Tropical forest landscape dynamics: population consequences for Neotropical lianas, genus Passiflora

When populations occur in ephemeral patches, such as treefall gaps, rapid changes in patch quality may affect colonization processes. I asked what effect patch quality dynamics and propagule dispersal would have on colonization by Passiflora vines that establish in canopy gaps in lowland rainforests of Corcovado National Park, Costa Rica. Passiflora vine recruitment required high patch quality, exceeding 3 hours of direct sunlight at ground level. Models of patch quality showed that canopy opening size and slope were significant factors associated with vine recruitment. Within 6 years of initial opening, seedling recruitment ceased as gap quality decreased by 13% per year due to canopy closure, and 8% per year due to understory regrowth. This ephemeral-patch system had low densities of new patches with sufficient lighting, and patch quality decreased rapidly resulting in a narrow temporal window for seedling establishment. Colonization by seed dispersal (80%) was constrained by patch quality and isolation, while clonal growth from dormant plants (20%) was limited to an infrequent appearance of adjacent patches. These results suggest that more realistic models of ephemeral-patch metapopulations should include distributions and transitions of patch quality based on organism requirements rather than simplistic assignments of patch suitability.