TY - JOUR A1 - Wacker, Alexander A1 - Martin-Creuzburg, Dominik T1 - Biochemical nutrient requirements of the rotifer Brachionus calyciflorus co-limitation by sterols and amino acids JF - Functional ecology : an official journal of the British Ecological Society N2 - It has been proposed that growth and reproduction of animals is frequently limited by multiple nutrients simultaneously. To improve our understanding of the consequences of multiple nutrient limitations (i.e. co-limitation) for the performance of animals, we conducted standardized population growth experiments using an important aquatic consumer, the rotifer Brachionus calyciflorus. We compared nutrient profiles (sterols, fatty acids and amino acids) of rotifers and their diets to reveal consumerdiet imbalances and thus potentially limiting nutrients. In concomitant growth experiments, we directly supplemented potentially limiting substances (sterols, fatty acids, amino acids) to a nutrient-deficient diet, the cyanobacterium Synechococcus elongatus, and recorded population growth rates. The results from the supplementation experiments corroborated the nutrient limitations predicted by assessing consumerdiet imbalances, but provided more detailed information on co-limiting nutrients. While the fatty acid deficiency of the cyanobacterium appeared to be of minor importance, the addition of both cholesterol and certain amino acids (leucine and isoleucine) improved population growth rates of rotifers, indicating a simultaneous limitation by sterols and amino acids. Our results add to growing evidence that consumers frequently face multiple nutrient limitations and suggest that the concept of co-limitation has to be considered in studies assessing nutrient-limited growth responses of consumers. KW - consumer KW - consumer-diet imbalance KW - dietary mismatch KW - fatty acid KW - global change KW - lipid KW - nutrition KW - phytoplankton KW - tetrahymanol KW - zooplankton Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-2435.2012.02047.x SN - 0269-8463 VL - 26 IS - 5 SP - 1135 EP - 1143 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Tang, Kam W. A1 - Backhaus, Liv A1 - Riemann, Lasse A1 - Koski, Marja A1 - Grossart, Hans-Peter A1 - Munk, Peter A1 - Nielsen, Torkel Gissel T1 - Copepod carcasses in the subtropical convergence zone of the Sargasso Sea BT - implications for microbial community composition, system respiration and carbon flux JF - Journal of plankton research N2 - The oligotrophic subtropical gyre covers a vast area of the Atlantic Ocean. Decades of time-series monitoring have generated detailed temporal information about zooplankton species and abundances at fixed locations within the gyre, but their live/dead status is often omitted, especially in the dynamic subtropical convergence zone (STCZ) where the water column stratification pattern can change considerably across the front as warm and cold water masses converge. We conducted a detailed survey in the North Atlantic STCZ and showed that over 85% of the copepods were typically concentrated in the upper 200 m. Copepod carcasses were present in all samples and their proportional numerical abundances increased with depth, reaching up to 91% at 300-400 m. Overall, 14-19% of the copepods within the upper 200 m were carcasses. Shipboard experiments showed that during carcass decomposition, microbial respiration increased, and the bacterial community associated with the carcasses diverged from that in the ambient water. Combining field and experimental data, we estimated that decomposing copepod carcasses constitute a negligible oxygen sink in the STCZ, but sinking carcasses may represent an overlooked portion of the passive carbon sinking flux and should be incorporated in future studies of carbon flux in this area. KW - Sargasso Sea KW - subtropical convergence zone KW - zooplankton KW - carcasses KW - carbon sinking flux Y1 - 2019 U6 - https://doi.org/10.1093/plankt/fbz038 SN - 0142-7873 SN - 1464-3774 VL - 41 IS - 4 SP - 549 EP - 560 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Sperfeld, Erik A1 - Wacker, Alexander T1 - Temperature affects the limitation of Daphnia magna by eicosapentaenoic acid, and the fatty acid composition of body tissue and eggs JF - Freshwater biology N2 - 1. Poikilothermic animals incorporate more polyunsaturated fatty acids (PUFAs) into their cellular membranes as temperature declines, suggesting an increased sensitivity to PUFA limitation in cool conditions. To test this we raised Daphnia magna at different temperatures and investigated the effect of varying dietary PUFA on life history parameters (i.e. growth, reproduction) and the PUFA composition of body tissue and eggs. 2. Upon a PUFA-rich diet (Cryptomonas sp.) females showed higher concentrations of several omega 3 PUFAs in their body tissue at 15 degrees C than at 20 degrees C and 25 degrees C, indicating a greater structural requirement for omega 3 PUFAs at low temperature. Their eggs had an equal but higher concentration of omega 3 PUFAs than their body tissue. 