Andean butterflies inherit different heat responses at different elevations

Inherited and temperature-linked traits

The two species showed parallel differences in wing colour: butterflies from higher elevations had darker wings than those from lower elevations. This pattern is consistent with darker wings helping regulate body temperature, although the study did not directly demonstrate that function.

Researchers also found evidence that genes and the environment interact to shape heat responses. In H. erato, butterflies from low-elevation populations had longer heat knock-out times when raised at higher temperatures. This change was not found in high-elevation populations, which experience cooler conditions in the wild.

Most of the traits measured showed heritable genetic variation. The researchers also found differences in developmental and morphological traits, as well as evidence that environmental conditions affected some traits. They conclude that selection may not act on these traits in a simple or uniform way.

Why elevation responses matter

Tropical temperatures are relatively stable year-round, so the temperature differences across short elevation gradients can be especially important for local adaptation. Showing that butterfly populations have both inherited differences and environment-dependent heat responses helps clarify how closely related populations may diverge across elevations.

Heritable variation in many traits could provide some capacity for populations to respond to changing climates. However, the finding that responses depend on both population origin and rearing temperature means climate adaptation may not follow a single predictable pattern.

How the study tested this

The study used common-garden rearing and reciprocal temperature experiments, which allow researchers to separate inherited differences from effects of the rearing environment and their interaction. The sample included more than 1,000 offspring from over 70 wild females representing an Andean elevation gradient.

The evidence comes from two neotropical butterfly species and the populations sampled along this gradient. The abstract does not report whether the measured differences improve survival or reproduction in the wild, nor does it establish how the traits will change under future climates. The darker wing colour pattern is consistent with a role in heat regulation, but that function was not directly tested in the study.