Fine‐scale changes in connectivity affect the metapopulation dynamics of a bryophyte confined to ephemeral patches

Abstract

Summary 1.We test how fine-scale (£ 400 m 2 ) connectivity to conspecifics influences metapopulation dynamics using a field experiment in central Amazonia with the epiphyllous (i.e. leaf-inhabiting) bryophyte Radula flaccida Gott. (Radulaceae). This is a natural model system with spatially structured ephemeral patches at the leaf and phorophyte scale. 2. The aim was to test how the rates of leaf colonization, local abundance, growth and extinction of bryophytes from both leaves and host phorophytes were affected by experimentally manipulated variation in connectivity to conspecifics. We also investigated the relative importance of local stochastic extinctions and deterministic extinctions at both spatial scales.3. Approximately 3500 leaves on 70 phorophytes were censused six times over a 15-month period by utilizing a repeated block design with control, positive control and three pulse-style reduction treatments, which varied in connectivity to surrounding conspecifics.4. An increase in stochastic extinction events was only accompanied by a reduction in colonization in the treatment in which focal and neighbouring phorophytes within the 400 m 2 plots were experimentally denuded of their natural populations, suggesting that epiphyllous cryptogams are subject to fine-scale (within phorophyte) rescue effects. Negative density-dependent growth was also detected in within-leaf population dynamics, suggesting that resource limitation or intraspecific competition influences local population growth. Finally, stochastic extinctions from viable leaves occurred with nearly the same frequency as deterministic events (e.g. leaf fall), whereas at the phorophyte scale only stochastic extinctions were observed. 5. Synthesis. The experiment demonstrates that rescue effects occur at fine scales even for vagile plant taxa, such as cryptogams, which may inhabit spatially isolated substrates characterized by turnover rates as fast as their own population dynamics. Furthermore, the results highlight the importance of quantifying both stochastic and deterministic extinction modes, as underestimating either of these parameters leads to over optimistic projections of future metapopulation size.

A model for non‐equilibrium metapopulation dynamics utilizing data on species occupancy, patch ages and landscape history

“…Nevertheless, significant stochastic extinction rates have been observed at the tree level in certain foliose epiphytic lichens (Fedrowitz, Kuusinen & Snäll ), in an epiphyllous bryophyte (Zartman et al . ) and in epixylic lichens (Caruso, Thor & Snäll ). Among ground‐floor vascular plants, the extinction rate at stand level varies (Verheyen et al .…”

Local epiphyte establishment and future metapopulation dynamics in landscapes with different spatiotemporal properties

“…, Zartman et al. ). For instance, Öckinger and Nilsson () reported shorter local L. pulmonaria population longevities than the estimated longevity of the long‐lived trees of formerly grazed areas that had developed into secondary woodlands.…”

How does reproductive strategy influence demography? A case study in the tropical, unisexual epiphyllous moss Crossomitrium patrisiae

“…Reproductive strategies -Evidence from experimental studies of fine-scale metapopulation dynamics of epiphylls indicates that patch extinction and colonization are disproportionately aff ected by within-as compared to among-phorophyte variation of neighborhood patch density of epiphyll conspecifi cs ( Zartman et al, 2012 ). Bryophyte spore dispersal has repeatedly been demonstrated to be strongly leptokurtic with the vast majority (ca.…”