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Stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio (SR) meiotic drive and impact the fitness of male and female carriers. Here, we assemble and describe a chromosome-level genome assembly of the stalk-eyed fly, Teleopsis dalmanni , to elucidate patterns of divergence associated with SR. The genome contains tens of thousands of transposable element (TE) insertions and hundreds of transcriptionally and insertionally active TE families. By resequencing pools of SR and ST males using short and long reads, we find widespread differentiation and divergence between XSR and XST associated with multiple nested inversions involving most of the SR haplotype. Examination of genomic coverage and gene expression data revealed seven X-linked genes with elevated expression and coverage in SR males. The most extreme and likely drive candidate involves an XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and associated with regulation of TE expression. In addition, we find evidence for rapid protein evolution between XSR and XST for testis expressed and novel genes, that is, either recent duplicates or lacking a Dipteran ortholog, including an X-linked duplicate of maelstrom , which is also involved in TE silencing. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species. [ABSTRACT FROM AUTHOR]

Artificial selection offers a powerful tool for the exploration of how selection and development shape the evolution of morphological scaling relationships. An emerging approach models the expression and evolution of morphological scaling relationships as a function of variation among individuals in the developmental mechanisms that regulate trait growth. These models posit the existence of genotype-specific morphological scaling relationships that are unseen or "cryptic." Within-population allelic variation at growth-regulating loci determines how these individual cryptic scaling relationships are distributed, and exposure to environmental factors that affect growth determines the size phenotype expressed by each individual on their cryptic, genotype-specific scaling relationship. These models reveal that evolution of the intercept and slope of the population -level static allometry is determined, often in counterintuitive ways, largely by the shape of the distribution of these underlying individual -level scaling relationships. Here we review this modeling framework and present the wing-body size individual cryptic scaling relationships from a population of Drosophila melanogaster. To determine how these models might inform interpretation of published work on scaling relationship evolution, we review studies where artificial selection was applied to alter the parameters of population-level static allometries. Finally, motivated by our review, we outline areas in need of empirical work and describe a research program to address these topics; the approach includes describing the distribution of individual cryptic scaling relationships across populations and environments, empirical testing of the model's predictions, and determining the effects of environmental heterogeneity on realized trait distributions and how this affects allometry evolution. [ABSTRACT FROM AUTHOR]

Cooperative behaviors exist along a spectrum of cost, from no-risk scenarios of mutual benefit to self-sacrificing altruism. Hamilton's rule predicts that as risk increases, cooperative decisions should become increasingly kin-biased (nepotistic). To manipulate the perceived risks of regurgitated food sharing in captive vampire bats, we created a novel "rescue" condition, which required that donors leave their preferred roosting location, descend to an illuminated spot on the cage floor, and regurgitate food across cage bars to a trapped hungry bat. Vampire bats adapted their food sharing to this novel context, but with a dramatic reduction in the probability and amount of food sharing. Sixteen of 29 bats were fed by groupmates when trapped. All 15 starved bats that were tested in both trapped and free conditions received less food when trapped. Donations to trapped bats came from kin and nonkin, but subjects received a greater proportion of their food from closer relatives when trapped than when free. This finding supports the prediction that nepotistic biases should be exaggerated under dangerous conditions. [ABSTRACT FROM AUTHOR]

Throughout their evolutionary history, genomes acquire new genetic material that facilitates phenotypic innovation and diversification. Developmental processes associated with reproduction are particularly likely to involve novel genes. Abundant gene creation impacts the evolution of chromosomal gene content and general regulatory mechanisms such as dosage compensation. Numerous studies in model organisms have found complex and, at times contradictory, relationships among these genomic attributes highlighting the need to examine these patterns in other systems characterized by abundant sexual selection. Therefore, we examined the association among novel gene creation, tissue-specific gene expression, and chromosomal gene content within stalk-eyed flies. Flies in this family are characterized by strong sexual selection and the presence of a newly evolved X chromosome. We generated RNA-seq transcriptome data from the testes for three species within the family and from seven additional tissues in the highly dimorphic species, Teleopsis dalmanni. Analysis of dipteran gene orthology reveals dramatic testes-specific gene creation in stalk-eyed flies, involving numerous gene families that are highly conserved in other insect groups. Identification of X-linked genes for the three species indicates that the X chromosome arose prior to the diversification of the family. The most striking feature of this X chromosome is that it is highly masculinized, containing nearly twice as many testes-specific genes as expected based on its size. All the major processes that may drive differential sex chromosome gene content---creation of genes with male-specific expression, development of male-specific expression from pre-existing genes, and movement of genes with male-specific expression---are elevated on the X chromosome of T. dalmanni. This masculinization occurs despite evidence that testes expressed genes do not achieve the same levels of gene expression on the X chromosome as they do on the autosomes. [ABSTRACT FROM AUTHOR]

