NEW RECORDS AND DATA OF RHODOCOLLYBIA POPAYANICA (AGARICALES: OMPHALOTACEAE) FROM MEXICO

Rhodocollybia popayanica is described as a new record for the Mexican mycobiota in the states of Chiapas, Hidalgo, México, Michoacán and Nayarit. The studied specimens are congruent with descriptions from Colombia and Costa Rica. With this record, Mexico becomes the northernmost limit for this neotropically distributed species.

As part of an ongoing review of collybioid agarics in Mexico, the authors found specimens fitting the diagnostic characters of Rhodocollybia popayanica (Halling) Halling, until now known only from Colombia and Costa Rica (Halling, 1989;Franco-Molano et al., 2000;2010;Mata, 2002).

MATERIALS AND METHODS
All specimens were annotated in the field and examined in the laboratory following standard techniques of macromorphology and macrochemicals reactions described by Cifuentes et al. (1986).Basidiomata colors were matched with Kornerup and Wanscher (1978).
Basidiomata micromorphology was examined using light microscopy.Sections of different tissues were mounted either with 3-5% aqueous KOH solution, lactic acid or Melzer's reagent; cotton blue or phloxine were used to stain cells when needed (Largent et al., 1977).The symbol "Ǭ" represents the average of mean the length/width ratio of basidiospores.Most measurements and drawings were made using oil immersion objective at X 1250.A drawing tube was used to construct illustrations of microscopic features.
Habitat and distribution: Humicolous or on very rotten wood; in mixed Pinus-Quercus, and Mexican montane mesophytic forests, at 800-2090 meters above sea level.It occurs during the months of July to September and its edibility is unknown.

DISCUSSION
Rhodocollybia popayanica is easily distinguished by its campanulate to planoconvex pileus, which is clearly cuspidate to papillate at center.At first, basidiomata are almost white or very pale yellow but tend to develop yellow or brown stains when older.Previous descriptions (Halling, 1989;Franco-Molano et al., 2000) have reported a more yellow to brown coloration (as brown as 6C4 and at center could be in age as reddish as 7-8A3), as well as longer stipe dimensions (80 to 200 mm), but Mata (2002) found paler basidiomata with shorter stipe just like the Mexican specimens.Mata (2002) related such variations to different developmental stages and we concur with his opinion.
Rhodocollybia popayanica is similar to the R. maculata complex because of the yellowish basidiomata (Halling, 1989), but we regard its consistency as cartilaginous rather than fibrous, just like in R. butyracea.In addition, R. maculata has globose spores while R. popayanica are ellipsoid.
Rhodocollybia popayanica is now recorded from central, southwestern and southern Mexico (Chiapas, Estado de México, Hidalgo, Michoacán and Nayarit).It seems to be widely distributed in the Neotropics with Colombia and Mexico respectively as its southern and northern limits so far.