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Title:Phenotypic patterns of size and shape in North American killifish
Author(s):Welsh, Daniel
Director of Research:Fuller, Rebecca C.
Doctoral Committee Chair(s):Fuller, Rebecca C.
Doctoral Committee Member(s):Cáceres, Carla E.; Paige, Ken N.; Suski, Cory D.
Department / Program:School of Integrative Biology
Discipline:Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):fish
morphology
phenotype
sex
habitat
lake
stream
body size
body shape
fin
Fundulus
topminnow
killifish
Abstract:Variation exists in multiple levels of organization, including between and within species, populations, and individuals. Fish are ideal organisms to explore questions related to the patterns of variation and the potential processes driving patterns. Fish occupy different types of habitats that vary in several important environmental parameters, including water velocity, predatory, prey, and spatial heterogeneity. Body size and shape (and associated characteristics such as fins) are great traits to focus on when exploring how fish may adapt to these different environmental pressures. Size and shape have strong effects on an individual’s maneuverability in many species and, because of this, are believed to be targets for selection. Populations occupying different habitats have shown differences in body size and shape, although species differ in the direction and magnitude of the variation and not all species show a difference between habitat types. The following chapters demonstrate just some of the multitude of complex questions that can be addressed by studying phenotypic differences across habitats in fish. Several such questions that are explored are: To what extent are there consistent differences in body shape and size between lentic and lotic habitats across different fish species? To what extent are there consistent differences in body shape and size between lake and stream habitats between populations within a species? What is the magnitude of variation in traits (fin shape) within a fish species? Is the phenotypic variation in body shape across populations attributable to genetic differentiation, phenotypic plasticity, or both? Here, I examine phenotypic patterns in body size and shape at multiple levels of biological organization- from a family-wide comparison to a with-in species and even within-in a particular trait (the dorsal and anal fins). There are several broad findings. First, there are large differences between males and females in body shape as well as in the shape of anal and dorsal fins, and these patterns appear to be robust to differences in flow regime. Some of these body shape differences may emerge simply due to the necessities of females producing eggs, but other shape differences cannot be attributed solely to these effects. For F. notatus, the unpaired fins (dorsal, anal, and perhaps caudal) differ between the sexes, and, again, the pattern is robust to habitat differences. The fact that dorsal and anal fin shape is tightly correlated along one axis, but that both males and females vary along that axis, suggests the possibility of interesting developmental constraints present. Second, there are differences in body size and shape between lentic and lotic habitats in F. notatus, and these patterns are somewhat generalizable to the entire fundulid family. Fish tend to be larger and deeper bodies with longer dorsal fin bases in lotic habitats than they are in lentic habitats. Finally, our analyses suggest that differences in shape are attributable to both genetics and plasticity as a function of water flow. Academically, this research makes significant contributions to two major areas of research in evolutionary biology. First, because environmental factors (both biotic and abiotic) are what ultimately result in differential survival and/or reproductive success, this research elucidates some potential causes of adaptive evolution in natural populations which is often poorly understood. The only way to fully understand natural selection is through a detailed knowledge of the ecology and biology of organisms. Second, this work helps to clarify the role of the environment in determining body size and shape in fishes. While there has been significant interest in this topic by other researchers, there is seems to be very little consistency in how different environmental factors influence body size and shape. There is a clear need to for additional research in new species in order to develop a more thorough understanding of when a particular factor should be important. In addition to its scholarly value, this work may offer practical, applied knowledge. As climate change progresses, extreme weather events such as spring floods and summer draughts are expected to increase in frequency. Stream fish of all sorts will be faced with the dual problem of countering extreme water flow at some points in time while having to accommodate a lack of water flow at other times. The hope is that this work provides insights as to how fish, in particular killifish (many species of which are widely distributed and abundant in nature, thus making them ecologically important, will deal with these challenges.
Issue Date:2013-08-22
URI:http://hdl.handle.net/2142/45515
Rights Information:Copyright 2013 Daniel Welsh
Date Available in IDEALS:2013-08-22
Date Deposited:2013-08


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