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In poeciliid fish, the evolution of the placenta is associated with polyandry in females and correlates with a suite of phenotypic and behavioural traits in males. Consequences of placenta evolution Females laying eggs for external fertilization have no control over the quality of the offspring, and must rely on proxies of male quality such as courtship and display traits. Evolutionary theory holds that all this changed with the advent of the placenta: with low-cost eggs incubated internally, a mother can hedge her bets, inspecting the genetic quality of her mates directly and provisioning her embryos accordingly. The resulting mother-offspring conflict is expected to lead to polyandry (females mating with multiple males) and to males that are smaller, less showy and more prone to opportunistic or 'sneaky' mating. Here Bart Pollux et al. test these ideas by looking at the Poecilidae -- guppies and their relatives -- a family of fish in which the various species show all varieties of internal and external fertilization, and in which the placenta has evolved at least eight times independently. This approach allows the authors to confirm that the evolution of the placenta is associated with polyandry in females, and smaller, less showy males that have longer penises to facilitate more opportunities for opportunistic mating. The evolution of the placenta from a non-placental ancestor causes a shift of maternal investment from pre- to post-fertilization, creating a venue for parent-offspring conflicts during pregnancy.sup.1,2,3,4. Theory predicts that the rise of these conflicts should drive a shift from a reliance on pre-copulatory female mate choice to polyandry in conjunction with post-zygotic mechanisms of sexual selection.sup.2. This hypothesis has not yet been empirically tested. Here we apply comparative methods to test a key prediction of this hypothesis, which is that the evolution of placentation is associated with reduced pre-copulatory female mate choice. We exploit a unique quality of the livebearing fish family Poeciliidae: placentas have repeatedly evolved or been lost, creating diversity among closely related lineages in the presence or absence of placentation.sup.5,6. We show that post-zygotic maternal provisioning by means of a placenta is associated with the absence of bright coloration, courtship behaviour and exaggerated ornamental display traits in males. Furthermore, we found that males of placental species have smaller bodies and longer genitalia, which facilitate sneak or coercive mating and, hence, circumvents female choice. Moreover, we demonstrate that post-zygotic maternal provisioning correlates with superfetation, a female reproductive adaptation that may result in polyandry through the formation of temporally overlapping, mixed-paternity litters. Our results suggest that the emergence of prenatal conflict during the evolution of the placenta correlates with a suite of phenotypic and behavioural male traits that is associated with a reduced reliance on pre-copulatory female mate choice., Author(s): B. J. A. Pollux [sup.1] [sup.2] , R. W. Meredith [sup.1] [sup.3] , M. S. Springer [sup.1] , T. Garland [sup.1] , D. N. Reznick [sup.1] Author Affiliations: (1) [...]

To understand the processes that maintain genetic diversity is a long-standing challenge in evolutionary biology, with implications for predicting disease resistance, response to environmental change, and population persistence (1-3). Simple population genetic models are not sufficient to explain the high levels of genetic diversity sometimes observed in ecologically important traits (2). In guppies (Poecilia reticulata), male colour pattern is both diverse and heritable, and is arguably one of the most extreme examples of morphological polymorphism known (4,5). Negative frequency-dependent selection (NFDS), a form of selection in which genotypes are favoured when they are rare (6), can potentially maintain such extensive polymorphism, but few experimental studies have confirmed its operation in nature (7,8). Here we use highly replicated experimental manipulations of natural populations to show that males with rare colour patterns have higher reproductive fitness, demonstrating NFDS mediated by sexual selection. Rare males acquired more mates and sired more offspring compared to common males and, as previously reported, had higher rates of survival (8). Orange colour, implicated in other studies of sexual selection in guppies, did predict male reproductive success, but only in one of three populations. These data support the hypothesis that NFDS maintains diversity in the colour patterns of male guppies through two selective agents, mates and predators. Similar field-based manipulations of genotype frequencies could provide a powerful approach to reveal the underlying ecological and behavioural mechanisms that maintain genetic and phenotypic diversity., Populations of organisms exhibit enormous genetic diversity. Explaining this diversity has been challenging, particularly when variation occurs in traits under strong natural selection (1,3). High genetic variation in ecologically important [...]

