| 1. |
- Cramer, Emily R. A., et al.
(författare)
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Testing a post-copulatory pre-zygotic reproductive barrier in a passerine species pair
- 2014
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 1432-0762 .- 0340-5443. ; 68:7, s. 1133-1144
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Tidskriftsartikel (refereegranskat)abstract
- Sexual selection may drive speciation, but most research focuses on pre-copulatory sexual selection, overlooking post-copulatory processes. Post-copulatory sexual selection in allopatric populations could drive divergence in post-copulatory pre-zygotic (PCPZ) phenotypes, limiting gene flow upon secondary contact. Here, we performed in vitro experiments examining one potential PCPZ barrier between two closely related passerine species, house sparrows (Passer domesticus) and Spanish sparrows (Passer hispaniolensis). In birds, crossing in the vagina may be particularly challenging for sperm, so we tested the effect of female reproductive tract fluids on sperm swimming speed and motility. If a PCPZ barrier exists at this stage of the fertilization process, heterospecific female fluids are predicted to reduce sperm swimming speed or motility relative to conspecific female fluid. We found that house sparrow female fluids affected the two species' sperm asymmetrically, depending on the control sperm velocity and male species. Overall, however, sperm performed equally in conspecific and heterospecific female fluids, and the species had similar sperm morphology and sperm swimming performance. Low divergence in PCPZ phenotypes between species, perhaps because post-copulatory sexual selection is stabilizing or only moderately strong in these taxa, may be insufficient to cause an overall PCPZ barrier. Reinforcement may be unlikely to drive PCPZ barriers for this species pair, because relatively effective pre-copulatory barriers exist between the species, and because hybrids can be quite successful. Testing the role of PCPZ barriers in birds with more divergent PCPZ phenotypes will improve our understanding of speciation in passerines.
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| 2. |
- Cuevas, Angelica, et al.
(författare)
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Predictors of genomic differentiation within a hybrid taxon
- 2022
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Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 18:2
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Tidskriftsartikel (refereegranskat)abstract
- Hybridization is increasingly recognized as an important evolutionary force. Novel genetic methods now enable us to address how the genomes of parental species are combined in hybrid lineages. However, we still do not know the relative importance of admixed proportions, genome architecture and local selection in shaping hybrid genomes. Here, we take advantage of the genetically divergent island populations of Italian sparrow on Crete, Corsica and Sicily to investigate the predictors of genomic variation within a hybrid taxon. We test if differentiation is affected by recombination rate, selection, or variation in ancestry proportions. We find that the relationship between recombination rate and differentiation is less pronounced within hybrid lineages than between the parent species, as expected if purging of minor parent ancestry in low recombination regions reduces the variation available for differentiation. In addition, we find that differentiation between islands is correlated with differences in signatures of selection in two out of three comparisons. Signatures of selection within islands are correlated across all islands, suggesting that shared selection may mould genomic differentiation. The best predictor of strong differentiation within islands is the degree of differentiation from house sparrow, and hence loci with Spanish sparrow ancestry may vary more freely. Jointly, this suggests that constraints and selection interact in shaping the genomic landscape of differentiation in this hybrid species.
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| 3. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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Contemporary parallel diversification, antipredator adaptations and phenotypic integration in an aquatic isopod.
- 2009
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:7
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Tidskriftsartikel (refereegranskat)abstract
- It is increasingly being recognized that predation can be a strong diversifying agent promoting ecological divergence. Adaptations against different predatory regimes can emerge over short periods of time and include many different traits. We studied antipredator adaptations in two ecotypes of an isopod (Asellus aquaticus) that have, diverged in parallel in two Swedish lakes over the last two decades. We quantified differences in escape speed, morphology and behavior for isopods from different ecotypes present in these lakes. Isopods from the source habitat (reed) coexist with mainly invertebrate predators. They are more stream-profiled and have higher escape speeds than isopods in the newly colonized stonewort habitat, which has higher density of fish predators. Stonewort isopods also show more cautious behaviors and had higher levels of phenotypic integration between coloration and morphological traits than the reed isopods. Colonization of a novel habitat with a different predation regime has thus strengthened the correlations between pigmentation and morphology and weakened escape performance. The strong signature of parallelism for these phenotypic traits indicates that divergence is likely to be adaptive and is likely to have been driven by differences in predatory regimes. Furthermore, our results indicate that physical performance, behavior and morphology can change rapidly and in concert as new habitats are colonized.
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| 4. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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Evolution and stability of the G-matrix during the colonization of a novel environment.
- 2011
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 24:6, s. 1363-1373
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Tidskriftsartikel (refereegranskat)abstract
- Populations that undergo a process of rapid evolution present excellent opportunities to investigate the mechanisms driving or restraining adaptive divergence. The genetic variance-covariance matrix (G) is often considered to constrain adaptation but little is known about its potential to evolve during phenotypic divergence. We compared the G-matrices of ancestral and recently established ecotype populations of an aquatic isopod (Asellus aquaticus) that have diverged in parallel in two south Swedish lakes. Phenotypic changes after colonization involved a reduction in overall size, lost pigmentation and changes in shape. Comparisons between G-matrices reveal close similarity within the same ecotype from different lakes but some degree of differentiation among ecotypes. Phenotypic divergence has apparently not been much influenced by the orientation of G. Additive genetic variation in the newly colonized habitats has also decreased substantially. This suggests that a process of adaptation from standing genetic variation has occurred and has probably facilitated phenotypic divergence.
