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A total evidence approach justifies taxonomic splitting of the endangered Pecos gambusia into three species

Published Article

Texas, New Mexico

Publication date: November 26, 2025

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A population genomics study of the endangered Gambusia nobilis across the Pecos River Drainage in Texas and New Mexico uncovered deep divergence among three lineages in the Leon Creek watershed, Toyah Creek watershed and Bitter Lake National Wildlife Refuge. Morphological differences supported these genetic splits, leading to recognition of two newly described species. These findings show that what was thought to be one species is actually three, underscoring the critical need to document biodiversity amid accelerating global loss.

Subject Tags

  • Wildlife
  • Desert
  • Watersheds

Abstract

Gambusia nobilis is a federally endangered species found across a fragmented distribution within the Pecos River Drainage of Texas and New Mexico, USA. Drought, human water usage, and potential hybridization and competition with introduced congeners threaten species persistence. Therefore, a population genomics study was conducted to provide critical information for conservation planning. Unsupervised clustering suggested hierarchical structure, with a primary K = 3, and deep divergences were detected among samples grouped into the Leon Creek watershed, the Toyah Creek watershed, and water bodies within the Bitter Lake National Wildlife Refuge (F’ST = 0.55–0.76 for putatively neutral data). Phylogenetic analyses showed three distinct clades corresponding to these groups, with divergence times estimated to be in the last 50 000 years. Complimentary morphological analyses detected differences among the three groups, including features of male colour pattern, and the number of caudal-fin rays in both sexes. Taken as a whole, the results indicate that the endangered G. nobilis comprises three species (two of which are named herein as G. pyrros n. sp. and G. echelleorum n. sp.), rather than one, and the study highlights the daunting yet critical task of documenting species diversity during a period of unprecedented diversity loss.

Citation

Portnoy, D. S., Bretzing-Tungate, R. J., Fields, A. T., Bean, M. G., Smith, R. K., Dolan, E. P., ... & Conway, K. W. (2025). A total evidence approach justifies taxonomic splitting of the endangered Pecos gambusia into three species. Royal Society Open Science, 12(11). https://doi.org/10.1098/rsos.251025

TNC Authors

  • Ryan K. Smith
    Director of Water and Science, Texas
    The Nature Conservancy
    Email: ryan_smith@tnc.org