3. In a life history experiment at 15 and 20 degrees C we supplemented a diet of a PUFA-free cyanobacterium with the omega 3 PUFA eicosapentaenoic acid (EPA). The growth of D. magna was more strongly EPA limited at low temperature. A greater requirement for structural EPA at 15 degrees C was indicated by a steeper increase in somatic EPA content with dietary EPA compared to 20 degrees C. 4. At 20 degrees C the development of eggs to successful hatching was high when EPA was supplied to the mothers. At 15 degrees C the hatching success was generally poor, despite of a higher maternal provision of EPA to eggs, compared to that at 20 degrees C, suggesting that EPA alone was insufficient for proper neonatal development at the low temperature. The growth of offspring from mothers raised at 20 degrees C without EPA supplementation was very low, indicating that the negative effects of EPA deficiency can be carried on to the next generation. 5. The fatty acid composition of Daphnia sp. in published field studies shows increasing proportions of saturated fatty acids with increasing environmental temperature, whereas omega 3 PUFAs and EPA show no clear pattern, suggesting that variations in dietary PUFA may mask temperature-dependent adjustments in omega 3 PUFA concentrations of cladocerans in nature. KW - food quality KW - maternal effects KW - polyunsaturated fatty acids KW - resource allocation KW - zooplankton Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-2427.2011.02719.x SN - 0046-5070 VL - 57 IS - 3 SP - 497 EP - 508 PB - Wiley-Blackwell CY - Hoboken ER - TY - THES A1 - Parry, Victor T1 - From individual to community level: Assessing swimming movement, dispersal and fitness of zooplankton T1 - Vom Individuum zur Gemeinschaft: Bewertung von Schwimmbewegungen, Ausbreitung und Fitness von Zooplankton N2 - Movement is a mechanism that shapes biodiversity patterns across spatialtemporal scales. Thereby, the movement process affects species interactions, population dynamics and community composition. In this thesis, I disentangled the effects of movement on the biodiversity of zooplankton ranging from the individual to the community level. On the individual movement level, I used video-based analysis to explore the implication of movement behavior on preypredator interactions. My results showed that swimming behavior was of great importance as it determined their survival in the face of predation. The findings also additionally highlighted the relevance of the defense status/morphology of prey, as it not only affected the prey-predator relationship by the defense itself but also by plastic movement behavior. On the community movement level, I used a field mesocosm experiment to explore the role of dispersal (time i.e., from the egg bank into the water body and space i.e., between water bodies) in shaping zooplankton metacommunities. My results revealed that priority effects and taxon-specific dispersal limitation influenced community composition. Additionally, different modes of dispersal also generated distinct community structures. The egg bank and biotic vectors (i.e. mobile links) played significant roles in the colonization of newly available habitat patches. One crucial aspect that influences zooplankton species after arrival in new habitats is the local environmental conditions. By using common garden experiments, I assessed the performance of zooplankton communities in their home vs away environments in a group of ponds embedded within an agricultural landscape. I identified environmental filtering as a driving factor as zooplankton communities from individual ponds developed differently in their home and away environments. On the individual species level, there was no consistent indication of local adaptation. For some species, I found a higher abundance/fitness in their