M. J. Alves

Evolution in action through hybridisation and polyploidy in an Iberian freshwater fish: a genetic review

The Iberian minnow Leuciscus alburnoides represents a complex of diploid and polyploid forms with altered modes of reproduction. In the present paper, we review the recent data on the origin, reproductive modes, and inter-relationships of the various forms of the complex, in order to predict its evolutionary potential. The complex follows the hybrid-origin model suggested for most other asexual vertebrates. Diploid and triploid females from the southern river basins exhibit reproductive modes that cannot be conveniently placed into the categories generally recognised for these vertebrate complexes, which imply continuous shifting between forms, where genomes derived from both parental ancestors are cyclically lost, gained or replaced. Replacement of nuclear genomes allow the introduction of novel genetic material, that may compensate for the disadvantages of asexual reproduction. Contrasting with most other vertebrate complexes, L. alburnoides males are fertile and play an important role in the dynamics of the complex. Moreover, diploid hybrid males may have initiated a tetraploidization process, when a diploid clonal sperm fertilised a diploid egg. This direct route to tetraploidy by originating fish with the right constitution for normal meiosis (symmetric), may eventually lead to a new sexually reproducing polyploid species. This case-study reinforces the significance of hybridisation and polyploidy in evolution and diversification of vertebrates.

MATERNAL ANCESTRY OF THE RUTILUS ALBURNOIDES COMPLEX (TELEOSTEI, CYPRINIDAE) AS DETERMINED BY ANALYSIS OF CYTOCHROME B SEQUENCES

Cytochrome b (cyt b) sequences from specimens of the Rutilus alburnoides unisexual complex and five bisexual species were compared to examine hypotheses regarding the origin and maternal ancestry of this complex. Phylogenetic analysis revealed a monophyletic relationship among unisexuals and Leuciscus pyrenaicus, clearly identifying this species as the maternal ancestor. Considerable mtDNA diversity exists among R. alburnoides populations, with many localities exhibiting unique haplotypes. The topology recovered from analysis of cyt b variation among populations suggested that R. alburnoides is polyphyletically derived from their sympatric L. pyrenaicus populations, indicating that unisexual lineages have been generated through multiple hybridization events. Although much less abundant, R. alburnoides is present outside the range of L. pyrenaicus, suggesting that it may have dispersed from the Tejo drainage into the northern basins. In this region, Leuciscus carolitertii is most likely the sexual host for the unisexual complex.

Semi-permeable species boundaries in Iberian barbels (Barbus and Luciobarbus, Cyprinidae)

BackgroundThe evolution of species boundaries and the relative impact of selection and gene flow on genomic divergence are best studied in populations and species pairs exhibiting various levels of divergence along the speciation continuum. We studied species boundaries in Iberian barbels, Barbus and Luciobarbus, a system of populations and species spanning a wide degree of genetic relatedness, as well as geographic distribution and range overlap. We jointly analyze multiple types of molecular markers and morphological traits to gain a comprehensive perspective on the nature of species boundaries in these cyprinid fishes.ResultsIntraspecific molecular and morphological differentiation is visible among many populations. Genomes of all sympatric species studied are porous to gene flow, even if they are not sister species. Compared to their allopatric counterparts, sympatric representatives of different species share alleles and show an increase in all measures of nucleotide polymorphism (S, Hd, K, π and θ). High molecular diversity is particularly striking in L. steindachneri from the Tejo and Guadiana rivers, which co-varies with other sympatric species. Interestingly, different nuclear markers introgress across species boundaries at various levels, with distinct impacts on population trees. As such, some loci exhibit limited introgression and population trees resemble the presumed species tree, while alleles at other loci introgress more freely and population trees reflect geographic affinities and interspecific gene flow. Additionally, extent of introgression decreases with increasing genetic divergence in hybridizing species pairs.ConclusionsWe show that reproductive isolation in Iberian Barbus and Luciobarbus is not complete and species boundaries are semi-permeable to (some) gene flow, as different species (including non-sister) are exchanging genes in areas of sympatry. Our results support a speciation-with-gene-flow scenario with heterogeneous barriers to gene flow across the genome, strengthening with genetic divergence. This is consistent with observations coming from other systems and supports the notion that speciation is not instantaneous but a gradual process, during which different species are still able to exchange some genes, while selection prevents gene flow at other loci. We also provide evidence for a hybrid origin of a barbel ecotype, L. steindachneri, suggesting that ecology plays a key role in species coexistence and hybridization in Iberian barbels. This ecotype with intermediate, yet variable, molecular, morphological, trophic and ecological characteristics is the local product of introgressive hybridization of L. comizo with up to three different species (with L. bocagei in the Tejo, with L. microcephalus and L. sclateri in the Guadiana). In spite of the homogenizing effects of ongoing gene flow, species can still be discriminated using a combination of morphological and molecular markers. Iberian barbels are thus an ideal system for the study of species boundaries, since they span a wide range of genetic divergences, with diverse ecologies and degrees of sympatry.

Development of cytochrome b primers for mitotyping of barbels (Barbus spp.)

Primers were developed that allow for rapid, reliable and inexpensive screening of cytochrome b by analysis of single‐stranded conformational polymorphisms. Twenty different haplotypes were identified from six species of Iberian Barbus. These primers proved useful for population and species level studies, and could also be valuable in population genetic and phylogenetic studies of other cyprinin fishes.

ENSINO DE DANÇA EM PROGRAMAS NACIONAIS NO BRASIL E PORTUGAL

This study examines the fundamental principles of dance teaching (GEHRES, 2008) in national programs in Brazil and Portugal. In Brazil we selected the Curricular Orientations and Parameters in Physical Education and Art; in Portugal we focused on the Programs of Physical Education and the Alternative Proposal for Dance Education for the second part of Primary Education. Taking the aim of the investigation into consideration, we chose to conduct analytical philosophical research which, according to Thomas and Nelson (2002), aims at critical investigation, the study of facts and the synthesis of variables to analyze the existing material under a viable theoretical model. The investigation of the guideline documents of the two countries showed predominance of subjective proposals in both nations. However, Portugal and Brazil diverge in terms of their focuses; Portugal has an objective approach while Brazil focuses on interactionism.Licence Creative Commom Abstract: This study examines the fundamental principles of dance teaching (GEHRES, 2008) in national programs in Brazil and Portugal. In Brazil we selected the Curricular Orientations and Parameters in Physical Education and Art; in Portugal we focused on the Programs of Physical Education and the Alternative Proposal for Dance Education for the second part of Primary Education. Taking the aim of the investigation into consideration, we chose to conduct analytical philosophical research which, according to Thomas and Nelson (2002), aims at critical investigation, the study of facts and the synthesis of variables to analyze the existing material under a viable theoretical model. The investigation of the guideline documents of the two countries showed predominance of subjective proposals in both nations. However, Portugal and Brazil diverge in terms of their focuses; Portugal has an objective approach while Brazil focuses on interactionism.