Press releases

Frankfurt am Main, Germany, June 18th 2014. Spanish slugs (Arion lusitanicus) are one of the most common slug species in Central Europe. The animals sometimes nicknamed “killer slugs” are known to do their fair share of damage in fields and gardens. The slug was thought to have originated in Southern Europe. However researchers of the German Biodiversity and Climate Centre and the Goethe University now found out, that the prime example of an invasive species is originally from Central Europe and thus no “immigrant” after all. Control measures, such as the EU regulation on prevention, early warning, rapid response, and management of invasive species which is being discussed currently, would therefore not apply to this species.

For some time conservationists have made aware of the fact that the rapidly growing number of brown Spanish slugs is replacing the native black slug in Central Europe as well as inflicting significant damage on natural vegetation and agricultural products. The numbers speak for themselves: today Arion lusitanicus is the most common species of snail in Germany. It is also ranked among the "100 of the worst" invasive animal and plant species in Central Europe that are thought to have a significant negative impact on biodiversity, economy and health. Allegedly the Spanish Slug made its way to Central Europe with imports of fruit and vegetables in the 1950s.

No Spanish slugs to be found in Spain

When taking stock German researchers however could not find a single individual of the slug in its presumed home country. In the spring of 2010 researchers of the Biodiversity and Climate Research Centre and the Goethe University collected 300 specimens of the snail in 60 locations in France, Spain, the UK and the Benelux countries and identified the species they came from. "Instead of the Spanish slug we found numerous, so-called cryptic species, which are indistinguishable using traditional methods of taxonomy which is based on morphology. Therefore, the animals were identified using DNA sequence data" lead author Prof. Markus Pfenninger, who conducts research on BiK-F and the Goethe University and teaches, explains.

Many cryptic species

Many of the specimens examined did not fit to a previously described, genetically characterized species. "We found a lot of unnamed, sometimes highly divergent haplotypes. This indicates the presence of several undescribed Arion species which we only discover using DNA taxonomy. It follows that Arion is very unresolved genus from a taxonomic point of view." But looking into the genes of the slugs yielded even more insights. Shared mutations in the genetic information of different individuals indicate relationships between them. "On the basis of this we created a phylogenetic tree and related it to the geographic distribution. It showed why we could not find Arion lusitanicus in its alleged homeland. The species is definitely not native to Spain but originated in Central Europe" concludes Pfenninger.

EU-regulations on alien species would not necessarily apply

According to experts there are more than 12,000 non-native species in Europe, and the number is increasing. Alien species are one of the main threats to biodiversity and native species as well as causing immense economic damage, e.g. via yield losses in agriculture. In April 2014 the EU parliament therefore approved a proposal for EU-wide measures to ban further import of non-native species and combatting non-native species which are already at home in EU more effectively. “Whether a species is classified as native or not will influence its management policy. Our research goes to show that we should be more prudent in labeling a species ‘invasive’ or non-native when the evidence for anthropogenic introduction is poor”, says Pfenninger and adds: “Perhaps the rapid increase in Spanish slugs we have seen in the last decades is caused by changes of land use practice. It may seem like an invasion when in truth there isn’t one going on “. 

For further information please contact
Prof. Dr. Markus Pfenninger
Goethe-University &
LOEWE Biodiversity and Climate Research Centre (BiK-F)
Tel. +49 (0)69 7542 1841
Pfenninger@bio.uni-frankfurt.de 

or

Sabine Wendler
LOEWE Biodiversity and Climate Research Centre (BiK-F),
Press officer
Tel. +49 (0)69 7542 1838
Sabine.wendler@senckenberg.de

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Frankfurt am Main, Germany, May 12, 2014. Hydrogen sulphide (H₂S) is a potent inhibitor of aerobic respiration. However populations of shortfin molly fish managed to colonise springs with high concentrations of dissolved hydrogen sulphide. In a new study researchers from LOEWE Biodiversity and Climate Research Centre (BiK-F) and the Goethe University Frankfurt am Main present evidence of genetic changes minimizing the harmful effects of H₂S which enable the fish to survive in this deleterious environment. The study provides insight into the molecular mechanisms of this key adaptation for the first time. It is published online today in "Nature Communications".  

Shortfin molly fishes (Poecilia mexicana) may only measure a few inches, but they are still exceptional. Populations of Poecilia mexicana, whose relatives are the well-known guppy, colonised sulphide-rich volcanic springs in Southern Mexico. In making this particular habitat their home, they have made the impossible possible, because hydrogen sulphide (H₂S), as for many other animal, is lethal. Even at low concentrations the gas blocks the cytochrome c oxidase-complex (COX). The higher the level of hydrogen sulphide, the more the activity of COX is inhibited. As it is essential for respiration, this turns out to be lethal in the end.

Changes in genetic make-up make less susceptible to poison

A team led by Prof. Dr. Markus Pfenninger, LOEWE Biodiversity and Climate Research Centre (BiK-F) and PD Dr. Martin Plath, Goethe University, has taken a closer look at the survivors. Their analysis showed that the COX activity of individuals of shortfin molly fish which colonise H₂S-rich waters remains virtually unchanged under high H₂S concentrations. This is due to a number of changes in the cox1 and cox3 genes, which have only occurred in populations living in the poisonous springs. Thus, transplanting individuals from non-sulphidic habitat to springs with high H₂S levels kills them for sure. 

Molecular mechanisms of adaptation to extreme habitat

"In this paper we analyse the key adaptation to an extreme habitat up to its molecular basis at the level of amino acids. This way, for the first time, we are able to point out, where exactly the adaption has taken place." Pfenninger concludes. The team also modelled three dimensional protein structures in order to shed light on necessary significant structural changes of amino acids in the cox1 gene. Without these structural changes, the colonisation of the H₂S-containing water for the fish would have been impossible. By colonising the poisonous springs, where there are hardly any other competitors, the fish may feed on resistant midge larvae that also occur there. 

