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

BIPPUS, ALEXANDER C.; ESCAPA, IGNACIO E.; TOMESCU, ALEXANDRU M. F.

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Año: 2018

0002-9122

PREMISE OF THE STUDY: The Polytrichaceae are a widespread and morphologically isolatedmoss lineage. Early attempts to characterize phylogenetic relationships within the familysuggested that morphology is not phylogenetically informative. Two well-characterizedfossils similar to basal and derived Polytrichaceae (Meantoinea alophosioides andEopolytrichum antiquum, respectively), are known from Cretaceous rocks. To assess thephylogenetic positions of these fossils and compare hypotheses of relationships recoveredusing molecular vs. morphological methods, we conducted a comprehensive morphologybasedphylogenetic study of Polytrichaceae.METHODS: We evaluated the phylogenetic relationships of Polytrichaceae using a dataset of 100 morphological characters (including 11 continuously varying traits codified ascontinuous characters) scored for 44 species of acrocarpous mosses and parsimony as theoptimality criterion.KEY RESULTS: Continuous characters significantly increased the resolving power of theanalyses. The overall ingroup topology was sensitive to rooting as determined by outgroupselection, with some analyses yielding results that were incongruent with those of molecularstudies. Both fossils had stable phylogenetic relationships, irrespective of outgroup sampling.CONCLUSIONS: Our results suggest that morphology is useful in resolving phylogeneticrelationships in the Polytrichaceae, if both discrete and continuous characters are used.However, our rooting experiments demonstrate that there is no superior way to root analysesand indicate that relationships within the family are best evaluated using unrooted networkswithout outgroup taxa. These rooting problems suggest that additional information is neededto understand the phylogenetic relationships of Polytrichaceae. Such additional informationcould come from fossils of stem group polytrichaceous mosses, which await discovery.