Abstract
The genus Rhytidhysteron is characterised by forming navicular to apothecial hysterothecia, exposing the green, yellow, orange, red, vinaceous or black colours of the hymenium which generally releases pigments in the presence of KOH. The exciple is smooth or striated, the asci bitunicate and ascospores have 1–5 transverse septa. To date, twenty-six Rhytidhysteron species have been described from the Tropics. The present study aims to describe three new species in the Neotropics of Mexico based on molecular methods and morphological features. Illustrations and a taxonomic key are provided for all known species of this genus. Rhytidhysteroncozumelense from the Isla Cozumel Biosphere Reserve, R.esperanzae from the Sierra Juárez, Oaxaca and R.mesophilum from the Sierra Madre Oriental, Hidalgo are described as new species. With the present study, the number of species of Rhytidhysteron known from Mexico is now increased to eight.
Highlights
The genus Rhytidhysteron was described by Spegazzini (1881) and has been shown to belong to the Hysteriaceae (Boehm et al 2009a, 2009b; Wijayawardene et al 2020)
The genus is characterised by forming hysterothecia, with lenticular or irregular, striated, or smooth openings; epithecium of various colours; excipulum composed of 1–2 layers of cells of angularis texture or globose texture
According to Kutorga and Hawksworth (1997), the length of the hysterothecia ranges from 2500–4000 μm, ascospores from (22–)25–35(–39) μm and has dark brown to reddish epithecium in potassium hydroxide (KOH) which changes to pale greenish-brown or from red wine to intense pink
Summary
The genus Rhytidhysteron was described by Spegazzini (1881) and has been shown to belong to the Hysteriaceae (Boehm et al 2009a, 2009b; Wijayawardene et al 2020). Cobos-Villagrán et al (2020), for the Mexican specimens, report ascomata of 1000–3000 μm, ascospores of 22.4–30.4 μm and orange-reddish, yellow or black epithecia changing to magenta in reaction with KOH. These morphological variations within R. rufulum have caused confusion in various fungal collections around the world and, as a result, they have been grouped into a complex of species (Boehm et al 2009b; Murillo et al 2009; Yacharoen et al 2015; Doilom et al 2016; Thambugala et al 2016; Soto-Medina and Lücking 2017)
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