DOI: 10.5061/dryad.612jm640h
title: Fragmentation reduces community-wide taxonomic and functional diversity of dispersed tree seeds in the Central Amazon

description: The Amazon harbors one of the most diverse tree floras on earth,
 and most species depend on mutualists for pollination and seed
 dispersal. This makes them susceptible to reproductive decline in
 fragmented forest because many of these mutualists suffer
 area-related extinction in fragments. It remains unknown,
 however, whether this highly biodiverse tree flora will reproduce
 and ultimately persist in fragmented forest. We conducted a
 two-year study of seed-fall in an
 experimentallyfragmented, highly-diverse Central Amazonian
 forest. We determined the effect of fragment size (1 ha, 10 ha,
 100 ha and continuous forest control) on the density, species
 richness, functional diversity and functional composition of
 seeds separated into two datasets: dispersed tree seeds, and
 undispersed tree seeds. Our results show a 3x reduction in the
 density of undispersed, non-pioneer tree seeds in fragments of
 all sizes, indicating reduced seed production of the non-pioneer
 tree community. The density of dispersed tree seeds was 6x
 reduced in fragments of all sizes, while species richness was 6x
 reduced in 1 ha fragments and 3x reduced in 10 ha and 100 ha
 fragments compared to intact forest. This provides evidence of
 reduced community-wide seed dispersal, which became more
 pronounced with declining fragment size. The functional diversity
 (FRic) of dispersed tree seeds was 9.6x reduced in small
 fragments, and significant shifts in the functional composition
 for 8 of the 10 reproductive and ecological traits studied were
 identified, suggesting compromised ecosystem functioning. These
 functional compositional shifts provide evidence for disrupted
 mutualistic processes in fragments, which include loss of
 pollination by bees, especially small eusocial (meliponid) bees,
 and loss of dispersal by primates and large birds, which reduced
 the frequency of large-seeded tree species. Fragments also lost
 rare and mature-forest species, and collectively these changes
 suggest that future tree communities in fragmented Amazonian
 landscapes will retain a taxonomically- and
 functionallyimpoverished species pool with a biased functional
 composition unless efforts are undertaken to conserve dispersal
 by large frugivores and pollination by meliponid bees.
description: Experimental design Plot (1 ha)
 establishment.— We established a total of 11 one hectare plots in the
 centers of fragments of different sizes (1 ha, 10 ha, and 100 ha) and
 intact forest controls. These plots were located at three cattle ranches
 (Dimona, Porto Alegre and Esteio), and two areas of continuous forest (Km
 37 and Km 41). Three plots were established in three different 1 ha
 fragments at two ranches (Dimona and Porto Alegre), two plots were
 established in the centers of 10 ha fragments located at two different
 ranches (Esteio, Porto Alegre), two plots were established in the centers
 of 100 ha fragments located at two different ranches (Dimona, Porto
 Alegre), and four were located in continuous forest controls, two at each
 of the two different sites (Km 37 and Km 41). We therefore had a
 fully-replicated experimental design with respect to fragment size at the
 plot level. The number of plots we established in each fragment size was
 constrained by the number of isolated fragments that are available at the
 BDFFP; we utilized all the 100 ha fragments, two of the three 10 ha
 fragments, and all the 1 ha fragments available. Seed
 trap establishment.— Seed traps were part of a broader experimental
 framework which included 10 m2 subplots established to document seedlings;
 each had an associated seed trap. For plots located in 1 ha fragments, a
 transect was extended perpendicular to the forest edge into the forest
 fragment, while for plots located in the centers of the 10 ha and 100 ha
 fragments and continuous forest, a transect was extended perpendicular
 from one randomly located plot boundary. In each plot, we placed eight 10
 m2 seedling subplots (71 cm x 14.2 m) at 4 distances (13 m, 29 m, 52 m,
 and 81 m) from the fragment edge / plot boundary with two replicates at
 each of these distances (Fig. 1). Subplot placement at each distance was
 located randomly, with the constraint that the second replicate must be
 located at least 20 m from the first (so that canopies of different trees
 would be over each subplot, therefore making each a true replicate with
 regards to seed dispersal), and neither could be closer than 20 m from the
 side of the plot. One 0.5 m2 seed trap (71 cm x 71 cm, elevated 0.5 m
 above the ground) was located one meter from one randomly-chosen side of
 each of these seedling subplots. In total, 88 seed traps were
 utilized. Data collection.—We visited each seed trap at
 approximately monthly census intervals for two years (2005 – 2006; 2007 –
 2008). At each visit, we counted all seeds and determined their origin as
 either undispersed or dispersed. Each seed encountered was photographed,
 measured, and identified to species level, or given a morphospecies
 designation. For all analyses, we used the total number of seeds per seed
 trap, summed over all census intervals during the two years. More details
 on plot and seed trap placement, methodology to determine whether tree
 seeds were dispersed or undispersed and taxonomic identification are given
 in Appendix S2. Seed rain functional classification.—
 All tree species were functionally classified, using ten traits describing
 key reproductive and ecological characteristics (Appendix S1).
 Reproductive traits included (i) reproductive strategy, (ii) pollination
 vector, (iii) bee-pollination vector (a subset of ii which delineates five
 bee guilds), (iv) seed size category, (v) seed dispersal syndrome, (vi)
 primary dispersal vector, and (vii) secondary dispersal vector. Ecological
 traits included (viii) successional status, (ix) adult abundance in intact
 forest (rarity), and (x) maximum adult tree height. For each of the 10
 functional traits, the assignment of trait state for each species was
 based on data collected from seed traps (trait iv), BDFFP phytodemographic
 data (W. F. Laurance pers. comm.) (trait ix), and for all other traits we
 used published information, detailed in Appendix S3: Tables S1–S7. More
 details on functional classification are found in Appendix S2 and Appendix
 S3. Functional diversity (FD) indices.— We used three
 complementary functional diversity (FD) indices, which together describe
 the distribution of species and their abundances within functional trait
 space. These indices include: 1) functional richness (FRic), the volume of
 functional trait space occupied by species in a community; 2) functional
 evenness (FEve), the evenness of species abundance distribution within
 functional trait space; and 3) functional divergence (FDiv), how far
 species abundances diverge from the center of functional trait space
 (Villéger et al. 2008). To compute these three FD indices, we used the
 dbFD function in the FD package in R (Laliberté and Legendre 2010). We
 pooled the data for the 8 seed traps found in each plot, and calculated
 these indices per plot. More details on functional diversity computation
 are found in Appendices S2 and S4.