Biodiversity patterns, palaeoecology and functional diversity across the "Great Ordovician Biodiversification Event" in the Basin and Range Province, USA

• Applicant: Dr. Richard Hofmann
• Subject Area: Palaeontology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324399721

The elucidation of processes that create and maintain biodiversity has been a central question of evolutionary research ever since and attracted particular interest owing to the increasing risk of biodiversity loss due to modern global change. Palaeontological studies provide most suitable tools to reconstruct historical biodiversity trajectories in order to reveal fundamental mechanisms that underlie biodiversification. Intrinsic factors such as predation and interspecific competition are suggested to play a crucial role but especially the impact of the latter remains poorly understood. Contrasting models portray competition either as driver or inhibitor of diversification processes. Moreover, it has been suggested that the rate of speciation itself is diversity-dependent. A possible mediating factor is interspecific competition, whose impact on diversification may have changed considerable during Earth's history. In low-diverse ecosystems, low competition allows organisms to exploit a considerable habitat width. In more diversified ecosystems, competition has a much higher impact, which restricts biota to their ecological optimum. Through progressing habitat saturation, organisms are forced to adapt to adjacent habitats. Such a phase transition from unsaturated to saturated conditions explains two effects that have been observed in deep time diversification events: (1) a lag phase between the principal establishment (or survival) of higher systematic levels and within-clade diversification, as well as (2) a relatively sudden increase in diversity. Such intrinsic mechanisms may be revealed by the analysis of alpha- and beta-diversity (diversity partitioning). A perfect test case to account for the impact of intrinsic factors is provided by the "Great Ordovician Biodiversification Event" (GOBE) which represents the most significant rise in biodiversity of the whole Phanerozoic. Using quantitative palaeoecology, diversity partitioning, and functional diversity, this project aims to reveal fundamental controls on biodiversification. The Cambro-Ordovician succession of the Basin and Range Province (USA) is perfectly suited as it fulfils central criteria (continuous fossiliferous strata along an environmental gradient across the GOBE) to successfully test such questions. It will be the first study that tracks alpha- (within habitat) and beta- (between habitats) diversity by means of whole-community analysis carried out on the species level throughout this pivotal episode of marine life. The expected results will be crucial in assessing the impact of community level interactions on biodiversification events in general. It will furthermore help to expose time intervals that are characterized by anachronistic framework conditions, and thereby refining the understanding of environmental parameters and evolutionary processes in deep time.

• DFG Programme: Research Grants