Insect Diversity Has Remained Relatively Constant Over Last 125 Million Years

Insects are astonishingly diverse, accounting for nearly three-quarters of all named animal species living today, and their diversity is widely thought to have increased steadily over evolutionary time. A new study, however, finds that insect diversity actually has not changed much over the past 125 million years. It's not that no new insects have evolved. Rather, as new insects have evolved, others have gone extinct, leaving the overall diversity relatively unchanged, according to paleontologist Matthew Clapham, Ph.D., Associate Professor of Earth and Planetary Sciences at UC Santa Cruz (UCSC), whose team published the new findings online on February 3, 2016 in Proceedings of the Royal Society B: Biological Sciences. The article is titled “Ancient Origin of High Taxonomic Richness Among Insects.” Previous studies of how insect diversity has changed over time used methods that artificially inflate the relative richness of younger (more recent) time intervals, Dr. Clapham said. These studies, as well as Dr. Clapham's, looked at the richness of the fossil record with respect to insect families, a broader taxonomic category than species and genus. The earlier studies were based on the first and last appearances of each family in the fossil record, and if there were still insects in that family living today its range was extended to the present. "The problem is that the range we see in the fossil record is always smaller than the real range, because insects don't fossilize very well--they don't have bones or shells," Dr. Clapham explained. "By extending the range of extant families to the present, you increase diversity toward the present day. It's a known bias called 'the pull of the recent.'" To avoid that bias, the Dr.
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