An individual optimizes its reproductive success by adopting a particular reproductive strategy. Studying the details of a reproductive strategy leads to an understanding of how sexual selection acts, as the former is the process via which the individual reproduces successfully. Hermaphroditic gastropods display a bewildering diversity of reproductive strategies, which may be due to their mode of gender expression, when compared with well-studied separate-sexed species. Extensive theoretical, observational, and experimental research has been conducted on this topic. However, despite our knowledge about the reproductive system of hermaphroditic gastropods, we still need to fill the gap between pre- and post-copulatory processes and reproductive success. Here, we review and propose conceptual and empirical approaches aimed at understanding reproductive strategies of hermaphroditic gastropods. In sum, our suggestions are (i) to focus on sex-biased traits, (ii) to take biologically reliable measurements at both the pre- and post-copulatory level that relate to reproductive success, and (iii) to examine the fitness consequences of biased sex allocation. Key words: hermaphrodite, paternity longevity, reproduction, sperm competition, sperm storage, sex allocation, sexual selection. Les individus optimisent leur succes de reproduction en adoptant des strategies reproductives qui leur sont propres. L'etude des details d'une strategie de reproduction permet une meilleure comprehension des mecanismes de selection sexuelle, puisqu'il s'agit du processus par lequel l'individu se reproduit avec succes. Comparativement a des especes bien etudiees dont les sexes sont distincts, les gasteropodes hermaphrodites presentent une extreme diversite de strategies de reproduction qui pourrait etre le fait du mode d'expression du sexe. De nombreux travaux theoriques, experimentaux et d'observation sur ce theme ont deja ete realises. Cependant, malgre les connaissances acquises sur le systeme reproducteur de gasteropodes hermaphrodites, le lien entre les processus pre- et post-copulatoires et le succes de reproduction n'est pas encore bien etabli. Nous passons en revue et proposons des approches conceptuelles et empiriques visant a mieux comprendre les strategies de reproduction des gasteropodes hermaphrodites. Nous suggerons (i) de mettre l'accent sur les caracteres dont la distribution depend du sexe, (ii) de prendre des mesures fiables sur le plan biologique aux stades pre- et post-copulatoires, qui sont reliees au succes de reproduction et (iii) d'examiner les consequences d'une determination asymetrique des sexes sur l'aptitude. [Traduit par la Redaction] Mots-cles : hermaphrodite, longevite de la paternite, reproduction, concurrence des spermatozoides, stockage des spermatozoides, determination du sexe, selection sexuelle., Introduction A reproductive strategy is defined as a set of (behavioural, morphological, physiological) traits that optimize reproductive success of an individual under given local conditions. Basically, for sexually reproducing organisms, [...]

We report genital coupling of Drosophila teissieri Tsacas, 1971, a member of the Drosophila melanogaster species subgroup. The species subgroup consists of nine described species including the model organism Drosophila melanogaster Meigen, 1830. Despite numerous studies on the biology of this group, our understanding of the evolutionary significance of the diversity in their genital structures is limited. This study provides evidence that (i) during the copulation, which lasts 41.1 min, a paired male genital part (dorsal branches of the basal processes of the aedeagus) open after being inserted into the female reproductive tract, (ii) female D. teissieri have a pair of pockets on the dorsal side of their genitalia that receive bifurcated spines of the male genitalia (ventral branches of the basal processes of the aedeagus), and (iii) male genital parts, especially unique strong spines of the cerci, cause multiple copulatory wounds on membranous areas of the female genitalia. Within the established phylogeny of the D. melanogaster species subgroup, we discuss possible functions of and evolutionary transitions in these genital structures. Key words: copulatory wounding, damaging mating, Drosophila teissieri, evolution of genitalia, sexual selection, transparentizing technique. Nous faisons etat de l'accouplement genital de Drosophila teissieri Tsacas, 1971, un membre du sous-groupe d'especes de Drosophila melanogaster. Ce sous-groupe d'especes compte neuf especes decrites dont l'organisme modele Drosophila melanogaster Meigen, 1830. Bien que la biologie de ce groupe ait fait l'objet de nombreuses etudes, la comprehension de la signification evolutionnaire de la diversite de ses structures genitales demeure limitee. L'etude indique que (i) durant la copulation, qui dure 41,1 min, une paire de pieces genitales males (branches dorsales des processus basaux de l'edeage) s'ouvre apres avoir ete inseree dans le tube reproducteur de la femelle, (ii) les D. teissieri femelles ont une paire de poches sur le cote dorsal de leurs genitalia qui recoivent des epines bifurquees des genitalia males (branches ventrales des processus basaux de l'edeage) et (iii) les pieces genitales males, particulierement de robustes epines des cerques, un caractere particulier a cette espece, causent de nombreuses lesions copulatoires sur les zones membraneuses des genitalia de la femelle. Nous abordons les fonctions possibles de ces structures genitales et leurs transitions evolutionnaires dans le contexte de la phylogenie etablie du sous-groupe d'especes de D. melanogaster. Mots-cles: lesion copulatoire, dommages dus a l'accouplement, Drosophila teissieri, evolution des genitalia, selection sexuelle, technique d'augmentation de la transparence. [Traduit par la Redaction], Introduction Animal genitalia that are used for copulation and sperm transfer, especially male organs, are often more complex than is necessary for sperm transfer alone, and they seem to evolve [...]

