Tylopilus aquarius var. megistus Wartchow, Barbosa-Silva, B. Ortiz & Ovrebo, in Barbosa-Silva, Ovrebo, Ortiz-Santana, Sá, Sulzbacher, Roy & Wartchow, Sydowia 69: 116 (2017)
It is an endemic species from Brazil, with a restricted distribution in a threatened environment (areas of restinga within the Atlantic Forest from Northeast Brazil).
Tylopilus aquarius ver. megistus is endemic to Restingas in Northeast Brazil. Restingas are unique, highly threatened ecosytems restricted to sandy coastal forests. Tylopilus aquarius var. megistus is known from only two sites, but it is likely to be more widespread occurring in high quality restingas, with a total population estimate of around 1,200-3,600 mature individuals, all in one subpopulation. Based on the severe habitat decline within the area, we infer a population decline around at least 30% in the last three generations (50 years) and this decline is ongoing. It is assessed as Endangered C1+2a(ii).
The species is currently known only from two sites at the urban park Parque Estadual das Dunas de Natal, Rio Grande do Norte state, which encompass an area of 1,172 ha surrounded by the city and at Reserva Biológica Guaribas, SEMA II, Paraíba state, with an area of 3.016,09 ha (Barbosa-Silva et al. 2017). The species grows in restinga, an unique ecosystem represented by fragmented coastal sand forests in the eastern coast of Brazil that often grows on ancient dune formations. It is expected that the species is distributed along the Atlantic Forest restrict to restingas. However, many other restinga areas towards the south of Brazil have been intensively explored in search of the species, but so far no success, which indicates that the species might be rare.
There are thirteen collections of the species deposited in fungaria. Nine collections are from Reserva Biológica Guaribas, and four are collections from Parque Estadual das Dunas de Natal. The longest distance between the two known collecting sites is around 120 km. This is a species with medium to high detectability, with medium sized basidiomes (ligth brwon pileus up to 12 cm diam.) even so, after intensive collecting in potential habitat it has not been found at other sites. It appears to be restricted to high quality sites. The Atlantic Forest has been deforested over decades, and the remaining fragments are suffering from biomass and biodiversity erosion, being one of the most fragmented tropical/subtropical forests in the world. Around 28% percent of the original forest in Brazil is left, much of it in small, unconnected fragments (Rezende et al. 2018). The restingas are a type of sandy coastal plain habitat associated with the Atlantic Forest domain, and are located along the litoral of eastern Brazil, coinciding with the area occupied by approximately 70% of the country’s population. As a result, Restingas are one of Brazil’s most impacted environments, with high rates of habitat loss, and are probably the country’s most endangered ecosystem (Rocha et al. 2007);. Its original area has been reduced by more than 90% (SOS MATA ATLÂNTICA 2021), and only 299 km2 of Restingas were in protected areas at the end of the 20 century (Zamith and Scarano 2006). Due to the small remaining area of suitable habitat, it is estimated that the species occurs in only 100-300 additional sites, each supporting around 12 mature individuals. This gives a total population estimate of between 1,200-3,600 mature individuals, restricted to one subpopulation. Based on extensive loss of suitable habitat and the putative influence that habitat degradation has on species occupation in a given environment (Berglund & Jonsson, 2003; Haddad et al., 2015), we precautionarily infer a population decline of at least 30% within the past three generations (50 years) and this decline is likely continuing into the future
Population Trend: Decreasing
The species grows in Restingas, in sandy soil substrates, forming 1-4 basidiomes per mature individual. The specimens were collected in the Brazilian northeast region during the rainy season in the autumn and winter (may-septermber). It is likely ectomycorrhizal like other species in the genus, and its distribution may follow the host (unknown) geographic distribution.
The main threats effecting Restingas are urban expansion, real estate speculation in coastal areas, tourism, pollution from the disposal of garbage and effluents, deforestation, the presence of exotic species such Casuarina, Eucalyptus and Pinus, and the lack of planning for the use of the restingas areas, as well as the lack of environmental education about the importance of restingas. Protected areas including restingas at the end of the 20 century covered only 299 km2 (Zamith and Scarano 2006).
To contain or mitigate the degradation of the restingas, ensuring that these areas can continue exercising their important environmental function, the Brazilian Forest Code – Law No. 12,651 of May 25, 2012 classified the restingas areas as Areas of Permanent Preservation (APP), stipulating rules for use and occupation. However, conservation actions including the management and maintenance of these protected areas where the species is found is not effectively being carried out. Developing conservation plans for other areas where the species might occur as well as the creation of new conservation areas with the appropriate reforestation action is needed.
More collections are needed to better understand the full geographic distribution of the species, especially towards the south of Brazil, and understand the phenology of the species. The genus is likely ectomycorrhizal, so it is necessary to confirm the mycorrhizal status of the species and identify its possible hosts. Many boletes are edible, and studies to investigate its potential use would be beneficial.