home environment, but for others, the opposite was the case, and some cases were indifferent. Overall, the thesis highlights the links between movement and biodiversity patterns, ranging from the individual active movement to the community level. N2 - Fortbewegung ist ein Mechanismus, der die Biodiversitätsmuster sowohl über räumliche als auch zeitliche Skalen hinweg prägt. Dabei beeinflusst der Bewegungsprozess die Interaktionen zwischen den Arten, die Populationsdynamik und die Zusammensetzung der Gemeinschaften. Diese Arbeit dient dazu die Auswirkungen der Bewegung auf die Biodiversitätsmuster des Zooplanktons sowohl auf der individuellen als auch gemeinschaftlichen Ebene zu untersuchen. Um auf der individuellen Ebene die Auswirkungen des Bewegungsverhaltens auf die Interaktionen zwischen Räuber und Beute zu untersuchen, wurde eine videobasierte Analyse durchgeführt. Die Ergebnisse zeigten, dass das Schwimmverhalten von großer Bedeutung ist, da es über das Überleben der Tiere im Angesicht von Räubern entscheidet. Darüber hinaus verdeutlichen die Ergebnisse die Rolle des Verteidigungsstatus bzw. der Morphologie der Beutetiere, da diese nicht nur durch die Verteidigung selbst, sondern auch durch die Plastizität des Bewegungsverhaltens, die Beziehung zwischen Beute und Raubtier beeinflussen. Auf der Ebene der Bewegung von Gemeinschaften habe ich ein Mesokosmen-Feldexperiment durchgeführt, um die Rolle der Ausbreitung (zeitlich, d. h. von den Überdauerungsstadien, welche im Sediment gelagert sind, in Kleingewässer, und räumlich, d. h. zwischen Kleingewässer) bei der Strukturierung von Zooplankton-Metagemeinschaften zu untersuchen. Die Ergebnisse konnten zeigen, dass Prioritätseffekte und taxon-spezifische Ausbreitungslimitierungen die Zusammensetzung der Gemeinschaften beeinflussen. Darüber hinaus zeigten die Ergebnisse, dass die unterschiedlichen Ausbreitungsarten (Windausbreitung und Tierverbreitung). Einfluss auf die Gemeinschaftsstrukturen haben. Zusätzlich spielt das Überdauerungsstadien-Reservoir in Sedimenten“, sowie biotische Ausbreitungsvektoren (d. h. Tiere, engl. mobile links), eine wichtige Rolle bei der Besiedlung neuer Habitate. Die lokalen Umweltbedingungen, die eine ankommende Art in einem Habitat vorfindet, sind ein entscheidender Aspekt, der die Struktur der Zooplanktongemeinschaft beeinflusst. Mit Hilfe eines Laborexperiments, für welches Wasserproben aus Kleingewässern/Söllen genutzt wurden, die von einer Agrarlandschaft umgeben sind, konnte ich die Fitness von Zooplanktongemeinschaften in ihrem Heimathabitat vs. in einem neuen Habitat untersuchen. Hierbei konnte ich zeigen, dass die Umweltfilterung ein entscheidender Faktor für die Gemeinschaftsstrukturierung ist, da sich die Zooplanktongemeinschaften der einzelnen Kleingewässer in ihrer Heimatumgebung anders entwickelten als in einer neuen Umgebung. Auf der Art-Ebene, konnte ich jedoch keine eindeutigen Hinweise auf eine lokale Anpassung finden. Bei einigen Arten konnten allerdings höhere Abundanz/Fitness in ihrer Heimatumgebung festgestellt werden, bei anderen war das Gegenteil der Fall, und in einigen F¨allen gab es keine eindeutigen Unterschiede. Zusammenfassend, unterstreicht diese Arbeit die Zusammenhänge zwischen Bewegungs- und Biodiversitätsmustern, die von der aktiven Bewegung des Einzelnen bis hin zur Gemeinschaftsebene reichen. KW - movement KW - zooplankton KW - dispersal KW - video analysis KW - environment filtering KW - Fortbewegung KW - Ausbreitung KW - Videoanalyse KW - Umweltfilterung KW - Zooplankton Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-597697 ER - TY - THES A1 - Paraskevopoulou, Sofia T1 - Adaptive genetic variation and responses to thermal stress in brachionid rotifers N2 - The importance of cryptic diversity in rotifers is well understood regarding its ecological consequences, but there remains an in depth comprehension of the underlying molecular mechanisms and forces driving speciation. Temperature has been found several times to affect species spatio-temporal distribution and organisms’ performance, but we lack information on the mechanisms that provide thermal tolerance to rotifers. High cryptic diversity was found recently in the freshwater rotifer “Brachionus calyciflorus”, showing that the complex comprises at least four species: B. calyciflorus sensu stricto (s.s.), B. fernandoi, B. dorcas, and B. elevatus. The temporal succession among species which have been observed