Laetiporus squalidus sporocarps are known only from two localities in high altitude environments of the Brazilian southern/south-eastern Atlantic Forest domain. The sites are in the Dense Ombrophilous Forest (above 700 m alt.) in São Paulo State and in the Cloud Forests (Mixed Ombrophilous Forest) of Santa Catarina State (above 1,500 m alt.) 1,000 km to the south. Based on the potential area where the species can occur, there are an estimated 1,000 sites each with 2-4 mature individuals. The total number of mature individuals is estimated to be no more than 4,000, restricted to one subpopulation. The population is inferred to decline by at least 10-15% over the next 30 years, driven by continued loss and degradation of the habitat in the Atlantic Forest due to human activity and climate change. The species is assessed as Vulnerable.
Laetiporus squalidus is a recently described species (Pires et al. 2016) based on molecular phylogenetic evidence and morphological characteristics. Authors suggested that the taxon could be a new genus, but maintained it as a new species in Laetiporus. A proposal for a new genus is in preparation.
Laetiporus squalidus is a wood-decaying fungus, causing brown rot. This is a very rare species, having been recorded only for three sites over four years since it has been described from the Brazilian Atlantic Forest inside São Paulo.
Currently, Laetiporus squalidus sporocarps are known only from two localities in high altitude environments in the southern/south-eastern Atlantic Forest domain of Brazil, in the Dense Ombrophilous Forest (above 700 m alt.) in São Paulo State and in Cloud Forests (Mixed Ombrophilous Forest) of Santa Catarina State (above 1500 m alt.). These two sites are separated by over 1,000 km. In Santa Catarina the species was collected on Schinus englerii (Anacardiaceae), but no substrate identification was given from the São Paulo specimens. The species is expected to occur elsewhere in the Atlantic Forest, likely restricted to montane environments in the Serra do Mar mountain range.
There is a record of Laetiporous squalidus from New Zealand isolated as a non-fruiting endophyte from Eucalyptus fastigata, an introduced species that is native to south-eastern Australia. The material was identified through DNA sequencing, with only a 3 base pair difference in ITS sequence between it and examined Brazilian material
. ITS sequences alone are not always able to discriminate between unique species in Laetiporaceae (Drechsler-Santos, pers. com.). Fungi on species of Eucalyptus have been well studied in Australia and worldwide, and no records of L. squalidus sporocarps have been found from that part of the world. Given the uncertainty of the identification and lack of data of a mature individual (it is only known from a single culture), further information is needed to determine conspecificity of the New Zealand material and its presence in Australasia. Therefore, this assessment is based only on Brazilian material.
The species was first recorded in 2014 with three collections from São Paulo State, Brazil, in the Atlantic Forest domain. These three collections were the only known records until very recently, when a collection was recorded in 2019 from Santa Catarina State in southern Brazil, also in the Atlantic Forest domain (FLOR 67251). The species is expected to be distributed elsewhere in the Atlantic Forest, likely restricted to montane environments in the Serra do Mar mountain range. Based on the extent of potential appropriate habitat, the species could occurs in up to 1,000 additional sites, each supporting 2-4 mature individuals resulting in an estimation of no more than 4,000 mature individuals; restricted to one subpopulation.
The population is inferred to decline by at least 10-15% over the next 30 years, due to continued loss and degradation of the required habitat in the Atlantic Forest due to human activity and impact of climate change.
Population Trend: Decreasing
Laetiporus squalidus is saprobic and lignicolous, causing a brown-rot. The specimen from southern Brazil was found on Schinus englerii (Anacardiaceae), but no host information was given for the São Paulo specimens. It is known only from montane environments, both in Coastal Atlantic Forests (dense ombrophilous forest) and cloud forests (with mixed ombrophilous forest).
The species is known from two localities in the Atlantic Forest domain. The deforestation rate of the Atlantic Forest largely declined in the last two decades. However, it was the most exploited ecosystem, and only 28% of its natural coverage remains, largely composed of small forest fragments and secondary forests (Tabarelli et al. 2010, Rezende et al. 2018). The type locality is an area inside the most developed state in Brazil, and natural areas are under threat from continued expanded agricultural and urban growth. The southernmost locality is in the Cloud Forests of São Joaquim National Park, about 1,000 km south of the type locality. Cloud Forests are a naturally fragmented environment, and their dependence on the fog regime makes them particularly vulnerable to climate change, as changes in temperature alters the occurrence of clouds (Foster 2001). Although it is a legally protected area for biodiversity, the area still faces many problems, such as alien invasive species, and increased fire frequency. Additionally, Conservation Units in Brazil often have problems with a conflict of land use and ownership within their boarders, which severely compromises the effectiveness of biodiversity conservation (Rocha et al. 2010).
Each of the known localities are in Conservation Areas, but the species also likely occurs in non-protected areas. The main conservation action required is the continuity and enhancement of protection within Conservation Areas and implementation of habitat protection and management at other sites inside the Atlantic Forest in a attempt to protect the remaining habitat fragments of the domain.
More research is needed to understand the phylogenetic position of the species. The genus Laetiporus and the family Laetiporaceae are undergoing revision by specialists, and new species and genera have been described, as well as new taxonomic combinations (Banik et al. 1998, Song and Cui 2017). Work to resolve the possible occurrence of the species in Australasia is also needed (a rDNA barcode sequence of a culture of an endophyte from Eucalyptus fastigata (ICMP 16889) from New Zealand has been reported, Hhowever, no mature basidiomata from Australasia has been reported). Also, more surveys are needed to understand the species’ distribution in Brazil, and much of the Laetiporus life cycle remains unknown.
Banik, M.T., Burdsall, H.H. and Volk, T.J. (1998) Identification of groups within Laetiporus sulphureus in the United States based on RFLP analysis of the nuclear ribosomal DNA. folia cryptogamica estonica 33, 9–14.
Foster, P. (2001) The potential negative impacts of global climate change on tropical montane cloud forests. Earth-Science Reviews 55(12): 73-106
Pires, R.M., Motato-Vásquez, V. and de Mello Gugliotta, A (2016). A new species of Laetiporus (Basidiomycota) and occurrence of L. gilbertsonii Burds. in Brazil. Nov. Hedwigia 102, 477–490.
Rezende, C.L., Scarano, F.R., Assad, E.D., Joly, C.A., Metzger, J.P., Strassburg, B.B.N., Tabarelli, M., Fonseca, G.A., Mittermeier, R. A. (2018) From hotspot to hopespot: An opportunity for the Brazilian Atlantic Forest. Perspectives in Ecology and Conservation. doi:10.1016/j.pecon.2018.10.002
Song, J. and Cui, B.-K. (2017) Phylogeny, divergence time and historical biogeography of Laetiporus (Basidiomycota, Polyporales). BMC Evol. Biol. 17, 102.
Tabarelli, M., Aguiar, A. V., Ribeiro, M. C., Metzger, J. P., & Peres, C. A. (2010) Prospects for biodiversity conservation in the Atlantic Forest: Lessons from aging human-modified landscapes. Biological Conservation, 143(10), 2328–2340. doi:10.1016/j.biocon.2010.02.005