University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Eileen Hebets Publications Papers in the Biological Sciences 4-2010 Female mate choice based upon male motor performance John Byers University of Idaho, [email protected] Eileen Hebets University of Nebraska - Lincoln, [email protected] Jeffrey Podos University of Massachusetts, Amherst, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/bioscihebets Part of the Behavior and Ethology Commons Byers, John; Hebets, Eileen; and Podos, Jeffrey, "Female mate choice based upon male motor performance" (2010). Eileen Hebets Publications. 45. https://digitalcommons.unl.edu/bioscihebets/45 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Eileen Hebets Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Animal Behaviour 79:4 (April 2010), pp. 771–778; doi: 10.1016/j.anbehav.2010.01.009 Copyright © 2010 The Association for the Study of Animal Behaviour; published by Elsevier Ltd. Used by permission. Submitted October 12, 2009; revised November 19, 2009; accepted January 11, 2010; published online February 19, 2010. Female mate choice based upon male motor performance John Byers,1 Eileen Hebets,2 and Jeffrey Podos 3 1. Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051, USA 2. School of Biological Sciences, University of Nebraska–Lincoln, Lincoln, NE 68588, USA 3. Department of Biology, University of Massachusetts, Amherst, MA 01003, USA Corresponding author — J. Byers, email [email protected] Abstract Our goal in this essay is to review the hypothesis that females choose mates by the evaluation of male motor performance. We define motor performance as vigor, the ability to perform energetically expensive acts repeatedly, or as skill, the ability to per- form difficult motor tasks well. Motor performance reflects most aspects of whole-organism performance that relate to survival, and thus should indicate, more reliably than ornaments do, individual male genetic quality and/or developmental history. Male sexual displays in many animal taxa contain elements of vigor and/or skill, and accumulating evidence suggests that females choose mates in nature based upon their evaluations of male motor performance. We note that male ornaments in many species are accompanied by conspicuous motor display, and we propose that ornaments often arise secondarily as a way to enhance the apparent skill or vigor of male motor performance. More and better methods to measure male vigor and skill are needed, as well as additional studies on the abilities of females to make discriminations of this type. Keywords: female mate choice, male display, motor performance, skill, vigor Charles Darwin (1859) proposed that many male sexual traits Puurtinen (2007) provide a more complete review of the history (ornaments and displays) evolve due to sexual selection by fe- of these ideas. male mate choice. In spite of initial resistance to Darwin’s pro- Nevertheless, there now seems to be widespread acceptance that posal, and a subsequent century of limited attention on the male ornaments are reliable indicators of male breeding value for topic (reviewed by Cronin 1991), the study of sexual selection offspring quality, and that the primary question about female mate currently stands front and centre within the field of animal be- choice concerns the origins and maintenance of preferences that re- havior. Empirical and theoretical work on sexual selection has sult in the evolution of exaggerated male ornaments. For example, traditionally focused on male ornaments, most famously the pea- in a terms-definition box in a recent issue of Trends in Ecology and Evo- cock’s (Pavo cristatus) tail. Sir Ronald Fisher (1930) developed lution, Tomkins et al. (2004, page 323) defined good genes as “mod- a verbal model of an evolutionary process by which ornaments els of sexual selection that assume that extreme ornaments indicate could evolve to become exaggerated, in spite of the expecta- the genetic quality of the bearer, defined as breeding value for fit- tion that such traits reduce the bearer’s survival ability. Subse- ness.” Or, consider Kirkpatrick’s (1987, page 45) widely cited formu- quently, Lande (1981) and Kirkpatrick (1982) developed mathe- lation: “Sexual selection by female choice involves two characters, a matical models of the Fisher idea, and a vigorous debate in the male secondary sexual trait and a female mating preference.” Data sup- literature followed on the question of whether ornaments evolve porting this model, however, are incomplete. Many researchers have via the Fisher runaway mechanism, which requires a genetic cor- indeed shown that females often prefer males with exaggerated or- relation between the magnitude of the male ornament and the naments (Andersson, 1989; Hill, 1990; Møller, 1991), and some stud- magnitude of the female preference, or alternatively whether or- ies have reported data on sire effects (i.e. showing that males with naments evolve as indicators of male breeding