Abstract
Size-assortative mating and sexual selection on size are common across species. Since both may be a result of mate choice, mate choice based on size should also be a widespread process. This behaviour is, however, rarely studied directly and thus the biological causes that determine size-based mate choice are poorly understood. To address this, we studied the size-based mate choice in an intertidal snail, Echinolittorina malaccana, that has been used as a model to understand this process. Previous studies, assuming a quantitative Gaussian mating preference function, have inferred that mate choice in this snail is caused by a size similarity mechanism (males prefer to mate with females slightly larger than themselves). To further test and quantify this proposed mechanism, we conducted mate choice experiments with alternative designs (single, male and multiple choice) in the laboratory and compared the results to mate choice data observed in natural populations. This integrated approach allowed us to elucidate the mechanism of mate choice by evaluating alternative mating models that best fitted the observed data of various designs. Results confirmed the similarity-based mechanism but showed deviations at extreme size classes. The single choice design indicated that mate choice was exercised during one-on-one male–female interactions, but the strength of mate choice increased with the presence of additional individuals (males in the male choice design, and both males and females in the multiple-choice design). Multiple-choice experiments are, therefore, the most valuable and useful design to infer how males choose mates in the wild, as they best mimic the natural scenario and the results are the most similar to those observed in natural populations. To elucidate the mechanisms causing this male choice for particular female sizes, the next steps are to identify the genetic basis as well as potential physiological benefits associated with choosing slightly larger females.
Highlights
Size-assortative mating and sexual selection on size are common across species
The single choice design indicated that mate choice was exercised during one-on-one maleefemale interactions, but the strength of mate choice increased with the presence of additional individuals
While the multiple-choice design represents the most realistic situation, using complementary, alternative mate choice designs allows us to disentangle the mechanisms of mate choice (Coyne et al, 2005; Dougherty & Shuker, 2015), especially when compared with data collected on the shore
Summary
Size-assortative mating and sexual selection on size are common across species. Since both may be a result of mate choice, mate choice based on size should be a widespread process. To further test and quantify this proposed mechanism, we conducted mate choice experiments with alternative designs (single, male and multiple choice) in the laboratory and compared the results to mate choice data observed in natural populations. This design is statistically robust as the data obtained are truly independent (Noor & Ortiz-Barrientos, 2006) With this approach, intrasexual competition cannot be estimated and even intersexual mate choice is considerably simplified (as only mechanisms that affect that particular male and female type are possible, for example, Knoppien, 1985), and mate choice is weaker under no-choice designs than under choice designs (Dougherty & Shuker, 2015). Certain multiple-choice designs have, been criticized because the different mating pairs observed may be statistically dependent (Noor & Ortiz-Barrientos, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
