Variation and heritability of aristal morphology in a natural population of Drosophila mediopunctata

We studied the major sources influencing the variation of the number of aristal branches in a natural population of Drosophila mediopunctata. Flies were collected on six occasions at different altitudes in Parque Nacional do Itatiaia (Brazil). The progenies of these flies were reared in the laboratory at 16.5 degrees C. The number of aristal branches ranges from 11 to 15 and is influenced by sex. Estimates of the natural heritability showed that at least 20% of the total phenotypic variation is due to additive genetic variation. Although the heritability of this trait estimate in the laboratory was larger (42%), the difference between the two estimates is not statistically significant. Thus, for the number of aristal branches, laboratory estimates of heritability provide reasonable estimations of both the magnitude and significance of heritabilities in nature. The mean numbers of aristal branches in the wild-caught flies from different altitudes or months are homogeneous. The same was observed for the means of its progeny kept in the laboratory under controlled conditions. On the other hand, wild-caught females have significantly fewer aristal branches than their laboratory-raised daughters, which suggests that an environmental factor or factors may have an important influence on this trait.1281677

YEAST SUCCESSION IN THE AMAZON FRUIT PARAHANCORNIA-AMAPA AS RESOURCE PARTITIONING AMONG DROSOPHILA SPP

The succession of yeasts colonizing the fallen ripe amapa fruit, from Parahancornia. amapa, aas examined. The occupation of the substrate depended on both the competitive interactions of yeast species, such as the production of killer toxins, and the selective dispersion by the drosophilid guild of the amapa fruit. The yeast community associated with this Amazon fruit differed from those isolated from other fruits in the same forest. The physiological profile of these yeasts was mostly restricted to the assimilation of a few simple carbon sources, mainly L-sorbose, D-glycerol, DL-lactate, cellobiose, and salicin. Common fruit-associated yeasts of the genera Kloeckera and Hanseniaspora, Candida guilliermondii, and Candida krusei colonized fruits during the first three days after the fruit fell. These yeasts were dispersed and served as food for the invader Drosophila malerkotliana. The resident flies of the Drosophila willistoni group fed selectively on patches of yeasts colonizing fruits 3 to 10 days after the fruit fell. The killer toxin-producing yeasts Pichia kluyveri var. kluyveri and Candida fructus were probably involved in the exclusion of some species during the intermediate stages of fruit deterioration. An increase in pH, inhibiting toxin activity and the depletion of simple sugars, may have promoted an increase in yeast diversity in the later stages of decomposition. The yeast succession provided a patchy environment for the drosophilids sharing this ephemeral substrate.61124251425

AUTOSOMAL SUPPRESSORS OF SEX-RATIO IN DROSOPHILA-MEDIOPUNCTATA

The sex-ratio trait has been described as the production of progenies with excess of females due to X-linked meiotic drive in the parental males. This trait has a variable expression in Drosophila mediopunctata. We describe here the existence and chromosomal localization of autosomal suppressors of sex-ratio in this species. There are at least four such genes (one on each major autosome) and the strongest effect.is localized on chromosome IV. These genes possibly result from the operation of 'Fisher's Principle'; a mechanism of Natural Selection leading to a 1:1 sex ratio.71554655

Shape and size variation on the wing of Drosophila mediopunctata: influence of chromosome inversions and genotype-environment interaction

The second chromosome of Drosophila mediopunctata is highly polymorphic for inversions. Previous work reported a significant interaction between these inversions and collecting date on wing size, suggesting the presence of genotype-environment interaction. We performed experiments in the laboratory to test for the joint effects of temperature and chromosome inversions on size and shape of the wing in D. mediopunctata. Size was measured as the centroid size, and shape was analyzed using the generalized least squares Procrustes superimposition followed by discriminant analysis and canonical variates analysis of partial warps and uniform components scores. Our findings show that wing size and shape are influenced by temperature, sex, and karyotype. We also found evidence suggestive of an interaction between the effects of karyotype and temperature on wing shape, indicating the existence of genotype-environment interaction for this trait in D. mediopunctata. In addition, the association between wing size and chromosome inversions is in agreement with previous results indicating that these inversions might be accumulating alleles adapted to different temperatures. However, no significant interaction between temperature and karyotype for size was found - in spite of the significant presence of temperature - genotype (cross) interaction. We suggest that other ecological factors - such as larval crowding - or seasonal variation of genetic content within inversions may explain the previous results.133333534

Y-LINKED SUPPRESSORS OF THE SEX-RATIO TRAIT IN DROSOPHILA-MEDIOPUNCTATA

X-linked meiotic drive causing female-biased progenies is known to occur in nine Drosophila species and is called 'sex-ratio'. In D. mediopunctata this trait is associated with the X:21 chromosome inversion and has variable expression. We describe here a powerful Y-linked suppressor system of sex-ratio expression in this species. There are two types of Y chromosomes (suppressor and nonsuppressor) and two types of X:21 chromosomes (suppressible and unsuppressible). Sex-ratio expression is suppressed in males with the 21 (suppressible)/Y-suppressor genotype, whereas the remaining three genotypes produce female-biased progenies.73657357

