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Apparent Homosexual Behaviour in an All-female Population of a Lizard, Lepidodactylus lugubris and its Probable Interpretation

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A case of apparent homosexual behaviour between female lizards is described and photographed in an all-female, parthenogenetic population of Lepidodactylus lugubris (Gekkonidae) in Hawau. Although other hypothetical explanations are offered, it appears most reasonable that this behaviour constitutes a demonstration of social rank. Briefly reviewed are homosexuality in lizards and the status of the L. lugubris population in Hawaii. Homosexuelles, kopulations-ähnliches Verhalten wurde unter Weibchen einer nur weiblichen, parthenogenetischen Population des tropischen Geckos Lepidodactylus lugubris auf der Insel Oahu, Hawaii, beobachtet. Die beobachtete und photographierte Haltung ähnelte der Kopulationshaltung der bisexuellen Geckos. Dies scheint die erste Mitteilung über Homosexualität weiblicher Echsen in der Natur zu sein. In diesem Fall scheint der Grund der Homosexualität nicht zu sein (1) das Nicht-Erkennen des Geschlechtes oder (2) Wirkung von männlichen Geschlechtshormonen, die wegen Hermaphroditismus oder teilweisem Geschlechtswechsel vorhanden sind. Anscheinend repräsentiert es auch nicht (1) eine Ersatz-Befriedigung, da das andere Geschlecht nicht vorhanden ist, oder (2) eine wirkliche Bevorzugung von Partnern desselben Geschlechts. Das homosexuelle Benehmen der “männlichen” Geckoweibchen scheint ihren sozialen Rang oder ihre territoriale Überlegenheit zu demonstrieren, wie bei manchen anderen Vertebraten.
... Same-sex mounting occurs in many species, and many hypotheses have attempted to explain this behavior (e.g. Werner 1980;Shine et al. 2000;Field and Waite 2004;Switzer et al. 2004;Levan et al. 2009;Bailey and Zuk 2009). Adaptive hypotheses attribute same-sex mounts to some adaptive value, such as to establish dominance or hierarchies (intrasexual conflict hypothesis: e.g., Werner 1980;Preston-Mafham 2006), while non-adaptive hypotheses mainly consider same-sex mounts to be caused by failure in sex discrimination (mistaken identity hypothesis: e.g., Barlow 2000;Marco and Lizana 2002), lack of opposite sex, strongly biased sex ratio (opposite-sex deprivation hypothesis: Shine et al. 2003;Field and Waite 2004;Switzer et al. 2004;Poiani 2010), or poor adaptation to an unfamiliar environment, such as captivity (maladaptation hypothesis: Bagemihl 1999). ...
... Werner 1980;Shine et al. 2000;Field and Waite 2004;Switzer et al. 2004;Levan et al. 2009;Bailey and Zuk 2009). Adaptive hypotheses attribute same-sex mounts to some adaptive value, such as to establish dominance or hierarchies (intrasexual conflict hypothesis: e.g., Werner 1980;Preston-Mafham 2006), while non-adaptive hypotheses mainly consider same-sex mounts to be caused by failure in sex discrimination (mistaken identity hypothesis: e.g., Barlow 2000;Marco and Lizana 2002), lack of opposite sex, strongly biased sex ratio (opposite-sex deprivation hypothesis: Shine et al. 2003;Field and Waite 2004;Switzer et al. 2004;Poiani 2010), or poor adaptation to an unfamiliar environment, such as captivity (maladaptation hypothesis: Bagemihl 1999). Although same-sex mounts are well-studied in some animals, such as birds and mammals (MacFarlane et al. 2006;Bailey and Zuk 2009), very little is known on this behavior in turtles and tortoises. ...
Article
Same-sex mounting is an aspect of animal behavior that has received increased attention in recent years in an attempt to improve our limited understanding of the possible causal mechanisms. Here, to our knowledge, we review for the first time same-sex mounting in turtles and tortoises. To this end, we have compiled data on same-sex mounts in 13 chelonian species and discuss the data together with those hypotheses most commonly raised in turtle studies, namely, the intrasexual conflict, maladaptation, mistaken identify, and opposite-sex deprivation hypotheses. Compilation of the data revealed that in almost every species with reports of same-sex mounting there were dominance relationships mediated by aggressive/submissive interactions; most of these cases occurred in captivity, and the sex ratios were not skewed. We discuss future research directions, providing initial ideas of experimental testing on each hypothesis, in the hope of directing more research effort to this field.
... Aaron Bauer and Dan Scantlebury. All agreed that the lizards in question were Mourning Geckos, Lepidodactylus lugubris (Duméril and Bibron 1836), a non-native parthenogenetic gekkonid native to the tropical Pacific (e.g., Werner 1980;Krysko and Krysko 2016). ...
... E mpirical observations of SSB (that is, any attempted sexual activity between two or more members of the same sex) in animals are widespread 1-4 , with evidence of SSB in mammals 5-9 , birds 10-14 , arthropods 15-19 , molluscs 20-22 , echinoderms 23-25 and other animals [26][27][28][29][30] . Since SSB is traditionally thought to be deleterious, as same-sex matings require energy expenditure but cannot produce offspring, there has been much interest in understanding its origin and maintenance 1-5 . ...
