The Genus Xanthagaricus: An Updated Global Species Distribution and Phylogeny with the Description of Two New Species from Oman

Abstract

Xanthagaricus is a saprotrophic mushroom genus with small-sized basidiomata in the family Agaricaceae (Agaricales). Prior to this study, 26 species belonging to this genus have been described and published. In this study, we reported Xanthagaricus for the first time from Oman with the description of two new species. Basidiomata of the new species Xanthagaricus appendiculatus and X. omanicus were collected during the monsoon rains of summer in 2018 in the southern coastal region of Oman. Species descriptions are based on morphological and molecular characterization. Phylogenetic analyses based on internal transcribed spacer region (ITS1-5.8S-ITS2 = ITS) of the nuclear ribosomal DNA clustered the new species in the Xanthagaricus clade with strong statistical support. The new species Xanthagaricus appendiculatus can be distinguished from other species by its purplish pileus with umbonate disc and X. omanicus with the largest pileus (70–90 mm diameter) among the known species of the genus. A detailed description, photographs, line drawings, and a phylogenetic tree showing the position of both new species are provided. A dichotomous key to the known taxa of Xanthagaricus is proposed. Morphological comparisons of new species with known Xanthagaricus taxa are provided. Our observations highlight the diversity of Xanthagaricus and other lepiotaceous mushrooms in southern Oman and further document the need for additional systematic focus on the region’s fungi.

Two new species of Hymenagaricus (Agaricales, Agaricaceae) from Oman, based on morphology and molecular phylogeny

“…Several species of Agaricaceae were recently reported from the Dhofar Region ( Al-Kharousi et al 2022a , 2022b ; Hussain et al 2022 ). It is evident that the area is rich in the diversity of Agaricaceae , including the genus Hymenagaricus .…”

“…This seasonal variation supports a diverse ecosystem and separates Dhofar from the arid desert conditions that prevail in the Arabian Peninsula ( El-Sheikh 2013 ). The Khareef season triggers the growth of various plants and trees, including frankincense trees, creating a lush and vibrant landscape where a number of saprotrophic mushrooms can flourish ( Al-Kharousi et al 2022a ).…”

“…Species of Hymenagaricus are saprotrophic in nature and are mostly distributed in the Palaeotropical Regions. Members of this genus are recognised by the squamulose pellicle on the pileus surface that mostly consists of hymeniform cells or pseudoparenchymatous tissues, yellow to yellowish-brown basidiospores and the absence of both pleurocystidia and clamp connections ( Heinemann and Little Flower 1984 ; Reid and Eicker 1995 ; Little Flower et al 1997 ; Hosen et al 2017 ; Al-Kharousi et al 2022a ). The number of known species in the genus is 17 ( Hussain et al 2018 ; Kumla et al 2021 , 2023 ; Syed et al 2023 ).…”

“…Four species of Agaricaceae , namely Agaricus arabiensis S. Hussain & Al-Sadi, Micropsalliota ventricocystidiata Al-Sadi & S. Hussain, Xanthagaricus appendiculatus Al-Sadi & S. Hussain and X. omanicus Al‐Kharousi, Al‐Sadi & S. Hussain have recently been described from Dhofar Region, Oman ( Al-Kharousi et al 2022a , 2022b ; Hussain et al 2022 ). However, no Hymenagaricus species has been reported from the country.…”