Green-brown polymorphism in alpine grasshoppers affects body temperature.

Area of Science:

• Ecology
• Evolutionary Biology
• Animal Physiology

Background:

• Ectothermic animals rely on external heat sources, posing challenges in high-altitude environments with cold nights and short seasons.
• Color polymorphism, specifically green-brown variations, is widespread in Orthopterans (grasshoppers and related insects) but the underlying eco-evolutionary maintenance mechanisms remain unclear.

Purpose of the Study:

• To investigate if green and brown grasshopper morphs exhibit different thermoregulatory capacities under field conditions.
• To determine if thermoregulation plays a role in maintaining the green-brown color polymorphism in alpine grasshoppers.

Main Methods:

• Field measurements of grasshopper thorax temperatures were recorded.
• Temperatures were analyzed to compare heating rates and stable temperatures between morphs and sexes.

Main Results:

• Grasshopper thorax temperatures ranged from 1.7-42.1°C, with rapid morning heat-up and stabilization between 31-36°C.
• Female grasshoppers maintained significantly higher body temperatures (average 2.4°C higher) than males.
• Brown morphs were, on average, 1.5°C warmer than green morphs, notably in *Gomphocerus sibiricus* and *Pseudochorthippus parallelus*.

Conclusions:

• The observed difference in body temperature between brown and green morphs suggests a potential role for thermoregulatory capacity in maintaining color polymorphism.
• This thermoregulatory advantage, combined with other factors like crypsis, could explain the prevalence of these color variations in Orthopterans.