Masters Theses

Date of Award

8-2013

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

Christopher D. Hulsey

Committee Members

Alison Boyer, James Fordyce

Abstract

Pelagic larval duration (PLD) likely influences evolutionary processes including dispersal, genetic connectivity, and extinction in aquatic organisms. PLD has been well studied in marine systems, but very few freshwater species have been studied. Darters are a diverse group of freshwater North American fish with available information on the length of this stage from propagation efforts. There is surprising variation in the length of this stage ranging from 0 to 60 days. By compiling information from Conservations Fisheries, Inc. (Knoxville, TN) and the literature, we were able to make comparisons between the PLD of 23 species and other life history characteristics. We hypothesized that 1) PLD will influence developmental characteristics and reflect tradeoffs at these critical stages 2) a higher extinction risk should associate with lower PLD. Size at yolk absorption was found to have a marginally significant, relationship with PLD, but juvenile size and maximum size were found to have positive relationships. These relationships indicate a possible developmental tradeoff between larval survival and potential size and that pelagic larval duration in darters is greatly influenced by life history characteristics. Additionally, through a phylogenetic comparative analysis, we found lower PLD in darter lineages was evolutionarily associated with extinction risk, which is similar to patterns commonly recovered from the marine fossil record. These findings provide some of the first support in extant taxa for the hypothesis that PLD is an important determinant of extinction. This study indicates that PLD is highly influential in species life history characteristics and predictions of species’ persistence.

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