Climbing aroids in a Panamanian lowland forest: We should reconsider our categories

Abstract

AbstractBackgroundIn contrast to woody climbers, information on community composition or vertical extension within the forest is scarce for herbaceous climbers, even in well‐studied field sites like Barro Colorado Island. Moreover, questions regarding ontogenetic patterns (site of germination, changes in root/shoot connection with the soil) are unresolved because of a lack of field data.LocationBarro Colorado Island, Panama.MethodsIn 17 plots of 400 m2 each, which were distributed all over the island, we recorded all potential hosts (trees, palms, lianas) with a diameter at breast height larger than 1 cm, and all climbing aroids attached to them. For aroids, we recorded species identity, number of shoots, root connections to the ground, and vertical shoot extension. By distinguishing three size classes for each species in our analyses we deduced the site of germination and ontogenetic changes in the root/shoot connection with the soil.ResultsOnly 16% of all potential hosts were occupied by climbing aroids. We recorded 1196 individuals of 17 species. Aroids preferred larger trees and old‐growth forest. Species differed strongly in vertical distribution. Hemiepiphytic species germinate epiphytically, often high up in tree crowns and later establish root contact with the soil, while the majority of species establish on or close to the ground and reach moderate heights of 5–15 m (forest height ca. 35 m). In all of these species, we observed dieback of the proximal portion of the shoot to a varying extent but contact with the soil was invariably retained via adventitious roots.ConclusionsWe provide rare quantitative data on species richness and abundance of herbaceous climbers in a tropical lowland forest. Few species fall neatly into the categories of vines, nomadic vines and hemiepiphytes. This highlights the need for longitudinal observational and experimental studies to resolve the current debate on the appropriate grouping of these climbers.