Natural forest dynamics is a foundational topic of forest science. A new Wood Pasture hypothesis considering large herbivore as driving force in forest ecosystem is now challenging the traditional High Forest hypothesis, in which vegetation is regarded as main driving force. In this study, a model-based approach is applied to investigate differences between these two hypotheses and the determine factors in the system. A theoretical landscape of 1 km²formed by 100*100 cells is set up with 100 vegetation patches and free moving herbivores on. Our null hypothesis that herbivores make no difference in vegetation dynamics especially at canopy level is rejected. It is found that synchronization of herbivore behaviors is the most influencing factor of how a landscape might be shaped. It is also found that landscape could be a mosaic of both high forest and wood pasture depends on large herbivore’s herd size.

Lipoxygenase (LOX)-derived oxylipins are known to play critical roles in defense against herbivores and pathogens. The objective of this study was to determine the biochemical, molecular and physiological roles of a specific maize lipoxygenase gene, ZmLOX10, with special emphasis on LOX10-derived oxylipins in plant-insect and plant-pathogen interactions. To achieve this goal, independent mutant alleles were generated and genetically advanced to create near-isogenic mutant and wild-type lines suitable for functional analysis. Here we provide genetic evidence that LOX10 is the sole LOX isoform in maize required for the biosynthesis of green leafy volatiles (GLV) in leaves and show that LOX10- mediated GLVs play a significant role in direct and indirect defense responses to insects through their regulation of jasmonic acid and volatile organic compound production. Contrary to the defensive role of LOX10 in plant-insect interactions, tests for susceptibility to fungal pathogens suggest that LOX10-mediated GLVs may contribute to the development of disease symptoms to the economically important maize pathogens, Aspergillus flavus and Colletotrichum graminicola. Specifically, LOX10-derived GLVs may facilitate aflatoxin accumulation in response to A. flavus infection and may play a positive role in anthracnose leaf blight and stalk rot caused by C. graminicola. Collectively, our results suggest that metabolites derived from GLV-regulated pathways have a significant impact on molecular plant-herbivore and plant-pathogen interactions.

Plant-herbivore interactions are among the most common of ecological interactions. It is therefore not surprising that plants have evolved multiple mechanisms to defend themselves, using both constitutive chemical and physical barriers and by induced responses which are only expressed after herbivory has occurred. Herbivores, on the other hand, respond to these plant defenses by evolving counter-adaptations which makes defenses less effective or even useless. Adaptation can occur at different geographical scales, with varying coevolutionary interactions across a spatially heterogenous landscape. By looking at the underlying genes responsible for these defensive traits and herbivore related phenotypic traits, it is possible to investigate the coevolutionary history of these plant- herbivore interactions. Here I use molecular population genetic tools to investigate the evolutionary history of several inducible defense genes in European Aspen (Populus tremula) in Sweden. Two genes, belonging to the Polyphenol oxidase gene-family (PPO1 and PPO2), show skews in their site frequency spectrum together with patterns of diversity and divergence from an outgroup which correspond to signatures of adaptive evolution (Paper II). 71 single nucleotide polymorphisms (SNPs) from seven inducible defense genes (PPO1-PPO3, TI2-TI5) show elevated levels of population differentiation compared to control genes (genes not involved in plant defense), and 10 of these defense SNPs show strong signatures of natural selection (Paper III). These 71 defense SNPs also divides a sample of Swedish P. tremula trees into three distinct geographical groups, corresponding to a Southern, Central and Northern cluster, a patterns that is not present in control SNPs (Paper III). The same geographical pattern, with a distinct Northern cluster, is also observed in several phenotypic traits related to herbivory in our common garden in Sävar (Paper IV). These phenotypic traits show patterns of apparent local maladaptation of the herbivore community to the host population which could indicate the presence of “information coevolution” between plants and herbivores (Paper IV). 