Tessera

Brent Emerson

@brentcemerson.bsky.social

Evolutionary biologist, sometimes faking it as an ecologist. Likes things with 6 or more legs. Professor @IPNA_CSIC. NZer in the Canary Islands.

71 Posts184 Follower 146 Folgt

Brian O'Meara @omearabrian.bsky.social · 12h ago

I wrote up my "it's like finding your hat preference" analogy for MCMC: brianomeara.info/posts/mcmc/ -- it helps students understand burnin, hot and cold chains, RJMCMC, etc. #Teaching #Bayes 🧢 👑 👒 🎩 🪖 🎓

$Hat Store 🧢 👑 👒 🎩 🪖 🎓 The analogy I’ve used in teaching is trying to figure out what kinds of hats you like. So you go into a hat store and put on a hat. Then, you wander around looking at hats one at a time. If you like a hat better than the current one, you put it on your head and put the other one down. If you like it worse, you compare how much worse it is to a random number: if it’s not worse than that, you put it on; otherwise you put it down and pick up another hat at random. In the meantime, a security camera takes a photo of you every so often and records the properties of the hat you’re wearing: kind of hat, color, propeller count, etc. This is basically an MCMC process, but for your hat preferences rather than for posterior probabilities for an evolutionary model. But it can illustrate some of the issues. If it all goes well, the fraction of the time you have hats with a certain property on your head is proportional to how much you like the hats. If you have a brown hat 40% of the time and a pink hat 10% of the time, your overall preference for brown is 40% out of all possible colors, and you like brown four times as much as you like pink. One can also pick up on correlations: you like brown hats in all styles but only like pink hats if they’re cowboy hats with sparkles. When you first walk into the store, the only hats you try on are those near the entrance. That might not reflect your preference: the ones at the front might all be varieties for the local sportsball team and you simply hate those. But they’re the only ones you can try at first, so you put them on. If we stopped the camera at that point, we would incorrectly think those are what you like. We have to wait until you’ve had time to wander around the store a bit to find the really awesome hats at the back. The photos we take where you’re only looking at hats because they are near where you came in are the burnin: we typically discard them.$

If you have an identical twin with the same preferences, you could start them in a separate part of the store and have the camera track each of you, keeping track of who is who (wear different shirts that day). At first the distribution of hats you choose are very different, accidents of where you started, but after a while the hats you and your twin have been wearing on average converge. This is known as running multiple chains. If only one of you could try a hat at a time, and the other has to wait (maybe you’re embarassed about your hair and only one of you can go into the changing room at a time), then this would double the amount of time required; if you can try on hats in parallel, then the time required doesn’t really increase. This is the same as running a process on one core or two cores (parallel processing).

You could get stuck: you could be in a pretty good display of cowboy hats but be separated from the really great propeller hats by racks of detested sportsball caps. Eventually you might wander over there, but it’ll require a lot of improbable choosing of bad hats to traverse the distance. But what you could do is get your identical twin a bit… uninhibited and send them to giddily wander the store. They still have your same preferences, but are more willing to put on bad hats. Eventually, they might get to the great part of the store and shout to you, “You HAVE to try these – they have propellers and lights!” This is running a heated chain. The camera still focuses just on you (since we care about what you prefer when sober) but the heated chain helps cross valleys with bad parameter values. There are often multiple heated chains, with different amounts of heating, but we just focus on the regular, “cold” chain.

How often should the camera take your picture? It feels natural to say “once for every hat” but hats are clumped: the hat nearest to the one you just put on your head is probably similar to it in many ways, and saving all these photos of you can take a lot of space. So in practice, we often have a sample frequency where we take a photo every 10th or 100th step. Also, since the hats we try on are correlated with each other (if we’re in the top hat section the next few hats are also likely to be top hats), it’s not like each one we try is an independent draw from all the ones in the store. There are ways to convert the number of correlated hats we’ve examined to the equivalent number of independent hats: this is known as the effective sample size or ESS (your software will typically tell you this number for each parameter: hats might clump more by style than color so your ESS for style might be smaller than color).

Hats aren’t the only model of head coverings you could like. There could be a wig store next door to the hat store, with a shared camera system. So you could try a hat, then the next thing is a great wig, then a mediocre hat, etc. The amount of time you spend in each store is proportional to how much time you like each head covering. Switching between models like this is reversible jump MCMC. But there’s a problem: within each store, the head coverings are arranged in clumps of similarity, but between the stores there might not be a relationship: maybe the purple hats are next to the purple wigs, but there are not a lot of parameters in common. If you’re in a part of one store you like, the nearest things in the other store might not be nearly as good, making switching harder. RJMCMC lets you compare models, but the issue of switching between the models often being rejected can result in difficulty mixing well between the stores.

Bumblebee Conservation Trust @bumblebeetrust.bsky.social · 6d ago

Is this bumblebee knitting?🧶 Female bumblebees collect pollen by brushing the fine grains out of their hair and into the pollen baskets on their hind legs. Still, how cute would it be to see bumblebee queens wrapped in tiny woolly jumpers as they settle down to hibernate over winter?

Brent Emerson @brentcemerson.bsky.social · 3w ago

This is a good read, provides a useful summary of the mechanisms that limit introgression, and offers new insights as to how hybrid speciation might be facilitated: Stabilizing selection generates selection against introgressed DNA www.journals.uchicago.edu/doi/10.1086/...