in sympatry led to the idea that temperature might play a crucial role in species differentiation. The central aim of this study was to unravel differences in thermal tolerance between species of the former B. calyciflorus species complex by comparing phenotypic and gene expression responses. More specifically, I used the critical maximum temperature as a proxy for inter-species differences in heat-tolerance; this was modeled as a bi-dimensional phenotypic trait taking into consideration the intention and the duration of heat stress. Significant differences on heat-tolerance between species were detected, with B. calyciflorus s.s. being able to tolerate higher temperatures than B. fernandoi. Based on evidence of within species neutral genetic variation, I further examined adaptive genetic variability within two different mtDNA lineages of the heat tolerant B. calyciflorus s.s. to identify SNPs and genes under selection that might reflect their adaptive history. These analyses did not reveal adaptive genetic variation related to heat, however, they show putatively adaptive genetic variation which may reflect local adaptation. Functional enrichment of putatively positively selected genes revealed signals of adaptation in genes related to “lipid metabolism”, “xenobiotics biodegradation and metabolism” and “sensory system”, comprising candidate genes which can be utilized in studies on local adaptation. An absence of genetically-based differences in thermal adaptation between the two mtDNA lineages, together with our knowledge that B. calyciflorus s.s. can withstand a broad range of temperatures, led to the idea to further investigate shared transcriptomic responses to long-term exposure to high and low temperatures regimes. With this, I identified candidate genes that are involved in the response to temperature imposed stress. Lastly, I used comparative transcriptomics to examine responses to imposed heat-stress in heat-tolerant and heat-sensitive Brachionus species. I found considerably different patterns of gene expression in the two species. Most striking are patterns of expression regarding the heat shock proteins (hsps) between the two species. In the heat-tolerant, B. calyciflorus s.s., significant up-regulation of hsps at low temperatures was indicative of a stress response at the cooler end of the temperature regimes tested here. In contrast, in the heat-sensitive B. fernandoi, hsps generally exhibited up-regulation of these genes along with rising temperatures. Overall, identification of differences in expression of genes suggests suppression of protein biosynthesis to be a mechanism to increase thermal tolerance. Observed patterns in population growth are correlated with the hsp gene expression differences, indicating that this physiological stress response is indeed related to phenotypic life history performance. N2 - Obwohl die kryptische Diversität von Rotatorien (Rädertierchen) und die daraus resultierenden ökologischen Konsequenzen inzwischen sehr gut verstanden sind, sind die zugrunde liegenden molekularen Mechanismen und die Artbildungsprozesse bisher weitgehend unbekannt. Bekannt ist, dass die Temperatur eine bedeutende Rolle in den raum-zeitlichen Verbreitungsmustern der Arten sowie der Leistungsfähigkeit der Organismen, spielt. Es fehlen jedoch konkrete Informationen über die der Thermotoleranz zugrundeliegenden Mechanismen bei Rotatorien. Vor kurzem wurde hohe kryptische Diversität in der unter anderem in Süßwasser vorkommenden Art „Brachionus calyciflorus“ gefunden, so dass diese nun in mindestens vier Arten (B. calyciflorus sensu stricto (s.s.), B. fernandoi, B. dorcas und B. elevatus) unterteilt wurde. Beobachtungen von in Sympatrie vorkommenden Arten haben gezeigt, dass eine zeitliche Suksession innerhalb dieser Arten existiert, was vermuten lässt, dass Temperatur eine entscheidende Rolle bei der Artbildung gespielt haben könnte. Ziel dieser Arbeit ist es, Thermotoleranzunterschiede zwischen Arten des früheren B. calyciflorus-Artenkomplexes durch den Vergleich von phänotypischen und molekularen (Genexpression) Reaktionen auf Temperatur festzustellen. Die in dieser Untersuchung ermittelte kritische Maximaltemperatur wurde als Schätzer für zwischenartliche Hitzetoleranz verwendet. Mit Hilfe eines zweidimensionalen Verfahrens, welches sowohl die Dauer als auch die Stärke des Hitzestresses detektiert, konnte festgestellt werden, dass B. calyciflorus s.s. im