Master's Theses

Date of Award

2017

Document Type

Thesis

Department

Biology

First Advisor

Amy Berkov

Second Advisor

David Lohman

Third Advisor

Michael Hickerson

Keywords

Wood-borer, bark beetles, Eschweilera biflava, lowland moist forest, mycetophagous, xylomycetophagous

Abstract

Abstract Primary saproxylic beetles play a major role in forest nutrient cycling and making deadwood accessible to other decomposers. Understanding beetle host preferences and patterns of community assembly is critical for their conservation, and for predicting which species might become invasive. This project aims to investigate the ecological and host specificity, as well as the community composition of curculionids in a mosaic of old-growth (OG) and secondary forest on the Osa Peninsula, Costa Rica. The subfamily Scolytinae was expected to be the most species-rich and abundant. Ambrosia beetles were expected to have more generalist species than other curculionids. Old growth forest was expected to yield more diversity and specialized curculionids, showing greater stratification. Lecythidaceae (the Brazil nut family) was hypothesized to yield the highest abundance and number of host specialist species. Forest stage was expected to be the strongest factor in determining overall community composition.

Forty-one trees (six plant families), were sampled. Branches were cut during the transition from dry to rainy season (2013) and exposed to beetles at canopy and ground strata. The branches yielded 8,761 individuals, from 91 species in eight curculionid subfamilies. Scolytinae had the highest species richness (N = 33) and abundance. Fourteen weevils were host specialists. Nine ambrosia beetles were host specialists, associated with either Lecythidaceae or Fabaceae (legume family). Secondary forest yielded the highest number of forest stage specialist species (N = 18). Ground stratum in secondary forest had the highest species diversity, while OG canopy yielded the highest relative abundance. The Brazil nut family yielded almost half of all curculionids (4,356 individuals in 51 species). Host plant species was the main deterministic factor for the community structure. Therefore, saproxylic curculionids are extremely vulnerable to forest disturbance and could be at risk in the face of climate change.