The species characterised by a distintcly annulate stipe. overall features are closely R. cingulata described from Papua New Guinea but in minute there are important differences in that the pileus does not disrupt into flakes or in to scale as R. cingulata. Further basidiospores are larger and less strongly ornamented.

It is unique in Thai mycota. This fungus has only been recorded growing in association with Dipterocarpus alatus (Dipterocarpaceae) from only one plantation of the Royal initiative project in the Eastern area of Thailand.

As demonstrated by Disyatat et al. (2016)  that fragmentation in a dry dipterocarp forest can influence patterns of ectomycorrhizal fungal diversity. Varying results indicate both that different stages of the dipterocarp life cycle may be differentially affected by disturbance and fragmentation and that the degree of disturbance and the environmental setting also play a role in determining tangible effects on dipterocarp communities.

The species is inferred to be rare, and under threat by deforestation and forest fragmentation.

Reported from Eastern part of Thailand in 2006 (Yomyart et al. 2006). Now known only at one plantation on a dipterocarps alatus , a commonly used in plantations.

So far known only from 1 site in Chacherngsoa Province, Eastern part of Thailand. In site, fruiting bodies occur regularly, but population size is estimated to a maximum of 3-5 individuals.  The putative host tree is commonly found throughout the area.  So habitat for additional sites of Russula siamensis exist widely.

The fungus grows in small groups on bare sandy loam soil under Dipterocarpus alatus, which prefers moist soil, and with ground cover of Malaysian grass. Presumably ectomycorrhizal with Dipterocarpus alatus. The host occurs only in the everegreen forests of Myanmar and Thailand and Andaman Islands.

In the area where this species is known to occur, forests continue to be degraded by human activities (e.g., rubber plantation). In a dry dipterocarp forest, Disyatat et al. (2016) further demonstrated that fragmentation can influence patterns of ectomycorrhizal fungal diversity.

Comprehensive surveys and inventories for Thailand, and the SE region are needed to determine the occurrence and distribution of the fungus.
Further annulate Russula species are needed for sequence.

unknown

Yomyart S, Piapukiew J, Watling R, Whalley AJS, Sihanonth P. 2006. Russula siamensis: a new species of annulate Russula from Thailand. Mycotaxon 95: 247-254.

Disyatat NR, Yomyart S, Sihanonth P, Piapukiew J. Community structure and dynamics of ectomycorrhizal fungi in a dipter- ocarp forest fragment and plantation in Thailand. Plant Ecology & Diversity 9(5–6). 2016:577–588.