Cantharellus rubrosalmoneus is an endemic species of the eastern coast of Madagascar. Based on current records it is known from two locations with a highly restricted area of occupancy (AOO) and extent of occurrence (EOO). Based on the area of currently known sites these are only 60 km² and 705 km² respectively. The population size is also predicted to be very small, potentially as low as 100-250 mature individuals. While these are minimum possible values, with the extensive habitat loss in the region means there is very limited suitable habitat available for the species, and so the maximum values are unlikely to be significantly greater (i.e. to exceed the thresholds for a threatened category) unless it were to be discovered in additional localities away from this area. While a population decline is suspected based on habitat loss, further information is required before a population decline can be inferred or the rate of decline estimated. Therefore, C. rubrosalmoneus is precautionarily assessed as Endangered under criteria B1ab(iii)+2ab(iii); D, but if a population decline were to be confirmed then it could warrant reassessment as Critically Endangered under criterion C.

Cantharellus rubrosalmoneus is endemic to the coastal region of eastern Madagascar. In its original description it was described from the Tampolo Forest station, near Fénérive Est (Buyck et al. 2015). There have been recent, additional collections from this site, as well as from Ambila Lemaitso (Buyck and Hofstetter 2018).

It is suspected that the population may be in decline due to ongoing threats to its habitat, which is severely fragmented due to extensive habitat loss in the region (see World Resources Institute 2023). There have been multiple collections from the type locality, Tampolo Forest station, from at least two different sites there based on georeferenced localities in Buyck and Hofstetter (2018). Thus, it is likely that there are multiple genets at this site. Based on the scaling factor of Dahlberg and Mueller (2011), and the amount of suitable habitat at this site then a subpopulation size for this locality could be c. 50 mature individuals. There has been only one reported collection from the other locality, but with a similar sized area of suitable habitat, it may be appropriate to assume a similar subpopulation size there. If these are the only two sites for the species then the population size would only be 100 mature individuals. It is conservatively estimated that the species occurs in at least two more sites, and the total population size is fewer than 250 mature individuals.

With the extensive loss of habitat in the region (see World Resources Institute 2023), it is plausible that these could be the only two sites for the species. However, if it does persist in some of the small, fragmented pockets of natural vegetation that remain then the overall population size could be larger, although the number of mature individuals per site for these other localities could be smaller. Thus a relatively low scaling factor of 5-10x, to take into account additional potential sites, is used here. Thus the estimated maximum population size is 500-1,000 mature individuals, with an overall range of 100-1,000 mature individuals. With a degree of uncertainty over the full range (i.e. if it is only present at these two sites, or if it is more widespread) it is not currently possible to accurately give an estimate of the potential scale of the population decline over three generations.

This is an ectomycorrhizal species of littoral forest, growing on deep sandy soil (Buyck et al. 2015, Buyck and Hofstetter 2018). It has been collected growing under Uapaca littoralis, Asteropeia multiflora, Leptolaena spp. and Sarcolaena spp. (Buyck et al. 2015, Buyck and Hofstetter 2018).

Littoral forest in eastern Madagascar has been extensively cleared throughout the range of the species. Some will have been lost to urbanisation, e.g. in and around Toamasina, but there has also been extensive land clearance in the region, with major drivers being from logging (for timber as well as for charcoal), and for agriculture (see e.g. Ecological Health Network 2023, World Resources Institute 2023).

Ensuring effective protection of remaining patches of suitable littoral forest within the range of this species will be important for its persistence. Further research into the overall range of the species will help to generate a more accurate estimate of the population size and trend as well. In its original description this species was described as a subspecies of Cantharellus subincarnatus (Buyck et al. 2015), but it has since been elevated to full species status, and C. subincarnatus is no longer accepted as a valid species (Buyck and Hofstetter 2018). Further taxonomic work to gain a better understanding of its affiliations with other Cantharellus species from mainland Africa could prove to be interesting (see e.g. Buyck et al. 2015, Buyck and Hofstetter 2018).