Phylogeny and evolution of sexually selected tail ornamentation in widowbirds and bishops (Euplectes spp.)

Despite similar ecology, mating systems and female preferences for supernormal tails, the 17 species of African widowbirds and bishops (Euplectes spp.) show astonishing variation in male tail ornamentation. Whereas bishops retain their brown nonbreeding tails in nuptial plumage, widowbirds grow black nuptial tails, varying in length from a few centimetres in E. axillaris to the extreme half metre train of E. progne. Here, we phylogenetically reconstruct the evolution of the discrete trait, nuptial tail and the continuous trait, tail length, using a molecular phylogeny of 33 Euplectes subspecies. Unlike many recent findings of labile evolution of plumage ornaments, our results suggest that the nuptial tail of Euplectes is a derived and phylogenetically conserved ornamental trait that, once gained, shows directional evolution in its expression. Directionality is demonstrated in the trivial sense of a short‐tailed ancestor, and by contingency and randomization tests suggesting that branches with increasing tail length are overrepresented. This supports an early origin and strong retention of directional female mate choice in widowbirds and bishops, as previously indicated by empirical and experimental results, and provides a less labile, yet rapid scenario of sexually selected diversification.     

Sexual receptivity and post-emergence ovarian development in females of Coproica vagans (Diptera: Sphaeroceridae)

Abstract .Males and females of the dung fly species Coproica vagans Haliday 1833 (Diptera: Sphaeroceridae) mate soon after emergence from the puparium. At this time females still have immature ovaries. Therefore, mating precedes vitellogenesis in this species. Data presented here show that mating enhances oogenesis in C. vagans females. Mated females mature their first egg batch sooner and oviposit four days earlier than virgin conspecifics. Mating-related enhancement of oogenesis could be explained either through nutritional benefits to females or male chemical or stimulatory manipulation of the females. Oogenesis was divided into six arbitrary stages, with vitellogenesis beginning in stage 4. Ovarian development beyond stage 4 is rapid compared with pre-vitellogenetic development. Virgin females pause oogenesis in stage 4. The genital opening of mated females is blocked by a mating plug that persists until oviposition begins. The plug seems to ensure the paternity of the last male to mate by preventing females from remating. The operational sex ratio in C. vagans populations is presumed to be strongly male-biased.     

The importance of scale in comparative microbiome research: New insights from the gut and glands of captive and wild lemurs

Research on animal microbiomes is increasingly aimed at determining the evolutionary and ecological factors that govern host–microbiome dynamics, which are invariably intertwined and potentially synergistic. We present three empirical studies related to this topic, each of which relies on the diversity of Malagasy lemurs (representing a total of 19 species) and the comparative approach applied across scales of analysis. In Study 1, we compare gut microbial membership across 14 species in the wild to test the relative importance of host phylogeny and feeding strategy in mediating microbiome structure. Whereas host phylogeny strongly predicted community composition, the same feeding strategies shared by distant relatives did not produce convergent microbial consortia, but rather shaped microbiomes in host lineage‐specific ways, particularly in folivores. In Study 2, we compare 14 species of wild and captive folivores, frugivores, and omnivores, to highlight the importance of captive populations for advancing gut microbiome research. We show that the perturbational effect of captivity is mediated by host feeding strategy and can be mitigated, in part, by modified animal management. In Study 3, we examine various scent‐gland microbiomes across three species in the wild or captivity and show them to vary by host species, sex, body site, and a proxy of social status. These rare data provide support for the bacterial fermentation hypothesis in olfactory signal production and implicate steroid hormones as mediators of microbial community structure. We conclude by discussing the role of scale in comparative microbial studies, the links between feeding strategy and host–microbiome coadaptation, the underappreciated benefits of captive populations for advancing conservation research, and the need to consider the entirety of an animal's microbiota. Ultimately, these studies will help move the field from exploratory to hypothesis‐driven research.     

