Current Zoology, 2018, 64(3), 321–322 doi: 10.1093/cz/zoy037 Advance Access Publication Date: 3 May 2018 Editorial Editorial Male mate choice, female competition, and female ornaments as components of sexual selection Ingo SCHLUPP* Department of Biology, University of Oklahoma, Norman, OK 73019-0390, USA *Address correspondence to Ingo Schlupp. E-mail: firstname.lastname@example.org. Choosing a mate is likely one of the most influential decisions any male fitness directly depends on female fitness, and most reductions individual makes because it heavily influences their fitness. Going of female fitness are also costly to males. The limited existing litera- back all the way to the seminal work by Darwin (1871, 1859), we ture is reviewed and summarized by Fitzpatrick and Servedio mostly think of females as choosing mates, whereas males compete (2018). One of the important conclusions is that genetic constraints, over mating opportunities with females. This view is very well sup- mainly via pleiotropy can be powerful. Another key conclusion from ported, but somewhat incomplete. As Darwin struggled to find a their work is that we know too little about the effects of male mate good explanation for the existence of ornamental traits in males, he choice on the evolution of female ornaments. This article will pro- proposed Sexual Selection and along with that theory he suggested 2 vide excellent guidance for future studies, both empirical and theor- mechanisms that could lead to and maintain such extreme traits: etical. Clearly, male mate choice is not simply the inverse of female Female Choice and Male Competition. Historically, male competi- choice. Conceptually, male mate choice is not only connected to female tion was quickly accepted, whereas acceptance of female choice was delayed until much later, coinciding with the rise of modern femin- mate choice, but also relevant to our understanding of female– ism (Zuk 1993). female competition, and female ornamentation. Although ornamen- Later, germane work by Bateman (1948), Trivers (1972), and tation in females may be due to pleiotropy, it can also evolve in Lehtonen et al. (2016) established that the early investment into response to male mate preferences. Two studies in the Special gametes is extremely important in defining what is known as “sex Column discuss such scenarios. One study by Weiss and Dubin roles.” In a nutshell, males invest very little into individual gametes (2018) investigates how male Sceloporus lizards adjust reproductive as compared to females, which make very strong investments into effort based on ornament size in females. The effects are subtle, but their eggs. This concept of ‘sex roles’ has created a somewhat binary males do base their decision to engage in male–male competition on view of a phenomenon that is actually quite continuous (Ah-King the perceived reproductive benefit provided by females. The other and Ahnesjo ¨ 2013). Consider investments into offspring made by study is by Yong et al. (2018) and investigates the relationship of fe- males after fertilization of the eggs. In some cases this has led to the male ornamentation and female aggression in two populations of evolution of “sex role” reversal, where the males act choosy, and sticklebacks. Interestingly, the expression of the ornament (red col- females compete over males (Berglund and Rosenqvist 2003). In less oration) does not correlate directly with female aggression. Both pronounced cases, however, males may also invest into their off- studies are important as they raise relevant new questions. spring, which may lead to the evolution of choosiness in males. But Another female trait that might be influenced by male mate this is not the only scenario for the evolution of male mate choice, choice is female competition. Of all the aspects connected with male mate choice, this might be hardest to grasp. Just like male mate and one relatively often reported phenomenon is the presence of male mate choice when females differ strongly in quality (Edward choice is not simply the inverse of female mate choice, female com- and Chapman 2011). In this case male mate choice might even petition appears to be more indirect, at least apparently, and typical- evolve when males contribute nothing but sperm to their offspring. ly lacks the open fights that characterize male–male competition. The theoretical literature on male mate choice is by far not as The same principle might be behind this: if female viability is imper- well developed as the one on female choice. One aspect that I find iled, such traits may be difficult to evolve. By contrast, females particularly important is that—in contrast to the evolutionary im- compete with each other for many resources, including males, but pact of female choice on males—it is unlikely that traits in females such interactions may be difficult to measure and hard to observe evolve to be detrimental to females, as many ornaments are in males (Heubel and Plath 2008). In a paper on a small fish, the common (Fitzpatrick and Servedio 2017, 2018). This seems to be because goby, Heubel (2018) elucidates how females respond to female V C The Author(s) (2018). Published by Oxford University Press. 