| 1. |
- Ah-King, Malin, 1973-, et al.
(författare)
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Sex in an Evolutionary Perspective : Just Another Reaction Norm
- 2010
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 37:4, s. 234-246
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Forskningsöversikt (refereegranskat)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.
(författare)
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The "Sex Role" Concept : An Overview and Evaluation
- 2013
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 461-470
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Forskningsöversikt (refereegranskat)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. |
- Eroukhmanoff, F., et al.
(författare)
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Effect of Species Interaction on Beak Integration in an Avian Hybrid Species Complex
- 2014
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Ingår i: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 41:3, s. 452-458
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Goenaga, Julieta, et al.
(författare)
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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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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 601-612
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Forskningsöversikt (refereegranskat)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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| 5. |
- Johansson, Frank, et al.
(författare)
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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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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 494-503
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Forskningsöversikt (refereegranskat)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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| 6. |
- Martínez-Abadías, Neus, et al.
(författare)
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The Developmental Basis of Quantitative Craniofacial Variation in Humans and Mice
- 2012
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 39:4, s. 554-567
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Forskningsöversikt (refereegranskat)abstract
- The human skull is a complex and highly integrated structure that has long held the fascination of anthropologists and evolutionary biologists. Recent studies of the genetics of craniofacial variation reveal a very complex and multifactorial picture. These findings contrast with older ideas that posit much simpler developmental bases for variation in cranial morphology such as the growth of the brain or the growth of the chondrocranium relative to the dermatocranium. Such processes have been shown to have major effects on cranial morphology in mice. It is not known, however, whether they are relevant to explaining normal phenotypic variation in humans. To answer this question, we obtained vectors of shape change from mutant mouse models in which the developmental basis for the craniofacial phenotype is known to varying degrees, and compared these to a homologous dataset constructed from human crania obtained from a single population with a known genealogy. Our results show that the shape vectors associated with perturbations to chondrocranial growth, brain growth, and body size in mice do largely correspond to axes of covariation in humans. This finding supports the view that the developmental basis for craniofacial variation funnels down to a relatively small number of key developmental processes that are similar across mice and humans. Understanding these processes and how they influence craniofacial shape provides fundamental insights into the developmental basis for evolutionary change in the human skull as well as the developmental-genetic basis for normal phenotypic variation in craniofacial form.
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| 7. |
- Outomuro, David, et al.
(författare)
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Hind wing shape evolves faster than front wing shape in Calopteryx damselflies
- 2012
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 39:1, s. 116-125
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Tidskriftsartikel (refereegranskat)abstract
- Wing shape has been shown in a variety of species to be influenced by natural and sexual selection. In damselflies, front- and hind wings can beat independently, and functional differentiation may occur. Males of Calopteryx damselflies show species-specific nuptial flights that differ in colour signalling with the hind wings. Therefore, hind wing shape and colour may evolve in concert to improve colour display, independent of the front wings. We predicted that male hind wing shape evolves faster than front wing shape, due to sexual selection. Females do not engage in sexual displays, so we predicted that females do not show differences in divergence between front- and hind wing shape. We analysed the nonallometric component of wing shape of five European Calopteryx taxa using geometric morphometrics. We found a higher evolutionary divergence of hind wing shape in both sexes. Indeed, we found no significant differences in rate of evolution between the sexes, despite clear sexspecific differences in wing shape. We suggest that evolution of hind wing shape in males is accelerated by sexual selection on pre-copulatory displays and that this acceleration is reflected in females due to genetic correlations that somehow link the rates of wing shape evolution in the two sexes, but not the wing shapes themselves.
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| 8. |
- Outomuro, David, et al.
(författare)
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The Evolution of Wing Shape in Ornamented-Winged Damselflies (Calopterygidae, Odonata)
- 2013
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:2, s. 300-309
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Forskningsöversikt (refereegranskat)abstract
- Flight has conferred an extraordinary advantage to some groups of animals. Wing shape is directly related to flight performance and evolves in response to multiple selective pressures. In some species, wings have ornaments such as pigmented patches that are sexually selected. Since organisms with pigmented wings need to display the ornament while flying in an optimal way, we might expect a correlative evolution between the wing ornament and wing shape. We examined males from 36 taxa of calopterygid damselflies that differ in wing pigmentation, which is used in sexual displays. We used geometric morphometrics and phylogenetic comparative approaches to analyse whether wing shape and wing pigmentation show correlated evolution. We found that wing pigmentation is associated with certain wing shapes that probably increase the quality of the signal: wings being broader where the pigmentation is located. Our results also showed correlated evolution between wing pigmentation and wing shape in hind wings, but not in front wings, probably because hind wings are more involved in signalling than front wings. The results imply that the evolution of diversity in wing pigmentations and behavioural sexual displays might be an important driver of speciation due to important pre-copulatory selective pressures.
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| 9. |
- Sanchez, Sophie, et al.
(författare)
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Bone Histology Reveals a High Environmental and Metabolic Plasticity as a Successful Evolutionary Strategy in a Long-Lived Homeostatic Triassic Temnospondyl
- 2013
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Ingår i: Evolutionary biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 40:4, s. 627-647
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Tidskriftsartikel (refereegranskat)abstract
- Evolutionary stasis (long-term stability of morphology in an evolving lineage) is a pattern for which explanations are usually elusive. The Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing temnospondyl, survived for 35 million years in the Germanic Basin of Central Europe persisting throughout the dinosaur-dominated Late Triassic period. This evolutionary stasis coincides with the occurrence of this species in a wide range of habitats and environmental conditions. By the combination of palaeoecological and palaeohistological analyses, we found great ecological flexibility in G. pulcherrimus and present substantial evidence of developmental and metabolic plasticity despite the morphological stasis. We conclude that G. pulcherrimus could show the capacity to settle in water bodies too harsh or unpredictable for most other tetrapods. This would have been made possible by a unique life history strategy that involved a wide reaction norm, permitting adjustment to fluctuating conditions such as salinity and level of nutrients. Growth rate, duration of juvenile period, age at maturity, and life span were all subject to broad variation within specimens of G. pulcherrimus in one single lake and in between different lakes. In addition to providing a better understanding of fossil ecosystems, this study shows the potential of such a methodology to encourage palaeobiologists and evolutionary biologists to consider the mechanisms of variation in extant and fossil organisms by using a similar time-scope reference.
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| 10. |
- Secondi, Jean, et al.
(författare)
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Bilateral Song Convergence in a Passerine Hybrid Zone: Genetics Contribute in One Species Only
- 2011
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Ingår i: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 38:4, s. 441-452
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Forskningsöversikt (refereegranskat)abstract
- Hybridization can drive the convergence of territorial and sexual signals. However, non-genetic processes such as competition, environment matching, or cultural transmission, also generate this pattern. We investigated the effect of hybridization on song convergence between two interspecifically territorial warblers in a moving hybrid zone. We confirmed song convergence in each species. Using an AFLP-based genetic index, we detected an effect of genetics on song convergence in Hippolais polyglotta, the expanding species. Evidence was weaker for H. icterina, the receding species. In moving zones, introgression is expected to be larger in the expanding species than in the receding. Thus, the asymmetric contribution of the genetic index to convergence was consistent with expectations for genetically determined traits in moving hybrid zones, and the observed introgression pattern of AFLP markers. However, the geographical location of individuals had an effect on song variation too when genetics was accounted for, suggesting that convergence also has non-genetic explanations. We examine the possible role of alternative processes to that of hybridization and discuss their conflicting effects on reinforcement and hybrid zone dynamics.
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