Quantifying mating success of territorial males and sneakers in a bower-building cichlid fish

I S Magalhaes,A M Smith,D A Joyce

doi:10.1038/srep41128

Abstract

The strategies and traits males evolve to mate with females are incredible in their diversity. Theory on the evolution of secondary sexual characters suggests that evolving any costly trait or strategy will pay off and stabilise in the population if it is advantageous compared to the alternative less costly strategy, but quantifying the relative success of the two can be difficult. In Lake Malawi, Africa, there are >200 species of cichlid fish in which the males form leks and spend several weeks per year building sand-castle “bowers” several times their size. We tested the idea that a less costly “sneaking” strategy could be successful by quantifying the mating success of bower-holding versus non-bower-holding males. We PIT-tagged every fish in a semi-natural experimental set-up and placed tag-readers on the side of bowers to determine which fish held a bower. We then genotyped the eggs removed from females’ mouths to assign paternity of each egg. Broods were fathered by up to 3 different males. Although paternity was mostly assigned to males that held a bower, a small number of males who did not own a bower were more successful than some of those that did, indicating a role for an alternative strategy in these bower builders.

Highlights

The strategies and traits males evolve to mate with females are incredible in their diversity
Male mating success in leks is typically skewed towards a small number of individuals, with high social dominance[3], or a more central position[4], yet the skew varies according to lek size
One outcome of strong competition for mates is the development of alternative reproductive tactics (ARTs)[5,6,7]

Summary

Introduction

The strategies and traits males evolve to mate with females are incredible in their diversity. We used a species of bower-building haplochromine cichlid (Nyassachromis cf microcephalus) from Lake Malawi to quantify the prevalence and relative success of ARTs in a lekking fish species, and test the hypothesis that males who invest in building and defending a bower have higher reproductive success than those that don’t. 200 species of bower-building haplochromine cichlid have evolved in the last ~5 million years in Lake Malawi[11,12] These species congregate in leks, and build and defend sand-castle structures, termed “bowers” because of their apparent lack of utility beyond male signalling, analogous to the structures of bower birds. They are mouth-brooding cichlids; females spawn and pick up the eggs in their mouth, while males www.nature.com/scientificreports/. Bowers tend to be species specific, and are used in both direct female choice[13,14,15], and male-male signalling[16,17,18]

Methods

Results

Conclusion