| 1. |
- Le Rouzic, Arnaud, et al.
(författare)
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Evolutionary Time-Series Analysis Reveals the Signature of Frequency-Dependent Selection on a Female Mating Polymorphism
- 2015
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 185:6, s. 182-196
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in evolutionary biology is understanding how stochastic and deterministic factors interact and influence macroevolutionary dynamics in natural populations. One classical approach is to record frequency changes of heritable and visible genetic polymorphisms over multiple generations. Here, we combined this approach with a maximum likelihood-based population-genetic model with the aim of understanding and quantifying the evolutionary processes operating on a female mating polymorphism in the blue-tailed damselfly Ischnura elegans. Previous studies on this color-polymorphic species have suggested that males form a search image for females, which leads to excessive mating harassment of common female morphs. We analyzed a large temporally and spatially replicated data set of between-generation morph frequency changes in I. elegans. Morph frequencies were more stable than expected from genetic drift alone, suggesting the presence of selection toward a stable equilibrium that prevents local loss or fixation of morphs. This can be interpreted as the signature of negative frequency-dependent selection maintaining the phenotypic stasis and genetic diversity in these populations. Our novel analytical approach allows the estimation of the strength of frequency-dependent selection from the morph frequency fluctuations around their inferred long-term equilibria. This approach can be extended and applied to other polymorphic organisms for which time-series data across multiple generations are available.
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| 2. |
- Abbott, Jessica, et al.
(författare)
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Correlated morphological and colour differences among females of the damselfly Ischnura elegans
- 2009
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Ingår i: Ecological Entomology. - : Wiley. - 1365-2311 .- 0307-6946. ; 34:3, s. 378-386
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Tidskriftsartikel (refereegranskat)abstract
- 1. The female-limited colour polymorphic damselfly Ischnura elegans has proven to be an interesting study organism both as an example of female sexual polymorphism, and in the context of the evolution of colour polymorphism, as a model of speciation processes. 2. Previous research suggests the existence of correlations between colour morph and other phenotypic traits, and the different female morphs in I. elegans may be pursuing alternative phenotypically integrated strategies. However, previous research on morphological differences in southern Swedish individuals of this species was only carried out on laboratory-raised offspring from a single population, leaving open the question of how widespread such differences are. 3. The present study therefore analysed multi-generational data from 12 populations, investigating morphological differences between the female morphs in the field, differences in the pattern of phenotypic integration between morphs, and quantified selection on morphological traits. 4. It was found that consistent morphological differences indeed existed between the morphs across populations, confirming that the previously observed differences were not simply a laboratory artefact. It was also found, somewhat surprisingly, that despite the existence of sexual dimorphism in body size and shape, patterns of phenotypic integration differed most between the morphs and not between the sexes. Finally, linear selection gradients showed that female morphology affected fecundity differently between the morphs. 5. We discuss the relevance of these results to the male mimicry hypothesis and to the existence of potential ecological differences between the morphs.
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| 3. |
- Abbott, J. K., et al.
(författare)
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Patterns of differentiation in a colour polymorphism and in neutral markers reveal rapid genetic changes in natural damselfly populations
- 2008
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Ingår i: Molecular Ecology. - : Wiley-Blackwell. - 0962-1083 .- 1365-294X. ; 17:6, s. 1597-1604
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Tidskriftsartikel (refereegranskat)abstract
- The existence and mode of selection operating on heritable adaptive traits can be inferred by comparing population differentiation in neutral genetic variation between populations (often using F-ST values) with the corresponding estimates for adaptive traits. Such comparisons indicate if selection acts in a diversifying way between populations, in which case differentiation in selected traits is expected to exceed differentiation in neutral markers [F-ST (selected) > F-ST (neutralfl, or if negative frequency-dependent selection maintains genetic polymorphisms and pulls populations towards a common stable equilibrium [FST (selected) < F-ST (neutral)]. Here, we compared F-ST values for putatively neutral data (obtained using amplified fragment length polymorphism) with estimates of differentiation in morph frequencies in the colour-polymorphic damselfly Ischnura elegans. We found that in the first year (2000), population differentiation in morph frequencies was significantly greater than differentiation in neutral loci, while in 2002 (only 2 years and 2 generations later), population differentiation in morph frequencies had decreased to a level significantly lower than differentiation in neutral loci. Genetic drift as an explanation for population differentiation in morph frequencies could thus be rejected in both years. These results indicate that the type and/or strength of selection on morph frequencies in this system can change substantially between years. We suggest that an approach to a common equilibrium morph frequency across all populations, driven by negative frequency-dependent selection, is the cause of these temporal changes. We conclude that inferences about selection obtained by comparing F-ST values from neutral and adaptive genetic variation are most useful when spatial and temporal data are available from several populations and time points and when such information is combined with other ecological sources of data.