15 unique defense SNPs also show significant associations to eight phenotypic traits but the causal effects of these SNP associations may be confounded by the geographic structure found in both the underlying genes and in the phenotypic traits. The co-occurrence of population structure in both defense genes and herbivore community traits may be the result from historical events during the post-glacial recolonization of Sweden. / Interaktioner mellan växter och herbivorer är bland de vanligaste ekologiska interaktionerna och det är därför inte förvånande att växter har utvecklat flera olika mekanismer för att försvara sig. Dessa försvarsmekanismer består både av konstitutiva kemiska och fysiska barriärer så väl som inducerade försvar som bara är uttryckta efter att en växt har blivit skadad genom betning. Herbivorerna å sin sida svarar på dessa försvar genom att utveckla motanpassningar som gör växternas försvar mindre effektiva eller till och med verkningslösa. Dessa anpassningar kan ske över olika geografiska skalor beroende på om de samevolutionära interaktionerna varierar i ett rumsligt heterogent landskap. Genom att studera de underliggande gener som kontrollerar dessa försvarsegenskaper tillsammans med herbivorrelaterade fenotypiska egenskaper är det möjligt att undersöka den samevolutionära historien av interaktionerna mellan växter och herbivorer. Här använder jag mig av molekylärpopulationsgenetiska verktyg för att undersöka den evolutionära historien i flera inducerade försvarsgener hos asp (Populus tremula) i Sverige. Två gener, som tillhör genfamiljen Polyphenol-oxidaser (PPO1 och PPO2), uppvisar ett frekvensmönster som man förväntar sig vid positiv selektion. Detta mönster kan också ses i dessa geners diversitet samt i divergens från en utgrupp (Uppsats II). 71 ”single nucleotide polymorphisms” (SNPar) från 7 inducerade försvarsgener (PPO1-PPO3, TI2-TI5) visar förhöjda nivåer av populationsdifferentiering jämfört med kontrollgener (gener som inte är involverade i trädens försvar), och 10 av dessa försvars-SNPar visar även tecken på naturlig selektion (Uppsats III). Dessa 71 försvars-SNPar delar in ett urval av svenska aspar i tre distinkta geografiska grupper som beskriver ett sydligt, centralt och nordligt kluster som inte förekommer hos kontroll-SNPar (Uppsats III). Samma geografiska mönster, med ett distinkt nordligt kluster, återfinns däremot i ett antal fenotypiska egenskaper som är relaterade till herbivori i ett odlingsförsök utanför Sävar (Uppsats IV). Dessa fenotypiska egenskaper visar tecken på lokal felanpassning hos herbivorsamhället till den lokala värdpopulationen, vilket kan indikera förekomsten av ett ”samevolutionärt informationsutbyte” mellan växter och herbivorer (Uppsats IV). 15 unika försvars-SNPar påvisar också signifikanta associationer med 8 olika fenotypiska egenskaper, men om dessa har en verklig effekt eller inte är svårt att säga på grund av den geografiska strukturen som förekommer både hos de underliggande generna och hos de fenotypiska egenskaperna. Att denna populationsstruktur förekommer hos både försvarsgener och egenskaper som är förknippade med herbivorsamhället kan däremot vara ett resultat av historiska händelser som skett under aspens post-glaciala återkolonisation av Sverige.

abstract: An understanding of diet habits is crucial in implementing proper management strategies for wildlife. Diet analysis, however, remains a challenge for ruminant species. Microhistological analysis, the method most often employed in herbivore diet studies, is tedious and time consuming. In addition, it requires considerable training and an extensive reference plant collection. The development of DNA barcoding (species identification using a standardized DNA sequence) and the availability of recent DNA sequencing techniques offer new possibilities in diet analysis for ungulates. Using fecal material collected from controlled feeding trials on pygmy goats, (Capra hicus), novel DNA barcoding technology using the P6-loop of the chloroplast trnL (UAA) intron was compared with the traditional microhistological technique. At its current stage of technological development, this study demonstrated that DNA barcoding did not enhance the ability to detect plant species in herbivore diets. A higher mean species composition was reported with microhistological analysis (79%) as compared to DNA barcoding (50%). Microhistological analysis consistently reported a higher species presence by forage class. For affect positive species identification, microhistology estimated an average of 89% correct detection in control diets, while DNA barcoding estimated 50% correct detection of species. It was hypothesized that a number of factors, including variation in chloroplast content in feed species and the effect of rumen bacteria on degradation of DNA, influenced the ability to detect plant species in herbivore diets and concluded that while DNA barcoding opens up new possibilities in the study of plant-herbivore interactions, further studies are needed to standardize techniques and for DNA bar-coding in this context. / Dissertation/Thesis / M.S. Applied Biological Sciences 2012

Philosophiae Doctor - PhD / Tortoises appear to be successful in arid ecosystems, where they depend on primary production for their predominantly herbivorous diets. The low primary production of arid regions is exacerbated by priodic droughts, so that iteroparous species such as chelonians require mechanisms to overcome resource shortages. The smallest of all tortoises, Homopus signatus signatus, occurs in a dry winter rainfall area in northwestern South Africa that is threatened with aridification due to regional climate change. The overall aim of this study is to understand the ecology of H. s. signatus, particularly in reference to the importance of rainfall.

