Home About us Contact
|
Home About us Contact | ||
|
|
||
Mate Competition (mate + competition)
Kinds of Mate Competition Selected AbstractsCHARACTER DISPLACEMENT AS THE "BEST OF A BAD SITUATION": FITNESS TRADE-OFFS RESULTING FROM SELECTION TO MINIMIZE RESOURCE AND MATE COMPETITIONEVOLUTION, Issue 10 2005Karin S. Pfennig Abstract Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected. [source] Can the extremely female-biased sex ratio of the social spider mites be explained by Hamilton's local mate competition model?ECOLOGICAL ENTOMOLOGY, Issue 6 2007YUKIE SATO Abstract 1.,Extremely female-biased sex ratios are known in the social spider mite species, Stigmaeopsis longus and S. miscanthi. Whether Hamilton's local mate competition (LMC) theory can explain such sex ratios was investigated. 2.,Significant changes of the progeny sex ratios in the direction predicted by the LMC model were found in both species when the foundress number changed. Therefore, LMC can partly explain the skewed sex ratios in these species. 3.,When the foundress number increased, the progeny sex ratio was still female biased and significantly different from the prediction of the LMC model for haplodiploidy. Relatedness between foundresses could not fully explain the female-biased sex ratios. Therefore, these results suggest that there are factors other than LMC skewing the sex ratios of these species toward female. [source] Coexistence of cryptic speciesECOLOGY LETTERS, Issue 3 2004Da-Yong Zhang Abstract Recent discovery of cryptic species in fig-pollinating wasps creates a puzzle for the ecological competition theory: how do two or more apparently identical species coexist? Conventional theory predicts that they should not. Chesson (Trends Ecol. Evol., 1991, 6, 26,28) identified one exception which he considered unlikely to occur in reality: coexistence might be possible if appropriate social behaviour was discriminately directed towards conspecifics and heterospecifics. Here we present an example of the exception by showing that two identical species with local mate competition and population size-dependent sex ratio adjustment may coexist. The new findings about fig-pollinating wasps provide a putative example of unexpected coexistence of identical competitors via this mechanism. [source] UNEXPLAINED SPLIT SEX RATIOS IN THE NEOTROPICAL PLANT-ANT, ALLOMERUS OCTOARTICULATUS VAR. DEMERARAE (MYRMICINAE): A TEST OF HYPOTHESESEVOLUTION, Issue 1 2010Gabriel D. G. Debout We investigated sex allocation in the Neotropical ant Allomerus octoarticulatus var. demerarae. Because Allomerus is a plant symbiont, we could make geographically extensive collections of complete colonies and of foundresses in saplings, allowing us to estimate not only population- and colony-level sex allocation but also colony resource levels and the relatednesses of competing ant foundresses. This species exhibits a strongly split sex ratio, with 80% of mature colonies producing ,90% of one sex or the other. Our genetic analyses (DNA microsatellites) reveal that Allomerus has a breeding system characterized by almost complete monogyny and a low frequency of polyandry. Contrary to theoretical explanations, we find no difference in worker relatedness asymmetries between female- and male-specialist colonies. Furthermore, no clear link was found between colony sex allocation and life history traits such as the number of mates per queen, or colony size, resource level, or fecundity. We also failed to find significant support for male production by workers, infection by Wolbachia, local resource competition, or local mate competition. We are left with the possibility that Allomerus exhibits split sex ratios because of the evolution of alternative biasing strategies in queens or workers, as recently proposed in the literature. [source] EVOLUTIONARY PATHWAYS IN SHOREBIRD BREEDING SYSTEMS: SEXUAL CONFLICT, PARENTAL CARE, AND CHICK DEVELOPMENTEVOLUTION, Issue 10 2005Gavin H. Thomas Abstract Sexual selection, mating opportunities, and parental behavior are interrelated, although the specific nature of these relationships is controversial. Two major hypotheses have been suggested. The parental investment hypothesis states that the relative parental investment of the sexes drives the operation of sexual selection. Thus, the sex that invests less in offspring care competes more intensely and monopolizes access to mates. The sexual conflict hypothesis proposes that sexual selection (the competition among both males and females for mates), mating opportunities, and parental behavior are interrelated and predicts a feedback loop between mating systems and parental care. Here we test both hypotheses using a comprehensive dataset of shorebirds, a maximum-likelihood statistical technique, and a recent supertree of extant shorebirds and allies. Shorebirds are an excellent group for these analyses because they display unique variation in parental care and social mating system. First, we show that chick development constrains the evolution of both parental care and mate competition, because transitions toward more precocial offspring preceded transitions toward reduced parental care and social polygamy. Second, changes in care and mating systems respond to one another, most likely because both influenced and are influenced by mating opportunities. Taken together, our results are more consistent with the sexual conflict hypothesis than the parental investment hypothesis. [source] Dispersal pattern of domestic cats (Felis catus) in a promiscuous urban population: do females disperse or die?