In long-lived temperate bats, female philopatry can influence the genetic structure of roosting groups and the potential for individuals to interact across generations. Although direct observation of dispersal between social groups is difficult given the vagility and nocturnal activity of most bats, molecular markers can be used to infer dispersal and mating patterns. Here we report on female philopatry among pallid bats, Antrozous pallidus, a species that exhibits dynamic fission-fusion roosting behavior in which philopatry and familiarity with a roosting area may help individuals choose roost sites and gain benefits associated with social roosting. In addition, we use genetic data to draw inferences about how dispersal and mating relate to the presence of divergent mitochondrial clades, which have been previously reported for pallid bats in western North America. We found significant genetic structure among colonies in central Oregon based on sequence variation at the mitochondrial (mt) DNA control region (pairwise ФФST = 0.08-0.678), but very little structure among colonies for bi-parentally inherited nuclear microsatellites (pairwise FST = 0.004-0.01) indicative of female philopatry and male-mediated gene flow. Interestingly, some bats captured in the same colony had mtDNA haplotypes that differed by more than 12% yet failed to exhibit differences at nuclear markers. Thus, even though such divergence values are sometimes associated with species differences, evidence indicates that bats from these clades freely interbreed. This unusual pattern seems likely to be the result of postglacial range expansions from separate southern refugia northwards followed by recent secondary contact. [ABSTRACT FROM AUTHOR]

We use three allopatric populations of the stalk-eyed fly Teleopsis dalmanni from Southeast Asia to test two predictions made by the sex chromosome drive hypothesis for Haldane's rule. The first is that modifiers that suppress or enhance drive should evolve rapidly and independently in isolated populations. The second is that drive loci or modifiers should also cause sterility in hybrid males. We tested these predictions by assaying the fertility of 2066 males derived from backcross experiments involving two pairs of populations and found that the proportion of mated males that fail to produce any offspring ranged from 38 to 60% among crosses with some males producing strongly female-biased or male-biased sex ratios. After genotyping each male at 25-28 genetic markers we found quantitative trait loci (QTL) that jointly influence male sterility, sperm length, and biased progeny sex ratios in each pair of populations, but almost no shared QTL between population crosses. We also discovered that the extant XSR chromosome has no effect on sex ratio or sterility in these backcross males. Whether shared QTL are caused by linkage or pleiotropy requires additional study. Nevertheless, these results indicate the presence of a "cryptic" drive system that is currently masked by suppressing elements that are associated with sterility and sperm length within but not between populations and, therefore, must have evolved since the populations became isolated, i.e., in <100,000 years. We discuss how genes that influence sperm length may contribute to hybrid sterility. [ABSTRACT FROM AUTHOR]

The steps by which isolated populations acquire reproductive incompatibilities remain poorly understood. One potentially important process is postcopulatory sexual selection because it can generate divergence between populations in traits that influence fertilization success after copulation. Here we present a comprehensive analysis of this form of reproductive isolation by conducting reciprocal crosses between variably diverged populations of stalk-eyed flies ( Teleopsis dalmanni). First, we measure seven types of reproductive incompatibility between copulation and fertilization. We then compare fertilization success to hatching success to quantify hybrid inviability. Finally, we determine if sperm competition acts to reinforce or counteract any incompatibilities. We find evidence for multiple incompatibilities in most crosses, including failure to store sperm after mating, failure of sperm to reach the site of fertilization, failure of sperm to fertilize eggs, and failure of embryos to develop. Local sperm have precedence over foreign sperm, but this effect is due mainly to differences in sperm transfer and reduced hatching success. Crosses between recently diverged populations are asymmetrical with regard to the degree and type of incompatibility. Because sexual conflict in these flies is low, postcopulatory sexual selection, rather than antagonistic coevolution, likely causes incompatibilities due to mismatches between male and female reproductive traits. [ABSTRACT FROM AUTHOR]

