Sepsis Cynipsea Research Articles

Geographic Variation in Genomic Signals of Admixture Between Two Closely Related European Sepsid Fly Species

The extent of interspecific gene flow and its consequences for the initiation, maintenance, and breakdown of species barriers in natural systems remain poorly understood. Interspecific gene flow by hybridization may weaken adaptive divergence, but can be overcome by selection against hybrids, which may ultimately promote reinforcement. An informative step towards understanding the role of gene flow during speciation is to describe patterns of past gene flow among extant species. We investigate signals of admixture between allopatric and sympatric populations of the two closely related European dung fly species Sepsis cynipsea and S. neocynipsea (Diptera: Sepsidae). Based on microsatellite genotypes, we first inferred a baseline demographic history using Approximate Bayesian Computation. We then used genomic data from pooled DNA of natural and laboratory populations to test for past interspecific gene flow based on allelic configurations discordant with the inferred population tree (ABBA–BABA test with D-statistic). Comparing the detected signals of gene flow with the contemporary geographic relationship among interspecific pairs of populations (sympatric vs. allopatric), we made two contrasting observations. At one site in the French Cevennes, we detected an excess of past interspecific gene flow, while at two sites in Switzerland we observed lower signals of past microsatellite genotypes gene flow among populations in sympatry compared to allopatric populations. These results suggest that the species boundaries between these two species depend on the past and/or present eco-geographic context in Europe, which indicates that there is no uniform link between contemporary geographic proximity and past interspecific gene flow in natural populations.

Sexual size dimorphism is associated with reproductive life history trait differentiation in coexisting sepsid flies

Organismal life histories evolve as syndromes, resulting in correlated evolutionary differentiation of key traits that ultimately aid in discerning species. Reproductive success depends both on the absolute body size of an individual and its size relative to the opposite sex: sexual size dimorphism. In an attempt to further elucidate their coexistence and ecological diversification, we compared standard life history (first reproduction, clutch size, egg size) and associated reproductive trait differentiation of 15 widespread European sepsid fly species (Diptera: Sepsidae) under laboratory common garden conditions. Despite relatively uniform body sizes, sexual dimorphism ranged from female‐ to male‐biased, and development time varied twofold across species. We expected, and found, the abundant and relatively large species (Sepsis cynipsea, punctum, thoracica) with often male‐biased SSD to lay larger but fewer eggs and show fast‐developing, fast‐reproducing life histories with aggressive (coercive) mating behavior characterized by short mating latencies and male conflict. In contrast, the smaller and more dispersed species with female‐biased SSD (S. flavimana, orthocnemis, violacea) laid smaller but more eggs, showing a generally slower life history with long and delayed copulation and oviposition, high mating reluctance fostering extensive inter‐sexual conflict, and more elaborate male (pre‐)copulatory courtship. Two Saltella species were exceptional, being large, developing slowly, nevertheless copulating soon after adult emergence, profusely and briefly. The documented life history differentiation seems partly driven by sexual selection leading to male‐biased dimorphism, rather than undetermined ecological selection, but regardless appears insufficient to explain the coexistence and diversification of these sepsid species in European pastoral landscapes.

Exaggerated male forelegs are not more differentiated than wing morphology in two widespread sister species of black scavenger flies

Sexual selection represents a potent force that can drive rapid population differentiation in traits related to reproductive success. Hence, sexual traits are expected to show greater population divergence than non‐sexual traits. We test this prediction by exploring patterns of morphological differentiation of the exaggerated fore femur (a male‐specific sexual trait) and the wing (a non‐sexual trait) among allopatric and sympatric populations of the widespread sister dung fly species Sepsis neocynipsea and Sepsis cynipsea (Diptera: Sepsidae). While both species occur in Eurasia, S. neocynipsea also abounds in North America, albeit previous studies suggest strong differentiation in morphology, behavior, and mating systems. To evaluate the degree of differentiation expected under neutrality between S. cynipsea, European S. neocynipsea, and North American S. neocynipsea, we genotyped 30 populations at nine microsatellite markers, revealing almost equal differentiation between and minor differentiation among geographic populations within the three lineages. Landmark‐based analysis of 18 populations reared at constant 18 and 24°C in a laboratory common garden revealed moderate temperature‐dependent phenotypic plasticity and significant heritable differentiation in size and shape of male forelegs and wings among iso‐female lines of the three lineages. Following the biological species concept, there was weaker differentiation between cross‐continental populations of S. neocynipsea relative to S. cynipsea, and more fore femur differentiation between the two species in sympatry versus allopatry (presumably due to character displacement). Contrary to expectation, wing morphology showed as much shape differentiation between evolutionary independent lineages as fore femora, providing no evidence for faster diversification of traits primarily engaged in mating.

