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Plant-Herbivore Interactions and Evolutionary Potential of Natural Arabidopsis lyrata Populations
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, I combined field, greenhouse and common-garden experiments to examine the ecological and evolutionary consequences of plant-herbivore interactions and the genetic architecture of fitness-related traits in the insect-pollinated, self-incompatible, perennial herb Arabidopsis lyrata. More specifically, I examined (1) whether damage to leaves and inflorescences affects plant fitness non-additively, (2) whether trichome production is associated with a cost in terms of reduced tolerance to leaf and inflorescence damage, (3) whether young plant resistance to a specialist insect herbivore varies among populations, and (4) whether the evolution of flowering time, floral display and rosette size is constrained by lack of genetic variation or by genetic correlations among traits.

A two-year field experiment in a Swedish population showed that damage to rosette leaves and to inflorescences can affect both current and future plant performance of A. lyrata, and that effects on some fitness components are non-additive. A two-year field experiment in another Swedish population indicated that trichome-producing plants are not less tolerant than glabrous plants to leaf and inflorescence damage. In a greenhouse experiment, acceptability of young plants (5-6 weeks old) to ovipositing females and damage received by Plutella xylostella larvae varied considerably among twelve A. lyrata populations. Both oviposition and leaf damage were positively correlated with rosette size, but trichome density in the trichome-producing morph was apparently too low at this developmental stage to influence resistance to P. xylostella. In a common-garden experiment, flowering time, floral display and rosette size varied among four Scandinavian A. lyrata populations, and displayed significant additive genetic variation in some populations. Yet, strong genetic correlations between flowering start and number of flowers, and between petal length and petal width suggest that these traits may not evolve independently.

Taken together, the results indicate the need to consider possible long-term and non-additive effects of herbivore damage to different plant parts, that there is no trade-off between trichome production and tolerance to herbivory, that the importance of morphological defenses against herbivory may change through plant ontogeny, and that considerable genetic variation for traits such as flowering time and floral display can be maintained in natural plant populations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 47 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 996
Keyword [en]
plant defenses, leaf herbivory, floral herbivory, ontogeny, G-matrix, trade-offs
National Category
Ecology Evolutionary Biology
Research subject
Biology with specialization in Ecological Botany; Biology with specialization in Evolutionary Genetics
Identifiers
URN: urn:nbn:se:uu:diva-183433ISBN: 978-91-554-8535-1 (print)OAI: oai:DiVA.org:uu-183433DiVA: diva2:564534
Public defence
2012-12-15, Lindahlsalen, Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-11-23 Created: 2012-10-25 Last updated: 2013-02-11Bibliographically approved
List of papers
1. Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata
Open this publication in new window or tab >>Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata
2012 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 169, no 4, 1033-1042 p.Article in journal (Refereed) Published
Abstract [en]

Herbivores may damage both leaves and reproductive structures, and although such combined damage may affect plant fitness non-additively, this has received little attention. We conducted a 2-year field experiment with a factorial design to examine the effects of simulated leaf (0,12.5, 25, or 50% of leaf area removed) and inflorescence damage (0 vs. 50% of inflorescences removed) on survival, growth and reproduction in the perennial herb Arabidopsis lyrata. Leaf and inflorescence damage negatively and independently reduced flower, fruit and seed production in the year of damage; leaf damage also reduced rosette size by the end of the first season and flower production in the second year. Leaf damage alone reduced the proportion of flowers forming a fruit and fruit production per plant the second year, but when combined with inflorescence damage no such effect was observed (significant leaf × inflorescence damage interaction). Damage to leaves (sources) caused a greater reduction in future reproduction than did simultaneous damage to leaves and inflorescences (sinks). This demonstrates that a full understanding of the effects of herbivore damage on plant fitness requires that consequences of damage to vegetative and reproductive structures are evaluated over more than 1 year and that non-additive effects are considered.