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| 4. |
- Gosden, Thomas, et al.
(författare)
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Asymmetric isolating barriers between different microclimatic environments caused by low immigrant survival.
- 2015
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 282:1802
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Tidskriftsartikel (refereegranskat)abstract
- Spatially variable selection has the potential to result in local adaptation unless counteracted by gene flow. Therefore, barriers to gene flow will help facilitate divergence between populations that differ in local selection pressures. We performed spatially and temporally replicated reciprocal field transplant experiments between inland and coastal habitats using males of the common blue damselfly (Enallagma cyathigerum) as our study organism. Males from coastal populations had lower local survival rates than resident males at inland sites, whereas we detected no differences between immigrant and resident males at coastal sites, suggesting asymmetric local adaptation in a source-sink system. There were no intrinsic differences in longevity between males from the different environments suggesting that the observed differences in male survival are environment-dependent and probably caused by local adaptation. Furthermore, the coastal environment was found to be warmer and drier than the inland environment, further suggesting local adaptation to microclimatic factors has lead to differential survival of resident and immigrant males. Our results suggest that low survival of immigrant males mediates isolation between closely located populations inhabiting different microclimatic environments.
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| 5. |
- Gosden, Thomas, et al.
(författare)
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Density-dependent male mating harassment, female resistance, and male mimicry.
- 2009
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 173:6, s. 709-721
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Tidskriftsartikel (refereegranskat)abstract
- Genetic variation in female resistance and tolerance to male mating harassment can affect the outcome of sexually antagonistic mating interactions. We investigated female mating rates and male mating harassment in natural populations of a damselfly (Ischnura elegans). This damselfly species has a heritable sex-limited polymorphism in females, where one of the morphs is a male mimic (androchrome females). The three female morphs differ in mating rates, and these differences are stable across populations and years. However, the degree of premating resistance toward male mating attempts varied across generations and populations. Male mating harassment of the female morphs changed in a density-dependent fashion, suggesting that male mate preferences are plastic and vary with the different morph densities. We quantified morph differences in male mating harassment and female fecundity, using path analysis and structural equation modeling. We found variation between the morphs in the fitness consequences of mating, with the fecundity of one of the nonmimetic morphs declining with increasing male mating harassment. However, androchrome females had lower overall fecundity, presumably reflecting a cost of male mimicry. Density-dependent male mating harassment on the morphs and fecundity costs of male mimicry are thus likely to contribute to the maintenance of this female polymorphism.
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| 6. |
- Gosden, Thomas, et al.
