The influence of eutrophication on sexual selection in sticklebacks

Jordens ekologiska system undergår för tillfället stora förändringar pga. människans aktiviteter. Ett växande antal studier visar att dessa förändringar påverkar naturliga och sexuella urvalet och därmed evolutiva processer. Målet med detta arbete var att undersöka effekterna av omgivningsförändringar på sexuella urvalet genom att använda den ökade övergödningen inom storpiggen Gasterosteus aculeatus lekområden som modell system. Sexuella urvalet är en viktig evolutiv kraft med följder på populations- och artnivå (Kapitel 1). Avhandlingens olika delar fokuserar på övergödningens effekter på upptäckandet av partners, användningen av visuella- och doftsignaler i partnersval, och fördelningen av parningsframgången mellan bobyggande hanar. I Kapitel II och III simuleras hur grumlighet orsakad av fytoplankton påverkar hastigheten med vilken potentiella partners påträffas, genom effekter på synligheten. Resultaten visar att normala algblomningar i Östersjön har en måttlig effekt på finnandet av potentiella partners. Detta tyder på att algblomningarna troligen inte kommer att minska på selektiva parningen pga. ökade sökkostnader. I Kapitel IV visas att storspiggen ändrar relativa användningen av olika signaler när vattnets grumlighet ökar; visuella signaler minskar i betydelse medan doftsignaler ökar i betydelse. Samtidigt underlättas användandet av doftsignaler av ändringar i vattnets kemiska sammansättning då fotosyntesen intensifieras (Kapitel V). Lek i övergödda vatten kan ändå vara kostsamt både på individ- och populationsnivån, då parasiterade hanar, som troligen är dåligt genetiskt anpassade till sin miljö, lyckas få mer ägg i sina bon än friskare hanar som troligen är av högre genetisk kvalitet (Kapitel VI). Övergödningen påverkar således partnersval och konkurrensen om partners genom att påverka upptäckandet av potentiella partners, evalueringen av partners och fördelningen av partners inom lekområdena. De följder detta kan ha för evolutionen av sexuellt selekterad egenskaper och för populationers dynamik och livskraft är dock oklara. Avhandlingen visar på svårigheten att förutse följderna av omgivningsförändringar för sexuella urvalet och effekterna på individ och populationsnivå.The increasing ecological footprint of the human population alters ecosystems worldwide. A growing number of studies reveal that human-induced changes interfere with natural and sexual selection. The aim of this thesis was to determine how environmental change alters sexual selection by using eutrophication of the breeding habitats of the threespine stickleback Gasterosteus aculeatus as a model system. Sexual selection is an important evolutionary process, with consequences at individual, population and species level (Chapter I). The different parts of the thesis focus on the influence of eutrophication on mate detection, the use of visual and olfactory mate choice cues, and the distribution of mating success among nesting males. In Chapter II and III, we simulate how phytoplankton turbidity decreases mate encounter rate by constraining the visual range. We show that the reduction in mate encounter rate is moderate at the breeding grounds in the Baltic Sea at normal spring bloom turbidity values. This suggests that phytoplankton turbidity is unlikely to decrease assortative mating due to increased search costs. Chapter IV shows that sticklebacks alter the use of cues used in mate choice when visibility decreases, reducing the use of visual cues and increasing the use of olfactory cues. Moreover changes in the water chemistry in eutrophied areas, caused by intensified photosynthetic production, seem to facilitate the use of olfactory cues (Chapter V). However, a field experiment revealed that breeding in eutrophied waters could be costly at both the individual and the population level, since more parasitized males received more eggs in eutrophied waters, although these males most likely are of low genetic quality (Chapter VI). Eutrophication clearly affects mate choice and mate competition by influencing mate detection, mate assessment and the distribution of mates on the breeding grounds, but the consequences this may have on sexual selection on traits and ultimately on population dynamics and persistence remain unclear. The thesis shows the difficulty in predicting the consequences of human-induced environmental change on sexual selection at the individual and the population level

