Distribution of Unionid Mussels in the Big Thicket Region of Texas
Distribution of Unionid Mussels in the Big Thicket Region of Texas

Author: Alison A. Tarter

Publisher:

Published: 2019

Total Pages: 90

ISBN-13:

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The Big Thicket located in Southeast Texas harbors the highest number of regional endemic freshwater mussel species and the highest diversity of unionid mussels in the state, including five state-threatened species. Unfortunately, mussels in this region are threatened by pollution, habitat alteration and destruction due to human impacts caused by petrochemical activities, climatic changes and urbanization. The goals of this project were to (1) survey mussels in the Big Thicket National Preserve, particularly in the poorly surveyed southern portion of the preserve, and (2) to examine historical changes in mussel communities. In addition, DNA samples were taken and the analysis of 97 mussels informed identification of ten species, some of which can be difficult to distinguish morphologically. A total of 39 sites in the Lower Neches River, Village Creek and Pine Island Bayou basins were surveyed. Historical data from 2002 (restricted to Village Creek) and 2014 were available for sub-set of these sites. The survey showed that species richness and mussel densities generally increased from upstream tributaries towards lower Village Creek and the mainstream Neches, where rare and threatened species were mostly found. Evidence for recruitment was mainly found in the backwaters of the lower Neches, which may act as a refuge during flooding. Declines between 2014 and 2018 were most severe in the parts of the Neches basin that most likely experienced the highest shear stress during flooding based on the channel morphology. Declines were also detected when data from 2002 were compared with 2014 suggesting that the exceptional drought in 2011 may have also contributed to long-term declines in Village Creek. Future studies should examine the role of backwaters for recruitment of threatened mussels.

Freshwater Mussels of Texas
Freshwater Mussels of Texas

Author: Robert G. Howells

Publisher: University of Texas Press

Published: 1996-09

Total Pages: 228

ISBN-13: 9781885696106

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Species. Freshwater mussels are the most rapidly declining group of animals in North America. This guide represents a first-ofits-kind reference to assist both biologists and naturalists in the identification and study of freshwater mussels. Freshwater Mussels of Texas contains 224 pages with 226 black and white photographs, 144 color photographs and 79 line drawings covering all 52 species found in Texas waters. Introductory sections cover basic anatomy, reproduction.

The Population Genetic Structure of Quadrula Aurea (Bivalvia: Unionidae), A Threatened Freshwater Mussel in Central Texas
The Population Genetic Structure of Quadrula Aurea (Bivalvia: Unionidae), A Threatened Freshwater Mussel in Central Texas

Author: Jeffrey A. Mabe

Publisher:

Published: 2018

Total Pages: 148

ISBN-13:

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The anthropogenic alteration of riverine ecosystems has led to declines in the abundance and diversity of freshwater mussels (Bivalvia: Unionoida) worldwide. Central Texas is home to a diverse freshwater mussel fauna including three candidates for federal listing under the Endangered Species Act. Surveys conducted over the last few decades suggest many of the endemic freshwater mussel species in Texas exist in small isolated populations that may be vulnerable to the deleterious effects of genetic diversity loss. Microsatellite primers from two closely related species were used to identify a set of genetic markers that functioned in the Golden Orb (Quadrula aurea). Microsatellite markers were then applied to document the population genetic structure of Q. aurea within and among three connected river drainages in southeastern Texas. Gene flow within existing Q. aurea populations appears high indicating little potential for genetic issues stemming from isolation and inbreeding. Two weakly divergent admixed populations were identified occupying the San Antonio and Guadalupe/San Marcos rivers. Population genetic structure was related to river basin affiliation, but results for environmental factors were unresolved. Current effective population size estimates are large for the Guadalupe/San Marcos drainage and moderately large for the San Antonio drainage and there is no clear genetic evidence of contemporary population declines. Transport in the glochidial phase by a highly mobile host fish, the channel catfish (Ictalurus punctatus), may provide a mechanism for maintaining connectivity among spatially discrete mussel beds and deserves further study. Information on the occurrence and habitat associations of Q. aurea and two other threatened freshwater mussel species was documented. Quantification of the population genetic structure for Q. aurea provides important information needed for the management of this species, a baseline for understanding future changes, and insight into the factors that shape the population genetic structure of other threatened unionids in Texas.