Geesterania davidii was described by Westphalen et al. (2018) based on morphological and molecular evidence. The species is related to G. carneola, the only other known species in the genus.
Geesterania davidii is a rare species, with only four records, most of them in Araucaria forests. In addition, it is known only to Rio Grande do Sul State (Brazil) and is most likely restricted to the subtropical Atlantic Forest in southern Brazil, which is considered a threatened biodiversity hotspot (Myers 2000) composed only of few forest remnants.
Geesterania davidii is known only from three sites, all of them in Rio Grande do Sul State, southern Brazil. Two of these sites are located in the municipality of São Francisco de Paula, in Araucaria Forests (900 m a.s.l.), distancing about 25 km from each other. The holotype is the only specimen known from dense ombrophilous Forests at sea level, but distancing less than 30 km from the closest montane site where the species was found. This shows that the currently known distribution is very restricted in the northeast of Rio Grande do Sul State, in areas with subtropical climate, indicating a preference of the species. It is expected to occur mostly in Araucaria Forests and more scarcely in other subtropical areas of the Atlantic Forest domain in southern Brazil
Geesterania davidii is known only from four collections, all of them from Rio Grande do Sul State. In many areas where the Funga has been intensively surveyed in the Atlantic Forest domain in southern Brazil in the past 15 years the species was never found, which indicates that it is likely rare. The region of São Francisco de Paula is one of the most surveyed in Rio Grande do Sul State and only three collections of G. davidii were found, also indicating its rarity even in its known area of occurrence. Taking into account the amount of potential appropriate habitat for the species, there are 500-800 estimated sites, with up to 6 mature individuals each. Total population is estimated at 6,000-9600 mature individuals. It is possible that these numbers are overestimated, as the species may not find conditions to occur in much of its potential range, given the poor current state of the forests where it could possibly be found.
With the only subpopulation known occurring in threatened areas in the Atlantic Forest domain, which has just 28% of its original area remaining and is composed mostly of secondary forests (Rezende et al. 2018), added to the preference of the species to montane environments in Araucaria Forests, which have lost about 97% of the original cover in the last 100 years (Castro et al. 2020), an ongoing decline is predicted to continue in the near future. The species has a projected decline in population size of at least 20% covering three generations of the species. Population decline was estimated in light of extension loss of suitable habitat (Rezende et al. 2018, Castro et al. 2020) 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
Geesterania davidii is a white-rot wood-decaying fungus. It grows on dead branches and more rarely logs of angiosperms. The species is expected to be rare but also found in other subtropical areas of the Atlantic Forest domain, mostly in Araucaria Forests.
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). 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). In addition, G. davidii is known mostly from montane environments, in Araucaria Forests, which have lost about 97% of the original cover in the last 100 years, mainly due to logging, a decline that is still ongoing, and currently are mostly found in southern Brazil. Only a small part of the Araucaria Forests are in conservation areas, and studies suggest that, due to climate change, by 2070 they could be restricted to highland microrefugia, from which only 2,5% are in conservation areas (Castro et al. 2020, Tagliari et al. 2021, Wilson et al. 2019).
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.
Geesterania davidii is morphologically similar to G. carneola, which may cause misidentifications. However, both species can be easily differed by the pore size. Even though herbaria revisions have already been carried out by Westphalen et al. (2018), it is important to further review collections from southern Brazil to confirm the species distribution.
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