321 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact email@example.com Downloaded from https://academic.oup.com/cz/article-abstract/64/3/321/4992021 by Ed 'DeepDyve' Gillespie user on 21 June 2018 322 Current Zoology, 2018, Vol. 64, No. 3 the discussions were lively, engaged, and open. I am very grateful to all of competition for large, nest holding males. Her work especially high- them. I also am deeply grateful to the organizers of the Behaviour conference, lights the role of the operational sex ratio as a crucial factor in mate who hosted the symposium. They created a warm and friendly atmosphere choice and female competition. that allowed for the delightful and productive interactions we had. Another paper—also on gobies—by Amundsen (2018) reports a similar effect. The operational sex ratio in another small fish, the two-spotted goby, is key to a functional sex role reversal over the References breeding season. This mating system is characterized by an over- Ah-King M, Ahnesjo ¨ I, 2013. The “Sex Role” concept: an overview and evalu- abundance of males early in the season. Late in the season, however, ation. Evol Biol 40:461–470. females become more abundant and compete for males (Borg et al. Amundsen T, 2018. Sex roles and sexual selection: lessons from a dynamic 2006). This is remarkable because it provides an insight into a tem- model system. Curr Zool 64:363–392. poral dynamic that might be much more widespread, but difficult to Bateman AJ, 1948. Intra-sexual selection in Drosophila. Heredity 2:349–368. observe. This mating system may provide an especially elegant ex- Berglund A, Rosenqvist G, 2003. Sex role reversal in pipeﬁsh. Adv Study planation for the presence of ornaments in both sexes. Behav 32:131–167. Finally, in my own paper (Schlupp 2018), I review male mate Bonduriansky R, 2001. The evolution of male mate choice in insects: a synthe- choice in a group of fishes that shows no male parental investment, sis of ideas and evidence. Biol Rev 76:305–339. livebearing fishes (Poeciliidae). Somewhat surprisingly male mate Borg AA, Forsgren E, Amundsen T, 2006. Seasonal change in female choice choice is widespread in that taxonomic group, and seems to be most- for male size in the two-spotted goby. Anim Behav 72:763–771. ly associated with differences in female quality. Overall, males seem Darwin C, 1859. The Origin of Species. London: John Murray. Darwin C, 1871. The Descent of Man. London: John Murray. to prefer larger, more fecund females. One point I am trying to Edward DA, Chapman T, 2011. The evolution and signiﬁcance of male mate make in this context is that apparently similar preferences can be choice. Trends Ecol Evol 26:647–654. present in females and males, but their evolutionary origin may be Fitzpatrick CL, Servedio MR, 2017. Male mate choice, male quality, and the different. Consider the widespread preference for larger size found potential for sexual selection on female traits under polygyny. Evolution 71: in both males and females. In the case of female choice this prefer- 174–183. ence is often interpreted in the context of indirect benefits, in par- Fitzpatrick CL, Servedio MR, 2018. The evolution of male mate choice and fe- ticular in polygamous species. By contrast, male preferences for male ornamentation: a review of mathematical models. Curr Zool 64: larger females are typically viewed as a direct benefit to males via 323–333. higher fecundity found in larger females. I think this makes com- Heubel K, 2018. Female mating competition alters female mating preferences parative studies of female and male preferences especially interest- in common gobies. Curr Zool 64:351–361. ing. I feel that more studies looking at mate choice in both sexes of Heubel KU, Plath M, 2008. Inﬂuence of male harassment and female competi- a species using the same experimental method would be great tion on female feeding behaviour in a sexual-asexual mating complex of (Ptacek & Travis 1997; Justus and Mendelson 2018). mollies (Poecilia mexicana, P. formosa). Behav Ecol Sociobiol 62: The present Special Column provides glimpses of the phenomena 1689–1699. Justus K, Mendelson TC, 2018. Male preference for conspeciﬁc mates is stron- associated with male mate choice and hopefully creates a more hol- ger than female’s in Betta splendens. Behav Process 151:6–10. istic view of mate choice and sexual selection in general. Due to my Lehtonen J, Parker GA, Scha ¨ rer L, 2016. Why anisogamy drives ancestral sex own research interests and limitations, the articles compiled here are roles. Evolution 70:1129–1135. taxonomically very biased toward vertebrates, but there is exciting Ptacek MB, Travis J, 1997. Mate choice in the sailﬁn molly Poecilia latipinna. work done on many other taxa. The literature on insects, for ex- Evolution 51:1217–1231. ample, is nicely summarized by Bonduriansky (2001). Maybe, we Schlupp I, 2018. Male mate choice in Livebearing ﬁshes: an overview. Curr are able to stimulate future research, both theoretical and empirical, Zool 64:393–403. into the topics presented here. I think the most important aspect to Trivers R, 1972. Parental investment and sexual selection. In: Campbell B, understand more fully is how male and female mate choice as well editor. Sexual Selection and the Descent of Man. Chicago: Aldine. as male and female competition interact to produce the outcomes 139–179. we observe in nature, especially mutual mate choice. Weiss SL, Dubin M, 2018. Male mate choice as differential investment in contest competition is affected by female ornament expression. Curr Zool 64:335–344. Acknowledgments Yong L, Lee B, McKinnon JS, 2018. Variation in female aggression in 2 threes- pined stickleback populations with female throat and spine coloration. Curr Many of the contributors of this special column met in the summer of 2017 Zool 64:345–350. for a symposium in Estoril, Portugal. The title of the symposium was Zuk M, 1993. Feminism and the study of animal behavior. Bioscience 43: “Integrating Male Mate Choice, Female Competition, and Female Ornaments” and the participants and discussants lived up to the expectations: 774–778. Downloaded from https://academic.oup.com/cz/article-abstract/64/3/321/4992021 by Ed 'DeepDyve' Gillespie user on 21 June 2018
Current Zoology – Oxford University Press
Published: May 3, 2018
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera