DOI: 10.5061/dryad.jm63xsjcc
title: Floristic composition in three different forest types in western Amazonia

description: Aim: The latitudinal gradient is considered a first-order
 biogeographical pattern for most taxonomic groups. Yet, latitudinal
 changes in plant ecological communities are not always consistent, and
 this could be related to the physical and biological characteristics of
 different forest types. In this study, we compare latitudinal
 changes in floristic diversity (alpha diversity), composition (beta
 diversity), and dominance across different tropical forest types:
 floodplain, terra firme, and submontane forests.  Location:
 Western Amazonia (Ecuador, Peru, and Bolivia). Taxon: Woody
 plants.  Methods: We inventoried 1,978 species and 31,203
 individuals of vascular plants with a diameter at breast height ≥ 2.5 cm
 in 118 0.1-ha plots over a 1,800-km latitudinal gradient in three
 different forest types. The relationships between alpha diversity,
 latitude, and forest type were analysed using generalised linear mixed
 models (GLMMs). Semi-parametric permutational multivariate analysis of
 variance was used to investigate the effects of latitude and forest type
 on beta diversity. Dominant species abundances were correlated with
 non-metric multidimensional scaling ordination axes to reflect their
 contributions in shaping changes in beta diversity.  Results:
 Alpha diversity increased towards equatorial latitudes in terra firme and
 submontane forests but remained relatively constant in floodplains. Beta
 diversity of all forest types changed with latitude, although less clearly
 in floodplains. Overall, the abundances of dominant species decreased
 towards the Equator, though in floodplains they were more homogeneous
 along the gradient. Main conclusions: Alpha diversity, beta diversity and
 dominance patterns differed across forest types. In floodplain forests,
 the flooding regime is a strong predictor of floristic composition, which
 maintains alpha diversity constant along the latitudinal gradient.
 However, alpha and beta diversity in unflooded forests increase steadily
 towards equatorial latitudes. Furthermore, we found fewer dominant species
 contributing to changes beta diversity in floodplain forests. Shifts in
 abundance of dominant species over gradients can explain how beta
 diversity is driven differently per forest type.
description: We selected 13 western
 Amazonian forest regions ranging from Ecuador to
 Bolivia. Regions were located throughout a 1,800-km
 latitudinal gradient. The forest
 regions encompassed one or two different forest types comprising
 floodplains, <em>terra</em> <em>firme</em>,
 and submontane forests. In each region, six to 14
 0.1-ha plots were established according to a standard sampling protocol.
 Plots (50 × 20 m) were located at least 300 m apart, and areas affected by
 human and natural disturbances were avoided. Overall, we sampled 118 plots
 in floodplain (n = 27), <em>terra</em>
 <em>firme</em> (n = 51), and submontane (n = 40) forests. In
 each plot, we measured and inventoried all individual woody plants (trees,
 palms, tree ferns, and lianas) with DBH ≥ 2.5 cm rooted within the plot
 limits. The 118 0.1-ha plots contained 31,20 individual woody plants with
 DBH ≥ 2.5 cm, and 1,978 species that belonged to 557 genera and 112
 families. 
description: Taxonomic standardisation of species names was based on the Plant
 List using the R package ‘Taxonstand’.