Browsing by Author "Engel, C. R."
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- Analysis of sexual phenotype and prezygotic fertility in natural populations of Fucus spiralis, F. vesiculosus (Fucaceae, Phaeophyceae) and their putative hybridsPublication . Billard, E.; Serrão, Ester; Pearson, G. A.; Engel, C. R.; Destombe, C.; Valero, MyriamIn the genus Fucus, the character dioecy/hermaphroditism has undergone multiple state changes and hybridization is possible between taxa with contrasting mating systems, e.g. between the dioecious Fucus vesiculosus and the hermaphrodite F. spiralis. In the context of mating system evolution, we evaluated the potential consequences of hybridization by studying the variation in sexual phenotype and prezygotic fertility. Firstly, as a result of hybridization between the two sexual systems, gender variation may arise depending on the relative importance of genes with large versus small phenotypic effects. We thus qualitatively examined the extent of gender variation within and among individual hybrids in comparison with both parental species. Secondly, if hybridization breaks up co-adapted gene complexes, hybrid fertility may be reduced in comparison with both parental species. Therefore, we also quantified male and female prezygotic fertility in parental species and their hybrids in order to test for reduction in hybrid fitness. A total of 89 sexually mature individuals (20 F. spiralis, 40 F. vesiculosus, 10 hermaphrodite hybrids and 19 dioecious hybrids) were sampled in two geographically distant regions (France and Portugal) and six conceptacles per individual were observed. Within-individual variation was very restricted qualitatively – only one hybrid carried a conceptacle with a different sexual phenotype from the five others – as well as quantitatively. This suggests a simple genetic system for sex determination involving a few genes with major effects. In addition, analyses showed no significant decrease in hybrid fertility compared with parental species. Moreover, hybrids exhibited all sexual phenotypes, suggesting several generations of hybridization and backcrossing and, therefore, that hybrids are reproductively successful. Finally, the occurrence of sterile paraphyses in female and hermaphrodite individuals was interpreted as a relic of male function and suggests that, as in higher plants, evolution from hermaphroditism to dioecy may be the most parsimonious pathway.
- Genetic entities and mating system in hermaphroditic Fucus spiralis and its close dioecious relative F. vesiculosus (Fucaceae, Phaeophyceae)Publication . Engel, C. R.; Daguin, C.; Serrão, EsterTo date, molecular markers have not settled the question of the specific status of the closely related, but phylogenetically unresolved, brown seaweeds, hermaphroditic Fucus spiralis and dioecious Fucus vesiculosus , nor their propensity for natural hybridization.
- Genetic isolation between three closely related taxa: fucus vesiculosus, F. spiralis, and F. ceranoides (Phaophyceae)Publication . Billard, E.; Daguin, C.; Pearson, G. A.; Serrão, Ester; Engel, C. R.; Valero, MyriamAll traditional markers, both phenotypic and phylogenetic, have failed to discriminate between the taxa composing the Fucus vesiculosus L., F. spiralis L., and F. ceranoides L. species complex, particularly in Brittany (France), so we used five microsatellite markers to compare the allelic frequencies of populations of the three taxa in this region. The aim of this study was to assess whether the different populations were grouped according to their geographical location, their habitat (open coast versus estuary), or their a priori taxonomic assignment. Species-specific alleles were identified at one locus, demonstrating the utility of microsatellite markers for recognizing the three taxa in Brittany. Moreover, our results clearly support the separation of F. vesiculosus, F. spiralis, and F. ceranoides into distinct species, independently of geography. We also identified genetic differentiation between estuarine and coastal populations of F. vesiculosus.
- Implications of mating system for genetic diversity of sister algal species: Fucus spiralis and Fucus vesiculosus (Heterokontophyta, Phaeophyceae)Publication . Perrin, C.; Daguin, C.; Van De Vliet, M. S.; Engel, C. R.; Pearson, G. A.; Serrão, EsterThe implications of mating system for genetic diversity were assessed in the sister species Fucus spiralis and Fucus vesiculosus using a combination of ten microsatellite markers. Five new microsatellite markers specific for F. spiralis were developed in order to increase marker resolution and complement the results (i.e. mating system and genetic diversity extended to a larger geographic scale) acquired using five microsatellite loci previously developed from a mixed fucoid seaweed DNA library that excluded F. spiralis. Low genetic diversities observed at the population and species level in F. spiralis using the five new F. spiralis-specific loci described here were consistent with the results obtained previously with non-specific microsatellite loci. Results revealed that selfing is characteristic in F. spiralis across its latitudinal distribution along the Iberian and French Atlantic coasts. Higher levels of within-population genetic diversity were observed in the outcrossing species F. vesiculosus, decreasing towards the southern distributional range of the species. Some cases of significant biparental inbreeding in this species are indicative of short gamete dispersal or mating of spatially or temporally structured populations. In contrast to within-population diversities, higher total genetic diversity among populations was observed in the hermaphroditic species in comparison to the dioecious F. vesiculosus.
- Isolation and cross-species amplification of microsatellite loci from the fucoid seaweeds fucus vesiculosus, f. serratus and Ascophyllum nodosum (heterokontophyta, fucaceae)Publication . Engel, C. R.; Brawley, S. H.; Edwards, K. J.; Serrão, EsterThe Fucaceae is a family of brown seaweeds that dominate and frequently co-occur on North Atlantic rocky shores. We developed nine polymorphic microsatellite markers for the fucoid seaweeds Fucus vesiculosus, F. serratus and Ascophyllum nodosum using a combined, enriched library. Six of these loci were polymorphic in at least two species, showing from two to eight alleles with heterozygosities ranging from 0.41 to 0.85. Loci were also tested on F. spiralis, revealing five polymorphic microsatellite loci in this species.
- When is a hybrid a hybrid? A counter-reply to Wallace et al.Publication . Engel, C. R.; Daguin, C.; Serrão, EsterIn a reply to a brief citation of their paper (Wallace et al . 2004), Wallace et al . (2006) re-analyse their data using the same methods as we did (Engel et al . 2005) to conclude again that an ecad of the brown alga Fucus sp., which occurs only in a particular type of habitat, was a hybrid. While we wholly agree that the ecad individuals (called ‘muscoides-like’) may be putative hybrids, their conclusions were — and remain — confounded with other, alternative explanations. Here, in response to their Reply (Wallace et al . 2006), we wish to clarify our reservations more fully and offer some reflections on identifying hybrids in species complexes.