Keyword
leaf herbivory, floral herbivory, artificial damage, plant fitness, interactions
National Category
Ecology
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-183432 (URN)10.1007/s00442-012-2276-1 (DOI)000306494800017 ()22349755 (PubMedID)
Available from: 2012-11-01 Created: 2012-10-25 Last updated: 2017-12-07Bibliographically approved
2. Trichome production does not influence tolerance to simulated leaf and inflorescence damage in the perennial herb Arabidopsis lyrata
Open this publication in new window or tab >>Trichome production does not influence tolerance to simulated leaf and inflorescence damage in the perennial herb Arabidopsis lyrata
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The evolution of plant defenses against herbivory depends on the costs and benefits of traits that deter herbivores (resistance) and traits that maintain fitness after damage (tolerance). In Arabidopsis lyrata, the production of trichomes is associated with a fitness cost in the absence of herbivores. We conducted a field experiment over two years to examine whether trichome production is also associated with reduced tolerance to simulated leaf (0 and 50% of leaf area removed) and inflorescence damage (0 and 50% of inflorescences removed). Trichome-producing plants were not less tolerant than glabrous plants to simulated herbivore damage (no significant morph × leaf or inflorescence damage interaction). Inflorescence and leaf damage had independent negative effects on the reproductive output and growth of damaged plants. Leaf damage reduced rosette size the year of damage, but effects on reproductive output in the year of damage, and on survival and reproductive performance the following year were weak and not statistically significant. Inflorescence damage significantly reduced the number of flowers, fruits and seeds the year of damage, but did not affect plant size, flower or fruit production the year after damage. The effect on seed production was proportional to the damage inflicted, but, because inflorescence damage stimulated the production of new inflorescences, the numbers of flowers and fruits decreased by less than 50%. Thus, irrespective of morph, the study population was more tolerant to leaf than to inflorescence damage. The results suggest that trichome production and tolerance to herbivore damage can evolve independently in A. lyrata.

Keyword
trade-offs, plant defenses, fitness costs, defoliation, florivory, herbivores
National Category
Ecology
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-183428 (URN)
Available from: 2012-11-01 Created: 2012-10-25 Last updated: 2013-02-11
3. Trichome production and variation in young plant resistance to the specialist insect herbivore Plutella xylostella among natural populations of Arabidopsis lyrata
Open this publication in new window or tab >>Trichome production and variation in young plant resistance to the specialist insect herbivore Plutella xylostella among natural populations of Arabidopsis lyrata
2013 (English)In: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 149, no 2, 166-176 p.Article in journal (Refereed) Published
Abstract [en]

The strength of plant-herbivore interactions varies spatially and through plant ontogeny, which may result in variable selection on plant defenses against herbivory both among populations and among different life-history stages. The perennial herb Arabidopsis lyrata occurs in a trichome-producing and a glabrous morph, and previous work has shown that glabrous plants tend to receive more damage than trichome-producing plants. In this study, we quantified oviposition preference and larval feeding by P. xylostella on very young A. lyrata (5-6 weeks old), originating from twelve natural populations, six from Sweden and six from Norway. Six of the populations (three from each region) were polymorphic for trichome production and allowed a comparison of resistance against P. xylostella between the glabrous and the trichome-producing morph at a stage when trichome density is low in trichome-producing plants. There was considerable variation among populations in the number of eggs received and the proportion of leaf area consumed, but not between regions (Sweden and Norway) or trichome morphs. Rosette size explained a significant portion of the variation in oviposition and larval feeding. The results demonstrate that among-population variation in resistance to insect herbivory can also be detected among very young individuals of the perennial herb A. lyrata. They further suggest that trichome densities are too low at this developmental stage to contribute to resistance, and that the observed among-population variation in resistance is related to differences in other plant traits.

Keyword
oviposition, larval feeding, ontogeny, plant defense, trichome density
National Category
Ecology
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-183429 (URN)10.1111/eea.12120 (DOI)000325356200008 ()
Available from: 2012-11-01 Created: 2012-10-25 Last updated: 2017-12-07Bibliographically approved
4. Genetic variation and covariation in flowering time, floral display and rosette size in four Scandinavian Arabidopsis lyrata populations
Open this publication in new window or tab >>Genetic variation and covariation in flowering time, floral display and rosette size in four Scandinavian Arabidopsis lyrata populations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Levels of additive genetic variation and patterns of genetic correlations among traits influence evolutionary trajectories of traits in natural populations and among-population differentiation. With a nested paternal half-sib crossing design we examined the genetic architecture of flowering time, floral display and rosette size in four Scandinavian populations of the perennial herb Arabidopsis lyrata grown in a common-garden experiment in the Swedish native range. We specifically asked whether these traits vary genetically among populations, whether response to selection is constrained by lack of genetic variation or by genetic covariances among traits, and whether there is evidence of a trade-off between allocation to reproduction and vegetative growth, or between the number and size of flowers produced. The characters examined varied genetically among populations and displayed significant additive genetic variation in some populations. A strong negative genetic correlation between flowering start and number of flowers, and a strong positive correlation between petal length and width indicated that these pairs of traits do not evolve independently in some populations. G-matrices varied among populations suggesting that genetic (co)variances have evolved locally. There was no evidence of a trade-off between allocation to reproduction and vegetative growth or between the number and size of flowers, indicating that variation in resource acquisition was larger than variation in relative allocation to these different functions. 

Keyword
G-matrix, genetic correlations, evolutionary potential, life-history tradeoffs, floral traits
National Category
Ecology Evolutionary Biology
Research subject
Biology with specialization in Evolutionary Genetics; Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-183430 (URN)
Available from: 2012-11-01 Created: 2012-10-25 Last updated: 2013-02-11

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