Do coercive males tradeoff mating for competition when

Do coercive males trade-off mating for competition when faced with multiple competitors? Hufsa Ali, Dr. Raelynn Deaton Haynes Department of Biological Sciences St. Edward’s University

Male-Male Competition

Introduction ● Poeciliid family o o live-bearing fish internal fertalization → sexual selection

Introduction ● Gambusia genus o G. affinis § coercive mating system

Understanding the Mating System ● Primarily coercive mating rather than courtship behaviors. ● Female resistence.

Understanding the Mating System: Size Source: Deaton, et al.

Understanding the Mating System Persistence of smaller males → reproductive success among smaller males. ● Male size → mating techniques o o Aggressive vs. sneaky copulation

Study Objectives ● Determine male density threshold at which large male advantage begins to break down. ● Size matching. ● Identify density at which males become primarily concerned with competing rather than with mating.

Predictions Mating Behaviors • Trade-off between mating and competition comp matin g Competitor Density

Predictions • Trade-off between mating and competition. • Point at which large-male competition allows small male mating.

Behaviors • • Chasing Bites and nips Gonopodial displays Gonopodial thrusts

Method • Behavior observations in social situations with varying male density. • Tracked aggressive and mating interactions of single males across all densities, towards both female and other males. • Looked for behavioral trends correlating to density changes.

Method

Results • Mating behaviors decrease with increasing male density.

Results • Aggressive behaviors among males does not change.

Results • No indication of trade-off between behaviors.

Results r 2=0. 28, df=83, p<0. 001 • Strong correlation between mating and competition behaviors as density increases. r 2=0. 46, df=83, p<0. 001

What does this mean? • There is no trade-off between mating behaviors and inter-male aggression. There is a correlation between occurrences of both behavior types. • The density at which this behavior trade-off occurs has not been tested yet.

Future Work • Continue current experiments on trade-off threshold with larger densities. • Size-ratio study. • Both studies on sister species, G. geiseri.

Acknowledgements ● ● ● TG Public Benefit Grant Program Dr. Raelynn Deaton Haynes Dr. Richard Kopec James Stewart Jacqueline Chisolm Aaron Haynes