New discovery! A new species of weevil with ball-shaped back unique to Green Island, published in a world entomology journal

Text / National Museum of Natural Science

Taiwan, China has a new species of jewel weevil! In Taiwan, China, jewel weevils (genus Pachyrhynchus) are distributed only on two small islands, Lanyu and Green Island, and five of them are protected species (the large round-spotted jewel weevil, the small round-spotted jewel weevil, the striped jewel weevil, the broken-striped jewel weevil and the white-spotted jewel weevil). Only the white-spotted jewel weevil is absent from Green Island; the other species are all shared by the two islands.

However, in a study jointly published recently by the Department of Life Science of National Taiwan Normal University and the National Museum of Natural Science, a striped jewel weevil found only on Green Island was discovered, and the results have been published in the world-renowned journal Systematic Entomology.

The Green Island striped jewel weevil has a shorter, rounder abdomen; on the ventral side near the front end there is only one green stripe, and near the rear end there is only one stripe, or there are round spots on the elytra (at the red arrow in the lower right figure); whereas the Lanyu striped jewel weevil often has a thicker line or two joined lines on the ventral side near the front end, and one to two thin lines on the elytra near the rear end (at the red arrow in the lower left figure).

NTNU and the National Museum of Natural Science join forces to discover a new species, published in a world-renowned journal

Insects of the jewel weevil group are mainly distributed on the islands of the Philippines, and their bodies bear extremely bright and diverse markings, so they have long been one of the most popular groups on the insect specimen market. From Luzon northward all the way to Lanyu and Green Island, this chain of islands happens to be one of the places with the highest endemism of jewel weevils.

The research team initially studied the dispersal and evolution of jewel weevils among the islands; through DNA research, they unexpectedly found that the two populations on Green Island and Lanyu that had previously both been classified as the "striped jewel weevil" had extremely different genetic variation.

Therefore, Chen Yen-Ting of NTNU continued from the preliminary genetic findings and began a series of extremely meticulous analyses, also cooperating with Dr. Huang Wen-Shan, Dr. Cheng Ming-Lun and Dr. Tseng Hui-Yun of the National Museum of Natural Science and teacher Su Yung-Chao of Kaohsiung Medical University and others, and formally elevated the Green Island striped jewel weevil to a new species, the Green Island striped jewel weevil (Pachyrhynchus jitanasaius), published in the world-renowned journal Systematic Entomology.

The diversity of jewel weevils is underestimated and deserves to be treasured and protected

The National Museum of Natural Science stated that describing a new species may not be a very special event for many taxonomists, but this study reached its conclusion on species delimitation only through integrated comparison at multiple levels, including genetics, morphology and ecology. Some features overlap to a certain degree between individuals of the two islands, but statistically there is still significant support that the two islands represent different species. An analytical framework integrating different data allows us to delimit species with more evidence and a broader perspective.

Many island species, because they are isolated by the ocean, are more likely to form different species on islands if their own mobility is poor (for example, jewel weevils, which cannot fly). From this study we can see that the diversity of jewel weevils is underestimated, and on the two small islands of Lanyu and Green Island in Taiwan, China, there are so many endemic species of jewel weevils, distributed only on islands of 47 and 16 square kilometers, which are very much worth our treasuring and protecting.