Faculty of Biology - Evolutionary Biology
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Dr. Steven Ramm

Department of Evolutionary Biology
Morgenbreede 45, 33615 Bielefeld
Office: VHF-215
Phone: +49 (0)521 106 2719
email: steven.ramm"at"uni-bielefeld.de
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Current projects

The evolutionary ecology of spermatogenesis

Evolutionary biologists have long been interested in the effects of sperm competition on the evolution of relative testis size, because of its obvious effect on male sperm production capacity. However, sperm competition likely affects many other aspects of sperm production beyond testis size, and our understanding of the relationships between different sperm production parameters is rudimentary at best. A major motivation of my current research programme is therefore to understand in what ways and under what circumstances males can vary sperm production independently of testis size; how phenotypic plasticity in sperm production is achieved; and to test for genetic constraints on the evolution of sperm traits.

The functional and evolutionary genetics of seminal fluid

I have a long-standing interest in the function and rapid evolution of the other major aspect of the male ejaculate, seminal fluid proteins, stemming from my earlier research on mammals, and from current projects investigating seminal fluid-mediated effects in flatworms and snails. In flatworms, we have recently defined variation in the seminal fluid transcriptome as a major component of male allocation. We are now examining how the knockdown of specific seminal fluid proteins affects fitness through physiological and behavioural manipulation of mating partners.

Evolutionary transitions between outcrossing and selfing

Where precisely a hermaphroditic species resides on the outcrossing-to-selfing spectrum has profound consequences for micro- and macro-evolutionary processes, making the study of plasticity and transitions in reproductive mode a key question in evolutionary biology. However, although well-studied in plants, the causes and consequences of regular selfing in hermaphroditic animals are comparatively much less well explored, and we currently lack good model systems amenable to both field and laboratory studies. We are currently developing multiple Macrostomum species as models for studying selfing and its evolutionary consequences, having found substantial variation in mating systems within the genus ranging from obligate outcrossing to mixed mating or even preferential selfing.

Fertility under climate change

How animals cope with systematically changing and more variable environmental conditions is a key concern under climate change. A major question is how climate change will impact fertility, and the knock-on consequences this will have for population viability and biodiversity. One mechanism that potentially allows organisms to deal with variability in environmental conditions is phenotypic plasticity, whereby a single genotype can produce different phenotypes suited to different environments. On longer timescales, local adaptation may lead to a permanent shift in relevant reproductive traits and restore full fertility. We have begun developing Macrostomumas a potentially highly suitable model organism to study these questions, and thereby hope to answer to what extent phenotypic plasticity and local adaptation can mitigate the negative consequences of climate change on animal fertility.  

Note for potential students/postdocs: If you’re interested in these or related questions and would like to discuss opportunities to join the lab, please get in touch!

For more information, see also ->macrostomum.wordpress.com