Organismen von morgen im Experiment von heute – experimentelle Evolution mit Phytoplankton

Der globale Wandel erfasst zunehmend auch die Weltmeere und ihre Lebewelt. Insbesondere Erwärmung und Ozeanversauerung könnte den Beginn der Nahrungskette beeinträchtigen, die mikroskopisch kleinen Pflanzen des Phytoplanktons. Diese Einzeller tragen zur Hälfte der gesamten Biomasse - Produktion auf unserem Planeten bei. Das allermeiste Wissen über ihre Reaktionen auf die globalen Umweltveränderungen hat die Meeresbiologie aus Kurzzeit-Experimenten. Doch die Organismen von morgen könnten auch ganz anders auf die neuen Bedingungen reagieren, sofern sie sich evolutiv anpassen. Der Vortrag stellt den neuen Ansatz von Evolutionsexperimenten in der Meereskunde vor. Dieser ermöglicht es, die Organismen von morgen heute im Labor zu untersuchen. Wie erwartet können sich einige Arten rechtzeitig anpassen, ihre Anpassungsrate ist dabei schneller als die prognostizierten Umweltänderungen. In einem Ausblick werden die evolutionsbiologischen Konzepte auch auf andere Bereiche in der Meeresbiologie übertragen wie die Fischerei

New markers-old questions: population genetics of seagrasses

Marine angiosperms, or seagrasses, continue to be a major focus of marine biologists because of their important ecological role in many coastal ecosystems. Seagrass population biology could benefit from a population genetic perspective because genetic data enable the extraction of useful demographic information such as isolation and gene flow between demes. Moreover, population genetic processes may contribute to the growing ecological risks of local population extinction. Progress in seagrass genetics is partly driven by novel genetic markers which detect variation at the DNA level and overcome the limited polymorphism of allozymes. Key results of studies in the past decade, mostly using RAPD and microsatellites, were (1) considerable genetic and genotypic (clonal) diversity is present in several species in contrast to earlier notions of low polymorphism detected at allozyme loci, and (2) genetic differentiation among populations seems to be the rule despite earlier reports of genetic uniformity. Pronounced genetic structure was detected between populations of 4 species examined thus far (Posidonia oceanica, P. australis, Zostera marina, Thalassia testudinum). The FST estimates varied widely and ranged from 0.01 to 0.623 across studies and species. Genetic differentiation at a systematic range of scales was only studied in eelgrass Zostera marina, where it was positively correlated with geographic distance. The high polymorphism of RAPD or microsatellite markers will allow the augmention of indirect estimates of gene flow by methods detecting individual immigration events through paternity analysis or assignment tests. Important conservation related issues such as the level of inbreeding and the effective population size have also been obtained from genetic marker data, but results are too scarce at the moment to allow generalizations. In Zostera marina and Posidonia australis, several population genetic attributes such as clonal diversity, mating system and effective population size varied among populations within species, highlighting that there is no Œtypical¹ population. An important gap in our knowledge is whether the effects of natural population fragmentation and patchiness enhance the genetic isolation of populations due to anthropogenic disturbances. It is also unclear whether genetic differentiation displayed at marker loci are correlated with fitness-related plant traits, and whether genetic or genotypic diversity is important for medium- to long-term meadow persistence. An assessment of the genetic and genotypic diversity at marker loci should be combined with experiments on the ecological plasticity and reaction norms of genotypes composing the populations in question. This way, the role of genetic diversity for seagrass population maintenance and growth in the face of changing environmental conditions can be evaluated

1. Wochenbericht AL509

Wochenbericht FS Alkor Reise 509, Fahrtabschnitt 15.05 – 20.05.201

A summer heat wave decreases the immunocompetence of the mesograzer, Idotea baltica

Extreme events associated with global change will impose increasing stress on coastal organisms. How strong biological interactions such as the host-parasite arms-race are modulated by environmental change is largely unknown. The immune system of invertebrates, in particular phagocytosis and phenoloxidase activity response are key defence mechanisms against parasites, yet they may be sensitive to environmental perturbations. We here simulated an extreme event that mimicked the European heat wave in 2003 to investigate the effect of environmental change on the immunocompetence of the mesograzer Idotea baltica. Unlike earlier studies, our experiment aimed at simulation of the natural situation as closely as possible by using long acclimation, a slow increase in temperature and a natural community setting including the animals' providence with natural food sources (Zostera marina and Fucus vesiculosus). Our results demonstrate that a simulated heat wave results in decreased immunocompetence of the mesograzer Idotea baltica, in particular a drop of phagocytosis by 50%. This suggests that global change has the potential to significantly affect host-parasite interaction

Innate versus adaptive immunity in sticklebacks: evidence for trade-offs from a selection experiment

In vertebrates, the immune system consists of two arms of different characteristics: the innate and the acquired immune response. Parasites that are only shortly exposed to the immune system are most efficiently attacked by fast, constitutive innate immune mechanisms. Here, we experimentally selected within four fish families for high innate resistance versus susceptibility of three-spined sticklebacks (Gasterosteus aculeatus) against infection with the eye-fluke (Diplostomum pseudospathacaeum), a parasite whose metacercariae are protected from the immune system within the eye lens. We predicted that in families with high susceptibility, the adaptive immune system would be upregulated when challenged with infection. In accordance, we found that MHC class IIB expression is increased by approximately 50% in those lines selected for higher parasite load (i.e. low innate response). This suggests extensive genetic correlations between innate and adaptive immune system and/or crosstalk between both lines of defense. An efficient, specific innate immune response might reduce overall activation of the immune system and potentially alleviate associated effects of immunopatholog

Host–parasite coevolution - rapid reciprocal adaptation and its genetic basis

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