Surviving ancestors, hard polytomies, and seed plant evolution.

Area of Science:

• Evolutionary Biology
• Phylogenetics
• Paleobotany

Background:

• Forty years of phylogenetic analysis have not resolved relationships among major seed plant groups.
• The fossil record indicates more extinct seed plant groups than extant ones, with potential survival of ancient ancestors.
• Traditional phylogenetic methods may be insufficient for complex evolutionary histories.

Purpose of the Study:

• To reanalyze morphological data for seed plant relationships using novel visualization techniques.
• To explore the utility of networks and Romerograms in depicting phylogenetic uncertainty and ancestral lineages.
• To challenge the limitations of strictly dichotomous tree representations in phylogenetics.

Main Methods:

• Reanalysis of morphological matrices for seed plants.
• Application of network visualizations to display incompatible phylogenetic signals.
• Utilized Romerograms (spindle diagrams) to represent alternative relationships and ancestral survival.
• Simulated ancestral data to test network efficacy in identifying potential ancestors.

Main Results:

• Networks effectively display conflicting phylogenetic signals within seed plant data.
• Romerograms provide a heuristic method for visualizing complex evolutionary hypotheses, including budding speciation and surviving ancestors.
• Simulated ancestor experiments suggest networks can help pinpoint surviving lineages.
• The study highlights limitations of focusing solely on sister group identification in cladograms.

Conclusions:

• Novel visualization tools, networks and Romerograms, offer promising approaches to resolve seed plant phylogeny.
• Overcoming the impasse in seed plant phylogenetics requires broadening data visualization methods beyond dichotomous trees.
• Further research into identifying true evolutionary polytomies is warranted, aided by advanced visualization techniques.