A family event

Abstract

When it comes to the number of species, beetles are the winners: it is estimated that there are one to 30 million species, comprising one third of all described species. Many remain undescribed and therefore unknown to science. But with such abundance, the mere description of a new species is not necessarily a big event, but researchers, at the Natural History Museum in London and other institutes have now reported two species of beetle that represent a new genus of water beetles, the first time for 150 years. I. Ribera and colleagues at the Natural History Museum in London and institutes in Jena and Munich in Germany, report in the Proceedings of the Royal Society B (published online) a description of new beetles found living among vegetation growing on stones in rivers subject to the constant flow of water. The new beetles are members of the larger water-beetle group Hydradephaga, which comprised six current families of beetles highly modified for life in the water. The new species, from South Africa and China, could not be placed within any of the current six groups but showed some resemblance to members of an extinct group found during the Jurassic-Cretaceous period. The authors place them in a new group, Aspidytidae. The team looked at both morphological features and DNA evidence to reach their conclusion. The evolution of swimming in water beetle groups has involved significant morphological changes, including the development of a hydrodynamic shape and fringes of swimming hairs on the middle and hind limbs, most notably in the diving and whirligig beetle families which have evolved large numbers of specialist species. The diving family comprise more than 4,000 described species and the whirligig group more than 1,000 species. But the authors argue that the new species, clinging to rock vegetation, result from complex and and repeated changes in lifestyles, that have led to the secondary loss of swimming ability. Beetles have exploited a vast array of niches by largely retaining their biting mouthparts but many other aspects of their biology have evolved to adapt to particular niches. The sheer range of food from all types of vegetation to animal dung on offer to such a lifestyle is something that marks out the worldwide success of the beetles. With such global abundance, the potential for the discovery of other higher-order groups is boosted by these latest findings. It is something that researchers in many other areas of taxonomy have long since forgotten as the pressure grows on so much of the world's remaining fauna.