| 1. |
- Ah-King, Malin, 1973-, et al.
(author)
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Sex in an Evolutionary Perspective : Just Another Reaction Norm
- 2010
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 37:4, s. 234-246
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Research review (peer-reviewed)abstract
- It is common to refer to all sorts of clear-cut differences between the sexes as something that is biologically almost inevitable. Although this does not reflect the status of evolutionary theory on sex determination and sexual dimorphism, it is probably a common view among evolutionary biologists as well, because of the impact of sexual selection theory. To get away from thinking about biological sex and traits associated with a particular sex as something static, it should be recognized that in an evolutionary perspective sex can be viewed as a reaction norm, with sex attributes being phenotypically plastic. Sex determination itself is fundamentally plastic, even when it is termed “genetic”. The phenotypic expression of traits that are statistically associated with a particular sex always has a plastic component. This plasticity allows for much more variation in the expression of traits according to sex and more overlap between the sexes than is typically acknowledged. Here we review the variation and frequency of evolutionary changes in sex, sex determination and sex roles and conclude that sex in an evolutionary time-frame is extremely variable. We draw on recent findings in sex determination mechanisms, empirical findings of morphology and behaviour as well as genetic and developmental models to explore the concept of sex as a reaction norm. From this point of view, sexual differences are not expected to generally fall into neat, discrete, pre-determined classes. It is important to acknowledge this variability in order to increase objectivity in evolutionary research.
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| 2. |
- Ah-King, Malin, et al.
(author)
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The "Sex Role" Concept : An Overview and Evaluation
- 2013
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 461-470
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Research review (peer-reviewed)abstract
- "Sex roles" are intuitively associated to stereotypic female and male sexual strategies and in biology, the term "sex role" often relates to mating competition, mate choice or parental care. "Sex role reversals" imply that the usual typological pattern for a population or species is deviates from a norm, and the meaning of "sex role reversal" thus varies depending upon whatever is the usual pattern of sex-typical behavior in a given taxon. We identify several problems with the current use of the "sex role" concept. (1) It is typological and reflects stereotypic expectations of the sexes. (2) The term "sex role" parses continuous variation into only two categories, often obscuring overlap, between the sexes in behavior and morphology, and variability in relation to ecological circumstances. (3) Common generalizations such as "sex role as seen in nature" mask variation upon which selection may act. (4) The general meaning of "sex roles" in society (i.e. "socially and culturally defined prescriptions and beliefs about the behavior and emotions of men and women") is contrary to biological "sex role" concepts, so that confusing the two obscure science communication in society. We end by questioning the validity of the "sex role" concept in evolutionary biology and recommend replacing the term "sex role" with operational descriptions.
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| 3. |
- Ahnesjö, Ingrid, et al.
(author)
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Considering gender‑biased assumptions in evolutionary biology
- 2020
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In: Evolutionary biology. - : Springer Nature. - 0071-3260 .- 1934-2845. ; 47, s. 1-5
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Journal article (peer-reviewed)abstract
- Many organisms studied by evolutionary biologists have different sexes, and the evolution of separate sexes and sexual dimorphisms in morphology and behaviour are central questions in evolutionary biology. Considering scientists to be embedded in a social and cultural context, we are also subjected to the risk of gender-biased assumptions and stereotypical thinking to appear when working on topics related to sexual reproduction and sexual dimorphism. Here we present, for continued discussion, a set of good-practice guidelines aimed at (1) helping to improve researchers’ awareness of gender-biased assumptions underlying language use, generalizations, and interpretation of observations; and (2) providing recommendations to increase transparency, avoid problematic terminology, and improve study designs.
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| 4. |
- Drobniak, Szymon M., et al.
