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Positive Assortative Mating (positive + assortative_mating)
Selected AbstractsInterspecific and intraspecific differences in two Liriomyza leafminer species in CaliforniaENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2002Stuart R. Reitz Abstract In recent years, the pest status of Liriomyza trifolii (Burgess) and L. huidobrensis (Blanchard) (Diptera: Agromyzidae) has changed in California, as well as other areas of the world. In California, L. huidobrensis has become the predominant Liriomyza species in valleys along the central coast, while L. trifolii remains the predominant species in southern California. To investigate possible reasons for this change in status, differences in host plant use and reproductive success of intraspecific populations were examined for Liriomyza trifolii and L. huidobrensis from both central and southern California. The southern L. trifolii fed, oviposited and reproduced successfully on all five hosts tested, but the central population fed significantly less on all hosts and was restricted to reproducing on pepper only. With the exception of pepper, southern L. trifolii had significantly greater larval survival on all hosts than central L. trifolii. In contrast, the central L. huidobrensis population had greater reproductive success than the southern population of that species on all hosts plants tested. However, pepper was not a suitable host for either L. huidobrensis population. Both species showed positive assortative mating, with homotypic mating occurring more frequently than heterotypic mating; however, the difference between L. trifolii populations was much more pronounced than between L. huidobrensis populations. These data indicate that central and southern California populations of each species are distinct biotypes. Furthermore when coupled with previous genetic data, our results suggest the possible existence of cryptic species within L. trifolii. [source] EVOLUTION OF REPRODUCTIVE ISOLATION WITHIN A PARASITIC FUNGAL SPECIES COMPLEXEVOLUTION, Issue 7 2007Mickael Le Gac Despite important advances in the last few years, the evolution of reproductive isolation (RI) remains an unresolved and critical gap in our understanding of speciation processes. In this study, we investigated the evolution of RI among species of the parasitic fungal species complex Microbotryum violaceum, which is responsible for anther smut disease of the Caryophyllaceae. We found no evidence for significant positive assortative mating by M. violaceum even over substantial degrees of genetic divergence, suggesting a lack of prezygotic isolation. In contrast, postzygotic isolation increased with the genetic distance between mating partners when measured as hyphal growth. Total RI, measured as the ability of the pathogen to infect and produce a diploid progeny in the host plant, was significantly and positively correlated with genetic distance, remaining below complete isolation for most of the species pairs. The results of this study, the first one on the time course of speciation in a fungus, are therefore consistent with previous works showing that RI generally evolves gradually with genetic distance, and thus presumably with time. Interestingly, prezygotic RI due to gamete recognition did not increase with genetic distance, in contrast to the pattern found in plants and animals. [source] RELATIVE ABUNDANCE AND THE SPECIES-SPECIFIC REINFORCEMENT OF MALE MATING PREFERENCE IN THE CHRYSOCHUS (COLEOPTERA: CHRYSOMELIDAE) HYBRID ZONEEVOLUTION, Issue 12 2005Merrill A. Peterson Abstract Most studies of reinforcement have focused on the evolution of either female choice or male mating cues, following the long-held view in sexual selection theory that mating mastakes are typically more costly for females than for males. However, factors such as conspecific sperm precedence can buffer females against the cost of mating mistakes, suggesting that in some hybrid zones mating mistakes may be more costly for males than for females. Thus, the historical bias in reinforcement research may underestimate its frequency. In this study, we present evidence that reinforcement has driven the evolution of male choice in a hybrid zone between teh highly promiscuous lealf beetles chyrsochus cobaltinus and C. auratus, the hybrids of which have extremely low fitness. In addition, there is evidence for male choice in these beetles and that male mating mistakes may be costly, due to reduced opportunities to mate with conspecific females. The present study combines laboratory and field methods to quantify the strenght of sexual isolation, test the hypothesis of reproductive character displacement, and assess the link between relative abundance and the strenght of selection against hybridization. We document that, while sexual isolation is weak, it is sufficient to produce positive assortative mating. In addtion, reproductive character displacement was only detected in the relatively rare species. The strong postzygotic barriers in this system are sufficient to generate the bimodality that characterizes this hybrid zone, but the weak sexual isolation is not, calling into question whether strong prezygotic isolation is necessary for the maintenance of bimodality. Growing evidence that the cost of mating mistakes is sufficient to shape the evolution of male mate choice suggests that the reinforecement of male mate choice may prove to be a widespread occurrence. [source] SEXUAL DIMORPHISM AND ADAPTIVE SPECIATION: TWO SIDES OF THE SAME ECOLOGICAL COINEVOLUTION, Issue 11 2003Daniel I. Bolnick Abstract Models of adaptive speciation are typically concerned with demonstrating that it is possible for ecologically driven disruptive selection to lead to the evolution of assortative mating and hence speciation. However, disruptive selection could also lead to other forms of evolutionary diversification, including ecological sexual dimorphisms. Using a model of frequency-dependent intraspecific competition, we show analytically that adaptive speciation and dimorphism require identical ecological conditions. Numerical simulations of individual-based models show that a single ecological model can produce either evolutionary outcome, depending on the genetic independence of male and female traits and the potential strength of assortative mating. Speciation is inhibited when the genetic basis of male and female ecological traits allows the sexes to diverge substantially. This is because sexual dimorphism, which