Department Aquatic Ecology

Eco-evolutionary responses of natural populations to climate change: insight from cryptic species

Why this project?

Human induced global change is challenging species persistence and imposing strong natural selection. Climate change, in particular, has strong effects via a range of environmental alterations (e.g. rise in temperatures, glacial retreat, altered hydrodynamics and novel species interactions). How organisms respond to these multiple challenges depends on their capacity to migrate to suitable areas, their inherent ability to cope with altered conditions (e.g. via phenotypic plasticity) and their ability to adapt to the changing conditions (i.e. via heritable changes).

Biological diversity of alpine taxa can be particularly strongly affected by global change due their high degree of specialization and high sensitivity to change. Ecological biodiversity assessments (e.g. species diversity) are strongly dependent on taxonomic species identification. However, to understand how biological diversity responds to environmental change over time, it is necessary to understand the underlying evolutionary processes and, hence, the correct identification of evolutionary units is important. With the application of molecular genetic tools, it is becoming increasingly clear that cryptic species (i.e. morphologically indistinguishable but genetically distinct units) are common in many taxa – including Baetid mayflies. The presence of such cryptic species challenges the estimates of biological diversity and, importantly, our ability to predict long-term responses of biological diversity to environmental change.

In this project, we aim to understand how ecological (e.g. landscape structure and habitat availability) and evolutionary (phenotypic variation and gene flow) affect responses of alpine stream macroinvertebrates to climate change. We specifically focus on eco-evolutionary processes within putative cryptic species.

Study system: Alpine stream catchments across Switzerland. Focal species is the common alpine mayfly Baetis alpinus.

Approaches: Extensive spatially and temporally replicated field surveys, combined with population genetics and laboratory assays of thermal tolerance (CTmax).

Key findings to date:

Our recent data (ongoing PhD thesis work of Marie Leys) indicates extensive cryptic genetic variation within B. alpinus within and among Swiss catchments. In particular, two major lineages (likely cryptic species) occur in sympatry but differ in life-cycle (mutlivoltine vs. univoltine), population genetic variation and extent of variation in thermal tolerance (CTmax).

People

Publications

Finn, D. S.; Räsänen, K.; Robinson, C. T. (2010) Physical and biological changes to a lengthening stream gradient following a decade of rapid glacial recession, Global Change Biology, 16(12), 3314-3326, doi:10.1111/j.1365-2486.2009.02160.x, Institutional Repository

Leys M*, Keller I, Räsänen K, Robinson C. Distribution and population genetic variation of cryptic species of the Alpine mayfly Baetis alpinus (Ephemeroptera: Baetidae) in the Central Alps. Submitted (in review).

Related student projects

Ph.D. theses

Marie Leys. (Ongoing) Eco-evolutionary responses of an alpine mayfly (Baetis alpinus) to glacial retreat: insight from cryptic species. D-USYS, ETH-Zurich, Switzerland.

M.Sc. theses

Philipp Ramsauer (2015) Spatio-temporal and thermal limit differences in two cryptic lineages of Baetis alpinus. D-BIOL, ETH-Zurich, Switzerland.

Linn Sgier (2012) Parasitism, melanism and immune parameters in alpine chironomid midges. Univ. of Zurich, Switzerland.