Studying patterns of species distribution across spatial gradients provides important insight into the functional mechanisms that drive and impact organismal diversity. The scope of ecological research on diversity across elevational gradients is wide, but current empirical data presents several competing hypotheses. Furthermore, a gap in scientific knowledge exists on how bark beetles disperse across these gradients, particularly in tropical environments. In this project, we sought to determine the distribution of bark beetles—the phloem, ambrosia, and seed feeding beetles of the weevil subfamily Scolytinae—along a tropical elevational gradient and assess areas of highest and lowest species richness, abundance, and diversity. A selection of nine different elevation bands was made along a mountain range in Madang, Papua New Guinea, to serve as our gradient. Our findings indicate that species richness of bark beetles appears to follow a unimodal curve that peaks at a lowland elevation of 700m and decreases towards higher elevations. Abundance, in contrast, peaks at both 200m and 1700m, with a dip in specimens at 700m. Distributions of two hyper-diverse genera—Coccotrypes and Cryphalus—follow unique patterns within the overall diversity gradient and dictate the curves of our abundance data. These results support the findings of previous studies that conclude higher diversity estimates at lower elevations and contribute additional data on the elevational spread of specific bark beetles in tropical environments.
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