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Introgressive hybridization in Iberian cyprinid fishes:a cytogenomic approach to homoploid Leuciscinae

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Resumo:Hybridization is currently a well-recognized process amongst animals responsible for biodiversity, evolution and speciation processes while defying most species concepts. Hybridization is prevalent among fishes, particularly cyprinids, which therefore constitute good models of study (1) to access general patterns of genomic variation, (2) to identify the genetic basis and the evolutionary processes behind adaptation and speciation in the wild, (3) working at different levels, from genome-wide to large geographic ranges and multiple gradients of selection. Considering that hybrids are usually characterized by genome instability and restructuring, the aim of this dissertation was to understand some processes of genome dynamics while also characterizing natural homoploid hybrids between Achondrostoma oligolepis and either Pseudochondrostoma duriense or its sister-species P. polylepis, mainly by means of cytogenomics integrated with morphologic and genetic data sets. Molecular probes included ribosomal DNAs, whole genomic DNAs, highly-moderately repetitive DNA fraction (C0t-1 DNA), retroelement Rex3, and telomeric (TTAGGG)n repeats, used to characterize nine Iberian species of Chondrostoma s.l. and the aforementioned hybrids using FISH, CGH and GISH procedures. This investigation provided new data on independent hybrid zones helping to better understand these not-so-highly conservative karyotypes as previously considered, their differentiation within the subfamily Leuciscinae, the interacting genomes in the hybrid compositions, and their post-hybridization dynamics and rapid reorganization. But many questions, including new ones, remain unanswered, namely, hybrids’ fitness in different environments, meiotic behaviour of hybrid heterokaryotypes, modes of inheritance and dosage compensation of diverging loci from each parent; as well as continuing to refine karyotype differentiation against a virtually constant macrostructure in highly flexible genomes. In summary, the hybrid fish systems that occur in the Iberian Peninsula – homoploid or polyploid – are promising regarding unresolved questions related to genome composition, plasticity and dynamics, and to evolutionary relevant processes like hybridization, introgression, adaptation or speciation, amongst many other biologically relevant subjects.
Autores principais:Pereira, Carla Sofia Alves
Assunto:Ciprinídeos - Península Ibérica Citogenética Hibridação Teses de doutoramento - 2013
Ano:2013
País:Portugal
Tipo de documento:tese de doutoramento
Tipo de acesso:acesso aberto
Instituição associada:Universidade de Lisboa
Idioma:inglês
Origem:Repositório da Universidade de Lisboa

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