In general, plant ecologists investigate the influence of abiotic factors on plant distribution, while plant-herbivore ecologists focus on the role of herbivores. Although relatively few studies have considered both, abiotic resources and the presence or the absence of biotic factors likely influence local abundance and habitat specialization in plants. The genus Piper (Piperaceae) is one of Gentry’s hyperdiverse tropical plant taxa. At our study site, the La Selva Biological Station, 50 Piper species are known to co-occur in an 1800 ha forest. Our overall objective was to determine the degree to which the common species of Piper partition the forest along dimensions of abiotic and biotic factors, thus allowing coexistence of so many similar species. We asked the following specific questions: Do abiotic (light and soil) and biotic (herbivore damage, surrounding species) factors affect abundance, distribution and community composition of Piper species in a lowland wet forest? Do abiotic and biotic factors affect the amount of herbivore damage in these species? We sampled Piper plants greater than 1 cm at ground level on two different soil types (alluvial and volcanic) along 26 transects, each 100 m long and 2 m wide. We measured light, herbivore damage, and plant size for all individuals encountered
We encountered 828 individuals of 24 Piper species. Of these, six species were common. Overall community composition was influenced by soil, light, herbivore damage, and the interaction between soil and light. The abundance of all Piper species encountered was mainly positively influenced by the number of Piper species within a plot. Herbivore damage across all species was mainly influenced by soil type and species identity. However, models per species show that the abundance of P. multiplinervium was marginally influenced by the interaction between soil and herbivore damage: when found on alluvial soils, where it is least common, this species suffered more herbivore damage than individuals found on volcanic soils, where it is more common. Damage to P. holdridgeianum was influenced by soil type and light levels. We conclude that there is an important role for both abiotic and biotic factors in determining community composition, distribution, and abundance of these understory habitat specialists. These results have important repercussions for niche differentiation and coexistence in plants. Niche axes along which plants can partition a habitat are not limited to just resource elements, but also potentially include biotic factors such as herbivory.