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While the phenotypic effects of sexual selection have been well studied, the consequences for population mean fitness remain unclear. Additionally, there is a need to more fully characterize how various forms of inter- and intrasexual selection combine to affect the evolution of traits under sexual selection. Here, I address these issues as they relate to male territoriality in Drosophila serrata, a model system for the study of female preference for male pheromones. First, I demonstrate that territoriality occurs and is a likely component of male sexual fitness. Results from a phenotypic manipulation indicate that territorial success was also condition-dependent, and that sexual selection against low condition males tended to be stronger given a high opportunity for territory defense. Territorial success depended on body size but not on pheromones. How this and other components of male mating success interact to affect trait evolution and population mean fitness remains an important area for future study.

Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.

The ultimate goal of my thesis is to develop a better understanding of the contribution of indirect benefits (i.e. good genes) to the evolution of female mate preferences. It is genetic variance in, and genetic correlations (covariances) among, male sexual displays, female preferences for them, and fitness that in part determine the degree to which females preferring certain male displays over others will gain an indirect benefit by having higher fitness offspring. Recent advances in quantitative genetic theory provide the mathematical means for quantifying the strength of indirect selection for female mate preferences (Kirkpatrick and Hall 2004), at least under certain conditions, but there are few empirical systems for which such data exist (Brooks and Endler 2001; Qvarnström et al. 2006). I have undertaken a classic half-sibling breeding design with the ultimate goal of estimating the specific parameters of this model in a population of the Australian fruit fly Drosophila serrata. The breeding design was performed across two environments - one to which the population was well adapted and a novel environment to which it was not - thereby also providing insight into genotype-by-environment interactions for this suite of traits and their effects on good genes indirect benefits in a novel environment. General insight is also gained into the genetic covariance of male and female fitness and the prevalence of intralocus sexual conflict, the quantitative genetic basis of female mate preferences for multiple male traits, the condition-dependence of these traits, and the genetic association between sexual displays and fitness when mutation-selection balance is inferred. My results advocate caution in the application of existing theory to quantify the strength of indirect selection, suggesting that a good genes process may be fundamentally different when the exaggeration of sexual displays is eventually halted and an equilibrium is reached between opposing selection.

