| 1. |
- Abbott, Jessica, et al.
(författare)
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Phenotypic and genetic variation in emergence and development time of a trimorphic damselfly
- 2005
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 18:6, s. 1464-1470
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Tidskriftsartikel (refereegranskat)abstract
- Although colour polymorphisms in adult organisms of many taxa are often adaptive in the context of sexual selection or predation, genetic correlations between colour and other phenotypic traits expressed early in ontogeny could also play an important role in polymorphic systems. We studied phenotypic and genetic variation in development time among female colour morphs in the polymorphic damselfly Ischnura elegans in the field and by raising larvae in a common laboratory environment. In the field, the three different female morphs emerged at different times. Among laboratory-raised families, we found evidence of a significant correlation between maternal morph and larval development time in both sexes. This suggests that the phenotypic correlation between morph and emergence time in the field has a parallel in a genetic correlation between maternal colour and offspring development time. Maternal colour morph frequencies could thus potentially change as correlated responses to selection on larval emergence dates. The similar genetic correlation in male offspring suggests that sex-limitation in this system is incomplete, which may lead to an ontogenetic sexual conflict between selection for early male emergence (protandry) and emergence times associated with maternal morph.
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| 2. |
- Andersson, Stefan, et al.
(författare)
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Paternal effects on seed germination: a barrier to the genetic assimilation of an endemic plant taxon?
- 2008
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 21:5, s. 1408-1417
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Tidskriftsartikel (refereegranskat)abstract
- We used a crossing experiment to investigate post-zygotic barriers that might limit introgression between a pair of closely-related, gynodioecious plant species - the widespread weed Silene vulgaris and the local Swedish endemic S. uniflora ssp. petraea. The study not only considered the effects of hybridization on conventionally-used (primary) fitness components such as seed set and progeny survival, but also provided a test for the effects of interspecific hybridization on characters with more subtle or habitat-specific effects on fitness. We detected highly significant paternal effects on seed germination properties, with the germination characteristics of hybrid seed resembling those of the species that served as the pollen donor. These paternal effects on germination represent a potentially strong barrier to interspecific introgression in the two species' natural habitats, where an inappropriate germination response in the habitat of the maternal parent may lead to the failure of seedling establishment. Interspecific crosses had weak or variable effects on progeny survival, flowering and sex ratio, but these effects could not be interpreted in terms of barriers to introgression. Our results indicate that nuclear restorers in S. vulgaris have the capacity to suppress cytoplasmic male-sterility genes in its endemic congener.
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| 3. |
- Bengtsson, Bengt Olle, et al.
(författare)
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The balance between sexual and asexual reproduction in plants living in variable environments
- 2000
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 13:3, s. 415-422
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Tidskriftsartikel (refereegranskat)abstract
- The balance between sexual and asexual propagule production is studied in an evolutionary model where plants produce the two kinds of propagules in genetically determined proportions. The male function of plants producing asexual propagules can be varied, and the sexual and asexual propagules carry different probabilities to turn into new reproductive individuals. These fitnesses may vary over years. The evolution of the population’s reproductive system is studied assuming modifier alleles with small effects. In this setting a balanced, mixed reproductive system can evolve, but only if the difference in fitness between the sexual and asexual propagules varies over years. When the two kinds of propagules are very similar to each other, as is often the case with sexual and asexual seed formation, evolution will tend towards a state dominated by the one or the other reproductive system.
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| 4. |
- Bilde, Trine, et al.
(författare)
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Survival benefits select for group living in a social spider despite reproductive costs
- 2007
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 20:6, s. 2412-2426
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The benefits of group living in such systems should therefore be substantial. We investigated the effect of group size on fitness components of reproduction and survival in the social spider Stegodyphus dumicola in two populations in Namibia. In both populations, the major benefit of group living was improved survival of colonies and late-instar juveniles with increasing colony size. By contrast, female fecundity, female body size and early juvenile survival decreased with increasing group size. Mean individual fitness, estimated as LRS and calculated from five components of reproduction and survival, was maximized for intermediate- to large-sized colonies. Group living in these spiders thus entails a net reproductive cost, presumably because of an increase in intra-colony competition with group size. This cost is traded off against survival benefits at the colony level, which appear to be the major factor favouring group living. In the field, many colonies occur at smaller size than expected from the fitness curve, suggesting ecological or life history constraints on colony persistence which results in a transient population of relatively small colonies.
