Larger swordtail females prefer asymmetrical males

Abstract

Many organisms, including humans, find symmetry more attractive than asymmetry. Is this bias towards symmetry simply a by-product of their detection system? We examined female preference for symmetry of the pigment pattern vertical bars in the swordtail fishes Xiphophorus cortezi and Xiphophorus malinche . We found a relationship between preference for symmetry and female size, with larger and thus older females spending significantly more time with the asymmetrical video animation as compared to the symmetrical video animation. The preference for asymmetry we report demonstrates that even if females can detect symmetrical males better, this does not preclude subsequent selection on females to prefer symmetrical or asymmetrical males. In addition, because the preference was correlated with female size, past studies may have missed preference for either asymmetry and/or symmetry by not examining the relationship between female preference and size/age or by measuring a limited size/age distribution of females. In both of the species of swordtail fishes examined, a high proportion of males are asymmetrical by more than one bar. We suggest that female preference may be maintaining fluctuating asymmetries in these fishes.

Chapter 5 Insights for Behavioral Ecology from Behavioral Syndromes

“…For example, some females like symmetrical males while others like asymmetrical ones (Morris et al, 2006). Some females copy the preferences of other females while others rely on their own assessment of males.…”

“…Some females copy the preferences of other females while others rely on their own assessment of males. The obvious syndrome question is whether there is something else distinctive about females with different preferences, apart from obvious attributes such as size (Morris et al, 2006) or age. In the particular situation where females engage in sexual cannibalism, individual females differ in their tendency to attack males versus mate with them (Johnson and Sih, 2005).…”

Inbreeding avoidance through non-random mating in sticklebacks

“…The risk of inbreeding in sticklebacks is high in newly established and small populations (Heckel et al 2002;Aeschlimann et al 2003). Inbred sticklebacks have greater body asymmetries making them less attractive as mating partners (Mazzi et al 2003; but see Morris et al 2005). Inbred eggs have a lower fertilization and hatching rate compared to outbred fishes, and fewer survive to reproductive age ( J. G. Frommen 2005, unpublished data).…”

Expression Patterns of Neuroligin-3 and Tyrosine Hydroxylase across the Brain in Mate Choice Contexts in Female Swordtails

“…In X. nigrensis , females prefer larger size class males over the small size class males that use forced copulation tactics [Ryan et al, 1990;Cummings and Mollaghan, 2006], and the strength of this preference changes with female age . Experience-dependent changes in female mate preference have also been demonstrated in other poeciliid species [Morris et al, 2006;Rios-Cardenas et al, 2007;Verzijden and Rosenthal, 2011], suggesting that learning is a common component of mate choice across poeciliids. Swordtail females only need visual information to display these preferences [Ryan and Rosenthal, 2001], and swordtail preferences in the laboratory lead to actual copulation in both the lab and the wild [Ryan et al, 1990;Walling et al, 2010].…”