A metabolic syndrome in terrestrial ectotherms with different elevational and distribution patterns

Abstract

The metabolic performance of ectotherms is expected to be driven by the environment in which they live. Ecologically similar species with contrasting elevation distributions occurring in sympatry at mid‐elevations, provide good models for studying how physiological responses to temperature vary as a function of adaptation to different elevations. Under sympatry, at middle elevations, where divergent species ranges overlap, sympatric populations are expected to have similar thermal responses, suggesting similar local acclimation or adaptation, while observed differences would suggest adaptation to each species’ core range. We analysed the metabolic traits of sympatric species pairs from three ectotherm groups: reptiles (Reptilia: Lacertidae), amphibians (Amphibia: Salamandridae) and beetles (Coleoptera: Carabidae), living at different elevations, in order to test how adaptation to different elevations affects metabolic responses to temperature. We experimentally tested the thermal response of respiration rate (RR) and estimated potential metabolic activity (PMA) at three temperature regimes surrounding the groups’ optimal activity body temperatures. RR was relatively similar among groups and showed a positive response to increasing temperature, which was more pronounced in the high‐elevation species of reptiles and beetles. Relative to RR, PMA displayed a stronger and more consistent positive response to increased temperature in all three groups. For all three groups, the average biochemical capacity for metabolism (PMA) was higher in the range‐restricted, high‐elevation species, and this difference increased at higher temperatures in a consistent manner. These results, indicating consistent pattern in three independently evolved animal groups, suggest a ubiquitous adaptive syndrome and represent a novel understanding of the mechanisms shaping spatial biodiversity patterns. Our results also highlight the importance of geographic patterns for the mechanistic understanding of adaptations in physiological traits, including species’ potential to respond/adapt to global climate changes.

Resting metabolic rates increase with elevation in a mountain‐dwelling lizard

“…Although in this study we evaluated metabolic rate within the same species, which present the same foraging strategies in all populations, high activity levels could compensate for the short duration of thermal windows in high mountain habitats (Žagar et al . 2018).…”

Environmental temperatures shape thermal physiology as well as diversification and genome-wide substitution rates in lizards

“…We calculated yearly hours above 30 °C at 1 cm above the ground, rock surface, and at full sun exposure from the Microclim dataset 35 at a spatial resolution of ~18 × 18 km, as well as yearly hours >4 °C and with solar radiation of >100 W/m 2 . This computation is conceptually similar to the one used to predict the observed extinctions of lizards at global scales 16 , differing slightly in y and x -variable scales.…”

“…Lacertids are the most diverse and ubiquitous squamates in the Western Palearctic 14 containing around 340 species of rather conserved morphology. As predominant lizards in Europe, they have become a well-studied model group in hundreds of physiological, ecological and evolutionary studies, for instance yielding fundamental insights into evolutionary adaptation in diet, morphology, and metabolism 15,16 . Lacertids inhabit diverse habitats, from rainforests to deserts, at sea level and on high mountains.…”

“…Lacertids inhabit diverse habitats, from rainforests to deserts, at sea level and on high mountains. Some species occur in extremely hot and xeric environments in the Namib Desert 16 while one species ( Zootoca vivipara ) has the largest and northernmost distribution of all terrestrial squamates, reaching subarctic regions 17,18 . Because numerous lacertid genera are predominantly distributed in temperate zones that have experienced dramatic climatic changes during the Cenozoic, it can be expected that changing climatic conditions have had profound impacts on their evolutionary history.…”

Running performance with emphasis on low temperatures in a Patagonian lizard, Liolaemus lineomaculatus

“…The variance in thermal quality and physiognomy of the landscape did not result in differences in maximal velocities of the 0.15 m runs or the 1.05 m runs between populations. We expected the lower thermal quality of partially exposed and potential refuges models in the cold site to be correlated with a better running performance by those individuals, to compensate for having less time available with temperatures within the TTB, as seen in many terrestrial ectotherms such as insects, amphibians and reptiles 55 . Additionally, daily temperature amplitude is more variable at high elevations and, when daily variation is situated near the most thermally sensitive areas of the TPC (such as values near T opt or near the critical thermal minima or maxima), it can reduce performance 56 , which could affect individuals from the temperate site.…”