Vergleich zu B. fernandoi hitzetoleranter ist. Auf Basis der innerartlichen genetischen Variation erfolgte eine tiefergehende Untersuchung zweier unterschiedlicher maternaler (mtDNA) Evolutionslinien der hitzetoleranteren Art B. calyciflorus s.s mit dem Ziel, unter divergenter Selektion stehende SNPs und Gene zu identifizieren, welche die Anpassung an verschiedene Temperaturen widerspiegeln könnten. Mit Hilfe dieses Experimentes war es möglich, potentiell positiv selektiere Kandidatengene zu identifizieren, welche im Zusammenhang mit dem „Lipidmetabolismus“, dem „Metabolismus und Abbau von Xenobiotika“ sowie dem „Sensorischen System“ stehen. Diese Kandidatengene lassen Rückschlüsse auf lokale Anpassungen zu. Es konnten keine genetischen Unterschiede gefunden werden, die im Zusammenhang mit der Temperaturanpassung der beiden untersuchten Evolutionslinien stehen. Um molekulare Grundlagen für die Toleranz von B. calyciflorus s.s für einen großen Temperaturbereich zu identifizieren, wurde das Transkriptom untersucht. Mit Hilfe der erhobenen Daten konnten Kandidatengene identifiziert werden, die für die Temperaturtoleranz von Bedeutung sind. Der letzte Teil dieser Arbeit konzentrierte sich auf die Untersuchung der Hitzestressantwort in einer hitzetoleranten und einer hitzesensitiven Brachionus Art. Diese Untersuchung konnte erhebliche Unterschiede in den Genexpre-ssionsmustern der beiden Arten aufzeigen. Die deutlichsten Unterschiede der Genexpression wurden hierbei in der Expression von Genen detektiert, die für die sogenannten Hitze-Schock-Proteinen (Heat-shock-proteins: hsp) codieren. In der hitzetoleranten Art B. calyciflorus s.s wurde ein signifikanter Anstieg der hsp-Genexpression bei geringen Temperaturen festgestellt, während bei der hitzesensitiven Art B. fernandoi ein signifikanter Anstieg bei hohen Temperaturen detektiert wurde. Die in dieser Arbeit gefundenen Unterschiede in der Genexpression zeigen, dass Temperaturstress eine Hemmung der Proteinbiosynthese bewirken kann, was zu einer erhöhten Thermotoleranz führt. Darüber hinaus ist Populationswachstum mit der Expression von Hitze-Schock-Proteingenen korreliert. Dies deutet darauf hin, dass die hier beschriebene physiologische Temperaturstressantwort tatsächlich mit den beobachteten phänotypischen Fitnessparametern im Zusammenhang steht. KW - Brachionus KW - zooplankton KW - temperature KW - RNA-seq KW - transcriptome KW - adaptation Y1 - 2019 ER - TY - JOUR A1 - Lukas, Marcus A1 - Wacker, Alexander T1 - Constraints by oxygen and food quality on carbon pathway regulation: a co-limitation study with an aquatic key herbivore JF - Ecology : a publication of the Ecological Society of America N2 - In food webs, herbivores are often constrained by low food quality in terms of mineral and biochemical limitations, which in aquatic ecosystems can co-occur with limited oxygen conditions. As low food quality implies that carbon (C) is available in excess, and therefore a regulation to get rid of excess C is crucial for the performance of consumers, we examined the C pathways (ingestion, feces release, excretion, and respiration) of a planktonic key herbivore (Daphnia magna). We tested whether consumer C pathways increase due to mineral (phosphorus, P) or biochemical (cholesterol and fatty acid) limitations and how these regulations vary when in addition oxygen is low. Under such conditions, at least the capability of the upregulation of respiration may be restricted. Furthermore, we discussed the potential role of the oxygen-transporting protein hemoglobin (Hb) in the regulation of C budgets. Different food quality constraints led to certain C regulation patterns to increase the removal of excess dietary C: P-limited D. magna increased excretion and respiration, while cholesterol-limited Daphnia in addition upregulated the release of feces. In contrast, the regulative effort was low and only feces release increased when D. magna was limited by a long-chain polyunsaturated fatty acid (eicosapentaenoic acid, EPA). Co-limiting oxygen did not always impact the discharge of excess C. We found the food-quality-induced upregulation of respiration was still present at low oxygen. In contrast, higher excretion of excess C was diminished at low oxygen supply. Besides the effect that the Hb concentration increased under low oxygen, our results indicate a low food-quality-induced increase in the Hb content of the animals. Overall, C budgeting is