Size does matter: Parallel evolution of adaptive thermal tolerance and body size facilitates adaptation to climate change in domestic cattle

Abstract

The adaptive potential of livestock under a warming climate is increasingly relevant in relation to the growing pressure of global food security. Studies on heat tolerance demonstrate the interplay of adaptation and acclimatization in functional traits, for example, a reduction in body size and enhanced tolerance in response to a warming climate. However, current lack of understanding of functional traits and phylogenetic history among phenotypically distinct populations constrains predictions of climate change impact. Here, we demonstrate evidence of parallel evolution in adaptive tolerance to heat stress in dwarf cattle breeds (DCB, Bos taurus indicus) and compare their thermoregulatory responses with those in standard size cattle breeds (SCB, crossbred, Bos taurus indicus × Bos taurus taurus). We measured vital physiological, hematological, biochemical, and gene expression changes in DCB and SCB and compared the molecular phylogeny using mitochondrial genome (mitogenome) analysis. Our results show that SCB can acclimatize in the short term to higher temperatures but reach their tolerance limit under prevailing tropical conditions, while DCB is adapted to the warmer climate. Increased hemoglobin concentration, reduced cellular size, and smaller body size enhance thermal tolerance. Mitogenome analysis revealed that different lineages of DCB have evolved reduced size independently, as a parallel adaptation to heat stress. The results illustrate mechanistic ways of dwarfing, body size‐dependent tolerance, and differential fitness in a large mammal species under harsh field conditions, providing a background for comparing similar populations during global climate change. These demonstrate the value of studies combining functional, physiological, and evolutionary approaches to delineate adaptive potential and plasticity in domestic species. We thus highlight the value of locally adapted breeds as a reservoir of genetic variation contributing to the global domestic genetic resource pool that will become increasingly important for livestock production systems under a warming climate.

Key traits for ruminant livestock across diverse production systems in the context of climate change: perspectives from a global platform of research farms

“…Even though feed intake per se would no longer be considered a main priority, frame size and cow mature weight, as proxies of maintenance costs, would increase in priority for INRAE-SLP and NWFP. This highlights the role animal size may play in a climate change scenario because it is related to both maintenance requirements and adaptation to warmer conditions (Elayadeth-Meethal et al 2018). Feed efficiency, particularly of forage-based diets, would gain relevance in the future scenario, highlighting the importance of improving the use of homegrown feed resources that would likely be accompanied by variations in nutritional value (Howden et al 2008).…”

“…Therefore, it becomes relevant to work towards producing accurate genetic and genomic breeding values for traits particularly suited to different biotypes. This wide spectrum of biotypes varies widely in body size; therefore, when considering the wide diversity of environments and management practices within the global beef and sheep industry, the breed or cross must be carefully chosen in each case to obtain the animal size to maximise efficiency (Arango and Van Vleck 2002) and minimise biotic stresses (Elayadeth-Meethal et al 2018). In addition, there is a strong environment  genotype interaction component (Morris et al 1993) that must be considered when assessing candidates for selection.…”

Decadal heat and drought drive body size of North American bison (Bison bison) along the Great Plains

“…If Bison body size is declining in response to increasing temperature and drought, then projected climate change will further challenge growth and management of these animals and other large mammals (Elayadeth‐Meethal et al, ). The North American Bison may be sentinels of global climate change impacts on the Great Plains and prairies.…”

Comparative Expression Profiling and Sequence Characterization of ATP1A1 Gene Associated with Heat Tolerance in Tropically Adapted Cattle

“…Tolerance to high heat and humidity is a vital functional trait in species that evolved in adverse environments [ 1 , 2 , 3 ] and is mediated by molecular mechanisms that demonstrate the complex interplay of genes and environment [ 4 , 5 ]. In this context, the relationship between body size and tolerance to heat stress becomes critical [ 6 ] and, in southern India, is exemplified by the indigenous dwarf B. t. indicus cattle—the Vechur, the smallest cattle genotype in the world, and the slightly larger Kasaragod—that are mainly reared in the integrated farming systems that prevail in the region. Smaller size and tolerance to heat stress evolved in parallel as an adaptation to the tropical climate prevailing in their native habitat [ 6 ].…”