Abstract
Climate change is generating range shifts in many organisms, notably along the elevational gradient in mountainous environments. However, moving up in elevation exposes organisms to lower oxygen availability, which may reduce the successful reproduction and development of oviparous organisms. To test this possibility in an upward‐colonizing species, we artificially incubated developing embryos of the viperine snake (Natrix maura) using a split‐clutch design, in conditions of extreme high elevation (hypoxia at 2877 m above sea level; 72% sea‐level equivalent O2 availability) or low elevation (control group; i.e. normoxia at 436 m above sea level). Hatching success did not differ between the two treatments. Embryos developing at extreme high elevation had higher heart rates and hatched earlier, resulting in hatchlings that were smaller in body size and slower swimmers compared to their siblings incubated at lower elevation. Furthermore, post‐hatching reciprocal transplant of juveniles showed that snakes which developed at extreme high elevation, when transferred back to low elevation, did not recover full performance compared to their siblings from the low elevation incubation treatment. These results suggest that incubation at extreme high elevation, including the effects of hypoxia, will not prevent oviparous ectotherms from producing viable young, but may pose significant physiological challenges on developing offspring in ovo. These early‐life performance limitations imposed by extreme high elevation could have negative consequences on adult phenotypes, including on fitness‐related traits.
Highlights
Climate envelopes are typically much narrower across altitudinal than latitudinal gradients (Chen et al, 2011; Loarie et al, 2009), fostering rapid migration along the elevational gradient as the climate warms (e.g. Bässler et al, 2013; Freeman et al, 2018; Parmesan & Yohe, 2003; Pauchard et al, 2016; Walther et al, 2002)
Heart rates decreased throughout incubation but remained consistently and significantly higher in embryos incubated at extreme high elevation (EHE) (Table 1)
Any range shift driven by climate change is likely to be gradual, potentially allowing for animals to adjust their physiology and behavior by means of phenotypic plasticity and natural selection acting on advantageous genetic variants
Summary
Climate envelopes are typically much narrower across altitudinal than latitudinal gradients (Chen et al, 2011; Loarie et al, 2009), fostering rapid migration along the elevational gradient as the climate warms (e.g. Bässler et al, 2013; Freeman et al, 2018; Parmesan & Yohe, 2003; Pauchard et al, 2016; Walther et al, 2002). Well documented in birds and mammals (Beall et al, 2002; Lague et al, 2016; Monge & Leon-Velarde, 1991; Storz et al, 2004), the acute effects of hypoxia commonly include hyperventilation, tachycardia, altitude sickness, and the down-regulation of non-essential physiological functions (such as digestion) These studies demonstrate that chronic effects range from an alteration of cardiorespiratory pathways (increased lung and heart size, increased blood pressure), blood composition (increased haematocrit, increased haemoglobin concentration), and muscle performance (increased vascularization, increased amount of myoglobin and mitochondria) to effects on embryonic development, birth size, and early growth rates (Beall et al, 2002; Lague et al, 2016; Monge & Leon-Velarde, 1991; Storz et al, 2004). Rats and mice showed delayed brain growth due to long-term exposure to hypoxia (Golan & Huleihel, 2006), cognitive effects which may be true in reptiles as well (Sun et al, 2014)
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