The relative importance of trees versus lianas as hosts for phytophagous beetles (Coleoptera) in tropical forests

Aim Insect assemblages associated with lianas in tropical forests are poorl y studied compared with those associated with trees. The importance of lian as for the maintenance of local species richness of insect herbivores in tr opical forests is therefore poorly understood. With this in mind, a compara tive study of the relative importance of trees and lianas as hosts for phyt ophagous beetles was carried out. Location The study area was located in the canopy of a dry tropical forest in Parque Natural Metropolitano, Panama province, Republic of Panama. Methods A crane system was utilized to access the canopy. The number of spe cies and host specialization of adult phytophagous beetles associated with twenty-six liana species of ten different families, and twenty-four tree sp ecies of twelve different families were compared. Results A total of 2561 host associations of 697 species of beetles were de termined (1339 for trees and 1222 for lianas). On average 55.8 +/- 6.8 beet le species were found to be associated with each tree species while the com parable number for lianas was 47.0 +/- 6.1. The pooled numbers of phytophagous beetle species associated with trees and lianas, respectively, were not significantly different. However, there wer e significantly more species feeding on green plant parts on lianas than on trees, and there were significantly more wood eaters on trees than on lian as. Phytophagous beetles associated with lianas were significantly more special ized than the tree associates due to a higher degree of specialization amon g the species feeding on green plant parts of lianas. Wood eaters and flowe r visitors showed no differences in host specialization on different growth forms. Main conclusion The present study shows that lianas are at least as importa nt as trees for the maintenance of local species diversity of phytophagous beetles at this site. The mechanisms that drive the patterns can only be hy pothesized. Plant architecture, size, and length of growing season are prob ably involved. Further studies, should include measurements of plant traits to elucidate experimentally what mechanisms that drive the patterns. Addit ional insight would come from similar studies in other forest types, and al so studies of other major taxonomic groups of arthropod herbivores.