Analysis of diversification histories in extinct carnivorous marsupials (Sparassodonta, Metatheria) using a Bayesian framework

TARQUINI, SERGIO DANIEL; LADEVÈZE, SANDRINE; PREVOSTI, FRANCISCO JUAN

Hammburgo

Congreso; 25th Latin-American Colloquium of Geosciences; 2019

Universität Hamburg

South America was isolated during a great time of the Cenozoic, allowing an endemic terrestrial biota to evolve. Within mammals, the carnivore guild was occupied by the Sparassodonta from the Palaeocene to the Pliocene. Moreover, from the late Miocene-Pliocene, carnivorous placentals (Carnivora) began to colonize the continent from North America, after the formation of the Isthmus of Panama. Given that, some authors proposed the ?competitive displacement? hypothesis justifying the extinction of sparassodonts by the arrival of carnivorous placentals, while others proposed an ?opportunistic replacement?. We compiled a data set of fossil occurrences for Sparassodonta and their potential competitors in South America (six families of Carnivora) collected from the literature and museums databases. All analyses were done with a Bayesian framework in the PyRate software. First, we estimated the preservation rate and the times and rates of speciation and extinction through a reversible jump Markov Chain Monte Carlo (RJMCMC). We ran 20000000 RJMCMC iterations and sampled once every 5000 to obtain posterior estimates of the parameters. Additionally we tested if the diversification dynamics of Sparassodonta may be linked with changes in body mass (using a Covar birth?death model) and in global temperature (using a birth?death model with time-varying rates). Information of body mass and temperature were obtained from the literature. Finally we assessed the effect of competition on the diversification of Sparassodonta with a Multiple Clade Diversity Dependence model. Our results show temporal changes in both speciation and extinction rates for Sparassodonta, supporting the idea that the demise of a clade is controlled by the two factors. Regarding body size there is a trend where the larger body mass in Sparassodonta appears later in their evolutionary history. Although the changes in body mass are not related to the speciation rate, they are related to the extinction rate (i.e., as the size increased, the extinction rate decreased). No significant correlations emerged between the global temperature curve and changes in diversification rates. Finally, clade competition did not affect the diversification dynamics of Sparassodonta; speciation rate fell before the dispersion of Carnivora in South America. In conclusion, these new techniques can improve our knowledge of the evolution of the taxa but more studies are required to elucidate the demise of Sparassodonta.