THE EFFECTS OF MAMMALIAN TAPHONOMY ON THE RECONSTRUCTION OF MACROEVOLUTIONARY DYNAMICS IN DEEP TIME

Geographic ranges are the fundamental unit of biogeography, and are known to possess many macroecological and -evolutionary correlates. Perhaps the best known of these is extinction risk, making range size a key factor in assessing the conservation status of modern species. Quantifying the relationship between geographic range size and extinction risk may thus offer a valuable window into predicting the consequences of ongoing global change. Simulations-based studies have thus far suggested that the preservation potential of geographic range size in the fossil record is high. However, to date these experiments have not considered differing taphonomy among species, which is thought to represent a significant source of bias. Here, we use a dataset of terrestrial mammals to test whether taphonomy affects our ability to reconstruct geographic range size in the fossil record, and correctly identify links to extinction risk. Our results illustrate that: 1) accurate detection of range size-extinction risk signals is sensitive to the inclusion of mammals with small body size, and thus emphasize the need to combine data from fossil localities preserving small mammals (e.g., microsites) with traditional macrofossil sites. 2) Extinction events that select against small-bodied mammals can create false-positive range size extinction signals. And 3) extinction events with random selectivity frequently create false positive range size-extinction risk signals, although this tendency is lessened when microsites are included. Lastly, we show that the impact of taphonomy in these geographic range size simulations contrast with those modelling the impact of mammalian taphonomy on diversity metrics where spatial turnover of species (beta diversity) is preserved with surprising fidelity. In sum, these results illustrate that our ability to reconstruct macroecological patterns over extinction events is governed by complex interactions between taphonomy, geographic range size, body size, and the locations of biogeographic hotspots. Although our results reinforce previous findings that the fidelity of the fossil record is better than anticipated, they also highlight potential biases – and the need for caution – when interpreting range size-extinction risk signals from terrestrial macrofossil records.