The purpose of the study was to find alternatives to fences by comparing the frequency of damages on different configurations of chemical treated, mechanically protected and untreated hybrid aspen seedlings, planted on agricultural land. The study also explored whether anthropogenic disturbance (proximity to roads and buildings) had any effect on the frequency of seedlings damages. The study was conducted as a quantitative study with field measurements over the course of a year, in two sample plots with hybrid aspen seedlings planted in May 2016 in Vimmerby kommun, Kalmar län. The field data was compiled into Excel and compared for differences between treatments and proximity to anthropogenic disturbance. The result showed that seedlings closer to anthropogenic disturbance showed a lower frequency of damage. There was no significant difference between the mechanical (Taimitassu) and chemical (Arbinol B) seedling protection. The highest frequency of damages occurred in the summer, peaking in July. In conclusion, when choosing a place to plant hybrid aspen, there should be anthropogenic disturbance to minimize the frequency of browsing.

Globally, human populations are increasing and coastal ecosystems are becoming increasingly impacted by anthropogenic stressors. As eutrophication and exploitation of coastal resources increases, primary producer response to these drivers becomes a key indicator of ecosystem stability. Despite the importance of monitoring primary producers such as seagrasses and macroalgae, detailed studies on the response of these benthic habitat components to drivers remain relatively sparse. Utilizing a multi-faceted examination of turtle-seagrass and sea urchin-macroalgae consumer and nutrient dynamics, I elucidate the impact of these drivers in Akumal, Quintana Roo, Mexico. In Yal Ku Lagoon, macroalgae bioindicators signified high nutrient availability, which is important for further studies, but did not consistently follow published trends reflecting decreased δ15N content with distance from suspected source. In Akumal Bay, eutrophication and grazing by turtles and fishes combine to structure patches within the seagrass beds. Grazed seagrass patches had higher structural complexity and productivity than patches continually grazed by turtles and fishes. Results from this study indicate that patch abandonment may follow giving-up density theory, the first to be recorded in the marine environment. As Diadema antillarum populations recover after their massive mortality thirty years ago, the role these echinoids will have in reducing macroalgae cover and altering ecosystem state remains to be clear. Although Diadema antillarum densities within the coral reef ecosystem were comparable to other regions within the Caribbean, the echinoid population in Akumal Bay was an insufficient driver to prevent dominance of a turf-algal-sediment (TAS) state. After a four year study, declining coral cover coupled with increased algal cover suggests that the TAS-dominated state is likely to persist over time despite echinoid recovery. Studies on macroalgal diversity and nutrients within this same region of echinoids indicated diversity and nutrient content of macroalgae increased, which may further increase the persistence of the algal-dominated state. This study provides valuable insight into the variable effects of herbivores and nutrients on primary producers within a tropical coastal ecosystem. Results from this work challenge many of the currently accepted theories on primary producer response to nutrients and herbivory while providing a framework for further studies into these dynamics.