In species with multiple mating and long-term sperm storage, males are expected to show a preference for mating with virgin and young females to reduce the risk of sperm competition. In various simultaneous hermaphrodite land snail species, sperm production precedes egg production by 2-4 weeks, resulting in a short period of protandric hermaphroditism before shell growth is completed. In a natural population, we collected copulating pairs of the simultaneous hermaphrodite land snail Arianta arbustorum (L., 1758) consisting either of two adults, of two subadults, or of one adult and one subadult snail, and determined the paternity of their hatchlings that emerged from subsequently deposited eggs. Adult snails used sperm received from subadult mating partners for egg fertilization in the same frequency as sperm from adults, indicating that subadult and adult snails do not differ in male function. Furthermore, an unfinished shell is not a reliable indicator for virginity, because 35% of the subadult individuals had already sperm stored from previous mating(s). Compared with adults, young individuals exhibited a lower risk of sperm competition, indicated by a higher last mate sperm precedence. However, subadult snails produced fewer eggs than adult snails, counteracting the evolutionary advantage of preferring a young partner with low sperm competition risk. Chez les especes a accouplements multiples et a stockage a long terme des spermatozoides, on s'attend a ce que les males montrent une preference pour l'accouplement avec des femelles jeunes et vierges afin de reduire le risque de competition spermatique. Chez divers escargots terrestres a hermaphroditisme simultane, la production de spermatozoides precede la production des oeufs de 2-4 semaines, ce qui resulte en une periode d'hermaphroditisme protandrique avant la fin de la croissance de la coquille. Nous avons preleve dans une population naturelle des paires accouplees de l'escargot terrestre a hermaphroditisme simultane Arianta arbustorum (L., 1758) comprenant ou bien deux adultes, ou deux subadultes ou alors un adulte et un subadulte; nous avons ensuite determine la paternite des nouveau-nes issus des oeufs qui ont ete subsequemment deposes. Les escargots adultes utilisent le sperme recu de leurs partenaires d'accouplement subadultes a la meme frequence que le sperme provenant des adultes, ce qui indique qu'il n'y a pas de difference dans la fonction male entre les subadultes et les adultes. De plus, une coquille incomplete n'est pas un indicateur fiable de virginite, puisque 35 % des individus subadultes possedent deja du sperme accumule a partir d'un ou plusieurs d'accouplements anterieurs. Par rapport aux adultes, les jeunes affichent un risque plus faible de competition spermatique, ce qui est indique par une preseance plus forte du sperme du dernier partenaire. Cependant, les escargots subadultes produisent moins d'oeufs que les adultes, ce qui contrecarre l'avantage evolutif qu'il y a a preferer un partenaire jeune a faible risque de competition spermatique. [Traduit par la Redaction], Introduction Sexual selection in animals may act before or after copulation. Precopulatory mechanisms include male competition and female mate choice (Birkhead and Moller 1998), whereas sperm competition and cryptic female [...]

