Wanted dead or alive (probably dead): Stem group Polytrichaceae.

Area of Science:

• Botany and evolutionary biology
• Phylogenetics and systematic botany

Background:

• The Polytrichaceae moss family is morphologically distinct, but early studies questioned the phylogenetic informativeness of its morphology.
• Fossils like Meantoinea alophosioides and Eopolytrichum antiquum offer insights into basal and derived Polytrichaceae lineages from the Cretaceous period.

Purpose of the Study:

• To conduct a comprehensive morphology-based phylogenetic study of the Polytrichaceae.
• To assess the phylogenetic positions of Cretaceous fossils and compare molecular vs. morphological phylogenetic hypotheses.
• To evaluate the utility of morphological characters, including continuous traits, in resolving Polytrichaceae relationships.

Main Methods:

• A dataset of 100 morphological characters, including 11 continuous traits, was compiled for 44 acrocarpous moss species.
• Parsimony was employed as the optimality criterion for phylogenetic analyses.
• Phylogenetic relationships were evaluated using various outgroup samplings to test rooting sensitivity.

Main Results:

• The inclusion of continuous morphological characters significantly enhanced the resolving power of phylogenetic analyses.
• Ingroup topology proved sensitive to rooting methods, with some results diverging from molecular studies.
• Fossil taxa exhibited stable phylogenetic positions regardless of the outgroup selection.

Conclusions:

• Morphology, when incorporating both discrete and continuous characters, is valuable for resolving Polytrichaceae phylogeny.
• Rooting analyses presented challenges, indicating that unrooted networks without outgroup taxa may be optimal for evaluating relationships within the family.
• Further discoveries of stem group polytrichaceous moss fossils are needed to fully elucidate their phylogenetic history.