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22287号 / 理博第4601号 / 新制||理||1660(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 酒井 章子, 教授 髙林 純示, 教授 田村 実 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Repeated polyploidization events are thought to be among the most important causes of sympatric speciation throughout evolutionary time. Changes in phenology and trait expressions that arise in polyploids have been shown to affect plant interactions with insect herbivores and pollinators. If these interactions are changed, selection subsequent to the polyploidization event could contribute to further divergence, or increased similarity, of cytotypes. This study was conducted to investigate plant interactions with insect herbivores and pollinators and patterns of selection in tetraploid and octoploid Cardamine pratensis L. (Brassicaceae), and to answer the following questions: i) Is there phenotypic selection on flowering phenology and number of flowers? ii) Is pollen limitation or herbivory most important for variation in reproductive output? iii) During what stages of ovary and ovule development do variation in fitness mainly arise? iv) Can the intensity of interactions be linked to phenology and number of flowers, suggesting that selection is mediated by pollen limitation or herbivory? v) Do intensity of interactions, and of interaction-mediated selection, differ between ploidy levels? From a combination of an observational study of herbivory and a hand pollination experiment, selection was found for earlier flowering in both subspecies. Intensity of herbivory was an important determinant of plant reproductive success, while hand pollination had little effect. Positive effects of flowering time on intensity of herbivory suggest that selection for earlier flowering was mediated by herbivores. Tetraploids initiated flowering later and suffered from more intense herbivory than did octoploids. The direction of selection was similar in both subspecies. However, differences strength of selection and intensity of herbivory suggest that there is a possibility of selection for their further divergence. / Polyploidisering anses vara en av de viktigaste orsakerna till artbildning inom populationer. Skillnader i blomningskaraktärer, såsom fenologi och blomantal, som uppstår i och med polyploidiseringen har visat sig påverka växters interaktioner med såväl pollinatörer som herbivorer. Förändringar i växt-insektsinteraktioner till följd av polyploidiseringen kan leda till selektion för ökade skillnader, eller likheter, mellan cytotyper. Studiens syfte var att undersöka växters interaktioner med insekter i form av pollinatörer och herbivorer, samt att undersöka selektionsmönster hos tetraploida och oktoploida Cardamine pratensis L. (Brassicaceae). Jag ville även besvara följande frågor: i) Sker selektion på blomningstid och blomantal? ii) Vilken växt-insektsinteraktion är viktigast för variation i reproduktionsframgång? iii) Under vilka utvecklingsstadier uppstår den största variationen i fitness? iv) Kan intensiteten av interaktionerna kopplas till blomningsfenologi och blomantal, vilket skulle indikera att selektion förmedlas genom pollenbegränsning eller herbivori? v) Skiljer sig styrkan av interaktionerna, och av interaktionsförmedlad selektion, mellan ploidinivåer? Studien utformades som en kombination av en observationsstudie av herbivori och ett handpollineringsexperiment, och jag fann selektion för tidigare blomning hos de två underarterna. Reproduktionsframgång styrdes av herbivori snarare än pollenbegränsing. Förlust av potentiell fitness genom att fröämnen inte utvecklades till frön var den faktor som starkast påverkade variation i fitness, och detta var också den fas i utvecklingen som bidrog i störst utsträckning till kvantitativ förlust av fitness. Ett positivt samband mellan blomningsfenologi och herbivoriintensitet indikerar att selektion för blomningstid var förmedlad av herbivorer. Tetraploider blommade senare och utsattes för mer intensiva herbivorattacker än oktoploider. Detta, samt skillnader i selektionsstyrka, indikerar att selektion skulle kunna leda till ökad divergens av underarterna.