Male mating success is often determined by body size or secondary sexual characters because of female mate choice or competition for females. In addition to intraspecific interactions, interspecific interactions may interfere with intraspecific selection. In this study, we investigated sexual selection on size and sexual characters of male banded demoiselle (Calopteryx splendens (Harris, 1780)) in wild populations sympatric with the beautiful demoiselle (Calopteryx virgo (L., 1758)). As secondary sexual characters, male C. splendens have pigmented wing spots whose size appears to be under positive selection. Male C. virgo resemble male C. splendens that have the largest wing spots, leading to interspecific male-male aggression and possibly also to heterospecific matings via mistaken species recognition. If interspecific interactions interfere with intraspecific sexual selection on wing-spot size of C. splendens, their effects should increase with the increasing relative abundance of C. virgo. Our results did not show the expected positive selection on wing-spot size in C. splendens, suggesting that interspecific interactions might interfere with sexual selection. Also, we observed no relationship between the strength of interspecific sexual selection and the relative abundance of C. virgo. However, there was a positive intraspecific density-dependent sexual selection for larger size. Although the present results are tentative, we suggest that interspecific interactions should be considered along with intraspecific selection when studies of sexual selection are performed in the wild. Resume : Le succes de l'accouplement chez les males est souvent determine par la taille corporelle ou par d'autres caracteres sexuels secondaires a cause du choix des partenaires par les femelles ou de la competition pour les femelles. En plus des interactions intraspecifiques, les interactions interspecifiques peuvent s'interposer dans la selection intraspecifique. Notre etude examine la selection sexuelle de la taille et des caracteres sexuels des demoiselles males (Calopteryx splendens (Harris, 1780)) dans des populations sauvages qui coexistent avec Calopteryx virgo (L., 1758). Les males de C. splendens possedent comme caracteres sexuels secondaires des taches pigmentees sur les ailes dont la taille semble etre l'objet d'une selection positive. Les males de C. virgo ressemblent aux males de C. splendens qui possedent les taches les plus grandes sur les ailes, ce qui mene a de l'agression interspecifique entre les males et peut-etre aussi a des accouplements heterospecifiques a cause d'une mauvaise identification de l'espece. Si les interactions interspecifiques nuisent a la selection sexuelle intraspecifique basee sur les taches alaires chez C. splendens, leurs effets devraient augmenter en fonction de l'accroissement de l'abondance relative de C. virgo. Nos resultats n'indiquent pas la selection positive attendue de la taille de la tache alaire chez C. splendens, ce qui laisse croire que les interactions interspecifiques peuvent nuire a la selection sexuelle. Nous n'observons pas non plus de relation entre la force de la selection sexuelle interspecifique et l'abondance relative de C. virgo. Toutefois, il existe une selection sexuelle intraspecifique positive des tailles plus grandes qui est dependante de la densite. Bien que nos resultats soient preliminaires, nous croyons que les interactions interspecifiques doivent etre prises en consideration au meme titre que la selection intraspecifique dans les etudes de selection sexuelle en nature. [Traduit par la Redaction], Introduction Sexual selection is competition within a sex for access to gametes of the opposite sex (Kokko et al. 2006; Jennions and Kokko 2010). The observed pattern is often such [...]

Male pregnancy in seahorses, pipefishes and sea dragons (family Syngnathidae) represents a striking reproductive adaptation that has shaped the evolution of behaviour and morphology in this group of fishes (1-4). In many syngnathid species, males brood their offspring in a specialized pouch, which presumably evolved to facilitate male parental care (5,6). However, an unexplored possibility is that brood pouch evolution was partly shaped by parent-offspring or sexual conflict, processes that would result in trade-offs between current and future pregnancies. Here we report a controlled breeding experiment using the sexually dimorphic Gulf pipefish, Syngnathus scovelli, to test for post-copulatory sexual selection within broods and for trade-offs between successive male pregnancies as functions of female attractiveness. Offspring survivorship within a pregnancy was affected by the size of a male's mate, the number of eggs transferred and the male's sexual responsiveness. Significantly, we also found that embryo survivorship in a current pregnancy was negatively related to survivorship in the prior pregnancy, clearly demonstrating fitness trade-offs between broods. Overall, our data indicate that post-copulatory sexual selection and sexual conflict occur in Gulf pipefishes. The conflict seems to be mediated by a strategy of cryptic choice in which males increase rates of offspring abortion in pregnancies from unattractive mothers to retain resources for future reproductive opportunities. Hence, the male brood pouch of syngnathid fishes, which nurtures offspring (7-9), also seems to have an important role as an arbiter of conflict between the sexes., Male pregnancy, a phenomenon unique to seahorses and their relatives, is facilitated by an elaborate brood pouch into which a female deposits eggs during mating (10,11). Far from being a [...]

