Exploration of temperature and latitude as phenological drivers in Corydalus cornutus (eastern dobsonfly) Restricted; Files Only

Abstract

Understanding the effect of temperature on the larval development and life history of aquatic macroinvertebrates is crucial as climate change permanently alters the freshwater ecosystems of North America. The eastern dobsonfly (Corydalus cornutus) is particularly susceptible by temperature change as shown through its variability in life history across its native range. While previous studies have examined metabolic heat loss in C. cornutus, no study has directly studied the effect of temperature on larval development and emergence phenology. I conducted a laboratory experiment exposing larvae to ambient and elevated temperatures measuring growth rate and development. In addition, I conducted an analysis of publicly available community observations of adult individuals to determine differences in the phenological point estimates of emergence onset, median of onset period, emergence period duration, and emergence offset. I did not observe any growth or larval development in regard to head capsule width and dry weight in the temperature treatment study. My analysis of publicly available community data for phenological point estimates revealed a significant association between latitude and emergence onset date, with higher latitudes being associated with later emergence onset dates. This emphasizes the phenological relevance of climate change for aquatic insect species such as C. cornutus and its importance to aquatic systems as a whole. However, further analyses of specific environmental variables associated with latitude are needed to better understand the environmental triggers of emergence and their relevance to my changing climate.

Table of Contents

Table of Contents

Introduction ............................................................................................................................................. 1

Methodology ............................................................................................................................................ 5

Sampling for Lab Study Individuals....................................................................................................................... 5

Lab Holding Conditions and Routine Maintenance............................................................................................... 6

Temperature Experiment........................................................................................................................................ 7

Dry Weights of Lab Vs. Field Specimens.............................................................................................................. 9

Data Sourcing ........................................................................................................................................................ 9

Calculating Phenological Onset, Duration, Offset and Median observations....................................................... 11

Results ..................................................................................................................................................... 13

Initial Capture Results .......................................................................................................................................... 13

The effect of temperature on larval growth rates and dry weight………………................................................. 13

Community Sourced Data and Phenological Point Estimates……………………………………...................... 15

Discussion ............................................................................................................................................... 17

References .............................................................................................................................................. 23

Appendix I: Supplemental Figures ...................................................................................................... 28

About this Honors Thesis

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School	Emory College
Department	Environmental Studies
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Zoology Environmental Studies
Keyword	Voltinism Megaloptera Eastern Dobsonfly Aquatic Macroinvertebrates Ecology Hellgrammite Temperature Life History Benthic Macroinvertebrates Latitude
Committee Chair / Thesis Advisor	Carolyn Keogh, Emory University
Committee Members	Kelly Murray-Stoker, Emory University Michael Martin, Emory University Julie Clennon, Emory University

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