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Mate Availability (mate + availability)
Selected AbstractsDOES MATE LIMITATION IN SELF-INCOMPATIBLE SPECIES PROMOTE THE EVOLUTION OF SELFING?EVOLUTION, Issue 6 2010THE CASE OF LEAVENWORTHIA ALABAMICA Genetic diversity at the S-locus controlling self-incompatibility (SI) is often high because of negative frequency-dependent selection. In species with highly patchy spatial distributions, genetic drift can overwhelm balancing selection and cause stochastic loss of S-alleles. Natural selection may favor the breakdown of SI in populations with few S-alleles because low S-allele diversity constrains the seed production of self-incompatible plants. We estimated S-allele diversity, effective population sizes, and migration rates in Leavenworthia alabamica, a self-incompatible mustard species restricted to discrete habitat patches in rocky glades. Patterns of polymorphism were investigated at the S-locus and 15 neutral microsatellites in three large and three small populations with 100-fold variation in glade size. Populations on larger glades maintained more S-alleles, but all populations were estimated to harbor at least 20 S-alleles, and mate availabilities typically exceeded 0.80, which is consistent with little mate limitation in nature. Estimates of the effective size (Ne) in each population ranged from 600 to 1600, and estimated rates of migration (m) ranged from 3 × 10,4 to nearly 1 × 10,3. According to theoretical models, there is limited opportunity for genetic drift to reduce S-allele diversity in populations with these attributes. Although pollinators or resources limit seed production in small glades, limited S-allele diversity does not appear to be a factor promoting the incipient breakdown of SI in populations of this species that were studied. [source] QUALITY OF AVAILABLE MATES, EDUCATION, AND HOUSEHOLD LABOR SUPPLYECONOMIC INQUIRY, Issue 3 2010BRIGHITA NEGRUSA We investigate the impact of sex ratios by education and metropolitan area on spouses' bargaining power and labor supplies, to capture the local and qualitative nature of mate availability. Using Current Population Survey and Census data for 2000, 1990, and 1980, we estimate these effects in a collective household framework. We find that a higher relative shortage of comparably educated women in the couple's metropolitan area reduces wives' labor supply and increases their husbands'. The impact is stronger for couples in higher education groups but not significant for high school graduates. Results are similar across decades. No such effects are found for unmarried individuals. (JEL D1, J22) [source] Environmental Predictors of Geographic Variation in Human Mating PreferencesETHOLOGY, Issue 4 2002Kevin J. McGraw Sexual selection theory classically posits consistent and directional mate-preferences for male traits that provide benefits to females. However, flexible mate-choice tactics may persist within a species when males display multiple desirable features that confer different benefits to females under variable environmental conditions. Ecological factors such as population density, resource demand, and sex ratio can influence the value that female animals place on certain male characteristics across mating environments. In this study, I used human mate-preference data from `lonely hearts' advertisements in the newspapers of 23 cities in the USA to assess geographic differences in female preferences for male traits (e.g. physical attributes, resource-holding potential, emotional characteristics, personal interests) in relation to these ecological parameters. I found that females placed more emphasis on the resource-accruing ability of prospective mates in densely populated cities and cities having greater resource demands (higher cost of living). In contrast, women from densely populated or resource-demanding cities placed less emphasis on the emotional aspects or personal interests of males. Preferences for physical features were not environmentally linked, but instead were a function of the degree to which females advertised their own physical attractiveness. Collectively, these results suggest that certain mate-choice criteria employed by women are sensitive to variation in local environmental conditions and that variable levels of resource or mate availability may favor different mating tactics across human populations. [source] THE POPULATION GENETICS OF SPOROPHYTIC SELF-INCOMPABILITY IN SENECIO SQUALIDUS L. (ASTERACEAE): THE NUMBER, FREQUENCY, AND DOMINANCE INTERACTIONS OF S ALLELES ACROSS ITS BRITISH RANGEEVOLUTION, Issue 2 2006Adrian C. Brennan Abstract Sporophytic self-incompatibility (SSI) was studied in 11 British Senecio squalidus populations to quantify mating system variation and determine how its recent colonization of the United Kingdom has influenced its mating behavior. S allele number, frequency, and dominance interactions in populations were assessed using full diallels of controlled pollinations. A mean of 5.1 S alleles per population was observed, and no population contained more than six S alleles. Numbers of S alleles within populations of S. squalidus declined with increasing distance from the center of its introduction (Oxford). Cross-classification of S alleles allowed an estimate of approximately seven and no more than 11 S alleles for the entire British S. squalidus population. The low number of S alleles observed in British S. squalidus compared to other SI species is consistent with the population bottleneck associated with S. squalidus introduction to the Oxford Botanic Garden and subsequent colonization of Britain. Extensive S allele dominance interactions were observed to be a feature of the S. squalidus SSI system and may represent an adaptive response to improve limited mate availability imposed by the presence of so few S alleles. Multilocus allozyme genotypes were also identified for individuals in all populations and geographic