Effects of d-amphetamine on behavior maintained by signaled and unsignaled delays to reinforcement

Four pigeons responded under a progressive-delay procedure. In a signaled-delay condition, a chained variable interval (VI) 30-s progressive time (PT) 4-s schedule was arranged; in an unsignaled-delay condition, a tandem VI 30-s PT 4-s schedule was arranged. Two pigeons experienced a signaled-unsignaled-signaled sequence; whereas, two pigeons experienced an unsignaled-signaled-unsignaled sequence. Effects of saline and d-amphetamine were determined under each condition. At intermediate doses (1.0 and 1.78 m/kg) delay functions were shallower, area under the curve was increased, and, when possible, break points were increased compared to saline; these effects were not systematically related to signaling conditions. These effects on control by delay often were accompanied by decreased response rates at 0 s. These results suggest that stimulus conditions associated with the delay may not play a crucial role in effects of d-amphetamine and other stimulants on behavior controlled by reinforcement delay.     

Female-specific color is a signal of quality in the striped plateau lizard (Sceloporus virgatus)

Recent theoretical and empirical studies confirm that male matechoice and/or female–female mate competition can be expressedin the absence of sex-role reversal. Such reproductive patternsmay select for the evolution of female traits that indicatefemale phenotypic or genotypic quality among non–role-reversedspecies. Although attention to the evolution and function offemale ornaments is increasing, additional focus is needed onfemale-specific ornaments (those not expressed in conspecificmales) and on nonavian systems in order to gain a broad understandingof how selection acts directly on ornamentation of female animals.In the striped plateau lizard, Sceloporus virgatus, only femalesdevelop orange throat patches during the reproductive season.The color peaks in expression near the time of ovulation andappears to stimulate male courtship. Here, I examine whetherthis female-specific ornament can be used by males to reliablyassess female phenotypic quality. Using multivariate regressionanalyses, I show that the area of the orange color patch predictsbody condition and mite load, the chroma (i.e., saturation)of the color patch predicts body size, and both patch area andchroma reliably predict average egg mass. Thus, female reproductivecolor may function as a condition-dependent signal, indicatingphenotypic quality to potential mates.     

Simple mathematical models to describe the rate of mating in insect populations

Simple models are constructed to describe the rate of mating in insect populations. The models are based on the assumption of random mate-searching in a closed habitat, including four parameters, i.e., population size, sex ratio, searching efficiency and male's capacity on mating frequency. The modes of effects of these parameters on the rate of mating are analyzed and some principles deduced are discussed in relation to the mating process in natural populations.     

Human biology in Tlaxcala, Mexico: demography

A demographic survey was conducted as part of an ongoing population study of large Mestizo and Indian communities in Tlaxcala, Mexico. Comparative data on population structure and movement, mate selection, age at marriage, differential fertility, and mortality were collected through the administration of a standardized demographic proforma, and then cross-tabulated by computer analysis. The resulting differences between the Indian and Mestizo populations are interpreted in terms of the relative importance of hybridization, natural selection, and genetic drift. Sizeable variance in achieved reproduction and the high neonatal mortality suggest the operation of natural selection in these two populations. Observed patterns of population movement and mate selection indicate that the Mestizo population of the city of Tlaxcala is highly hybridized, in contrast to the endogamous Indian community of San Pablo del Monte.     

Fractional paternity assignment: theoretical development and comparison to other methods

Summary There has recently been a burgeoning interest in the analysis of paternity patterns for natural populations because of its relevance to population genetic phenomena such as the distance between successful mates, relative male reproductive success and gene flow. In this paper we develop a method of analyzing populational patterns of paternity, the fractional paternity method, and compare its performance to two other commonly used methods of paternity analysis (simple exclusion and the most-likely methods). We show that the fractional method is the most accurate method for determining populational patterns of paternity because it assigns paternity to all progeny examined, and because it avoids biases inherent in the other paternity analysis methods when model assumptions are met. In particular, it avoids a systematic bias of the most-likely paternity assignment method, which has a tendency to over-assign paternity of progeny to certain male parents with a greater than average number of homozygous marker loci. We also demonstrate the effect of linkage of some of the marker loci on paternity assignment, showing how the knowledge of the linkage phase of male and female parents in the population can significantly improve the accuracy of the estimates of populational patterns of paternity. Knowledge of the linkage phase of individuals in a population is usually unknown and difficult to assess without progeny testing, which involves considerable labor. However, we show how the linkage phase of hermaphroditic individuals in a population can be obtained in conjunction with the paternity analysis if progeny can be obtained from each hermaphroditic individual in the population, thereby avoiding the problem of traditional progeny testing. Applications of the fractional paternity approach developed herein should contribute significantly to our understanding of the mating patterns in, and hence the evolution of, natural populations.