Transcriptomic variation and plasticity in rufous‐collared sparrows (Zonotrichia capensis) along an altitudinal gradient

Abstract

As modern genomic tools are developed for ecologically compelling models, field manipulation experiments will become important for establishing the role of functional genomic variation in physiological acclimation and evolutionary adaptation along environmental clines. High-altitude habitats expose individuals to hypoxic and thermal stress, necessitating physiological acclimation, which may result in evolutionary adaptation. We assayed skeletal muscle transcriptomic profiles of rufous-collared sparrows (Zonotrichia capensis) distributed along an altitudinal gradient on the Pacific slope of the Peruvian Andes. Nearly 200 unique transcripts were differentially expressed between high-altitude [4100 m above sea level (a.s.l.)] and low-altitude (2000 m a.s.l.) populations in their native habitats. Gene ontology and network analyses revealed that these transcripts are primarily involved in oxidative phosphorylation, protein biosynthesis, signal transduction and oxidative stress response pathways. To assess the plasticity in gene expression differences between populations, we performed a 'common garden' experiment in which high- and low-altitude individuals were transferred to a common low-altitude site (approximately 150 m). None of the genes that were differentially expressed between populations at the native altitudes remained significantly different between populations in the common garden. The role of gene expression variation in adaptation and acclimation to environmental stress is largely unexplored in natural populations of birds. These results demonstrate substantial plasticity in the biochemical pathways that underpin cold and hypoxia compensation in Z. capensis, which may mechanistically contribute to enabling the broad altitudinal distribution of the species.

Phylogeography: its development and impact in Australo-Papuan ornithology with special reference to paraphyly in Australian birds

“…Neutral markers must be distinguished from those under influence of selection. Developments such as pyrosequencing, the nuclear marker set of Backström et al (2008), and genechip technology (Cheviron et al 2008) hold promise here. Phylogeographic studies of Australian birds have already hinted at a role for selection in some groups (e.g.…”

Genomic insights into adaptation to high-altitude environments

“…Recently, we used a zebra finch cDNA microarray to measure transcriptomic variation among rufous-collared sparrow (Zonotrichia capensis) populations distributed along an altitudinal gradient in the Peruvian Andes (Cheviron et al, 2008). Initially, we measured gene expression profiles in individuals that were sampled at their native elevations, and identified over 200 genes that were differentially expressed between high-altitude (4100 m) and low-altitude (2000 m) populations.…”

“…Similarly, an explosion of genomic data has led to the proliferation of genomic tools, such as complementary DNA (cDNA) and oligonucleotide microarrays, and these tools are beginning to be used to study transcriptomic variation between high-and lowaltitude populations of non-model species (Cheviron et al, 2008). The genomic perspective provided by these technologies promises to yield novel insights into the mechanisms of high-altitude adaptation and acclimatization.…”

Stress hormone receptors change as range expansion progresses in house sparrows

“…Rather, we hypothesise that variation exists among individuals arriving at the range edge (possibly exemplified by the relatively high MR : GR ratio in Kakamega, the youngest population), but only individuals with a low MR : GR ratio, or those with the flexibility to reduce it rapidly in response to the novel environment, will survive (as exemplified by the low MR : GR ratio in Isiolo, Nyeri and Nakuru, with populations less than 10 years old; and intermediate levels in Nairobi, with populations less than 20 years old). Perpetuation of distinct phenotypes among populations might be a result of rapid evolution, developmental plasticity (early life experiences can shape GC receptor densities in the brain [18,19]) or individual flexibility responding to specific cues in the environment [20]; further, the adaptive values of these phenotypes are as yet unknown. Ultimately, however, the current experiment was not designed to elucidate the mechanism(s) of change, nor the adaptive values of those changes.…”