DNA barcodes narrow down possible sources of introductions of an invasive banana skipper butterfly pest

CABI has led a team of scientists who have used DNA barcodes to narrow down the possible sources of introductions of an invasive banana skipper butterfly, with implications as to the threat of it spreading to Africa and tropical America.

The banana skipper, Erionota torus Evans (Lepidoptera, Hesperiidae, Hesperiinae, Erionotini) is a South-east Asian pest of banana that, in the last 60 years, has spread to the southern Philippines, Taiwan, Japan, India, Sri Lanka, Mauritius and La Réunion.

The new research, published in the journal CABI Agriculture and Bioscience, analysed a partial library of DNA barcodes from the indigenous and introduced ranges and suggests that aircraft are likely a pathway into new areas.

Gravid females may be attracted to airport lights

It is believed that gravid females may be attracted to airport lights while aircraft are being loaded at night and settling within aircraft before departure.

Indeed, it has been suggested that at least one of three separate invasions in Japan, all in the Ryukyu Islands of Okinawa and Kagoshima Prefectures, southern Japan, was unwittingly made on US military planes moving between the South Vietnam and the US Okinawa airbase during the Vietnam war.

The scientists found that based on their DNA barcodes indigenous populations can be divided into an ‘East’ group, in China and Vietnam, and a ‘West’ group in India, Nepal, Myanmar and west Malaysia.

Furthermore, within the ‘West’ group, there is a coherent ‘Malaysia’ subgroup from west Malaysia. Introduced populations in south India, La Réunion and Taiwan showed almost no variation in barcodes, suggesting they are each based on a single homogenous introduction.

They conclude that the introduced populations in Taiwan and Japan match the ‘East’ group, the introduced populations in Mauritius and La Réunion match the ‘Malaysia’ subgroup and the introduced population in south India matches the ‘West’ group.

Useful insight regarding the origin and potential pathways

Dr Matthew Cock, lead author of the research and CABI Emeritus Fellow, said, “Our study has added useful insight regarding the origin and potential pathways of introductions of E. torus in Asia and the Indian Ocean.

“We would have achieved more if larger numbers of samples and a wider geographical range of DNA barcodes had been available. Accordingly, this is a tool well worth including in future studies on introductions and pathways of alien invasive species.”

He added that the low level of replication and a limited library of barcodes from indigenous populations means that it can only be concluded with confidence that the introduced populations of E. torus in Taiwan and Japan match the ‘East’ group, the introduced populations in Mauritius and La Réunion match the ‘Malaysia’ subgroup and the introduced population in southern India matches the ‘West’ group.

The scientists say the results support earlier suggestions that the introduction to Mauritius was from west Malaysia, quite possibly on military aircraft, and the introduction to La Réunion was from Mauritius (or possibly west Malaysia).

They believe the introduction to southern India was either from north-eastern India or perhaps one of the adjacent countries, the introduction to Taiwan was from Vietnam or China (e.g. Hong Kong), the introduction to Okinawa was from Vietnam (as previously suggested) or China.

However, they say the introduction to Yonaguni Island, Japan, was from Taiwan. They were unable to obtain DNA barcodes from Sri Lanka or the Philippines to assess the likely origins of these introductions, but when DNA barcodes become available from these countries it will be easy to compare them with the barcodes reported here.

Full paper reference

Matthew J.W. Cock, Alan G. Buddie, Giovanni Cafa, Hideyuki Chiba, Athulya Girish Kizhakke, Yu-Feng Hsu and Krushnamegh Kunte, ‘DNA barcodes narrow down the possible sources of introductions of an invasive banana skipper, Erionota torus Evans (Lepidoptera, Hesperiidae)’. CABI Agriculture and Bioscience, 27 February (2025). DOI: 10.1079/ab.2025.0016

The paper can be read in full here: https://www.cabidigitallibrary.org/doi/10.1079/ab.2025.0016

CABI Agriculture and Bioscience

CABI Agriculture and Bioscience is an open access journal publishing high-quality, rigorously peer-reviewed multi-, inter- and transdisciplinary research focused on agriculture, food security, and the environment. 
 
Global agriculture faces many challenges today. How can we produce more safe, nutritious food in the face of climate change? Can we balance greater efficiencies with the need to reduce greenhouse gas emissions and protect biodiversity?  Can we meet changing market demands and yet develop more equitable economies? Can agriculture provide a livelihood and opportunities for women and young people? 
 
These problems require increasingly complex and urgent solutions from researchers and policymakers. The journal editors are committed to encouraging an inclusive culture of scientific discussion and rapid information sharing among researchers worldwide.