Tylopilus bulbosus is endemic to southern neotropical Quercus forests. It was described from Costa Rica, but also frequently is found in Colombia. It is possible that the species occurs with Quercus in Panama, but there are no reports. There is no direct information on population reductions, but a significant reduction is inferred due to extensive past and ongoing habitat loss and decline in habitat quality in Colombia resulting in a decline in obligate ectomycorrhizal hosts, species of Quercus. Pressure and population reductions are expected to continue. The Costa Rican subpopulation is likely relatively stable due to forest conservation policies in that country. As the sites in Costa Rica are relatively stable while the sites in Colombia will continue to face significant threats and continued decline, the ongoing reduction for the population of T. bulbosus is suspected to be between 20-25% over three generations. It is listed as Near Threatened.
Tylopilus bulbosus is a conspicuous and rare purple brown neotropical bolete. The species is associated to mountain oak forests in Costa Rica and Colombia. There are not enough information about the trend of the population of T. bulbosus. However, habitat loss and degradation are the main threatened. Tropical forests dominated by Quercus are restricted to mountain areas with anthropic pressures due to land use change, deforestation, timber extraction causing a decrease in populations, fragmentation and loss of habitat quality.
Tylopilus bulbosus is an ectomycorrhizal fungus associated with Quercus species in Costa Rica and Colombia. This species was first described from Costa Rica in wet montane forests in the Talamanca Cordilllera, Alajule, Guanacaste and San José provinces associated with Q. copeyensis, Q. oocarpa, and Q. seemannii. In Colombia this species has been collected in Antioquia in wet montane forests with Q. humboldtii (Sierra-Toro et al. 2011). It is possible that the species occurs with Quercus in northern Panama and/or the Darien, but there are no reports.
Tylopilus bulbosus is known from forests with Quercus in Colombia and Costa Rica (Halling and Mueller 2005, Sierra-Toro et al. 2011). This species is common near San Gerardo de Dota in the Talamanca mountains in Costa Rica (Halling and Mueller 2005). In Colombia the species forms ectomycorrhizas with Quercus humboldtii in Santa Elena, Santa Rosa de Osos and Angelopolis municipalities in Antioquia Department (Herbaria HUA; Sierra-Toro et al. 2011). The species likely occurs in other Quercus dominated forests in Colombia. There are 13 herbarium specimens housed in the herbarium at the University of Antioquia (HUA). It is not known if it occurs with Quercus in Panama.
There is no direct information indicating a population reduction, but a significant reduction is inferred due to extensive past and ongoing habitat loss and decline in habitat quality resulting in reduction in its obligate mycorrhizal hosts, species of Quercus. Further pressure and population reductions are expected to continue. There has been a nearly 42% loss of Quercus humboldtii populations in Colombia, and the tree is nationally listed as vulnerable in Colombia (VU A2cd) (Cardenas and Salinas 2007). Deforestation in Colombia has increased in recent years and is anticipated to continue into the future. A loss of its mycorrhizal host directly impacts T. bulbosus - and it is estimated that the species has undergone a rapid population reduction in the past that will continue into the future resulting in a population reduction of between 30-50% in Colombia, the primary country that it inhabits. There is less data available to suggest a decline of the species in Costa Rica. Parts of the Talamancas are protected in National parks, but other areas are privately held, and there is limited logging ongoing as well as commercial and housing developments. For the mountain areas where this species occurs in Costa Rica, the total forest cover has not significantly changed in the last 20 years (MINAE et al. 2018). As T. bulbosus is ectomycorrhizal and requires a Quercus host, a reduction in host population directly negatively impacts its population size. As the sites in Costa Rica are relatively stable while the sites in Colombia will continue to face significant threats and continued decline, the ongoing decline for the population of T. bulbosus is suspected to be between 20-25% over three generations.
Population Trend: Decreasing
Tylopilus bulbosus is restricted to wet montane forests with Quercus humboldtii in Colombia, and with Quercus copeyensis, Q. oocarpa, and Q. seemannii in Costa Rica. The species is obligatorily ectomycorrhizal with Quercus species. It has been commonly encountered at the sites where it has been reported.
The main known threat to Tylopilus bulbosus is declining habitat and fragmentation resulting in a decrease in area and quality of Quercus dominated forests. Anthropogenic pressure on oak forests and habitat degradation is mainly due to deforestation caused by land use changes, logging, and urbanization. In addition, timber extraction carried out for the production of charcoal in the past and continued use of wood for construction of houses and furniture has significantly negatively impacted oak populations (Cárdenas and Salinas 2007, Nieto and Rodriguez 2010). There are several large mining initiatives being considered for the region, and if they come to fruition they will have a significant negative impact. Deforestation in Colombia has increased in recent years and is anticipated to continue into the future. Due to a policy aimed at conserving remaining natural areas, there is a lower threat level for the species in Costa Rica (MINAE et al. 2018).
Habitat protection and enhanced forest management practices are needed. In Colombia, Quercus humboldtii occurs in several protected sites, including the slopes of Nevados del Puracé and Huila, Parque Nacional Darién, Los Guacharos National Park, Corredor de Conservación de Robles Guantiva – La Rusia – Iguaque, and biological reserves on private land (Cárdenas and Salinas 2007). But most of the habitat is unprotected and susceptible to further deforestation and degradation. Fungi are not included in Colombian conservation and biodiversity policy and laws. The sites where Tylopilus bulbosus occurs in Costa Rica are mostly protected.
Research is needed to document distribution and evaluate population trends. DNA sequences are needed for phylogenetic inference and to provide information to enable identification of environmental samples required for molecular based ecology studies. A taxonomic review of the collections deposited in the Colombian, Costa Rican and Panamanian herbaria should be carried out, as there are many unidentified Boletaceae specimens.
No uses have been reported for this species