Dissertations and Theses

Date of Award

2021

Document Type

Thesis

Department

Biology

First Advisor

Amy Berkov

Second Advisor

David Lohman

Third Advisor

Ana Carnaval

Keywords

Cerambycinae, digital image analysis, Lagocheirus, Lamiinae, macrophysiology, Mionochroma, thermoregulation

Abstract

Increasing global temperatures have been linked to shifts in the distributions and preferred microhabitats of terrestrial species. This trend is predicted to impact tropical forest insects, which may already be exposed to conditions that bring them close to their thermal maxima. Tropical microhabitats are linked to vertical stratification, because the canopy is hotter, winder, and less humid than the ground. In ectothermic organisms, such as beetles, thermoregulation is dependent on morphological and behavioral traits. This study investigates woodboring cerambycid beetles, to determine how behavioral thermoregulation through microhabitat selection (vertical stratification) is correlated to morphological attributes (color lightness, size, and pubescence) and thermal responses (heating rates and maximum temperature). Preserved specimens from Central and South America, representing species with stratum preferences, were heated in a laboratory setting. Color lightness had a significant impact on heating rates: in accordance with the thermal melanism hypothesis, darker specimens heated up more rapidly than lighter ones. Smaller specimens, and specimens with appressed pubescence, reached lower maximum temperatures. These latter results were contrary to expectations based on surface area to volume ratios. Thermal responses involved more complicated relationships with morphological attributes than predicted. Morphological attributes and thermal responses did not differ significantly between strata due to the high levels of variability observed, and small sample size. Further study of the interactions between the factors affecting heating rates of cerambycids, their thermal tolerances, and the abiotic components of their selected microhabitats will be essential to understand the potential impact of climate change.

Available for download on Sunday, July 02, 2023

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