(författare)
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Female sexual polymorphism and fecundity consequences of male mating harassment in the wild
- 2007
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Ingår i: PLoS ONE. ; 2:6
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Tidskriftsartikel (refereegranskat)abstract
- Genetic and phenotypic variation in female response towards male mating attempts has been found in several laboratory studies, demonstrating sexually antagonistic co-evolution driven by mating costs on female fitness. Theoretical models suggest that the type and degree of genetic variation in female resistance could affect the evolutionary outcome of sexually antagonistic mating interactions, resulting in either rapid development of reproductive isolation and speciation or genetic clustering and female sexual polymorphisms. However, evidence for genetic variation of this kind in natural populations of non-model organisms is very limited. Likewise, we lack knowledge on female fecundity-consequences of matings and the degree of male mating harassment in natural settings. Here we present such data from natural populations of a colour polymorphic damselfly. Using a novel experimental technique of colour dusting males in the field, we show that heritable female colour morphs differ in their propensity to accept male mating attempts. These morphs also differ in their degree of resistance towards male mating attempts, the number of realized matings and in their fecundity-tolerance to matings and mating attempts. These results show that there may be genetic variation in both resistance and tolerance to male mating attempts (fitness consequences of matings) in natural populations, similar to the situation in plant-pathogen resistance systems. Male mating harassment could promote the maintenance of a sexual mating polymorphism in females, one of few empirical examples of sympatric genetic clusters maintained by sexual conflict.
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| 7. |
- Gosden, Thomas, et al.
(författare)
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Range limits, large-scale biogeographic variation, and localized evolutionary dynamics in a polymorphic damselfly
- 2011
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066. ; 102:4, s. 775-785
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Tidskriftsartikel (refereegranskat)abstract
- Studies of heritable colour polymorphisms allow investigators to track the genetic dynamics of natural populations. By comparing polymorphic populations over large geographic areas and across generations, issues about both morph stability and evolutionary dynamics can be addressed, increasing our understanding of the potential mechanisms maintaining genetic polymorphisms. In the present study, we investigated population morph frequencies in a sex-limited heritable colour polymorphic damselfly (Ischnura elegans, Vander Linden), with three discrete female morphs. We compared the frequencies of these three female morphs in 120 different populations from ten European countries at differing latitudes and longitudes. There were pronounced differences in morph frequencies both across the entire European biogeographic range, as well as at a smaller scale within regions. We also found considerable between-population variation at the local scale within regions, particularly at the edges of the range of this species. We discuss these findings in the context of recent models of adaptive population divergence along the range of a species. This polymorphism is thus highly dynamic, with stable morph frequencies at the core of the species range but fluctuating morph dynamics at the range limits. We finish with a discussion of how local interactions and climatic factors can be expected to have a strong influence on the biogeographic patterns in this species and other sexually selected polymorphisms. (c) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 775-785.
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| 8. |
- Gosden, Thomas, et al.
(författare)
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SPATIAL AND TEMPORAL DYNAMICS IN A SEXUAL SELECTION MOSAIC.
- 2008
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Ingår i: Evolution. - 1558-5646. ; 62, s. 845-856
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Tidskriftsartikel (refereegranskat)abstract
- Selective regimes and phenotypic optima could either change smoothly and in a clinal fashion or be spatially organized in a more unpredictable mosaic pattern over the geographic landscape. When natural or sexual selection is driven by intra- or interspecific biotic interactions, fine-grained spatial variation in selective regimes could result in selection mosaics rather than clinal variation in selection. We investigated temporal variation and spatial organization in sexual selection on male body size along an ecological coastal-inland gradient of a polymorphic damselfly Ischnura elegans. Body size increased in a clinal fashion along this gradient: animals were smaller in size at the coast, but became larger in the inland areas. In contrast, the sexual selection regimes on male body size showed evidence of more fine-grained spatial organization with no evidence for a clinal pattern and low spatial autocorrelations between populations. These spatially fine-grained sexual selection regimes varied in sign and magnitude and were driven by a combination of the densities of heritable female color morphs and local female body sizes. We suggest that the spatial organization of the selective regimes can be interpreted as a sexual selection mosaic that is influenced by highly localized density- and frequency-dependent social interactions.
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| 9. |
- Gosden, Thomas, et al.
(författare)
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Testing the correlated response hypothesis for the evolution and maintenance of male mating preferences in Drosophila serrata.