Although male ornaments may provide benefits to individuals bearing them, such structures may also entail fitness costs. Selection should favour aspects of the phenotype that act to reduce such costs, yet such compensatory traits are often ignored in studies of sexual selection. If a male ornament increases predation risk via reduced locomotor performance, then there may be selection for changes in morphological traits to compensate for behavioural or biomechanical changes in how individuals use their morphology (or both). We took a comparative approach aiming to test whether changes in wing beat frequency are evolutionarily correlated with increases in male ornamentation across stalk-eyed fly species. Previous studies have shown that increased male eye span is evolutionarily correlated with increased wing size; thus, we tested whether there is additional compensation via increases in size-adjusted wing beat frequency. The results obtained revealed that relative wing beat frequency is negatively related to relative eye span in males, and sexual dimorphism in wing beat frequency is negatively related to dimorphism in eye span. These findings, in addition to our finding that eye span dimorphism is positively related to aspect ratio dimorphism, suggest that male stalk-eyed flies compensate primarily by increasing wing size and shape, which may then have resulted in the subsequent evolutionary reduction in wing beat frequency. Thus, exaggerated ornaments can result in evolutionary modifications in wing morphology, which in turn lead to adjustments in flapping kinematics, illustrating the tight envelope of trade-offs when compensating for exaggerated ornaments. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 670-679. [ABSTRACT FROM AUTHOR]

The eyes of stalk-eyed flies (Diopsidae) are positioned at the end of rigid peduncles (‘stalks’) protruding laterally from the head. Eye-stalk length varies within the family and, in some species, varies between males and females. Larger eye-stalks in males result from sexual selection for longer stalks, a trait that increases male reproductive success. In the present study, we examined whether an increase in eye-stalk length results in an adjustment of wing size and shape to deal with the burden of bearing an exaggerated ‘ornament’. We compared wing morphology among ten species of stalk-eyed flies that differ in eye-span and the degree of sexual dimorphism. Mass-specific wing length differed between males and females in seven out of the ten species. Nondimensional wing shape parameters differed between the species ( P < 0.001), but mostly did not differ between males and females of the same species. Dimorphism in eye-span closely correlated with dimorphism in wing length ( r = 0.89, P < 0.001) and the correlation remained significant (r = 0.81, P = 0.006) after correcting for phylogenetic relationships. Once corrected for phylogenetic relatedness, the mass-specific wing length of males (but not females) was weakly correlated with mass-specific eye-span ( r = 0.66, P = 0.042). We propose that the observed proportional increase in wing length associated with increased eye-span can facilitate aerial manoeuverability, which would otherwise be handicapped by the elevated moment of inertia imposed by the wider head. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 860–871. [ABSTRACT FROM AUTHOR]

Coevolution between male and female traits can result from correlated responses to selection or correlated selection on genetically independent traits. This study examines the possibility that traits involved in precopulatory sexual selection may influence the evolution of traits involved in postcopulatory sexual selection due to the existence of correlated selection or correlated responses to selection. Artificial selection on male eye span in Cyrtodiopsis dalmanni, a sexually dimorphic stalk-eyed fly, is used to test for correlated changes in reproductive traits of male and female flies. Flies from replicate lines that had been under selection for 57 generations were matched for age and genotyped at four X-linked microsatellite loci. Egg number and testis size increased with age, but did not differ among lines. Spermathecal areas and duct lengths differed among replicates, but not among selection treatments. Female relative eye span, size of the ventral receptacle and egg size exhibited significant correlated responses to selection on male relative eye span. The absence of any change in sperm length or testis size between lines indicates that changes in female traits are unlikely due to correlated selection mediated by sperm competition. Significant effects of X-linked microsatellite genotypes indicate instead that the correlated responses to selection were due, in part, to X-linked genes in linkage disequilibrium or that exhibit pleiotropy. The presence of nonadditive allelic effects on genetically correlated female traits combined with additive allelic effects on a male ornament provides a previously unrecognized mechanism by which genetic variation could be maintained despite strong sexual selection. [ABSTRACT FROM AUTHOR]

