The best things in life take time, or in this case just over a full year in review and revision, but I am so excited to share our paper on path dependent evolution with the world. 

The summary of the paper below when it was a preprint is more exhaustive, but in brief we constructed the most complete chiton phylogeny to date, discovered that spatial vision evolved two different ways and FOUR times (two examples of convergent evolution nested within each other across the chiton tree). We then identified a morphological trait that is correlated with which type of eyes a given lineage can evolve, demonstrating path dependent evolution in a natural system! 

A fantastic article in Quanta magazine covers our work HERE! 

And a Perspective piece by Lauren Sumner-Rooney, a fellow chiton aficionado, is HERE! 

Here is a PDF of our paper!
*This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science on 1 March 2024, doi 10.1126/science.adg2689

 
​Happy to finally share our preprint on path dependent evolution in visual systems in chitons! Check it out here: https://doi.org/10.1101/2022.12.20.520810

Path dependence (contingency) is the idea that specific key events can push lineages down one or another path across evolutionary time. Kind of like skipping lunch leads to eating an earlier dinner, previous events can determine whether or not future events happen.

Chitons build iron teeth, but they also make TWO totally different types of eyes! Some chitons have hundreds of shell eyes, with a lens and retina, that look a lot like your camera-type eyes. But other chitons have thousands of eyespots, small receptors that work together like the facets of a fly's compound eye. BOTH types of eyes can provide spatial vision.

So what's going on, chitons? Why eyespots some times, and shell eyes other times? Why never both? We built the largest chiton phylogeny ever, and then mapped the two visual systems back to it. And we were SURPRISED.

There are TWO SEPARATE ORIGINS of shell eyes, AND there are TWO SEPARATE ORIGINS of eyespots. FOUR INDEPENDENT ORIGINS of vision! WHAT?!

What does this mean for evolution? Well, we hypothesized that the slits act as a critical junction, a key determining factor that forces lineages down one or another evolutionary path. This would mean that on a morphospace, we should see a GAP between eyespots and shell eyes, because the two rely on different morphological set ups. We plotted it, and sure enough we found a gap right between! 

Demonstrating path dependent evolution in a natural system requires a unique suite of circumstances, so much so that some scientists claimed it was impossible. Chitons are perfect, because even though different lineages gained different types of visual systems, they all live in really similar places, and have across their fossil record. That also meant we could time the evolution of eyes; one lineage of chitons gained eyespots in only 6 million years. For the record, that's FAST.

This was a really rewarding paper to write, especially because it doesn't seem like anybody noticed the slits-eyespots link before now! Never underestimate the power of some good old fashioned morphology, even alongside the latest and greatest 'omics. 

It was a wilder ride than anticipated, but I'm happy to share that our paper on the phylogenetic relationships of Pycnogonids (Sea Spiders) was accepted today in Polar Biology. The analyses for this paper began during downtime on the ship to Antarctica in 2020, and amazing first author Jessica Zehnfennig got mitochondrial genomes from some very tiny sea spider specimens that I pulled from Antarctic mud! We spent a lot of time squinting at mitochondrial gene orders, but the result was surprising. We found a very different topology from some previous studies, specifically changing places of Nymphonidae (smaller, cute spiders) and Colossendeidae (the gigantic but also cute spiders). Working with Jess to build robust phylogenies was a joy, and I am excited to see what the rest of her PhD work brings!

Check out our paper HERE!

We just finished a fantastic week of field work in Puerto Rico! The Oakley Lab (me, Todd, and our amazing undergrad Stuart) worked in collaboration with Anders Garm and Jan Bilecki to gather Tripedelia jellyfish. We also recorded some incredible ostracod signals with WALLE, and even collected some of the elusive Jimmorinia to bring home! It was a beautiful place to see, and the boat drivers at the marine lab were THE BEST. We didn't miss a trap the entire trip, even collecting them at night.  

Keep your fingers and tentacles crossed for a great Tripedelia genome to come soon!

Oh dear, old words are coming back! A huge undertaking, led by the amazing Marie Drabkova, assessed the phylogenetic positions of dicyemids and orthonectids, and SURPRISE, they came out together. I had the pleasure of generating transcriptomes from preserved dicyemids, which looked like tiny bits of lint floating in a sea of RNALater. We guessed at which little brown shrivels were the right ones, so getting the data back was a delight after a challenging extraction! 

Check out our paper here! 

When one chiton genome just isn't enough... sequence another! Happy to share our paper on the genome of Hanleya hanleyi, a lepidopleurid chiton with SO MANY REPEATS. Take a look HERE! 

We tackled this genome with a combination of nanopore and short-reads. Running the flow cells ourselves was a fun process, and benefitted a lot from the short-read eliminator kit from Circulomics. 

Seems like chitons enjoy expanding repeats as much as long crawls on the beach; Hanleya has more repetitive content (66%!) than any other molluscs sequenced to date. But this beautiful chiton offers new data from Lepidopleurids, the clade that falls sister to all other chitons.