Abstract Detail

Modeling the processes that mediate speciation and extinction rates across plants

Pennell, Matt [1].

Why extinction estimates from extant phylogenies are so often zero.

Time-calibrated phylogenies of extant species are widely used to estimate historical speciation and extinction rates by fitting stochastic birth-death models. These approaches have long been controversial as many phylogenetic studies report zero extinction in many taxa, contradicting the high extinction rates seen in the fossil record and the fact that the majority of species ever to have existed are now extinct. To date, the causes of this discrepancy remain unresolved. Here we provide a novel and simple explanation for these zero-inflated extinction estimates, based on the recent discovery that there exist many alternative "congruent'' diversification scenarios that cannot be distinguished based solely on extant timetrees. Due to such congruencies, estimation methods tend to converge to some scenario congruent to (i.e., statistically indistinguishable from) the true diversification scenario, but not necessarily to the true diversification scenario itself. This congruent scenario may exhibit negative extinction rates, a biologically meaningless but mathematically feasible situation, in which case estimators will tend to stick to the boundary of zero extinction. Based on this explanation, we make multiple testable predictions, which we confirm using analyses of simulated trees and 121 empirical trees. In contrast to other proposed mechanisms for erroneous extinction rate estimates, our proposed mechanism specifically explains the zero-inflation of previous extinction rate estimates in the absence of detectable model violations, even for large trees. Not only do our results likely resolve a long-standing mystery in phylogenetics, they demonstrate that model congruencies can have severe consequences in practice.

1 - University Of British Columbia, Department Of Zoology, #4200-6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada

Keywords:
phylogenetics
modeling
diversification
Extinction.

Presentation Type: Colloquium Presentations
Session: C01, Modeling the processes that mediate speciation and extinction rates across plants
Location: /
Date: Monday, July 19th, 2021
Time: 1:45 PM(EDT)
Number: C01013
Abstract ID:57
Candidate for Awards:None