Comparative reproductive dormancy differentiation in European black scavenger flies (Diptera: Sepsidae).

Seasonality is a key environmental factor that regularly promotes life history adaptation. Insects invading cold-temperate climates need to overwinter in a dormant state. We compared the role of temperature and photoperiod in dormancy induction in the laboratory, as well as winter survival and reproduction in the field and the laboratory, of 5 widespread European dung fly species (Diptera: Sepsidae) to investigate their extent of ecological differentiation and thermal adaptation. Unexpectedly, cold temperature is the primary environmental factor inducing winter dormancy, with short photoperiod playing an additional role mainly in species common at high altitudes and latitudes (Sepsis cynipsea, neocynipsea, fulgens), but not in those species also thriving in southern Europe (thoracica, punctum). All species hibernate as adults rather than juveniles. S. thoracica had very low adult winter survivorship under both (benign) laboratory and (harsh) field conditions, suggesting flexible quiescence rather than genetically fixed winter diapause, restricting their distribution towards the pole. All other species appear well suited for surviving cold, Nordic winters. Females born early in the season reproduce before winter while late-born females reproduce after winter, fulgens transitioning earliest before winter and thoracica and punctum latest; a bet-hedging strategy of reproduction during both seasons occurs rarely but is possible physiologically. Fertility patterns indicate that females can store sperm over winter. Winter dormancy induction mechanisms of European sepsids are congruent with their geographic distribution, co-defining their thermal niches. Flexible adult winter quiescence appears the easiest route for insects spreading towards the poles to evolve the necessary overwinter survival.

Geographic patterns of postzygotic isolation between two closely related widespread dung fly species (Sepsis cynipseaandSepsis neocynipsea; Diptera: Sepsidae)

Identifying the contribution of pre‐ and postzygotic barriers to gene flow is a key goal of speciation research. The widespread dung fly species Sepsis cynipsea and Sepsis neocynipsea offer great potential for studying the speciation process over a range of opportunities for gene exchange within and across sister species (cross‐continental allopatry, continental parapatry and sympatry). We examined the role of postcopulatory isolating barriers by comparing female fecundity and egg‐to‐adult viability of F1 and F2 hybrids, as well as backcrosses of F1 hybrids with the parental species, via replicated crosses of sym‐, para‐ and allopatric populations. Egg‐to‐adult viability was strongly but not totally suppressed in hybrids, and offspring production approached nil in the F2 generation (hybrid breakdown), indicating yet unspecified intrinsic incompatibilities. Viable F1 hybrid offspring showed almost absolute male (the heterogametic sex) sterility while females remained largely fertile, in accordance with Haldane's rule. Hybridization between the two species in European areas of sympatry (Swiss Alps) indicated only minor reinforcement based on fecundity traits. Crossing geographically isolated European and North American S. neocynipsea showed similar albeit weaker isolating barriers that are most easily explained by random genetic drift. We conclude that in this system with a biogeographic continuum of reproductive barriers, speciation is mediated primarily by genetic drift following dispersal of flies over a wide (allopatric) geographic range, with some role of natural or sexual selection in incidental or direct reinforcement of incompatibility mechanisms in areas of European sympatry. S(ubs)pecies status of continental S. neocynipsea appears warranted.

Behavioural mechanisms of reproductive isolation between two hybridizing dung fly species