phenotypically plastic towards different (co-) limiting scenarios. These trigger specific regulation responses that could be the result of evolutionary adaptations. KW - carbon budget KW - carbon stoichiometry KW - cholesterol KW - co-limitation KW - Daphnia KW - EPA KW - hemoglobin KW - oxygen KW - phosphorus KW - polyunsaturated fatty acid KW - zooplankton Y1 - 2014 SN - 0012-9658 SN - 1939-9170 VL - 95 IS - 11 SP - 3068 EP - 3079 PB - Wiley CY - Washington ER - TY - JOUR A1 - Lukas, Marcus A1 - Wacker, Alexander T1 - Acclimation to dietary shifts impacts the carbon budgets of Daphnia magna JF - Journal of plankton research N2 - Daphnia responds to low availability of carbon (food quantity) or limiting concentrations of nutrients relative to carbon (C) in excess (food quality) by respectively saving or discharging C via different pathways. We investigated which kind of food limitation leads to a faster regulation in Daphnia C budgets, and whether the pre-assimilative C pathways, ingestion and faeces egestion and the post-assimilative C pathways, excretion and respiration, are regulated concurrently. Daphnia magna were exposed to dietary shifts in different food quantities or qualities; food quality was varied in terms of the essential component, cholesterol. After acclimation to the new diet ranging from 0 to 96 h, C budgets were measured by a radiotracer technique. Dietary shifts in quantity and quality caused Daphnia to quickly adjust their C budgets within 6 h, but different C pathways were affected. A shift to low food quantity reduced Daphnia respiration indicating C retention. In contrast, sudden low quality food caused increased faeces egestion to discharge excess C. Furthermore, we observed a delayed increase in excretion but no change in respiration within the time frame studied. Such time-shifted responses appear to be an appropriate means to keep the costs of physiological adjustments relatively low, which in turn would benefit Daphnia performance. KW - carbon pathway KW - cholesterol KW - zooplankton KW - food quality KW - food quantity Y1 - 2014 U6 - https://doi.org/10.1093/plankt/fbu018 SN - 0142-7873 SN - 1464-3774 VL - 36 IS - 3 SP - 848 EP - 858 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Lukas, Marcus A1 - Sperfeld, Erik A1 - Wacker, Alexander T1 - Growth Rate Hypothesis does not apply across colimiting conditions cholesterol limitation affects phosphorus homoeostasis of an aquatic herbivore JF - Functional ecology : an official journal of the British Ecological Society N2 - 1. Herbivores show stronger control of element homoeostasis than primary producers, which can lead to constraints in carbon and nutrient transfer efficiencies from plants to animals. Insufficient dietary phosphorus (P) availability can cause reduced body P contents along with lower growth rates of animals, leading to a positive relationship between growth and body P. 2. We examined how a second limiting food component in combination with dietary P limitation influences growth and P homoeostasis of a herbivore and how this colimitation influences the hypothesized positive correlation between body P content and growth rates. Therefore, we investigated the responses in somatic growth and P stoichiometry of Daphnia magna raised on a range of diets with different amounts of P and the sterol cholesterol. 3. Somatic growth rates of D. magna increased asymptotically with increasing P as well as with increasing cholesterol availability. The body P content increased with increasing dietary P and stabilized at high dietary P availability. The observed plasticity in D. magna's P stoichiometry became stronger with increasing cholesterol availability, i.e. with decreasing colimitation by cholesterol. 4. At P-limiting conditions, the positive correlation between body P content and growth rate, as predicted by the growth rate hypothesis (GRH) applied to the within-species level, declined with increasing cholesterol limitation and disappeared entirely when cholesterol was not supplied. Thus, even when Daphnia shows no growth response owing to strong limitation by the colimiting nutrient, the body P content may vary substantially, calling into question the unconditional use of herbivores' P content as predictor of a potential P limitation in nature. 