Paper 36: PATTERNS IN VASCULAR LAND PLANT DIVERSIFICATION – K. J. NIKLAS, B. H. TIFFNEY, AND A. H. KNOLL (1983)

 Peter Wilf – Commentary author  

Dr. Peter Wilf is a professor of Geosciences and an adjunct professor of biology at Penn State (University of Pennsylvania). His main research interest focus on using paleobotany to study how past environment has changed through time and how this has affect biodiversity, ecosystems and other ecological variables. From 2013-206 he was the academic editor of PloS One. He has 77 publications (Researchgate) and his most cited paper (380) was published in 2009: Phylogenetic biome conservatism on a global scale.

K. J. Niklas – Author - http://labs.plantbio.cornell.edu/niklas/

Dr. Karl Niklas is a paleobotanist (or plant evolutionist he likes to say) at Cornell University. He is interested in plant functional morphology and evolution using biomechanics and allometric analysis. His focus is in understanding plant form and function over the course of millions of years by combining physics, engineering and mathematics.

298 publications 12566 citations (ResearchGate).

B. H. Tiffney – Author

Dr. Bruce Tiffney is a paleobotanist professor of Geological Sciences at University of California Santa Barbara. He is interested in how morphology, anatomy and biogeography of land plants has changed through the fossil record. He has specialized in angiosperms, in particular fossil fruits and seeds.

51 publications and 2683 citations (ResearchGate).

A. H. Knoll – Author

Dr. Andrew Knoll is a professor of Earth and Planetary Sciences at Harvard University and Fisher Professor of Natural History. He is particularly interested in Archean and Proterozoic paleontology and biochemistry. His lab also works on early seed plant evolution and other physiological variables.

387 publications and 29933 citations (ResearchGate).

Cliff Notes of the paper:

In this paper Niklas, Tiffney and Knoll use plant fossil record to prove Sepkoski’s ideas in land plants. “Does land plant follow the same patter as marine invertebrate or they have different evolutionary associations? And if there are differences, what generated them?”

These authors were the first ones to quantify the plant-fossil record and from those observations they found four different land-plant radiations related to main morphological and reproductive changes: (a) Silurian-mid Devonian with an initial radiation of early vascular plants; (b) Devonian-Carboniferous when free sporing plants radiated; (c) late Devonian-late Paleozoic when seed plants appeared; and (d) Early Cretaceous with the radiation of angiosperms (flowering plants) [Fig. 1].

In general, the diversification of each of this four radiation groups is related to a high rate of appearance followed by a short species duration rate. However, within a group, new species appear less frequent and their duration increases through time [Fig. 2].  

This radiation is either cause by an increase in the total number of species diversity (b & d) or due to a decline of the old species from previous dominant groups (transition a-b & c-d). The authors called this second phenomena “competitive displacement” meaning that the old less specialized taxa is being displaced by the newer more specialized taxa.

Based on their findings, they concluded a very similar pattern between the evolution of land plants and Sepkoski’s evolution of marine invertebrates. The authors summarized that a “generalized pattern in the evolution of higher taxa”.

The commentary author addresses one of the main questions that came to my mind when I was reading the article: “Is this conclusion still plausible today?” As Peter Wilf points out, there are some biases (inconsistent sampling, undersampling, variation in preservation…) that would probably change this generalized pattern today. However, based on the conclusions of the paper, do you agree that the patterns observed in land plants and marine invertebrates are somewhat similar?