A New Herpsilochmus Antwren (Aves: Thamnophilidae) from Northern Amazonian Peru and Adjacent Ecuador: The Role of Edaphic Heterogeneity of Terra firme Forest

Abstract

Herpsilochmus gentryi, the Ancient Antwren, is described from northern Amazonian Peru and from one locality in southeastern Ecuador. As for several other recently described birds, the new species was first identified by voice. Herpsilochmus gentryi is restricted to two structurally distinct kinds of terra firme forest, growing on nutrient-poor, podzolic and quartzitic soils; its distribution is almost entirely edaphically controlled. Morphological and vocal comparisons strongly indicate a sister relationship with H. stictocephalus of the widely disjunct Guianan region. Both species are sympatric with sister taxa of parallel geographic disjunction in the H. sticturus complex. However, the degree of syntopy in the two regions is different. We suggest that the more limited overlap of H. gentryi with H. sticturus dugandi is a function of higher habitat mosaicism resulting from Andean orogeny and fluvial perturbance in Amazonian Peru than on the relatively stable and uniform Guianan shield. Herpsilochmus gentryi is common within its habitat, but the habitat itself is naturally rare and patchily distributed. Construction of a road through these ancient and fragile habitats near the city of Iquitos has led to a dramatic increase in habitat destruction over just the last 10 years. Integration of satellite imagery and aerial photographs with multidisciplinary ground-truthing of soil types, and botanical inventories by teams from the University of Turku, has shown that terra firme landscape heterogeneity is high in Peruvian Amazonia, and at least some distinctive habitats, such as those of H. gentryi, are readily mapped. Both the history and destiny of H. gentryi exemplify how the deterministic effects of local edaphic conditions on phytogeographic and, by extension, bird distribution, define an integral role for these factors in conservation initiatives, and in revealing biogeographic patterns.