Behavioral Temperature Preference and Physiological Critical Thermal Limits of the Non-Native Indo-Pacific Sergeant Abudefduf Vaigiensis, Endemic Hawaiian Sergeant Abudefduf Abdominalis, and Hybrids from Oʻahu, Hawaiʻi
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Authors
Elena Maria Polizotto
Issue Date
2025
Type
Thesis
Language
Keywords
Marine Science
Alternative Title
Abstract
Sea surface temperatures have been increasing globally as has the frequency of marine heat waves due to climate change. In the Hawaiian Archipelago, sea surface temperatures have been increasing since the 1940s. Tropical marine ectotherms often have a core temperature close to their environmental temperatures and settle in environments near their upper thermal range. Increased sea surface temperature has been shown to threaten coral reef fishes when surpassing their thermal tolerances. I chose to investigate the sergeant major species group (Abudefduf abdominalis, A. vaigiensis, and hybrids) which are an abundant coral reef fish in the Hawaiian Islands. The endemic Hawaiian sergeant, A. abdominalis, and the invasive Indo-Pacific sergeant, A. vaigiensis, first reported in the islands in the 1990s, were formally documented hybridizing in 2007, although hybridization likely occurred before. I assessed differences in thermal biology in relation to genetic similarity to the pure, parental species (A. abdominalis and A. vaigiensis) by using Structure 𝑄𝐴𝑣𝑎 as an estimate of the proportion of the genome in each individual that came from A. vaigiensis versus A. abdominalis. I performed temperature preference (Tpref) experiments, which assessed an individual’s behavioral choice for certain temperatures, in an annular chamber on forty sergeant majors. Additionally, I performed critical thermal maximum (CTmax) experiments, which assess an individual's physiological thermal limit, on thirty-six sergeant majors. There was no effect of genetic similarity to A. vaigiensis on CTmax, but mass had an effect of a 1.4°C decrease on CTmax as mass increased from 8.7 to 124.6 g. Additionally, there was an effect of 1.7°C increase in the size of the thermal preference range, interquartile range (IQR), over the mass range in this study (8.7 to 124.6 g = 116 g). I found genetic similarity to A. vaigiensis to have significant effect of 1.2°C increase in median Tpref, a 2.2 °C increase in lower avoidance temperature (the first quartile), and a 1.5°C decrease in the size of the IQR; moreover, 2 both A. vaigiensis and hybrids showed a preference for temperatures from 26 - 28°C. By using Structure 𝑄𝐴𝑣𝑎 as an estimate of the proportion of the genome in each individual that came from A. vaigiensis versus A. abdominalis, I found genetic similarity to A. vaigiensis lead to higher median Tprefs, higher lower avoidance temperatures, and decreased size of the thermal preference ranges, though there was no effect on CTmax. Although I could not directly compare across species groups, testing for differences in thermal biology in relation to genetic similarity to the pure, parental species suggest that the invasive A. vaigiensis have a preference for warmer temperatures than the native A. abdominalis, which may have aided A. vaigiensis’ expansion into Hawaiian habitats with increasing SST.
Description
Citation
Publisher
Hawaii Pacific University