The chemical ecology of copepods

An increasing number of studies show the importance of chemical interactions in the aquatic environment. Our understanding of the role of chemical cues and signals in larger crustaceans has advanced in the last decades. However, for cope-pods, the most abundant metazoan zooplankton and essential for the functioning of the marine food web, much is still unknown. We synthesize current knowledge about chemical ecology of copepods including foraging, survival and reproduction. We also compile information on the sensory apparatus and new analytical approaches that may facilitate the identification of signal molecules. The review illustrates the importance of chemical interactions in many aspects of copepod ecology and identi-fies gaps in our knowledge, such as the lack of identified infochemicals and electro-physiological studies to confirm the function of sensory structures. We suggest approaches that are likely to further our understanding of the role of chemical inter-actions in the pelagic ecosystem

Physiology and dormancy of the aquatic angiosperm potamogeton crispus L. turions

University of Minnesota Ph.D. dissertation. December 2013. Major: Plant Biological Sciences. Advisor: Florence Gleason. 1 computer file (PDF); ix, 147 pages, appendices A-D.Vegetative buds (turions) are the major source of propagation for the aquatic invasive angiosperm, Potamogeton crispus L. (Potamogetonaceae). An understanding of the regulation of turion dormancy could lead to better methods of population control. The majority of Potamogeton crispus turions remain dormant over the summer and sprout in the autumn, while a small subset of turions remain dormant for an unspecified time. Hormonal control of dormancy in aquatic plant vegetative propagules is not well understood. For this study turions were divided into two different age groups, newly formed (current season) and older than one year (overwintered). The effect of varying light durations and temperatures on sprouting was monitored in these different groups. Non-structural carbohydrates, photosynthesis, and aerobic respiration were measured to determine metabolic activity. We also measured abscisic acid concentrations and sprouting levels in turions that were exposed to various hormones, temperatures, and light durations to elucidate hormonal control of dormancy. Current season turions were found to sprout mainly in response to day length and were metabolically active over a 6 week period. They are in a semi-dormant state and 60-70% will sprout in the autumn. The remaining current season turions presumably go into a state of deep dormancy and remain dormant over the winter. Turions that have overwintered are not photosynthetically active, have stable carbohydrate levels, and can remain dormant but viable for several years. Under laboratory conditions, they sprouted mainly in response to an increase in water temperature. These different age groups correspond to different turion physiological states and can explain sprouting variability recorded by other researchers. Current season turions produce and sprout in response to changes in ABA levels. A reduction of ABA in new turions is correlated with the breaking of dormancy. Overwintered turions do not sprout in response to ABA or GA changes. The results indicate two different pathways utilized by P. crispus turions to maintain and break dormancy

Selective silicate-directed motility in diatoms

Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 1012 mol Si per year, which makes them the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under dSi-limited conditions in a chemokinetic response and, if gradients of this resource are present, increased directionality of cell movement promotes chemotaxis. The ability to exploit local and short-lived dSi hotspots using a specific search behaviour likely contributes to micro-scale patch dynamics in biofilm communities. On a global scale this behaviour might affect sediment–water dSi fluxes and biogeochemical cycling

Evaluation of Fast Generation Cycling in Oat (Avena sativa)

Cereal breeding programs are interested in increasing the number of generations per year to reduce the time needed to develop new cultivars. A common method to accomplish this is to extend the photoperiod to speed up plant growth. For oat, this method is problematic because the species responds to changes in light and temperature. Current methods of fast generation cycling in oat require embryo rescue, which is labor intensive and has a low success rate. Recently a method was developed using increased photoperiod and foliar mineral supplement to reduce generation time for wheat and barley. We evaluated this newly published method in oat and found that anthesis occurred 15 ± 3 days faster, however there was a 3-fold reduction in seed count and a 2-fold reduction in inflorescence weight. In addition, we measured endogenous ascorbate to evaluate the physiological status of the plants under fast generation cycling conditions. For oat, fast generation cycling would be effective to more rapidly advance populations using single seed descent, but not as useful when seed yield is important

