Sean A. S. Anderson 🍉

Congratulations to Joe Felsenstein on being awarded the 2026 Mendel Medal!

How are Pacific NW mountain birds responding to climate change?

I got up at 4:00 am for a month to find out.

but first the backstory, or "how I spent seven years telling everyone this project wasn't possible"

new paper here:
esajournals.onlinelibrary.wiley.com/doi/full/10....

Testing the thermal physiology, habitat and competition hypotheses for elevational range limits in four tropical songbirds | Proceedings of the Royal Society B: Biological Sciences Restricted elevational ranges are common across tropical montane species, but the mechanisms generating and maintaining these patterns remain poorly resolved. A long-standing hypothesis is that specia...

Check out our new paper in @royalsociety.org testing mechanisms behind elevational range restriction in tropical montane songbirds! ⛰️🦜🌳

Backstory: when i first visited Central America in the early 2010's i was struck with elevational ranges of birds..

royalsocietypublishing.org/doi/10.1098/...

And honestly, we all should aspire to and hope for more whimsy in our lives—it’s bleak out there

This is excellent

This obit of Watson is *amazing*.

It's irritating that they describe the effects of his racism as limited to causing controversy within science and reputational consequences for himself rather than giving an immeasurable boost, false veneer of legitimacy, and idiot-friendly prestige to modern scientific racism and eugenics.

As Mamdani nears victory, Democrats worry about national fallout The progressive candidate is on the cusp of a historic mayoral win. And that's adding to unease among Democrats looking for a way back to national power.

The framing of this is hilarious: Democrats deeply worried about the repercussions of a victory
www.msnbc.com/msnbc/news/m...

Anyway, doing great this morning

There’s not one more cruel, sadistic sports town anywhere. These teams excel at tempting you into hope. They drag you into deep water and drown you

I really thought I’d seen it all in terms of the most depressing, soul-crushing, eye-watering failure that Toronto sports has to offer, but somehow I was wrong

YES, SAVAGE!!!

Loss of macroevolutionary species fitness explains the rise and fall of clades - Nature Ecology & Evolution The interplay between speciation and extinction rates shapes clade diversity dynamics. Using a novel phylogenetic model that includes living and fossil lineages, the authors estimate speciation and ex...

Excited to share our new paper where we find that the rise, decline and fall of clades is not explained by the usual suspects (diversity-dependence, ecological opportunities) but rather by species' insidious loss of macroevolutionary fitness: www.nature.com/articles/s41... 1/3

It’s the green light on the dock across the bay?

They don’t deserve it is what I’m saying

The people in the apartment across the street from me have had their patio fan running continuously since January. Never seen them out there. Need to learn flashlight Morse code.

My colleague @jameststroud.bsky.social is a fantastic scientist and an even better guy -- congrats James on this richly deserved recognition and research support!!

Speciation Through the Lens of Population Dynamics: A Theoretical Primer on How Small and Large Populations Diverge Population size and dynamics fundamentally shape speciation by influencing genetic drift, founder events, and adaptive potential. Small populations may speciate rapidly due to stronger drift, whereas...

New review out! With students in my lab, we explore how population size shapes speciation—from drift in small populations to selection in large ones. Do small or large populations speciate faster? The answer is more nuanced than you might think.
esj-journals.onlinelibrary.wiley.com/doi/full/10....

Human-mediated land-use and climate change occur simultaneously, but how do they interact to shape adaptive dynamics? Super excited to share the first paper from the Kreiner lab, led by postdoc extraordinaire @rpineau.bsky.social

Thanks Jesper!

We hope you find this paper and the phylopairs package useful. Please have a read and get in touch if questions arise.

phylopairs: Comparative Analyses of Lineage-Pair Traits Facilitates the testing of causal relationships among lineage-pair traits in a phylogenetically informed context. Lineage-pair traits are characters that are defined for pairs of lineages instead of i...

Finally, a major impediment to the comp analysis of LP traits has been a lack of ready-made tools for empiricists to deploy. To help on this front, I created the R package 'phylopairs', a tool entirely devoted to working with LP traits. Phylopairs encodes our method plus previous approaches

The paper goes into much more detail on our approach and a few other methods that have been used in the past. We also provide the first test of the performance of any of the methods that have been used in comparative analyses of LP traits, some of which turn out to be potentially problematic

A major breakthrough for us was stumbling across Isserlis' theorem, which allows us to write the expected covariance among lineage-pairs in terms of the expected covariance among the component lineages (which we know if we have a tree).

From this basic assumption, we can derive metrics for the expected covariance among PAIRS of lineages. In effect, we convert a standard phylogenetic covariance matrix into a lineage-pair covariance matrix -- and we can use this to account for non-independence in comp. studies of lineage-pair traits

Our basis for these expectations is the idea that C and D are similar in some trait(s) due to shared evolutionary history, and this affects the value of the LP traits measured for AC and AD. That is, we assume phylogenetic signal in some underlying character that affects the LP trait we care about

Our answer is that, yes, as a NULL expect'n, AC and AD should be more similar to each other in an LP trait than either is to AB. E.g., if A has strong postzygotic RI w/ species C, then it prob. does so w/ D also. If A competes strongly for food w/ C, it prob does so w/ D as well (as a null expect'n)

We start by considering the following tree. Six lineage-pairs can be derived from this tree, three of which are AB, AC, and AD. We ask: of those three pairs, would we expect any two to be more similar to each other than either is to the third in some continuous lineage-pair trait?

In this paper, we work to develop such models and show that they produce a ‘lineage-pair covariance matrix’, an object that can be used to account for non-independence in downstream analyses in the same that way a ‘phylogenetic covariance matrix’ is used in comparative studies of species’ traits

Like the traits of related species, the traits of related lineage pairs are non-independent. Unlike for the traits of species, we currently lack models for the structure of non-independence of lineage-pair traits, which makes it unclear how to account for their underlying covariance.