Populations of the desert moss Syntrichia caninervis Mitt. were sampled on a 1.5 hectare site in order to study spatial distributions of male, female, and mixed sex populations. Populations were also categorized in reference to their microhabitat (shaded versus exposed) and mapped on a coordinate grid system including prominent topographic trends. Exposed populations were found to be significantly clustered near trails and washes. Shaded populations, both mixed-sex and single-sex (female), were clumped in arrangement, but single-sex populations were more clumped than mixed-sex populations. This study provides a basis for exploring the potential mechanisms involved in the origins and maintenance of these patterns. We provide three potential explanations for these patterns: a leptokurtic hypothesis of spore dispersal, failure of the species to colonize new habitats via spores, and limitation of mixed-sex populations by the vegetative self-propagation of single-sex populations.

Key words: niche partitioning, Pottiaceae, spatial segregation, Syntrichia caninervis