Summary from the authors: 31° South: The physiology of adaptation to arid conditions in a passerine bird

Karoo scrub-robin (Cercotrichas coryphaeus) in its typical arid habitat in southern Africa. Photo by Krista N. Oswald.

Written by Ângela M. Ribeiro

Arid environments are ecosystems of energetic stringency. Their typical high temperatures, low primary productivity, and unpredictable water availability prove physiologically challenging for birds. How these vertebrates cope with such harshness remains a conundrum in physiological evolutionary biology. While physiological adaptation likely involves energetic metabolic phenotypes, the underlying mechanisms (plasticity, genetics) are largely uncharacterized. To explore this, we developed a intra-specific level framework (Figure 1) that links environmental conditions, phenotypes and genotypes in a passerine bird whose range spans an aridity gradient. We found variation in energetic physiology phenotypes (a measure of energy expenditure) and gut microbiota composition (involved in energy retrieval from food) to be associated with environmental features and identified a small list of candidate adaptive genes. By working at the interface of physiology and genomics, we suggest that selective pressures on energetic physiology mediated by genes related to energy homeostasis and possibly with contribution of gut microbiota may facilitate adaptation to local conditions. Ultimately, our findings offer a possible explanation to the high avian intra-specific divergence observed in harsh environments, raises awareness that accounting for intra-specific variation is fundamental when modeling physiological responses to climate change, and provides a stepping-stone for further research into the mechanisms of phenotypic adaptation to aridity.

Figure 1. Conceptual framework to infer the mechanisms of physiological adaptation to aridity: linking environment (climate and primary productivity), phenotype (organism-level energetic metabolism: basal metabolic rate and metabolic expansibility; microbiome composition) and genotype (genetic variation in genes underlying the biochemical machinery of energy production).

Link to paper: https://onlinelibrary.wiley.com/doi/full/10.1111/mec.15176

Ribeiro ÂM, Puetz L, Pattinson NB, Dálen L, Deng Y, Zhang G, da Fonseca RR, Smit B, Gilbert MT. (2019). 31° South: The physiology of adaptation to arid conditions in a passerine bird. Molecular Ecology. 2019. 28-16. 3709-3721.