Term of Award
Master of Science in Biology
Document Type and Release Option
Thesis (restricted to Georgia Southern)
Michael P. Moulton
Committee Member 1
J. B. Claiborne
Committee Member 2
John W. Parrish
Several morphological analyses have been conducted on the introduced passerines of the Hawaiian islands that have implicated interspecific competition as having played a role in the assembly of that community. In this thesis, I extended these morphological analyses to another tropical island, Tahiti. I chose to center my analyses to the search for one particular morphological pattern, overdispersion. Morphological overdispersion here means that the set of surviving species in a community are more different from one another than what would be expected by chance alone.
There have been at least 41 passerine species introduced to Tahiti and of those only seven still exist in the community. Using multiversity statistics and Monte Carlo simulations, these seven species were shown to be morphologically overdispersed. This result is consistent with the hypothesis that interspecific competition played a role in the assembly of this community.
Although these analyses are a unique and revealing way to observe corranunities through an extended length of time, they are not without their potential problems. The second part of this thesis is focused around three potential biases outlined by Colwell and Winkler (1984). In particular, I illustrate the Narcissus effect among the introduced finches of Oahu, Hawaii.
At least 25 species of finches have been introduced to Oahu and of these 15 are currently surviving. When the dispersion of these 15 are compared to a series of random communities they appear morphologically overdispersed. Of these 15 surviving species, seven are found in sugarcane field habitat. When these seven are compared to all 25 species introduced to Oahu, they too appear morphologically overdispersed. According to Colwell and Winkler this is the appropriate pool of species for comparison.
When these seven species present in sugarcane are compared only the 15 surviving species, though, they do not appear morphologically overdispersed. Unfortunately, this is the pool of comparison that most morphological analyses on natural communities are forced to use. The discrepancy in the results among the introduced finches of Oahu is apparently due to a Narcissus effect.
Lockwood, Julie L., "Morphology, Competition, and the Structure of Some Introduced Passerine Communities" (1991). Legacy ETDs. 666.