Format: ORAL

Francisco E. Fontrbel1,2, Jos I. Orellana1,2, Gabriela S. Olivares3, Roberto F. Nespolo2,4

1 Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile 2 Millennium Nucleus of Patagonia Limit-of-Life (LiLi), Valdivia, Chile 3 Universidad de Chile, Santiago, Chile 4 Universidad Austral de Chile, Valdivia, Chile

Mistletoes are a key component of most forest habitats, as they offer valuable fruit resources for animals during scarcity times. Despite their parasitic habits, mistletoes exert many positive effects in forest communities via indirect interactions. While our knowledge about plant-animal interactions in which mistletoes are involved is reasonably good, our knowledge about the plant-plant interactions that take place with their hosts remains limited. The temperate rainforests of southern South America are considered a biodiversity hotspot due to its highly-endemic relic flora. There are two common mistletoe species at those forests:Tristerix corymbosus, a highly-abundant generalist mistletoe in the evergreen forests, andDesmaria mutabilis, a deciduous mistletoe that parasitizes onlyNothofagustrees. Those mistletoes are almost exclusively dispersed by the relict arboreal marsupialDromiciops gliroides. While both mistletoes are sympatric at mid-elevations, where we foundT. corymbosusinNothofagusspp. trees by parasitizingD. mutabilis(hyperparasitism), asD. gliroidesfeeds simultaneously on both species during the austral summer. However, above 1250 m of elevation onlyD. mutabilisis found as forest vegetation change from evergreen to deciduous. From 1250 m until the forest treeline (~1600 m) the deciduous treeNothofagus pumiliobecomes dominant, concentrating most ofD. mutabilisplants. The presence ofD. mutabilisrepresents a major food source forD. gliroidesat those forests, where other fleshy-fruited plants are nearly absent. We recorded manyD. gliroidesvisits to those mistletoes using camera traps, even at temperatures as low as -6C, as mistletoes generate amenable microclimatic conditions. BesidesD. gliroides, we recorded many other animal species associated withD. mutabilis(e.g., parrots).Whereas both mistletoes play a key role in southern South America temperate rainforests,D. mutabilisis particularly relevant in high-mountain forests where food is limiting and environmental variations are broaderthan in the evergreen forests.