Species diversity estimation of ambrosia and bark beetles in temperate mixed forests in Japan based on host phylogeny and specificity

Understandings of the effect of host plant phylogeny on the structure of herbivore assemblage is useful for estimating global species richness of herbivores. Here we test the relationship between host plant phylogeny and two assemblages including ambrosia beetle assemblage that have been considered to be the lowest host specificity among plant-dependent guilds. These results of local scale were used for estimating regional species richness by extrapolating to the number of plant order and species in Japan. The estimated numbers were compared with the numbers of described species in Japan. Tree trunks of 17 plant species representing 17 orders of all major lineages of Japanese tree flora were exposed for collecting wood boring beetle species. A total of 12 ambrosia and four bark beetle species were collected. Similarity of both ambrosia and bark beetle assemblages showed a significant negative trend with phylogenetic distance between focal host plant species. The regression model for this relationship was well fit by a linear model whereas previous studies used a semi-log model, which suggests a difference in mechanism of host utilization with host taxonomic levels. Our results showed a broader host range of ambrosia beetle assemblage in temperate forest than to a comparable study in tropical rainforests. Species richness estimated is lower than the described species in Japan, suggesting the need for more samples along the altitudinal gradients for accurate estimation for the Japanese fauna.