Shape-shifting: changing animal morphologies as a response to climatic warming

Appendages have an important, but often undervalued, role in animal thermoregulation as sites of heat exchange. This thermoregulatory role leads to geographic clines in animal morphology where animals at lower latitudes, in warmer climates, have larger appendages (a pattern known as ‘Allen’s rule’). Animals are shifting their morphologies to have proportionately larger appendages in response to climate change and its associated temperature increases. This proportional increase in relative appendage size, and therefore subsequent change in body proportions, can be referred to as ‘shape-shifting’ and is an underappreciated response to climatic warming. Many animal appendages, such as avian beaks and mammalian ears, can be used to dissipate excess body heat. Allen’s rule, wherein animals in warmer climates have larger appendages to facilitate more efficient heat exchange, reflects this. We find that there is widespread evidence of ‘shape-shifting’ (changes in appendage size) in endotherms in response to climate change and its associated climatic warming. We re-examine studies of morphological change over time within a thermoregulatory context, finding evidence that temperature can be a strong predictor of morphological change independently of, or combined with, other environmental changes. Last, we discuss how Allen’s rule, the degree of temperature change, and other ecological factors facilitate morphological change and make predictions about what animals will show shape-shifting. Many animal appendages, such as avian beaks and mammalian ears, can be used to dissipate excess body heat. Allen’s rule, wherein animals in warmer climates have larger appendages to facilitate more efficient heat exchange, reflects this. We find that there is widespread evidence of ‘shape-shifting’ (changes in appendage size) in endotherms in response to climate change and its associated climatic warming. We re-examine studies of morphological change over time within a thermoregulatory context, finding evidence that temperature can be a strong predictor of morphological change independently of, or combined with, other environmental changes. Last, we discuss how Allen’s rule, the degree of temperature change, and other ecological factors facilitate morphological change and make predictions about what animals will show shape-shifting. Shape-shifting: changing animal morphologies as a response to climatic warming: (Trends in Ecology and Evolution , 1036–1048; 2021)Ryding et al.Trends in Ecology & EvolutionJanuary, 2022In BriefA reference was omitted from the article ‘Shape-shifting: changing animal morphologies as a response to climatic warming’ when it was published. The corrected text, reference citation, and reference details appear below. The authors apologise profusely for this oversight. Full-Text PDF