Characterization of the phenotypic differentiation and genetic basis of traits that can contribute to reproductive isolation is an important avenue to understand the mechanisms of speciation. We quantified the degree of prezygotic isolation and geographical variation in mating behaviour among four populations of Sepsis neocynipsea that occur in allopatry, parapatry or sympatry with four populations of its sister species Sepsis cynipsea. To obtain insights into the quantitative genetic basis and the role of selection against hybrid phenotypes we also investigated mating behaviour of F1 hybrid offspring and corresponding backcrosses with the parental populations. Our study documents successful hybridization under laboratory conditions, with low copulation frequencies in heterospecific pairings but higher frequencies in pairings of F1 hybrids signifying hybrid vigour. Analyses of F1 offspring and their parental backcrosses provided little evidence for sexual selection against hybrids. Longer copulation latencies in heterospecific pairings indicate species recognition, probably due to surface or volatile chemicals. The frequency of male mating attempts did not differ greatly between species or hybrid pairings, suggesting no male discrimination of mating partners. Female shaking duration, signifying female choice and/or reluctance to mate, differed strongly between the species and appears to contribute to avoiding heterospecific males; this trait is partially maternal inherited. Importantly, females of both species discriminated more strongly against males in areas of sympatry than allopatry indicating reinforcement. Shorter copulations in heterospecific parental pairings and longer copulations in F1 hybrids suggest mechanistic difficulties with sperm transfer. Overall, our study highlights an important role of character displacement affecting mating behaviour of hybridizing sepsid species in geographical areas of coexistence.

Strategic Ejaculation in the Black Scavenger Fly Sepsis cynipsea Revisited: Copula Duration as a Function of Sperm Depletion and Body Size

AbstractThe massive numbers of sperm males transfer during a single mating are physiologically costly and the amount of sperm that can be stored is limited. Therefore, males can perform only a finite number of successive copulations without loss of fertility, and males should allocate sperm prudently. We investigated sperm availability and depletion in male black scavenger flies, Sepsis cynipsea (Diptera: Sepsidae), asking whether males adjust copula duration according to nutrition, their sperm stores, their own and their partner’s body size, as predicted by theory. We created a gradient of sperm limitation by restricting dung (their protein resource as adults) and subjecting males to a varying number of copulations. While male fertility did not depend on access to fresh dung (contrary to females), it did decline after three copulations, and more so when males were small. Larger females tended to lay more unfertilized eggs after copulating with previously mated males. However, copula duration was not influenced by a male’s number of previous copulations, and therefore apparently not by his current sperm stores. Nevertheless, copula duration varied with male size, with small males copulating longer, and with female size, as copulations lasted longer with larger females, suggesting that males are investing more sperm in larger, more fecund females. While male copula adjustments to their own nutrition and body size may be simple (proximate) physiological responses, responses to female size indicate more strategic and sophisticated sperm‐allocation strategies than previously thought.

No size-dependent reproductive costs in male black scavenger flies (Sepsis cynipsea)

Mating is generally assumed to be costly, but mating costs differ between the sexes. Although mating itself is considered cheaper for males, mate search and mate competition are cheaper for females. Nevertheless, studies increasingly reveal considerable mating costs for males, and these costs should depend on the body size of the individual. We investigated size-dependent predation (ecological) and energetic (physiological) mating costs in male black scavenger flies, Sepsis cynipsea (Diptera: Sepsidae), a model organism for studies of reproductive behavior. We addressed costs of mating by assessing predation risk for differently sized flies in male, female, and mixed-sex groups. Males were not more likely to be predated in mating or matesearch situations. Scathophaga stercoraria (Diptera: Scathophagidae) predators preferred smaller females and males as prey. Male movement in these different social situations does not proximately explain this size-selective predation, as small individuals were not more mobile. We addressed energetic costs of mating by measuring residual longevity (or starvation resistance) of starved males exposed to different mating situations. Copulation, courtship, interaction with reluctant females, or brief interactions with other males, all presumably increasing energy demand, did not significantly reduce longevity of males compared with males not interacting with other individuals. In general, small males died sooner when starved. Overall, we found no direct costs of mating for male S. cynipsea, but both predation and physiological costs were size dependent. Key words: body size, energetic costs, food limitation, mating behavior, mortality, predation, starvation resistance. [Behav Ecol]

Longevity and Developmental Stability in the Dung FlySepsis cynipsea,as Affected by the Ectoparasitic Mite,Pediculoides mesembrinae

Fluctuating asymmetry (FA) is a widely employed measure of developmental stability. It has been found to increase with many stressors including parasite infection. Associations between parasites and FA may exist for several reasons in addition to parasites being the direct cause of increased FA. Developmentally stable individuals may have superior immune systems, and be less susceptible to parasite infection, and/or may be less exposed to parasites than developmentally unstable ones. Mites negatively impact host fitness in a number of insects, and if FA is a reflection of general genetic quality, as has been proposed, associations between mite number and FA are predicted. Potential relationships were investigated between an ectoparasitic mite, Pediculoides mesembrinae (Canestrini) (Phthiraptera: Menoponidae) and FA in the common dung fly Sepsis cynipsea (L.) (Diptera: Sepsidae). While it was found that mite infested flies died much faster than flies without mites, indicating that mites indeed stress their hosts, counter to expectations, no associations between mites and FA were found in any analyses. Additionally, FA in mite-infected flies generally did not differ from previously published FA data from uninfected S. cynipsea. Nevertheless, parasitized males tended to be somewhat less asymmetrical than non-parasitized males, but based on our data, it does not appear that mite infestation is generally associated with developmental stability in S. cynipsea.

