Near-Peer seminar: land crab evolution
Our summer seminars launched this week with a talk about travel to tropical islands. But it was more than just a travelogue: Population Biology graduate student Victoria Watson-Zink gave a sparkling talk to UC Davis summer research students in which she outlined her dissertation research. In The Hitchhiker's Guide to Terrestriality: Exploring Life-History Evolution in Land Crabs, Watson-Zink described how she uses similarities in the DNA of land crab species to study their evolution from a marine ancestor.
Watson-Zink explained that because all life began in the sea, many branches of the tree of life had to overcome the challenges created by moving from a marine environment to a terrestrial one. These include developing new ways to breathe, thermoregulate, and deal with salt balance and waste excretion. Focusing on one group of organisms -- land crabs -- could yield information into the underlying genetic mechanisms that might lend broader insights into the transition from marine to terrestrial habitats.
The students in the audience, all of whom conduct virtual summer research with UC Davis faculty through the EERREC REU, research programs funded by UC Davis, or the UC-HBCU Initiative NUTGAP and PABGAP programs, asked insightful and probing questions throughout and gained knowledge about crab evolution, entering graduate study, and funding science.
And they learned something about resilience and collaboration, too. The 2020 pandemic prevented Watson-Zink from returning to the South Pacific to conduct another field study. Instead, the third chapter of her dissertation will focus on color variations in a threatened species, the coconut crab Birgus latro, across its range, which spans the Indian Ocean and Western Pacific. Scientists from across this region are assisting Watson-Zink by sending reports of color variations.
Rick Grosberg, Watson-Zink's major professor, commented, "Vicky is one of those truly exceptional students with the intelligence, talent, focus, vision, and boldness to revolutionize an emerging discipline that examines the genetic changes underlying one of the most important and challenging shifts in the history of life on this planet, namely the repeated evolution of transitions from the sea to land. Like the crabs she passionately loves, Vicky’s life journey has posed many seemingly unsurmountable obstacles, but here she is, destined to transform the future of discovery not only through her own research innovation, but through her exceptional collaborative, mentoring, and community-building skills."
Watson-Zink, an NSF GRFP Fellow who currently serves as the UC Davis College of Biological Sciences' Graduate Student Assistant to the Dean for Diversity and Inclusion, will finish her research in the coming academic year and begin a position as a Stanford Science Fellow to extend her work on the biology of land crabs.
Thank you, Vicky, for a wonderful seminar.
p.s. postscript, 9 July: Congratulations, @origamicrab!
p.p.s. aaaaaand....it's out!
Watson-Zink, V.M. 2021. Making the grade: Physiological adaptations to terrestrial environments in decapod crabs. https://doi.org/10.1016/j.asd.2021.101089
Abstract: All extant macroscopic terrestrial diversity has evolved from the ancestors of a small group of successful terrestrial colonizers, but in a few lineages this transition has independently occurred multiple times in spite of the significant functional challenges it presents. Decapod crabs have transitioned from marine to terrestrial environments at least ten times, occupy diverse habitats, and display varying degrees of terrestriality. Previous attempts to categorize land crab diversity relied on single traits, did not explicitly distinguish between brachyuran and anomuran lineages, and did not separate lineages that colonized land via freshwater or marine environments. As a result, critical phylogenetic and ecological constraints were missing from these earlier classifications. In this paper, I reclassify terrestriality in the land crabs by designating four transition pathways that reflect deep phylogenetic relationships between the two decapod crab infraorders and the route-specific nature of this transition. I then describe the adaptive traits that evolved in response to six primary terrestrial selective challenges. I conclude by proposing six grades of terrestriality in this system that describe observable trait-by-environment associations, and propose studies that can test the hypothetical sequence of trait evolution and the nature of convergence in the land crabs using phylogenetic and transcriptomic tools.