Many studies have reported morphological plasticity of butterfly wing coloration in response to changes in thermal environments and other selection pressures. Darker butterfly species have been reported to occur in dark environments such as closed-canopy rainforests.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and University of Hongkong conducted a study to test whether differences in wing luminance are related to predation rates within open and closed habitats in monsoonal tropical forests of southwestern China.
The researchers surveyed butterfly communities in Xishuangbanna Nature Reserve in southernmost Yunnan. They used artificial butterflies (mealworms attached to plastic sheeting to mimic adult butterflies) of varying wing luminance (black and white) and size (large and small).
Using artificial butterflies, significantly lower predation rates were found for dark-coloured artificial butterflies within closed habitats, whereas such relationships were not found within open habitats. It was found that actual butterfly communities were also significantly darker in closed than in open habitats.
Their findings suggested that dark-winged butterflies are subject to lower predation rates than are light-colored butterflies within closed habitats, whereas both dark- and light-colored butterfly models suffer similar predation rates in open habitats.
The study showed that camouflaging plays a role in shaping luminance either separate from or in addition to thermoregulatory advantages in darker, closed habitats. Darker colors may have the effect of reducing predation rates in shady environments. Different habitat types can have contrasting effects on luminance and therefore predation risk.
The study entitled “Dark butterflies camouflaged from predation in dark tropical forest understories” has been published in Ecological Entomology.
Akihiro Nakamura Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China