BEETLE BIAS: HOW SEDIMENTARY ENVIRONMENT INFLUENCES PATTERNS OF COLEOPTERAN DIVERSITY IN THE FOSSIL RECORD

Previous studies of Coleopteran (Beetle)family-level diversity through time have shown a general pattern of increasing diversity from the Permian to the Recent. Most notable is the large increase in diversity that occurs in the early Tertiary. Several authors have noted this increase and several hypotheses have been generated to explain this pattern. However, the influences of taphonomic factors on the insect fossil record are poorly understood. How well does the beetle diversity curve reflect true change in diversity? How much of this pattern is due to taphonomic artifact? To examine these questions, we have conducted a study that is based on the published literature on fossil Coleoptera.

We present updated diversity data for fossil Coleoptera and examine the type and number of depositional environments represented in each time interval, the taphonomic condition of described taxa, size characteristics and the change in species richness within deposits over time. We specifically examine the role that sedimentary environment plays in diversity and contrast beetle preservation in amber, lacustrine and lagoonal environments. The large increase in beetle diversity during the early Tertiary appears to be due to preservational artifact. Not only are there more types of depositional environments during this time interval, but the quality of these deposits in terms of insect preservation are also exceptional. There is also a distinct size bias with environment that may also affect diversity estimates for Coleoptera. Therefore, future analyses of insect diversity in the fossil record should only examine patterns within a single type of depositional regime to avoid a taphonomically biased picture of insect diversity trends over time.