Senckenberg Research

Session 5







18. January 2018, 3.10 - 4.30 pm


3.10-3.30 pm

Dr. Eva Koch, University of Zurich, Switzerland

Combining transcriptomic and fitness data to study plastic and evolved responses to environmental changes

Eva Koch & Frédéric Guillaume

Organisms can show plastic and evolutionary responses when adapting to changing environments. The two responses can be efficiently studied with whole transcriptome sequencing, which has become a powerful tool able to give us detailed insights into the underlying physiological processes. However, it is challenging to understand how certain components are ultimately linked to fitness and adaption. We therefore measured gene expression using RNA-seq and a fitness estimate (offspring number) to study the plastic and evolved responses in the model organism Tribolium castaneum to understand the role of gene expression for adaptation. We used an experimental evolution approach in which we exposed the beetles to two different stressors (drought and heat) and the combination of both. Since most species will experience climate warming with other changes, studying the joint response to multiple stressors is important because trade-offs may emerge when responses to different stressors cannot be optimized simultaneously. We found that the responses of fitness and gene expression were stronger under higher temperatures than reduced humidity, with little overlap among their differentially expressed genes. However, the joint stress response included most of the genes found in single stress treatments. Combining fitness and expression data, we further identified condition specific modules of co-expressed genes that were related to fitness and, for the first time, estimated selection gradients on single gene expression levels. By measuring expression after 20 generations in selection lines, we could show that there was a positive correlation between the selection intensity on gene expression levels in the first generation and the evolved response of expression in our selection lines. Yet, the evolved responses were in general opposed to the immediate plastic changes elicited by stress responses in the first generation. Our approach shows that we can gain a deeper understanding of the evolution of adaptation to new environments by joining classical evolutionary quantitative genetics with modern genomic techniques.


3.30-3.50 pm

Dr. Janne Swaegers, Freie Universität Berlin, Germany

The evolution of transcriptome responses to global warming in a damselfly using a space-for-time approach

Janne Swaegers, Katina Spanier, Robby Stoks

Global warming has caused phenotypic changes in ectotherms over the last decades. We however still lack knowledge of the underlying molecular pathways leading to responses to mild warming and the relative importance of plasticity and adaptation to this response. We assessed gene expression patters in response to mild warming and identified molecular pathways associated with plastic and constitutive responses across northern and southern populations of the damselfly Ischnura elegans. Thermal responses in southern larvae are considered a good proxy for the expected responses of northern larvae when they have enough time to adapt to the expected temperature increase. Larvae were collected from regions differing 4°C (corresponding to the predicted 4°C temperature increase by 2100) in their mean summer water temperatures and experimentally exposed to these temperatures in a common environment. Our results suggest that 1/ Northern populations respond plastically to a 4°C thermal difference while southern populations do not show this thermal inducement of gene expression. 2/ During their evolutionary history southern populations have partly adapted to higher temperatures through genetic accommodation of these plastic responsive genes. 3/ Both plastic and adaptive responses to mild warming are facilitated by changes in metabolic pathways rather than stress response pathways.


3.50-4.10 pm

Dr. Felicitas Erzinger (née Hoppeler)

Running dry: gene expression patterns associated with extreme hydrological regimes in aquatic caddisfly larvae

Felicitas Erzinger, Björn Rotter, Nicolas Krezdorn, Steffen Pauls

Inhabitants of naturally intermittent streams necessarily experience and are adapted to dealing with radical shifts in abiotic conditions when surface water subsides and streams run dry. While intermittent streams are common and harbor a diverse invertebrate fauna, physiological responses associated with the sudden transition from an aquatic to terrestrial environment during drought are poorly understood. Here, we used an experimental approach to study this striking physiological ability in the caddisfly Stenophylax permistus by means of changes in gene expression levels using Massive Analysis of cDNA Ends (MACE), a digital and transcriptome-wide gene expression profiling technique. Specifically, we compared larval individuals experimentally held under two different hydrological treatments: wet, i.e. complete inundation and dry-down, i.e. loss of free surface water over time. Our results suggest that energy and water saving mechanisms are critical survival mechanisms in order to overcome drought. Further, gradually induced environmental changes, which closely mimic prevailing situations in the natural environment, seemingly induce gradual responses in the expression of genes.


4.10-4.30 pm

Prof. Jonathon Stillman, UC Berkeley and San Francisco State University, USA

Adaptive differences in response to pH and temperature variability in two species of porcelain crab

Jonathon Stillman & Eric Armstrong

Functional genomic responses to environmental variation are thought to reflect the capacity of organisms to respond to climate change. There have been relatively few studies examining differences in those functional genomic responses in species that are adapted to different levels of environmental variation.  Here, we examined the transcriptomes of two sympatric species of porcelain crab from different thermal microhabitats. Petrolisthes cinctipes lives in the intertidal zone and routinely experiences thermal variation during low tide. Petrolisthes manimaculis lives lower on the shore in a more constant thermal environment. Both crabs experience routine daily and seasonal pH variation when immersed.  Crab specimens were exposed to constant or variable pH and temperature conditions and samples for RNA-seq were taken after an acute exposure (1 day) and after acclimation (2 weeks). Differentially expressed genes varied between P. cinctipes and P. manimaculis, suggesting differences in the capacity of these species to respond to variation in pH and temperature through cellular regulation of ion pumping and the cellular stress response. No differences in the expression of genes involved in ATP generation suggest that regulation of mitochondrial volume and energetics is important for plasticity in response to pH and temperature variation. Our results also highlight challenges involved with functional genomics analyses in non-model organisms and the need for more genomic information in organisms for which responses to climate change are the central focus of study.