An Experimental Study of Vertical Habitat Use and Habitat Shifts in ...

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Chapter 1: Literature Review Literature Review Extensive literature searches were performed on such topics as niche theory, speciation, competitive exclusion (and other outcomes of nonnative species introductions), characteristics of host watersheds susceptible to invasion, common characteristics of invasive fish species, the risks of hybridization with native species, and behavioral habitat segregation. To understand the competitive relationships between closely related species and the harmful possibilities of mixing similar vicariant species, one must first begin to understand the tenets of niche theory and competitive exclusion. Uninterrupted biological succession among similar species over time is necessary for increasingly close-knit associations and reciprocal adaptations (Odum 1969). Long periods of uninterrupted interactions between biotic communities allow the possibility of coexistence and an increase in the degree of species specialization (MacArthur and Levins 1967, Odum 1969). This is especially true when considering areas possessing migration barriers (Pianka 1966). Migratory pathways would be eliminated, disallowing the onslaught of congeners or similar species that could compete with species typifying the current assemblage. Thus, symbiotically coevolved species assemblages are often formed within areas in which natural isolating barriers occur (Pianka 1966). This assumes that factors allowing divergence and co-evolution, such as time and ecological stability, are present and substantial enough to create ecologically stable communities (Pianka 1966, Odum 1969, Schoener et al. 1979). The net result of uninterrupted succession over time is stability; however, perturbations of the community’s interspecific framework and anthropogenic stresses can deteriorate this stability (Odom 1969). 1
In order for similar species to avoid competitive exclusion they must be capable of partitioning some aspect of the trophic, spatial, or temporal variables of habitat usage (MacArthur and Levins 1964, Pianka 1974). Effects of competition, such as decreased survivorship and fecundity, are reduced through natural selection in lieu of more favorable traits (Murray 1986). Differentiation of breeding strategies, behavior, susceptibility to biochemical hazards, or resistance to the effects of environmental stochasticity is needed for interspecific traits to remain distinct (Harper et al. 1961). Such evolutionary specializations are more pronounced in complex, heterogeneous environments (Murray 1986). Increased niche dimensionality allows greater ecological packing, thus allowing an environment to accommodate a greater number of species (MacArthur and Levins 1967). Similarly, it is believed that the number of related species coexisting in a given ecosystem is strongly dependent on the width and overlap of those species’ niches (Pielou 1972). Complete, non-interbreeding competitors cannot coexist without evolutionary divergence, readjusted niche widths, or competitive elimination of one of the species (Hardin 1960, Pianka 1966, Pianka 1974). Problems occur when ecological processes set into place through disturbances disrupt stable evolutionary processes (Pianka 1966). The introduction of a non-indigenous species that acquires already utilized niche space in a new region would be an example of such a disturbance. The chance exists for competitive exclusion to occur if two similar, geographically separated species are mixed (Hardin 1960). To make matters worse, established introduced species often utilize a realized niche that more closely resembles its fundamental niche in the host community (Li and Moyle 1981). Thus, species 2
Page 1 and 2: An Experimental Study of Vertical H
Page 3 and 4: Acknowledgements I would like to th
Page 5: LIST OF TABLES Table 1. Results of
Page 9 and 10: species diversity should increase (
Page 11 and 12: noting that the abundance of some s
Page 13 and 14: exhibited by species involved; the
Page 15 and 16: new environment (Dueser and Porter
Page 17 and 18: host environment, proposing that a
Page 19 and 20: Hybridization with introduced speci
Page 21 and 22: alteration may reduce the habitat s
Page 23 and 24: in the upper Greenbrier River and o
Page 25 and 26: ubiquitous, appearing in all channe
Page 27 and 28: Literature Cited Addair, J. 1944. T
Page 29 and 30: Gibbs, R. H. 1957. Cyprinid fishes
Page 31 and 32: Lobb, M. D., III. 1986. Habitat use
Page 33 and 34: Paybins, K. S., T. Messinger, J. H.
Page 35 and 36: Chapter 2: An Experimental Study of
Page 37 and 38: Introduction Non-native fishes nega
Page 39 and 40: native cyprinids on their native co
Page 41 and 42: enthic, near-benthic, lower-pelagic
Page 43 and 44: N. telescopus had modes in the lowe
Page 45 and 46: native species pairs were partially
Page 47 and 48: interspecific separation of vertica
Page 49 and 50: MacArthur, R. and R. Levins. 1967.
Page 51 and 52: Table 1. Results of Chi square Test
Page 53 and 54: Total Number of Occurrences 160 140
Page 55: Total Number of Occurrences 160 140

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