Introduction
The genus Agaricus L. includes saprotrophic fungi characterized by free lamellae with brown spores, an annulate stipe, suprapellis cutis-like and cheilocystidia without capitulate apex. Its species can present nutraceutical properties of great interest. Thus far (July 2019), more than 500 taxa have been described (Chen et al., 2019), distributed in Africa, America, Asia, Australia and Europe. This number is constantly increasing since current research is focused on the identification of species using morphological and molecular data, and many of these studies were conducted in the tropical zones of Asia and America (Zhao et al., 2016; Parra et al., 2018). The last update of the genus in Mexico was carried out in a preliminary study by Mata et al. (2011), in which they recorded 32 species from 25 states. An inventory of the Agaricus species so far reported from Mexico is important because it provides a starting point for understanding the diversity, ecology, systematics and management of Agaricus species in the country.
Materials and methods
An exhaustive bibliographic review from original sources was conducted to compile a list including all published records of the genus Agaricus in Mexico to the present day. A table was constructed including the name of the species, and its available information in the literature (use, description, key, illustration, DNA sequence on Genbank, vegetation type, geographical distribution in Mexico and herbaria where the specimens are preserved when a voucher was deposited). The taxonomic arrangement of the species followed the classification of Zhao et al. (2016) and the vegetation types followed the classification of Rzedowski (2006). The nomenclatural status of each name and its synonymy follows Parra (2008, 2013). For the names not treated by this author, the nomenclatural databases Index Fungorum (http://www.indexfungorum.org) and MycoBank (http://www.mycobank.org) were consulted. Finally, a key to the subgenera and sections of the genus known to Mexico was included.
Results
A total of 53 validly published names of the genus Agaricus have been cited for Mexico in 122 works conducted over a period of 123 years, with A. campestris being the first taxon recorded (Patouillard and Harriot, 1896). The total of cited species (Table 1) corresponds to approximately 10 % of the worldwide diversity. Vouchers from the records have been deposited in more than 20 institutional herbaria, mainly ENCB, FCME, MEXU and XAL, being the last one the only with holotypes (see Table 1, on the “voucher” column). Species are spread across 28 states, of which Veracruz presents the greatest species richness (Figure 1). The species are classified in 6 subgenera and 10 sections. Most of the species belong to Agaricus sect. Arvenses, followed by A. sect. Xanthodermatei (11 and 9 taxa, respectively, Figure 2). They are associated with 15 vegetation types (Figure 3), although they also grow in grazing pastures, cultivated areas and urban zones. They are distributed mainly in the cloud forest (18 species); however, an important diversity was also noted in the temperate zones of the country, particularly in the pineoak forests (16 species), where the highest number of edible species are found together with urban zones (16 species). Agaricus sylvaticus is the most common species, being cited from 21 states and associated with 12 vegetation types, although Mexican samples of this species have never been sequenced. To date, Agaricus guzmanii, A. tlaxcalensis, A. tollocanensis and A. xuchilensis are endemic species that were described from Mexico. Agaricus tephrolepidus was originally described also from the Dominican Republic (Figure 4). Only from eight of the 53 taxa DNA sequences are available (Figure 5 and is indicated under “available information” (MD) in Table 1).
