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Experimental evolution provides an integrative method for revealing complex interactions among evolutionary processes. One such interaction involves sex-linked selfish genetic elements and sexual selection. X-linked segregation distorters, a type of selfish genetic element, influence sperm transmission to increase in frequency and consequently alter the population sex ratio and the opportunity for sexual selection, while sexual selection may impact the spread of X-linked distorters. Here we manipulated sexual selection by controlling female mating opportunities and the presence of a distorting X chromosome in experimental lines of the stalk-eyed fly, Teleopsis dalmanni, over 11 generations. We find that removal of sexual selection leads to an increase in the frequency of the X-linked distorter and sex ratio across generations and that post-copulatory sexual selection alone is sufficient to limit the frequency of distorters. In addition, we find that male eyestalk length, a trait under pre-copulatory sexual selection, evolves in response to changes in the strength of sexual selection with the magnitude of the response dependent on X chromosome type and the frequency of distorting X chromosomes. These results reveal how a selfish X can interact with sexual selection to influence the evolution of sexually selected traits in multiple ways. [ABSTRACT FROM AUTHOR]

Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity. We demonstrate that DNAm accurately predicts chronological age. Across species, longevity is negatively associated with the rate of DNAm change at age-associated sites. Furthermore, analysis of several bat genomes reveals that hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that age-related methylation change is influenced by developmental processes, while longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that bat longevity results from augmented immune response and cancer suppression. DNA methylation profiles from 26 bat species accurately predicts chronological age, while longevity-related methylation patterns across the genome suggest that bat longevity results from augmented immune response and cancer suppression. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.09.003 Byline: Kirsten M. Bohn, Gerald S. Wilkinson, Cynthia F. Moss Abstract: In colonial species, recognition of offspring should be under strong selection. For accurate identification to occur, offspring must produce individually distinctive signals and parents must be able to discriminate between signals. Female greater spear-nosed bats roost in stable social groups and use infant vocalizations, termed isolation calls, to locate and identify their young. In this study, we investigated both the production and perception of isolation calls in P. hastatus. First, we measured acoustic features of calls and found that, after controlling for ontogenetic effects, sufficient variation exists between pups for isolation calls to function as individual signatures. Moreover, calls of pups from the same social group were more similar in spectral and spectrotemporal features than were calls of pups from different social groups, indicating that these features are probably heritable. We used psychoacoustic experiments in the laboratory to determine whether adult females could discriminate between calls from pups in the same or different social group. Females discriminated between pups when faced with a template-matching task and their performance was correlated with the salience of spectral and spectrotemporal features. We found no difference in performance when females had to discriminate between pups from the same and different social groups. These results indicate that females should be able to accurately identify their young using isolation calls. Author Affiliation: (a) Department of Biology, University of Maryland, U.S.A. (a ) Department of Psychology, University of Maryland, U.S.A. Article History: Received 22 March 2006; Revised 18 May 2006; Accepted 5 September 2006 Article Note: (miscellaneous) MS. number: A10399

Evolutionary hypotheses regarding longevity predict that life span should increase as extrinsic mortality rates decrease. Specifically, a decline in age-specific survival and fertility should evolve and decrease life span in proportion to the magnitude of the mortality risk. We examined these ideas using a new data set on maximum longevity, ecology, and life history of 162 parrot species (Psittaciformes). Parrots are generally long-lived but exhibit remarkable variation in life span between similar-sized genera, with particularly long-lived species occurring in the Cacatua, Calyptorhynchus, and Amazona. After controlling for both body size and phylogenetic ancestry using a phylogenetic supertree of all 352 parrot species, type of diet and communal roosting explain significant variation in parrot life span, but the influence of communal roosting is statistically dependent on an association with diet type. We suggest that extreme longevity in parrots has evolved in response to species-specific characteristics of diet, habitat, and behavior that influence extrinsic mortality rates. Received 24 July 2004, accepted 8 June 2005. Key words: life history, longevity, parrots, Psittaciformes. Las hipotesis evolutivas relacionadas con la longevidad predicen que la duracion de la vida debe incrementarse cuando las tasas de mortalidad extrinseca disminuyen. Especificamente, se esperarla una disminucion evolutiva en la supervivencia y la fertilidad a edades especificas, causando una disminucion en la longevidad proporcional a la magnitud del riesgo de mortalidad. Examinamos estas ideas empleando una base de datos nueva sobre la longevidad maxima, la ecologia y las historias de vida de 162 especies de Psittaciformes. Los Psittaciformes son generalmente longevos pero existe amplia variacion en la longevidad entre generos con especies de tamano corporal similar; las especies particularmente longevas pertenecen a los generos Cacatua, Calyptorhynchus y Amazona. Luego de controlar por el tamano corporal y la ancestria filogenetica empleando un superarbol filogenetico de las 352 especies de Psittaciformes, el tipo de dieta y el uso de perchas comunales explicaron significativamente la variacion en la longevidad, pero la influencia del uso de perchas comunales depende estadisticamente de una asociacion con el tipo de dieta. Sugerimos que la extrema longevidad de los Psittaciformes ha evolucionado como respuesta a caracteristicas de la dieta, el habitat y el comportamiento especificas de las especies que influencian las tasas extrinsecas de mortalidad.

An overview is presented on the occurrence of heteromorphic sperm in insects. Topics include hypotheses for sperm function, distribution and development, evolution, and observations of heteromorphic sperm development in Lepidoptera, Diptera (Diopsidae and Drosophilidae), Hemiptera, Hymenoptera, and Coleoptera.

Sperm development, sex chromosome meiotic drive, and age have been studied in Cyrtodiopsis whitei, an unusual stalk-eyed fly. It may be that frequency-dependent selection on male fertility stabilizes the drive polymorphism in the flies.

Wolbachia are cytoplasmically inherited bacteria. They can alter the reproductive biology of hosts in a way that increases their presence in a population. The distribution and reproductive effects of these bacteria have been studied in stalk-eyed flies (Diptera: Diopsidae) and it seems the microbes are associated with greater fly male fertility. Wolbachia do not cause detectable cytoplasmic incompatibility or cut down reproduction in the host.

Female greater spear-nosed bats, Phyllostomus hastatus, can discriminate the calls of members of their own social groups but fail to discriminate individual calls based on field and laboratory playback studies using bat populations from three caves. The familiarity and discrimination of groupmates provide benefits to these bats in terms of sharing food resources and guarding feeding areas.

The social calls emitted by the greater spear-nosed bats, Phyllostomus hastatus are contact calls that coordinate foraging activities in this species. This is the conclusion drawn from seasonal observations and playback investigations undertaken in colonies in Trinidad, West Indies. The evidences that proved these screeches to be social calls in the greater spear-nosed bats are presented.

Sexual selection in through female preference for male genetic quality is a controversial subject, as genetic mechanisms have insufficient variation in male quality to account for preference and ornament evolution. Research now shows that females have a preference for ornaments indicating genetic quality generated by conflict by sex chromosomes. Sex-ratio distributions were compared in stalk-eyed fly progeny, and female-biased sex ratios occurred in species show eye-stalk sexual dimorphism, and a female preference for long eye span.

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome ([X.sup.d]). Relatively high frequencies of [X.sup.d] in C. dalmanni and C. whitei (13-17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of [X.sup.d]. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with [X.sup.d], modifying Y chromosomes ([Y.sup.m]) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of [X.sup.d] on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.