Closely related fish follow different paths to adaptation

The study also shows that closely related populations of a species follow parallel as well as disparate paths in response to similar environmental conditions. Three shortfin molly fish populations were sampled for study. Two of the populations show the same changes in their genetic material in adapting to the hostile conditions. However this proved to be not the case for the third population of shortfin molly fish. Whereas these fish also tolerate high levels hydrogen sulphide, the mechanism enabling their adaptation is still subject to ongoing research.

Paper:
Pfenninger, M. et al.: Parallel evolution of cox-genes in H₂S- tolerant fish as key adaptation to a toxic environment – Nature Communications, DOI: 10.1038/ncomms4873 

For more information please contact:
Prof. Dr. Markus Pfenninger
Goethe University &
LOEWE Biodiversity and Climate Research Centre (BiK-F)
Tel. +49 (0)69 7542 1841
Pfenninger@bio.uni-frankfurt.de

or

Sabine Wendler
LOEWE Biodiversity and Climate Research Centre (BiK-F)
Press officer
Tel. +49 (0)69 7542 1838
Sabine.wendler@senckenberg.de

Download press release  and images at
http://www.bik-f.de/root/index.php?page_id=267&ID=692&year=0

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WaterGAP is a hydrological model used to model water shortage, groundwater depletion, and floods and droughts over the land area of the globe. The Frankfurt hydrologist Prof. Petra Döll has examined how good a fit this model provides, using GPS observations and data from the GRACE satellite, which measures the gravitational field of the Earth. The study, published in the current issue of Surveys in Geophysics indicates that WaterGAP needs to be modified.

FRANKFURT. WaterGAP (Water Global Assessment and Prognosis) is a hydrological model used to model water shortage, groundwater depletion, and floods and droughts (e.g. as impacted by climate change) over the land area of the globe. The Frankfurt hydrologist Prof. Petra Döll has examined how good a fit this model provides, using GPS observations and data from the GRACE satellite, which measures the gravitational field of the Earth. The study, published in the current issue of the scientific journal Surveys in Geophysics indicates that WaterGAP needs to be modified.

“In most regions of the globe, WaterGAP underestimates seasonal continental water storage fluctuations and does not retain rainwater for a sufficiently long time on the continents”, is how Petra Döll from the Institute of Physical Geography at Goethe University sums up the findings. “So more water is being stored than the model predicts.”

On a daily basis and with a spatial resolution of approx. 50 km, WaterGAP measures various forms of water flux such as evaporation, groundwater recharge and water flow in rivers, as well as the amount of water stored in the ground, in groundwater, in surface water bodies and as snow. Here, water abstraction for drinking water, industry and agriculture is also taken into account. A variety of data is used in calculating the models: climatic data, data concerning vegetation and soil, as well as socioeconomic and many other data besides.

Due to the uncertain data that is fed in and the simplifications required in a global-scale model, the findings are unreliable. Until now, river flow data has been employed to calibrate and check the quality of the model, but unfortunately this data does not exist for all major rivers. Besides, a model also needs to accurately map the dynamics of the stored water in order, for example, to be able to detect water abstraction by humans.

For this reason, to check the model, Petra Döll decided to use the influence of water masses on the deformation of the Earth’s crust and the gravitational field of the Earth. Periodic changes in water masses deform the Earth’s crust, which causes the position of permanently installed GPS antennae to vary by millimetres. Simultaneously, varying water masses also lead to significant variations in the Earth’s gravitational field. These can be estimated using the GRACE satellite.

Working together with Dr. Mathias Fritsche, a geodesist in Dresden specialising in the data analysis of GPS observations, and Dr. Annette Eicker, a geodesist in Bonn dealing with gravity field computation, Petra Döll checked the WaterGAP calculations for the dynamic of continental water storage and could thus identify the shortcomings of the model.

In the study, the changes in position of about 200 GPS worldwide-distributed antennae were measured and compared to the changes in position that should – according to the WaterGAP calculations – have occurred due to the variations in water masses. In addition the researchers compared the seasonal variations of the continental component of GRACE gravitational fields to the results from WaterGAP. The result showed that WaterGAP underestimates seasonal variations in continental water storage and so in the future it will need to be modified.

A further result of the study is that seasonal variations in the Earth’s gravitational field cannot be used to measure human water abstraction. The reason for this is that there are too few permanently installed GPS antennae, and the accuracy and spatial resolution of GRACE’s field of gravity is too poor. “Only if water abstraction leads to groundwater depletion, i.e. where the amount of water abstracted is greater than the inflow, can GRACE satellite measurements be used to support the quantification of water abstraction”, explains Prof. Döll. This possibility was used in a follow-up study, which has not yet been published. 

The research work was funded by the German Research Foundation as part of its priority programme "Mass transport and mass distribution in the system Earth".

Publications: Döll, P., Fritsche, M., Eicker, A., Müller Schmied, H. (2014): Seasonal water storage variations as impacted by water abstractions: Comparing the output of a global hydrological model with GRACE and GPS observations. Surv Geophys. DOI 10.1007/s10712-014-9282-2

Picture text: The map shows where the WaterGAP model needs to be improved. Red dots mark the location of permanent GPS antennae that indicate that WaterGAP underestimates seasonal water storage. Red areas show where the programme underestimates the amount of water compared to the gravitational field of the Earth, as measured by the GRACE satellite. Within the masked areas, the signal from GRACE is of low significance.

Information: Prof. Petra Döll, Institute of Physical Geography, Tel.: +49-69-798-40219, p.doell@em.uni-frankfurt.de

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