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| 5. |
- Calsbeek, B., et al.
(författare)
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Multivariate phenotypes and the potential for alternative phenotypic optima in wall lizard (Podarcis muralis) ventral colour morphs
- 2010
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 23:6, s. 1138-1147
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Tidskriftsartikel (refereegranskat)abstract
- A major goal in evolutionary biology is to determine how phenotypic variation arises and is maintained in natural populations. Recent studies examining the morphological, physiological and behavioural differences among discrete colour morphotypes (morphs) have revealed several mechanisms that maintain discrete variation within populations, including frequency-dependence, density-dependence and correlational selection. For example, trade-offs over resource allocation to morphological, physiological and behavioural traits can drive correlational selection for morph-specific phenotypic optima. Here, we describe a ventral colour polymorphism in the wall lizard (Podarcis muralis) and test the hypothesis that morphs differ along multivariate axes defined by trade-offs in morphological, physiological, and immunological traits. We show that ventral colour is a discrete trait and that morphs differ in body size, prevalence of infection by parasites and infection intensity. We also find that morphs differ along multivariate phenotypic axes and experience different multivariate selection pressures. Our results suggest that multivariate selection pressures may favour alternative optimal morph-specific phenotypes in P. muralis.
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| 6. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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Phenotypic integration and conserved covariance structure in calopterygid damselflies.
- 2008
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 21:2, s. 514-526
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Tidskriftsartikel (refereegranskat)abstract
- By comparing the phenotypic (P) variance-covariance matrices between closely related taxa or conspecific populations, one can study the outcome of the interplay between selection and developmental constraints in phenotypic evolution. Shared patterns of phenotypic integration are also of interest and might result from similarities in either selection or developmental pathways. We compared P-matrices and phenotypic integration indices between populations and species of the damselfly genus Calopteryx. P(max)-comparisons between parapatric C. splendens populations revealed stronger conserved phenotypic covariance structure than P(max)-comparisons between species, suggesting that divergence in its early stages proceeds along phenotypic lines of least resistance. Within- and among-population correlations in C. splendens were highly concordant, in further support of initial divergence along P(max). Despite some similarities in overall phenotypic integration between C. splendens and C. virgo, these two species only had several P-matrix eigenvectors in common, indicating that after reproductive isolation, divergence has proceeded against P(max).
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| 7. |
- Hargeby, Anders, et al.
(författare)
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Is size-assortative mating important for rapid pigment differentiation in a freshwater isopod?
- 2006
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 19:6, s. 1911-1919
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Tidskriftsartikel (refereegranskat)abstract
- Identifying mechanisms behind assortative mating is central to the understanding of ecological divergence and speciation. Recent studies show that populations of the freshwater isopod Asellus aquaticus can rapidly become locally differentiated when submerged Chara vegetation expands in lakes. In the novel Chara habitat, isopods have become lighter pigmented and smaller than in ancestral reed stands. In this study, we used a laboratory multiple-choice experiment to investigate assortative mating as a possible prezygotic reproductive barrier between Chara and reed isopods. Mating was assortative when Chara isopods were experimentally mixed with isopods from an adjacent reed site with large-size individuals, suggesting a partial prezygotic reproductive barrier. No deviation from random mating could, however, be detected when Chara isopods were mixed with smaller sized isopods from another reed site. In both experiments, assortative mating was apparently based on size, as Chara isopods were larger and reed isopods smaller in mixed pairs than in assortative pairs. Pigmentation did not have any clear influence on mating. We suggest that divergence in pigmentation evolved through natural selection in conjunction with size-assortative mating indirectly causing assortative mating between Chara and reed isopods. Size-assortative mating is likely a by-product of natural selection, but its importance may hypothetically be transient, if selection erodes the correlation between pigmentation and size over time.
