Reproductive Systems, Morphology, and Genetical Diversity in Didymium Iridis (Myxomycetes)

ABSTRACT

Of 44 Didymium iridis isolates examined, 12 are heterothallic and 32 are nonheterothallic (presumptively apomictic). Isolates belonging to the two reproductive systems are essentially indistinguishable and therefore constitute a single morphospecies. There is a considerable amount of genetical variability among isolates studied. For example, heterothallics are divisible into three breeding groups whose isozyme patterns indicate they have diverged genetically from one another. Nonheterothallics do not interbreed with heterothallics or among themselves, and their isozyme patterns indicate divergence from one another as well as from all heterothallics. Thus, D. iridis is partitioned into many “biological species.” The evolutionary relationships of reproductive systems and their probable consequences for myxomycete speciation are discussed.

Key Words:

• reproductive systems
• enzyme polymorphism
• heterothallism
• apomixis