Development of polymorphic microsatellite markers for the dung fly (Sepsis cynipsea)

The polyandrous fly Sepsis cynipsea has been used extensively in studies of sexual selection and local adaptation. We isolated and characterized 11 novel microsatellite markers for S. cynipsea from a genomic library and screened 32 flies for polymorphism. All microsatellite markers show high allelic diversity with an average of 9.64 alleles per locus. Two microsatellites were found likely to be X-linked. These novel markers will significantly advance studies of sexual selection and evolutionary genetics of S. cynipsea and related species, especially given the low numbers of markers currently available in this family.

Is reduced female survival after mating a by-product of male-male competition in the dung fly Sepsis cynipsea?

BackgroundIn a number of species males damage females during copulation, but the reasons for this remain unclear. It may be that males are trying to manipulate female mating behaviour or their life histories. Alternatively, damage may be a side-effect of male-male competition. In the black scavenger or dung fly Sepsis cynipsea (Diptera: Sepsidae) mating reduces female survival, apparently because males wound females during copulation. However, this damage does not seem to relate to attempted manipulation of female reproduction by males. Here we tested the hypothesis that harming females during mating is an incidental by-product of characters favoured during pre-copulatory male-male competition. We assessed whether males and their sons vary genetically in their ability to obtain matings and harm females, and whether more successful males were also more damaging. We did this by ranking males' mating success in paired competitions across several females whose longevity under starvation was subsequently measured.ResultsAs previously reported, our results show mating is costly for female S. cynipsea. However, variance in female longevity was not explained by male identity, family, body size, number of previous copulations, or copulation duration. Nevertheless, there was a positive correlation between the harm fathers inflicted on their mates (affecting female longevity) and the harm sons inflicted on theirs. Additionally, family identity significantly influenced male copulation success.ConclusionOur results indicate a heritable component of some yet unspecified male trait(s) that influence harm and mating success. However, there was no relationship between copulation success of fathers or sons and the mean longevity of their mates. We therefore found no support for harm being a side effect of traits favoured in pre-copulatory male-male competition.

The reluctant fly: what makes Sepsis cynipsea females willing to copulate?

A female's willingness to copulate (i.e. her receptivity) can depend on several endogenous, environmental and social factors. The black scavenger or dung fly, Sepsis cynipsea (Diptera: Sepsidae), is a classic example of strong female reluctance to mate and sexual conflict over mating. Laboratory studies have found high variability in female receptivity and even virgins unwilling to mate. The aim of this study was to determine the proximate factors influencing female receptivity. Fresh dung was necessary for egg production. Female receptivity strongly depended on a female's egg-laying cycle rather than age: receptivity was highest when females had no ripe eggs. The absence of eggs in the female's reproductive tract is probably required for spermatophore transfer, leading to the unusual precopulatory guarding and postoviposition mating of sepsids. Nonvirgins were less receptive than virgins, except when they were in need of sperm, and more receptive when they were larger and had previously laid more eggs. Only when not in need of sperm did females copulate with males larger than their previous mate. This suggests sequential female choice, but females typically copulated with the first of up to 10 presented males or not at all, provided that they were at the appropriate stage of their laying cycle. Female unwillingness to mate in this and probably other species therefore has various, sometimes physiological (intrinsic) causes. These must be controlled in experiments assessing mate choice, costs and benefits of mating, or sexual conflict. Not taking into account female egg-laying state can mask female choice, bias data and suggest wrong associations.

