The Impacts of Salinity Tolerance and Predation on the Allopatric Distribution of Two Species of Palaemonid Slu'imp
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Authors
Darcy, Tara
Issue Date
1996
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Both abiotic and biotic factors are crucial components of a species'
environment. To examine the importance of both forces in determining the
distribution and interactions among closely related species, two experiments were
performed with the congeneric grass shrimp Palaemonetes pugio Holthuis and
Palaemonetes paludosus (Gibbes). In the first experiment, each species was subjected
to 7-day salinity exposures to determine if an overlap existed in their physiological
tolerances to this abiotic factor. Significantly higher survival rates of P. pugio were
found at the highest level of salinity (10.8 parts per thousand, ppt) than at the lowest
level (1.0 ppt), whereas, significantly lower survival rates of P. paludosus were
demonstrated at the highest level (15.0 ppt) versus the two lowest levels (2.4 and 1.0
ppt). A range of salinities (~2.0-6.5 ppt) was found at which we observed high
survival (>65%) for both species, suggesting an overlap of their fundamental niches.
Thus, to take the initial step in determining whether biotic interactions, such as
predation and competition, contribute to the allopatric distribution of the two species,
individuals of each were held together at a tolerable salinity (2.5 ppt) during the
second experiment. A factorial-design was used to determine whether predation by the
large-mouth bass, Micropterus salmoides, would have a significant effect upon the
survival of P. pugio and P. paludosus and whether these effects would differ between
species or in the presence or absence of refuge space. Survival rates for both species
were found to be significantly higher in treatments without a predator than in
treatments where a predator was present. However, survival rates did not significantly
differ between species or between treatments with or without cover. In addition, the
interactions between predator and cover, and predator, cover, and species type did not
significantly affect the survival of P. pugio or P. paludosus. These latter results are
undoubtedly related to the high variability and low number of replicates utilized during
the experiment. However, with repeated experiments and further studies into the
ecology and interactions of P. pugio and P. paludosus, competition between the two
could be examined, perhaps offering an explanation of why they have remained
allopatrically distributed in nature. The results of both experiments serve to illustrate
the potential importance of both abiotic and biotic factors to species distribution in
nature.
With honors.
With honors.
Description
vi, 39 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.