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| 5. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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Experimental evidence for ovarian hypofunction in sparrow hybrids
- 2016
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Ingår i: Avian Research. - : Elsevier BV. - 2053-7166. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPostzygotic isolation in the form of reduced viability and/or fertility of hybrids may help maintain species boundaries in the face of interspecific gene flow. Past hybridization events between house sparrows (Passer domesticus) and Spanish sparrows (P. hispaniolensis) have given rise to a homoploid hybrid species, the Italian sparrow (P. italiae). Although genetic incompatibilities are known to isolate these three species, the biological consequences of these incompatibilities are still unknown in early generation hybrids.MethodsWe investigated whether F1 hybrids between house and Spanish sparrows experience reduced viability or fertility. More specifically, we generated hybrids through controlled crosses in aviaries, and compared ovaries of female hybrids with female of pure-species sparrows.ResultsWe found that overall, hybrid ovaries were underdeveloped and that half of all female hybrids exhibited symptoms of ovarian hypofunction (ovarian atrophy and complete absence of developed follicles).ConclusionsFertility in hybrids is a common consequence or post-zygotic barriers between species. We discuss these results in light of previous findings on genetic incompatibilities between the parent species and the potential role of incompatibilities in hybrid speciation, a rare evolutionary process in birds.
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| 6. |
- Eroukhmanoff, Fabrice
(författare)
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Just How Much is the G-matrix Actually Constraining Adaptation?
- 2009
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Ingår i: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 36:3, s. 323-326
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Forskningsöversikt (refereegranskat)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.
(författare)
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Patterns of Phenotypic Divergence in Wing Covariance Structure of Calopterygid Damselflies
- 2009
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Ingår i: Evolutionary Biology. - : Springer Science and Business Media LLC. - 0071-3260 .- 1934-2845. ; 36:2, s. 214-224
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Forskningsöversikt (refereegranskat)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. |
- 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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| 9. |
- Eroukhmanoff, Fabrice, et al.
(författare)
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Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F-ST-Q(ST) analysis
- 2009
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Ingår i: Molecular Ecology. - Oxford, United Kingdom : Wiley-Blackwell. - 0962-1083 .- 1365-294X. ; 18:23, s. 4912-4923
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Tidskriftsartikel (refereegranskat)abstract
- Divergent natural selection is often thought to be the principal factor driving phenotypic differentiation between populations. We studied two ecotypes of the aquatic isopod Asellus aquaticus which have diverged in parallel in several Swedish lakes. In these lakes, isopods from reed belts along the shores colonized new stonewort stands in the centre of the lakes and rapid phenotypic changes in size and pigmentation followed after colonization. We investigated if selection was likely to be responsible for these observed phenotypic changes using indirect inferences of selection (F-ST-Q(ST) analysis). Average Q(ST) for seven quantitative traits were higher than the average F-ST between ecotypes for putatively neutral markers (AFLPs). This suggests that divergent natural selection has played an important role during this rapid diversification. In contrast, the average Q(ST) between the different reed ecotype populations was not significantly different from the mean F-ST. Genetic drift could therefore not be excluded as an explanation for the minor differences between allopatric populations inhabiting the same source habitat. We complemented this traditional F-ST-Q(ST) approach by comparing the F-ST distributions across all loci (n = 67-71) with the Q(ST) for each of the seven traits. This analysis revealed that pigmentation traits had diverged to a greater extent and at higher evolutionary rates than size-related morphological traits. In conclusion, this extended and detailed type of F-ST-Q(ST) analysis provides a powerful method to infer adaptive phenotypic divergence between populations. However, indirect inferences about the operation of divergent selection should be analyzed on a per-trait basis and complemented with detailed ecological information.
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| 10. |
- Eroukhmanoff, Fabrice
(författare)
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The Interplay Between Selection And Constraints On Adaptive Divergence And Phenotypic Evolution
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Under natural or sexual selection, individuals with advantageous traits or combinations of traits will be more successful than their peers at surviving and/or reproducing. Provided these traits are heritable, meaning that they have a genetic basis, the traits combinations which are selected for, will increase in frequency in the population. When selection is intense and persistent, adaptive traits may become ubiquitous in the population, and we may then say that this population has evolved and become adapted. However, this process might not always occur rapidly. This is because adaptive evolution occurs only when the individuals of a population are diverse in their trait combinations and when there is a significant amount of genetic variation for the trait(s) upon which selection is acting. However, if the adaptive optimum of a combination of traits is situated in a direction where there is little variation available, adaptation will be slowed down, and we will say it is constrained. This is precisely what I attempted to study in this thesis. The outcome of the interplay between selection and constraints might lead to evolution, to divergence between populations, and finally to the emergence of new species and biodiversity. By using different statistical techniques used in quantitative genetics or geometric morphometrics, combined with behavioral and breeding experiments, I tried to draw some conclusions on the role of constraints both in the early stages of adaptation and divergence (using isopod lake populations as a model system) and in the latter stages of divergence and speciation (using damselfly species as model organisms). My main conclusions are that in the context of strong divergent selection, constraints may be overcome and adaptation may proceed, provided that gene flow between populations is restrained.
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