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  • Under Assessment
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Inonotus pusillus Murrill

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Scientific name
Inonotus pusillus
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Category
Proposed by
Ricardo Garcia-Sandoval
Ricardo Garcia-Sandoval
Roberto Garibay Orijel
Roberto Garibay Orijel
Comments etc.
Anders Dahlberg, Gregory Mueller

Assessment Notes

This species is known from four localities in two countries, and also it has been reported from Sinaloa and Yucatan, without providing specific localities (Valenzuela et al. 2013). It has been collected from subtropical dry forest, growing in branches of Jacquinia sp. And Zantoxyllum sp., shrubs widely distributed in subtropical areas. Three of the four localities from where the species is known are urban areas, without any specific vegetation type.


Even when this species is known from less than ten localities, and it has been collected few times over the last one hundred years, this species does not have any special ecological requirement, it is able to grow in widely distributed shrubs, and in urban areas without vegetation, and the EOO is significantly large.

Taxonomic notes

This species do not have synonyms, and its taxonomic position was corroborated by Leif Ryvarden (1985). Its phylogenetic affinities are unknown so far. Saccardo & Troter proposed the combination Polyporus pusillus (Murrill) Sacc. & Trotter, but the name was invalid because that combination was used previously by Rostrup.

Description from the protologue: Pileus sessile, convexe, flabeliform, tapering to a narrow base, erumpent from lenticels, 2x2x0.5-1 mm; surface ferruginous to fulvous, silky-striate, subzonate, shining, margin pallid, acute, often depressed; context thin, fibrous, ferruginous; tubes umbrinous, comparatively large, 2-4 mm; polygonal, becoming irregular, much exceeding in length the thickness of the context; mouths at first withish-pulverulent, dissepiments thin, entire; spores small, ovoid, 3.5x5 µ, pale ferrugious, copious, hyphae concolorous.

Valenzuela et al. (2013). Monomitic, generative hypha with simple septa, yellowish to brown yellowish in KOH, inamiloid, simple to branched, 2-8 µ. No cystidia. Basidia 15-22x6-8, hialine to yellowish, four-spored. Spores 4.5-6x3.2-4.8µ, elipsoid, hialine to yellowish, non amiloid, smooth, thin wall.

Why suggested for a Global Red List Assessment?

NOTE The documentation of this assessment is being revised and edited when finalized when entered to IUCNs Red-List database. This species was described in 1904 by Murril, and is only known from two countries in the Neotropics. Since its first record it has been collected only seven times. Six of the records are located in urban or suburban areas, were the land use have an impact in populations. The species was collected from five localities, three in central and south Mexico, one in Belize and one in Dominican Republic, which allows to presume small and scattered populations. Only one of the localities from were is known is under a conservation or sustained management program. Due to current policies in land use on the areas were this species inhabit, and the scattered nature of its distribution, the species populations are in decline.

Geographic range

Only known from four localities in Mexico and one in Belize. This species is restricted to tropical dry forest in the Pacific coast of Mexico and the Caribe. In Mexico was reported from the type locality in the city of Manzanillo,  State of Colima (Murril 1904, Valenzuela et al. 2012); Isthmus of Tehuantepec, state of Oaxaca; Municipality of Cosala, state of Sonora; and sate of Yucatan without location (Valenzuela et al. 2012); one specimen from Five Sisters Lodge, Cayo District, Belize (USDA Forest Service); Santo Domingo, Dominican Republic (GBIF 2018).

Population and Trends

Inonotus pusillus is endemic to the Megamexico 3 region (Rzedowsky 1991) and the Caribe. Megamexico 3 is an area that included the Mesoamerican part of the Neotropical region, and represents a more natural region. This species is restricted to tropical dry forest in localities near sea level (i.e. Manzanillo, Colima, Mexico). Each of the six localities from where it has been collected are hundreds of kilometers away, and usually one individual is collected per locality.

Population Trend: Decreasing

Habitat and Ecology

Inonotus pusillus grows in subtropical dry forest near see level, and is known from the Pacific coast of Mexico, low lands in the Isthmus of Tehuantepec, low lands in Belize, and the Caribe region (Santo Domingo, Dominican Republic; Yucatan, Mexico). Collected on branches of Jacquinia sp. (Primulaceae) or Zanthoxyllum sp. (Rutaceae). This species grows in urban areas without vegetation, and does not have a specific ecological requirement.

Subtropical/Tropical Dry Forest


Main threats for this species came from the scarcity of its distribution (few localities separated for hundreds of kilometers), the small size of its populations (only few specimens are reported from each locality), and the urban and suburban nature of the localities were the species inhabit (only one locality in Belize is a natural reserve). The type locality is the main tourist city in the state of Colima, Mexico, and one of the most popular destinations in the Mexican Pacific coast. Even because of the scarcity of its distribution, this species do not have any specific ecological need, it grown in shrubs widely distributed in subtropical areas, and it has been collected in urban areas without vegetation.

Conservation Actions

Because this species is known from urban areas, and grows in shrubs widely distributed in subtropical areas, any particular conservation action is needed.

Research needed

More research on distribution of this species is needed. So far is known from five localities in two countries, but it is very likely that its distribution is larger.

Use and Trade

No uses are known.


Murrill, W. (1904). The Polyporaceae of North America-IX. Inonotus, Sesia and Monotypic Genera. Bulletin of the Torrey Botanical Club, 31(11), 593-610. doi:10.2307/2478612

Ryvarden, L. (1985). Type studies in the Polyporaceae 17. Species described by W.A. Murrill. Mycotaxon. 23:169-198

Rzedowski, J. (1991). Diversidad y orígenes de la flora fanerogámica de México. Acta botánica mexicana, (14), 3-21.

Valenzuela, R., Raymundo, T., & Cifuentes, J. (2013). El género Inonotus sl (Hymenochaetales: Agaricomycetes) en México. Revista mexicana de biodiversidad, 84, S70-S90.

Country occurrence

Regional Population and Trends

Country Trend Redlisted