RESUMO
Coexisting bisexual and unisexual populations of individuals belonging to the genus Heterocypris are found in ephemeral freshwater ponds on the island of Lampedusa (Pelagie Islands, Italy). Different reproductive modes were associated with a peculiar morphological trait: a lamella hyalina on the posterior margin of the left valve was observed in amphimictic females, a feature missing in apomictic females. In order to clarify the phylogenetic relationships among taxa with different morphological traits and reproductive modes, we used four polymorphic enzyme loci (GPI, ICD2, MPI and PGM) and mitochondrial DNA 16S ribosomal sequences. We identified three main evolutionary units that showed a combination of morphological and reproductive characteristics: (1) amphimictic females of H. barbara with a lamella hyalina, according to the typical feature of the species, and apomictic females of H. barbara without lamella that are sympatric in one temporary pond; (2) apomictic females of H. incongruens without a lamella, as typical of the species; (3) apomictic females without a lamella, living in sympatry with H. barbara, but characterised by a high genetic diversity from both H. incongruens and H. barbara. We discuss the possible origin of apomictic lineages as a result of independent transition episodes to apomixis from different sexual ancestors. Time of divergence reflected the genetic differentiation within and among multiple ancestors and different possible routes to parthenogenesis.
Assuntos
Crustáceos/classificação , Crustáceos/genética , Animais , Sequência de Bases , Crustáceos/enzimologia , Crustáceos/fisiologia , Primers do DNA/genética , DNA Mitocondrial/genética , Evolução Molecular , Feminino , Itália , Masculino , Ilhas do Mediterrâneo , Dados de Sequência Molecular , Filogenia , Reprodução/genética , Reprodução/fisiologiaRESUMO
To identify the callipyge mutation, we have resequenced 184 kb spanning the DLK1-, GTL2-, PEG11-, and MEG8-imprinted domain and have identified an A-to-G transition in a highly conserved dodecamer motif between DLK1 and GTL2. This was the only difference found between the callipyge (CLPG) allele and a phylogenetically closely related wild-type allele. We report that this SNP is in perfect association with the callipyge genotype. The demonstration that Solid Gold-the alleged founder ram of the callipyge flock-is mosaic for this SNP virtually proves the causality of this SNP in the determinism of the callipyge phenotype.