Sexual morphology of male Sepsis cynipsea (Diptera: Sepsidae): lack of support for lock-and-key and sexually antagonistic morphological coevolution hypotheses

AbstractTraits that function in male–female sexual interactions tend to diverge rapidly compared with other traits. Several hypotheses attempt to explain this evolutionary pattern. Predictions of two of these hypotheses, lock-and-key and sexually antagonistic morphological co-evolution, were tested by examining how two sets of species-specific male structures fit with female structures during courtship and copulation in the fly Sepsis cynipsea (L., 1758). Contrary to predictions of both hypotheses, neither the species-specific modifications of the male's front legs nor those of his genitalic surstyli were matched by modifications of the female structures with which they meshed (wing bases, 6th abdominal sternite); males damaged small patches of microtrichia on the female's wings with their legs, but the morphology of the female's wings and abdomen showed no sign of the defensive designs expected under antagonistic morphological co-evolution. Data regarding the alternative hypothesis of sexually antagonistic behavioral co-evolution by females in response to male morphology were less conclusive, but this hypothesis failed to explain the sustained, apparently stimulatory rhythmic squeezing by the male genitalia and the lack of female defensive responses to this squeezing. These movements of the male surstyli during copulation suggest that they function to stimulate the female. The wing base of the female has apparent sense organs near the sites contacted by the male, as expected under the alternative hypothesis of traditional female choice to explain rapid divergent evolution. The male's genitalic surstyli were also used in novel precopulatory interactions. A pair of previously undescribed processes at the bases of the surstyli probably grasp and may also rhythmically squeeze the female during copulation.

How Important Is Sexual Conflict?

Next article No AccessHow Important Is Sexual Conflict?David Hosken and Rhonda SnookDavid Hosken Search for more articles by this author and Rhonda Snook Search for more articles by this author 1. Centre for Ecology and Conservation, University of Exeter in Cornwall, Tremough, Penryn, Cornwall TR10 9EZ, United Kingdom;2. Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield S10 2TN, United KingdomPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 165, Number S5May 2005HOW IMPORTANT IS SEXUAL CONFLICT?A Special Issue Edited by David Hosken and Rhonda Snook Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/429355 Views: 112Total views on this site Citations: 25Citations are reported from Crossref © 2005 by The University of Chicago.PDF download Crossref reports the following articles citing this article:Marcus Lee, Carlota Solano Udina, Lars-Anders Hansson Fear of sex: sexual conflict exposed as avoidance in a parthenogenetic invertebrate, Behavioral Ecology and Sociobiology 75, no.88 (Jul 2021).https://doi.org/10.1007/s00265-021-03054-9David J. Hosken, C. Ruth Archer, Clarissa M. House, Nina Wedell Penis evolution across species: divergence and diversity, Nature Reviews Urology 16, no.22 (Nov 2018): 98–106.https://doi.org/10.1038/s41585-018-0112-zRebecah E. Ford, Stephen C. Weeks, E. Hebets Intersexual conflict in androdioecious clam shrimp: Do androdioecious hermaphrodites evolve to avoid mating with males?, Ethology 124, no.55 (Apr 2018): 357–364.https://doi.org/10.1111/eth.12738Linda C. Hernández Duran, Gonzalo E. Fajardo Medina, Luz S. Fuentes Quintero Mating Opportunities in Sangalopsis veliterna Females: Costs and Benefits, Journal of Insect Science 14, no.112112 (Aug 2014): 1–9.https://doi.org/10.1673/031.014.112Akanksha Singh, Bashisth N. Singh Role of sexual selection in speciation in Drosophila, Genetica 142, no.11 (Dec 2013): 23–41.https://doi.org/10.1007/s10709-013-9751-4Krista M. Milich, Janice M. Bahr, Rebecca M. Stumpf, Colin A. Chapman Timing is everything: expanding the cost of sexual attraction hypothesis, Animal Behaviour 88 (Feb 2014): 219–224.https://doi.org/10.1016/j.anbehav.2013.11.029Ryne A. Palombit Sexual Conflict in Nonhuman Primates, (Jan 2014): 191–280.https://doi.org/10.1016/B978-0-12-800286-5.00005-5Abderrahman Khila, Ehab Abouheif, Locke Rowe Function, Developmental Genetics, and Fitness Consequences of a Sexually Antagonistic Trait, Science 336, no.60816081 (May 2012): 585–589.https://doi.org/10.1126/science.1217258Adrian L. O'Loghlen, Stephen I. Rothstein, Jane M. Waterman When Less Is Best: Female Brown-Headed Cowbirds Prefer Less Intense Male Displays, PLoS ONE 7, no.55 (May 2012): e36130.https://doi.org/10.1371/journal.pone.0036130Rebecca M. Stumpf, Rodolfo Martinez-Mota, Krista M. Milich, Nicoletta Righini, Milena R. Shattuck Sexual conflict in primates, Evolutionary Anthropology: Issues, News, and Reviews 20, no.22 (Apr 2011): 62–75.https://doi.org/10.1002/evan.20297Adrian L. O’Loghlen, Stephen I. Rothstein Multimodal signalling in a songbird: male audiovisual displays vary significantly by social context in brown-headed cowbirds, Animal Behaviour 79, no.66 (Jun 2010): 1285–1292.https://doi.org/10.1016/j.anbehav.2010.03.001Matthew D. Hall, Simon P. Lailvaux, Mark W. Blows, Robert C. Brooks SEXUAL CONFLICT AND THE MAINTENANCE OF MULTIVARIATE GENETIC VARIATION, Evolution 64, no.66 (Dec 2009): 1697–1703.https://doi.org/10.1111/j.1558-5646.2009.00932.xRyne A. Palombit Conflict and Bonding Between the Sexes, (Sep 2009): 53–83.https://doi.org/10.1007/978-3-642-02725-3_3John Archer Does sexual selection explain human sex differences in aggression?, Behavioral and Brain Sciences 32, no.3-43-4 (Aug 2009): 249.https://doi.org/10.1017/S0140525X09990951KRISTA K. INGRAM, TORSTEN LAAMANEN, NALINI PUNIAMOORTHY, RUDOLF MEIER Lack of morphological coevolution between male forelegs and female wings in Themira (Sepsidae: Diptera: Insecta), Biological Journal of the Linnean Society 93, no.22 (Jan 2008): 227–238.https://doi.org/10.1111/j.1095-8312.2007.00922.xDarryl T. 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Hosken, Paula Stockley Sexual conflict, Current Biology 15, no.1414 (Jul 2005): R535–R536.https://doi.org/10.1016/j.cub.2005.07.014Muhammad Qasim Zaman Review: Beyond Turk and Hindu: Rethinking Religious Identities in Islamicate South Asia, Journal of Islamic Studies 14, no.11 (Jan 2003): 112–116.https://doi.org/10.1093/jis/14.1.112

