Diet for city butterflies
Next time you see a small but conspicuous butterfly flutter by, it could well be a “picky” feeder that only goes for specific flowers.
NUS biologists discovered that although most tropical butterflies feed on a variety of flower types, those species choosy about their flower diets tend to prefer native plants and are more dependent on forests. Singapore’s urbanisation has led to a decrease in native plants, affecting the diet of such butterflies. Thus, intervention may be needed to manage their preferred flower resources.
The study, published online in Biological Conservation on 17 July, was conducted by Anuj Jain as part of his doctoral thesis at NUS Biological Sciences. “Butterfly species exhibit different levels of flower preferences and flower specialisation. Understanding the complex phenomenon of flower specialisation of butterflies is important as butterflies are known to be important pollinators of tropical forests. Changes in vegetation structure due to urbanisation could alter butterfly behaviour, and in turn, result in changes in native plant pollination and reproduction,” he said.
Anuj conducting his butterfly research in the field
As flower pollinators, butterflies help in the reproduction and dispersal of different types of plants, thus the study on their diet is critical. However, most research on the flower-feeding patterns of butterflies is concentrated in temperate countries.
“With massive landscape transformation that is happening in the tropics, there is a need to understand flower use by butterflies, to assess the implications on pollination and plant reproduction, as well as conservation of butterfly species,” said Associate Professor Edward Webb who supervised the study.
To address this knowledge gap in the flower-feeding patterns of tropical butterflies, Anuj worked with Assistant Professor Krushnamegh Kunte from the National Centre for Biological Sciences in Bangalore, India, and butterfly experts from the Nature Society (Singapore).
The team surveyed 62 sites in Singapore, including forested areas and urban parks, and recorded 3,092 flower visits by butterflies feeding on 149 plant species. Among the 190 butterfly species spotted, 30 fed on specific flowers.
The investigators noticed that the flower specialists had conspicuous and bigger wing spans but shorter proboscis, suggesting an evolutionary adaptation to escape predators during feeding. Flower generalists possessed longer proboscis lengths, which broadened their food choices by allowing access to nectar in deep flowers.
One butterfly critically dependent on single native flower species is the Yellow Vein Lancer (Pyroneura latoia), which feeds on flowers of the native shrub Leea indica, as shown in 74 per cent of feeding observations. The team also noted that the Lycaenidae family of butterflies, the most extinction-prone in Singapore, is the most flower-specialised.
Yellow Vein Lancer, a flower specialist, feeding on Leea indica flowers (Photo: Tea Yi Kai)
Of the 19 butterfly species that made at least 10 flower visits in both forests and urban parks, five expanded their diet in the parks housing more non-native plants compared to forested sites. This indicates that non-native flowering plants may be benefitting some butterflies by providing extra nectar resources.
The scientists proposed that habitat management for flower specialised butterflies would be important to provide their preferred native flower sources in urbanising landscapes.
See press release.