Valid name | Uses | Available information | Voucher | Vegetation Type | States | References | |
Agaricus [subg. Agaricus] sect. Agaricus | Agaricus altipes (F.H. Møller) F.H. Møller | E | D | - | 11 | 10, 14 | 16 [as A. aestivalis], 69 |
A. campestris L. : Fr. | E | D, I, K | + | 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 |
2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 22, 24, 25, 26, 28 |
1, 2, 3, 4, 5, 7, 10, 12, 18, 20, 21, 22, 23, 25, 27, 28, 32, 34, 36, 39, 40, 42, 44, 47, 48, 49, 51, 52, 54, 61, 63, 64, 65, 67, 69, 71, 76, 79, 85* [as Psalliota campestris], 90, 96, 99, 100, 101, 103, 104, 105, 106, 107, 108, 110, 112, 114, 115, 121, 122 |
|
A. langei (F.H. Møller) F.H. Møller | E | D, I, K | + | 11, 13, 17 | 2, 10, 11 | 5, 23, 35 [all as A. fuscofibrillosus] |
|
A. lividonitidus F.H. Møller | - | - | - | - | 21 | 69 | |
A. porphyrocephalus F.H. Møller | - | - | + | 11 | 12 | 51, 53 [as A. porphyreus], 69, 105 |
|
A. porosporus Heinem. | - | - | - | - | 20 | 69 | |
A. solidipes Peck | E* | - | + | 11 | 5, 22 | 58, 69, 93 | |
A. [subg. Flavoagaricus] sect. Arvenses | A. abruptibulbus Peck | E | D, I, K | - | - | 12, 18 | 51, 62, 63, 67, 110 |
A. albolutescens Zeller | - | D, I | - | - | 25 | 67 | |
A. arvensis Schaeff. | E | D, I, K | + | 3, 5, 6, 7, 8, 10, 11, 13, 16, 17, 18 |
2, 5, 6, 8, 11, 12, 14, 18, 19, 22, 25, 26 |
3, 23, 39, 40, 44, 53, 54, 55, 58, 59, 60, 61, 62, 63, 69 [as A. nivescens], 70, 73 [as A. nivescens], 76, 90, 93, 105, 109*, 121, 122 |
|
A. augustus Fr. | E | D, I, K | + | 1, 2, 3, 5, 10, 11, 13 |
4, 5, 6, 8, 10, 11, 12, 13, 14, 18, 24, 25, 26 |
13, 16, 18, 20, 23, 25, 27, 37, 40, 41, 44, 50, 54, 64, 67, 69, 70, 71, 72, 90, 95, 100, 119, 120, 122 |
|
A. bambusigenus Berk. & M. A. Curtis | - | - | - | - | 17 | 109* | |
A. crocodilinus Murrill | - | - | - | 1, 13 | 6, 19 | 69, 122 | |
A. essettei Bon | E | D, I, K | + | 11, 16 | 10, 13, 22 | 16, 35, 93 | |
A. osecanus Pilát | E | D, I | + | 18 | 18 | 67, 69, 110, 115 | |
A. subrufescens Peck | E, M* | D, I, MD | + | 3 | 6, 8, 18, 26 | 67, 69, 110, 116 | |
A. sylvicola (Vittad.) Lév. | E | D, I, K | + | 1, 2, 3, 7, 8, 10, 11, 12, 13, 14, 15, 18 |
1, 2, 5, 6, 7, 8, 10, 11, 12, 13, 14, 17, 18, 19, 23, 26 |
2, 3, 4, 9, 23, 35, 44, 50, 51, 52, 54, 58*, 59, 60, 61, 64, 66, 70, 76, 79, 82, 99, 100, 101, 107, 114, 121 |
|
A. trinitatensis Baker & Dale | - | - | - | - | 20, 27 | 14, 46, 69 | |
A. [subg. Minores] sect. Minores | A. aridicola Geml, Geyser & Royse ex Mateos, J. Morales, J. Muñoz, Rey & Tovar | - | D, I | + | 4 | 2, 3, 5, 22 | 19 [as Gyrophragmium dunalii], 80, 89 [as G. dunalii], 91 [as G. dunalii] |
A. comtulus Fr. | E | D, I, K | + | 3, 10, 18 | 10, 26 | 35, 70 | |
A. purpurellus (F.H. Møller) F.H. Møller | E* | - | - | - | 20 | 14, 69 | |
A. brunneolus (J.E. Lange) Pilát | - | D, I, K | + | 3, 11 | 6, 10, 11 | 35 [as A. xantholepis], 113 [as A. purpurascens] |
|
A. semotus Fr. | E, NE | D, I, K | + | 3, 16 | 8, 10, 14, 26 | 35, 70 | |
A. singeri Heinem. | E* | - | - | - | 20 | 14, 69 | |
A. [subg. Minoriopsis] sect. Minoriopsis | A. globocystidia- tus Drewinski & M. A. Neves | - | MD | + | 3 | 26 | 15 |
A. guzmanii Linda J. Chen & G. Mata | - | MD | +(H) | 3 | 26 | 15 | |
A. [subg. Pseudochitonia] sect. Bivelares | A. bisporus (J.E. Lange) Imbach | E | D, I, MD | + | 5, 6, 8, 18 | 1, 5, 6, 7, 8, 12, 14, 18, 23, 25, 26 |