(author)
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Maternal Age-Related Depletion of Offspring Genetic Variance in Immune Response to Phytohaemagglutinin in the Blue Tit (Cyanistes caeruleus)
- 2015
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 42:1, s. 88-98
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Research review (peer-reviewed)abstract
- Studies examining age-specific patterns in genetic variance have focussed primarily on changes in the genetic variance within cohorts. It remains unclear whether parental age may affect the genetic variance among offspring. To date, such an effect has been reported only in a single study performed in a wild bird population. Here, we provide experimental evidence that the additive genetic variance (V-A) observed among offspring may be related to parental age in a wild passerine-the blue tit (Cyanistes caeruleus). To separate genetic and environmental components of phenotypic variance in nestling body size and immune function we cross-fostered nestlings between pairs of broods born to young and old mothers and used an animal model to estimate V-A. We show that the genetic variance in immune response to phytohaemagglutinin (PHA) and body weight among offspring depends on maternal age. V-A in response to PHA appeared to be lower among nestlings of older mothers. Such a tendency was not observed for tarsus length. We argue that the lower V-A may result either from depletion of additive genetic variation due to selection acting on parents across age classes or from environmental effects confounded with parental age. Thus, our study suggests that parental age may significantly affect estimates of quantitative genetic parameters in the offspring.
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| 5. |
- Eroukhmanoff, F., et al.
(author)
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Effect of Species Interaction on Beak Integration in an Avian Hybrid Species Complex
- 2014
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In: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 41:3, s. 452-458
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Journal article (peer-reviewed)abstract
- Theory predicts that variability in size and the shape of a morphological trait should often be stable both at the intra- and interspecific level. We studied variation in beak integration among several populations of two species of the genus Passer, a hybrid species, the Italian sparrow (Passer italiae) and one of its parents, the Spanish sparrow (Passer hispaniolensis). We show that the general shape of the beak has been conserved in these two species and that hybrid speciation has had no major effects on beak integration. However, in young, sympatric populations, phenotypic integration between beak height and length decreased significantly, to the extent that these two dimensions apparently became independent. This displacement in phenotypic integration seems to be accompanied with changes in the distribution of phenotypic variation at the univariate level. This suggests that while beak shape may have been constrained over evolutionary time-scales and major hybridization events (i.e. the formation of the hybrid Italian sparrow), under specific selection regimes linked to secondary contact, it can evolve rapidly.
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| 6. |
- Eroukhmanoff, Fabrice
(author)
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Just How Much is the G-matrix Actually Constraining Adaptation?
- 2009
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In: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 36:3, s. 323-326
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Research review (peer-reviewed)abstract
- The genetic variance-covariance matrix (G) has long been considered to summarize the genetic constraints biasing evolution in its early stages, although in some instances, G can enhance divergence and facilitate adaptation. However, the effects of G on the response to selection might be of less importance than previously thought. In addition, it has been suggested that selection itself, under certain conditions, might rapidly alter the genetic covariance structure. If selection can indeed affect the stability of G to facilitate evolution, the overall structure of G might not be as important to consider as the past selective conditions that G was subject to. Thus, more empirical work is needed on the stability of G in the early stages of divergence before one can really assess to what extent G constrains evolution.
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| 7. |
- Eroukhmanoff, Fabrice, et al.
(author)
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Patterns of Phenotypic Divergence in Wing Covariance Structure of Calopterygid Damselflies
- 2009
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In: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 36:2, s. 214-224
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Research review (peer-reviewed)abstract
- Comparing species differences in covariance patterns of traits subject to divergent selection pressures can increase our understanding to the mechanisms of phenotypic divergence. Different species of calopterygid damselflies have diverged in the melanized wing patch of males. This trait serves multiple ecological functions and has behavioral consequences in terms of sexual selection, interspecific interactions, reproductive isolation. We compared the phenotypic variance-covariance matrices (P) of wing traits among nine populations of four European species of calopterygid damselflies. We found modest divergence in covariance structure among populations of the same species, but strong divergence between species. Interestingly, the orientation of the first eigenvector of P (P (max) ) differed more between closely related species than between distantly related species, although this pattern was absent when overall covariance structures were compared. We also found that distantly related species but geographically closer had converged towards a similar covariance structure. Finally, divergence in covariance structure was correlated with divergence in wing patch length, but not with other wing traits. This last finding suggests that divergent selection on wing patch length might have affected the stability of P. These results indicate that P might not only reflect ancestral developmental pathways but might also be influenced by current ecology.
