Abstract
Goats living in arid and semi-arid environments combine morphological and physiological strategies to maintain homeothermy; autochthonous breeds from the Canary Islands and Brazil’s semi-arid region offer a natural model to compare these adaptive profiles. In this study, we characterized the adaptive profile of five populations: Majorera, Palmera, and Northern Tinerfeña (Spain) and Canindé and Moxotó (Brazil). A total of 150 goats (30 per breed), all clinically healthy, non-pregnant, non-lactating females of reproductive age (2–4 years), were evaluated. Morphological traits included coat thickness (CT), hair diameter (HD), and hair length (HL); physiological indicators included rectal temperature (RT) and respiratory rate (RR). Among the Spanish breeds, RT did not differ (p > 0.05; ≈ 39.2 °C), whereas RR was higher in North Tinerfeña (p < 0.05) than in Majorera and Palmera. Palmera and North Tinerfeña showed greater CT and HL (p < 0.05; CT) compared with Majorera (CT ≈ 1.06 mm; HL ≈ 36.7 mm), and HD also differed among the Spanish breeds (p < 0.05). In the Brazilian breeds, RT did not differ (p > 0.05); however, Canindé exhibited higher RR (p < 0.05), CT (p < 0.05), and HL (p < 0.05), while HD was similar between breeds (p > 0.05). In multivariate analyses, principal component biplots indicated predominantly morphological variability in the Spanish breeds and predominantly physiological variability in the Brazilian breeds; correspondence analysis clearly separated Spanish and Brazilian groups; discriminant analysis confirmed this distinction (Wilks’ λ, P < 0.001) and achieved higher classification accuracy when morphological variables were considered, especially for classifying Majorera. On their own, physiological variables had lower discriminatory power in the Brazilian breeds. Interestingly, Majorera clustered closer to Moxotó and Canindé in multivariate space, while remaining distinct from Palmera and Northern Tinerfeña. Collectively, the results reveal two complementary adaptive profiles: (i) morphological insulation that attenuates heat gain and reduces demand for active heat loss (predominant in Spanish breeds), and (ii) physiological adjustment emphasizing evaporative heat loss (predominant in Brazilian breeds). These findings provide actionable evidence for genetic resource conservation and inform breeding programs oriented toward thermal resilience under warming and aridification scenarios.