- 2014
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 27:10, s. 2106-2112
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Tidskriftsartikel (refereegranskat)abstract
- Mate preferences are abundant throughout the animal kingdom with female preferences receiving the most empirical and theoretical attention. Although recent work has acknowledged the existence of male mate preferences, whether they have evolved and are maintained as a direct result of selection on males or indirectly as a genetically correlated response to selection for female choice remains an open question. Using the native Australian species Drosophila serrata in which mutual mate choice occurs for a suite of contact pheromones (cuticular hydrocarbons or CHCs), we empirically test key predictions of the correlated response hypothesis. First, within the context of a quantitative genetic breeding design, we estimated the degree to which the trait values favoured by male and female choice are similar both phenotypically and genetically. The direction of sexual selection on male and female CHCs differed statistically, and the trait combinations that maximized male and female mating success were not genetically correlated, suggesting that male and female preferences target genetically different signals. Second, despite detecting significant genetic variance in female preferences, we found no evidence for genetic variance in male preferences and, as a consequence, no detectable correlation between male and female mating preferences. Combined, these findings are inconsistent with the idea that male mate choice in D. serrata is simply a correlated response to female choice. Our results suggest that male and female preferences are genetically distinct traits in this species and may therefore have arisen via different evolutionary processes.
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| 10. |
- Gosden, Thomas, et al.
(författare)
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The B-matrix harbors significant and sex-specific constraints on the evolution of multicharacter sexual dimorphism.
- 2012
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 66:7, s. 2106-2116
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Tidskriftsartikel (refereegranskat)abstract
- The extent to which sexual dimorphism can evolve within a population depends on an interaction between sexually divergent selection and constraints imposed by a genetic architecture that is shared between males and females. The degree of constraint within a population is normally inferred from the intersexual genetic correlation, r(mf) . However, such bivariate correlations ignore the potential constraining effect of genetic covariances between other sexually coexpressed traits. Using the fruit fly Drosophila serrata, a species that exhibits mutual mate preference for blends of homologous contact pheromones, we tested the impact of between-sex between-trait genetic covariances using an extended version of the genetic variance-covariance matrix, G, that includes Lande's (1980) between-sex covariance matrix, B. We find that including B greatly reduces the degree to which male and female traits are predicted to diverge in the face of divergent phenotypic selection. However, the degree to which B alters the response to selection differs between the sexes. The overall rate of male trait evolution is predicted to decline, but its direction remains relatively unchanged, whereas the opposite is found for females. We emphasize the importance of considering the B-matrix in microevolutionary studies of constraint on the evolution of sexual dimorphism.
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| 11. |
- Gosden, Thomas, et al.
(författare)
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The evolutionary stability of cross-sex, cross-trait genetic covariances
- 2014
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Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 68:6, s. 1687-1697
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Tidskriftsartikel (refereegranskat)abstract
- Although knowledge of the selective agents behind the evolution of sexual dimorphism has advanced considerably in recent years, we still lack a clear understanding of the evolutionary durability of cross-sex genetic covariances that often constrain its evolution. We tested the relative stability of cross-sex genetic covariances for a suite of homologous contact pheromones of the fruit fly Drosophila serrata, along a latitudinal gradient that these traits have diverged in mean. Using a Bayesian framework, which allowed us to account for uncertainty in all parameter estimates, we compared divergence in the total amounts and orientations of genetic variance across populations, finding divergence in orientation but not total variance. We then statistically compared orientation divergence of within-sex (G) to cross-sex (B) covariance matrices. In line with a previous theoretical prediction, we find that the cross-sex covariance matrix, B, is more variable than either male or female within-sex covariance matrix. Decomposition of B matrices into their symmetrical and non-symmetrical components revealed that instability is linked to the degree of asymmetry. We also find that the degree of asymmetry correlates with latitude suggesting a role for spatially varying natural selection in shaping genetic constraints on the evolution of sexual dimorphism. This article is protected by copyright. All rights reserved.
