Orange Females Research Articles

CONDITION, GENOTYPE-BY-ENVIRONMENT INTERACTION, AND CORRELATIONAL SELECTION IN LIZARD LIFE-HISTORY MORPHS

We compared reproductive allocation and variation in condition and survivorship of two heritable female throat color morphs (orange and yellow) in a free-living population of side-blotched lizards (Uta stansburiana). Using path analysis and structural equation modeling, we investigated how variation in the social environment affected clutch size and egg mass and two condition traits (postlaying mass, immunological condition) and how these traits in turn affected female field survival. In the presence of many neighbors, both morphs increased their clutch sizes, although these effects were only significant in yellow females. In addition, yellow females increased their egg mass in the presence of many orange neighbors. Orange females surrounded by many orange neighbors showed sign of stress in the form of immunosuppression, whereas this effect was less pronounced in yellow females. The morphs also differed in the impact of variation in clutch size and egg mass on both condition traits. Finally, female morphotype and immune responsiveness affected fitness interactively, and hence these two traits showed signs of fitness epistasis: Selection gradients on this trait were opposite in sign in the two morphs. The correlational selection gradient (γthroat×antibody response) between female throat color and antibody responsiveness was −0.365. Our data thus reveal important interactive effects such as genotype-by-environment interaction toward the social environment and morph-specific trade-offs as well as the occurrence of correlational selection. We discuss the use of naturally occurring and conspicuous genetic polymorphisms in field studies of selection and life-history allocation.Corresponding Editor: T. Garland Jr.

Retroviruses and sexual size dimorphism in domestic cats (Felis catus L.).

Hochberg and co-workers have predicted that an increase in host adult mortality due to parasites is balanced by an earlier age at first reproduction. In polygynous species we hypothesize that such a pattern would lead to diverging selection pressure on body size between sexes and increased sexual size dimorphism. In polygynous mammals, male body size is considered to be an important factor for reproductive success. Thus, under the pressure of a virulent infection, males should be selected for rapid growth and/or higher body size to be able to compete successfully as soon as possible with opponents. In contrast, under the same selection pressure, females should be selected for lighter adult body size or rapid growth to reach sexual maturity earlier. We investigated this hypothesis in the domestic cat Felis catus. Orange cats have greater body size dimorphism than non-orange cats. Orange females are lighter than non-orange females, and orange males are heavier than non-orange males. Here, we report the extent to which orange and non-orange individuals differ in infection prevelance for two retroviruses, feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). FIV is thought to be transmitted almost exclusively through aggressive contacts between individuals, whereas FeLV transmission occurs mainly through social contacts. The pattern of infection of both diseases is consistent with the higher aggressiveness of orange cats. In both sexes, orange cats are significantly more infected by FIV, and tend to be less infected by FeLV than other cats. The pattern of infection is also consistent with an earlier age at first reproduction in orange than in non-orange cats, at least for females. These results suggest that microparasitism may have played an important role in the evolution of sexual size dimorphism of domestic cats.

Evidence of Selection on the Orange Allele in the Domestic Cat Felis catus: The Role of Social Structure

Various ecological conditions encountered by cats have important effects on their spatial and social organization. Our interest was focused on the relationships between genetic structure of populations, and their social structure and mating behaviour. A survey of allele frequencies at seven coat-colour loci in rural and urban populations of domestic cats in France confirmed the rural-urban cline for the Orange locus. The frequencies of the Orange allele were high in rural habitats, which were characterized by low densities (between 140 to 230 individuals per km 2 ), and a polygynous mating system. Low frequencies of the Orange allele were found in urban populations, which had high densities (1300 cats per km 2 ) and a promiscuous mating system. Orange males were heavier than non-Orange males, whereas Orange females were lighter than non-Orange females. Due to the importance of body weight in life-history traits variability, we hypothesize that reproductive tactics may differ between individuals according to Orange genotype. This may explain why the Orange allele does not reach frequencies as high as those of non-agouti and blotched tabby alleles, which are more recent coat colour mutations.

Disruptive sexual selection in Colias eurytheme butterflies.

Sexual selection on male pheromone composition in Colias eurytheme (Pieridae) butterflies has the remarkable effect of increasing the variability of this trait. Sexual selection on important traits is generally thought to have a strong stabilizing effect on intraspecific variation of those characters. In this species, however, the male courtship pheromone is highly variable in the relative proportions of its three chemical constituents. Stabilization and/or canalization of this polygenic character in a population is impeded by the disproportionate mating success of males in one portion of the character distribution with alba (white morph) females, and of those in the opposite portion with orange (colored morph) females.

Nitrogen metabolism in Colias croceus (Linné) and its “ Alba” mutant (Lepidoptera Pieridae)

[1- 14C]glycine and [2- 14C]guanosine were injected into pupae at various stages and into pharate adults of the polymorphic Pierid butterfly Colias croceus. Three phenotypes were studied: orange males, white (“ Alba”) females, and orange females. After hatching, the adults were submitted to an analysis which separated small excretory molecules, wing (pteridine) pigments, RNA and proteins. The overall metabolism of these compounds is quantitatively very different between males and both types of females. “ Alba” females incorporate more quanosine in RNA and glycine in proteins than “orange” females at the developmental time which corresponds to fat body synthesis. This phenomenon is related to a different resource allocation in both female morphs.

Adaptive and incidental consequences of the alba polymorphism in an agricultural population of Colias butterflies: female size, fecundity, and differential dispersion.

A sex-limited color dimorphism occurs in many populations of Colias eurytheme. Alba females exhibit different patterns of resource allocation and are less attractive than orange females. This study examines some of the consequences of these differences in terms of reproductive success and population structure in a high density agricultural population.Alba females produced more eggs than orange females on a daily basis, but the morphs did not differ in three measures of size. Spermatophore counts revealed that fresh and worn females did not differ in mating frequency between the two morphs, but very worn alba females gained more matings than very worn orange females.In two mark-release-recapture experiments, alba females exhibited longer residence times than orange females. Changes in population structure over time suggest that this was due to dispersal of orange females from the mature field. Evidence is presented that orange females emigrate in response to male harassment at high density while alba females, exposed to less harassment, remain behind. We suggest that the persistence of the polymorphism in this agricultural population is at least partially facilitated by the cyclic cutting of the alfalfa.

Stability of the Sex Alleles of Habrobracon

A single female heterozygous for orange eye-color and derived from a cross of unrelated parents was bred to one of its own orange sons. Descendants were inbred by sibling matings in different lines for ten generations with orange and wild type black eye-color retained in each line. Orange and black stocks were then derived and the orange females were crossed in various combinations with the black males. Total progeny counted were 56,913 females, 7,471 diploid males and 41,899 haploid males. Only two members of the single series of multiple sex alleles are to be expected because the entire population was derived from a single female. The data suggest an influence of maternal genotype exceeding that of paternal on viability of diploid males and also an increase in their viability due to heterosis. Diploid male viability as compared with that of females showed no association with sex ratio or with average numbers of haploid males or of females per fraternity. There were, however, eleven so-called mutant fr...