RESPONSE OF BEETLES TO GLOBAL CHANGE: THE PAST IS A CLUE TO THE FUTURE

Abstract

Fossils of beetles preserved as heads, pronota, and elytra in Pliocene, Pleistocene, and Holocene sediments are an important resource from which the historical effects of climate change and human activities on insect faunas can be examined. During the Plio-Pleistocene transition ∼2 million years ago, a diverse beetle fauna inhabited Kap Kobenhavn, northernmost Greenland. The beetle fauna inhabited a forested landscape in contrast to the polar desert of today. A significantly warmer climate also may have existed in the interior of Antarctica until Pliocene time, based on a fossil assemblage that includes fossils of beetles. During the last 2 million years of the Quaternary Period, both the northern and southern hemispheres have undergone repeated glaciations in both polar and temperate latitudes. Beetle species have responded by tracking the changing climates. Even though populations were isolated and the conditions theoretically conducive to speciation and extinction, only a few new species have been described and only a few species became extinct. Regional extinctions have been detected but these did not lead to species extinctions. Human activities during the Holocene and within historical times have produced effects in the fossil record as striking as those of climate changes. In the British Isles and Europe, clearance of old growth forests, starting in Neolithic times ∼5000 years ago, led to the reduction in habitat and the extinction or restriction of several species of beetles. Much later in the midnineteenth century, the arrival of Europeans and their cultivation practices modified the insect fauna of the American Midwest so profoundly that the event is as detectable in the fossil record as any ice age climate change. The lesson from the fossil record of insects is that with increasing human disturbance there will be more extinction of insect species.