Looking at Cell Wall Components with Our Customers in Mind

Fiber digestibility of alfalfa for animal nutrition is a complex system encapsulating animal, plant, and microbe biological traits. Understanding all components within the system is key to predicting forage quality. We investigated the relationship between alfalfa cell wall components and invitro neutral detergent fiber digestibility (IVNDFD) speed (16-hr) and potential (96-hr) of by cattle ruminant microbes. A composite alfalfa (Medicago sativa L.) population from seven commercial cultivars underwent two cycles of bidirectional selection for plants with low or high stem 16-hr IVNDFD and low or high stem 96-hr IVNDFD. The resulting selected populations were then evaluated by near inferred spectrometry for structural cell wall components and thier relationship with IVNDFD. Hemi-cellulose and cellulose components were found to have a greater negative correlation (-0.85 & -0.86) on the speed of digestion (16-hr IVNDFD) than lignin (-0.70). Whereas, for the overall potential of stem digestibility, lignin (-0.89) had the greatest negative correlation. The relationship between cellulose and lignin with IVNDFD was futher supported with the use of a path model. Lignin and 96-hr IVNDFD had the strongest broad sense heritability across the populations (0.74 & 0.70 respectively). Pectin components correlated positively with speed of digestion (0.41) but had limited correlation on the overall digestibility potential. As IVNDFD increased with each breeding cycle, it remained stable across environments along with concentrations of total cell wall components, lignin, hemi-cellulose, and pectin. However, the cellulose concentrations were not stable across environments. Cell wall components such as hemi-cellulose and lignin could be used as selection traits for increased IVNDFD breeding and may be a way to link invitro digestibility to plant trait genes for genomic selection

Adult and offspring size in the ocean over 17 orders of magnitude follows two life history strategies

Explaining variability in offspring vs. adult size among groups is a necessary step to determine the evolutionary and environmental constraints shaping variability in life history strategies. This is of particular interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical and biological forcing factors in space and time. We compiled adult and offspring size for 407 pelagic marine species covering more than 17 orders of magnitude in body mass including Cephalopoda, Cnidaria, Crustaceans, Ctenophora, Elasmobranchii, Mammalia, Sagittoidea, and Teleost. We find marine life following one of two distinct strategies, with offspring size being either proportional to adult size (e.g., Crustaceans, Elasmobranchii, and Mammalia) or invariant with adult size (e.g., Cephalopoda, Cnidaria, Sagittoidea, Teleosts, and possibly Ctenophora). We discuss where these two strategies occur and how these patterns (along with the relative size of the offspring) may be shaped by physical and biological constraints in the organism's environment. This adaptive environment along with the evolutionary history of the different groups shape observed life history strategies and possible group-specific responses to changing environmental conditions (e.g., production and distribution)

An affordable and automated imaging approach to acquire highly resolved individual data—an example of copepod growth in response to multiple stressors

Individual trait variation is essential for populations to cope with multiple stressors and continuously changing environments. The immense number of possible stressor combinations and the influence of phenotypic variation makes experimental testing for effects on organisms challenging. The acquisition of such data requires many replicates and is notoriously laborious. It is further complicated when responses occur over short time periods. To overcome such challenges, we developed an automated imaging platform to acquire temporally highly resolved individual data. We tested this platform by exposing copepods to a combination of a biotic stressor (predator cues) and a toxicant (copper) and measured the growth response of individual copepods. We tested the automatically acquired data against published manually acquired data with much lower temporal resolution. We find the same general potentiating effects of predator cues on the adverse effects of copper, and the influence of an individual’s clutch identity on its ability to resist stress, between the data obtained from low and high temporal resolution. However, when using the high temporal resolution, we also uncovered effects of clutch ID on the timing and duration of stage transitions, which highlights the importance of considering phenotypic variation in ecotoxicological testing. Phenotypic variation is usually not acknowledged in ecotoxicological testing. Our approach is scalable, affordable, and adjustable to accommodate both aquatic and terrestrial organisms, and a wide range of visually detectable endpoints. We discuss future extensions that would further widen its applicability

Solid phase extraction and metabolic profiling of exudates from living copepods

Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding or induce defensive traits in prey organisms. However, little is known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid phase extraction setup that allows for extraction of exuded metabolites from live copepods. We captured exudates from male and female Temora longicornis and analyzed the content with high resolution LC-MS. Chemometric methods revealed 87 compounds that constitute a specific chemical pattern either qualitatively or quantitatively indicating copepod presence. The majority of the compounds were present in both female and male exudates, but nine compounds were mainly or exclusively present in female exudates and hence potential pheromone candidates. Copepodamide G, known to induce defensive responses in phytoplankton, was among the ten compounds of highest relative abundance in both male and female extracts. The presence of copepodamide G shows that the method can be used to capture and analyze chemical signals from living source organisms. We conclude that solid phase extraction in combination with metabolic profiling of exudates is a useful tool to develop our understanding of the chemical interplay between pelagic organisms