Phenological trade-offs under biotic and abiotic selection in introduced populations of Lythrum salicaria
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Authors
Akbar, Mia
Date
2024-07-31
Type
thesis
Language
eng
Keyword
Ecology , Evolution , Flowering phenology
Alternative Title
Abstract
Evolutionary constraints imposed by a life history trade-off between age and size at maturity are common to a wide range of taxa. However, studies measuring phenotypic selection in natural populations often observe directional selection for both early reproduction and large size rather than predicted stabilizing selection around a local optimum. A further theoretical contradiction appears when this directional selection is accompanied by a missing evolutionary response. For example, directional selection for early flowering in plants is contrasted by variable phenological responses to climate change that do not demonstrate a unilateral shift to earlier flowering time. Focusing on North American populations of the wetland plant Lythrum salicaria, I used common garden experiments to investigate why variation for flowering time and size persists in the presence of strong genetic correlations. The first field experiment characterized full flowering schedules of 369 individuals representing 13 populations and revealed heritable genetic changes in phenology. Aspects of flowering schedule shape that are potentially adaptive such as mean, skew and kurtosis may weaken the trade-off between flowering time and size. The second field experiment measured six years of growth and reproduction in 221 seed families representing 20 populations in the presence and absence of insect herbivory. We found that insect herbivory results in plants that flower at a later time and smaller size than their predicted source population optimum. We also learned that patchy and variable selection from herbivores across years alters the strength of natural selection on flowering time and size, resulting in persistent phenotypic variation in both traits. Together, these results provide evidence that rapid phenological evolution can emerge along environmental gradients but is limited when strong biotic interactions reduce the efficiency of natural selection.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
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.
Attribution 4.0 International