# The Carpiodes Conundrum: Molecular Hypothesis Testing Informs Conservation Applications for Carpsuckers (Catostomidae: Carpiodes) in Texas and Beyond

## TL;DR

This study uses genetic analysis to clarify the taxonomy of carpsuckers in Texas, revealing potential new species and informing conservation strategies.

## Contribution

The study provides new insights into the native status and genetic relationships of Llano River Carpsucker, supporting conservation decisions.

## Key findings

- Llano River Carpsucker specimens form unique lineages related to C. cyprinus, supporting their native status.
- Cryptic undescribed species of Carpiodes are likely present in Eastern Gulf of Mexico drainages.
- C. cyprinus hybridizes with C. carpio, leading to mitochondrial introgression across their range.

## Abstract

Sufficient taxonomic understanding is critical for biodiversity conservation. This is particularly relevant among freshwater fishes, where cryptic undescribed species cause difficulties for promoting conservation efforts. Catostomidae (i.e., suckers) is a family of freshwater fishes with cryptic diversity and biological traits that make them difficult to classify taxonomically. Among suckers, the Carpsuckers (
Carpiodes carpio
,
Carpiodes cyprinus
,
Carpiodes velifer
) possess uncertain taxonomic classifications and cryptic diversity despite a rich history of research. Within Carpiodes, uniquely slender‐bodied populations occurring in Western Gulf of Mexico drainages suggest potential for an undescribed species. Originally collected in the Llano River, tributary to the Texas Colorado River, Llano River Carpsucker are morphologically similar to
C. cyprinus
. Our study explores how historical biogeographic scenarios may have led to lineage diversification of Llano River Carpsucker. We test competing molecular hypotheses (i.e., Native Endemic Species Hypothesis, Native Lineage Hypothesis) to explain the native origin of Llano River Carpsucker and further assess whether the taxon is nonnative
C. cyprinus
(i.e., Species Introduction Hypothesis), each carrying vastly different conservation and management implications. Additionally, we assessed phylogenetic relationships across the entire genus Carpiodes. Phylogenetic analyses recovered divergent lineages of
C. cyprinus
in Eastern Gulf of Mexico drainages, suggesting the presence of cryptic undescribed species. Llano River Carpsucker specimens were resolved in unique lineages relative to
C. cyprinus
, with mitochondrial haplotypes closely related to Mississippi
C. cyprinus
(p‐distance < 0.005). Our study suggests Llano River Carpsucker represent native
C. cyprinus
, supporting our Native Lineage Hypothesis. We further provide evidence that
C. cyprinus
readily hybridizes with
C. carpio
, resulting in mitochondrial introgression across much of their distribution. Lastly, we provide recommendations to promote conservation efforts and discuss further research directions to understand deeper evolutionary and environmental mechanisms behind morphologically and genetically unique
C. cyprinus
inhabiting Western Gulf of Mexico drainages of Texas.

Our study investigates both distribution‐wide and within‐Texas genetic patterns of a group of fishes in need of greater taxonomic research (Catostomidae: Carpiodes). We recovered lineages of Carpiodes in the southeastern United States that are likely cryptic undescribed species and concurrently identify the native and taxonomic status of a uniquely shaped Carpiodes predominantly inhabiting the Texas Hill Country ecoregion.