Phylogenetic relationships and systematics of the bamboo‐specialistAmaurospizablue seedeaters

Abstract

TheAmaurospiza‘seedeaters’ are bamboo‐specialized mixed strategists, most often found in bamboos in vegetative state, feeding on buds, shoots, petioles and insects. As bamboos die after flowering, birds may wander in search of live vegetative bamboo. The three currently recognized species ofAmaurospizaare allopatrically distributed: the Blackish‐blue SeedeaterAmaurospiza moestain the Atlantic Forest of Argentina, Brazil and Paraguay, and in forest enclaves in the Cerrado; the recently described Carrizal SeedeaterAmaurospiza carrizalensisknown from a few localities in southeastern Venezuela; and the Blue SeedeaterAmaurospiza concolordistributed patchily from Mexico to Peru. Three subspecies are recognized withinA. concolor:relictain southwest Mexico,concolorfrom southern Mexico to Panama andaequatorialisfrom southwest Colombia to northwest Peru. Full species status has been advocated forrelictaandaequatorialisbut evidence supporting their recognition is weak, whilerelictawas described in the monospecific genusAmaurospizopsis. Here we (1) test the monophyly ofAmaurospiza, (2) reconstruct the phylogenetic relationships of all its constituent taxa using mitochondrial and nuclear markers, (3) re‐assess species limits inAmaurospizawith the aid of vocalizations and genetic and plumage data, and (4) discuss the link between bamboo life history, biogeographical patterns and extent of genetic differentiation.Amaurospizawas found to be monophyletic in both theND2and multilocus analyses. In theND2treeA. moestaandA. carrizalensiswere sister to each other,A. concolorwas found to be paraphyletic becauseaequatorialiswas placed as sister tomoesta–carrizalensis, and a clade including nominateconcolorandrelictawas sister to all the other taxa. The multilocus tree showed the same relationships, but lacked nuclear samples ofrelicta. MeanND2pairwise distance betweenconcolorandaequatorialis(8.3%) was greater than that betweenmoestaandcarrizalensis(5.7%), whilerelictadiverged on average 1.0% from nominateconcolor. The South American clade has more slender bills and white underwing coverts, while the Central American clade has thicker bills and bluish underwing coverts. All taxa exhibited typicalAmaurospizasongs with quickly delivered, warbled, pure and fairly high‐pitched musical notes. Number of inflections/second exhibited a stepped pattern, withconcolorandrelictaon the lower end andcarrizalensis,aequatorialisandmoestaon the upper end. Similarly,moesta,carrizalensisandaequatorialishad overall more inflections per note thanconcolorandrelicta. Linear discriminant analysis using nine acoustic variables correctly assigned all 62 songs to the correct taxon. Morphology, plumage, vocalizations and phylogenetic data indicate thataequatorialisshould be afforded full species status as the Ecuadorian Seedeater (A. aequatorialis), suggest keepingrelictaas a subspecies ofA. concolorand support continued recognition ofA. carrizalensis. Our data support mergingAmaurospizopsisintoAmaurospiza.