DOI: 10.5061/dryad.0cfxpnw3v
title: Life on a leaf: the development of spatial structure in epiphyll communities

description: 1. The spatial structure of biotic communities can be shaped by
 niche-based or stochastic processes, and the importance of both can change
 through time. Niche-based processes include neighbour interactions, which
 can change in intensity and quality as communities develop in dependence
 of environmental conditions. Epiphylls, miniature communities of
 liverworts, lichens, algae and fungi on leaves, develop only in relatively
 moist forests, but their leaf-surface habitat is still characterised by
 moisture stress, especially in more exposed parts of the forest. As
 neighbours may alleviate moisture stress, we expected that in forest gaps
 (dryer, brighter) epiphyll communities would show more positive neighbour
 interactions, resulting in more clustered spatial patterns, than in closed
 forest, in accordance with the stress-gradient hypothesis. 2. To
 understand how the processes shaping epiphyll communities change through
 time and differ between gaps and closed forest, we examined the fine-scale
 spatial structure within and between epiphyll functional groups (algae,
 fungi, lichens, liverworts) during 12 months on 60 leaves across twelve
 sites in a tropical rainforest in Panama. We analysed changes in spatial
 positions and spatial associations within and between functional groups
 using spatial point pattern analysis based on repeated photography. 3.
 Epiphyll densities increased through time for most epiphyll functional
 groups. However, although epiphyll groups changed their positions through
 time, the general types of spatial patterns remained similar for most
 groups: only lichen patterns shifted from mostly random to mostly
 aggregated through time. We found only random and aggregated spatial
 patterns within groups, while among groups we additionally found
 segregated spatial associations, but no consistent temporal trend.
 Patterns did not differ between gaps and closed forest, thus not
 supporting the stress-gradient hypothesis. 4. Synthesis. Our results only
 weakly support the assumption that community-shaping processes change from
 neutral to niche-based as communities develop. We do provide empirical
 evidence that epiphyll communities are dynamic and exhibit different
 spatial association patterns within than among groups. This suggests
 different interactions and processes within than between groups.
 Experimental studies and monitoring of individual epiphyll patches are
 recommended to shed further light on what processes shape life on leaves.
description: The dataset was collected based on  digital photographies with
 tree or shrub leaves with epiphylls, taken four times a year from the same
 leaves in tropical rainforest on Barro Colorado island, Panama from the
 November 2016 till November 2017. Each digital photography was processed
 with Arcmap programme, where each epiphyll functional group patch (fungi,
 algae, lichens, liverworts) and leaf  shapes were mapped manually. For
 spatial data analysis, centroids were calculated of each epiphyll
 functional group patch.  
description: The dataset was exported from Arcmap programme and consists of
 spatial data files (shp) which can be processed with GIS programmes.
 Explanatory file (txt) is attached to uploaded files.