can evolve quickly, can eliminate the frequency-dependent disruptive selection that would have provided the impetus for speciation. Conversely, populations with strong assortative mating based on ecological traits are less likely to evolve a sexual dimorphism because females cannot simultaneously prefer males more similar to themselves while still allowing the males to diverge. This conflict between speciation and dimorphism can be circumvented in two ways. First, we find a novel form of speciation via negative assortative mating, leading to two dimorphic daughter species. Second, if assortative mating is based on a neutral marker trait, trophic dimorphism and speciation by positive assortative mating can occur simultaneously. We conclude that while adaptive speciation and ecological sexual dimorphism may occur simultaneously, allowing for sexual dimorphism restricts the likelihood of adaptive speciation. Thus, it is important to recognize that disruptive selection due to frequency-dependent interactions can lead to more than one form of adaptive splitting. [source] Lower reproductive success in hybrid fur seal males indicates fitness costs to hybridizationMOLECULAR ECOLOGY, Issue 15 2007MELANIE L. LANCASTER Abstract Hybridization among organisms can potentially contribute to the processes of evolution, but this depends on the fitness of hybrids relative to parental species. A small, recently formed population of fur seals on subantarctic Macquarie Island contains a high proportion of hybrids (17,30%) derived from combinations of three parental species: Antarctic, subantarctic and New Zealand fur seals. Mitochondrial control-region data (restriction fragment length polymorphisms) and nine microsatellites were used to determine the species composition of breeding adults, and hybrid male fitness was measured by comparing reproductive success (number of genetically inferred paternities) of hybrid and pure-species territory males over 6 years. No correlations were found between male reproductive success and three genetic measures of outbreeding, but this may be due to a relatively small number of dominant males analysed. Territory males fathered 63% of pups, but hybrid males had lower reproductive success than pure-species males despite having the same ability to hold territories. A greater proportion of females in hybrid male territories conceived extra-territorially than those in territories of pure-species males, and most (70 of 82) mated with conspecifics. This suggests the presence of reproductive isolating mechanisms that promote positive assortative mating and reduce the production of hybrid offspring. Although we found no evidence for male sterility in the population, mechanisms that reduce lifetime reproductive success may act to decrease the frequency of hybrids. Our study has identified a disadvantage of hybridization , reduced reproductive success of hybrid sons , that may be contributing to the persistence of pure lineages at Macquarie Island and the temporal decline in hybridization observed there. [source] DNA analysis of transferred sperm reveals significant levels of gene flow between molecular forms of Anopheles gambiaeMOLECULAR ECOLOGY, Issue 7 2001F. Tripet Abstract Anopheles gambiae populations in west Africa are complex, being composed of multiple, sympatric subpopulations. Recent studies have failed to reveal significant genetic differences among subpopulations, stimulating a debate regarding the levels of gene flow among them. The observed homogeneity may be the consequence of substantial contemporary gene flow or it may be that reproductive isolation is complete, but too recent for the accumulation of significant levels of genic divergence. Here, we report the results of a study estimating contemporary levels of gene flow between An. gambiae subpopulations by analysing females and transferred sperm removed from their reproductive systems. A total of 251 female and associated sperm extracts was analysed from a single site in Mali. Two molecular forms of An. gambiae, the M- and S-forms, occurred in sympatry at this site. Overall, we found very strong positive assortative mating within forms, however, we did observe significant hybridization between forms. In the M subpopulation 2/195 females (1.03%) contained sperm from S-form males and in 55 S-form females we found one female containing M-form sperm (1.82%). We also identified a mated M ×S hybrid adult female. From mating frequencies, we estimate the Nem between the M- and S-form at 16.8, and from the adult hybrid frequency at 5.6. These values are consistent with our earlier estimate, based on FST for 21 microsatellite loci in which Nem = 5.8. We conclude that the general lack of genetic divergence between the M and S subpopulations of An. gambiae can be explained entirely by contemporary gene flow. [source] Ritualized combat as an indicator of intrasexual selection effects on male life history evolutionAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2010Brent M. Graves Trade-offs between survival, growth, current reproduction, and future reproduction influence life history evolution, leading to adaptive timing of investment in various strategies. If engagement in costly intrasexual contests to gain better access to mates is an important form of male reproductive investment, then the expression of characters that promote success in this process should be influenced by their fitness effects across the lifespan. To test this prediction, the ages at which human (Homo sapiens) males exhibit the greatest investment in morphological, behavioral, and physiological characters associated with intrasexual competition was estimated by examining the ages at which males succeed in a form of ritualized combat. The average age of international boxing champions was in the latter half of the twenties, and titles were held for about 2 years on average. Thus, peak investment in traits that enhance intrasexual competition abilities appears to coincide with ages at which males have highest reproductive success. Additionally, larger males reached peak probability of success in this ritualized combat at ages about 2.6 years greater than smaller males. Because body size is highly heritable and there is strong positive assortative mating relative to this character among humans, this may indicate a polymorphic set of reproductive strategies produced through maintenance of coadapted gene complexes. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source] | ||||||||||