10:00 AM - 10:15 AM
[BPT03-05] Do diversity patterns in clade relate to the probability of extinction of clade during a mass extinction event? -simulation study-
Keywords:mass extinction, ecosystem simulation, clade, diversity change
A number of clades that became extinct during the mass extinction at the end of the Cretaceous are known to show a decreasing trend in diversity long before the mass extinction. This was once considered one of the bases for refuting the asteroid impact theory. The relationship between diversity patterns in clades and extinction of clades during mass extinction events has been studied by analyzing the fossil record. However, the clear conclusion has not been obtained yet. One of the main reasons for this is that diversity patterns in clades cannot be shown clearly. For example, since Sloan et al. (1986) and Sheehan et al. (1991), there has been a long debate as to whether dinosaur diversity is on the decline. In recent years, there have been several reports that the apparent decrease in diversity is due to incompleteness of the fossil record (Signor & Lipps, 1982, Paul, 2005, Schultz et al. 2010). The results of statistical analysis by Wang & Dodson (2006) also indicate this. However, the results of statistical analyzes by Ballet et al. (2009) and Sakamoto et al. (2016) indicate that dinosaur diversity is on the decline. Thus, no clear conclusion has been obtained. In this study, I attempted to address this problem using computer simulations of ecosystem evolution. This is because data for all clades and all species are recorded in the course of simulations, making it possible to clearly analyze diversity patterns in clades and the extinction rate of clades during mass extinctions.
After a long enough evolution, I reduced the energy input by 85% for a short period. As a result, about 60% of animal species and clades became extinct, respectively. Species with large body were prone to go extinct. Carnivorous and omnivorous without scavenging were prone to go extinct. Clades with low species diversity are prone to extinction. These results are consistent with the fossil record. The result of simulations showed that long-term trends in species diversity within clades did not relate to the probability of extinction during a mass extinction event. I also analyzed the effect of short-term trends (incline or decline) in species diversity within clades. When the species diversity within clades became extremely low as a result of a short-term decline in species diversity, the clades were prone to go extinct. However, when comparing clades that maintained a certain level of diversity, short-term trends in species diversity within clades did not relate to the probability of extinction during a mass extinction event. However, patterns of species diversity within clades and the probability of extinction of clade during a mass extinction event were not completely unrelated. Clades surviving for a long period with low species diversity, such as living fossils, had relatively low extinction rates. In addition, clades of which center of gravity of diversity pattern was far from the time of the mass extinction were prone to go extinct.
After a long enough evolution, I reduced the energy input by 85% for a short period. As a result, about 60% of animal species and clades became extinct, respectively. Species with large body were prone to go extinct. Carnivorous and omnivorous without scavenging were prone to go extinct. Clades with low species diversity are prone to extinction. These results are consistent with the fossil record. The result of simulations showed that long-term trends in species diversity within clades did not relate to the probability of extinction during a mass extinction event. I also analyzed the effect of short-term trends (incline or decline) in species diversity within clades. When the species diversity within clades became extremely low as a result of a short-term decline in species diversity, the clades were prone to go extinct. However, when comparing clades that maintained a certain level of diversity, short-term trends in species diversity within clades did not relate to the probability of extinction during a mass extinction event. However, patterns of species diversity within clades and the probability of extinction of clade during a mass extinction event were not completely unrelated. Clades surviving for a long period with low species diversity, such as living fossils, had relatively low extinction rates. In addition, clades of which center of gravity of diversity pattern was far from the time of the mass extinction were prone to go extinct.