Distribution, genetic analysis and conservation priorities for rare Texas freshwater molluscs in the genera Fusconaia and Pleurobema (Bivalvia: Unionidae)

Alexander Y Karatayev,David Campbell,Lyubov E Burlakova,Don Barclay

doi:10.1186/2046-9063-8-12

Abstract

BackgroundFreshwater bivalves in the order Unionoida are considered to be one of the most endangered groups of animals in North America. In Texas, where over 60% of unionids are rare or very rare, 15 species have been recently added to the state’s list of threatened species, and 11 are under consideration for federal listing. Due to insufficient survey efforts in the past decades, however, primary data on current distribution and habitat requirement for most of these rare species are lacking, thus challenging their protection and management. Taxonomic identification of endemic species based on shell morphology is challenging and complicates conservation efforts. In this paper we present historic and current distributional data for three rare Texas species, Fusconaia askewi, F. lananensis, and Pleurobema riddellii, collected during our 2003–2011 state-wide surveys and suggest appropriate conservation measures. In addition, we tested the genetic affinities of Fusconaia and similar species collected from eastern Texas and western Louisiana using cox1 and nad1 sequences.ResultsWe found that F. askewi still inhabits four river basins in eastern and northeastern Texas and can be locally abundant, while P. riddellii was found only in one river basin. Pleurobema riddellii was well-separated from F. askewi and grouped with the P. sintoxia clade. The sequences for F. lananensis were very similar to those for F. askewi, with a maximum difference of just over 1% for nad1 and only 0.7% for cox1, similar to the variation between F. askewi alleles. Except for one low difference (1.55%) with the partial cox1 sequence for F. burkei, all other Fusconaia populations, including those from the Calcasieu drainage, differed by over 2.3% for both genes.ConclusionsOur study suggested that F. lananensis is not a valid species, and it is likely that only one Fusconaia species (F. askewi or its probable senior synonym F. chunii) is currently present in East Texas, thus simplifying conservation efforts. Distribution range of both these regional endemics (F. askewi and P. riddellii) has been reduced in the last 80 years.

Highlights

Freshwater bivalves in the order Unionoida are considered to be one of the most endangered groups of animals in North America
All Fusconaia species identified during our study (F. askewi and F. lananensis) and historical data reported from East Texas
Genetic analysis The sequences for F. lananensis were very similar to those for F. askewi, with less than 1% difference, similar to the variation between F. askewi alleles (Tables 1, 2)

Summary

Introduction

In Texas, where over 60% of unionids are rare or very rare, 15 species have been recently added to the state’s list of threatened species, and 11 are under consideration for federal listing. In this paper we present historic and current distributional data for three rare Texas species, Fusconaia askewi, F. lananensis, and Pleurobema riddellii, collected during our 2003–2011 state-wide surveys and suggest appropriate conservation measures. Molluscs are among the most threatened groups of animals on the planet [1], and freshwater bivalves in the order Unionoida are considered to be one of the most endangered groups of animals in North America [2,3,4]. Fifteen rare freshwater mussel species were recently added to the state’s list of threatened species [8], and 11 of those are currently under consideration for federal listing by the U. Fish and Wildlife Service [9,10]

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Results

Discussion

Conclusion