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Animals developing at high elevation experience a suite of environmental challenges, most notably the low partial pressure of oxygen ( P O 2 ) in ambient air. In low P O 2 , bird species with high-elevation ancestry consistently demonstrate higher hatching success than lowland counterparts, suggesting highland birds are adapted to restricted O 2 (hypoxia) in early development. Haemoglobin (Hb), the critical oxygen-transport protein, is a likely target of P O 2 -related selection across ontogeny since Hb isoforms expressed at distinct developmental stages demonstrate different O 2 affinities. To test if Hb function is under P O 2 -related selection at different ontogenetic stages, we sampled a songbird, the hooded siskin ( Spinus magellanicus ), across two approximately 4000 m elevational transects. We sequenced all of the loci that encode avian Hb isoforms, and tested for signatures of spatially varying selection by comparing divergence patterns in Hb loci to other loci sampled across the genome. We found strong signatures of diversifying selection at non-synonymous sites in loci that contribute to embryonic ( α π , β H ) and definitive ( β A ) Hb isoforms. This is the first evidence for selection on embryonic haemoglobin in high-elevation Neoaves. We conclude that selection on Hb function at brief, but critical stages of ontogeny may be a vital component to high elevation adaptation in birds. 

We describe a colorful and distinctive new species of tanager from the lower slopes of the Andes of southeastern Peru and western Bolivia. The species was first noted from southeastern Peru in 2000, but little of its natural history was uncovered until the 2011 discovery of a breeding population in deciduous forest in an intermontane valley, the Machariapo valley, in Bolivia. This species appears to be an intratropical migrant, breeding in deciduous forest during the rainy season (November–March) and spending the dry season dispersed along the lower slopes of the Andes, apparently favoring Guadua bamboo-dominated habitats in both seasons. Phylogenetic evidence suggests this tanager is embedded within a clade of thraupids that includes Ramphocelus, Coryphospingus, Loriotus, Tachyphonus, and related genera in the subfamily Tachyphoninae. Within this subfamily, the new species falls in a clade with two monotypic genera, Eucometis penicillata (Gray-headed Tanager) and Trichothraupis melanops (Black-goggled Tanager). There is strong support for a sister relationship between the new tanager and T. melanops, but because all three species in this clade are highly distinctive phenotypically, we propose erecting a new genus and species name for the new tanager.

 

Geographic turnover in community composition is created and maintained by eco-evolutionary forces that limit the ranges of species. One such force may be antagonistic interactions among hosts and parasites, but its general importance is unknown. Understanding the processes that underpin turnover requires distinguishing the contributions of key abiotic and biotic drivers over a range of spatial and temporal scales. Here, we address these challenges using flexible, nonlinear models to identify the factors that underlie richness (alpha diversity) and turnover (beta diversity) patterns of interacting host and parasite communities in a global biodiversity hot spot. We sampled 18 communities in the Peruvian Andes, encompassing ∼1,350 bird species and ∼400 hemosporidian parasite lineages, and spanning broad ranges of elevation, climate, primary productivity, and species richness. Turnover in both parasite and host communities was most strongly predicted by variation in precipitation, but secondary predictors differed between parasites and hosts, and between contemporary and phylogenetic timescales. Host communities shaped parasite diversity patterns, but there was little evidence for reciprocal effects. The results for parasite communities contradicted the prevailing view that biotic interactions filter communities at local scales while environmental filtering and dispersal barriers shape regional communities. Rather, subtle differences in precipitation had strong, fine-scale effects on parasite turnover while host–community effects only manifested at broad scales. We used these models to map bird and parasite turnover onto the ecological gradients of the Andean landscape, illustrating beta-diversity hot spots and their mechanistic underpinnings.