Haleomyces

Haleomyces is a fungal genus in the family Verrucariaceae. A monotypic genus, it contains the single species Haleomyces oropogonicola. This parasitic fungus was discovered in high-elevation forests of Mexico and Venezuela, where it lives exclusively on the beard lichen Oropogon lopezii, appearing as tiny blackish pin-points that merge into irregular dark patches on the pale-grey strands of its host. The fungus produces flask-shaped fruiting bodies containing colourless, spindle-shaped spores divided by a single cross-wall, and it gradually damages and replaces the host tissue beneath its black clusters without forming any independent body of its own.

Taxonomy

Haleomyces was erected in 1993 after David L. Hawksworth and Theodore Lee Esslinger discovered an unfamiliar fungus parasitising the beard-lichen Oropogon lopezii in high-elevation forests of Oaxaca, Mexico, and the Venezuelan Andes. They found no comparable organism among the 29 other New-World members of Oropogon, so they coined the monotypic combination Haleomyces oropogonicola—literally "dweller on Oropogon". The holotype specimen was collected at roughly 3,100 m above San Felipe Tejalapam. As a lichenicolous species it lives on, and ultimately damages, the host thallus rather than forming its own independently visible lichen body.

The genus was created because the fungus combines traits that are rarely seen together. Its minute, brown-black perithecia (flask-shaped fruit bodies) sit on the host surface and soon merge in a shared stroma; inside, thin-walled, iodine-negative asci release colourless one-septate spores.