A small white butterfly (left) and a green-veined white butterfly meeting (right) meeting head to head in nature.
Newswise — A study published in Nature Communications by researchers at Stockholm University delves into how different organisms have evolved to adapt to the contrasting living conditions of summer and winter seasons in various parts of the world. The researchers focused on two closely related butterfly species, namely the small white butterfly and the green-veined white butterfly, to investigate this phenomenon.
Loke von Schmalensee, a doctoral student in ecology at Stockholm University's Department of Zoology, emphasizes the significance of their approach in comprehending species' responses to future changes in environmental conditions. By examining seasonal adaptations, the research team aimed to shed light on how these butterflies cope with the varying seasons.
Despite their similar appearance, with both species being medium-sized and white, the small white butterfly and the green-veined white butterfly possess distinct adaptations. Typically, they exhibit a preference for laying eggs on the same cruciferous plants under ordinary circumstances. These butterflies coexist in many parts of Sweden, where their two generations per year coincide temporally.
In summary, the study focuses on exploring the seasonal adaptations of the small white butterfly and the green-veined white butterfly, which share common traits but differ in specific strategies to cope with changing environmental conditions.
The ecological similarity between the small white butterfly and the green-veined white butterfly is evident. However, upon analyzing butterfly observations reported by citizen scientists on www.artportalen.se, the research team made a significant discovery regarding the contrasting characteristics of their two annual generations. In terms of size, the small white butterfly's first generation, which emerges during spring and early summer, is considerably smaller in number compared to its second generation in late summer. On the other hand, the green-veined white butterfly exhibits two generations of relatively equal size.
Interestingly, the small white butterfly demonstrates superior reproductive abilities during the summer but displays poorer winter survival rates. It can be considered a 'summer specialist,' while the green-veined white butterfly can be classified as a 'winter specialist.' This contrast is associated with a range of temperature adaptations, as explained by Loke von Schmalensee.
For instance, the small white butterfly exhibits a preference for laying eggs in warmer locations during the summer, in contrast to the green-veined white butterfly. This divergence in preference corresponds to distinct physiological temperature adaptations between the two species.
Through laboratory experiments, we have observed that the small white butterfly, which thrives in warm conditions, exhibits faster growth and development compared to the green-veined white butterfly. Moreover, the small white butterfly demonstrates higher survival rates when subjected to extreme heat. On the other hand, the green-veined white butterfly displays better adaptability to cold overwintering conditions. When individuals encounter distinct seasons throughout their lives, various evolutionary strategies emerge to tackle seasonal challenges. According to Loke von Schmalensee, maximizing gains during the summer season, even if it comes at the expense of winter survival, is one viable strategy, while investing in winter adaptations is another.
Over the past decade, the heat-adapted "summer specialist," the small white butterfly, has exhibited superior performance compared to the "winter specialist," the green-veined white butterfly. However, the small white butterfly faces limitations in its ability to expand its range further north, as the summer season becomes too short to support the development of two generations. Without a second generation to compensate for winter losses, the small white butterfly populations experience collapse.
As a result, in a warming world, northern latitudes or high mountains may serve as crucial refuges for "winter specialists." This finding exemplifies how our research results aid in predicting the responses of organisms to climate change, as explained by Loke von Schmalensee.
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