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| 8. |
- Goenaga, Julieta, et al.
(author)
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Latitudinal Variation in Starvation Resistance is Explained by Lipid Content in Natural Populations of Drosophila melanogaster
- 2013
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 601-612
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Research review (peer-reviewed)abstract
- One of the most common environmental stressors is a shortage or suboptimal quality of food, thus all animals deal with periods of starvation. In the present study we examine variation in starvation resistance, longevity and body lipid content and the correlations between traits along an environmental gradient using isofemale lines recently derived from natural populations of Drosophila melanogaster from South America. The use of isofemale lines and controlled rearing laboratory conditions allows us to investigate within and among population components of genetic variation and the potential associations among starvation resistance, longevity and body lipid content. All these traits were analyzed separately in females and males, improving our understanding of sexual dimorphism. Our results revealed significant differences among populations in starvation resistance and longevity. Actually, the opposing latitudinal cline detected for starvation resistance suggests that natural selection played an essential role in shaping the pattern of geographic variation in this trait. Moreover, we also detected a positive relationship between starvation resistance and body lipid content in both sexes, providing evidence for a physiological and/or evolutionary association between these traits. Conversely, starvation resistance was not correlated with longevity indicating that these traits might be enabled to evolve independently. Finally, our study reveals that there is abundant within population genetic variation for all traits that may be maintained by sex-specific effects.
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| 9. |
- Johansson, Frank, et al.
(author)
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Morphological Consequences of Developmental Plasticity in Rana temporaria are not Accommodated into Among-Population or Among-Species Variation
- 2016
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 43:2, s. 242-256
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Journal article (peer-reviewed)abstract
- Environmental induced developmental plasticity occurs in many organisms and it has been suggested to facilitate biological diversification. Here we use ranid frogs to examine whether morphological changes derived from adaptive developmental acceleration in response to pool drying within a species are mirrored by differences among populations and across species. Accelerated development in larval anurans under pool drying conditions is adaptive and often results in allometric changes in limb length and head shape. We examine the association between developmental rate and morphology within population, among populations in divergent environments, and among species inside the Ranidae frog family, combining experimental approaches with phylogenetic comparative analyses. We found that frogs reared under decreasing water conditions that simulated fast pool drying had a faster development rate compared to tadpoles reared on constant water conditions. This faster developmental rate resulted in different juvenile morphologies between the two pool drying conditions. The association between developmental rate and morphology found as a result of plasticity was not mirrored by differences among populations that differed in development, neither was it mirrored among species that differed in development rate. We conclude that morphological differences among populations and species were not driven by variation in developmental time per se. Instead, selective factors, presumably operating on locomotion and prey choice, seem to have had a stronger evolutionary effect on frog morphology than evolutionary divergences in developmental rate in the ranid populations and species studied.
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| 10. |
- Johansson, Frank, et al.
(author)
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Within-Population Developmental and Morphological Plasticity is Mirrored in Between-Population Differences : Linking Plasticity and Diversity
- 2013
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In: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 494-503
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Research review (peer-reviewed)abstract
- It has been suggested that phenotypic plasticity can facilitate evolutionary diversification of organisms. If life-history and morphological diversification across a lineage is mirrored in diversification in the same traits due to phenotypic plasticity within a lineage it fulfils one of the expectations that are needed to support this diversification hypothesis. We carried out a laboratory study to examine development rate and morphology between and within populations of the parsley frog, Pelodytes punctatus. We found that frogs reared in the laboratory had a longer development time, relatively longer hind legs and relatively narrower heads under constant water level compared to those under decreasing water level simulating pool drying. This adaptive phenotypic plasticity response to pool drying was mirrored across populations because frogs from permanent waters had longer development times, relatively longer hind legs and relatively narrower heads compared to frogs from temporary waters. Hence the developmental and morphological plasticity observed within populations was also observed between populations as constitutive expressed traits. We suggest that the morphology pattern observed was driven by a common developmental process (time to metamorphosis), indicating that plasticity may contribute to evolutionary change, ultimately resulting in genetic accommodation of the morphological traits.
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