Description of a new Malagasy treefrog (Boophis) occurring syntopically with its sister species, and a plea for studies on non-allopatric speciation in tropical amphibians

Abstract

Based on concordant differences in male advertisement call, tadpole morphology, and absence of haplotype sharing in mitochondrial and nuclear DNA markers, we describe a new species of treefrog from Ranomafana National Park in the southern central east of Madagascar. In its adult stage Boophis narinsi sp. n. is highly similar to its sister species, Boophis majori, but appears to differ in having longer hindlimbs. The genetic divergences between these two species (2.5-3.3% in a fragment of the 16S rRNA gene, depending on fragment length and individual haplotype analyzed) are below the threshold typically characterizing distinct species of anurans. Together with their relatively small and largely overlapping ranges and their sympatric occurrence in Ranomafana National Park, this indicates that they potentially could have originated rather recently by adaptive speciation under parapatric or sympatric conditions. Most studies on amphibian speciation have so far by default assumed vicariant speciation. We suggest that alternative speciation scenarios should be considered in future works and characterize settings in which more reliable assessments of adaptive parapatric or sympatric speciation could be carried out.