Chromosomal and molecular analysis of some repeated families in Discoglossus Otth, 1837 (Anura, Discoglossidae): Taxonomic and phylogenetic implications

Abstract

We conducted a cytogenetic and molecular analysis in six out of the eight Discoglossus taxa CD. pictus pictus, D. p. auritus, D. sardus, D. montalentii, D. galganoi galganoi and D. g. jean‐neae) All the taxa possessed 2n = 28 biarmed chromosomes, except D. pictus pictus where the 13th pair was acrocentric, and the NORs were located on the short arm of the 7th pair in all the taxa but D. galganoi, where they were on the short arm of the 13th pair. Heterochromatin was detected by banding methods (C‐band‐ing, base‐specific fluorochromes, replication patterns and digestions with restriction enzymes). The techniques used were able to discriminate among all the Discoglussus taxa studied, identifying several heterochromatin families with marked differences in chromosome location and/or in the behaviour of the banding techniques used. The differentiation of these heterochromatin families can have either a phylogenetic (as is the case with A+T rich cen‐tromeric heterochromatin) or an adaptive (G+C rich interstitial heterochromatin) meaning. Heterochromatin heterogeneity was also observed at molecular level. In D. p. pictus, DNA digestions with restriction enzymes revealed several satellite DNA families. The sequence of the monomeric unit, its chromosomal location and the divergence along the other Discoglossus taxa were detected for one of these families (Hind III). The molecular data obtained confirmed the relationships suggested by other authors in Discoglossus by osteological and genetic data.

Key words:

• Chromosomes
• Heterochromatin
• NORs
• Satellite DNA
• rDNA
• Discoglossus.