Sexual selection is among the most powerful of all evolutionary forces. It occurs when individuals within one sex secure mates and produce offspring at the expense of other individuals within the same sex. Darwin was first to recognize the power of sexual selection to change male and female phenotypes, and, in noting that sexual selection is nonubiquitous, Darwin was also first to recognize the importance of mating system--the 'special circumstances' in which reproduction occurs within species. Analyses of mating systems since Darwin have emphasized either the genetic relationships between male and female mating elements, usually among plants, or the numbers of mates males and females may obtain, usually among animals. Combining these schemes yields a quantitative methodology that emphasizes measurement of the sex difference in the variance in relative fitness, as well as phenotypic and genetic correlations underlying reproductive traits that may arise among breeding pairs. Such information predicts the degree and direction of sexual dimorphism within species, it allows the classification of mating systems using existing genetic and life history data, and with information on the spatial and temporal distributions of fertilizations, it may also predict floral morphology in plants. Because this empirical framework identifies selective forces and genetic architectures responsible for observed male-female differences, it compliments discoveries of nucleotide sequence variation and the expression of quantitative traits. Moreover, because this methodology emphasizes the process of evolutionary change, it is easier to test and interpret than frameworks emphasizing parental investment in offspring and its presumed evolutionary outcomes. animal breeding | opportunity for selection | plant breeding

In one of his few major oversights, Darwin failed to appreciate that male-male competition and sexual selection can continue even after copulation has begun. The postcopulatory equivalents of both direct male-male battles (sperm competition) and female choice (cryptic female choice) occur within the female's body. Recognition of this hidden, but intense, sexual competition provides new insights into a variety of fields. These include the hyperdiverse and paradoxically elaborate morphology of both sperm and male genitalia, the equally puzzling and elaborate morphology of nongenitalic male structures that are specialized to grasp and stimulate females, powerful manipulative effects of substances in male semen on female reproductive physiology, paradoxical male courtship behavior that occurs after copulation has already begun, variability in parental investments, and the puzzlingly complex and diverse interactions between sperm and female products that surround animal eggs and between male gametophytes and female tissues in flowering plants. Many bizarre traits are involved, including male genitalia that are designed to explode or fall apart during copulation leaving behind parts within the female, male genitalia that 'sing' during copulation, potent seminal products that invade the female's body cavity and her nervous system to influence her behavior, and a virtual Kama Sutra of courtship behavior performed after rather than before genital coupling, including male-female dialogues during copulation. cryptic female choice | sexually antagonistic coevolution

Upon mating, Drosophila melanogaster females undergo numerous alterations in their behavior and reproductive physiology that are accompanied by small-magnitude transcript-level changes in up to 1700 genes. Many of these postmating transcriptome changes are the direct result of the sperm and seminal fluid proteins (Acps) that females receive from their mates. To begin to determine if the genetic background of the female's mate contributes to the previously described gene expression changes, we assessed whether interactions between the genotypes of two commonly used laboratory strains of D. melanogaster (Canton-S and Oregon R) influence the female's postmating transcriptome as well as several pre- and postcopulatory phenotypes. We find negligible differences in the female's transcriptome at 1-3 hr postmating regardless of the strain of the male with whom she mated. However, a male x female genotype interaction significantly influenced mate selection, and, in some cases, fecundity, fertility, and hatchability. Our data support previous work suggesting that many of the early postmating changes observed in D. melanogaster females are not caused by large modifications of transcript levels. Instead, early postmating phenotypes result from preexisting receptors or pathways that are already in place upon sexual maturity.

In reply to Machin's criticism of Kohn and Mithen's (1999) 'Sexy Handaxe Theory' in a recent Antiquity debate (Machin 2008: 761-6), Mithen (2008: 766-9) states that sexual selection is still [...]

