Evolutionarily distinct “living fossils” require both lower speciation and lower extinction rates

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Title: Evolutionarily distinct “living fossils” require both lower speciation and lower extinction rates
Author(s): Bennett
Sutton, MD
Turvey, ST
Item Type: Journal Article
Abstract: As a label for a distinct category of life, ‘living fossil’ is controversial. The term has multiple definitions and it is unclear whether the label can be genuinely used to delimit biodiversity. Even taking a purely phylogenetic perspective where a proxy for the living fossil is evolutionary distinctness (ED), an inconsistency arises: does it refer to “dead-end” lineages doomed to extinction or “panchronic” lineages that survive through multiple epochs? Recent tree-growth model studies indicate that speciation rates must have been unequally distributed between species in the past to produce the shape of the tree of life. Although an uneven distribution of speciation rates may create the possibility for a distinct group of living fossil lineages, such a grouping could only be considered genuine if extinction rates also show a consistent pattern, be it indicative of dead-end or panchronic lineages. To determine whether extinction rates also show an unequal distribution, we developed a tree-growth model where the probability of speciation and extinction is a function of a tip’s ED. We simulated 1,000s of trees where the ED function for a tip is randomly and independently determined for speciation and extinction rates. We find that simulations where the most evolutionarily distinct tips have lower rates of speciation and extinction produce phylogenetic trees closest in shape to empirical trees. This implies that a distinct set of lineages with reduced rates of diversification, indicative of a panchronic definition, is required to create the shape of the tree of life.
Publication Date: 1-Dec-2017
Date of Acceptance: 7-Aug-2016
URI: http://hdl.handle.net/10044/1/38813
ISSN: 0094-8373
Publisher: Paleontological Society
Journal / Book Title: Paleobiology
Keywords: Paleontology
0403 Geology
0602 Ecology
0603 Evolutionary Biology
Publication Status: Accepted
Appears in Collections:Faculty of Engineering
Earth Science and Engineering

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