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| 8. |
- Hargeby, Anders, et al.
(författare)
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Locally differentiated cryptic pigmentation in the freshwater isopod Asellus aquaticus
- 2005
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 18:3, s. 713-721
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Tidskriftsartikel (refereegranskat)abstract
- A repeated pattern of background colour matching in animals is an indication that pigmentation may be cryptic. Here, we examine the relationship between pigmentation of the freshwater isopod Asellus aquaticus and background darkness in 29 lakes, wetlands and ponds in Southern Sweden. The results show that Asellus pigmentation was correlated with substrate darkness across all localities. In seven localities, in which two contrasting substrate types were noted, Asellus populations were differentiated with respect to pigmentation. These findings thus provide phenomenological support for cryptic pigmentation in Asellus. Pigmentation generally increased with body size, but the relationship between pigmentation and size differed among localities, possibly as a result of differences in correlational selection on pigmentation and size. Selection thus appears to have resulted in local differentiation over a small spatial scale, even within lakes and wetlands. This differentiation is a likely cause behind elevated phenotype variation noted in localities with two substrate types, suggesting that habitat heterogeneity promotes genetic diversity.
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| 9. |
- Jakobsson, Mattias, et al.
(författare)
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The evolutionary history of the common chloroplast genome of Arabidopsis thaliana and A. suecica.
- 2007
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 20:1, s. 104-121
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Tidskriftsartikel (refereegranskat)abstract
- The evolutionary history of the common chloroplast (cp) genome of the allotetraploid Arabidopsis suecica and its maternal parent A. thaliana was investigated by sequencing 50 fragments of cpDNA, resulting in 98 polymorphic sites. The variation in the A. suecica sample was small, in contrast to that of the A. thaliana sample. The time to the most recent common ancestor (T-MRCA) of the A. suecica cp genome alone was estimated to be about one 37th of the T-MRCA of both the A. thaliana and A. suecica cp genomes. This corresponds to A. suecica having a MRCA between 10 000 and 50 000 years ago, suggesting that the entire species originated during, or before, this period of time, although the estimates are sensitive to assumptions made about population size and mutation rate. The data was also consistent with the hypothesis of A. suecica being of single origin. Isolation-by-distance and population structure in A. thaliana depended upon the geographical scale analysed; isolation-by-distance was found to be weak on the global scale but locally pronounced. Within the genealogical cp tree of A. thaliana, there were indications that the root of the A. suecica species is located among accessions of A. thaliana that come primarily from central Europe. Selective neutrality of the cp genome could not be rejected, despite the fact that it contains several completely linked protein-coding genes.
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| 10. |
- Karlsson, Kristina, et al.
(författare)
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Parallel divergence in mate guarding behaviour following colonization of a novel habitat.
- 2010
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 23, s. 2540-2549
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Tidskriftsartikel (refereegranskat)abstract
- Ecological factors can have profound effects on mating system and mating behaviour. We investigated the effect of altered ecological conditions, following colonization of a novel habitat, on precopulatory mate guarding in a freshwater isopod (Asellus aquaticus). This isopod occurs in two different ecotypes, which coexist within several different lakes in Sweden but which utilize different habitats. These ecotypes have rapidly (ca. 40 generations) diverged in parallel among lakes in several phenotypic characters, presumably as a response to different predatory pressures. Here, we demonstrate that also mate guarding characteristics have diverged in parallel between the ecotypes in different lakes. This is one of the few studies reporting parallel evolution of mating behaviour. Furthermore, our results also indicate a potential sexual conflict, as the length of mate guarding appears to lower components of female fitness. We discuss how novel environments might have strong and rapid effects on mate guarding dynamics and mating behaviour.
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