5. The observed interaction between dietary P and cholesterol on Daphnia's growth and stoichiometry can be used as a conceptual framework of how colimiting essential nutrients affect herbivore homoeostasis, and provide further insights into the applicability of the GRH within a consumer species. KW - colimitation KW - Daphnia KW - ecological stoichiometry KW - essential resources KW - food quality KW - imbalanced diet KW - nutrient limitation KW - nutritional ecology KW - zooplankton Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-2435.2011.01876.x SN - 0269-8463 VL - 25 IS - 6 SP - 1206 EP - 1214 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Lukas, Marcus A1 - Frost, Paul C. A1 - Wacker, Alexander T1 - The neonate nutrition hypothesis - early feeding affects the body stoichiometry of Daphnia offspring JF - Freshwater biology N2 - Aquatic herbivores consume variable quantities and qualities of food. In freshwater systems, where phosphorus (P) is often a primary limiting element, inadequate dietary P can slow maternal growth and reduce body P content. There remains uncertainty about whether and how dietary effects on mothers are transferred to offspring by way of egg provisioning. Using the keystone herbivore Daphnia, we tested a novel explanation (the neonate nutrition hypothesis') to determine whether the early nutrition of newborns affects their elemental composition and whether the indications of differences in maternal P nutrition found previously might be overestimated. We thus examined the P content of mothers and their eggs from deposition through development to the birth of neonates. We examined further whether very short periods of ingestion (3h) by the offspring alter the overall P content of juvenile Daphnia. We showed that strong dietary P effects on mothers were not directly transferred to their eggs. Irrespective of the supply of P in the maternal diet, the P content of eggs in different developmental stages and in (unfed) neonates did not differ. This indicates that Daphnia mothers do not reduce the quality (in terms of P) of newly produced offspring after intermittent periods (i.e. several days) of poor nutrition. In contrast, the P content of neonates reflected that of their food after brief periods of feeding, indicating that even temporary exposure to nutrient poor food immediately after birth may strongly affect the elemental composition of neonates. Our results thus support the neonate nutrition hypothesis, which, like differential maternal provisioning, is a possible explanation for the variable elemental quality of young Daphnia. KW - ecological stoichiometry KW - food quality KW - maternal effects KW - nutrient limitation KW - zooplankton Y1 - 2013 U6 - https://doi.org/10.1111/fwb.12213 SN - 0046-5070 VL - 58 IS - 11 SP - 2333 EP - 2344 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Koussoroplis, Apostolos-Manuel A1 - Wacker, Alexander T1 - Covariance modulates the effect of joint temperature and food variance on ectotherm life-history traits JF - Ecology letters N2 - Understanding animal performance in heterogeneous or variable environments is a central question in ecology. We combine modelling and experiments to test how temperature and food availability variance jointly affect life-history traits of ectotherms. The model predicts that as mean temperatures move away from the ectotherm's thermal optimum, the effect size of joint thermal and food variance should become increasingly sensitive to their covariance. Below the thermal optimum, performance should be positively correlated with food–temperature covariance and the opposite is predicted above it. At lower temperatures, covariance should determine whether food and temperature variance increases or decreases performance compared to constant conditions. Somewhat stronger than predicted, the covariance effect below the thermal optimum was confirmed experimentally on an aquatic ectotherm (Daphnia magna) exposed to diurnal food and temperature variance with different amounts of covariance. Our findings have important implications for understanding ectotherm responses to climate-driven alterations of thermal mean and variance. KW - Biotic interactions KW - co-limitation KW - Daphnia KW - environmental fluctuations KW - heterogeneity KW - variability KW - vertical migration KW - zooplankton Y1 - 2016 U6 - https://doi.org/10.1111/ele.12546 SN - 1461-023X SN - 1461-0248 VL - 19 SP - 143 EP - 152 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Kiemel, Katrin A1 - Weithoff, Guntram A1 - Tiedemann, Ralph T1 - DNA metabarcoding reveals impact