Drosophila (Sophophora) serrata Malloch Drosophila serrata Malloch, 1927. Proc. Linnean Soc. N.S.W. 52, p. 6. Type locality: Eidsvold, Queensland, Australia. Apart from the semi-cosmopolitan species Drosophila kikkawai, D. serrata is, within the Australasian Region, the most widespread species of the montium subgroup. We have examined specimens from widely separated localities of the known D. serrata range and found limited morphological variation and no incorrect earlier determinations. We now have a better understanding of the preferred D. serrata habitat and note that certain earlier reports of ��� D. serrata ��� for which there are no reference specimens, are difficult to reconcile within this new view of preferred environmental conditions; we believe that earlier reports of D. serrata from deep within rainforests are more likely to be misidentifications of D. birchii or of the new species we describe below. The southern limit of the range of D. serrata is at Wollongong (34.3��S, Jenkins & Hoffmann 1999), intensive fruit trapping at Nowra, 50 km farther south failed to yield any montium subgroup species (Jenkins & Hoffmann 2001). The most northern record for D. serrata is at Rabaul, New Britain (4.4��N, Ayala 1965 a). This distribution has a latitudinal magnitude of over 38 ��. The longitudinal breadth is also wide at 54 ��, with reports from Christmas Island in the Indian Ocean near Java (Carson & Wheeler 1973 and McEvey 2004) through the Kimberly region, Western Australia, and Berry Springs, Northern Territory to Lord Howe Island, 500 km off the east coast of Australia. Distribution (Fig. 20): Northern and eastern Australia (including Christmas, Norfolk and Lord Howe Islands) and Papua New Guinea (Atkinson 1985; Ayala 1965 a; Baimai 1970 a; Birch et al. 1963; Bock 1976; Bock 1977; Dobzhansky & Mather 1961; Jenkins & Hoffmann 1999; Jenkins & Hoffmann 2001; Mather 1955; Mather 1956; McEvey 1993; van Klinken 1996; also see Appendix)., Published as part of Schiffer, Michele & Mcevey, Shane F., 2006, Drosophila bunnanda ��� a new species from northern Australia with notes on other Australian members of the montium subgroup (Diptera: Drosophilidae), pp. 1-23 in Zootaxa 1333 on pages 6-7, DOI: 10.5281/zenodo.174253, {"references":["Malloch, J. R. (1927) Notes on Australian Diptera No. x. Proceedings of the Linnean Society of New South Wales, 52, 1 - 16.","Jenkins, N. L. & Hoffmann, A. A. (1999) Limits to the southern border of Drosophila serrata: Cold resistance, heritable variation and trade-offs. Evolution, 53, 1823 - 1834.","Jenkins, N. L. & Hoffmann, A. A. (2001) Distribution of Drosophila serrata Malloch (Diptera: Drosophilidae) in Australia with particular reference to the southern border. Australian Journal of Entomology, 40, 41 - 48.","Ayala, F. J. (1965 a) Sibling species of the Drosophila serrata group. Evolution, 19, 538 - 545.","Carson, H. L. & Wheeler, M. R. (1973) A new crab fly from Christmas Island, Indian Ocean (Diptera: Drosophilidae). Pacific Insects, 15, 199 - 208.","McEvey, S. F. (2004) The Drosophilid flies of Christmas Island: Australian Museum survey 2003. Unpublished report for Parks Australia North, Christmas Island.","Atkinson, W. D. (1985) Coexistence of Australian rainforest diptera breeding in fallen fruit. Journal of Animal Ecology, 54, 507 - 518.","Baimai, V. (1970 a) Additional evidence on sexual isolation within Drosophila birchii. Evolution, 24, 149 - 155.","Birch, L. C. Dobzhansky, T. Elliott, P. O. & Lewontin, R. C. (1963) Relative fitness of geographic races of Drosophila serrata. Evolution, 17, 72 - 83.","Bock, I. R. (1976) Drosophilidae of Australia I. Drosophila (Insecta: Diptera). Australian Journal of Zoology, Supplementary series, 40, 1 - 105.","Dobzhansky, T. & Mather, W. B. (1961) The evolutionary status of Drosophila serrata. Evolution, 15, 461 - 467.","Mather, W. B. (1955) The genus Drosophila (Diptera) in eastern Queensland I. Taxonomy. Australian Journal of Zoology, 3, 545 - 582.","Mather, W. B. (1956) The genus Drosophila (Diptera) in eastern Queensland II. Seasonal changes in a natural population 1952 - 1953, Australian Journal of Zoology, 4, 65 - 75.","McEvey, S. F. (1993) Drosophilidae (Diptera) of northern Cape York Peninsula. In: Anon (Ed.) Cape York Peninsula Scientific Expedition, Wet Season 1992, The Royal Geographic Society of Queensland Inc, Fortitude Valley, Brisbane pp. 155 - 168.","van Klinken, R. D. (1996) Understanding diversity in ecological communities: A study of Australian Drosophilidae, with emphasis on the coracina group of Scaptodrosophila species. PhD thesis. Department of Entomology. The University of Queensland, Brisbane, Australia."]}

Drosophila serrata complex Drosophila serrata complex���first reference Bock & Wheeler, Univ. Texas Publ. 7213, p. 49 Bock & Wheeler (1972) note that ���the most extensively studied complex in the montium subgroup from the point of view of speciation and incipient speciation is that consisting of the three species D. serrata, D. birchii and D. dominicana ���. We can find no earlier mention of the ��� serrata complex��� in the literature, although Ayala refers to the ��� serrata group��� in the title of his 1965 papers (1965 a, b), nor is there a formal description of the morphological characteristics of such a complex. It should be noted that the term ���species complex��� is not a formal taxonomic category. After D. serrata was described by Malloch (1927) from Eidsvold, Queensland (not ���Esdivold��� as is written on the label of the type specimen, and not ���Eidsvolt��� sensu Bock & Wheeler 1972), Dobzhansky & Mather (1961) detected a very similar form from Papua New Guinea and northern Australia and designated it as a D. serrata subspecies: D. serrata birchii. Ayala (1965 a), tested sexual isolation between these two forms and a third (very closely resembling D. birchii), known only from Madang on the north coast of Papua New Guinea. His findings resulted in the reclassification of D. serrata birchii as D. birchii, and nomination of the Madang fly as D. dominicana (Ayala 1965 b). Following on from the work of Ayala (1965 a), Baimai (1970 a) studied incipient speciation within D. birchii, and confirmed Ayala���s earlier conclusion that the populations of this species from Rabaul (New Britain), from mainland Papua New Guinea, and from northern Australia comprise a series of populations partially reproductively isolated from one another. Baimai (1970 b) also found that several of the at least 40 polytene chromosome inversions in D. birchii are unique to specific geographic areas. Investigations of ND 5 microsatellite variation in Australian populations of D. birchii have revealed no significant geographic structure and low nucleotide diversity (Kelemen & Moritz 1999)., Published as part of Schiffer, Michele & Mcevey, Shane F., 2006, Drosophila bunnanda ��� a new species from northern Australia with notes on other Australian members of the montium subgroup (Diptera: Drosophilidae), pp. 1-23 in Zootaxa 1333 on pages 5-6, DOI: 10.5281/zenodo.174253, {"references":["Bock, I. R. & Wheeler, M. R. (1972) The Drosophila melanogaster species group. In: Wheeler, M. R. (Ed.), Studies in Genetics VII. The University of Texas Publication No 7213, Texas, pp. 1 - 102.","Malloch, J. R. (1927) Notes on Australian Diptera No. x. Proceedings of the Linnean Society of New South Wales, 52, 1 - 16.","Dobzhansky, T. & Mather, W. B. (1961) The evolutionary status of Drosophila serrata. Evolution, 15, 461 - 467.","Ayala, F. J. (1965 a) Sibling species of the Drosophila serrata group. Evolution, 19, 538 - 545.","Ayala, F. J. (1965 b) Drosophila dominicana, a new sibling species of the serrata group. Pacific Insects, 7, 620 - 622.","Baimai, V. (1970 a) Additional evidence on sexual isolation within Drosophila birchii. Evolution, 24, 149 - 155.","Baimai, V. (1970 b) Chromosomal polymorphism in Drosophila birchii. Journal of Heredity, 61, 22 - 34.","Kelemen, L. & Moritz, C. (1999) Comparative phylogeography of a sibling pair of rainforest Drosophila species (Drosophila serrata and D. birchii). Evolution, 53, 1306 - 1311."]}