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| 12. |
- Gosden, Thomas
(författare)
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The Preservation of Favoured Morphs in the Struggle Between Sexes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sexual selection is particularly likely to promote population divergence, because sexual traits are expected to be subject to rapid evolutionary change. Identifying the relative roles of particular barriers to the amount of total reproductive isolation between populations or closely related species can provide important clues to the mechanisms of population divergence and speciation Phenotypic trait differences among populations are thought to reflect the interaction between the intensity of gene flow versus the strength of local selection and drift. Low levels of gene flow between populations will facilitate adaptation to the local environment and increase the strength of genetic drift. Conversely, when there is extensive gene flow circulating between populations, the high “migration load” will potentially enhance the level of population maladaptation. I examine the evolutionary dynamics of interactions between the sexes, and the significance of these interactions in shaping patterns of temporal and spatial population divergence. In my studies I take advantage of a female polymorphism, as colour polymorphisms in natural populations provide a visual marker that greatly aids in studies of the maintenance of genetic variation, as well as the mechanisms driving spatial and temporal fluctuations in selection regimes. In this thesis I investigated population divergence, changes in local selection patterns, female variation in response to male harassment, and large scale biogeographic patterns. The main goal of these studies was to aid in the understanding the evolutionary processes involved in the maintenance of genetic variation as well as potential causes of reproductive isolation and speciation. I also developed a theoretical model to examine consequences of male sperm limitations on mutual mate choice and conflicts between the sexes. Variation in selection is caused by feedbacks between the interacting phenotypes, both between and within the sexes. The studies in this thesis show that these feedbacks arise from the interaction between frequency-dependent and density-dependent dynamics of the female morphs, which in turn influence the spatially varying sexual selection regimes on males. The combination of the studies in this thesis demonstrates that local intra-specific interactions can have an important influence on observed large-scale biogeographic differentiation within a species.
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| 13. |
- Härdling, Roger, et al.
(författare)
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Male mating constraints affect mutual mate choice: prudent male courting and sperm-limited females.
- 2008
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 172:2, s. 259-271
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Tidskriftsartikel (refereegranskat)abstract
- Costs of sperm production may lead to prudence in male sperm allocation and also to male mate choice. Here, we develop a life history-based mutual mate choice model that takes into account the lost-opportunity costs for males from time out in sperm recovery and lets mate competition be determined by the prevailing mate choice strategies. We assume that high mating rate may potentially lead to sperm depletion in males, and that as a result, female reproduction may be limited by the availability of sperm. Increasing variation in male quality leads, in general, to increased selective mate choice by females, and vice versa. Lower-quality males may, however, gain access to more fecund higher-quality females by lowering their courting rate, thus increasing their sperm reserves. When faced with strong male competition for mates, low-quality males become less choosy, which leads to assortative mating for quality and an increased mating rate across all males. With assortative mating, the frequency of antagonistic interactions (sexual conflict) is reduced, allowing males to lower the time spent replenishing sperm reserves in order to increase mating rate. This in turn leads to lower sperm levels at mating and therefore could lead to negative effects on female fitness via sperm limitation.
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| 14. |
- Reddiex, Adam J., et al.
(författare)
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Sex-Specific Fitness Consequences of Nutrient Intake and the Evolvability of Diet Preferences
- 2013
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 182:1, s. 91-102
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Tidskriftsartikel (refereegranskat)abstract
- The acquisition of nutrients is fundamental for the maintenance of bodily functions, growth, and reproduction in animals. As a result, fitness can be maximized only when animals are able to direct their attention to foods that reflect their current nutritional needs. Despite significant literature documenting the fitness consequences of nutrient composition and preference, less is known about the underlying genetic architecture of the dietary preferences themselves, specifically, the degree to which they can respond to selection. We addressed this by integrating evolutionary quantitative genetics and nutritional geometry to examine the shape of the sex-specific fitness surfaces and the availability of genetic variance for macronutrient preferences in the fruit fly Drosophila melanogaster. Combining these analyses, we found that the microevolutionary potential of carbohydrate and protein preference was above average in this population, because the expected direction of selection was relatively well aligned with the major axis of the genetic variance-covariance matrix, G. We also found that potential exists for sexually antagonistic genetic constraint in this system; macronutrient blends maximizing fitness differed between the sexes, and cross-sex genetic correlations for their consumption were positive. However, both sexes were displaced from their feeding optima, generating similar directional selection on males and females, with the combined effect being that minimal sex-specific genetic constraints currently affect dietary preferences in this population.
