The hybridizing Daphnia mendotae and D. dentifera (Crustacea: Cladocera) are sympatric
throughout much of North America, and are considered a cryptic species complex due to their lack of
phylogenetically informative morphological characters. They appear to have no biological mating
barriers: hybrids may dominate or coexist with either or both parental species, and are sexually
competent, forming both F2 hybrids and back-crosses. Nevertheless, the two species remain distinct.
There is observational evidence that separation may be enforced by adaptation to different predation
regimes: D. mendotae, with its greater anti-predator morphological plasticity, may out-compete D.
dentifera under intense invertebrate predation, while the smaller D. dentifera may be better adapted to
avoid predation by visually feeding fish. We tested this idea by examining whether D. mendotae and D.
dentifera differ in ecologically relevant life history and morphological traits. We performed a replicated
life history experiment involving 6 replicates of 6 clones within each species, and measured time until
first reproduction, fecundity, and juvenile and population growth rates. In parallel, we examined
whether these species differed in morphological traits predicted to arise from adaptation to different
predator types, and tested the ecological relevance of these traits by exposing Daphnia to predation by
the invasive cladoceran Bythotrephes longimanus. Finally, we examined the plasticity of life history,
morphology, and susceptibility to predation by rearing Daphnia under exposure to Bythotrephes
chemical cues for two generations. D. mendotae and D. dentifera differed across almost all measured
life history and morphological traits in directions that accord with our hypotheses, strongly suggesting
that their species boundaries are maintained by adaptation to different predation regimes. Plastic
reaction to Bythotrephes, however, was weak and inconsistent, suggesting that these species either do
not detect or respond to this recent invader, or that their responses are manifested in other ways. / Thesis (Master, Biology) -- Queen's University, 2011-12-23 20:31:14.76
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/6936 |
| Date | 04 January 2012 |
| Creators | TURKO, PATRICK |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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