Genetics and sexual behavior of the pheromone producer Chlamydomonas allensworthii (Chlorophyceae)

Strains of Chlamydomonas allensworthii Starr, Marner, and Jaenike isolated from 13 sites worldwide in distribution were compared to assess the congrui ty of DNA similarity, sexual behavior, and pheromone response type, The iso lates fell into two pheromone response categories. One of these included is olates of widespread distribution in the United States, and all appeared to be capable of forming zygotes inter sc. The second group was larger and mo re complex, encompassing four mating groups as defined by zygote formation, Comparison of DNA sequences (internal transcribed spacers 1 and 2 of the n uclear rDNA repeats) fully supported the same subdivision of the isolates, Both selfing and outbreeding clones were among the isolates. The possibilit y that other Volvocales species might respond to these same pheromones rema ins to be tested.