SUMMARY Fluorescence spectrophotometry can reliably detect levels of the pteridine 6-biopterin in the heads of individual Drosophila serrata Malloch 1927. Pteridine content in both laboratory and field captured flies is typically a level of magnitude higher than the minimally detectable level(meanlab=0.54 units, meanfield=0.44 units, minimum detectable level=0.01 units) and can be used to predict individual age in laboratory populations with high certainty (r2=57%). Laboratory studies of individuals of known age (from 1 to 48 days old)indicate that while pteridine level increases linearly with age, they also increase in a linear manner with rearing temperature and ambient light levels,but are independent of sex. As expected, the longevity of laboratory-reared males (at least 48 days) is higher than the range of predicted ages of wild-caught males based on individual pteridine levels (40 days). However, the predictive equation based on pteridine level alone suggested that a number of wild-caught males were less than 0 days old, and the 95% confidence limits for these predictions based on the inverse regression are broad. The age of the oldest wild-caught male is predicted to fall within the range of 2 to 50 days. The significant effects of temperature and light intensity determined in the laboratory study (effect sizes ω2=14.3 and 20.4%,respectively) suggests that the calibration of the age prediction equation for field populations would be significantly improved when combined with fine-scaled studies of habitat temperature and light conditions. The ability to determine relative age in individual wild-caught D. serratapresents great opportunities for a variety of evolutionary studies on the dynamics of natural populations.

We examined the genetic basis of clinal adaptation by determining the evolutionary response of life-history traits to laboratory natural selection along a gradient of thermal stress in Drosophila serrata. A gradient of heat stress was created by exposing larvae to a heat stress of 36° for 4 hr for 0, 1, 2, 3, 4, or 5 days of larval development, with the remainder of development taking place at 25°. Replicated lines were exposed to each level of this stress every second generation for 30 generations. At the end of selection, we conducted a complete reciprocal transfer experiment where all populations were raised in all environments, to estimate the realized additive genetic covariance matrix among clinal environments in three life-history traits. Visualization of the genetic covariance functions of the life-history traits revealed that the genetic correlation between environments generally declined as environments became more different and even became negative between the most different environments in some cases. One exception to this general pattern was a life-history trait representing the classic trade-off between development time and body size, which responded to selection in a similar genetic fashion across all environments. Adaptation to clinal environments may involve a number of distinct genetic effects along the length of the cline, the complexity of which may not be fully revealed by focusing primarily on populations at the ends of the cline.

