Subterranean Fishes of the World

5756

2019

302 pages

Dissertation Presented to the Graduate Faculty of the University of Louisiana at Lafayette In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy

This doctoral dissertation focuses on the genetic, geographic, and morphological bases of speciation in glass knifefishes of the genus Eigenmannia, a species-rich but morphologically-conserved clade of Neotropical freshwater fishes. The Neotropical freshwater ichthyofauna is the most diverse on Earth, encompassing >8,000 species or approximately one-quarter of all living fishes. The freshwater fish genus Eigenmannia represents an excellent model in which to study the formation of this immense diversity, exhibiting many features commonly observed in members of the fauna. Eigenmannia has diversified into at least 21 species, including a few geographically widespread and many geographically restricted species. Further, Eigenmannia species exhibit little divergences in features of external morphology, such that most sister-species pairs do not differ substantially in ecologicallyrelated aspects of head and jaw morphology, but rather differ primarily on the basis of social communication signals and karyotypes. Such a cryptic (or in some cases pseudocryptic) nature of phenotypic differences among closely related species has hampered efforts to document diversity in this genus, as in the Neotropical fauna as a whole, and obscured the role of ecological and evolutionary processes in producing this incredible species richness.

1