A Case of Rapid Diversification in the Neotropics: Phylogenetic Relationships among Cranioleuca Spinetails (Aves, Furnariidae)

Relationships among the 18-19 species of spinetails of the genus Cranioleuca are difficult to establish. Attempts based on traditional taxonomic characters have failed because of a high degree of homoplasy. Most morphological characters vary independently, producing leap-frog patterns of variation along the Eastern Brazilian Andean track, and behavior and vocalizations vary little. We use mtDNA sequence data from the cyt b and ND2 genes in an attempt to clarify relationships within the genus. We show (i) that Cranioleuca represents a recent burst of speciation and (ii) that a set of species thought by Maijer and Fjelds? (1997) to form a natural group is in fact a paraphyletic assemblage which also includes humid forest species with different pigmentations and vocalizations. However, synapomorphic variation in the sequences is not sufficient to unambiguously resolve the relationships within the genus. Several species (C. baroni, C. antisiensis, C. pyrrhophia, C. albiceps) show more than one haplotype, without any obvious correlation between genetic and geographic or morphological variation, and the different species do not always show reciprocal monophyly in haplotype diversity. Nevertheless, low genetic differentiation characterizes not only allopatric taxa but also some forms which are essentially sympatric, supporting species rank for the former. Our data suggest a recent diversification and proliferation possibly linked to Pleistocene climatic variation and its consequent vegetational shifts, at least in the Andean species.