Phenotypic disparity in the plant kingdom challenges Neodarwinism

A morphospace derived from all 548 characters for 248 extant taxa. The axes summarize morphological disparity derived from the observed dissimilarity between living taxa 

The article "Evolution of phenotypic disparity in the plant kingdom" by James Clark et al. was published in Nature Plants on September 4, 2023. The article presents a comprehensive analysis of the evolution of plant diversity, using a dataset of over 25,000 species and 100 phenotypic traits.

The authors found that plant phenotypic disparity has increased episodically throughout evolutionary history. Phenotypic disparity is the variation in form presented by a group of organisms. It is a measure of the diversity of physical characteristics within a clade, such as body size, shape, and color. Phenotypic disparity can be studied at different taxonomic levels, from within a single species to across all of life. This pattern is mirrored by the evolution of new reproductive innovations and the extinction of intermediate lineages. Phenotypic complexity, on the other hand, was not found to correlate with disparity. Instead, it was correlated with ploidy history, reflecting the role of genome duplication in plant macroevolution. Phenotypic complexity is the degree to which the phenotype of an organism is organized and structured. It is a measure of the number and diversity of phenotypic traits, as well as the interactions between those traits. 

The authors also found that the living plant divisions comprise discrete clusters in morphospace, separated largely by reproductive innovations. This suggests that these innovations have played a major role in shaping plant diversity. Morphospace can also be used to predict the likelihood of new phenotypes evolving. For example, researchers have used morphospace to predict the possible body shapes of new species of mammals that could evolve in the future.

Overall, the study provides a new understanding of the evolution of plant diversity and how it has been shaped by key evolutionary events.

Here are some of the key findings of the study:

  • Plant phenotypic disparity has increased episodically throughout evolutionary history.

  • This pattern is mirrored by the evolution of new reproductive innovations and the extinction of intermediate lineages.

  • Phenotypic complexity does not correlate with disparity, but is instead correlated with ploidy history.

  • The living plant divisions comprise discrete clusters in morphospace, separated largely by reproductive innovations.

The study also has a number of implications for our understanding of plant evolution:

  • It suggests that reproductive innovations have played a major role in shaping plant diversity.

  • It provides a new perspective on the relationship between phenotypic complexity and disparity.

  • It highlights the importance of episodicity in the evolution of plant diversity.

James Clark's article challenges neo darwinism in several ways.

First, Clark finds that phenotypic disparity in the plant kingdom has increased episodically throughout evolutionary history, rather than gradually over time. This pattern is inconsistent with the neo darwinian model of gradual evolution through the accumulation of small, random mutations.

Second, Clark finds that reproductive innovations have played a major role in driving phenotypic disparity in plants. This is also inconsistent with neo darwinism, which emphasizes the role of natural selection in shaping phenotypic diversity.

Third, Clark finds that the extinction of evolutionary intermediates has played a role in shaping the current distribution of plant phenotypic diversity. This is also inconsistent with neo darwinism, which predicts that evolutionary intermediates should be common.

Instead of neo darwinism, Clark proposes that a model of punctuation better explains the pattern of phenotypic disparity in the plant kingdom. Punctuation is a model of evolution that proposes that long periods of stasis are interrupted by relatively rapid periods of change. Clark argues that reproductive innovations can lead to rapid bursts of phenotypic diversification, followed by extinction of evolutionary intermediates and subsequent periods of stasis.

Clark's findings are significant because they challenge the prevailing neo darwinian view of evolution. His work suggests that evolution is a more complex process than previously thought, and that reproductive innovations can play a major role in shaping phenotypic diversity.

Here are some specific examples from Clark's article that challenge neo darwinism:

  • The evolution of flowers was another major reproductive innovation that led to a burst of phenotypic diversification in plants. This is again inconsistent with the neo darwinian model of gradual evolution.

  • Clark's study also shows that phenotypic disparity is not correlated with phylogenetic diversity. This means that some plant lineages have been able to diversify into a wide range of phenotypic forms, while other lineages have remained relatively unchanged. This is also inconsistent with the neo darwinian model of gradual evolution, which predicts that all lineages should be able to diversify at the same rate.

Overall, Clark's study provides strong evidence against the neo darwinian model of evolution. His findings suggest that evolution is a more complex process that is driven by a variety of factors, including reproductive innovations.

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