The description of a cryptic species related to the pan-Amazonian frog Allobates femoralis (Boulenger 1883) (Anura: Aromobatidae)

Abstract

We describe a new species of litter frog from western Brazilian Amazon previously referred to as Allobates femoralis (Boulenger 1883). The new species is allopatric to A. femoralis and its known occurrence is restricted to terra-firme forests on the left bank of the upper Madeira River and southeastern State of Acre. This species is distinguished from A. femoralis and from other species in the A. femoralis group by presenting two-note advertisement calls and conspicuous reddish-orange color on ventral surfaces of hind limbs and posterior abdomen. Phylogenetic analyses based on a fragment of the 16S rRNA mitochondrial gene suggest the new species is the sister group to a clade referred to as A. femoralis occurring in southern State of Acre, from which it is distinguished by six unambiguous nucleotide substitutions, in addition to exclusive advertisement calls and color patterns. The new species is more distantly related to A. femoralis sensu stricto occurring near the A. femoralis type locality in the Peruvian Amazon. Summarizing evidence from molecular phylogenetic analysis, genetic distances and available data on advertisement calls, we identify one possible case of genetic introgression between lineages in this group and highlight the potential for the description of more species within the A. femoralis complex.

Restricted natural hybridization between two species of litter frogs on a threatened landscape in southwestern Brazilian Amazonia

“…Among these, the existence of genetic incompatibilities over multiple loci, or reduced fitness of F 1 hybrids (which are apparently rare across the contact zone area) are examples of possible intrinsic and extrinsic factors regulating contact zone position and width. For instance, A. femoralis is considered to be a color mimic of sympatric poison-frogs (Darst et al 2006), and color differences between A. femoralis and A. hodli are conspicuous (Simões et al 2010). Ongoing research supports the existence of spectrum overlap in body color between these species and the sympatric poison-frogs Ameerega picta and Adelphobates quinquevittatus from Jirau to Lower Jirau (Amézquita et al unpublished data).…”

“…The two species are easily distinguished by their advertisement calls (Fig. 1c), in addition to characteristic color patterns (Simões et al 2010).…”

“…As the two species are not each other's sister clades (Simões et al 2010), and have been distinct lineages for at least 2.5 million years (and most probably for around 4.5 million years- Santos et al 2009), the presence of mtDNA markers typical of one of the lineages within the genome of the other can be unambiguously attributed to genetic introgression rather than to incomplete lineage sorting from a recent polymorphic common ancestor.…”

“…However, the occurrence of contact zones and the description of areas of possible genetic introgression between divergent lineages of Amazonian lowland anurans have been poorly documented in the literature (e.g. point records are briefly mentioned in Brown and Twomey 2009;Simões et al 2010).…”

“…At the time, the two species were thought to represent distinct morphotypes of the widespread brilliantthighed poison frog, Allobates femoralis (Simões et al 2008;Amézquita et al 2009). Recently, summing information on the geographic distribution, mtDNA molecular phylogeny, and available evidence on morphological and acoustic differentiation, one of the former morphotypes was described as a new species, which has a restricted geographic distribution, being parapatric to, and highly divergent from the A. femoralis populations inhabiting the upper Madeira River basin (Simões et al 2010).…”