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2003Sébastien Devillard Summary 1The domestic feral cat (Felis catus L.) is a good model for studying intraspecific variability of dispersal patterns in mammals because cats live under a large diversity of socio-ecological conditions. We analysed both the natal and breeding dispersal patterns of domestic cats in a promiscuous urban population and tested whether or not it differed from the male-biased natal dispersal pattern observed for polygynous rural populations. 2During an 8-year study we recorded the exact date of in situ death for 148 marked cats and the exact date of disappearance from the population for 99 other cats. Because undiscovered deaths might over-estimate dispersal probabilities when considering only disappearance probabilities, we made an novel application of multistrata capture,recapture methods in order to disentangle dispersal from true mortality. 3We showed that mature females dispersed, both before and after their first reproduction, at 1 and 2 years old. Contrary to females, no dispersal seemed to occur in males. Before sexual maturity, females that disappeared at 1 and 2 years old were in worse body condition than females that stayed in the population area after 2 years old. However, they did not reproduce less successfully before their disappearance than females that died later in the population area. 4The female-biased and low natal dispersal pattern in this population was atypical compared to other promiscuous/polygynous mammals and differed from that observed in rural polygynous populations of domestic cat. Neither local mate competition nor inbreeding avoidance appeared to be sufficient pressures to counterbalance ecological constraints on dispersal in an urban environment. However, local resource competition for den sites between potential matriarchies could lead to the breeding dispersal of less competitive females. [source] Effects of sex, status, and mating cues on expected aggressive responsesAGGRESSIVE BEHAVIOR, Issue 3 2009Heather K. Terrell Abstract The effect of sex, status, and mating cues on expected aggression was examined via three scenario-based studies in which participants imagined themselves in a situation with a same-sex instigator of a provocation. Participants were randomly assigned to receive a scenario, which included one of two levels of status of instigator (high, low), one of two levels of attractiveness of the instigator (unattractive, attractive), and one of two levels of provocation (apology, insult). Sex and dispositional aggressivity were also included in a full factorial design. Based on evolutionary psychology ideas, we anticipated that status and attractiveness would differentially influence expected aggression for men vs. women. Participants in Experiment 1 were instructed to imagine that they were alone, whereas participants in Experiments 2 and 3 imagined themselves in a situation that included mating-related primes. In general expected aggression was greater for aggression-prone participants and under conditions of provocation and/or a high-status instigator. Experiments 2 and 3 found that, in the context of mate competition, sex differences in the effects of instigator provocation, status, and attractiveness emerged: greater aggressivity now only predicted more aggression for males but not females who were insulted; aggression was highest for females confronting an unattractive, high-status instigator and for males confronting an attractive, high-status instigator; females were more likely to aggress against a high-status instigator, regardless of being in a steady relationship or a first date situation, but males were only more likely to aggress against a high-status instigator in a first date situation. Aggr. Behav. 35:259,273, 2009. © 2009 Wiley-Liss, Inc. [source] Evolution of sexual size monomorphism: the influence of passive mate guardingJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 7 2009A. E. DUNHAM Abstract Some species have potential for intense mate competition yet exhibit little or no sexual size dimorphism, despite predictions from sexual selection theory. Using a conceptual model, we show the conditions for which passive mate guarding with copulatory plugs can be an alternative and more successful strategy to active (direct) guarding, reducing selection pressure on large male size. The model predicts that copulatory plugs in mammals should be favoured in species for which females have short sexual receptivity periods. Using data on 62 primate species and a phylogenetic regression approach, we show that, as predicted, copulatory plugs are negatively associated with degree of sexual dimorphism and females' sexual receptivity length. Penile spines are also significantly associated with plug use and short receptivity periods suggesting a possible offensive role in sperm competition. Results highlight that life-history characteristics, such as sexual receptivity lengths, may alter the costs and benefits of alternative male strategies and thus alter the strength of sexual selection. [source] | ||||||||||