Communicator whistles: A Trek through the taxonomy of the Boophis marojezensis complex reveals seven new, morphologically cryptic treefrogs from Madagascar (Amphibia: Anura: Mantellidae)

Abstract

The Malagasy stream-breeding treefrog species Boophis marojezensis contains bioacoustically and genetically highly divergent populations. Some of these populations have been defined as candidate species and emit somewhat bizarre advertisement calls consisting of multiple whistle-notes. We here enable a long-overdue taxonomic revision of this species complex by applying a museomics approach to sequence DNA from the holotype of B. marojezensis. Based on an integrative approach that combines divergence levels in mitochondrial DNA and in three nuclear-encoded genes, morphological data, and bioacoustic comparisons, we conclude that eight different species exist in this complex, seven of which are formally described herein as new. Although morphological differences between species are small and mainly separate small-sized from larger-sized species, conclusive evidence for the new species comes from their sympatric and sometimes syntopic occurrence without haplotype sharing in three nuclear genes and under maintenance of bioacoustic differences. Uncorrected genetic divergences in the mitochondrial 16S rRNA gene are >3% in almost all cases, and in some cases up to 8%. In reference to the otherworldly sounds by which these frogs fill Malagasy rainforests, some of them reminiscent of sounds of technical equipment in the fictional “Star Trek” universe, we here name and describe the seven new species in honor of fictional captains of starships, namely B. kirkisp. nov., B. picardisp. nov., B. siskoisp. nov., B. janewayaesp. nov., B. archerisp. nov., B. pikeisp. nov., and B. burnhamaesp. nov. The majority of these species occur in northern Madagascar, where up to three species can occur in immediate geographical proximity, e.g., B. marojezensis, B. burnhamaesp. nov. and B. pikeisp. nov. at different elevations in the Marojejy Massif. South of 16°S latitude, only B. janewayaesp. nov., B. picardisp. nov., and B. kirkisp. nov. are found, with the latter extending southwards to Ranomafana National Park. Our study confirms the existence of numerous morphologically cryptic and microendemic species among Madagascar’s amphibians, some of which are known only from unprotected sites and require adequate conservation management.