So far distribution is only known for Guangzhou in the Guangdong province, but since authors say that a larger distribution is likely I also added GFW data for the surrounding provinces in the “Population and current trends” field. This species may apply for a threatened category due to deforestation through criterion A, but uncertainty in distribution and hosts makes it difficult to establish. Only included known region in the distribution map.
Nigroboletus roseonigrescens is a bolete known from south-eastern China. The species was described in 2015 from 2 locations in the Guangdong Province, but it is thought to be common and a wider distribution is likely. For this reason, population size is estimated to be of at least 20000 individuals. Since no specific plant host relationship or significant population decline has been established, the species is assessed as Least Concern (LC). (Unsure between Least Concern and DD, given that there are so few records and distribution is not yet clear, and GFW reports some deforestation)
Nigroboletus roseonigrescens is the only species of the Nigroboletus genus, described for the first time in 2018 with morphological and phylogenetic evidence (Gellardi et al 2015).
Why suggested for a Global Red List Assessment?
So far known from two locations in Guangzhou, Guangdong Province, China.
Population and Trends
This species has so far only been reported for 2 distinct locations in Guangzhou, between 2012 and 2014. However, Gellardi et al. (2015) noted that the species appears to be common and abundant and admit the possibility of a larger area of distribution in south-eastern Asia. Therefore, considering that this is a terrestrial fungus, and the guidelines by Dahlberg and Mueller (2011), population size is estimated at 20000 individuals (2 sites x 10 mature individuals x 1000 multiplier).
The southeastern and south regions of China, where the Guangzhou region is located, present the higher deforestation rates in China (Zhang et al. 2022), and Global Forest Watch (2022) shows a decrease in forest cover (>30% canopy density) of 20% between 2001 and 2021 in the Guangdong province. Surrounding provinces also show some degree of deforestation for this period: 20% in Guangxi, 7% in Hunan, 12% in Jiangxi and 14% in in Fujian. Still, forests dominated by Castanopsis fissa or Castanea henryi were not included in Red list of China’s forest ecosystems (Chen et al. 2020) and the existence of other potential hosts make estimating population declines through habitat reduction difficult.
Population Trend: Uncertain
Habitat and Ecology
N. roseonigrescens grows in clayey soil among litter, gregariously or scattered. It was found in tropical montane and lowland mixed forests with mostly Castanopsis fissa, Castanea henryi, Lithocarpus sp., as well as Schima superba and Litsea rotundifolia var. oblongifolia (Gelardi et al. 2015)
Deforestation in southern China can present a threat to this species.
Housing & urban areasScale Unknown/Unrecorded
Given that deforestation may present a threat to this species, monitoring and protection of areas of potential habitat in the south of China is recommended to prevent declines in population.
Resource & habitat protection
Increase in searching efforts in other regions to confirm whether this species has a wider distribution and to obtain a better estimate of population size. More research into its habitat specificity is also important to establish potential threats, namely loss of habitat.