The ecological cost of sexual reproduction
The ecological cost of sexual reproduction
The aim of this thesis was to investigate ecological conditions under which the genetic variation inherent to sexual reproduction may confer immediate competitive advantages over asexual reproduction. The model species for these tests were the freshwater crustacean Daphnia, with seasonally sexual and obligately parthenogenetic forms, and the littoral enchytraeid worm Lumbricillus lineatus, which has sexual diploid and pseudogamous triploid reproductive systems.
Laboratory experiments with Daphnia pulex during their parthenogenetic phase set genetically varied and genetically uniform populations in competition for an impure food mix, simulating sexual-asexual coexistence. Genetically varied populations had significantly higher birth rates in competition with genetically uniform populations than in competition with themselves. This small competitive release was predicted to be sufficient for immediate coexistence of sexual and asexual populations of Daphnia pulex. Further laboratory experiments instigated invasions by small and large groups of genetically varied Daphnia obtusa into large genetically uniform populations of the same species, and vice versa. Genetically varied invaders of initially large group size increased their representation by more than those of initially small size; in contrast, genetically uniform invaders of large group size diminished on average by more than those of small size, supporting the hypothesis that larger genetically varied groups, with greater genetic variation, had greater competitive advantage than smaller groups with less genetic variation.
The population dynamics of the pseudogamous Lumbricillus lineatus system were investigated by studying life-history characteristics at different starting ratios of triploids to diploids. At lower temperatures and higher food quality, reproductive outputs of triploids and diploids were each inversely proportional to the abundance of the other. This dynamic appeared to favour eventual reversion to diploid-only populations as a result either of diploids out-performing triploids, or of triploids out-performing diploids and crashing in the absence of diploid sperm.
University of Southampton
Tagg, Nikki
6fe9d321-e746-4267-8f40-985d19c2c7a8
2004
Tagg, Nikki
6fe9d321-e746-4267-8f40-985d19c2c7a8
Tagg, Nikki
(2004)
The ecological cost of sexual reproduction.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The aim of this thesis was to investigate ecological conditions under which the genetic variation inherent to sexual reproduction may confer immediate competitive advantages over asexual reproduction. The model species for these tests were the freshwater crustacean Daphnia, with seasonally sexual and obligately parthenogenetic forms, and the littoral enchytraeid worm Lumbricillus lineatus, which has sexual diploid and pseudogamous triploid reproductive systems.
Laboratory experiments with Daphnia pulex during their parthenogenetic phase set genetically varied and genetically uniform populations in competition for an impure food mix, simulating sexual-asexual coexistence. Genetically varied populations had significantly higher birth rates in competition with genetically uniform populations than in competition with themselves. This small competitive release was predicted to be sufficient for immediate coexistence of sexual and asexual populations of Daphnia pulex. Further laboratory experiments instigated invasions by small and large groups of genetically varied Daphnia obtusa into large genetically uniform populations of the same species, and vice versa. Genetically varied invaders of initially large group size increased their representation by more than those of initially small size; in contrast, genetically uniform invaders of large group size diminished on average by more than those of small size, supporting the hypothesis that larger genetically varied groups, with greater genetic variation, had greater competitive advantage than smaller groups with less genetic variation.
The population dynamics of the pseudogamous Lumbricillus lineatus system were investigated by studying life-history characteristics at different starting ratios of triploids to diploids. At lower temperatures and higher food quality, reproductive outputs of triploids and diploids were each inversely proportional to the abundance of the other. This dynamic appeared to favour eventual reversion to diploid-only populations as a result either of diploids out-performing triploids, or of triploids out-performing diploids and crashing in the absence of diploid sperm.
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Published date: 2004
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Local EPrints ID: 465253
URI: http://eprints.soton.ac.uk/id/eprint/465253
PURE UUID: 31af0a20-ceb3-417f-9b71-4f6b515dc170
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Date deposited: 05 Jul 2022 00:32
Last modified: 16 Mar 2024 20:04
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Author:
Nikki Tagg
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