of local recruitment, dispersal, and hydroperiod on assembly of a zooplankton metacommunity JF - Molecular ecology N2 - Understanding the environmental impact on the assembly of local communities in relation to their spatial and temporal connectivity is still a challenge in metacommunity ecology. This study aims to unravel underlying metacommunity processes and environmental factors that result in observed zooplankton communities. Unlike most metacommunity studies, we jointly examine active and dormant zooplankton communities using a DNA metabarcoding approach to overcome limitations of morphological species identification. We applied two-fragment (COI and 18S) metabarcoding to monitor communities of 24 kettle holes over a two-year period to unravel (i) spatial and temporal connectivity of the communities, (ii) environmental factors influencing local communities, and (iii) dominant underlying metacommunity processes in this system. We found a strong separation of zooplankton communities from kettle holes of different hydroperiods (degree of permanency) throughout the season, while the community composition within single kettle holes did not differ between years. Species richness was primarily dependent on pH and permanency, while species diversity (Shannon Index) was influenced by kettle hole location. Community composition was impacted by kettle hole size and surrounding field crops. Environmental processes dominated temporal and spatial processes. Sediment communities showed a different composition compared to water samples but did not differ between ephemeral and permanent kettle holes. Our results suggest that communities are mainly structured by environmental filtering based on pH, kettle hole size, surrounding field crops, and permanency. Environmental filtering based on specific conditions in individual kettle holes seems to be the dominant process in community assembly in the studied zooplankton metacommunity. KW - bulk DNA KW - dispersal KW - DNA-metabarcoding KW - environmental filtering; KW - metacommunity KW - zooplankton Y1 - 2022 U6 - https://doi.org/10.1111/mec.16627 SN - 0962-1083 SN - 1365-294X VL - 32 IS - 23 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Ehrlich, Elias A1 - Gaedke, Ursula T1 - Coupled changes in traits and biomasses cascading through a tritrophic plankton food web JF - Limnology and oceanography N2 - Trait-based approaches have broadened our understanding of how the composition of ecological communities responds to environmental drivers. This research has mainly focussed on abiotic factors and competition determining the community trait distribution, while effects of trophic interactions on trait dynamics, if considered at all, have been studied for two trophic levels at maximum. However, natural food webs are typically at least tritrophic. This enables indirect interactions of traits and biomasses among multiple trophic levels leading to underexplored effects on food web dynamics. Here, we demonstrate the occurrence of mutual trait adjustment among three trophic levels in a natural plankton food web (Lake Constance) and in a corresponding mathematical model. We found highly recurrent seasonal biomass and trait dynamics, where herbivorous zooplankton increased its size, and thus its ability to counter phytoplankton defense, before phytoplankton defense actually increased. This is contrary to predictions from bitrophic systems where counter-defense of the consumer is a reaction to prey defense. In contrast, counter-defense of carnivores by size adjustment followed the defense of herbivores as expected. By combining observations and model simulations, we show how the reversed trait dynamics at the two lower trophic levels result from a "trophic biomass-trait cascade" driven by the carnivores. Trait adjustment between two trophic levels can therefore be altered by biomass or trait changes of adjacent trophic levels. Hence, analyses of only pairwise trait adjustment can be misleading in natural food webs, while multitrophic trait-based approaches capture indirect biomass-trait interactions among multiple trophic levels. KW - community ecology KW - cyclops vicinus KW - dynamics KW - functional traits KW - lake KW - life-cycle KW - natural rotifer KW - phytoplankton KW - trophic cascades KW - zooplankton Y1 - 2020 U6 - https://doi.org/10.1002/lno.11466 SN - 0024-3590 SN - 1939-5590 VL - 65 IS - 10 SP - 2502 EP - 2514 PB - Wiley CY - Hoboken ER -