51, 53, 61, 62 [as A. bispora], 63 [as
A. bispora], 67 [as “A.
hortensis”], 68, 69, 83 [as A. brunnescens], 100, 110 [as “A. hortensis”], 122 |
A. bitorquis (Quél.) Sacc. | E | D,I,K | + | 5, 7, 8, 9, 13, 18 | 2, 6, 11, 12, 14, 18 |
5, 23, 37, 40 [as A. rodmanii], 44, 51, 67,
69, 110, 122 |
|
A. subperonatus (J.E. Lange) Sing. | E | D,I,K | + | 5, 8, 9, 11, 18 | 6, 8, 10, 12 | 35, 44, 51, 53, 69, 122 | |
A. tlaxcalensis Callac & Mata | - | D, I, MD | + | 6 | 25 | 56*, 69 | |
A. [subg. Pseudochitonia] sect. Chitonioides | A. bernardi Quél. | E* | - | + | 18 | 6 | 90 [as A. bernardii] |
A. pearsonii Bon & Boisselet | - | - | - | - | 26 | 24 [as A. volvatus Pers.] | |
A. [subg. Pseudochitonia] sect. Hondenses | A. phaeolepido- tus (F.H. Møller) F.H. Møller | NE | D,I,K | + | 3, 10, 16 | 8, 10, 14, 26 | 35, 70 |
A. [subg. Pseudochitonia] sect. Sanguinolenti | A. benesii (Pilát) Pilát | E, NE | D,I,K | + | 3, 10, 11,13 | 8, 10, 14 | 16 [as A. maiusculus], 35 [as A. squamulifer], 69 |
A. benzodorus Heinem. & Goos.-Font. | - | - | - | - | 20 | 14, 45, 69 | |
A. sylvaticus Schaeff. | E, NE | D,I,K | + | 1, 3, 5, 6, 7, 10, 11, 13, 15, 16, 17, 18 |
1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 18, 19, 23, 24, 25, 26 |
5, 9, 12, 17, 18, 22, 23, 26, 27, 28, 30, 31, 35, 38, 41, 44, 50, 51, 52, 54, 55, 58*, 59, 60, 64, 66, 69, 70, 81, 82, 86, 87, 91, 98, 102, 107, 111, 114, 115, 117, 118, 119, 120, 121, 122 |
|
A. [subg. Pseudochitonia] sect. Xanthodermatei | A. californicus Peck | - | D, MD | - | 6, 13 | 2, 25, 26 | 5, 57*, 69 |
A. endoxanthus Berk. & Broome | NE* | - | - | - | 20 | 14, 69 | |
A. iodoformicus Speg. | - | - | - | - | 12 | 51 | |
A. moelleri Wasser | E, NE | D,I,K | + | 3, 8, 10, 13, 16 | 6, 8, 10, 13, 14, 17, 25, 26 |
4 [as A. meleagris], 16 [as A.
praeclaresquamosus], 33, 35 [as A. praeclaresquamosus], 69, 90 [as A. meleagris] |
|
A. placomyces Peck | E, NE | D,I,K | + | 1, 3, 8, 9, 10, 11, 13, 15, 17 |
6, 7, 8, 9, 11, 12, 13, 14, 17, 18, 19, 24, 25, 26, 28 |
1, 11, 17, 18, 20, 23, 27, 38, 40, 41, 44, 49, 51, 52, 53, 54, 59, 60, 61, 64, 69, 88, 90, 99, 105, 113, 115, 121, 122 |
|
A. tephrolepidus L. A. Parra, C. Billete, Angelini, G. Mata & Callac | - | D, I, MD | + | 3 | 26 | 84* | |
A. tollocanensis Callac & Mata | - | D, I, MD | +(H) | 6, 18 | 8, 25 | 8*, 69 | |
A. [subg. Pseudochitonia] sect. Xanthodermatei | A. volvatulus Heinem. & Goos.-Font. | - | D, I | + | 3 | 26 | 6, 11, 69 |
A. xanthodermus Genev. | M*, NE | D, I, K | + | 3, 5, 7, 8, 9, 11, 13, 16, 17, 18 |
2, 5, 6, 8, 10, 12, 13, 18, 20, 22, 24, 26 |
5, 14, 21, 25, 27, 35 [as A.
