Cunha,Gonçalo A.G Pereira,Marcos A Oliveira,Sérgio F Dos Reis

doi:10.1590/s1415-47572002000200007

Abstract

Hydromedusa maximiliani is a vulnerable neotropical freshwater turtle endemic to mountainous regions of the Atlantic rainforest in southeastern Brazil. Random amplified polymorphic DNA (RAPD) was used to estimate the gene flow and dispersal for individuals inhabiting rivers and streams within a drainage. Nine primers generated 27 scoreable bands, of which 9 (33%) were polymorphic and produced 12 RAPD phenotypes. The gene flow estimates (Nm) among turtles inhabiting different rivers and streams were variable, ranging from 0.09 to 3.00 (mean: 0.60). For some loci, the rates of gene flow could offset population differentiation (Nm > 1), whereas for others random genetic drift could result in population divergence (Nm < 1). Since the genetic variation of this turtle seems to be structured according to the natural hierarchical system of rivers and streams within drainages, management programs involving translocations between different regions across the geographical range of H. maximiliani should be viewed with caution.

Highlights

The neotropical freshwater turtle Hydromedusa maximiliani (Chelidae) is endemic to the Atlantic forest of the coastal region of southeastern Brazil, with a geographical distribution ranging from the State of Espírito Santo to the State of São Paulo (Ernst and Barbour, 1989; Iverson 1992)
The observed limited dispersal suggests that each H. maximiliani population inhabits a specific river within a given drainage system, and this hypothesis was addressed in a preliminary work on the population genetic structure of the species, which indicated a substantial partitioning of molecular variation across rivers and streams inhabited by this turtle (Souza et al, 2002)
Field work was conducted from November 1998 to November 1999 at the Parque Estadual de Carlos Botelho (PECB), state of São Paulo, southeastern Brazil (24°00’24°15’S, 47°45’-48°10’W)

Summary

Introduction

The neotropical freshwater turtle Hydromedusa maximiliani (Chelidae) is endemic to the Atlantic forest of the coastal region of southeastern Brazil, with a geographical distribution ranging from the State of Espírito Santo to the State of São Paulo (Ernst and Barbour, 1989; Iverson 1992). The observed limited dispersal suggests that each H. maximiliani population inhabits a specific river within a given drainage system, and this hypothesis was addressed in a preliminary work on the population genetic structure of the species, which indicated a substantial partitioning of molecular variation across rivers and streams inhabited by this turtle (Souza et al, 2002) These findings of population structure on a small spatial scale defined by the complex topographical features of the species’ habitat, a region topologically complex, with ridges and valleys drained by numerous rivers and streams (Pfeifer et al, 1986; Souza and Abe 1998), could imply that there is little or no gene flow among turtles inhabiting different water courses or distinct drainage. We used random amplified polymorphic DNA (RAPD) markers (Williams et al, 1993) to assess levels of gene flow among local H. maximiliani populations, and briefly discuss the conservation and management implications of our findings

Methods

Results

Conclusion