Farewell to Aniqa and Sun!

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Aniqa and Sun both had their last days in the lab in July — we’re sad about them leaving and also excited about their new adventures!

Aniqa worked as an undergrad researcher in the lab beginning in Fall 2019 (in the before times!), working particularly closely with Kristel. (Fun fact: Aniqa also worked on fixing captions on Intro Bio videos during the 2020-2021 school year!) Aniqa will be starting an MS program in Physiology here at Michigan this fall.

Sun began as a postdoc in the lab in 2021, and to say that he hit the ground running would be an understatement! Sun did lots of fieldwork (and took gorgeous photos of our lakes!) and also carried out a series of lab experiments. Sun is now moving back to Taiwan where he will begin a faculty position at National Taiwan University. Check out his website!

A beautiful sunrise at Whitmore Lake (photo credit: Syuan-Jyun Sun)

Kate’s new paper is out in Evolutionary Ecology!

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One of Kate McLean’s dissertation chapters just appeared in Evolutionary Ecology! The paper explored the roles of sexual recombination and temporal gene flow (via the egg bank) in maintaining host resistance and genetic diversity. Many studies (including some from our lab) have focused on how host resistance changes within a growing season. Others have looked at long term trends in resistance evolution across many years. Kate’s study looks at the neglected middle ground: how the resistance distribution that exists at the end of one growing season changes by the start of the next growing season as a result of sexual recombination and temporal gene flow from the egg bank.

To study this, Kate and colleagues tracked resistance to Metschnikowia and genetic diversity in Daphnia dentifera in two lakes. This involved collecting sexual females in the autumn, getting them to release their resting eggs, and hatching those resting eggs. Comparing the resistance phenotypes of the moms vs. the hatchlings let us uncover the effect of sexual recombination on resistance, and also to estimate the heritability of resistance. In addition, we sampled the populations early the following spring to characterize the populations shortly after they were reestablished from the egg bank. Since the hatchlings told us about what had gone in to the egg bank the prior year, comparing them with the spring population allowed us to determine the effect of temporal gene flow via the egg bank. Resistance was quantified using infection assays, and genetic diversity was quantified using microsatellites; the diversity component of this project was the foundation of the undergraduate Honors Thesis of Haniyeh Zamani, who is a coauthor on the study.

Because we know that resistance and fecundity trade off in the Daphnia dentiferaMetschnikowia system, we expected that populations would evolve toward higher susceptibility (due to its fecundity advantages) unless an epidemic had recently selected for resistance. Moreover, if an epidemic did occur, we expected resistance to increase temporarily but that sexual recombination and temporal gene flow would then shift the population back towards susceptibility. This is not what we found! Instead, susceptibility was the transient state, with recombination and gene flow restoring and/or maintaining high resistance.

For genetic diversity, we expected that fall offspring would show greater genotypic diversity than their parents due to the effects of sexual recombination; this was observed in one lake (Hackberry) but not in the other (Midland), where genotypic diversity of parents was already very high. We also predicted that the egg bank clones would have higher diversity than the fall offspring, since we anticipated hatching of individuals produced across multiple years; again, this was observed in Hackberry but not in Midland.

In short, sexual recombination and temporal gene flow are both important players in determining inter-annual variation in host resistance in this study system, but not always in the ways we predicted!

In addition to lead author Kate McLean, the authors on this paper are former Duffy Lab grad student Camden Gowler, lab postdoc Marcin Dziuba, former lab undergrad Haniyeh Zamani, long term collaborator Spencer Hall, and Meghan.

Congrats to Kate on her new publication!

New lab group photo

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We didn’t manage to get everyone, but we did get everyone who was there looking at the camera, so we’ll call it a win!

Back row, left to right: Marcin, Noah, Siobhan, Kira, Libby, Kate
Kneeling, left to right: Sun, Meghan, Kristel, Aniqa
Summer 2022 folks who are not pictured: Kris, Logan, Michelle, Paige, Teresa

The 2022 field season has begun!

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Our field season has begun! And it turns out the weather gets better every day of field season — this trend will continue through November, right?

Day 1: We started sampling on June 1st which was, unfortunately, a rainy day, but that didn’t stop the field crew!

Siobhan heading out to the deep spot on Crooked (W) in the rain.

Day 2: The weather was somewhat nicer — no rain, but still cloudy.

Teresa collecting a water sample with the van Dorn bottle.
Sun collecting a plankton tow.

Day 3:

Beautiful weather for Noah’s first day in the field!

Noah giving a thumbs up to the beautiful weather for his first day in the field!

We’re looking forward to field season, even if the weather isn’t always as nice as it was on day 3!

Kristel receives department JEDI award!

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Congratulations to Kristel, one of two recipients of this year’s departmental Justice, Equity, Diversity, and Inclusion (JEDI) award! Kristel received the award specifically for her work on Feria de Ciencias, which is an annual event that engages local primary school students about science in Spanish. Kristel has been a principal organizer of this, working with the En Nuestra Lengua after school program (where Kristel also volunteers!) to bring it to fruition.

In addition to her work with Feria de Ciencias, Kristel has been highly involved in multiple other JEDI efforts while in grad school. This has included: department service focused on JEDI issues (including serving on the department’s Diversity Committee), helping to organize the annual BioBlitz in the Detroit area, helping with EcoDia (an event held in Mexico for children ages 5-12 from rural communities in Chiapas), and via thoughtful, supportive mentoring of students from underrepresented groups.

Kristel is highly deserving of this award and we’re very happy she is receiving this recognition! Congrats, Kristel!

Stations at Feria de Ciencias (photo courtesy of Kristel Sánchez)

Kristel smelling ants with an EcoDia participant!

New article on virulence evolution!

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We have a new article exploring virulence evolution during a naturally occurring parasite outbreak! This paper includes work led by Camden Gowler as part of his dissertation work, as well as Haley Essington’s undergraduate honors thesis project. The study tracked an outbreak of the virulent bacterial parasite Pasteuria ramosa in a lake population; this was a large outbreak, with ~40% of the population being infected at the peak of the epidemic. Not surprisingly, considering the size of the outbreak of this sterilizing parasite, host density declined precipitously during the epidemic.

In addition to monitoring the epidemiological dynamics, Camden collected host and parasite from different time points during the outbreak. Camden and Haley then led a study that exposed Daphnia clones to parasites isolated at different time points. We did not detect any significant changes in host resistance or parasite infectivity. We also did not find evidence of shifts in two measures of parasite virulence, host lifespan and number of clutches produced by hosts. To our surprise, the parasite evolved over the course of the epidemic to produce significantly fewer spores in infected hosts. You can read more about this in the article which is now available online at Evolutionary Ecology; it’s open access, so free for all to read!

lake with plants in foreground and trees in distance
A photo of Little Appleton Lake, which was the focus of the study in the new Gowler et al. Evolutionary Ecology paper. Photo credit: Libby Davenport

Libby is now a PhD Candidate!

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Congratulations to Libby on completing her qualifying exams! During Fall semester, she gave a presentation about her research, wrote a dissertation proposal, and took her oral exams — while also collecting and filtering almost 1000 water samples during field season! Libby is now a PhD candidate and is looking forward to analyzing all those samples and trying out some winter sports.

Libby out sampling (photo credit: Siobhan Calhoun)