Accommodating natural and sexual selection in butterfly wing pattern evolution
Jeffrey C. Oliver1,Kendra A. Robertson2 and Antónia Monteiro1,2
Proc. R. Soc. B 7 July 2009 vol. 276 no. 1666 2369-2375
動物的視覺樣式可能具有不同的功能，例如吸引配偶與欺騙天敵。假設一個訊號具有多重的功能，不同功能間便有可能發生衝突，而妨礙任何視覺訊號的最佳化。作者對“Bicyclus屬蝴蝶具有不同視覺訊號功能的空間性區隔“之假說進行驗證。運用特徵演化的親緣關係重建與演化速率之比較，作者發現背面的特徵眼化速率比腹面快速。因此，背面的特徵與作者對交配訊號的預測有關、而腹面特徵則在避免天敵的功能上扮演重要的角色。前翅的特徵亦符合交配訊號的模型、且表現出比後翅特徵更高的演化速率。作者的結果，與前人在行為與發育上的研究資料吻合，均支持“Bicyclus屬蝴蝶具有不同視覺訊號功能的空間性區隔“之假說。本研究是首先以親緣關係架構證明：使用在交配訊息上與用來避免捕食者的訊號空間性區隔是可行的策略，可調和多重的訊號功能。這種訊號策略對於蝴蝶翅膀斑紋元件之發育與分化的演化具有重要的衍生脈絡。
Abstract
Visual patterns in animals may serve different functions, such as attracting mates and deceiving predators. If a signal is used for multiple functions, the opportunity arises for conflict among the different functions, preventing optimization for any one visual signal. Here we investigate the hypothesis that spatial separation of different visual signal functions has occurred in Bicyclus butterflies. Using phylogenetic reconstructions of character evolution and comparisons of evolutionary rates, we found dorsal surface characters to evolve at higher rates than ventral characters. Dorsal characters also displayed sex-based differences in evolutionary rates more often than did ventral characters. Thus, dorsal characters corresponded to our predictions of mate signalling while ventral characters appear to play an important role in predator avoidance. Forewing characters also fit a model of mate signalling, and displayed higher rates of evolution than hindwing characters. Our results, as well as the behavioural and developmental data from previous studies of Bicyclus species, support the hypothesis that spatial separation of visual signal functions has occurred in Bicyclus butterflies. This study is the first to demonstrate, in a phylogenetic framework, that spatial separation of signals used for mate signalling and those used for predator avoidance is a viable strategy to accommodate multiple signal functions. This signalling strategy has important ramifications on the developmental evolution of wing pattern elements and diversification of butterfly species.
Jeffrey C. Oliver1,Kendra A. Robertson2 and Antónia Monteiro1,2
Proc. R. Soc. B 7 July 2009 vol. 276 no. 1666 2369-2375
動物的視覺樣式可能具有不同的功能，例如吸引配偶與欺騙天敵。假設一個訊號具有多重的功能，不同功能間便有可能發生衝突，而妨礙任何視覺訊號的最佳化。作者對“Bicyclus屬蝴蝶具有不同視覺訊號功能的空間性區隔“之假說進行驗證。運用特徵演化的親緣關係重建與演化速率之比較，作者發現背面的特徵眼化速率比腹面快速。因此，背面的特徵與作者對交配訊號的預測有關、而腹面特徵則在避免天敵的功能上扮演重要的角色。前翅的特徵亦符合交配訊號的模型、且表現出比後翅特徵更高的演化速率。作者的結果，與前人在行為與發育上的研究資料吻合，均支持“Bicyclus屬蝴蝶具有不同視覺訊號功能的空間性區隔“之假說。本研究是首先以親緣關係架構證明：使用在交配訊息上與用來避免捕食者的訊號空間性區隔是可行的策略，可調和多重的訊號功能。這種訊號策略對於蝴蝶翅膀斑紋元件之發育與分化的演化具有重要的衍生脈絡。
Abstract
Visual patterns in animals may serve different functions, such as attracting mates and deceiving predators. If a signal is used for multiple functions, the opportunity arises for conflict among the different functions, preventing optimization for any one visual signal. Here we investigate the hypothesis that spatial separation of different visual signal functions has occurred in Bicyclus butterflies. Using phylogenetic reconstructions of character evolution and comparisons of evolutionary rates, we found dorsal surface characters to evolve at higher rates than ventral characters. Dorsal characters also displayed sex-based differences in evolutionary rates more often than did ventral characters. Thus, dorsal characters corresponded to our predictions of mate signalling while ventral characters appear to play an important role in predator avoidance. Forewing characters also fit a model of mate signalling, and displayed higher rates of evolution than hindwing characters. Our results, as well as the behavioural and developmental data from previous studies of Bicyclus species, support the hypothesis that spatial separation of visual signal functions has occurred in Bicyclus butterflies. This study is the first to demonstrate, in a phylogenetic framework, that spatial separation of signals used for mate signalling and those used for predator avoidance is a viable strategy to accommodate multiple signal functions. This signalling strategy has important ramifications on the developmental evolution of wing pattern elements and diversification of butterfly species.
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