			Home About us Contact

Fecundity Selection (fecundity + selection)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Fecundity selection predicts Bergmann's rule in syngnathid fishes

MOLECULAR ECOLOGY, Issue 6 2009
ANTHONY B. WILSON
Abstract The study of latitudinal increases in organismal body size (Bergmann's rule) predates even Darwin's evolutionary theory. While research has long concentrated on identifying general evolutionary explanations for this phenomenon, recent work suggests that different factors operating on local evolutionary timescales may be the cause of this widespread trend. Bergmann's rule explains body size variation in a diversity of warm-blooded organisms and there is increasing evidence that Bergmann's rule is also widespread in ectotherms. Bergmann's rule acts differentially in species of the Syngnathidae, a family of teleost fishes noted for extreme adaptations for male parental care. While variation in body size of polygamous Syngnathus pipefish is consistent with Bergmann's rule, body size is uncorrelated with latitude in monogamous Hippocampus seahorses. A study of populations of Syngnathus leptorhynchus along a natural latitudinal and thermal gradient indicates that increases in body size with latitude maintain the potential reproductive rate of males despite significant decreases in ambient temperatures. Polygyny is necessary in order to maximize male reproductive success in S. leptorhynchus, suggesting a possible a link between fecundity selection and Bergmann's rule in this species. [source]

Genetic and demographic responses of mercury-exposed mosquitofish (Gambusia holbrooki) populations: Temporal stability and reproductive components of fitness

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2002
Christopher Paul Tatara
Abstract Two previous mesocosm studies showed changes in glucosephosphate isomerase-2 (Gpi-2) allele frequencies in mosquitofish populations exposed to mercury for 111 d or two years. A previous selection component analysis of single-generation populations exposed for 111 d to 18 ,/L Hg suggested that female sexual selection and fecundity selection could contribute to changes in Gpi-2 allele frequencies. The present multigeneration study was conducted to determine the stability of Gpi-2 allele frequencies over four years of mercury exposure, measure the reproductive fitness of Gpi-2 genotypes inhabiting control and mercury-contaminated mesocosms to determine a mechanism explaining changes in Gpi-2 allele frequencies, investigate differences in the demographic characteristics of mercury-exposed and control populations, and investigate the water quality of the mesocosms to determine if variables other than mercury show concordant patterns among mesocosms. Differences in Gpi-2 allele frequencies between control and mercury-exposed populations were stable over four years (, eight generations) of mercury exposure. Mercury-exposed female mosquitofish had a lower probability of being gravid than control females (p = 0.001). Mercury-exposed females also had lower fecundity (total number of eggs and embryos) than control females (p = 0.036). Unlike the results of the more intense mercury exposures in the single generation study, no strong evidence was found that Gpi-2 genotype influenced fecundity or the probability of being gravid in both control and mercury-exposed females. The quantification of fitness components is difficult but has the potential to enhance our understanding of how toxicants alter allele frequencies in exposed populations. [source]

NUPTIAL GIFTS AND THE EVOLUTION OF MALE BODY SIZE

EVOLUTION, Issue 3 2002
Kenneth M. Fedorka
Abstract In many insect systems, males donate nuptial gifts to insure an effective copulation or as a form of paternal investment. However, if gift magnitude is both body size-limited and positively related to fitness, then the opportunity exists for the gift to promote the evolution of large male size. In the striped ground cricket, Allonemobius socius, males transfer a body size-limited, somatic nuptial gift that is comprised primarily of hemolymph. To address the implications of this gift on male size evolution, we quantified the intensity and direction of natural (fecundity) and sexual (mating success) selection over multiple generations. We found that male size was under strong positive sexual selection throughout the breeding season. This pattern of selection was similar in successive generations spanning multiple years. Male size was also under strong natural selection, with the largest males siring the most offspring. However, multivariate selection gradients indicated that gift size, and not male size, was the best predictor of female fecundity. In other words, direct fecundity selection for larger gifts placed indirect positive selection on male body size, supporting the hypothesis that nuptial gifts can influence the evolution of male body size in this system. Although female size was also under strong selection due to a size related fecundity advantage, it did not exceed selection on male size. The implications of these results with regard to the maintenance of the female-biased size dimorphic system are discussed. [source]

Fecundity selection predicts Bergmann's rule in syngnathid fishes

A test of Rensch's rule in varanid lizards

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010
PETRA FRÝDLOVÁ
In a model group of giant reptiles, we explored the allometric relationships between male and female body size and compared the effects of sexual and fecundity selection, as well as some proximate causes, on macroevolutionary patterns of sexual size dimorphism (SSD). Monitor lizards are a morphologically homogeneous group that has been affected by extreme changes in body size during their evolutionary history, resulting in 14-fold differences among the body sizes of recent species. Here, we analysed data concerning the maximum and/or mean male and female snout,vent lengths in 42 species of monitor lizard from literary sources and supplemented these data with measurements made in zoos. There was a wide scale of SSD from nearly monomorphic species belonging mostly to the subgenus Odatria and Prasinus group of the Euprepriosaurus to apparently male-larger taxa. The variable best explaining SSD was the body size itself; the larger the species, the higher the SSD. This pattern agrees with the currently discussed Rensch's rule, claiming that the relationship between male and female body size is hyperallometric, i.e. the allometric exponent of this relationship exceeds unity and thus SSD increases with body size in the case of male-larger taxa. All our estimates of the reduced major axis regression slopes of this relationship ranged from 1.132 to 1.155. These estimates are significantly higher than unity, and thus unequivocally corroborate the validity of Rensch's rule in this reptilian group. In spite of our expectation that the variation in SSD can be alternatively explained by variables reflecting the strength of sexual selection (presence of male combat), fecundity selection (e.g. clutch size and mass) and/or proximate ecological factors (habitat type), none of these variables had consistent effects on SSD, especially when the data were adjusted to phylogenetic dependence and/or body size. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 293,306. [source]