Along the coast of temperate oceans brown algae of the genus Fucus form dense stands on rocky shores and are keystone species of the coastal ecosystem. These large seaweeds are perennial and function as substrate for many sessile marine organisms, provide shelter for fauna and juvenile fish, and are food source. A number of abiotic (e.g. wave-exposure, salinity and substrate) and biotic (e.g. herbivory and competition) factors structures these communities and determines the abundance and composition of fucoids at each specific site. Earlier studies have shown that herbivores may reduce growth of fucoids, thus affecting their distribution, and at high densities eliminate the species from previously occupied sites. In my thesis I focused on investigating herbivore-seaweed interactions and whether such interactions could influence the geographical range limits of Fucus species. A set of laboratory bioassays and a field survey were conducted (1) to investigate the resistance to grazing by a generalist gastropod between introduced (to Sweden) and native (Iceland) Fucus evanescens (Paper I),  (2) to study the distribution pattern of F. radicans and F. vesiculosus along the Swedish coast and specifically the southern limit of F. radicans, (3) to examine the abundance of herbivores in these two species, and (4) to test the hypothesis that Idotea baltica may contribute to restrict F. radicans to the Bothnian Sea (objective 2-4; Paper II). Fucus evanescens, a species that was introduced to the Swedish coast about 100 years ago, was found to be more resistant to grazing by L. littorea compared to F. evanescens from the native Icelandic populations.  It was also shown to contain a higher amount of phlorotannins; a putative chemical defence to herbivory. This indicates that development of resistance to herbivory could be important for a successful introduction and survival in a new range. No gradual change in the proportion, measured as % cover of either F. radicans or F. vesiculosus was found inside the range of F. radicans and its southernmost limit was abrupt without any corresponding abrupt change in any abiotic factor, e.g. salinity. Herbivores, i.e. Idotea spp., Gammarus spp. and Theodoxus fluviatils were found to be more abundant in F. radicans than in F. vesiculosus thalli indicating a habitat preference for F. radicans.  Further, Idotea baltica, whose range only overlaps with that of F. radicans in the south, was shown to prefer F. radicans over F. vesiculosus, possibly due to its lower content of phlorotannins. Based on these findings I propose that Idotea species may contribute in restricting the southern range of F. radicans, although further experiments, especially regarding competition with the larger F. vesiculosus need to be performed. In conclusion, biotic interactions e.g. the ability of to resist herbivore grazing by e.g. high phlorotannin content or having a structure less attractive as habitat to herbivores may be of importance in determining the geographic range of fucoids. / Längs kusterna i de tempererade haven bildar brunalger av släktet Fucus täta bestånd på klippiga stränder och är ofta nyckelarter i kustekosystemen. Dessa tångarter är fleråriga och utgör substrat för många fastsittande organismer, ger skydd åt små rörliga djur och fiskyngel, samt utgör föda för betare så som gastropoder, amphipoder och isopoder. Faktorer som vågexponering, bottentyp, salthalt, näringshalter, bete och konkurrens strukturerar tångsamhällen och avgör hur vanlig varje tångart är på en viss lokal. I min avhandling har jag fokuserat på interaktionen mellan betare och tång, samt hur viktig denna interaktion är för att avgöra den geografiska utbredningen av tångarter. Tidigare studier har visat att betare kan minska tillväxten hos tång och på så sätt påverka dess utbredning. I höga densiteter kan de beta ner hela bestånd av tång så att den försvinner från lokaler där de tidigare vuxit. Resistens mot bete hos Fucus evanescens, ishavstång, som är introducerad till Skagerrak, Kattegat och sydvästra Östersjön och inhemsk i norra Atlanten och norra Stilla Havet undersöktes i betesförsök (Artikel I). En betare, generalisten Littorina littorea, strandsnäcka, som är inhemsk i Sverige, dit F. evanescens har introducerats, föredrog att äta F. evanescens från Island där den är inhemsk, framför F. evanescens från Sverige. Det här skulle kunna tyda på att ett välutvecklat försvar är viktigt för att alger som blir introducerade till nya områden ska kunna etablera sig i det nya området. Jag undersökte även utbredningen av den nyligen beskrivna tångarten Fucus radicans, smaltång (Artikel II). Resistensen mot betare hos F. radicans jämfördes med resistensen mot bete hos F. vesiculosus, blåstång, som växer tillsammans med F. radicans, genom att undersöka preferensen mellan de två arterna hos Idotea baltica, tånggråsugga (Artikel II). Det fanns ingen gradient i förekomsten av F. radicans eller F. vesiculosus inom F. radicans utbredningsområde. Istället observerades en ganska abrupt gräns för utbredningen av F. radicans i söder. Eftersom I. baltica, vars utbredning överlappar F. radicans utbredning i söder, föredrog att äta F. radicans framför F. vesiculosus, skulle F. radicans utbredning kunna påverkas av I. baltica. Både I. baltica och två andra betare, Gammarus spp. och Theodoxus fluviatilis, var vanligare i F. radicans än i F. vesiculosus i plantor insamlade i fält. Det innebär att de vanligaste betarna, även i fält, föredrar att uppehålla sig i F. radicans och antagligen konsumerar mer av F. radicans. Slutsatsen från de båda studierna är att betare och tångens försvar mot bete har potentialen att påverka utbredning av olika tångarter.