Only five species of these so-called 'flea' beetles, out of a global total of 60, had been found to date in New Caledonia, in the western Pacific. A three-year study has now enabled Spanish researchers to discover two new herbivorous beetles -- Arsipoda geographica and Arsipoda rostrata. These new beetleshold a secret -- they feed on plants that the scientists have still not found on the archipelago.
"The study, financed by the National Geographic, went some way beyond merely classifying species, and investigated the ecology of these herbivorous insects with a prodigious leaping capacity, which they use to avoid their predators," Jesús Gómez-Zurita, lead author of the study and a researcher at the Institute of Evolutionary Biology (CSIC-UPF) who is passionate about New Caledonia and collected hundreds of beetles in order to study them, said.
The researchers, from Spain and New Caledonia, used previously-developed molecular tools in order to classify the DNA sequences of the animals' diet, in particular chloroplast DNA (which is exclusive to plants). The team used plant matter remains found in the digestive tract of the insects at the time they were killed in order to extract their DNA at the same time.
According to the study, which has been published in the Journal of Natural History, this technique made it possible to discover that one of the new species, Arsipoda geographica, which measures three millimetres, feeds on a tropical plant in the mountains (Myrsinaceae), while Arsipoda isola, which is the same size, feeds on another plant (Ericaceae) in the southern jungles of the island.
"The strangest thing is that the DNA sequences of the plants are from botanical species that have still not been found on the archipelago. This provides indirect evidence of the existence of an enigmatic botanical diversity, which should be more than expected on an island with a wealth of lush vegetation," says the researcher, who has been studying beetles for 20 years.
The study, which is the first in this research line focusing on the Chrysomelidae family (known as 'leaf beetles' because they feed primarily on plants), made it possible to collect more than 2,000 beetle samples on the island of Grande Terre, compare them with other species, and carry out a phylogenetic analysis. So far, three new species have been found, two of which are described here.
New Caledonia, a still unknown territory
"The interest in New Caledonia has recently been renewed as a result of the discovery that the archipelago may have remained completely submerged over a lengthy period up until the Oligocene (more than 23.5 million years ago), when it emerged again, which would mean its fauna and flora originated much more recently than had previously been speculated," explains Gómez-Zurita.
The numerous insects and beetles on the archipelago, are great number of which are endemic, "are the great unknowns of this biota," says the biologist. "This study of their diversity and similarities without any doubt holds the keys to understanding the evolution of life in this part of the world," he adds.
The isolation of New Caledonia in the western Pacific, which became separated from Australia 70 million years ago, has led to "the evolution of some very unusual biotas that have not had any contact with the rest of the world for enormous period of time," the scientist explains.
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