To investigate the ability of Drosophila serrata to adapt to thermal conditions over winter at the species southern border, replicate lines from three source locations were held as discrete generations over three years at either 19 degrees C (40 generations) or temperatures fluctuating between 7 degrees C and 18 degrees C (20 generations). Populations in the fluctuating environment were maintained either with an adult 0 degrees C cold shock or without a shock. These conditions were expected to result in temperature-specific directional selection for increased viability and productivity under both temperature regimes, and reduced development time under the fluctuating-temperature regime. Selection responses of all lines were tested under both temperature regimes after controlling for carry-over effects by rearing lines in these environments for two generations. When tested in the 19 degrees C environment, lines evolving at 19 degrees C showed a faster development time and a lower productivity relative to the other lines, while cold shock reduced development time and productivity of all lines. When tested in the fluctuating environment, productivity of the 7-18 degrees C lines selected with a cold shock was relatively lower than that of lines selected without a shock, but this pattern was not observed in the other populations. Viability and body size as measured by wing length were not altered by selection or cold shock, although there were consistent effects of source population on wing length. These results provide little evidence for temperature-specific adaptation in D. serrata-although the lines had diverged for some traits, these changes were not consistent with a priori predictions. In particular, there was no evidence for life-history changes reflecting adaptation to winter conditions at the southern border. The potential for D. serrata to adapt to winter conditions may therefore be limited.

The influence of maternal and grandmaternal age on progeny egg–to–adult viability was assessed in Drosophila serrata . Viability in progeny decreased with increasing maternal age. The potential for cumulative age effects was investigated in two environments, one of which involved nutrient and cold stress. Environment influenced viability and female age influenced progeny egg–to–adult viability across one generation. The influence on viability was cumulative across two generations. Females from old mothers, who also had old grandmothers, had the lowest viability in both environments. Grandmaternal effects were associated with a decrease in egg hatch rate whereas maternal effects also involved larval–to–adult viability. The age of the mother and grandmother should be taken into account when evaluating life–history traits in Drosophila .

A simple and rapid method for isolation of high quality mitochondrial DNA (mtDNA) is presented in this report. Using this method, isolation and restriction site maps for 10 enzymes of the mtDNA of Drosophila serrata were established.

Drosophila serrata and D. birchii are presumed sibling species; the former is a widespread generalist and the latter is restricted to rainforests. Comparison of the mtDNA sequence phylogeographies revealed two highly divergent, geographically distinct lineages of D. serrata that are as distinct from each other as either is from D. birchii. However, diversity in D. birchii is low and unstructured. The low diversity in D. birchii corresponds with a late-Pleistocene-Holocene contraction of lowland rainforests. We suggest that future studies of speciation and adaptation should compare the two lineages of D. serrata to each other as well as to D. birchii.

Many species harbor the incompatibility-inducing microbe Wolbachia, a maternally inherited endoparasite that causes reduced egg hatch in crosses between infected males and uninfected females. Infected females are immune to this effect, which gives them a relative fitness advantage that results in the spread of the infection. The strength of incompatibility, fitness deficits associated with the infection, and transmission rate from mother to offspring largely determine the rate and extent of spread of Wolbachia in a population. We transferred Wolbachia from Drosophila simulans to Drosophila serrata, a novel host, and compared parameter estimates with those from three naturally occurring Drosophila-Wolbachia associations believed to be of different ages. Transfected D. serrata showed strong incompatibility, low transmission efficiency, and an associated fitness deficit, and they would probably be unable to spread in nature. The comparisons generally supported the predicted evolution of a host-Wolbachia association. The parameters peculiar to any given host-Wolbachia association may determine whether the microbial strain can spread in that host.

Geographic variation in wing shape in female Drosophila serrata was examined by characterizing isofemale strains from 19 localities collected along a transect on the eastern coast of Australia. Shape variation was analyzed by Procrustes superimposition of landmark data followed by canonical variate analysis. The first extracted canonical variate showed a nonlinear association with latitude and accounted for 43% of the variance. There was a sharp increase in this variate at low latitudes as well as a gradual increase at high latitudes. These shape changes were associated with two landmarks at the edge of the wing. There was also a linear change in wing aspect. The isofemale heritability for two measures of shape was around 30%. Allometric relationships were weak both between localities and among isofemale strains within localities. The possibility that wing shape parameters are under selection independent of wing size is discussed.

Eight populations of Drosophila serrata were used in a factorial design of the type 2 x 2 x 2 to study the influence of some environmental and genetic factors on the productivity and total size of a population under conditions of severe competition. The variables studied were two temperatures (25 C versus 19 C), two feeding schedules (2 versus 3 food units per week), and two genetic compositions (single strain versus two strain hybrid population). The parameters measured were the number of flies, the biomass produced per food unit, and the total population size. The results show that the amount of food is the main factor controlling the number of flies and the biomass produced by a population. The higher temperature has a slight favorable effect on the number of flies, but not on the biomass produced; that is, at 25 C a few more flies are produced but they are lighter. When the flies oviposit in the bottle for a longer time, the number of flies and the biomass produced are increased. The main factor contr...