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The widespread presence of same-sex sexual behaviour (SSB) has long been thought to pose an evolutionary conundrum, as participants in SSB suffer the cost of failing to reproduce after expending the time and energy to find a mate. The potential for SSB to occur as part of an optimal strategy has received less attention, although indiscriminate sexual behaviour may be the ancestral mode of sexual reproduction. Here, we build a simple model of sexual reproduction and create a theoretical framework for the evolution of indiscriminate sexual behaviour. We provide strong support for the hypothesis that SSB can be maintained by selection for indiscriminate sexual behaviour, by showing that indiscriminate mating is the optimal strategy under a wide range of conditions. Further, our model suggests that the conditions that most strongly favour indiscriminate mating were probably present at the origin of sexual behaviour. These findings have implications not only for the evolutionary origins of SSB, but also for the evolution of discriminate sexual behaviour across the animal kingdom.
... Este gecko puede emitir llamados de múltiples clics durante contextos sociales (Hunsaker y Breese 1967, Frankenberg 1982b; Petren y Case 1998). Estos llamados son emitidos en interacciones entre hembras durante el cortejo homosexual, el cual puede ir acompañado de pseudocópulas (Werner 1980, Frankenberg 1982b. Cabe recordar que L. lugubris es una especie partenogenética que presenta poblaciones que casi en su totalidad son hembras (Cuéllar y Kluge 1972, Yamashiro et al. 2000. ...
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Lizards mainly depend on chemical and visual signals to communicate and, to a lesser extent, on acoustic signals, so generally it has been considered that these reptiles do not emit sounds. However, representatives of different lizard families can emit sounds through their mouths and in different contexts. In Chile, the reports on the emission of sounds in lizards are scarce and anecdotal, and in very few cases, these acoustic signals have been studied in detail. However, the knowledge about sound emissions of some species of native lizards from Chile has increased during the last few years. The goal of this review is to define the state of the art on the emission of sounds in native lizards of Chile as well as to encourage the development of research related to this particular communication modality. For this, we made an exhaustive compilation of the existing information on this topic. Of the 121 species of native lizards in Chile, there are reports of sound emission for only 13 species (10.7%) of the genus Diplolaemus, Garthia, Lepidodactylus, Liolaemus, Phyllodactylus, Phymaturus and Pristidactylus. Most of these species emit sounds in predation contexts, probably for the purpose of deterring the attack of a predator. We discuss several aspects that should be considered for the future studies about lizard sounds.
... data). Pseudocopulation between two L. lugubris has been reported (Werner 1980; McCoid and Hensley 1991), although it was not witnessed in a total of 37 h of experimentally staged interactions (Bolger and Case 1992;Hanley et al. 1994). One way to determine whether a gecko's genotype influences its susceptibility would be to examine rates of mite infestation of formerly heavily and lightly infested individuals under common conditions and then test the rate of mite infestation in their offspring (BulI pers. ...
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We examined the hypothesis that pseudosexual behaviour facilitates reproduction in the unisexual gecko, Lepidodactylus luguhris. Thirty-eight hatchlings were housed in isolated or social conditions. Age at initial egg development, days between egg development and laying for the geckos’first three clutches of eggs, inter-clutch intervals and dominance behaviours were recorded. Lepidodactylus lugubris developed their first clutch of eggs at about 9·5 months of age after their endolymphatic sacs became externally visible. The geckos laid their eggs about 28–30 days later with smaller geckos requiring more time between egg development and laying than larger geckos. Grouped geckos formed dominance hierarchies. In the triad and quadrad groups, the subordinate geckos’growth rates were slowed and their fecundity was suppressed. Pseudosexual behaviour was not observed in the geckos and was unrelated to fecundity because isolated geckos developed and laid three clutches of eggs at the same rate as grouped geckos. Dominance behaviour, not pseudosexual behaviour, was related to fecundity in L. lugubris. Dominance behaviour may facilitate dispersal in this colonizing species because subordinate geckos could increase their fecundity by moving to less populated areas.
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The main features of the hybrid theory can best be summarized by some of its principal exponents: "The hypothesis entails two to three major steps. The initial step is the same as in all cases--the hybridization of diploid bisexual species to produce a diploid parthenoform, Second, if this diploid parthenoform is adequately adapted and an available habitat is present, it colonizes the habitat as a diploid parthenospecies .... The diploid parthenoform backcrosses to one or the other, or both, of the generating diploid bisexual species... to form an allotriploid parthenoform. Again, if this form is able to invade and capture a habitat, then the result is an allotriploid parthenogenetie species" (Wright and Lowe 1968). Thus: "Hybridization diploid unisexuality and then polyploidy are the natural sequence of events, with unisexual populations sustaining themselves by one of the three types of clonal reproduction" (hultz 1969). Finally: "It is further speculated that the formation of unreduced eggs in a diploi...
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Conclusion The original hypothesis thatLepidodactylus lugubris is parthenogenetic is strongly supported by the following data: disparate sex ratio (only 4 individuals with mae characteristics among a total of 673 examined), absence of courtship in reproductively mature females, and acceptance of skin homografts. The chromosome number ofL. lugubris is about 44, and very likely a diploid complement. It seems very unlikely that gynogenesis is the mode of parthenogenesis inL. lugubris owing to the absence of congeners and even species in closely related genera throughout much of its geographic range. The meiotic mechanism and the origin of the males is being further investigated by us.
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