Alike but different : the evolution of the Tubifex tubifex species complex (Annelida, Clitellata) through polyploidization
Articolo
Data di Pubblicazione:
2014
Citazione:
Alike but different : the evolution of the Tubifex tubifex species complex (Annelida, Clitellata) through polyploidization / R. Marotta, A. Crottini, E. Raimondi, C. Fondello, M. Ferraguti. - In: BMC EVOLUTIONARY BIOLOGY. - ISSN 1471-2148. - 14:1(2014), pp. 73.1-73.14. [10.1186/1471-2148-14-73]
Abstract:
Tubifex tubifex is a widespread annelid characterized by considerable variability in its
taxonomic characteristics and by a mixed reproductive strategy, with both parthenogenesis
and biparental reproduction. In a molecular phylogenetic analysis, we detected substantial
genetic variability among sympatric Tubifex spp. from the Lambro River (Milano, Italy),
which we suggested comprise several cryptic species. To gain insights into the evolutionary
events that generated this differentiation, we performed a cytogenetic analysis in parallel with
a molecular assay. Approximately 80 cocoons of T. tubifex and T. blanchardi were collected
and dissected. For each cocoon, we sequenced a fragment of the 16S rRNA from half of the
sibling embryos and karyotyped the other half. To generate a robust phylogeny enabling the reconstruction of the evolutionary processes shaping the diversity of these sympatric lineages,
we complemented our original 16S rRNA gene sequences with additional COI sequences.
Results
The chromosome number distribution was consistent with the presence of at least six
sympatric euploid chromosome complements (one diploid, one triploid, three tetraploids and
one hexaploid), as confirmed by a FISH assay performed with an homologous 18S rDNA
probe. All the worms with 2n = 50 chromosomes belonged to an already identified sibling
species of T. tubifex, T. blanchardi. The six euploid sets were coherently arranged in the
phylogeny, with each lineage grouping specimens with the same chromosome complement.
Conclusions
These results are compatible with the hypothesis that multiple polyploidization events,
possibly enhanced by parthenogenesis, may have driven the evolution of the T. tubifex
species complex.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Cryptic species; Cytogenetics; Molecular phylogenetics; Polyploidy; Reproduction; Speciation; Tubifex
Elenco autori:
R. Marotta, A. Crottini, E. Raimondi, C. Fondello, M. Ferraguti
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