| 1. |
- 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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| 2. |
- Richardson, David, et al.
(författare)
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Sex-specific associative learning cues and inclusive fitness benefits in the Seychelles warbler
- 2003
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 16:5, s. 854-861
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Tidskriftsartikel (refereegranskat)abstract
- In cooperative, breeding vertebrates, indirect fitness benefits would be maximized by subordinates that accurately assess their relatedness to group offspring and preferentially help more closely related kin. In the Seychelles warbler (Acrocephalus sechellensis), we found a positive relationship between subordinate-nestling kinship (determined using microsatellite marker genotypes) and provisioning rates, but only for female subordinates. Female subordinates that helped were significantly more related to the nestlings than were nonhelpers, and the decision to help appears to be based on associative learning cues. High levels of female infidelity means that subordinates cannot trust their legitimacy through the male line, consequently they appear to use the continued presence of the primary female, but not the primary male, as a reliable cue to determine when to feed nestlings. By using effective discrimination, female subordinates are able to maximize the indirect benefits gained within. a cooperative breeding system otherwise driven primarily by direct breeding benefits.
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| 3. |
- Svensson, Erik, et al.
(författare)
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Mechanistic and experimental analysis of condition and reproduction in a polymorphic lizard
- 2002
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 15:6, s. 1034-1047
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Tidskriftsartikel (refereegranskat)abstract
- The importance of genetic and environmental variation in condition in shaping evolutionary trade-offs have recently been subject to much theoretical discussion, but is very difficult to investigate empirically in most field-based systems. We present the results from mechanistic experimental manipulations of reproductive investment and condition in two female colour morphs (orange and yellow) of side-blotched lizards (Uta stansburiana). We investigated the interactions between throat colour morphs, condition, local social environment and female survival using path-analysis. Using follice-ablation experiments, we show that large clutch size has a negative effect on field survival among yellow females, and that this effect is partly mediated by immunosuppressive effects of large clutches. In orange females these effects were less pronounced, and there was a negative survival effect of strong antibody responses. Hence, we experimentally confirmed our previous findings of correlational selection between female morphotype and immunocompetence, an important condition trait. Manipulation of corticosterone revealed multiple (pleiotropic) direct and indirect effects of this hormone on both condition and reproductive traits. We argue that interaction effects (e.g. between local environments and genotypes) could explain a substantial fraction of variation in condition and reproduction in natural populations. Increased attention to such interaction effects and their fitness consequences will provide novel insights in field studies of selection and reproductive allocation.
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| 4. |
- Waldmann, P, et al.
(författare)
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Comparison of genetic (co)variance matrices within and between Scabiosa canescens and S-columbaria
- 2000
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 13:5, s. 826-835
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Tidskriftsartikel (refereegranskat)abstract
- In the current study, we used bootstrap analyses and the common principal component (CPC) method of Flury (1988) to estimate and compare the G-matrix of Scabiosa columbaria and S. canescens populations. We found three major patterns in the G-matrices: (i) the magnitude of the (co)variances was more variable among characters than among populations, (ii) different populations showed high (co)variance for different characters, and (iii) there was a tendency for S. canescens to have higher genetic (co)variances than S. columbaria. The hypothesis of equal G-matrices was rejected in all comparisons and there was no evidence that the matrices differed by a proportional constant in any of the analyses. The two 'species matrices' were found to be unrelated, both for raw data and data standardized over populations, and there was significant between-population variation in the G-matrix in both species. Populations of S. canescens showed conservation of structure (principal components) in their G-matrices, contrasting with the lack of common structure among the S. columbaria matrices. Given these observations and the results from previous studies, we propose that selection may be responsible for some of the variation between the G-matrices, at least in S. columbaria and at the between-species level.
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| 5. |
- Bengtsson, Bengt Olle
(författare)
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Genetic variation in organisms with sexual and asexual reproduction
- 2003
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 16:2, s. 189-199
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Tidskriftsartikel (refereegranskat)abstract
- The genetic variation in a partially asexual organism is investigated by two models suited for different time scales. Only selectively neutral variation is considered. Model 1 shows, by the use of a coalescence argument, that three sexually derived individuals per generation are sufficient to give a population the same pattern of allelic variation as found in fully sexually reproducing organisms. With less than one sexual event every third generation, the characteristic pattern expected for asexual organisms appear, with strong allelic divergence between the gene copies in individuals. At intermediary levels of sexuality, a complex situation reigns. The pair-wise allelic divergence under partial sexuality exceeds, however, always the corresponding value under full sexuality. These results apply to large populations with stable reproductive systems. In a more general framework, Model 2 shows that a small number of sexual individuals per generation is sufficient to make an apparently asexual population highly genotypically variable. The time scale in terms of generations needed to produce this effect is given by the population size and the inverse of the rate of sexuality.
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| 6. |
- Ceplitis, Alf, et al.
(författare)
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Genetic variation, disequilibrium and natural selection on reproductive traits in Allium vineale
- 2004
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 17:2, s. 302-311
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Tidskriftsartikel (refereegranskat)abstract
- Bulbils and seeds collected from Allium vineale plants from natural populations were grown under uniform conditions. The bulbil-derived offspring represented the parental generation, whereas the seed-derived offspring represented the sexually produced offspring generation. Molecular markers were used to identify maternal genets. Variation in traits determining the allocation to sexual and asexual reproduction was partitioned among genets and ramet families in the parental and offspring generations. From observations of a release of genetic variation and slippage in the mean phenotype in the offspring generation, we inferred that there exists extensive genetic disequilibrium for reproductive traits in A. vineale populations, that most of the genetic variance is because of dominance effects, and that natural selection favours a reduced allocation to sexual reproduction. No genetic correlation between sexual and asexual allocation traits was found. We discuss the implications of these results with respect to the evolution of a mixed reproductive system in A. vineale.
