Morphometrics and the Identification of Braunia andrieuxii and B. secunda (Hedwigiaceae, Bryopsida)

Although previous cladistic analyses revealed Braunia secunda and B. andrieuxii as two lineages and valid species, they have been considered synonyms due to morphological similarities and sympatric distribution. This study was undertaken to evaluate which morphological characters best distinguish these two species. A total of 180 specimens of B. andrieuxii and 112 of B. secunda from the U.S. and Mexico were examined for morphometric analyses. Digital images of capsules, leaves, and groups of leaf cells were used to extract 31 linear measurements. Specimens were subdivided into seven geographic groups to compare levels of variation within and between species with univariate and multivariate analyses. Most characters are similar among groups within species, except the length of the revolute leaf margin and apical and upper leaf cells, which are significantly different between species (ANOVA and MRT). Partitioned Canonical Variates Analyses on eight variables of leaf cells and seven variables of vegetative leaves identified significant Mahalanobis distances between the two species. These methods also revealed that the revolute leaf margin and upper leaf cells contribute most to the distinction between species.