Evolutionary change in aquatic invertebrates


Christine Ewers, PhD

(formerly Ewers-Saucedo)

About me

I have always been fascinated by change. In marine and aquatic environments, changes are much harder to observe, and my work focuses on reconstructing these illusive but pervasive changes. Some of these changes are rapid and anthropogenic, others driven by "slow" nature itself. My approaches are interdisciplinary: I utilise phylogeographic and temporal genomic approaches in combination with field observations, morphology and experiments.

Change can be relatively fast, especially if the selective pressure is strong, as is the case in environmental gradients. In alien species and extinct populations, evolution may even be faster, and many of the potential changes would have occurred in the last two centuries. For these contemporary changes, I am taking advantage of natural history collections, which offer largely untapped time series. Change can also be comparatively slow, observable as differences between species. I study such large-scale patterns of adaptive evolution in a diversity of systems and traits, focused on life history and reproduction.

Rapid evolution of alien species

Alien or non-native species represent unparalleled evolutionary experiments. They allow us to investigate how species deal with rapid change, i.e. how alien species deal with their novel habitat. At the same time, we can learn much about colonisation and the very beginnings of speciation. At present, I am working with crabs as a group of very successful invaders, specifically the Chinese mitten crab.

Extinction & evolution

While many species extinctions are human-mediated, the mechanisms underlying especially marine and aquatic extinctions are not well understood. I utilise historical specimens from natural history collections to study the evolutionary properties preceding decline and extinction. My current focus is on the European oyster, which went extinct a century ago in the Wadden Sea.

Evolution across environmental gradients

Environmental change drives evolution, but how adaptive and neutral processes interact to shape the current distribution of species is not well understood. Using the relatively young (ca. 10,000y) North Sea - Baltic Sea region with its strong salinity gradient as a natural experiment, I test how and if marine invertebrates have adapted to the brackish water conditions.

Large-scale patterns of adaptive evolution

Comparative methods are a powerful tool to infer large-scale adaptive patterns. They help us understand the general rules that have shaped biodiversity. I utilise comparative methods in many contexts, but my longstanding interests is life history and reproductive evolution in crustaceans.