Armillaria paulensis Capelari, Mycol. Res. 112(9): 1125 (2008)
Armillaria paulensis is a saprotrophic and parasitic species, described in 2008, andso far known from 5 collections from Southern and Southeastern Brazil. This is a species with medium to high detectability and was found in Dense and Mixed Ombrophilous Forest. The estimated population size is 20,000 – 40,000 mature individuals, restricted to one subpopulation, which is expected to decline by at least 16% over the next 30 years (three generations). Although occurring in a biodiversity hotspot, neither the inferred population decline of Armillaria paulensis nor population size qualifies the species as threatened. Thus, it is assessed as LC.
The species is known from only two locations, one of them is the holotype site, in the Parque Estadual das Fontes do Ipiranga (23°39’ S 46°37’ W), south of São Paulo city (Lima et al. 2008). Scheibler (2016) reports the species occurrence in the Floresta Nacional de São Francisco de Paula (29°25’22"S 50°23’11"W), in Rio Grande do Sul. Armillaria paulensis is expected to be distributed in the south and southeast of the Atlantic Forest biome, in places with mature vegetation, both in Dense Ombrophilous Forest and Mixed Ombrophilous Forest.
There are only 5 collections of the species from two sites. The species was described based on a specimen collected on July 8, 2004, in the Parque Estadual das Fontes do Ipiranga, a conservation unit located in the southeast region of the São Paulo city. The vegetation of PEFI is mainly the Dense Ombrophilous Forest, and it is the largest fragment of Atlantic Forest inserted in the urban area of the Metropolitan Region of São Paulo. The park is composed of well-preserved areas of mature vegetation and areas in recovery, composing a mosaic of different successional stages.
The other 4 known collections of the species were found on two dates (May 17, 2014 and May 25, 2015) in the Floresta Nacional de São Francisco de Paula (FLONA). FLONA is located entirely in the municipality of São Francisco de Paula, in the northeast of the state of Rio Grande do Sul. The predominant vegetation in FLONA is Mixed Ombrophilous Forest (forest with araucarias).
This is a species with medium to high detectability, and considering the history of the study of macrofungi in southeastern and southern Brazil, the species is expected to occur in 500 – 1.000 sites with up to 40 mature individuals per site, with an estimated population size of 20,000 – 40,000 mature individuals, restricted to one subpopulation.
The total population of A. paulensis is expected to decline by at least 16% over the next 30 years (three generations), based on extensive loss of suitable habitat (Silva et al. 2020, Rezende et al. 2018, Joly et al. 2014) and the putative influence that habitat degradation has on species occupation in a given environment (Berglund & Jonsson 2002, Haddad et al. 2015).
Population Trend: Decreasing
A. paulensis exhibits a gregarious to caespitose growth, and is found growing on logs of an undetermined angiosperm tree (Lima et al. 2008) in the Atlantic Forest (Dense and Mixed Ombrophilous Forest). Scheibler (2016) found the species growing on a decaying trunk and on a living tree (unidentified).
Primary threats include habitat loss and fragmentation, logging, fire, and climate change. The expansion of urban areas is also an important pressure further reducing the area of the Atlantic Forest (Joly et al. 2014). Weak enforcement of conservation policies threaten some remaining high quality areas where the species occurs.
The specimens of A. paulensis were collected in national and state preservation areas. To guarantee the species survival it is necessary to maintain existing preservation areas, reinforce fiscalization and create new conservation areas.
Although the species has large and conspicuous basidiomata, A. paulensis is known for only two localities. Scheibler (2016) observed clamp connection at the base of some basidia, a characteristic not mentioned in the description of the holotype. Thus, it is necessary to expand sampling, and carry out morphological and molecular studies to better understand the morphological circumscription and distribution of the species, as well as research to identify its possible hosts.