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PROPAGULE DISPERSAL BY LARGE MAMMALS TAKEN TO THE NEXT LEVEL: WHITE-LIPPED PECCARIES AS DISPERSERS OF ROOT MUTUALISTS IN THE ATLANTIC FOREST
Small and large mammals play crucial roles in seed dispersal, plant diversity and community structure. Less known is the role of mammals as dispersers of fungi that are associated with the roots of plants (mycorrhizal fungi) and form mutualist associations that improve the plants acquisition of soil nutrients and water and protect them against pathogens. In most tropical forests, arbuscular mycorrhizal (AM) fungi (Glomeromycota clade) dominate the root mutualist communities by forming beneficial associations with 90% of the plants. These fungi, different from other groups of mycorrhizal fungi, do not produce large and tasty truffles and mushrooms and do not exhibit any clear mechanisms to discharge spores in the air or to attract dispersers. Nevertheless, AM fungi are still widely spread across different ecosystems worldwide by mechanisms that are poorly understood. In this study, we then asked (i) are small and large mammals important AM fungi dispersers across ecosystems? and (ii) what would be the consequence of the loss of large mammals for the abundance and richness of these important plant mutualists in the Atlantic forest? To answer the first question, we performed an extensive literature review searching for evidence of AM fungi dispersal by different groups of vectors (biotic and abiotic). We found 37 papers that have recorded spores of AM fungi in scat, stomach, fur, feet, air and water samples, in a total of 270 observations. Small mammals were the most studied group (44.4% of all observations) with more than 100 species being surveyed. From the small mammal observations, 69.7% had viable/alive spores of AM fungi, with around 18 AM fungal morphospecies being morphologically identified. On the other hand, large mammals were highly overlooked, with only 4 observations from this group across the globe. To answer our second question, we took advantage of long-term experiment in the Atlantic forest to investigate the diversity of AM fungal spores in the soil of exclosure plots (where large-mammals do not have access for nine years) and paired open plots. We found that the number and richness of AM fungal spores were significantly lower in the exclosure plots. We also observed through camera trapping that white-lipped peccaries (Tayasu pecari) are the most dominant large-mammal in the studied area. By analysing the presence of spores and DNA in scat samples from these animals, we confirm that they can ingest great quantities of spores and colonized root fragments and transport the fungal plant partner across the landscape. These results show the huge potential of large mammals as dispersers of root mutualist fungi and the need to expand this knowledge to other mammal and non-mammal groups. We also highlight that the loss or reduction in the populations of such mammals may be triggering a much profound trophic cascade because it is not only harmful for the seed dispersal and community structure of plants, but also for the plants’ interactions with beneficial soil organisms.
Mycorrhizal fungi; Herbivores, Mutualism.
FAPESP (Fundação de Amparo a Pesquisa do Estado de São Paulo)
FAPESP – 2016/25197-0 (Claudia Paz)
FAPESP – 2018/00212-1 (Leticia Cagnoni)
FAPESP -- 2015/11521-7 (Nacho Villar)
Biologia da Conservação
CLAUDIA PANDOLFO PAZ, LETICIA BULASCOSCHI CAGNONI, NACHO VILLAR, PAULA AKKAWI, MAURO GALETTI RODRIGUES