Fig 1.
Summarizing scheme of the expected trends with increasing branch diameter.
We expect a decrease in water stress, mechanical disturbance and branch abundance with an increasing branch diameter. These drivers plus the increase in branch age should lead to higher epiphyte colonization and survival and an increase in epiphyte abundance, richness and proportion of adults per branch.
Fig 2.
Branch abundances as a function of branch diameter.
A) Brazilian core transects (n = 30). B) Brazilian edge transects (n = 30). C) Panamanian transects (n = 36). Box-plots show the median as central line, the first and third quantiles as the bottom and top box limits, 1.5 interquantile range as whiskers, and outliers as circles. Solid lines show fits from GAMMs with 95% CI indicated by dashed lines.
Table 1.
Comparisons between study sites. Several measures characterizing forest structure, branch abundance, epiphyte abundance and epiphyte richness.
Fig 3.
Species accumulation curves based on forest floor-based sampling of epiphytes.
A) Brazilian core transects (n = 30). B) Brazilian edge transects (n = 30). C) Panamanian transects, excluding ferns and aroids (n = 36). D) Panamanian transects, all species (n = 36). Solid curves give the mean number of species based on 100 randomized samplings, dashed curves the 95% CI. Horizontal lines indicate the number of species present in the canopy of the transects (thin lines), in the study site (thick lines, same estimate for both Brazilian study sites) and on substrate < 10 cm in diameter (dot line, in c and d). See S1 Table for the list of species found in the transects and S2 Table for species lists found in the study sites. Note that the Brazilian study sites showed curves leveling off, whereas the Panamanian site revealed a slightly steeper curve in agreement with the higher number of species.
Fig 4.
Absolute epiphyte abundance (A-C) and richness (D-F) per transect as a function of branch diameter.
Trends are shown for Brazilian core (A,D, n = 30), Brazilian edge (B,E, n = 30), and Panamanian (C,F, n = 36) transects. Box-plots show the median as central line, 1.5 interquantile range as whiskers, and outliers as circles. Solid lines give the values predicted by the estimated GAMMs, dashed lines show 95% CI. Note that the number of epiphytes was generally hump-shaped along diameter classes in Brazilian transects, whereas it was positive in Panamanian transects.
Fig 5.
Epiphyte abundance (A-C) and richness (D-F) per branch as a function of branch diameter.
Trends are shown for Brazilian core (A,D, n = 26), Brazilian edge (B,E, n = 21), and Panamanian (C,F, n = 25) transects. Box-plots show the median as central line, 1.5 interquantile range as whiskers, and outliers as circles. Solid lines give the values predicted by the estimated GAMMs. Dashed lines show 95% CI.
Fig 6.
Proportion of adults as a function of branch diameter.
A) Brazilian core transects (n = 30). B) Brazilian edge transects (n = 30). C) Panamanian transects (n = 36). Box-plots show the median as central line, 1.5 interquantile range as whiskers, and outliers as circles. Solid lines give the values predicted by the estimated GAMMs. Dashed lines show 95% CI.
Fig 7.
Epiphytes in the canopy and their relationship with forest floor trends.
(A) epiphyte abundance and (B) species richness in the canopy directly above the Panamanian transects (n = 29) as a function of branch diameter. Proportion of individuals (C) and species (D) found on the forest floor compared to the transects' total abundance (forest floor and canopy). (E-F) Non-metric multidimensional scaling of transects based on species composition and abundance considering (E) all individuals found on the forest floor and canopy (n = 18 forest floor and canopy pairs) and (F) only individuals on substrate < 10 cm in diameter (n = 17). Forest floor and canopy pairs are indicated by the same numbers in E-F (legend in F). See S2 File for the number of individuals and species censed within the whole crane plot (c. 0.9 ha). Solid lines give the values predicted by the estimated GAMMs, whereas dashed lines show 95% CI in A-D. Lines connecting numbers indicate convex hulls in D-F. We excluded the thinnest branch diameter class in C and D due to overall low abundances in the canopy (see A-B). Box-plots show the median as central line, 1.5 interquantile range as whiskers, and outliers as circles.