Dr. habil. Sandra Bouwhuis
Institute of Avian Research
An der Vogelwarte 21
Tel.: +49 4421 9689 14
I am an evolutionary ecologist with a specific interest in the causes and consequences of within-individual change in life-history traits and between-individual variation in life-history strategies. I mostly conduct analyses on long- term individual-based data sets collected in wild populations, and have so far had the pleasure to work on great tits (Parus major), pre- industrial humans (Homo sapiens) and common terns (Sterna hirundo).
My current work focuses on the common tern. The common tern is a Nearctic and Palearctic colonially breeding and migratory seabird. The data we collect come from a long-term study population located in the Banter See at Wilhelmshaven on the German North Sea coast. In 1992, 101 adult birds were caught and marked with transponders, and since 1992 all locally hatched birds have similarly been marked with a transponder shortly prior to fledging. The colony site consists of 6 concrete islands, each of which measures 10 by 5 meter and is surrounded by a 60 cm wall. The walls support 44 platforms for terns to land on, and each platform is equipped with an antenna which reads transponder codes to record the presence of all transponder-marked individuals. During incubation, which is shared between partners, additional antennae are placed at each nest for 1–2 days to identify breeding individuals. Combined with 3-times-weekly checks of nests to record reproductive parameters and to mark offspring, these methods enable the systematic and remote documentation of individual presence and reproductive performance at the colony. Once birds have established themselves as Banter See breeders, their re-sighting probability is almost 100% and their local survival probability is 80-90%, such that we can collect data over long individual life cycles. Since 1992, the number of breeding pairs has ranged between 90 and 715.
Making use of the long-term data set, I have found sex-specific pathways of parental age effects on offspring lifetime reproductive success: recruited sons from older fathers suffer from a reduced lifespan, while recruited daughters from older mothers suffer from reduced reproductive performance throughout life (Bouwhuis et al. 2015 Evolution). The latter effect may (partly) be explained by daughters from older mothers fledging with a reduced body mass and remaining a low body mass throughout life. With a team of students I now investigate potential underlying mechanisms and study sex-specific offspring food intake, growth and telomere length in relation to parental age and sex. In addition, in collaboration with Dr. Miriam Liedvogel, I have been awarded a grant by the Max Planck Institute to start work on the epigenetics of the observed parental age effects. Together with Dr. Britta Meyer, we will use repeated blood samples of parents, and their offspring produced at different ages, to assess DNA methylation status and answer the following questions:
* do adult DNA methylation patterns change with age within individual common terns and does any within-individual change in adult DNA methylation pattern depend on age-at-first-sampling or sex?
* do offspring DNA methylation patterns resemble those of (one of) their parent(s) and do (sex-specific) offspring DNA methylation patterns predict offspring development or survival?
In addition, in a few years, we will be able to also assess whether adult DNA methylation status is predictive of remaining lifespan and whether offspring DNA methylation status is predictive of the probability to recruit to the breeding population. Follow-up studies of recruits throughout their subsequent reproductive lifespan are of course within reach as well!
Working with Dr. Oscar Vedder, I am investigating whether telomere length or dynamics can be used as a proxy of somatic state and therefore can be used to combine analyses of life-history data with contemporary data in order to understand the physiological processes underlying within-individual change in life-history traits and between-individual variation in life-history strategies. Moreover, we analyse how both ecological (e.g. the early-life environment) and evolutionary factors (e.g. conflicting selection on parents and offspring) explain between-individual variation (or its absence) in life histories. In addition to using the correlative tern data, we have recently acquired replicated lines of Japanese quail artificially selected for high and low investment in reproduction. Also in collaboration with Dr. Barbara Tschirren, we’ll use these to experimentally investigate under which circumstances late-life consequences of poor developmental conditions can evolve, and how such consequences are regulated.
In collaboration with my first own PhD student, Nathalie Kürten, as well as Dr. Heiko Schmaljohann and Dr. Jacob González-Solís, I have started to extend our view of the common tern beyond the breeding season and now study migration of the Banter See breeders in relation to (natal) environmental variation and the phenotypic and genetic characteristics of the birds. In 2016, we tagged 24 adults and their 24 first-hatched chicks. In 2017, we retrapped 22 of the adults, re-equipped them with a new geolocator and also tagged 14 new adults. Now, in 2018, we are again successfully re-trapping these birds and re-equipping them with a geolocator, while again also adding new birds to our sample. Finally, the first geolocator chick prospected in 2017, and we can't wait for him to start his reproductive life so we can retrap him and see where he spent his juvenile life stage! May many of his peers return to the colony to prospect or breed as well!
Working with Dr. Coraline Bichet, I am extending the current projects by means of a common tern microsattelite project facilitated by Prof. Michael Wink. In addition, and in collaboration with Dr. Kevin Matson, we are currently collecting longitudinal data on mercury pollution and various immune parameters. Finally, we have started to photograph the eggs of known parents and are planning to turn this into another longitudinal project.
If you are interested in joining us in any of these projects, or have an interesting project to add, please get in touch. There are several grant opportunities that I would be happy to explore with you!