Regional and Fine Scale Variation of Holoepiphyte Community Structure in Central Amazonian White‐Sand Forests

Abstract

Factors controlling holoepiphyte (plants which start and complete their life cycle on a phorophyte) distributions may be wide and variable. They are determined either by spatial processes, as evidenced by dispersal limitation and/or historical factors, environmental filters, such as microsite variation within phorophytes, and/or biotic interactions. Disentangling the importance of these classes is particularly difficult in tropical forests where phorophyte alpha‐diversity is exceptionally high. We controlled for phorophyte specificity by studying the holoepiphytic communities of an emergent tree Aldina heterophylla (Fabaceae), known for its heavy epiphyte loads and dominance in Amazonian white‐sand habitats, in order to quantify the importance of tree zone and geographic distance on holoepiphytes at fine (100 m2) and regional (2500 km2) scales. At regional scales, tree zone explained nearly two‐thirds of the main compositional gradient, accounting for more than double that of site differences. No spatial effects were observed on holoepiphyte community structure at the fine scale as treelet communities were more dissimilar than by chance alone from their neighboring emergent phorophyte. These results suggest that microsite availability, as opposed to dispersal limitation, is the most important mechanism in structuring holoepiphyte communities of this insular forest type.

What do tropical cryptogams reveal? Strong genetic structure in Amazonian bryophytes

“…In the present sample, B. hookeri , T. amazonicus , S. annotinus, and S. helicophyllus were, for instance, completely or largely (< 2 specimens) restricted to white‐sand forests. Furthermore, white‐sand forests host substantially heavier epiphyte loads characterized by different species communities than those of other Amazonian forest types due to narrow host specificity (Cornelissen & ter Steege, 1989; Benavides et al ., 2016; Marí et al ., 2016). Therefore, although the selected species were either epiphytic ( A. juliformis , T. amazonicus , S. helicophyllus , and S. hornschuchii ), epiphytic or epixylic on dead logs ( B. hookeri , M. trachyphyllum , L. martianum , O. albidum , O. pulvinatum , S. simmondsii ), or ground‐dwelling ( S. annotinus ), the differentiation between terra firme and white‐sand forests provided a major habitat differentiation for the three sampled functional groups in the six remaining species, which occurred in both forest types, and wherein we sought a signature of ecotypification.…”

Composition, diversity and structure of vascular epiphytes in two contrasting Central Amazonian floodplain ecosystems

“…However, even in these environments, vascular epiphytes are neglected in conservation action plans, which mostly focus on arboreal species (Obermüller et al 2012). Epiphytes are also poorly sampled in other Amazonian environments, including savannas (Gottsberger & Morawetz 1993), coastal forests (Quaresma & Jardim 2014) and white-sand forests (Steege & Cornelissen 1989;Mari et al 2016) Composition, diversity and structure of vascular epiphytes in two contrasting Central Amazonian floodplain ecosystems While vascular epiphytes are visually highly abundant in Amazonian floodplain forests, to the best of our knowledge there are only two studies that investigated species composition and richness. Nieder et al (2000), in 1.5 ha of a igapó forest along of the Suromoni River, Venezuelan Amazon, reported 778 individuals belonging to 53 epiphyte species, where orchids (19 species) and aroids (15 species) were the most abundant families.…”

Logging impact on Amazonian white-sand forests: perspectives from a sustainable development reserve

“…Family ACTA AMAZONICA is also one of the ecologically most important species in these forests (Anderson, 1981;Targhetta et al 2015;Demarchi et al 2018), as it is one of the few species that reach similar basal area to species from terra-firme forests (Stropp et al 2011). Additionally, A. heterophylla in campinarana has important roles in the nitrogen fixation process (Mardegan et al 2009), as a substrate for the epiphytic community (Marí et al 2016), and as a facilitator of colonization by other species under its shade, as its canopy width can reach up to two times its height (Anderson et al 1975).…”