How Important Is Sexual Conflict?

Next article No AccessHow Important Is Sexual Conflict?David Hosken and Rhonda SnookDavid Hosken Search for more articles by this author and Rhonda Snook Search for more articles by this author 1. Centre for Ecology and Conservation, University of Exeter in Cornwall, Tremough, Penryn, Cornwall TR10 9EZ, United Kingdom;2. Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield S10 2TN, United KingdomPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 165, Number S5May 2005HOW IMPORTANT IS SEXUAL CONFLICT?A Special Issue Edited by David Hosken and Rhonda Snook Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/429355 Views: 127Total views on this site Citations: 25Citations are reported from Crossref © 2005 by The University of Chicago.PDF download Crossref reports the following articles citing this article:Marcus Lee, Carlota Solano Udina, Lars-Anders Hansson Fear of sex: sexual conflict exposed as avoidance in a parthenogenetic invertebrate, Behavioral Ecology and Sociobiology 75, no.88 (Jul 2021).https://doi.org/10.1007/s00265-021-03054-9David J. Hosken, C. Ruth Archer, Clarissa M. House, Nina Wedell Penis evolution across species: divergence and diversity, Nature Reviews Urology 16, no.22 (Nov 2018): 98–106.https://doi.org/10.1038/s41585-018-0112-zRebecah E. Ford, Stephen C. Weeks, E. Hebets Intersexual conflict in androdioecious clam shrimp: Do androdioecious hermaphrodites evolve to avoid mating with males?, Ethology 124, no.55 (Apr 2018): 357–364.https://doi.org/10.1111/eth.12738Linda C. Hernández Duran, Gonzalo E. Fajardo Medina, Luz S. Fuentes Quintero Mating Opportunities in Sangalopsis veliterna Females: Costs and Benefits, Journal of Insect Science 14, no.112112 (Aug 2014): 1–9.https://doi.org/10.1673/031.014.112Akanksha Singh, Bashisth N. Singh Role of sexual selection in speciation in Drosophila, Genetica 142, no.11 (Dec 2013): 23–41.https://doi.org/10.1007/s10709-013-9751-4Krista M. Milich, Janice M. Bahr, Rebecca M. Stumpf, Colin A. Chapman Timing is everything: expanding the cost of sexual attraction hypothesis, Animal Behaviour 88 (Feb 2014): 219–224.https://doi.org/10.1016/j.anbehav.2013.11.029Ryne A. Palombit Sexual Conflict in Nonhuman Primates, (Jan 2014): 191–280.https://doi.org/10.1016/B978-0-12-800286-5.00005-5Abderrahman Khila, Ehab Abouheif, Locke Rowe Function, Developmental Genetics, and Fitness Consequences of a Sexually Antagonistic Trait, Science 336, no.60816081 (May 2012): 585–589.https://doi.org/10.1126/science.1217258Adrian L. O'Loghlen, Stephen I. Rothstein, Jane M. Waterman When Less Is Best: Female Brown-Headed Cowbirds Prefer Less Intense Male Displays, PLoS ONE 7, no.55 (May 2012): e36130.https://doi.org/10.1371/journal.pone.0036130Rebecca M. Stumpf, Rodolfo Martinez-Mota, Krista M. Milich, Nicoletta Righini, Milena R. Shattuck Sexual conflict in primates, Evolutionary Anthropology: Issues, News, and Reviews 20, no.22 (Apr 2011): 62–75.https://doi.org/10.1002/evan.20297Matthew D. Hall, Simon P. Lailvaux, Mark W. Blows, Robert C. Brooks SEXUAL CONFLICT AND THE MAINTENANCE OF MULTIVARIATE GENETIC VARIATION, Evolution 64, no.66 (Dec 2009): 1697–1703.https://doi.org/10.1111/j.1558-5646.2009.00932.xAdrian L. O’Loghlen, Stephen I. Rothstein Multimodal signalling in a songbird: male audiovisual displays vary significantly by social context in brown-headed cowbirds, Animal Behaviour 79, no.66 (Jun 2010): 1285–1292.https://doi.org/10.1016/j.anbehav.2010.03.001Ryne A. Palombit Conflict and Bonding Between the Sexes, (Sep 2009): 53–83.https://doi.org/10.1007/978-3-642-02725-3_3John Archer Does sexual selection explain human sex differences in aggression?, Behavioral and Brain Sciences 32, no.3-43-4 (Aug 2009): 249.https://doi.org/10.1017/S0140525X09990951KRISTA K. INGRAM, TORSTEN LAAMANEN, NALINI PUNIAMOORTHY, RUDOLF MEIER Lack of morphological coevolution between male forelegs and female wings in Themira (Sepsidae: Diptera: Insecta), Biological Journal of the Linnean Society 93, no.22 (Jan 2008): 227–238.https://doi.org/10.1111/j.1095-8312.2007.00922.xDarryl T. 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Reproductive Consequences of Population Divergence through Sexual Conflict

Sexual-selection research increasingly focuses on reproductive conflicts between the sexes [1–4]. Sexual conflict, divergent evolutionary interests of males and females [5], can cause rapid antagonistic coevolution of reproductive traits [6] and is a potentially powerful speciation engine [7–11]. This idea has theoretical and comparative support [10–12] but remains controversial [13–14]. Recent experimental evidence from Sepsis cynipsea indicates that populations with greater sexual conflict diverged more quickly; females were less likely to mate with males from other populations when flies had evolved under high levels of sexual conflict [15]. The consequences of this divergence have not been addressed, so here we assess two female fitness surrogates after 44 generations of evolving (and diverging) under three different levels of sexual conflict. Longevity after copulation was negatively associated with the degree of sexual conflict under which flies evolved, and housing females with males also reduced female longevity. Female lifetime reproductive success (LRS) also tended to decrease with increasing conflict. However, there was evidence of either sexual-selection fitness benefits at intermediate levels of sexual selection and conflict or inbreeding depression in the smallest populations (those with the lowest levels of conflict). Nevertheless, the results indicate that there can be a fitness load associated with sexual selection [2] and support claims that sexual conflict can lead to reproductive isolation [7–11, 15].

