2019 IBS Dissertation Awardee – Johannes Wessely

Synopsis

The possible consequences of climate change for the future of biodiversity have become an active field of research. Individual species may respond to the altered climatic conditions by phenotypic or evolutionary adaptation and/or by shifting their geographical distributions Indeed, growing empirical evidence suggests that plants and animals have already started to shift their ranges in response to the last decades’ warming trends. The pronounced climatic change predicted until the end of the 21st century will further increase pressure on species to adapt their geographical distributions and hence likely accelerate these range dynamics. Anticipative management requires predictive models of these dynamics for minimizing negative effects on biodiversity.

Species distribution models (SDMs) are the most widely used method to predict how the spatial distributions of species are going to change under different future climatic conditions. One of the criticized simplifications of SDMs, is the negligence of demographic and dispersal processes involved in range shifts. In order to overcome these shortcomings so called hybrid models have been developed, which combine SDMs with demographic and dispersal simulations.

Within my dissertation, I use such a hybrid model to investigate the influence of different processes shaping species distributions as well as associated uncertainties. In the first study (Hülber et al., 2016) I, together with my co-authors, assess the effect of short term climate variability on predicted 21^st century range changes of endemic mountain plants, and emphasise the importance of considering the appropriate temporal resolution when parameterizing and applying range dynamic models. In the second study (Wessely et al., 2017), I incorporate different habitat based conservation measures into models of future range dynamics for 51 species from three taxonomic groups (vascular plants, butterflies and grasshoppers) in Central Europe. I conclude that none of the applied measures is able to fully compensate the negative impact of expected climate change on regional populations. The third paper (Kirchheimer et al., 2018) takes a longer term, historical perspective. I model the Holocene range expansion of an alpine buttercup (Ranunculus kuepferi), in order to disentangle the impacts of different processes on the geographical success of the asexual lineage of this species in comparison to its sexual relative. I show that niche differentiation of the asexual linage is the main driver of the observed geographical pattern in this species, although a switch of the reproductive strategy potentially has a huge additional effect on successful range expansion. In the fourth study (Cotto et al., 2017), I analyse the response of alpine plant species to climate change incorporating adaptation via mutations. I show that their evolutionary rescue is constrained by long life spans of adults producing maladapted offspring. Finally (Wessely et al., in prep.), I show that genetic patterns in populations of alpine plant species may shift towards alleles adapted to colder climatic conditions under climate change. The underlying process shaping this pattern is intraspecific competition, blocking warm adapted individuals from colonializing sites preoccupied by cold adapted individuals.

Cotto, O., Wessely, J., Georges, D., Klonner, G., Schmid, M., Dullinger, S., Thuiller, W. & Guillaume, F. (2017) A dynamic eco-evolutionary model predicts slow response of alpine plants to climate warming. Nature Communications, 8, 15399.

Hülber, K.*, Wessely, J.*, Gattringer, A.*, Moser, D., Kuttner, M., Essl, F., Leitner, M., Winkler, M., Ertl, S., Willner, W., Kleinbauer, I., Sauberer, N., Mang, T., Zimmermann, N.E. & Dullinger, S. (2016) Uncertainty in predicting range dynamics of endemic alpine plants under climate warming. Global Change Biology, 22, 2608-2619 (* joint first authors).

Kirchheimer, B.*, Wessely, J.*, Gattringer, A.*, Hülber, K., Moser, D., Schinkel, C.C., Appelhans, M., Klatt, S., Caccianiga, M. & Dellinger, A. (2018) Reconstructing geographical parthenogenesis: effects of niche differentiation and reproductive mode on Holocene range expansion of an alpine plant. Ecology Letters, 21, 392-400 (* joint first authors).

Wessely, J.*, Hülber, K.*, Gattringer, A., Kuttner, M., Moser, D., Rabitsch, W., Schindler, S., Dullinger, S. & Essl, F. (2017) Habitat-based conservation strategies cannot compensate for climate-change-induced range loss. Nature Climate Change, 7, 823 (*joint first authors).

Wessely, J., Gattringer, A., Hülber, K., Klonner, G., Moser, D., Dullinger, S (in preperation) Intraspecific competition may restrict adaptation of alpine plant species to a warming climate

Statement of significance

Hybrid models combine advantages of SDMs, such as easy parameterization and detailed representation of spatio-temporal variation in climatic suitability, with the possibility to evaluate impacts of various factors on demographic and dispersal processes. Among these factors, I focused on inter-annual climatic variability, human habitat fragmentation, changes in mating systems, climatic niche evolution, and intra-specific variation in my thesis. I found that all of these factors have potentially strong effects on how the ranges of species respond to climate change and may even lead to counter-intuitive dynamics. In conclude that models able to incorporate these factors are needed to reliably assess threats to species from future environmental change.

However, important processes are still missing in the models I used in my thesis. This is particularly true for biotic interactions. Range dynamics may, for example, strongly depend on competitive interactions with both the resident communities and simultaneously migrating species within the same ecosystem and/or geographic region. The model development in this thesis includes a first step into this direction, as intra-specific interactions are already incorporated. In future projects, I will additionally incorporate interactions across trophic levels (modelling butterflies and their larval host plants) as well as competitive interactions between alpine plant species.

Dissertation chapters

Cotto, O., Wessely, J., Georges, D., Klonner, G., Schmid, M., Dullinger, S., Thuiller, W. & Guillaume, F. (2017) A dynamic eco-evolutionary model predicts slow response of alpine plants to climate warming. Nature Communications, 8, 15399.

https://www.nature.com/articles/ncomms15399

Hülber, K.*, Wessely, J.*, Gattringer, A.*, Moser, D., Kuttner, M., Essl, F., Leitner, M., Winkler, M., Ertl, S., Willner, W., Kleinbauer, I., Sauberer, N., Mang, T., Zimmermann, N.E. & Dullinger, S. (2016) Uncertainty in predicting range dynamics of endemic alpine plants under climate warming. Global Change Biology, 22, 2608-2619 (* joint first authors).

https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13232

Kirchheimer, B.*, Wessely, J.*, Gattringer, A.*, Hülber, K., Moser, D., Schinkel, C.C., Appelhans, M., Klatt, S., Caccianiga, M. & Dellinger, A. (2018) Reconstructing geographical parthenogenesis: effects of niche differentiation and reproductive mode on Holocene range expansion of an alpine plant. Ecology Letters, 21, 392-400 (* joint first authors).

https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.12908

Wessely, J., Hülber, K., Gattringer, A., Kuttner, M., Moser, D., Rabitsch, W., Schindler, S., Dullinger, S. & Essl, F. (2017) Habitat-based conservation strategies cannot compensate for climate-change-induced range loss. Nature Climate Change, 7, 823.

https://www.nature.com/articles/nclimate3414

Wessely, J., Gattringer, A., Hülber, K., Klonner, G., Moser, D., Dullinger, S (in preperation) Intraspecific competition may restrict adaptation of alpine plant species to a warming climate … see more about it at IBS Malaga 2019!