摘要: We used Takydromus septentrionalis, a sexually size-monomorphic lacertid lizard, as a model system to test the hypothesis that sexual size monomorphism may evolve in lizards where reproductive performance is maximized at a similar body size for both sexes. We allowed lizards housed in laboratory enclosures to lay as many clutches (for females) as they could or to mate as many times (for males) as they could in a breeding season. Size-assortative mating was weak but evident in T. septentrionalis, as revealed by the fact that male and female snout-vent lengths (SVLs) in mating pairs were significantly and positively correlated. Mating frequency (indicative of male reproductive performance) varied from 1 to 8 per breeding season, generally increasing as SVL increased in adult males smaller than 67.4 mm SVL. Clutch frequency varied from 1 to 7 per breeding season, with female reproductive performance (determined by clutch frequency, annual fecundity, and annual reproductive output) maximized in females with a SVL of 68.0 mm. Accordingly to our hypothesis, the reproductive performance was maximized in the intermediate sized rather than the largest individuals in both sexes, and the body size maximizing reproductive performance was similar for both sexes. Future work could usefully investigate other lineages of lizards with sexually monomorphic species in a phylogenetic context to corroborate the hypothesis of this study.

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摘要: Cooperative breeding is a sophisticated altruistic social behavior that helps social animals to adapt to harsh environments. The Tibetan ground tit, Pseudopodoces humilis, is a high-altitude bird endemic to the Tibetan plateau. Recently, it has become an exciting system for studying the evolution of facultative cooperative breeding. To test for molecular adaptations associated with cooperative breeding, we resequenced the whole genome of ground tits from 6 wild populations that display remarkable variation in the frequency of cooperative breeding. Population structure analyses showed that the 6 populations were divided into 4 lineages, which is congruent with the major geographical distribution of the sampling sites. Using genome-wide selective sweep analysis, we identified putative positively selected genes (PSGs) in groups of tits that displayed high and low cooperative breeding rates. The total number of PSGs varied from 146 to 722 in high cooperative breeding rate populations, and from 272 to 752 in low cooperative breeding rate populations. Functional enrichment analysis of these PSGs identified several significantly enriched ontologies related to oxytocin signaling, estrogen signaling, and insulin secretion. PSGs involved in these functional ontologies suggest that molecular adaptations in hormonal regulation may have played important roles in shaping the evolution of cooperative breeding in the ground tit. Taken together, our study provides candidate genes and functional ontologies involved in molecular adaptations associated with cooperative breeding in Tibetan ground tits, and calls for a better understanding of the genetic roles in the evolution of cooperative breeding.

摘要: Roads may influence the selection of phenotypic traits of wildlife. In particular, the likelihood of vehicle collisions with wildlife may vary depending on body coloration in contrast to the road, which may be exaggerated by cultural attitudes toward the species. The timber rattlesnake Crotalus horridus is a threatened species that varies widely in coloration, and their color pattern could influence thermoregulatory use of roads and visibility to motorists. Moreover, better-camouflaged snakes may have higher road mortality in areas where environmental interest is lower and, perhaps, negative attitudes toward wildlife are more prevalent. We used citizen scientist observations of timber rattlesnakes from iNaturalist and categorized for each rattlesnake the surface they were on, its color pattern, and whether they were alive. We combined iNaturalist data with Google Trends data to characterize regional variation in environmental interest. We discovered that lighter-colored snakes were more likely to be found on roads, as were snakes further south, west, and on warmer days. Once on a road, coloration did not influence survival regardless of road type or environmental interest. However, snakes on asphalt roads or on southern roads were more likely to be found dead. The higher likelihood of lighter-colored snakes being found on roads suggests that they are at a greater overall risk of road death, potentially selecting for darker coloration. Citizen scientist behavior may at least partly underlie the influence of latitude on the results, however, and further work in the application of citizen science data to such research questions is warranted.

摘要: Dispersal is an individual life-history trait that can influence the ecological and evolutionary dynamics of both the source and recipient populations. Current studies of animal dispersal have paid little attention to how the responses of residents in a recipient population affect the social resettlement of dispersers into a new habitat. We addressed this question in the blue-breasted quail Synoicus chinensis by designing an outsider introduction experiment to simulate a scenario of interaction between residents and dispersers. In the experiment, we introduced an unfamiliar quail into a group of 3 differently ranked residents and then examined their behavioral responses to the arrival of the outsider. We found that all residents made negative responses by pecking at the outsider to maintain their pecking order, in which high-ranked residents displayed significantly greater intensity than those of lower ranks. This result highlighted that adverse behavioral responses of residents would prevent outsiders from obtaining hierarchical dominance in the recipient group. Moreover, the residents' sex ratio, their relative ages to the outsiders, and whether outsiders counter-pecked at the residents all influenced the probability of outsiders prevailing against the residents. Those outsiders that displayed counter-peck courage were more likely to gain higher dominance and hence resettle into the recipient group successfully. Our findings suggest that resident groups may impose a selection among dispersers via adverse behavioral responses. Therefore, social factors that can influence the resettlement step of dispersers in a new habitat should be accounted for in future studies of animal dispersal.