Heritability, phenotypic and genetic correlations of size and shape of Drosophila mediopunctata wings

We have studied the morphology of wings of Drosophila mediopunctata employing the ellipse method, a procedure that allows precise descriptions of wing size (SI), wing share outline (SM), and placement of longitudinal wing veins. We have found that the SH and the points which determine the position of the apices of the third, fourth and fifth longitudinal wing veins show high heritability in nature (the lower bound for the natural heritability is above 0.25). The values found are similar to those obtained for the broad-sense heritabilities (H(2)) in the laboratory. However, SI and the point which determines the apex of the second longitudinal wing vein showed small lower bounds for heritability in nature, 0.05 and 0.07, respectively, in spite of the high estimates of H(2) in the laboratory. These results suggest that size and shape have different genetic properties. We observed a high positive phenotypic correlation between the SH, the fourth and the fifth longitudinal wing veins, which contrasts with a negative correlation between these traits and the second longitudinal vein. That is, as the SH gets longer, the apices of the second and fifth veins become closer to each other. Positive genetic correlations in the field were detected between SH, the fourth and the fifth longitudinal veins and also between the third and the fourth veins.8368869

Plasticity of Drosophila melanogaster wing morphology: effects of sex, temperature and density

In this paper we use an adjusted ellipse to the contour of the wings of Drosophila as an experimental model to study phenotypic plasticity. The geometric properties of the ellipse describe the wing morphology. Size is the geometric mean of its two radii; shape is the ratio between them; and, the positions of the apexes of the longitudinal veins are determined by their angular distances to the major axis of the ellipse. Flies of an inbred laboratory strain of Drosophila melanogaster raised at two temperatures (16.5 degrees C and 25 degrees C) and two densities (10 and 100 larvae per vial) were used. One wing of at least 40 animals of each sex and environmental condition were analyzed (total = 380), a measurement of thorax length was also taken. Wing size variation could be approximately divided into two components: one related to shape variation and the other shape independent. The latter was influenced primarily by temperature, while the former was related to sex and density. A general pattern could be identified for the shape dependent variation: when wings become larger they become longer and the second, fourth and fifth longitudinal veins get closer to the tip of the wing.105220321

Size and shape heritability in natural populations of Drosophila mediopunctata: temporal and microgeographical variation

'Traditional morphometrics' allows us to decompose morphological variation into its major independent sources, identifying them usually as size and shape. To compare and investigate the properties of size and shape in natural populations of Drosophila mediopunctata, estimating their heritabilities and analysing their temporal and microgeographic changes, we carried out collections on seven occasions in Parque Nacional do Itatiaia, Brazil. In one of these collections, we took samples from five different altitudes. Measurements were taken from wild caught inseminated females and up to three of their laboratory-reared daughters. Through a principal component analysis, three major sources of variation were identified as due to size (the first one) and shape (the remaining two). The overall amount of variation among laboratory flies was about half of that observed among wild flies and this reduction was primarily due to size. Shape variation was about the same under natural and artificial conditions. A genetic altitudinal cline was detected for size and shape, although altitude explained only a small part of their variation. Differences among collections were detected both for size and shape in wild and laboratory flies, but no simple pattern emerged. Shape variation had high heritability in nature, close to or above 40% and did not vary significantly temporally. Although on the overall size heritability (18 +/- 6%)was significant its estimates were not consistent along months - they were non-significant in all but one month, when it reached a value of 51 +/- 11%. Overall, this suggests that size and shape have different genetic properties.1051354

Polymorphism for Y-linked suppressors of sex-ratio in two natural populations of Drosophila mediopunctata

In several Drosophila species there is a trait known as ''sex-ratio'': males carrying certain X chromosomes (called ''SR'') produce female biased progenies due to X-Y meiotic drive. In Drosophila mediopunctata this trait has a variable expression due to Y-linked suppressors of sex-ratio expression, among other factors. There are two types of Y chromosomes (suppressor and nonsuppressor) and two types of SR chromosomes (suppressible and unsuppressible). Sex-ratio expression is suppressed in males with the SRsuppressible/Y-suppressor genotype, whereas the remaining three genotypes produce female biased progenies. Now we have found that similar to 10-20% of the Y chromosomes from two natural populations 1500 km apart are suppressors of sex-ratio expression. Preliminary estimates indicate that Y-suppressor has a meiotic drive advantage of 6% over Y-nonsuppressor. This Y polymorphism for a nonneutral trait is unexpected under current population genetics theory. We propose that this polymorphism is stabilized by an equilibrium between meiotic drive and natural selection, resulting from interactions in the population dynamics of X and Y alleles. Numerical simulations showed that this mechanism may stabilize nonneutral Y polymorphisms such as we have found in D. mediopunctata.146389190