Hedenäs, L. & I. Bisang. Are morphology and environment correlated with male dwarfism in pleurocarpous mosses?

Arctoa (2015) 24: 362-374

doi: 10.15298/arctoa.24.29

Dwarf males in mosses are restricted to certain lineages and have been proposed to be associated with epiphytism and subtropical environments. Here we explore which morphological and environmental characteristics are associated with male dwarfism in a set of 528 pleurocarpous mosses that represent the different lineages, habitats, and climatic conditions found in the world. We evaluate differences in frequencies of states for 48 morphological characters and for occurrences in different environments among species that are monoicous, dioicous without dwarf males, and dioicous with obligate or facultative dwarf males. An ambiguous picture emerged regarding which morphological characters or environmental parameters correlate with male dwarfism, indicating that dwarf males evolved in phylogenetically widely spread groups of pleurocarpous mosses that are not characterized by common characters or environments. Dioicous species with dwarf males were correlated with broad and imbricate leaves, short and wide marginal leaf cells, differentiated, but not inflated alar cells that relatively often consist of more than one cell layer, and patent or recurved upper portions of the inner perichaetial leaves. Such species were also more frequent than expected in temperate montane environments and in non-wetland habitats. Further studies of the evolution of dwarf males among (pleurocarpous) mosses should in a first step focus on these characters and environments. Differences between monoicous species and the two dioicous categories were numerous, including 18 characters between monoicous and dioicous species with dwarf males and 17 between monoicous and dioicous ones lacking dwarf males. Species with dwarf males were thus not more similar to monoicous than to dioicous species lacking dwarf males despite that they are sometimes called ‘pseudautoicous’.