So Long Sucker: Comparing Growth Rates among Purebred Suckers and their Hybrids in a Laboratory Setting

Authors: Lauren Mason-Sarantopulos, David Rogowski, Jan Boyer, Crosby Hedden

Year: 2021

Abstract

Flannelmouth Sucker (Catostomus latipinnis) and Razorback Sucker (Xyrauchen texanus) are two catostomids endemic to the Colorado River basin, and are known to hybridize with one another. Due to human altered river conditions (e.g., dams, water diversions, water withdrawals) and the introduction of nonnative species, many native fish populations within the Colorado River basin have declined. Razorback Sucker recruitment in the wild is low due to these stressors, and thus they have experienced largescale declines throughout the river. The scarcity of Razorback Sucker, and the rareness of conspecific mates, increases the probability of hybridization with the abundant Flannelmouth Suckers. Do hybrids have a competitive advantage over Razorback Sucker or Flannelmouth Suckers, and how might that affect the management and conservation of Razorback Suckers? We investigated the differences in growth rates between four progenies: Razorback Sucker, Flannelmouth Sucker, and their hybrids: Razormouth Sucker (RBS? x FMS?), and Flannelback Sucker (FMS? x RBS?), at two size classes: juveniles (< 130mm) and sub-adults (>130mm). Both juvenile and sub-adult hybrids grew faster than purebreds. For both size-classes combined, hybrid growth rates were 0.103 mm/day compared to 0.085 mm/day for Razorback Sucker and 0.058 mm/day for Flannelmouth Sucker. The presence of higher growth rates in hybrids suggests a life-history advantage exists in hybrids over purebred suckers, which could hinder the genetic integrity and recovery of the Razorback Sucker.