Marie-Claire recently won, and just started, a prestigious University of California President’s Postdoctoral Fellowship! The Edwards Lab is lucky to have her. Dan is very excited to work with Marie-Claire and Prof. Carolin Frank to discover the impacts of sexual selection, the environment and disease on the evolution of sexual size dimorphism in Sceloporus occidentalis in California!
It has been a busy year for the Edwards Lab. This was my first time teaching, so things like updating the lab website have been lower on my priority list than keeping up with new course preparation. But we have some exciting news to share on a number of fronts, and some other exciting news on the horizon which I will post about later.
To start, Kinsey won a couple of large awards over the last semester. Firstly, she won a Southern California Edison Summer Fellowship worth ~$12,600 (including summer stipend and research money). Next she won the School of Natural Sciences Dean’s Distinguished Scholar Fellowship worth ~$18,000 to cover her Spring 2017 tuition and salary. Next up she won a prestigious National Geographic Waitt Grant providing her with $15,000 toward her dissertation research. Kinsey has been having a good year and we are all very proud of her achievements!
Indianna also won ~$1400 from the Associated Students of the University of California, Merced (ASUCM) Undergraduate Research Grants. This will allow her to travel to Greece to do field work with Kinsey this summer.
Laura also won ~$1600 travel award from the Environmental Systems Graduate Program to travel to the Evolution Conference this summer. She also got into the La Kretz Conservation Genomics Workshop and will be going to learn a whole bunch about undertaking conservation genomics projects!
Meg was also accepted into the Workshop on Quantitative Genetics at Friday Harbor and will be going to learn a whole bunch of new sweet skills this summer.
Justin was appointed the Environmental Systems, Ecology & Evolution (ESEE) Postdoctoral Fellow for 2017. He has been leading a bunch of meetings to promote interdisciplinary research in ESEE across campus, working with graduate students and postdocs to increase scholarly activities across UC Merced.
Kaithlen Zen Pacheco also joined our lab as an undergraduate researcher. We are very happy to have her along for the rid, and you can read a little more about Kaithlen on our People page.
Finally, myself and Kinsey wrote and won a Texas Ecolab Grant (~$14,000) to undertake research on Uta stansburiana and Urosaurus ornatus across western Texas. The lab is currently beginning a field trip to undertake this work.
That’s all for now….
It has been some time since I have posted any news. We had a VERY busy summer collecting lizards across the SW US. This semester brings us several new members to the lab. We welcome Megha, Laura and Marie-Claire to the lab! See our People page to meet our new folks.
Just out today, a big congratulations to Kinsey on her Rosemary Grant Award from The Society for the Study of Evolution. Such a proud advisor moment!
Justin just arrived as the Edwards Lab’s first postdoc a few weeks ago and has already started working hard on a range of different lizardy projects! I am really stoked Justin decided to come join the lab at UC Merced, and am looking forward to working with him over the next ~2 years. At the moment he is getting to know Merced, UC life and coming to terms with the much smaller town he now finds himself in (compared to New Orleans!). Welcome Justin!
Our paper describing a new species of giant Galápagos tortoise from Santa Cruz Island is now out in PLOS One. The new species, Chelonoidis donfaustoi, is named after Galápagos National Park Ranger Don Fausto Llerena (pictured above, image: Washington Tapia) – whose contributions to the captive rearing of Galápagos tortoises have essentially saved many species from extinction. He was also the primary carer of Lonesome George (the last remaining individual of Chelonoidis abingdoni who died June 24th 2012) during his time in captivity.
This paper formalizes what we have known for some time, that there were two species on Santa Cruz Island. These two species differ slightly in the shape of their carapace, but are extremely divergent genetically and represent separate colonizations of Santa Cruz island from different sources. They also occupy different distributions on Santa Cruz. Naming this species now allows for efforts by the Galápagos National Park, Galápagos Conservancy and others to conserve the new species, whose population consists of a few hundred individuals.
Distribution of the two species of tortoise on Santa Cruz (image: Nikos Poulakakis)
Determining the processes that drive speciation is a central question for the study of evolutionary biology, and research has generally focussed on adaptive speciation and speciation driven by sexual selection as independent processes. Adaptive evolution occurs when ecological selection shapes the evolution of traits for optimal fitness or performance in specific ecological contexts. Alternatively, sexual selection results from divergent selection of the traits that distinguish the best mates. Our new paper shows that in the Australian sand dragon complex (Ctenophorus maculatus and allied taxa) – both work together with geography to drive speciation repeatedly, and we suggest in a specific sequence.