Biological evolution results from natural selection promoting or conserving the adaptedness of populations of organisms to their changing environments. The fitness, or adaptedness, of a population to its environment is a property of prime importance in evolutionary studies. Population adaptedness must be quantified in order to measure the effect of natural selection on a population, or in order to compare meaningfully different populations. Average population size after achievement of an equilibrium, and numbers of individuals produced per unit time, were used as measures of the relative adaptedness of three geographic strains of D. serrata (Ayala, 1965). The adaptedness of the populations was estimated at two temperatures, 19C and 25C. The experiments reported now represent an attempt to measure the fitness of these three geographic strains of D. serrata by their performance in interspecific competition. Three experiments were carried out. In the first experiment each strain of D. serrata competed with a standard strain of D. pseudoobscura; in the second experiment they competed with a strain of D. melanogaster; and in the third experiment each strain of D. serrata competed with a strain of D. nebulosa. The first two experiments were performed at 2 5C, and the third at 19C. One objective of these experiments was to find out whether there was any consistency among the estimates of relative fitness in the various interspecific competitions, and of these estimates with those obtained in the previous experiment where fitness was measured by population size and productivity of single-species populations.

Laboratory populations of several geographic strains of the sibling species, Drosophila serrata and D. birchii were studied. Under the experimental conditions, the biomass produced by a population is determined by the amount of food, and it is independent of temperature and the feeding schedule. The number of flies produced is determined mainly by the amount of food, temperature having a slight effect. Living space determines the size of the population, which is independent of the amount of food and of temperature. See full-text article at JSTOR

Drosophila serrata Malloch (1927) is a species belonging to the melanogaster section of the subgenus Sophaphora and was originally described from a locality (Eidsvold) in Queensland, Australia. A redescription, in the form now accepted in Drosophila systematics, was made by Mather in 1955. Dobzhansky and Mather (1961) collected living specimens in eight localities of New South Wales and Queensland in Australia, and in New Guinea and New Britain. They distinguished two subspecies, the southern D. serrata serrata in New South Wales and most of Queensland, and the northern D. serrata birchii from Cairns, Queensland, to New Guinea and New Britain. The southern subspecies was described as having females with darker abdomens and males with two pairs of strong bristles in the genital arch. The northern group was characterized as having lighter females and three pairs of bristles in the male genitalia. More recently, some 15 strains were collected by H. L. Carson and M. Wasserman. The present paper reports the results obtained from the study of all the available strains. It will be shown that the subspecies described by Dobzhansky and Mather are, in fact, two reproductively completely isolated species, D. serrata and D. birchii, which are sympatric at several localities. A strain collected in a locality of New Guinea (Madang) belongs to a third sibling species, fully isolated from the other two, which I have named Drosophila dominicana. A description of this new species has been published elsewhere (Ayala, 1965a).

Changes which enhance adaptedness to the environment occur in experimental populations of Drosophila serrata which are acted upon by strong natural selection. The improvement is greater in hybrid than in single-strain populations because genetic variability is greater in the former.

A CONTROVERSY1,2 has arisen over the interpretation of the results of an experiment by Ayala3 purporting to invalidate the “competitive exclusion principle” which was defined in terms of the Volterra competition equations. The invalidation was based on a competition experiment between Drosophila serrata and D. pseudoobscura where the two species were in apparent equilibrium, and from which the following parameters were calculated: where K is the maximum number of individuals attainable when only one species is present, and N is the number actually observed at equilibrium. These parameters when estimated from Ayala's results were such that stability would not be predicted between the two competing species, and thus the competitive exclusion principle was rejected. Borowsky1 re-analysed the data, and concluded that a stable equilibrium was not present, and that the depression in yield of the mixed populations was caused by decreased fitness of each species from short term fluctuations in temperature that resulted in an environment optimal for neither species. Ayala subsequently2 replied to these criticisms.

AYALA has written of the so-called “experimental invalidation of the principle of competitive exclusion”, describing experiments on competition between two species, Drosophila serrata and D. pseudoobscura1. He observed that two species of Drosophila competing for limited resources of food and space can coexist. He says that there is direct evidence that D. serrata is superior in competitive fitness to D. pseudoobscura at the larval stage (solid phase of the environment), but inferior to it at the adult stage (aerial phase of the environment).