AsianScientist (Sep. 9, 2016) – The differences in coloring within an aphid colony may depend upon aphids’ interactions with their allies rather than with their predators, scientists in Japan have observed.
These findings, published in Science Advances, reveal the first case of a difference in trait, called a polymorphism, driven by a symbiotic partnership rather than by predation.
Normally, polymorphisms are thought to be shaped by predator preferences: predators preferentially selecting prey with certain traits will influence the expression of those traits in the next generation of prey. However, predator-preference appeared to be an unlikely explanation for color polymorphism observed in the Japanese mugwort aphid, Macrosiphoniella yomogicola, mainly because these aphids experience little predation thanks to their symbiotic interactions with ants.
In this well-known interaction, these aphids exude honeydew, a sugary secretion favored by the ants. In return, the ants provide protection to the aphids. The aphid’s dependence on ant protection is strong; remove the ants and the aphids can quickly go locally extinct from heavy predation.
Pointing to this unique interaction, Dr. Saori Watanabe and colleagues from Hokkaido University hypothesized that the aphids’ color polymorphisms were dictated by the preferences of their ant partners. After collecting 85 aphid colonies and their ant partners, specifically ants of the species Lasius japonicus, the authors observed that more ants tended aphid colonies that were 65 percent green, suggesting that ants prefer a specific ratio of green to red aphids.
As a next step, Watanabe and team hope to investigate why exactly these ants favor this color ratio and how they maintain it in the aphid populations they tend.
The article can be found at: Watanabe et al. (2016) Color Polymorphism in an Aphid is Maintained by Attending Ants.
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Source: Science Advances.
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