Heterothallic mating systems in the Echinostelium minutum complex

Biosystematics of the myxomycete Badhamia gracilis

Sixty-four isolates that conformed to the general morphological description of Badhamia gracilis were isolated from several arid regions in the southwestern USA, northern Mexico, Puerto Rico, and the Canary Islands. These isolates were then subjected to a biosystematic study in which reproductive systems, culture characteristics, and morphology were examined. Five of the isolates were heterothallic and were divided into two separate biological species with multiple allelic mating systems: A1 consisting of three isolates (Arz 4, Arz 5, Arz 6) displaying four alleles, and A2 consisting of two isolates (NM 3, NM 4) also displaying four alleles. The remaining 59 isolates were nonheterothallic and presumably apomictic. All of the isolates had similar culture characteristics in that they had white (rarely with a yellowish tinge) plasmodia that sporulated at a relatively small size. While all of the isolates generally conformed to the standard species description, there were several variations from the norm that occurred at a high frequency. The sporotheca was often laterally flattened instead of globose or ovate, the spores generally averaged 10 μm instead of 14 μm in diam, and the capillitium often appeared physaroid instead of badhamoid. This study indicates that Badhamia gracilis is probably a widespread species complex consisting of a number of local sexual populations and numerous asexual clones that are adapted to arid conditions.