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| 15. |
- Svensson, Erik, et al.
(författare)
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Contemporary evolution of secondary sexual traits in the wild
- 2007
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 21:3, s. 422-433
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Tidskriftsartikel (refereegranskat)abstract
- 1. Sexual selection has been studied intensively, and is often strong in natural populations. Theoretical models, comparative studies and laboratory selection experiments all suggest that evolution driven by sexual selection should be rapid and common. 2. However, there are relatively few documented cases of the contemporary evolution of secondary sexual traits in natural populations. Moreover, the causes are not always due to sexual selection, but often due to altered natural selection regimes, or an altered balance between natural and sexual selection. 3. Here we discuss recent empirical studies that have demonstrated the contemporary evolution of secondary sexual traits in natural populations. Our examples include both continuous traits and discrete polymorphisms. Taxa in which the contemporary (rapid) evolution of secondary sexual traits have been demonstrated include fish, insects, mammals, reptiles and birds. The evolutionary rates of these changes range from 0.005 to 0.570 haldanes (arithmetic mean = 0.14; geometric mean = 0.095; median = 0.12). 4. The relative rarity of examples could be explained by different genetic architectures of sexually selected traits compared with naturally selected traits, or by sexual selection regimes not being sustained in the long term. These factors could potentially slow down evolutionary rates of secondary sexual traits and make the detection of the contemporary evolution empirically more difficult. 5. Promising and underutilized approaches to sexual selection research include reciprocal transplant experiments and estimation of sexual isolation between conspecific populations.
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| 16. |
- Svensson, Erik, et al.
(författare)
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Female polymorphisms, sexual conflict and limits to speciation processes in animals
- 2009
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Ingår i: Evolutionary Ecology. - : Springer Science and Business Media LLC. - 1573-8477 .- 0269-7653. ; 23:1, s. 93-108
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Forskningsöversikt (refereegranskat)abstract
- Heritable and visually detectable polymorphisms, such as trophic polymorphisms, ecotypes, or colour morphs, have become classical model systems among ecological geneticists and evolutionary biologists. The relatively simple genetic basis of many polymorphisms (one or a few loci) makes such species well-suited to study evolutionary processes in natural settings. More recently, polymorphic systems have become popular when studying the early stages of the speciation process and mechanisms facilitating or constraining the evolution of reproductive isolation. Although colour polymorphisms have been studied extensively in the past, we argue that they have been underutilized as model systems of constraints on speciation processes. Colouration traits may function as signalling characters in sexual selection contexts, and the maintenance of colour polymorphisms is often due to frequency-dependent selection. One important issue is why there are so few described cases of female polymorphisms. Here we present a synthetic overview of female sexual polymorphisms, drawing from our previous work on female colour polymorphisms in lizards and damselflies. We argue that female sexual polymorphisms have probably been overlooked in the past, since workers have mainly focused on male-male competition over mates and have not realized the ecological sources of genetic variation in female fitness. Recent experimental evolution studies on fruit flies (Drosophila melanogaster) have demonstrated significant heritable variation among female genotypes in the fitness costs of resistance or tolerance to male mating harassment. In addition, female-female competition over resources could also generate genetic variation in female fitness and promote the maintenance of female sexual polymorphisms. Female sexual polymorphisms could subsequently either be maintained as intrapopulational polymorphisms or provide the raw material for the formation of new species.
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