Reproductive effort should negatively correlate with reproductive value, yielding a pattern of increased effort with age. According to the terminal investment hypothesis, females near the end of their reproductive life span should devote more resources to reproduction than those near the start of their reproductive careers. We tested predictions of the terminal investment hypothesis by evaluating 38 years of reproductive life-history data collected from Nile lechwe (Kobus megaceros), an ungulate species living at San Diego Zoo's Wild Animal Park. The maximum reproductive success of Nile lechwe matched predictions of models of lifetime reproductive effort, with the relative mass of newborn calves providing an accurate indicator of the costs of reproduction. Newborn mass was significantly correlated with maternal age, and neonatal males tended to be heavier than neonatal females. Older dams were more likely to produce sons than daughters, dams that produced sons were more likely to die than were dams that produced daughters, and male calves were less likely to survive than were female calves. We conclude that young females endure a fertility cost while breeding, whereas older females encounter a survivorship cost, associated with progeny production. Our findings support the terminal investment hypothesis, and we suggest that secondary sex ratio bias among older female Nile lechwe reflects the evolution of a flexible life-history strategy promoting production of costly male calves when reproductive value is declining. Key words: Kobus, reproductive success, residual reproductive value, sex ratio adjustment, sexual selection, ungulates

Like many other mammals, Saccopteryx bilineata exhibits a polygynous mating system, in which each male defends a group of females called a harem. Colonies consist of several harems, and nonharem males roost adjacent to harems. Unlike most other mammals, females disperse from their natal colony and most juvenile males remain in it. Thus, colonies consist of patrilines, which promotes intense local mate competition. Females are in estrus during a few weeks at the end of the rainy season. Mating is most likely initiated by females and preceded by intense courtship displays of males. Forty percent of colony males do not sire any offspring during their tenure in the colony, whereas a few males can sire up to 6 offspring in a single year. Males use olfactory, visual, and acoustic signals for courtship, and they demonstrate territory ownership by scent marks, low-frequency calls, and visual displays. Harem males sire on average more offspring than do nonharem males but produce only 30% of the offspring within their own harem territory, with 70% being sired by other harem males or nonharem males. Reproductive success of males increases with decreasing size, fluctuating asymmetry, and fundamental frequency of territorial calls. In addition, females that are closely related to the harem holder are more likely to mate with other males than with the harem holder. Sexual selection in S. bilineata is most likely influenced by intense local mate competition caused by scarce roosts and the patrilineal organization of colonies. Key words: acoustic signals, female choice, harem, olfactory signals, polygynous mating system, sex-biased dispersal, visual signals

The wild boar (Sus scrofa) is a large, sexually dimorphic ungulate that exhibits a life-history tactic different from what would be predicted for a mammal of its size. In particular, litter size is larger and adult survival usually lower in wild boars than in other species of comparable size. We used capture-mark-recapture methods to model survival in a Mediterranean population (S. s. majori) of wild boars during an 8-year period, using a large sample of individually tagged animals of known age, to investigate demographic patterns and the effects of variable environmental conditions (e.g., summer droughts), which are believed to have a strong impact on the demography of this species. Contrary to the predictions based on our current knowledge of life-history theory, survival of wild boars differed less among age classes and between sexes than has been reported in other large mammals. As predicted from current theories on sexual selection, the impact of environmental factors was stronger on males than on females. This study documents for wild boars a life-history tactic different from the accepted model for large ungulates but similar to the tactic observed in small terrestrial mammals. Key words: capture-mark-recapture, life history, Mediterranean environments, sexual dimorphism, survival, Sus scrofa majori, wild boar

The mechanisms by which cancer evolves and persists in natural systems have been difficult to ascertain. In the Xiphophorus melanoma model, a functional oncogene (Xiphophorus melanoma receptor kinase Xmrk) has been maintained for several million years despite being deleterious and in an extremely unstable genomic region. Melanomas in Xiphophorus spp. fishes (platyfishes and swordtails) have been investigated since the 1920s, and, yet, positive selection that could explain the maintenance of Xmrk has not been found. Here, we show that Xiphophorus cortezi females from two populations prefer males with the spotted caudal (Sc) melanin pattern, which is associated with the presence of the Xmrk oncogene and serves as the site of melanoma formation within this species. Moreover, X. cortezi females prefer males with an enhanced Sc to males with a reduced Sc pattern. RT-PCR analysis confirms tissue-specific Xmrk expression within the Sc pattern in X. cortezi. Because of the association of Xmrk with the Sc pigment pattern and the fact that melanoma formation augments this visual signal, sexual selection appears to be maintaining this oncogene because of a mating preference for Sc, as well as the exaggeration of this male trait. At the individual level, decreases in viability and fecundity because of Xmrk and subsequent melanoma formation may be mitigated via increases in mate acquisition. At the population level, maintenance of this oncogene appears to be under frequency dependent selection, as we detected female preference for males without Sc in a third population that had higher frequencies of Sc in females. cancer | evolution | sexual selection | Xiphophorus | Xmrk