value for offspring more elaborate ornaments sire offspring with superior health, sur- quality. Critics of the indicator hypothesis noted that the asso- vival or developmental profiles; Petrie 1994). But, despite keen inter- ciation between male ornament size and male breeding value est on the topic for more than a quarter century, no published study would tend to decay, but supporters replied that the decay could has put these two lines of evidence together for a single species, to be avoided if male ornaments were condition dependent (Borgia, show that the free choices of females in nature create stabilizing or 1979; Taylor and Williams, 1981; Pomiankowski and Møller, 1995; directional selection for high values of male ornament expression, Rowe and Houle, 1996; Houle and Kondrashov, 2002). Kotiaho & and to show simultaneously that offspring quality is associated with 771 772 BYERS, HEBETS, & PODOS IN ANIMAL BEHAVIOUR 79 (2010) the selected values of sire ornament expression. Fannia canicularis (Land & Collett 1974), the leg-waving displays of Stepping back, the foundation for a broader view of sexual se- many wolf spiders (Hebets & Uetz 1999) and the energetically ex- lection by female choice was put forward 9 years before the Lande pensive waving of the enlarged cheliped in fiddler crabs, genus Uca paper, by Robert Trivers, who wrote: “As in other aspects of sex- (Salmon et al., 1978; Matsumasa and Murai, 2005). Additional exam- ual selection, the degree of male investment in the offspring is im- ples include the lengthy bouts of flying in some male bird displays portant and should affect the criteria of female choice. Where the (Mather & Robertson 1992), the sustained, energetically expensive male invests little or nothing beyond his sex cells, the female has vocalizations of many anuran amphibians (Prestwich, 1994; Welch only to decide which male offers the ideal genetic material for her et al., 1998) and of some ungulates (Wyman et al. 2008), sustained offspring…” (Trivers 1972, page 167). This view looks beyond or- stridulation in some orthoptera (Hedrick, 1986; Prestwich, 1994; naments per se; it predicts that sexual selection by female choice Prestwich and O’Sullivan, 2005), sustained flashing displays of fire- should occur wherever there is asymmetry in parental investment, flies (Lewis & Cratsley 2008) and persistence on leks by displaying and that females should evolve the ability to discriminate among males (Leuthold, 1966; Vehrencamp et al., 1989; Deutsch, 1994; Is- potential mates, using whatever information is available. Consider varan and Jhala, 2000). Indeed, one of the most striking aspects of the situation in mammals, where asymmetry in parental invest- many male mating displays is their repetitive nature. Certainly, the ment is extreme. With few exceptions (e.g. Bradbury 1977), male vigorous repetition of a display can serve other functions, such as re- mammals do not possess sexual ornaments analogous to the elon- pelling rivals, or simply increasing the likelihood of attracting a fe- gated tail feathers or brightly colored plumage of birds. In the few male, but to the extent that repetition is energetically costly, or to mammalian species in which males have some conspicuous col- the extent that repetition exposes the signaler to danger or risk of oration (Fernandez & Morris 2007), it is doubtful that the color- retaliation, it becomes a way in which the quality of males can be ation constitutes a character that is opposed by natural selection. compared. In addition, females may be able to assess vigor by ob- Many male mammals do possess characters that are associated serving male fighting and similar forms of competition, by indi- with intrasexual selection, such as weapons (Emlen 2008), large rectly detecting the outcome of male–male competition, or by incit- body sizes and pugnacious dispositions, but they do not possess ing male competition and selecting the winner (Cox and LeBoeuf, nonutilitarian ornaments that serve female choice. 1977; Byers et al., 1994; Bro-Jorgensen, 2002). In many lek-breeding The virtual absence of male ornaments in mammals forces one species, females prefer to mate with males that occupy territories at of two conclusions: either sexual selection by female choice does the spatial centre of the lek (Hoglund and Lundberg, 1987; Apollo- not occur in mammals, or alternatively, it does occur, but the crite- nio et al., 1992; Kokko et al., 1999; Isvaran and Jhala, 2000; Bro-Jor- ria by which females evaluate males involve something other than gensen and Durant, 2003). Here, to the extent that males compete ornaments. In this article, we review the evidence that, across a for central locations, the female preference is for vigor. wide range of taxa, females evaluate males largely based on male Studies on wolf spiders provide multiple lines of support for motor performance, especially within mating displays. This hy- the hypothesis that display vigor is used in mate choice.