Although intrasexual competition among males is known to be an important de- terminant of male mating success in lizards, less is known about what role the mate choice component of sexual selection may play in determining male and female mating success. The purpose of this review was to consider the evidence for mate choice in lizards. The issue of whether females in territorial species choose where to reside, and thus mating partners, based on the availability of resources or on male phenotypic traits is largely unresolved in most species. There is, however, good empirical evidence for at least one territorial species that the availability of resources is a more important factor than male phenotypic traits in determining where females reside, and thus their mating partners. Although male body size is known to be a key factor determining male mating success in lizards, only one study of female mate choice has found a significant relationship between female mating preferences and male body size. The best evidence for the importance of male phenotypic traits in female mate choice comes from studies of Anolis lizards that demonstrate that female mating preferences are affected by male display behavior. Findings from studies of female mate choice in lizards support Halliday's causal model of female mate choice and Ryan's sensory exploitation hypothesis, but not the Hamilton and Zuk hypothesis. Finally, a male mating preference for unfamiliar females has been reported in two highly territorial species.
Extension and retraction of the throat fan or dewlap is one of the most conspicuous aspects of display behavior of male Anolis lizards. Although dewlap display plays a role in species recognition, signal detection, and even predator defense, the importance of the male dewlap in male mating success in nature has not been established. The present study tested whether the display of the dewlap by males of Anolis sagrei affected the mating success of free-ranging males. We compared the number of males that copulated and their copulation rates between two groups: experimental males that were surgically prevented from extending their dewlaps and control males that were sham treated. Experimental and control groups did not differ significantly in the proportion of males that copulated or in copulation rate. These results do not support the hypothesis that the male dewlap affects male mating success in A. sagrei. If the male dewlap does have an effect on male mating success in this species, then the effect was too subtle to be detected by our study.
Both luteinizing hormone-releasing hormone (LHRH) and thyrotropin-releasing hormone (TRH) induce sexual receptivity in ovariectomized, estrogen-primed female lizards (Anolis carolinensis). Ovariectomized females pretreated with three daily injections of a subthreshold dose (0.2 micrograms) of estradiol benzoate were administered either 500, 1,000 or 1,500 ng of LHRH, or 1,000 ng of TRH 48 h following the last estrogen pretreatment injection. Hormone-treated females exhibited significantly higher sexual receptivity scores than controls when tested 2, 4, 6 and 24 h post-injection. Female sexual receptivity scores in females that were administered 500 ng of LHRH or 1,000 ng of deamido TRH were, however, no different than control scores at these test times. The observed ability of LHRH to increase female sexual receptivity is consistent with previous results in birds and mammals. The ability of TRH to increase female sexual receptivity is a novel finding that may underscore differences in neuroendocrine regulation of vertebrate estrous behavior.
The importance of androgens in the ability of male lizards to acquire a territory was tested by determining whether male brown anoles, Anolis sagrei, treated with the anti-androgen, cyproterone acetate (CA), were less successful in acquiring a 'high-quality' habitat patch in an outside enclosure than placebo-treated males of similar size. The habitat patch had a tree for perching, ornamental plants and twigs for refuge, and three females for mating partners. Reproductively active males were treated for 21 days with either CA (0· 1 mg/day) or placebo, both delivered from subcutaneously placed pellets. On day 21, a CA-treated male and a placebo-treated male were placed into the enclosure (6·0 m2). Two hours later, the behaviour and location of the males were monitored for a 30-min period. In tests of 20 pairs, significantly fewer CA-treated males headbob displayed to their male pair-mate, showed the static display modifier of crest erection, and courted females than placebo-treated males. In addition, CA-treated males spent significantly less time in the high-quality habitat patch and less time perched on the tree than did placebo-treated males; they also had significantly less time of exclusive use of these areas. Males treated with CA also perched lower in the habitat than did placebo-treated males. These results suggest that androgens may play an important role in the ability of male A. sagrei and perhaps other lizards to acquire a territory.
Prostaglandins (PGs) have been implicated in the mediation of sexual behavior in vertebrates. In this study, the effects of administered PGs on sexual receptivity were examined in the ovariectomized female green anole lizard (Anolis carolinensis). Injection (ip) of 15 microgram PGF2 alpha failed to induce sexual receptivity in nonreceptive females which were either untreated or estrogen primed. On the other hand, PGF2 alpha treatment of sexually receptive estrogen-pretreated females inhibited sexual receptivity 1 h post injection. A dose of 7.5 microgram PGF2 alpha was as effective as 15 microgram in inhibiting sexual receptivity, while a dose of 1.5 microgram was near the minimum effective level. Treatment with 15 microgram PGE2 and, to a lesser extent, PGE1 also reduced sexual receptivity. In contrast, arginine-8-vasotocin, a neuropeptide capable of stimulating smooth muscle contractions in reptiles, did not decrease sexual receptivity. The inhibitory effects of PG treatment observed at 1 h were diminished by 3 h and were no longer present 6 and 24 h post injection, with females, again, being fully receptive. Inhibition of sexual receptivity occurs very rapidly after PGF2 alpha treatment. When tested 5 min post injection, all females treated with 15 microgram arginine-8-vasotocin were sexually receptive. The oviducts were not required for PGF2 alpha inhibition of sexual receptivity, as sexual receptivity was inhibited in oviductectomized females 1 h after the injection of 15 microgram PGF2 alpha. The inhibitory action of PGF2 alpha was also observed when sexually receptive females were injected intracranially rather than ip. Intracranial injection of 3.8 microgram PGF2 alpha inhibited sexual receptivity in females tested 1 h post injection. These results indicate that exogenous PGs, possibly acting centrally within the brain, inhibit sexual receptivity in female A. carolinensis, a species with a rapid mating-induced termination of sexual receptivity.
