原文標題：Direction and strength of selection by predators for the color of the aposematic wood tiger moth

摘要 [原文連結]

Conventionally, predation is assumed to select for conspicuousness and uniformity of warning signals in aposematic (i.e., chemically defended and warning signaling) prey because this enhances predators' initial and learned avoidance. On the other hand, it has been suggested that both variation in the background where the signal is displayed as well as variation in predators' probability to attack defended prey may favor intermediate signals or relax selection for signal monomorphism. We studied the direction and strength of selection for the hind wing color (orange vs. red) of female Parasemia plantaginis moths. Birds found the moths aversive and avoided them by sight both in laboratory and field experiments. A laboratory experiment with great tits showed that birds can discriminate between orange and red wings and attack red females less than orange females. This directional selection should decrease variation in hind wing color. However, the hind wing color did not significantly affect the “survival” of dead specimens under natural field conditions in a multipredator community. In addition, even though both orange and red were highly conspicuous against green leaves and silver birch trunks (backgrounds used in the studies), the magnitude of avian-perceived chromatic contrast (conspicuousness) differed against these backgrounds. Our results suggest that depending on the signal environment (background, predator community) directional selection for the warning signal monomorphism can be relaxed.


結果顯示無論是紅色或橘色在鳥類眼中都是十分顯眼的顏色，而紅色的效用似乎大於橘色，但兩個顏色都仍是有效的警戒色，作者認為這樣的結果代表兩個顏色都能分擔捕食壓力，因此這樣的多態型能夠被保留下來。

這個結果雖然在某種程度上可以解釋為何警戒色有多態型，不過一個物種的多態型成因有很多，不同的顏色也可能代表小時候吃的食物不同，進而反應個體品質之類的；另一個點在於，這個燈蛾與那個螟蛾的大小好像有點差距，雖然燈蛾的顏色是顯眼多了沒錯，不過也可能是因為比較大，螟蛾比較小的緣故，但這算是瑕不掩瑜的小缺點啦。