patterns of S locus and allozyme loci variation investigated. Less interpopulation structure was observed for the S locus than for allozyme diversity-a finding indicative of the effects of negative frequency-dependent selection at the S locus maintaining equal S phenotypes within populations and enhancing effective migration between populations [source] Skipped spawning in female iteroparous fishesFISH AND FISHERIES, Issue 1 2005Rick M Rideout Abstract It is often assumed that iteroparous fishes spawn annually once reaching sexual maturity, but this is not always the case. This paper reviews available information on skipped spawning in female teleost fishes. All instances of non-annual spawning are described as one of three types (retaining, reabsorbing, resting), depending on where in the normal spawning cycle development has been interrupted. Retaining ripe eggs is caused by conditions experienced during the spawning season (fish density, mate availability, pollution), whereas failure to start vitellogenesis (resting) or the breakdown of all oocytes that enter into vitellogenesis (reabsorbing) is caused by factors experienced prior to the spawning season (primarily temperature and poor nutrition). It is speculated that the relative shortage of data on non-annual spawning may be because of difficulties in identifying non-reproductive individuals. In an attempt to rectify this situation, the criteria needed to identify females undergoing the three forms of spawning omission are presented in terms of external appearance of gonads, gonad indices, and histological analysis. The energy saved by not spawning in a poor year may lead to increased survival and the probability of spawning in subsequent years. As the cumulative number of progeny gained by surviving to spawn in multiple subsequent years outweighs the number of progeny lost by not spawning in a given single year, occasional omission of spawning may constitute an adaptive trait in long-lived iteroparous fishes. [source] Are there interactive effects of mate availability and predation risk on life history and defence in a simultaneous hermaphrodite?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2008J. R. AULD Abstract Encountering mates and avoiding predators are ubiquitous challenges faced by many organisms and they can affect the expression of many traits including growth, timing of maturity and resource allocation to reproduction. However, these two factors are commonly considered in isolation rather than simultaneously. We examined whether predation risk and mate availability interact to affect morphology and life-history traits (including lifetime fecundity) of a hermaphroditic snail (Physa acuta). We found that mate availability reduced juvenile growth rate and final size. Predator cues from crayfish induced delayed reproduction, but there were no reduced fecundity costs associated with predator induction. Although there were interactive effects on longevity, lifetime fecundity was determined by the number of reproductive days. Therefore, our results indicate a resource-allocation trade-off among growth, longevity and reproduction. Future consideration of this interaction will be important for understanding how resource-allocation plasticity affects the integration of defensive, life-history and mating-system traits. [source] The evolution of repeated mating under sexual conflictJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2005R. Härdling Abstract In insects, repeated mating by females may have direct effects on female fecundity, fertility, and longevity. In addition, a female's remating rate affects her fitness through mortality costs of male harassment and ecological risks of mating such as predation. We analyse a model where these female fitness factors are put into their life-history context, and traded against each other, while accounting for limitations because of mate availability. We solve analytically for the condition when female multiple mating will evolve. We show that the probability that a female mates with a courting male decreases with increases in population density. The extent of conflict between the sexes thus automatically becomes larger at higher densities. However, because at higher densities females meet males at a higher rate, the resulting ESS female remating rate is independent of population density. The female remating probability is in conflict with male adaptations that increase male mating rate by persuading or forcing females to mate, and also in conflict with male adaptations for protecting the own sperm from being removed by future female mates. We show that the relative importance of these conflicts depends on population density. [source] Increase in mate availability without loss of self-incompatibility in the invasive species Senecio inaequidens (Asteraceae)OIKOS, Issue 2 2007Lucile Lafuma The evolution of the strength of self-incompatibility in Senecio inaequidens, a native of South Africa was investigated in relation to its invasion in Europe. Levels of self-incompatibility were estimated with hand-pollinations in five populations in greenhouse conditions. One population came from the native range of the species and four populations were sampled in Europe from two independent transects of colonization with old and recent populations. Contrary to Baker's law predictions, our results suggest that the species has a sporophytic self-incompatible system maintained in all populations. We suggest that the ability of S. inaequidens to colonize new sites with a self-incompatibility system is promoted by its ecological characteristics (perenniality, extended reproductive period, massive seed production, generalist pollinators). In addition, we found that mate availability was increased (1) in the introduced range compared to the native range, (2) in marginal versus central European populations. Possible explanations for this surprising result are discussed. [source] | ||||||||||