Abstract: Female Columbian ground squirrels (Spermophilus columbianus (Ord, 1815)) sometimes emit a repetitive vocalization after copulation. We examined two possible explanations for why sexual selection would favor expression of these [...]

Molecular measures of parentage provide important insights into the opportunity for sexual selection; in birds, such studies have been conducted almost exclusively on pair-bonded passerines. Here I employ a multitiered parentage analysis involving 10-locus microsatellite genotypes to characterize the genetic mating system of a population of Wild Turkeys (Meleagris gallopavo), a promiscuous species in which males and potentially females have been thought to mate multiply. Young in almost half of nests (48%, n = 15) were each apparently the product of a single male and female parent. Fourteen broods (45%) resulted from multiple paternity; seven contained eggs from multiple females, four of which appeared to be cases of quasi parasitism, in which the offspring of the brood parasitic female were fathered by the same male that sired at least one of the host females' offspring. Bateman gradients for males and females indicate that males experience a significantly greater gain in reproductive success from additional mates; the trend for females to benefit from multiple matings disappeared when the small 'clutches' of parasitic females were excluded from the analysis. Of the components of variance in male fitness, number of mates was the most important determinant of male reproductive success. Somewhat surprisingly, when considering only reproductively successful males, the proportion of a female's offspring that a male sired also explained a substantial proportion of the total variance in male reproductive success. Incomplete sampling of offspring could mean that these estimates, particularly the importance of mate number, may be underestimated. Regardless, these results suggest that multiple mating by females may be an important and overlooked component of sexual selection in species with lek-like mating systems, and that selection may act independently on males to attract more mates and increase their share of paternity with those mates. Key words: Bateman gradient, brood parasitism, kin selection, microsatellite, opportunity for selection, polyandry, polygyny. Las medidas moleculares de paternidad proveen informacion importante sobre las oportunidades para la seleccion sexual. En las aves tales estudios han sido llevados a cabo de manera casi exclusiva con paserinos que mantienen vinculos de pareja. En el presente estudio empleo un analisis de paternidad de multiples niveles utilizando genotipos basados en 10 sitios microsatelitales para caracterizar el sistema de apareamiento genetico de una poblacion de Meleagris gallopavo. Esta es una especie promiscua en la cual los machos, y potencialmente las hembras, se aparean de manera multiple. Casi la mitad de los nidos (48%, n = 15) fueron el producto de una madre y un padre. Catorce nidos (45%) fueron el resultado de paternidad multiple, siete contenian huevos de multiples hembras y, de estos siete, cuatro aparentan ser casos de quasi-parasitismo en el cual las crias de la hembra parasitica eran del mismo padre que al menos una de las crias de la hembra huesped. Los gradientes de Bateman para machos y hembras indican que los machos obtienen un aumento significativamente mayor en el exito reproductivo cuando se aparean con mas parejas; la tendencia en la cual las hembras obtenian beneficios del apareamiento multiple desaparecio cuando se excluyeron del analisis las puestas pequenas de las hembras parasiticas. Al examinar los componentes de varianza en la aptitud biologica de los machos, el componente mas importante del exito reproductivo de los machos fue el mimero de parejas. Al considerarse solamente los machos que tuvieron exito reproductivo, la proporcion de crias de la hembra que el macho engendro tambion explico una porcion substancial de la varianza en el exito reproductivo total de los machos. El muestreo incompleto de las crias podria significar que estos estimados pueden set subestimaciones, en particular la importancia del mimero de parejas. Sin embargo, estos resultados sugieren que el apareamiento multiple de hembras podria ser un componente importante y frecuentemente desapercibido de la seleccion sexual en especies con sistemas de apareamiento tipo lek y que la seleccion podria actuar independientemente sobre los machos para atraer mas parejas y para incrementar la proporcion de crias engendradas con esas parejas.

