Mating studies, new species, and new reports of Marasmius from northern Thailand.

The mating systems operating in seven species of Marasmius collected recently in northern Thailand were determined. Marasmius cremeus belonging to sect. Sicci subsect. Siccini ser. Leonini, and Marasmius straminiceps belonging to sect. Marasmius subsect. Sicciformes are described as new species. Five members of sect. Marasmius were tetrapolar (bifactorial), viz. M. apatelius, M. guyanensis, M. nigrobrunneus, M. ruforotula, and M. straminiceps. Two members of sect. Sicci were bipolar (unifactorial), viz., M. corneri (syn. M. incarnatus) and M. cremeus. Our data support the hypothesis that the mating system is consistent within infrageneric taxa. The seven species that are herein described, illustrated, and compared with phenetically similar species represent the first reports for this genus in Thailand.