Community of arbuscular mycorrhizal fungi in fragments of tropical rainforest

Background/Question/Methods Effects of fragmentation on belowground communities are not clear. Arbuscular mycorrhizal (AM) fungi community does not seem to be strongly affected by fragmentation, probably because herbs and grasses play an important role for their maintenance or land use change from forest to pasture or crop is not the key factor to modify the community structure of these fungi. However, fungi species composition can change, and due to its close relationship, where a fungi species provides different quantities of nutrients depending on plant species, plant composition and diversity also can vary. The main goal of this study was to characterize AM fungi community from different size fragments of tropical rain forest and to compare them. We selected seven fragments, two large, two medium and three small in Los Tuxtlas region, Veracruz, Mexico. We collected 14 compound soil samples for fragment, they were air dried, we weighted 100 g of dry soil and all spores were separated; they were identified and counted.

Results/Conclusions The least abundant and frequent AM fungi species were Glomus sp1, Scutellospora heterogama, Acaulospora laevis, Glomus sp2, and Glomus sp4; whereas, the most abundant and registered in all fragments were Acaulospora spinosa, Glomus claroideum, Glomus sinuosum, Acaulospora scrobiculata, Glomus tenebrosum, and Glomus verruculosum. Estimated species richness, Simpson diversity index and Bray-Curtis similarity index were calculated. The smallest fragment presented the AM fungi highest estimated richness (91 species) while the largest fragments presented the lowest (29). However, there was a positive relationship between diversity and fragment size; the highest diversity value corresponded to the largest fragment. The smallest fragment shared more than 50% of species with the other fragments. Distance seems to be an important factor to explain these results, not size. But also it is clear that AM fungi community presents a great resistance to fragmentation effects, and may be these are more related to the interaction performance.