Testes mass in the livebearing fish Brachyrhaphis rhabdophora (Poeciliidae) varies hypoallometrically with body size but not between predation environments

Keywords

body size, Brachyrhaphis rhabdophora, gonadosomatic index, life history, Poeciliidae, predation environment effects

Abstract

In this study, we considered potential causes of variation in testis size in the livebearing fish Brachyrhaphis rhabdophora. We evaluated variation in testes mass among individual males and among populations that occupy different selective environments. First, we predicted that small males should allocate more to testes mass than large males (i.e., hypoallometric pattern) based on a sperm competition argument. Second, based on life history theory and associated differences in mortality rates between populations that coexist with many fish predators and those with few predators, we predicted that males in high-predation environments should allocate more to testes mass than males in habitats with few predators. Our results showed that small males allocated proportionally more to testes mass than larger males (slope of testes mass to body mass was hypoallometric). However, there was no effect of predator environment on testes mass independent of body size differences. In this system, size-specific patterns of reproductive allocation in males (hypoallometry) differ from that seen in females (hyperallometry). Allocation to testes mass may respond to differences in mortality rate through selection on body size.

Original Publication Citation

Brown HN, B Gale, JB Johnson, MC Belk. 2018. Testes mass in the livebearing fish Brachyrhaphis rhabdophora (Poeciliidae) varies hypoallometrically with body size but not between predation environments. Ecology and Evolution 8: 11656-11662.

Document Type

Peer-Reviewed Article

Publication Date

2018-11-08

Permanent URL

http://hdl.lib.byu.edu/1877/8130

Publisher

Ecology and Evolution

Language

English

College

Life Sciences

Department

Biology

University Standing at Time of Publication

Full Professor

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