(Thanks to Stewart Ford for the image above)
Figure 1: Distribution of lineages within the Ctenophorus maculatus species complex, including drawings of the dorsal surface (showing body proportions and dorsal markings) and visual social signals (i.e., ventral throat and chest pattern). Dorsal drawings are scaled to mean male snout-vent length (see C. m. dualis for scale bar). Extent of the arid zone is also shown (dotted line). Illustrations by Corrine Edwards.
In our new paper out today in The American Naturalist we studied how the evolution of adaptive and social signaling traits relates to geography in closely related lizards from the Australian arid zone (see our Publications page). We found that lineages diverged as heterogeneous arid habitats developed and expanded in Australia. As species invaded distinct ecological niches repeatedly and independently within arid regions, both adaptive and social signaling traits convergently evolved in response to ecological selection in these new habitats.
Figure 2: Time-calibrated species tree for the lineages within the Ctenophorus maculatus species complex. Posterior probabilities are displayed (above/below nodes), as are median clade divergence times (95% highest posterior density in brackets and bars). Scale bar is in millions of years before present. Boxes indicate significant niche divergence (above branches) and niche conservatism (below branches) for different niche axes. Also shown are the scaled dorsal views and visual social signals. Illustrations by Corrine Edwards.
But striking variation in visual social signaling traits not only resulted from adaptive evolution. Rather, geographic overlap between lineages explains greater variation in visual signals than ecological context. These results suggest that divergent visual signals reinforce the species boundaries initiated by adaptive evolution, driving dramatic variation in these traits. Such divergent signals allow avoidance of maladaptive hybridization between ecologically distinct species. Thus, we found that interactions between adaptive and social signal evolution during speciation depended on geographic context.
Figure 3 (part of 4 in paper): Proportions of variance independently explained by the environment (white), spatial overlap (dark gray), and the phylogenetic relationships among lineages (light gray) for visual (B) signaling traits. Circle overlap shows the proportion of variance explained by combinations of these factors, with unexplained variance listed outside circles.
This project represented years of work, and for me at least was challenging and exciting for a number of reasons. It changed the way I do science, the way I think about science and it pushed me to learn complex new analytical methods that I had never before used – as well as develop some novel tools. One of the exciting things about this paper was a novel way of graphing phylogenetic uncertainty onto disparity-through-time (DTT) plots (Harmon et al. 2003) that I developed. It allowed me to look at where phylogenetic uncertainty was concentrated in time and how that might affect the interpretation of trait DTT. The R code implementing this can be found here.
Figure 4 (part 3 in paper): Disparity-through-time (DTT) plots for visual signaling traits in the Ctenophorus maculatus species complex. The median observed relative subclade trait disparity is shown (black line; fig. 2), in addition to phylogenetic uncertainty from 1,000 posterior trees (red lines; aqua dotted line indicates median). The median (yellow dotted line) and 95% confidence interval from 1,000 simulations of the null Brownian motion model from each of 1,000 posterior trees (gray shading) is also shown. Time is in millions of years before present.
It also changed the way I viewed the review process for scientific publication. For me, the review process felt more like a collaboration between myself, my co-authors, the reviewers (MRE Symonds and one anonymous reviewer), the associate editor (SJ Steppen), and the editor-in-chief (JL Bronstein). All with the common goal of getting the best out of the research in the paper. It was the MOST constructive and enjoyable review-revise experience that I have ever had at a journal. Thank you The American Naturalist!
Another reason this paper was exciting was that I got to work with my sister, Corrine Edwards. She is an amazingly talented artist whose drawings (yes they are drawings, not photos!) appear throughout the paper.
This week Kinsey officially joined the Edwards Lab as its first graduate student! Dan is really excited that Kinsey decided to come work with us here at UC Merced, and she is looking forward to working with Kinsey on a range of different lizardy questions. For now Kinsey is getting settled into the lab, and gearing up to take some classes! Hopefully there will be more from Kinsey soon!