Differences in the degree of environmental control on large and small tropical plants: just a sampling effect?

Abstract

Summary 1.Tropical rain forest tree species are commonly perceived to have more generalized habitat distributions than understorey species. However, the correspondence between floristic patterns in large trees and smaller understorey plants in relation to environmental differences has rarely been investigated. Comparative analyses are complicated by the fact that tree data are often much more noisy, with higher overall species richness and poorer spatial and temporal representation of species composition within sampling plots. 2. Using data on trees and pteridophytes collected in 1125 plots located within 6 km 2 of lowland rain forest in Costa Rica, we asked: (i) Is there evidence that trees are more generalized in their edaphic and topographic distributions than pteridophytes, and (ii) How much might differences in sampling efficiency affect the results? 3. We ran community-level analyses using Mantel tests, and for the five most frequent tree and pteridophyte species we ran logistic regression analyses of species occurrence. To investigate the influence of differing sampling efficiency, the analyses were repeated with four rarefied pteridophyte data sets approximating key structural features of the tree data set. 4. Differences in community composition in trees and in all pteridophyte data sets were most strongly correlated with environmental differences in the same five soil variables. The most frequent species in both plant groups had non-random edaphic and topographic distributions. 5. Both Mantel correlations and the predictive performance of single species models (AUC values) were higher for the full pteridophyte data set than for trees, but these differences were much reduced after pteridophyte rarefaction. 6. The performance of the species occurrence models calibrated with rarefied pteridophyte data appeared poor when tested on rarefied data. However, their performance in predicting occurrences in the full data set was usually moderate (AUC > 0.70). This suggests that the tree species models may also predict species' potential habitat distributions better than is apparent from their AUC values. 7. Synthesis . Our results indicate that rain forest trees and pteridophytes may respond to mesoscale environmental variation in qualitatively similar ways, but that trees will appear much more generalized in their response to the environment unless differences in sampling efficiency are taken into account.

Disentangling environmental and spatial processes of community assembly in tropical forests from local to regional scales

“…This seems to be true for the average trend, as wells as for the majority of sub‐regions. Our results are in agreement with previous studies in tropical forests that have found similar patterns in regions spanning a broad range of spatial extents (Phillips et al , Macía et al , Ruokolainen et al , Jones et al , Myers et al ). While the amount of compositional variation explained exclusively by environment increases with spatial extent in our study system, the variation explained solely by spatial predictors remains constant (Fig.…”

Modelling responses of western Amazonian palms to soil nutrients

“…; Chust et al . ), although size‐dependent differences in data quality may affect the observed patterns (Jones, Tuomisto & Olivas ). It is intriguing that our models suggest canopy palms to exhibit a significantly higher mean optimum response to soil P but not to exchangeable bases or B when compared to understorey palms.…”

Lycophytes and ferns composition of Atlantic Forest conservation units in western Paraná with comparisons to other areas in southern Brazil

“…Thus, also in the four areas under study in western Paraná, the greatest similarity was found between fragments with the same forest formation. Additionally, other factors could influence this similarity, such as environmental heterogeneity (Jones et al 2006;Gasper et al 2012) and disturbance history (Jones et al 2008;Nóbrega et al 2011).…”