CRYPTIC BIODIVERSITY: AN OVERLOOKED SPECIES AND NEW SUBSPECIES OF ANTBIRD (AVES: FORMICARIIDAE) WITH A REVISION OF CERCOMACRA TYRANNINA IN NORTHEASTERN

An undescribed population of antbirds in the Cercomacra tyranninalni- grescens complex that is sympatric with Cercomacra tyrannina was discovered north of Manaus, Brazil. The new population differs from Cercomacra tyrannina in plumage, certain mensural characters, and especially voice. Based on similarity of the song, the undescribed form from Manaus is considered conspecific with Cercomacra tyrannina laeta. However, because of the sympatry of the Manaus population with Cercomacra tyrannina, laeta must be elevated to full species level, with three subspecies: Cercomacra laeta laeta in extreme southeastern Amazonia; C. laeta sabinoi in northeastern Brazil; and a new subspecies described in this paper, known only from the vicinity of Manaus and eastern Roraima, approximately 650 km north Manaus. The population of Cercom- acra tyrannina north of the Amazon River and west of the Rio Negro, formerly assigned to Cercomacra tyrannina laeta, is shown to be allied with Cercomacra tyrannina rather than Cercomacra laeta. In this paper, we recognize a valid species and subspecies from two areas whose avifaunas are among the best known in tropical South America. The cryptic species, Cercomacra laeta, was already represented by many dozens of speci- mens in museum collections. Our findings demonstrate that the accurate cataloging of the planet's biodiversity will rely not only on expeditions to remote mountain valleys but also on a careful analysis of specimens and information already at our disposal.