Will H. Ryan, PhD

Variation in the temperature dependence of fission across the latitudinal range of the sea anemone, Diadumene lineata 

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Diadumene lineata is a small, intertidal sea anemone with a prolific habit of asexual reproduction. Previous work on this species has shown that the rate at which it divides strongly depends on water temperature, with warmer water stimulating more frequent divisions. 

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The abiotic environment that an individual experiences can be very different from one end of the species range to the other. It is reasonable to expect that a sea anemone living on the coast of Massachusetts, where summers are mild and winters sometimes mean weeks encased in ice, will have different adaptations to temperature than a sea anemone living on the Gulf Coast of Florida, where mild winters are traded for months of summer heat. Populations of Diadumene lineata thrive all along this latitudinal range, but act very differently in different places. In the south, they clone themselves prolifically, whereas in the center and north of their range, they divide less and stay larger. Being larger, they tend to produce more eggs during the summer reproductive months (Ryan 2018, Am Nat)

 

Much of my work thus far has been showing how temperature, body size, fission rate and gametogenesis interact to set population specific rates of investment in clonal growth and gametes.  But, the presence of environmentally-mediated tradeoffs between investing in clonal growth versus gametes make this an exciting system to use in exploring the factors that push populations to invest more or less in sex.  

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Seasonal and size dependent patterns of gametogenesis in Diadumene lineata

Although D. lineata is one of the few sea anemones that has been studied by many authors, very little has been described about the sexual life of this species. Almost nothing was known about patterns of gametogensis outside of its probable native range in Asia. Knowing when and why an organisms makes gametes is important to addressing almost any other question about its life history. So, for nearly four years I  carefully dissected thousands of individuals from across the species US east coast range to understand when gametes are made (seasonally), what kinds of gametes are made (eggs or sperm) and what determines how many gametes are made (hint: its got a lot to do with body size).  (Ryan 2017)

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Modeling the factors stabilizing balanced reproductive investment

Species that invest in asexual reproduction usually also engage in sexual reproduction , at least occasionally. How much energy an organism invests in these two, often conflicting processes has complicated consequences for individual fitness. I am using a simulation modeling approach, using the biology of my anemone as a muse, to pick apart the direct and indirect selective forces that influence the evolution of reproductive investment strategy (Ryan 2017).

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Comparing latitudinal patterns in life history strategy between the native (Japan) and exotic (US) coastlines

Through the NSF's EAPSI program and the generosity of many Japanese hosts, I had the opportunity to spend 10 weeks exploring my sea anemone on part of its home turf. I was interested to answer several questions about how the effects of temperature and other factors correlated with changes in latitude on the body size and gametogenesis of this species differed between the native and invaded ranges. I was able to travel from Itsukushima, Hiroshima to Akkeshi, Hokkaido, collecting samples, counting eggs and measuring little bodies. Paired with comparable sampling done across the same latitudinal range in the US, common garden experiments and field observations are adding all sorts of interesting pieces to the puzzle. I also replicated a survey of color morphs of the species in around Tanabe Bay, Wakayama done in the 1930's by Tohru Uchida (Ryan and Kubota 2016).

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