Trade-off between thermal preference and sperm maturation in a montane lizard

Area of Science:

• Ecology
• Physiology
• Reproductive Biology

Background:

• Temperature is a critical abiotic factor influencing ectotherm physiology.
• Ectotherms regulate body temperature to optimize physiological functions like speed and reproduction.

Purpose of the Study:

• To investigate the impact of temperature on locomotor performance and sperm viability in the high-elevation lizard species, *Sceloporus aeneus*.
• To assess the trade-offs between physical performance and reproductive health under varying thermal conditions.

Main Methods:

• Field active and preferred body temperatures were identified for *Sceloporus aeneus*.
• Locomotor performance (sprint speed) was measured at preferred temperatures.
• Sperm morphology, concentration, motility, and viability were assessed after short-term exposure to preferred temperatures.

Main Results:

• Maximal sprint speed in *Sceloporus aeneus* occurred at their field active and preferred body temperatures.
• Exposure to preferred temperatures resulted in abnormal sperm morphology, reduced sperm concentration, and diminished motility and viability.
• A trade-off exists between optimal locomotor performance and male reproductive health at preferred temperatures.

Conclusions:

• While locomotor performance is maximized at preferred temperatures, this negatively impacts male reproductive attributes, potentially leading to infertility.
• Prolonged exposure to preferred temperatures may jeopardize the species' persistence due to reduced fertility.
• Access to cooler thermal microhabitats is essential for enhancing reproductive parameters and ensuring species survival.