Not surprisingly, seedling density was negatively correlated with distance to the source (distance to source was up to 300 m Werner and Gradstein, 2008). Dispersal of epiphytes has been assessed indirectly by monitoring the establishment of new individuals in the vicinity of a seed source ( Werner and Gradstein 2008, 2009). Since it is difficult to quantify long-distance seed dispersal directly this has been rarely done (but see Bullock and Clarke 2000). Successful dispersal is a pre-requisite for long-term survival of epiphyte metacommunities. In this study, we investigated the bottleneck of dispersal and establishment of vascular epiphytes in such a modified landscape by breaking down this early life stage into four consecutive steps. Thus, long-distance seed dispersal is of critical importance for epiphytes, and flora in general (e.g. To guarantee a constant renewal of epiphyte populations in a fragmented landscape, the habitat fragments have to be sufficiently connected. For stochastic reasons local populations are typically bound to go extinct, but they can be rescued if they are connected with other populations which undergo asynchronous oscillations ( Tremblay et al. In the particular case of epiphytes, seeds may be dispersed within a host tree, among neighbouring trees in a forest patch, between forest patches or into uninhabitable parts in between. In their review on the вЂecology of seed dispersalвЂ™ Howe and Smallwood (1982) emphasize that the seeds of most species disperse only short distances on the order of tens of metres. In such a fragmented environment seed dispersal is a particularly critical process ( Bullock and Clarke 2000), because suitable safe sites are not necessarily close-by. Together the assemblages inhabiting these вЂislandsвЂ™ form a metacommunity. 2001 KrГ¶mer and Gradstein 2003 KГ¶ster et al. Epiphyte diversity is negatively affected by anthropogenic activities: the epiphytic habitats in modified landscapes, which typically consist of вЂislandsвЂ™ of small natural forest fragments, secondary forests, tree plantations and scattered solitary trees, usually have reduced species richness and a modified floristic composition dominated by xerotolerant species (e.g. Globally, they account for almost 10 % of all vascular plants ( Zotz 2013), but locally, in humid montane forests they can represent up to 50 % of the vascular flora ( Kelly et al. This contribution focuses on one of these biotic components, vascular epiphytes, which-by definition-depend on trees. This degradation of forest endangers all components of these ecosystems. In Central and South America, fragmentation of the remaining rainforests continues by conversion to agricultural land and wood removal ( FAO 2011). Although this is no new development at a local or regional scale, as example Forman (1987) quotes Plato (4th century B.C.) with a description of land overuse that left the land bare like a вЂmere skeletonвЂ™, but the current, global magnitude has led researchers to declare a global biodiversity crisis. Increasing human populations lead to massive alteration and fragmentation of native vegetation that remains in patches within the landscape (cp. A potentially regenerating forest may receive considerable input from sources such as pasture trees and in this way gain structural complexity, which also greatly enhances its value for other forest organisms.ДЇragmentation, land-use change, microclimate, seed dispersal, tropics Introduction The findings suggest a large capacity for dispersal and successful early establishment for these anemochorous species. Microclimatic differences between habitat types were marginal and neither germination nor establishment correlated significantly with annual precipitation. Germination success and early establishment of four bromeliad species did not differ between isolated trees, teak plantations or secondary forest patches. (iii and iv) Successful establishment is achieved when a seed germinates and a plantlet grows and survives. Even fine bark structure allowed effective attachment. (ii) We quantified attachment success of bromeliad seeds as a function of bark rugosity with >30 common tree species in the region. All measured V term of bromeliad and orchid seeds fell into a range of velocities with a high chance of long-distance dispersal.

(i) Seed falling velocity ( V term) is known to correlate with long-distance dispersal via convective updraft. We experimentally studied four vital steps of epiphyte dispersal in different habitat types in western Panama. A pre-requisite for the maintenance of a viable metacommunity in a fragmented landscape is the connectivity between habitable patches. The ongoing destruction of old-growth forests puts tropical forest species under great pressure because of the resulting habitat loss.

Zotz definition