Halimium as an ectomycorrhizal symbiont: new records and an appreciation of known fungal diversity

Abstract

Halimium is a genus of Cistaceae, containing a small group of shrub species found in open vegetation types and in degraded forest patches throughout the western and central Mediterranean region. We recently described the morpho-anatomical features of the ectomycorrhizae formed by Scleroderma meridionale on Halimium halimifolium, but the mycorrhizal biology of this host plant genus is still largely unexplored. Here, we report new data on the ectomycorrhizal fungal symbionts of Halimium, based on the collection of sporocarps and ectomycorrhizal root tips in pure stands occurring in Sardinia, Italy. To obtain a broader view of Halimium mycorrhizal and ecological potential, we compiled a comprehensive and up-to-date checklist of fungal species reported to establish ectomycorrhizae on Halimium spp. on the basis of field observations, molecular approaches, and mycorrhiza synthesis. Our list comprises 154 records, corresponding to 102 fungal species and 35 genera, revealing a significant diversity of the Halimium ectomycorrhizal mycobiota. Key ectomycorrhizal genera like Russula, Lactarius/Lactifluus, Amanita, Inocybe, and Cortinarius account for more than half of all mycobionts. A large proportion of Halimium fungal species are shared with other host plants in various ecological settings, suggesting a critical role of common mycorrhizal networks in the function played by this shrub in various Mediterranean ecosystems.

A short story of nearly everything in Lactifluus (Russulaceae)

“…Abies , Picea , Pinus ), and Cistaceae ( e.g. Cistus, Halimium ) ( Hesler & Smith 1979 , Heilmann-Clausen et al 1998 , Comandini et al 2006 , Van de Putte 2012 , Leonardi et al 2016 , Leonardi et al 2020 ). In Asia, Lactifluus species mainly occur with Dipterocarpaceae ( e.g.…”

Conservation Status of Milkcaps (Basidiomycota, Russulales, Russulaceae), with Notes on Poorly Known Species

“…Christ. by Heilmann-Clausen et al [22]; 48 from North America, often recorded as Lactarius speciosus (J.E. Lange) Romagn.…”

“…As Lactarius luteolus Peck in ECCF, FrRL and SRL. Lactifluus luteolus Peck is the correct name for a North American species [4,47,48]; 78 as Lactarius piperatus (L.) Pers. in CRL, ECCF, ERL, FrRL, GRL, NBIC, NRL, and SwRL.…”

“…However, it should be noted that even in those cases where a 'typical' ectomycorrhizal association can be recognized, the possibility for a given milkcap to enter into mutualistic symbiosis with additional/diverse hosts cannot be ruled out a priori. A relevant, interesting case is L. hepaticus, usually reported as linked to Pinus, but recently shown to enter into shared mycorrhizal network between Pinus and understory Halimium shrubs (Cistaceae) [68], or to occur also in pure Halimium stands [48].…”

“…The correct path that should lead a rare species to be the focus of Red List assessment and eventually conservation measures, in our opinion, is that indicated by Lactarius pseudoscrobiculatus. This Mediterranean species is distributed from Spain to the East Aegean Islands in association with Mediterranean Pinus and Cistaceae (Cistus spp., Halimium halimifolium) [48,97], and has been rarely reported, although it might be locally common (Pierre-Arthur Moreau, personal communication). Detailed morphoanatomical study of new collections and their comparison with original description, integrated by molecular phylogenetic analysis, has recently permitted to expand our understanding of the relationships of L. pseudoscrobiculatus within the genus, and to acquire much needed information on the geographic distribution and ecology of this ectomycorrhizal species [98].…”