Evidence of a myco-heterotroph in the plant family Ericaceae that lacks mycorrhizal specificity

Abstract

Myco-heterotrophy is one of the longest-studied aspects of the mycorrhizal symbiosis, but there remain many critical, unanswered questions regarding the ecology and physiology of myco-heterotrophic plants and their associated fungi. The vast majority of all myco-heterotrophs studied to date have exhibited specificity towards narrow lineages of fungi, but it is unclear whether the loss of photosynthesis in these plants is contingent upon fungal specialization. Here, we examine the fungal associates of the myco-heterotroph Pyrola aphylla (Ericaceae) and its closest green relative Pyrola picta to determine the pattern of mycorrhizal specialization. Our findings show that both plant species associate with a range of root-inhabiting fungi, the majority of which are ectomycorrhizal taxa. This study provides the first example of a eudicotyledonous myco-heterotroph that is a mycorrhizal generalist, indicating that the loss of photosynthesis in myco-heterotrophs is not contingent upon fungal specialization.

Evolution of mycoheterotrophy in Polygalaceae: The case of Epirixanthes

“…As the majority of AMF engaged in mycoheterotrophic interactions are Glomeraceae ( Merckx et al, 2012 ), only plants with a restricted clade of symbiotic Glomeraceae are interpreted as having high levels of specialization (e.g., Arachnitis unifl ora , Corsiaceae ; Afrothismia spp., Thismiaceae [ Merckx and Bidartondo, 2008 ]). Lack of specifi city however, is not a rare phenomenon in mycoheterotrophic plants as it is found in species of Aphyllorchis (Orchidaceae), Cephalanthera (Orchidaceae), Pyrola (Ericaceae), Sciaphila (Triuridaceae) and Campylosiphon (Burmanniaceae) ( Hynson and Bruns, 2009 ;Roy et al, 2009 ;Merckx et al, 2012 ). Concluding, our results suggest that species of Epirixanthes are more specialized than their chlorophyllous relatives, but the species are not highly specialized as compared with many other mycoheterotrophic plants.…”

“…We use this framework to compare the fungal specifi city between Epirixanthes and its close relatives in Salomonia and Polygala by measuring the phylogenetic diversity (PD; Faith, 1992 ) of the associated AMF. The results were compared with published insights on AMF of Polygalaceae ( Imhof, 2007 ;Rath et al, 2013 ) as well as to recent studies of mycoheterotrophic specifi city ( Hynson and Bruns, 2009 ;Merckx et al, 2009Merckx et al, , 2012Roy et al, 2009 ).…”

Artificial Cultivation System for Gastrodia spp. and Identification of Associated Mycorrhizal Fungi

“…Most MHPs have a high fungal specificity (reviewed by Bidartondo, 2005), whereas others interact with a variety of species (Roy et al, 2009;Hynson & Bruns, 2009). Obligate MHPs, which include about 530 species, do not produce functional chloroplasts and are completely dependent on their associated mycorrhizal fungi as a source of carbon.…”

Mycobiont overlap between two mycoheterotrophic genera of Monotropoideae (Pterospora andromedea and Sarcodes sanguinea) found in the Greater Yellowstone Ecosystem

“…Monotropoideae (Ericaceae) is mainly comprised of mycoheterotrophic plants (Bidartondo and Bruns 2002;Hynson and Bruns 2009). These achlorophyllous plants form a tripartite relationship with an autotrophic host via an obligate mycorrhizal fungus to procure their carbon requirements.…”

“…These achlorophyllous plants form a tripartite relationship with an autotrophic host via an obligate mycorrhizal fungus to procure their carbon requirements. Although some generalist relationships do exist, (Martos et al 2009;Roy et al 2009;Hynson and Bruns 2009), many mycoheterotrophs are specific to certain genera, species groups or individual species of fungi (Leake 2004;Bidartondo and Bruns 2002). Three tribes of mycoheterotrophs are recognized in Monotropoideae: Pterosporeae, Monotropeae and Pyroleae.…”