xanthoderma], 40, 44, 51, 53, 55 [as A. xanthoderma], 62 [as A. xanthoderma], 63, 64, 69, 70, 90, 92 [as A. xanthoderma], 93, 94, 97, 105, 106, 108, 111, 122 |
|
A. [subg. Spissicaules] sect. Subrutilescentes | A. impudicus (Rea) Pilát | E | D, I, K | + | 3, 10, 13 | 4, 7, 8, 10, 13, 26 | 17, 35, 51 |
A. subrutilescens (Kauffman) Hotson & Stuntz | E | D, I | + | 3, 10, 11 | 6, 8, 13, 14, 26 | 54, 64, 69, 70 | |
A. variegans (F.H. Møller) Pilát | E* | - | + | 16 | 12 | 53 [as A. variegatus] |
|
Incertae sedis | A. deserticola Moreno, Esqueda y Lizárraga | - | D, I | + | 7, 8, 13, 15, 18 | 2, 5, 22 | 5 [as A. texensis], 74 [as A. texensis], 75, 80 [as A. texensis] |
A. martinezianus Heinem. | E | D, I, K | + | 8, 16, 17 | 12 | 44, 47, 51, 53 [all as A. volvatus A. T. Martínez] |
|
A. pratensis Scop. | - | D | - | - | 14 | 43, 78 | |
A. robustissimus (Panizzi) Heinem. | - | D, I | - | - | 18 | 67 | |
A. xuchilensis Murrill | - | D | - | 18 | 26 | 43, 77 |
Uses: E = edible; M = medicinal; NE = not edible.
Available information: K = with key; D = with description; MD = with molecular data; I: with illustration or photograph.
Voucher: + = yes; +(H) = Holotype in herbarium. − = no data
States: 1. Aguascalientes, 2. Baja California, 3. Baja California Sur, 4. Chiapas, 5. Chihuahua, 6. Ciudad de México, 7. Durango, 8, Estado de México, 9.Guanajuato, 10. Guerrero, 11. Hidalgo, 12. Jalisco, 13. Michoacán, 14. Morelos, 15. Nayarit, 16. Nuevo León, 17. Oaxaca, 18. Puebla, 19. Querétaro,
20. Quintana Roo, 21 San Luis Potosí. 22. Sonora, 23. Tabasco, 24. Tamaulipas, 25. Tlaxcala, 26. Veracruz, 27. Yucatán, 28. Zacatecas; − = no location. Vegetation type: 1: Abies forests; 2: Alnus forests; 3: Cloud forest; 4: Coastal dunes; 5: Crops; 6: Cupressus; 7: Desert; 8: Grassland; 9: Grazing pastures; 10: Pinus forests; 11: Pinus-Quercus forests; 12: Prunus; 13: Quercus forests; 14: Salix; 15: Thorn forests; 16: Tropical deciduous forests; 17: Tropical evergreen forests; 18: Urban zones; − = no data.
References: 1. Acosta & Guzmán, 1984. 2. Aroche et al., 1984. 3. Ayala & Guzmán, 1984. 4. Ayala & Ochoa, 1998. 5. Ayala et al., 2015. 6. Bandala & Montoya, 1993. 7. Burrola et al., 2012. 8. Callac & Mata, 2004. 9. Capello-García & Hernández-Trejo, 1990. 10. Chacón & Guzmán, 1984. 11. Chacón & Guzmán, 1997. 12. Chanona et al., 2007. 13. Chávez-León et al., 2009. 14. Chay-Casanova & Medel, 2000. 15. Chen et al., 2019. 16. Cifuentes et al., 1993. 17. Cifuentes et al., 1990. 18. Díaz-Barriga, 1992. 19. Esqueda et al., 2012. 20. Estrada-Martínez et al., 2009. 21. Estrada-Torres & Aroche, 1987. 22. Fierros & Guzmán-Dávalos, 1997. 23. Frutis & Guzmán, 1983. 24. Frutis & Pinzón-Picaseño, 1997. 25. Gándara et al., 2014. 26. García et al., 2014. 27. García-Jiménez & Valenzuela, 2005. 28. Garibay-Orijel, 2009. 29. Garibay-Orijel et al., 2006. 30. Garza, 1986. 31. Garza et al., 1985. 32. Gispert et al., 1984. 33. Gómez-Reyes, 2017. 34. González, 1982. 35. Gutiérrez-Ruiz & Cifuentes, 1990. 36. Guzmán, 1958. 