Occupancy history influences extinction risk of fossil marine microplankton groups

Abstract.

Geographic range has long been acknowledged as an important determinant of extinction risk. The trajectory of geographic range through time, however, has not received as much scientific attention. Here, we test the role of change in geographic range – assessed by a measure of proportional occupancy of grid cells – in determining the extinction risk in four major microplankton groups: foraminifera, calcareous nannofossils, radiolarians, and diatoms. Logistic regression was used to assess the importance of standing occupancy, occupancy change, and sampling probability in the extinction risk of species. We find that while standing occupancy is a major determinant of extinction risk in all microplankton groups, change in occupancy accounts for an average of 52 % of the explanatory power of the three analyzed variables, with a maximum value of 92 %. Sampling probability was also found to be consistently informative, with an average of 6 % and a maximum value of 22 %. Our results highlight the importance of incorporating both geographic range and its change through time, as well as sampling probability, into extinction models. The ability of occupancy trajectory to help predict extinction risk underlines the necessity of paleontological data in modern conservation efforts.