Steccherinum subochraceum was described by Hjortstam & Bononi (1986) to validate the species Irpex hydneus, which was proposed by Rick (1959) but with no type mentioned. Maas Geesteranus (1974) also proposed the combination Steccherinum hydneum (Rick) Maas G. for this species, but since the basoninym was invalid, this name also should be considered invalid.
Steccherinum subochraceum is known from the Atlantic Rain Forest, with most records in forest remnants in urban areas of São Paulo. The species is expected to become even rarer with the continued loss and degradation of habitat due to human activity and climate change.
Steccherinum subochraceum is known only from three sites in southern and southeastern Brazil, two in São Paulo State and one in Rio Grande do Sul State. One collection was also identified from northern Brazil in a mangrove area, but this is likely a different species since it was found in a different habitat, so it is not considered in the species range of distribution. All of the sites where the species is known are in the Atlantic Rainforest Domain, in forest remnants in urban areas. It is expected to occur in other areas of the Atlantic Rainforest domain in Brazil.
Steccherinum subochraceum is known from sixteen collections, one from Rio Grande do Sul State and 15 from São Paulo. However, at least half of the collections from São Paulo present problems in the identification. Therefore, we consider an estimate of no more than 10 known specimens. In addition, all the known collections are over 20 years old and only the type and the specimen from Rio Grande do Sul have been thoroughly being studied (Westphalen at al. 2021). In over 10 years of surveys in Rio Grande do Sul and São Paulo States, including the areas where the species had been recorded, it was never found. It is unclear if the older specimens could be misidentified or if there was a decrease in the population of S. subocrhaceum in these areas.
Taking into account the amount of potential appropriate habitat for the species, there are 1,500 estimated sites, with up to 10 mature individuals each. Total population is estimated at up to 20,000 mature individuals. It is likely that these numbers are overestimated and the species is even rarer throughout its potential range, given the poor current state of the forests where it is known from, and the fact that it has not been registered in 24 years.
With the only subpopulation known occurring in threatened areas in the Atlantic Forest domain, that has just 28% of its original area remaining, mostly composed by secondary forests (Tabarelli et al. 2010, Rezende et al. 2018), and an ongoing decline predicted to continue in the near future, the species has projected decline in population size of at least 16% covering three generations of the species. Population decline was estimated in light of extension loss of suitable habitat (Rezende et al. 2018) 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
Steccherinum subochraceum is a white-rot wood-decaying fungus currently known from the Atlantic Forest domain in southern and southeastern Brazil. It grows on dead branches and logs of angiosperms. The species is expected to be rare but widespread throughout other areas of the Atlantic Rainforest in Brazil.
The Atlantic Forest is regarded as a biodiversity hotspot for conservation priorities due to its high diversity, endemism rates and habitat loss (Myers et al. 2000). This phytogeographical domain is estimated to have only 28% of its vegetation remaining, with the remnants being fragmented and composed mostly by secondary forests (Tabarelli et al. 2010, Rezende et al. 2018). According to Pinto et al. (2006), the Atlantic Forest is found in this situation due to predatory exploration of resources and human actions, like territorial occupation. About 60% of the Brazilian population lives in the Atlantic Forest, mainly in coastal areas, where the country’s largest cities are located (Rezende et al. 2018). Also, reduction and ‘savannization’ of Atlantic Forest is expected due to climate change in the next decades (Salazar et al. 2007).
The main conservation action required is the continuity and enhancement of protection within Conservation Areas and enforcement of public policies to recover secondary forests. Also, more surveys are needed to understand the species’ distribution in Brazil.
Steccherinum subochraceum is similar to other species of Steccherinum, which may cause misidentifications. The paratype cited by Hjortstam & Bononi (1986) is different from the holotype as well as other specimens deposited at SP herbarium. A thorough review of herbarium species as well as more surveys to find newer collections of S. subochraceum and to obtain DNA sequences of the species are needed to elucidate its true distribution and if it is even rarer than it appears to be.
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