37. Guzmán, 1961. 38. Guzmán, 1966. 39. Guzmán, 1969. 40. Guzmán, 1970. 41. Guzmán, 1972a. 42. Guzmán, 1972b. 43. Guzmán, 1975. 44. Guzmán, 1977. 45. Guzmán, 1983. 46. Guzmán, 1986. 47. Guzmán & García-Saucedo, 1973. 48. Guzmán & Johnson, 1974. 49. Guzmán & Vela-Gálvez, 1960. 50. Guzmán & Villarreal, 1984. 51. Guzmán-Dávalos & Fragoza, 1995. 52. Guzmán-Dávalos & Guzmán, 1979. 53. Guzmán-Dávalos et al., 1983. 54. Herrera & Guzmán, 1961. 55. Herrera et al., 2006. 56. Kerrigan et al., 2008. 57. Kerrigan et al., 2005. 58. Laferrière & Gilbertson, 1992. 59. Landeros et al., 2006. 60. León & Guzmán, 1980. 61. López et al., 1985. 62. Manzi, 1976. 63. Manzi, 1978. 64. Mapes et al., 1981. 65. Martín del Campo, 1968. 66. Martínez-Alfaro et al., 1983. 67. Martínez-Carrera et al., 2001. 68. Mata et al., 2016. 69. Mata et al., 2011. 70. Medel et al., 2015. 71. Montoya et al., 2004. 72. Montoya et al., 2014. 73. Mora & Guzmán, 1983. 74. Moreno et al., 2007. 75. Moreno et al., 2010. 76. Moreno-Fuentes et al., 1994. 77. Murrill, 1918. 78. Murrill, 1922. 79. Nava-Mora & Valenzuela, 1997. 80. Ochoa & Moreno, 2006. 81. Padilla-Velarde et al., 2016. 82. Pardavé-Díaz, 1993. 83. Pardavé-Díaz et al., 2012. 84. Parra et al., 2018. 85. Patouillard & Harriot, 1896. 86. Pérez-Moreno & Villarreal, 1988. 87. Pérez-Moreno & Villarreal, 1989. 88. Pérez-Silva, 1959. 89. Pérez-Silva & Aguirre-Acosta, 1986a. 90. Pérez-Silva & Aguirre-Acosta, 1986b. 91. Pérez-Silva & León de la Luz, 1997. 92. Pérez-Silva et al., 2008. 93. Pérez-Silva et al., 2006. 94. Pérez-Silva et al., 1970 95. Pérez-Silva et al., 2011a. 96. Pérez-Silva et al., 2011b. 97. Pérez-Silva et al., 1992. 98. Portugal et al., 1985. 99. Quintos et al., 1984. 100. Quiñones-Martínez & Garza-Ocaña, 2015. 101. Reygadas et al., 1995. 102. Robles-Porras et al., 2006. 103. Rodríguez et al., 2002. 104. Rodríguez et al., 2000. 105. Rodríguez et al., 2010. 106. Rodríguez-Alcántar et al., 2018. 107. Rodríguez-Scherzer & Guzmán-Dávalos, 1984. 108. Salvador-Vázquez & Guzmán-Dávalos, 1988. 109. Singer, 1957. 110. Sobal et al., 2007. 111. Téllez-Bañuelos et al., 1988. 112. Terríquez et al., 2017. 113. Valenzuela et al., 2004. 114. Varela & Cifuentes, 1979. 115. Vázquez-Mendoza & Valenzuela-Garza, 2010. 116. Velázquez-Narváez et al., 2018. 117. Villarreal, 1987. 118. Villarreal & Guzmán, 1985. 119. Villarreal & Guzmán, 1986a. 120. Villarreal & Guzmán, 1986b. 121. Welden & Guzmán, 1978. 122. Zarco, 1986.
*Data from foreign literature
Nomenclatural comments
In order to contribute to nomenclatural stability, and according to the provisions of the current International Code of Nomenclature-Shenzhen Code (Turland et al., 2018), the following aspects of the names of the species recorded for Mexico have been reviewed: A.- its exclusion of the catalogue because the species does not belong to the genus Agaricus in the current sense or it was invalidly published, B.- its status as doubtful name, C.- its synonyms, D.- the correct spelling of its epithet.