We test the relative rates of evolution of pre- and postzygotic reproductive isolation using eight populations of the sexually dimorphic stalk-eyed flies Cyrtodiopsis dalmanni and C. whitei. Flies from these populations exhibit few morphological differences yet experience strong sexual selection on male eyestalks. To measure reproductive isolation we housed one male and three female flies from within and between these populations in replicate cages and then recorded mating behavior, sperm transfer, progeny production, and hybrid fertility. Using a phylogeny based on partial sequences of two mitochondrial genes, we found that premating isolation, postmating isolation prior to hybrid eclosion, and female hybrid sterility evolve gradually with respect to mitochondrial DNA sequence divergence. In contrast, male hybrid sterility evolves much more rapidly--at least twice as fast as any other form of reproductive isolation. Hybrid sterility, therefore, obeys Haldane's rule. Although some brood sex ratios were female biased, average brood sex ratio did not covary with genetic distance, as would be expected if hybrid inviability obeyed Haldane's rule. The likelihood that forces including sexual selection and intra- and intergenomic conflict may have contributed to these patterns is discussed. [ABSTRACT FROM AUTHOR]

Sperm competition is common in many insect species; however, the mechanisms underlying differences in sperm precedence are not well understood. In the stalk-eyed fly, Cyrtodiopsis whitei (Diptera, Diopsidae), sperm precedence is influenced by the presence of sex chromosome meiotic drive. When drive-carrying males compete with non-driving males for fertilizations within a female, the number of progeny sired by drive males is significantly fewer than predicted by sperm mixing alone. Thus, drive males apparently suffer not only a reduction in the number of viable sperm produced, but also a reduction in sperm competitive ability. In this study, we manipulated the amount and source of seminal fluid and sperm received by females by interrupting copulations before sperm, but after seminal fluid, was transferred. We find that seminal fluid from another male influences the number of progeny sired by a drive-carrying male when both males mate with the same female. Sperm viability staining reveals that sperm from drive males are incapacitated by seminal fluid from other males within the female reproductive tract. These results suggest that multiple mating by females enables seminal fluid products to interact differentially with sperm and may reduce the transmission advantage of the drive chromosome. [ABSTRACT FROM AUTHOR]

Provides information on a study that investigated the phylogenetic analysis of correlation structure in stalk-eyed flies in the genus Diasemopsis. Methodology of the study; Results and discussion on the study.

Presents a study that determined the geographic and individual variation in vocalizations of male Saccopteryx bilineata also known as bats. Details on the daytime repertoire of male bats; Discussion on the potential importance of individual and colony-level differences in the vocal displays of the bats; Methodology and result of the study.

Presents a study which examined the pattern of evolutionary change in the sexual dimorphism and static allometry of eye stalks in stalk-eyed flies in the family Diopsidae. Pattern of gains and losses of sexual dimorphism and eye-span allometry; Coevolution of males and females; Discussion on evolutionary flexibility of static allometry; Materials and methodology; Results and discussion.

Investigates the influence of sex chromosome on male relative eyespan, a sexually selected trait in the stalk-eyed fly Cyrtodiopsis dalmanni. Magnitude of an X-chromosome effect; Reciprocal cross; Lack of a disproportionate effect of dosage-compensated X-linked loci on relative eyespan.

Sensory exploitation predicts that female mate preferences exist before the evolution of exaggerated male ornaments. We tested this prediction by estimating female preference functions, remating intervals, and copulation durations for three species of stalk-eyed flies. Two species, Cyrtodiopsis whitei and C dalmanni, exhibit extreme sexual dimorphism in eye span, with eye stalks exceeding body length in large males. In contrast, C quinqucguttata of both sexes possess short eye stalks. Maximum parsimony analysis of 437 basepairs of the 16S mitochondrial ribosomal RNA gene from 6 Malaysian diopsids reveals that short, sexually monomorphic eye stalks are plesiomorphic in Cyrtodiopsis. Observations of multiple copulations by females in paired-choice mating chambers indicated that female C whitei and C. dalmanni exhibit relative preferences for longer eye stalks such that preference intensity increases linearly with the difference in eye stalk length between males. Females from the sexually monomorphic species showed no detectable preference for male eye stalk length. Female mating preferences of bodi sexually dimorphic species exhibited significant repeatability, as expected if genetic variation underlies the preference. In addition, female C whitei and C. dalmanni exhibited shorter copulations, mated more frequently, and rejected fewer mating attempts than female C quinqueguttata. Thus, opportunities for sperm competition have increased with acquisition of female preferences. We conclude that female sensory bias for males with long eye span did not exist in a common ancestor to these species. Instead, female preference and remating propensity either coevolved with eye span dimorphism or evolved after male eye stalks elongated. [ABSTRACT FROM AUTHOR]

Focuses on the evolution of repeated sequence arrays in the D-loop region of bat mitochondrial deoxyribonucleic acid (DNA). Information on animal mitochondria; Details on the function of the D-loop.