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Elevational migration is a widespread phenomenon in tropical avifauna but it is difficult to identify using traditional approaches. Hydrogen isotope (δ 2 H) values of precipitation decrease with elevation so δ 2 H analysis of multiple bird tissues with different isotopic incorporation rates may be a reliable method for characterizing seasonal elevational migration. Here we compare δ 2 H values in metabolically inert (feathers and claws) and metabolically active (whole blood) tissues to examine whether an upslope migration occurs prior to the breeding season in the Yungas Manakin (Chiroxiphia boliviana). We compare results from C. boliviana with data from a known elevational migrant, the Streak-necked Flycatcher (Mionectes striaticollis). Opposite to our expectations, tissue δ 2 H values increased over time, largely reflecting seasonal patterns in precipitation δ 2 H rather than elevational effects; linear mixed-effects models with strongest support included ordinal date, tissue type, and elevation. This seasonal increase in precipitation δ 2 H is a general phenomenon in both tropical and temperate mountain ranges. We use these data to propose a hypothetical framework that predicts different patterns in tissue δ 2 H values collected in different seasons from residents and elevational migrants. This framework can serve as a reference for future studies that assess elevational migration in birds and other animals., (© 2016 by the Ecological Society of America.)

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Species distribution models are useful for identifying the ecological characteristics that may limit a species' geographic range and for inferring patterns of speciation. Here, we test a hypothesis of niche conservatism across evolutionary time in a group of manakins (Aves: Pipridae), with a focus on Chiroxiphia boliviana, and examine the degree of ecological differentiation with other Chiroxiphia and Antilophia manakins. We tested whether allopatric sister species were more or less similar in environmental space than expected given their phylogenetic distances, which would suggest, respectively, ecological niche conservatism over time or ecologically mediated selection (i.e. niche divergence). We modeled the distribution of nine manakin taxa (C. boliviana, C. caudata, C. lanceolata, C. linearis, C. p. pareola, C. p. regina, C. p. napensis, Antilophia galeata and A. bokermanni) using Maxent. We first performed models for each taxon and compared them. To test our hypothesis we followed three approaches: (1) we tested whether C. boliviana could predict the distribution of the other manakin taxa and vice versa; (2) we compared the ecological niches by using metrics of niche overlap, niche equivalency and niche similarity; and (3) lastly, we tested whether niche differentiation corresponded to phylogenetic distances calculated from two recent phylogenies. All models had high training and test AUC values. Mean AUC ratios were high (>0.8) for most taxa, indicating performance better than random. Results suggested niche conservatism, and high niche overlap and equivalency between C. boliviana and C. caudata, but we found very low values between C. boliviana and the rest of the taxa. We found a negative, but not significant, relationship between niche overlap and phylogenetic distance, suggesting an increase in ecological differentiation and niche divergence over evolutionary time. Overall, we give some insights into the evolution of C. boliviana, proposing that ecological selection may have influenced its speciation. [ABSTRACT FROM AUTHOR]

Elevational migration is a widespread phenomenon in tropical avifauna but it is difficult to identify using traditional approaches. Hydrogen isotope (δ2H) values of precipitation decrease with elevation so δ2H analysis of multiple bird tissues with different isotopic incorporation rates may be a reliable method for characterizing seasonal elevational migration. Here we compare δ2H values in metabolically inert (feathers and claws) and metabolically active (whole blood) tissues to examine whether an upslope migration occurs prior to the breeding season in the Yungas Manakin ( Chiroxiphia boliviana). We compare results from C. boliviana with data from a known elevational migrant, the Streak-necked Flycatcher ( Mionectes striaticollis). Opposite to our expectations, tissue δ2H values increased over time, largely reflecting seasonal patterns in precipitation δ2H rather than elevational effects; linear mixed-effects models with strongest support included ordinal date, tissue type, and elevation. This seasonal increase in precipitation δ2H is a general phenomenon in both tropical and temperate mountain ranges. We use these data to propose a hypothetical framework that predicts different patterns in tissue δ2H values collected in different seasons from residents and elevational migrants. This framework can serve as a reference for future studies that assess elevational migration in birds and other animals. [ABSTRACT FROM AUTHOR]