A.- Excluded names Species belonging to other genera
Agaricus cretaceus Bull., described from México city (Mata et al., 2011) is excluded because, judging from Bulliard’s original plate, it depicts a Leucocoprinus species.
Agaricus yucatanensis Ellis & Everh., described from Yucatán (Guzmán, 1975), is excluded because its type specimen deposited in FH was examined by one of the authors (R. Medel), who verified that this taxon does not belong to the genus Agaricus. It very likely belongs to a Leucocoprinus species.
Agaricus quinquepartitus L., recorded from Michoacán and A. umbelliferus L. (as A. umbellifer Scop.) recorded from México City (Pérez-Silva et al., 2011b), are also excluded because according to the mycological literature they were combined as Tricholoma quinquepartitus L. (Gillet) and Lichenomphalia umbellifera (L.) Redhead, Lutzoni, Moncalvo & Vilgalys respectively.
Invalidly published names
The name Agaricus combonicusManzi from Jalisco (Manzi, 1978), was invalidly published because no Latin description or diagnosis was provided (Art. 39.1 of the ICN). Agaricus hortensis (J.E. Lange) Pilát (as A. hortensis (Cooke) Pilát) from Puebla (Martínez Carrera et al., 2001), is a later isonym of A. hortensis (J.E. Lange) Imai without nomenclatural status (Art. 6.3, Note 2). Agaricus aff. dennisii of Quintana Roo (Chay-Casanova and Medel, 2000) is a provisional name, the final identification of which is still unknown.
B.- Doubtful names
Agaricus lividonitidus F.H. Møller, A. pratensis Scop., A. robustissimus (Panizzi) Heinem. (mentioned as A. robustissimus Panizzi) and A. semotus Fr. are doubtful names (Parra, 2013), but we carried them in the catalogue because they are not invalidly published. These four names should not be used because from their original descriptions it is not possible to get an accurate identification. An extreme case is A. robustissimus, its original description only included a short sentence with measurements from the pileus, lamellae and stipe and no illustration was provided. However, the specimens assigned to these names, if extant, should be carefully studied to determine, if possible, their identity.
D.- Corrected epithets
The epithet bernardii was corrected to bernardi, its original spelling (Parra, 2013: 1130, 1136), as it is correct according to the Art. 60, Rec. 60C.2.
The original epithet in A. martineziensis Heinem. (a new name for the illegitimate A. volvatus A.T. Martínez) was corrected to A. martinezianus Heinem. in accordance with Art. 60.8(c) and its example 19.
The epithet in A. xanthoderma (a name used in some works) was corrected to xanthodermus, its original spelling (Parra, 2013: 162, 180), as it is correct according to the Art. 23.1 and 23.5.
Key to Agaricus L. subgenera and sections known to Mexico1
-
1.- Schaeffer’s reaction in unspoiled areas, immediately and strongly positive, odour of the pileus margin when rubbed, strongly of the anise or bitter almonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 2
1.- Schaeffer’s reaction in unspoiled areas negative, odour hardly distinctive, mushroomy, like phenol, of Lepiota cristata or Scleroderma, fishy, rarely of anise or bitter almonds . . . . . . . . . . . . . . . . . . . . . . . . .4
-
2.- Lower surface of the annulus constituted by cylindrical hyphae and inflated elements with rounded ends. Annulus double, thick, with cottony scales on the lower surface. Cheilocystidia catenulate . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Flavescentes] sect. Arvenses
2.- Lower surface of the annulus constituted only by cylindrical hyphae. Annulus double or simple. Cheilocystidia simple or septate at the base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . .. . . . . 3
-
3.- Annulus double, thick, with cottony scales on the lower surface . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Minoriopsis] sect. Minoriopsis
3.- Annulus simple, thin, smooth on the lower surface . . . . . . . . . . . . . .A. [subg. Minores] sect. Minores
-
4.-Odour of Lepiota cristata or Scleroderma, KOH reaction positive pale olive yellow or negative on pileus surface, context when cut unchanging or slightly rufescent in the stipe cortex, never turning strongly red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Spissicaules] sect. Subrutilescentes
4.- Odour not so, KOH reaction positive yellow or negative on pileus surface, context sometimes turning strongly red 5
-
5.- Odour indistinct or mushroomy, inferous annulus absent, if strongly reddening cheilocystidia simple (neither catenulate nor septate at the base), pyriform, globose to sphaeropedunculate with width often equal to, or bigger than half their length, KOH reaction on pileus surface negative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Agaricus] sect. Agaricus
5.- With other combination of characters (A. subg. Pseudochitonia) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
-