The quantitative genetics of sexual selection in the dung fly Sepsis cynipsea

AbstractIn the common dung or black scavenger fly Sepsis cynipsea (Diptera: Sepsidae) several morphological and behavioural male and female traits interact during mating. Previous studies show that males attempt to mount females without courtship, females use vigorous shaking behaviour in response to male mounting, the duration of shaking is an indicator of both direct and indirect female choice and sexual conflict, and larger males enjoy a mating advantage. We conducted a quantitative genetic paternal half sib study to investigate the genetic underpinnings of these traits, notably body size (the preferred trait) and the associated female preference, and to assess the relative importance of various models generally proposed to account for the evolution of sexually selected traits. Several morphological traits and female shaking duration were heritable, thus meeting a key requirement of all sexual selection models. In contrast, two traits indicative of male persistence in mating were not. Male longevity was also heritable and negatively correlated with his mating effort, suggesting a mating cost. However, the crucial genetic correlation between male body size and female shaking duration, predicted to be negative by both 'good genes' and Fisherian models and positive by the sexual conflict (or chase-away) model, was zero. This could be because of low power, or because of constraints imposed by the genetic correlation structure. Based on our rsults we conclude that discriminating sexual selection models by sole means of quantitative genetics is difficult, if not impossible.

The costs of avoiding matings in the dung fly Sepsis cynipsea

Mating is generally assumed to carry costs, particularly for females, which have to be traded off against each other and against the fitness benefits of mating. To understand any particular mating system and the evolution of sexual conflict, these costs have to be evaluated. Female dung flies, Sepsis cynipsea (Diptera: Sepsidae), typically attempt to dislodge mounted males by vigorous shaking. Such female reluctance to mate can only evolve if the cost of avoiding matings does not exceed the cost of copulation. We investigated female precopulatory costs of assessing and rejecting males in terms of increased predation, wing injuries, and (indirectly) energetics, all ultimately affecting mortality, and compared them to the costs of copulation assessed in this and a companion study. Females housed with a male had lower survivorship than females housed with another female. This was largely due to the costs of copulation rather than presumed energetic costs of avoiding males, which were minor. Male harassment augmented female wing injuries, which accumulate with age in the field and laboratory, but in laboratory experiments using one common predator, wing injuries did not increase the susceptibility of S. cynipsea to predation, nor did their mating behavior per se. Instead, predation was highest and survivorship lowest in all-male groups, probably because males are more active in search of females and harass each other. Overall, the precopulatory costs of mate assessment and rejection were low relative to the costs of copulating, explaining female reluctance behavior in this and possibly other species.

The costs of copulating in the dung fly Sepsis cynipsea

Finding, assessing, rejecting, and copulating with a mate is assumed to carry fitness costs, particularly for females, that have to be traded off against fitness benefits of mating such as increased fecundity, fertility, longevity, or better quality offspring. Female dung flies, Sepsis cynipsea (Diptera: Sepsidae), typically attempt to dislodge mounted males harassing them by vigorous shaking. Shaking duration has been shown to reflect both direct and indirect female choice in this species. The latter is an expression of the females' general reluctance to mate due to presumed costs of mating. We investigated the costs of copulation in the laboratory. Females were randomly assigned to one of three treatment groups and allowed to copulate either not at all, once, or twice. The males' armored genitalia injured females internally during copula. Injuries were visible as sclerotized scars in the female ovipositor, and their occurrence increased with mating frequency. Presumably due to these injuries, mated females showed higher mortality. This effect was statistically independent from additional costs of reproduction related to oviposition, as copulation also increased lifetime egg production and tended to augment oviposition rate (eggs per day), while fertility (proportion of offspring emerged) was unaffected. We thus found high mortality costs of copulating, indicating substantial sexual conflict, which helps explain female reluctance to mate in this species. Copyright 2002.

Strategic ejaculation in the common dung fly Sepsis cynipsea

Sperm competition has been a major selective force acting on male and female behaviour. Theory predicts that when sperm compete numerically, selection will favour males that vary the number of sperm they transfer with sperm competition risk. This often leads to increased copula duration when sperm competition risk is high, the selective advantage of which is increased paternity. We investigated the copulatory behaviour of the common dung fly Sepsis cynipsea in relation to male and female size, female mating status, age, and presence or absence of dung. This fly is unusual in that males mate-guard before copula while females use the sperm of previous males for their current clutch. Body size had no effect on copula duration, but duration of first copulations depended on female age, with older females having longer copulations. For females that copulated twice, there was an interaction between female age and mating status influencing copula duration: old females had longer copulations than young females, but second copulas were longer for young females. Residual testis size of nonvirgin males was smaller than for virgins, and testis shrinkage was significantly associated with copula duration, which indicates that males transfer more ejaculate with longer copulations. We therefore conclude that copulation duration and ejaculate transfer vary in accordance with sperm competition theory.