Estimates of epiphyllous population size dynamics
Data from the epiphyllous metacommunity sampling collected in the year
2000 (Zartman, 2003) and 2016 (Sierra et al., 2019b) were used as
baseline information on demographic changes accountable to fragmentation
in this study. The two focal leafy liverworts species selected,Radula flaccida Lindenb. & Gott. (Radulaceae) andCololejeunea surinamensis Tixier (Lejeuneaceae), are regionally
and locally abundant across the landscape (Sierra et al., 2019b). At
BDFFP, both species predominantly occur on understory leaves of young
trees and shrubs (Figure S2A, E). Colonies of R. flaccida andC. surinamensis are typically found with sexual reproductive
structures (male: androecia or/and female: gynoecia/sporophytes), and
specialized asexual propagules (gemmae). Nevertheless, the two species
differ in the mating system where R. flaccida is unisexual andC. surinamensis is bisexual (Figure S2). These species were
chosen due to their: (i) comparatively higher local population densities
relative to the other 74 epiphyllous species known from BDFFP (Zartman,
2003; Sierra et al., 2019b); (ii) distinct patterns in radial growth
allowing for clear spatial delimitation of colonies; (iii) the negative
effect of fragmentation on their local abundances (a characteristic this
species shares with a vast majority of the other epiphylls at the BDFFP,
see Sierra et al., 2019b); and (iv) empirical data for demographic
patterns over a 15-year interval (Sierra et al., 2019b) as well as for
associations between colonization and extinction with fragmented patches
from transplant experiments (Zartman & Shaw, 2006).
The number of colonies was estimated for a total of 22 study plots
(1-ha) distributed in 1-, 10-, 100-ha forest fragments, and in
continuous forest (Table S1); see Sierra et al., (2019b) for further
detail on the sampling design. The number of colonies was estimated for
each study plot by calculating the percentage of occupied host leaves by
the species (occupied patches) and multiplying by the total number of
host plants with epiphyllous colonies within the respective study plot
(suitable patches). This approach led us to accurately compare
population size among plots in the fragmented and continuous forest
avoiding sampling size bias. For each species, differences in the number
of colony estimates were compared among small (1- and 10- ha), and large
patches (100- ha fragments and continuous forests) over time from the
years 2000 and 2016 using the non-parametric Wilcoxon rank sum exact
test. Likewise, was compared tested if the increase colony density
observed in small patches in the year 2016 reached similar values when
compared to large patches.