Many scarab beetles produce rigid projections from the body called horns. The exaggerated sizes of these structures and the staggering diversity of their forms have impressed biologists for centuries. Recent comparative studies using DNA sequence-based phylogenies have begun to reconstruct the historical patterns of beetle horn evolution. At the same time, developmental genetic experiments have begun to elucidate how beetle horns grow and how horn growth is modulated in response to environmental variables, such as nutrition. We bring together these two perspectives to show that they converge on very similar conclusions regarding beetle evolution. Horns do not appear to be difficult structures to gain or lose, and they can diverge both dramatically and rapidly in form. Although much of this work is still preliminary, we use available information to propose a conceptual developmental model for the major trajectories of beetle horn evolution. We illustrate putative mechanisms underlying the evolutionary origin of horns and the evolution of horn location, shape, allometry, and dimorphism. allometry development | phenotypic plasticity | sexual selection | weapons

Male mating tactics can vary according to the potential for scramble or contest competition but also as a consequence of individual characteristics, such as body condition and previous experience. The influence of experience, i.e., residency, on male recapture rates and reproductive success was studied in a population of free-living grey mouse lemurs. Long-term capture data from 320 individuals revealed that both sexes had very low recapture probabilities within their first year in the study population, but recapture rates declined less sharply during the following years. Capture results and telemetric analyses on 12 focal males revealed that resident males had larger body mass and larger home ranges than new males. Home range size correlated with the number of accessible females, indicating that resident males had higher probabilities to meet mates than new males. The reproductive success of 132 candidate fathers, representing both resident and new males, was determined by means of molecular genotyping. Paternity determination was successful in 38 cases (success rate: 19%). Sixteen resident males and seventeen new males sired offspring. However, in relation to the number of candidate fathers being present in the mating season, resident males were twice as likely to reproduce successfully as new males. These findings suggest experiencedependent reproductive tactics that most likely correspond to a differential spatial knowledge of resources, mates and potential threats. The results generally agree with the predictions made for a scramble competition regime and demonstrate substantial behavioral plasticity in a nocturnal primate species with a dispersed multi-male/ multi-female mating system. KEY WORDS Sexual selection; intrasexual competition; survival analysis; mating tactics

Nectar production may disproportionately benefit male relative to female pollination success. In such cases, sexual selection is often suggested as the cause of asymmetric benefits, yet sexual selection in plants--particularly plants with hermaphroditic flowers--is infrequently tested empirically. Here, I used a protandrous herb with male-biased nectar production (Chrysothemis friedrichsthaliana, Gesneriaceae) to test predictions from sexual selection theory. During three flowering seasons, I measured nectar production, pollinator visits, and male and female fecundity following different numbers of cross-pollination events. In accordance with sexual selection predictions, (1) nectar production was greater during the male phase by at least 65%; (2) visits by the main pollinator (hummingbird Phaethornis striigularis) were limiting for part of the season, indicating that plants had to compete for pollinator visits; (3) pollinators spent 53% more time per visit and made 86% more visits to male- vs. female-phase flowers, suggesting that nectar increased male more than female pollination success; and (4) female fecundity was maximized by one visit, whereas male fecundity continued to increase with additional visits. Autonomous self-pollination further reduced visit requirements for maximum female seed set. These findings match specific sexual selection predictions: they link an observable male bias in a secondary sexual trait (nectar) to positive responses of mating participants (pollinators), resulting in more mating opportunities for mate-limited males, relative to apparently resource-limited females. This field-testing of theoretical predictions provides unique evidence that sexual selection helps maintain nectar production patterns in this and, quite likely, other hermaphroditic plant species. Key words: Chrysothemis friedrichsthaliana; Costa Rica; Gesneriaceae; hummingbird pollination; nectar; Phaethornis striigularis; pollinator-mediated selection; sexual selection.

Reconstructed patterns of vocal evolution in the New world orioles are compared to reconstructed patterns of change in plumage evolution. Both show repeated convergence in overall patterns hinting that both these character classes are highly labile but conserved within the genus.

Empirical evidence refutes the theory that sexually selected traits usually exhibit positive static allometries. It suggests that very few sexual traits exhibit positive allometry and directional sexual selection does not always produce positive allometry.