Navegando por Autor "Carrión, Juan Fernando"

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Facilitation as a driver of plant assemblages in Caatinga
(Journal of Arid Environments, 2017-07) Carrión, Juan Fernando; Gastauer, Markus; Mota, Nayara Mesquita; Meira-Neto, João Augusto Alves
Nurse plants reduce the environmental severity experienced by neighboring plants by providing shade, enabling nutrient accumulation or protection from herbivores within patches of vegetation. Nurse plants should preferentially promote the coexistence of ecologically dissimilar species with little niche overlap, and if ecological traits are conserved within evolutionary lineages, this should result in phylogenetic overdispersion. In contrast to competition, facilitation is expected to increase species richness. Therefore, to examine the role of facilitation as a driver of plant assemblages in Caatinga, we quantified the functional traits of nurse species and compared species richness, phylogenetic diversity, phylogenetic structure of the tree layer and of the herbaceous layer between patchy Caatinga and Caatinga with segregated plants. Results show that functional traits related to resilience and resistance against herbivory seem to be crucial for facilitation in Caatinga. Autochory occurs at a higher frequency in nurse plants than in Caatinga in general. The herbaceous layer of patchy Caatinga is richer in species than of Caatinga with segregated plants, and facilitation is the suggested cause. As the whole community of the 196 patches is phylogenetically overdispersed compared to the null expectations, facilitation seems to predominantly promote the coexistence of dissimilar species with little niche overlap.
Phylogenetic structure is determined by patch size in rock outcrop vegetation on an inselberg in the northern Amazon region
(Acta Amazonica, 2018-07) Villa, Pedro Manuel; Gastauer, Markus; Martins, Sebastião Venâncio; Carrión, Juan Fernando; Campos, Prímula Viana; Heringer, Gustavo; Meira-Neto, João Augusto Alves; Rodrigues, Alice Cristina
Although inselbergs from around the world are iconic ecosystems, little is known on the underlying mechanisms of community assembly, especially in their characteristic patchy outcrop vegetation. Environmental constraints are expected to cause phylogenetic clustering when ecological niches are conserved within evolutionary lineages. We tested whether vegetation patches from rock outcrops of the Piedra La Tortuga Natural Monument, in the northern Amazon region, are phylogenetically clustered, indicating that environmental filtering is the dominant driver of community assemblage therein. We classified all patches according to their size as very small (< 1 m 2 ), small (1-4 m 2 ), medium-sized (4-8 m 2 ), and large patches (8-15 m 2 ). From each class, we randomly selected 10 patches, totalizing 40 patches covering 226 m 2 . All individuals found in the 40 isolated patches were identified to the species level. We also correlated measurements of phylogenetic community structure with patch size. We found that species from patches are restricted to the clades monocots, fabids, malvids, and lamiids. We conclude that vegetation in this rock outcrop is phylogenetically clustered. Furthermore, we found that phylogenetic turnover between pairs of patches increases with patch size, which is consistent with a scenario of higher environmental stress in smaller patches. Further research is necessary to identify nurse species in inselberg vegetation, which is pivotal for conservation and restoration of this particular ecosystem.