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Front. Ecol. Evol. | doi: 10.3389/fevo.2019.00007

Alternative mating tactics in socially monogamous prairie voles, Microtus ochrogaster.

 Stephen M. Shuster1*, Regina M. Willen2, Brian Keane2 and  Nancy G. Solomon2
  • 1Department of Biological Sciences, Northern Arizona University, United States
  • 2Department of Biology, Miami University, United States

ABSTRACT: Alternative mating tactics appear to evolve when sexual selection is strong. Because such conditions are usually observed in species with polygynous or polyandrous mating systems, alternative mating tactics in monogamous mating systems are seldom documented and are poorly understood. In prairie voles, Microtus ochrogaster, a species widely known for forming monogamous pair-bonds, the expression of territoriality within each sex is dimorphic, and includes non-territorial “wanderers” as well as territorial “residents.” To explore the variance in fitness, measured in offspring numbers, among breeding individuals expressing these alternative mating tactics, we compiled parentage data over three years for male and female prairie voles from natural populations in Indiana and Kansas, USA. We found that: (1) the average fitnesses of males and females within each population were identical when adjusted by the sex ratio; (2) the variance in fitness in male and female prairie voles was comparable to that of many highly polygynous species; (3) The average fitnesses of male tactics, and of female tactics, were equivalent within and among years within each location; (4) consistent with negative frequency-dependent selection acting on mating phenotypes, the between-tactic variance in fitness for male and female mating tactics decreased with increasing study duration; (5) consistent with negative assortative mating, resident males and wanderer females produced offspring primarily in monogamous partnerships, whereas wanderer males and resident females produced offspring primarily in polygamous partnerships. Our results show that the conditions necessary for the persistence of alternative mating tactics are indistinguishable from those for phenotypically less flexible alternative mating strategies, and that alternative mating tactics can evolve in both sexes in monogamous species when fitness variance within each sex is large.

Keywords: Opportunity for selection, Best of a bad job, Fitness variance, Fisher's principle, Negative frequency dependent selection, Equal average fitness

Received: 05 Jul 2018; Accepted: 09 Jan 2019.

Edited by:

Dustin R. Rubenstein, Columbia University, United States

Reviewed by:

Carl Soulsbury, University of Lincoln, United Kingdom
Matina C. Kalcounis-Rueppell, University of North Carolina at Greensboro, United States  

Copyright: © 2019 Shuster, Willen, Keane and Solomon. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Stephen M. Shuster, Department of Biological Sciences, Northern Arizona University, Flagstaff, 86011, Arizona, United States, stephen.shuster@nau.edu