Supplementary files available: Additional file 1: Specimen information. Museum catalogue numbers (QCAZ) for E. ockendeni and two outgroup species, GenBank accession numbers for cyt b and/or 16S fragment, and locality of origin for each individual used in the study.- Additional file 2: TN-corrected p-distance among cyt b haplotypes. TN-corrected p-distances among cyt b haplotypes of E. ockendeni, grouped by clade.
[Background] The forests of the upper Amazon basin harbour some of the world's highest anuran
species richness, but to date we have only the sparsest understanding of the distribution of genetic
diversity within and among species in this region. To quantify region-wide genealogical patterns and
to test for the presence of deep intraspecific divergences that have been documented in some
other neotropical anurans, we developed a molecular phylogeny of the wide-spread terrestrial
leaflitter frog Eleutherodactylus ockendeni (Leptodactylidae) from 13 localities throughout its range
in Ecuador using data from two mitochondrial genes (16S and cyt b; 1246 base pairs). We examined
the relation between divergence of mtDNA and the nuclear genome, as sampled by five speciesspecific
microsatellite loci, to evaluate indirectly whether lineages are reproductively isolated
where they co-occur. Our extensive phylogeographic survey thus assesses the spatial distribution
of E. ockendeni genetic diversity across eastern Ecuador.
[Results] We identified three distinct and well-supported clades within the Ecuadorean range of E.
ockendeni: an uplands clade spanning north to south, a northeastern and central lowlands clade, and
a central and southeastern clade, which is basal. Clades are separated by 12% to 15% net corrected
p-distance for cytochrome b, with comparatively low sequence divergence within clades. Clades
marginally overlap in some geographic areas (e.g., Napo River basin) but are reproductively
isolated, evidenced by diagnostic differences in microsatellite PCR amplification profiles or DNA
repeat number and coalescent analyses (in MDIV) best modelled without migration. Using Bayesian
(BEAST) and net phylogenetic estimates, the Southeastern Clade diverged from the Upland/
Lowland clades in the mid-Miocene or late Oligocene. Lowland and Upland clades speciated more
recently, in the early or late Miocene.
[Conclusion] Our findings uncover previously unsuspected cryptic species diversity within the
common leaflitter frog E. ockendeni, with at least three different species in Ecuador. While these
clades are clearly geographically circumscribed, they do not coincide with any existing landscape
barriers. Divergences are ancient, from the Miocene, before the most dramatic mountain building
in the Ecuadorean Andes. Therefore, this diversity is not a product of Pleistocene refuges. Our
research coupled with other studies suggests that species richness in the upper Amazon is
drastically underestimated by current inventories based on morphospecies.
Peer reviewed