On the role of ectomycorrhizal fungi in Pinaceae invasions

HORTON THOMAS R.; NUÑEZ MARTIN A.; RIVERA, YAZMIN; AMICO GUILLERMO C.; DIMARCO ROMINA D.; BARRIOS-GARCIA M. NOELIA; HAYWARD JEREMY; SIMBERLOFF DANIEL

Congreso; Mycology society of America Annual Meeting 2012; 2012

Establishment of Pinaceae in locations with no history of the trees requires the co-introduction of compatible ectomycorrhizal (EM) fungi, which are also required to facilitate invasions. Compatible fungi disperse from plantations through mycelial networks that grow from plantation edges (short distance), and spores dispersed by wind, water and mammals (potentially long distance). Invasion of Pinaceae from plantations into native forests has been limited on Puerto Rico (USA) and Isla Victoria (Argentina). The trees do not associate with native EM fungi to any great extent, if at all. On Puerto Rico most established pines are within decimeters of plantations, but some trees have established at 1000m. Root tips collected from established pines at 1000m from plantations yielded Rhizopogon spp., as well as Pisolithustinctorius, Wilcoxina mikolae and a member of the Atheliaceae. This indicates mammalian (Rhizopogon) as well as other dispersal vectors (Pisolithus, Wilcoxina, Atheliaceae). Bioassays with dried soils collected in areas 1000m from plantations and without pines only yielded Rhizopogon. Dispersal of fungi may be facilitated by rats and mice introduced since the 1500s. In addition, tropical storms and anthropogenic activity may vector the fungi over long distances. On Isla Victoria establishment is largely restricted around plantations. We have not observed the rare native deer or any rodents in or near plantations. However, nonnative deer were first introduced with conifers about 100 years ago and pigs have become numerous since 2004. A bioassay with ponderosa pine and Douglas fir using fecal pellets from the nonnative mammals collected away from plantations yielded Rhizopogon, Suillus, and Hebelomamycorrhizae. Severe weather during the peak fruiting period is probably less important for spore dispersal on Isla Victoria than it is on Puerto Rico. We hypothesize the degree long-distance dispersal and accumulation of compatible propagules can impact the rate at which these invasions proceed.