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| 7. |
- Comendant, T, et al.
(författare)
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Social competition, corticosterone and survival in female lizard morphs
- 2003
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 16:5, s. 948-955
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Tidskriftsartikel (refereegranskat)abstract
- We examined the selective consequences of variation in behaviour and endocrine physiology in two female throat-colour morphs of the lizard, Uta stansburiana in the wild. Female morphs differed in home-range distribution patterns and corticosterone levels in relation to the density and frequency of their female neighbours. Levels of plasma corticosterone of yellow-throated females increased with increased density of both morphs. in contrast, orange-throated females had reduced levels of corticosterone in response to increased density of orange females. Additionally, females with lower corticosterone survived poorly, suggesting that social interactions and high local densities of orange females may be potentially costly for orange females. These results are consistent with decreased fitness effects and suppression of immune function previously reported for orange female morphs surrounded by more orange neighbours. These correlations, in conjunction with previous work in this system, indicate that corticosterone is likely to be an important physiological mechanism regulating female fitness in nature.
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| 8. |
- Friberg, Urban, et al.
(författare)
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Fitness effects of female mate choice : preferred males are detrimental for Drosophila melanogaster females
- 2003
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Ingår i: Journal of Evolutionary Biology. - : John Wiley & Sons. - 1010-061X .- 1420-9101. ; 16, s. 797-811
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of female mate choice, broadly defined to include any female behaviour or morphology which biases matings towards certain male phenotypes, is traditionally thought to result from direct or indirect benefits which females acquire when mating with preferred males. In contrast, new models have shown that female mate choice can be generated by sexual conflict, where preferred males may cause a fitness depression in females. Several studies have shown that female Drosophila melanogaster bias matings towards large males. Here, we use male size as a proxy for male attractiveness and test how female fitness is affected by reproducing with large or small males, under two different male densities. Females housed with large males had reduced lifespan and aged at an accelerated rate compared with females housed with small males, and increased male density depressed female fitness further. These fitness differences were due to effects on several different fitness components. Female fitness covaried negatively with male courtship rate, which suggests a cost of courtship. Mating rate increased with male size, whereas female fitness peaked at an intermediate mating rate. Our results suggest that female mate choice in D. melanogaster is, at least in part, a by-product of sexual conflict over the mating rate.
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| 9. |
- Helbig, AJ, et al.
(författare)
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Male-biased gene flow across an avian hybrid zone: evidence from mitochondrial and microsatellite DNA
- 2001
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 14:2, s. 277-287
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Tidskriftsartikel (refereegranskat)abstract
- Mating pattern and gene flow were studied in the contact zone between two morphologically very similar Chiffchaff taxa (Phylloscopus collybita, P. brehmii) in SW France and northern Spain. Mating was assortative in brehmii, but not in collybita. Mixed matings were strongly asymmetric (excess of callybita male x brehmii female pairs), but did produce viable offspring in some cases. Sequence divergence of the mitochondrial cytochrome b gene was 4.6%; Haplotypes segregated significantly with phenotype (only five 'mismatches' among 94 individuals), demonstrating that mitochondrial gene flow was very restricted. The estimated proportion of F-1 hybrids in the reproductive population was significantly lower than expected under a closed population model, indicating strong selection against hybrids. Genetic typing of 101 individuals at four microsatellite loci also showed significant population differentiation, but nuclear gene flow was estimated to be 75 times higher than mitochondrial gene flow. This strong discrepancy is probably due to unisexual hybrid sterility (Haldane's rule). Thus, there is a strong, but incomplete, reproductive barrier between these taxa.
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| 10. |
- Säll, T., et al.
(författare)
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Chloroplast DNA indicates a single origin of the allotetraploid Arabidopsis suecica
- 2003
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Ingår i: Journal of Evolutionary Biology. - : John Wiley & Sons Inc.. - 1010-061X .- 1420-9101. ; 16:5, s. 1019-1029
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Tidskriftsartikel (refereegranskat)abstract
- DNA sequencing was performed on up to 12 chloroplast DNA regions [giving a total of 4288 base pairs (bp) in length] from the allopolyploid Arabidopsis suecica (48 accessions) and its two parental species, A. thaliana (25 accessions) and A. arenosa (seven accessions). Arabidopsis suecica was identical to A. thaliana at all 93 sites where A. thaliana and A. arenosa differed, thus showing that A. thaliana is the maternal parent of A. suecica. Under the assumption that A. thaliana and A. arenosa separated 5 million years ago, we estimated a substitution rate of 2.9 x 10(-9) per site per year in noncoding single copy sequence. Within A. thaliana we found 12 substitution (single bp) and eight insertion/deletion (indel) polymorphisms, separating the 25 accessions into 15 haplotypes. Eight of the A. thaliana accessions from central Sweden formed one cluster, which was separated from a cluster consisting of central European and extreme southern Swedish accessions. This latter cluster also included the A. suecica accessions, which were all identical except for one 5 bp indel. We interpret this low level of variation as a strong indication that A. suecica effectively has a single origin, which we dated at 20 000 years ago or more.
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