6.- KOH reaction on pileus surface positive bright yellow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 7
6.- KOH reaction on pileus surface negative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
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7.- Stipe base when rubbed discolouring pale to bright yellow and with an intense odour of phenol, if unchanging and lacking phenol odour cheilocystidia clavate 6-12 μm in width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Pseudochitonia] sect. Xanthodermatei
7.- Stipe base when rubbed unchanging or hardly yellow and faint odor of phenol, cheilocystidia pyriform, globose or sphaeropedunculate 8-35 μm in width (only A. phaeolepidotus recorded from Mexico) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Pseudochitonia] sect. Hondenses2
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8.- Alpha naphthol negative on the whole context. Superous annulus absent and inferous annulus present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Pseudochitonia] sect. Chitonioides
8.- Alpha naphthol positive at least on the extreme base stipe context . . . . . . . . . . . . . . . . . . . . . . . . 9
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9.- Inferous annulus (annuli) present or absent. When absent the superous annulus is thin and smooth on its underside, taxa possess glabrous stipe, strong red context discolouration and mushroomy odor . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. [subg. Pseudochitonia] sect. Bivelares
9.- Inferous annulus absent. Superous annulus thick with fibrillose to squamose lower surface, if thin and smooth in the lower surface with anise-like or almond odour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . A. [subg. Pseudochitonia] sect. Sanguinolenti
Discussion
Although Mexico possesses ≈10 % of the worldwide diversity, the recently discovered neotropical clades suggest a greater diversity (Callac and Chen, 2017). In countries with similar vegetation types such as the Dominican Republic and the United States have been recently described several species (Parra et al., 2018; Kerrigan, 2016). However, in Mexico much work remains to be done. Since the last update (Mata et al., 2011), only A. guzmanii and A. tephrolepidus were described as new species from the country (Parra et al., 2018; Chen et al., 2019).
It is expected that Veracruz state presents a high diversity since it has subtropical and tropical vegetation (Zhao et al., 2011; Medel et al., 2018) and it is the most widely studied state in the country.
The distribution of species with secotioid forms (i.e. Agaricus aridicola and A. deserticola) in northern states could imply their presence in states with similar environmental conditions such as Nuevo León or Tamaulipas.
In Mexico, documented information on this genus has been scarce, since a large part of the available records of the species is from lists lacking descriptions, photographs or reference to herbarium material. Few studies provide keys for the identification of Mexican species (e.g. Guzmán, 1970), and traditionally, their identification was based on European keys. Moreover, no key was found for the subgeneric and sectional ranks and for this reason we have included it in this work.
The best-known area of the country is the central region, while Campeche, Coahuila, Colima, Guanajuato, San Luis Potosí and Sinaloa states show no records of Agaricus species. Tropical and subtropical areas have been scarcely studied to date (Medel et al., 2018). Therefore, efforts to know the real diversity of the genus in Mexico should be made to obtain more information on those underexplored areas.
The richest section in the country is A. sect. Arvenses, which comprises edible and medicinal species, e.g. A. arvensis (Pérez-Silva et al., 2006). Thus, it is crucial to go on studying the wild species in terms of cultivation and its secondary metabolites in order to exploit any possible medicinal use. Inconsistencies with respect to some species’ edibility (i.e. A. semotus, A. benesii, A. sylvaticus, A. moelleri and A. placomyces), might be the result of a poor taxonomic identification. However, there have been cases of toxic species (A xanthodermus) that can also be eaten by some people (Kerrigan et al., 2005).
Since advances in molecular studies concerning Agaricus species in Mexico have been made in recent years (Callac and Mata, 2004; Kerrigan et al., 2008; Mata et al., 2016; Velázquez-Narváez et al., 2018; Chen et al., 2019), it can be predicted that taxonomic novelties will be published as a result of a methodical study of the wild species in Mexico, some of which could be from neotropical sections within A. subg. Minoriopsis.
It is recommended that taxonomic studies should include molecular data from now on, since only 15 % of the cited species have been published with DNA sequences. So far, only analyses with ITS have been carried out to identify Agaricus species in Mexico, having proved sufficient to distinguish among them.