Isotopic evidence of partial mycoheterotrophy in Burmannia coelestis (Burmanniaceae)

The Burmanniaceae contain several lineages of achlorophyllous mycoheterotrophic plants that associate with arbuscular mycorrhizal fungi (AMF). Here we investigate the isotopic profile of a green and potentially mycoheterotrophic plant in situ, Burmannia coelestis, and associated reference plants. We generated δ 13C and δ 15N stable isotope profiles for five populations of B. coelestis. Burmannia coelestis was significantly enriched in 13C relative to surrounding C3 reference plants and significantly depleted in 13C relative to C4 reference plants. No significant differences were detected in 15N enrichment between B. coelestis and reference plants. The isotopic profiles measured are suggestive of partial mycoheterotrophy in B. coelestis. Within the genus Burmannia transitions to full mycoheterotrophy have occurred numerous times, suggesting that some green Burmannia species are likely to be partially mycoheterotrophic but in many conditions this mode of nutrition may only be detectable using natural abundance stable isotopic methods, such as when associated with C4 mycorrhizal plants. This study provides the first evidence of partial mycoheterotrophy in a green Burmanniaceae using natural abundance stable isotope methods. Associated mycorrhizal plants with C4 metabolism probably provided the enriched d13C signature in Burmannia coelestis.