Stabilizing selection generates selection against introgressed DNA | The American Naturalist: Vol 0, No ja

journals.uchicago.edu

José Cerca @naturalselection.bsky.social · 4w ago

V happy about this one (@brentcemerson.bsky.social @biodiversitysmns.bsky.social @hernmoral.bsky.social)et al Species have survived on oceanic islands for Mya despite occupying small geographic areas, facing environmental calamities and having low Ne. We discuss this w/ a focus on conservation. 1/2

Nature Ecology & Evolution @natecoevo.nature.com · last mo.

Obituary: Robert Ricklefs (1943–2026) www.nature.com/articles/s41... Polymath ecologist whose research and textbooks integrating ecology and evolution have inspired generations of students. Free to read: rdcu.be/D33fLgYcv4Ba

Robert Ricklefs (1943–2026) - Nature Ecology & Evolution

Polymath ecologist whose research and textbooks integrating ecology and evolution have inspired generations of students.

nature.com

Brent Emerson @brentcemerson.bsky.social · last mo.

Tarentola delalandii from Tenerife emerging from behind a species of green gecko from New Zealand

Brent Emerson @brentcemerson.bsky.social · 2mo ago

Bea Leiderman @bealeiderman.bsky.social · 2mo ago

Bertholdia. One of my favorite moths. Every single one in the genus is a stunner. Those translucent bits! 🌿😜

A moth on a leaf. The wings are mostly brown with a big area lacking scales so it is translucent and the leaf shows through. The thorax has a red crest. There are four yellow spots along the thorax and black and yellow dashed lines along the posterior edge of the forewings.

@lourdeschamorro.bsky.social · 2mo ago

Weevils, weevils, weevils ... again this year! Online, free, and always exciting and illuminating :)

Jakob Jilg@weevil-see.bsky.social · 3mo ago

Spread the word! The Weevil Workers meetings consist of a series of presentations on any aspect of the study of weevils (Curculionoidea). Topics include systematics, faunistics, biogeography, evolution, biology, ecology, pests/biological control agents, etc. www.curculionoidea.org/weevil-worke...

Matt Bertone @bertonemyia.bsky.social · 2mo ago

That's not excessive. THIS is excessive:

Brent Emerson @brentcemerson.bsky.social · 2mo ago

Well this just got bumped up to the top of the reading list: "Chromosomal inversions accelerate genetic evolution and drive ecological speciation across an island gradient" doi.org/10.1073/pnas...

PNAS

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...

doi.org

Brent Emerson @brentcemerson.bsky.social · 2mo ago

Yet another reason why I will always love the UK www.bbc.com/news/article...

Count Binface receives over a quarter of votes in Clacton by-election

The dustbin themed candidate got 9,455 votes and came second to Nigel Farage

bbc.com

Harmit Singh Malik @harmitmalik.bsky.social · 4mo ago

😮 @danielgorelick.bsky.social @biologyopen.bsky.social www.nature.com/articles/d41...

Why paying peer reviewers works, according to a journal’s editor-in-chief

A biology journal that paid peer reviewers found that the approach cut the time to a first editorial decision by 85% and maintained high-quality reviews.

nature.com

Neil Gemmell @profgemmell.bsky.social · 4mo ago

Want to join our team? Check out this opportunity. Closes 30 June NZT.

Neil Gemmell@profgemmell.bsky.social · 5mo ago

🔬 Postdoctoral Opportunity – Mitochondrial Genome Editing We are recruiting a PDF to study how mitochondrial DNA mutations influence phenotype, metabolism, fertility, and ageing using mitochondrial base editing and Drosophila. Apply: otago.taleo.net/careersectio... 📩 neil.gemmell@otago.ac.nz

🔬 Postdoctoral Research Opportunity – Mitochondrial Genome Editing
We are recruiting a PDF to study how mitochondrial DNA mutations influence phenotype, metabolism, fertility, and ageing using mitochondrial base editing and Drosophila.
This is part of an international collaboration led by Neil Gemmell (University of Otago, NZ) with partners including Damian Dowling (Monash University,
AU), Alex Whitworth, and Michal Minczuk (University of Cambridge, UK).
📍 Based at the University of Otago, with collaboration and research visits in the UK and Australia.
💰 PDF Salary: ~NZ$92.35k/year fixed term for 2.5 years
📅 Deadline: 30 June 2026
If you know postdoctoral candidates interested in mitochondrial biology, genetics, evolution, or genome editing, please share.

Miguel A Gómez Serrano @gomezserrano-ma.bsky.social · 4mo ago

Durante las olas de calor las aves soportan mucho estrés. Esta hembra de Chorlitejo patinegro se moja el pecho para disipar su temperatura corporal y refrescar sus huevos, evitando así que alcancen una Tª letal para el embrión. Los moja y se levanta para dejar correr el aire.

Carl Quintanilla @carlquintanilla.bsky.social · 4mo ago

Dylan, on life in your 80’s, is incredible. @nytimes.com www.nytimes.com/2026/06/14/o...

Brent Emerson @brentcemerson.bsky.social · 4mo ago

www.ipna.csic.es/noticia/2026...

En memoria de Heriberto López Hernández | Instituto de Productos Naturales y Agrobiología

Dicen que lo que no se nombra no existe y, de ser así, Heriberto tenía un poder casi sobrenatural, porque la biodiversidad canaria está llena de seres vivos que hoy conocemos (y nombramos) gracias a s...

ipna.csic.es

Abejas de Canarias @abejasdecanarias.bsky.social · 5mo ago

Frente a las palmeras washingtonias del Padre Anchieta, otro modelo de jardinería canaria es posible. Es hora de cambiar el jardín ornamental por verdaderos ecosistemas urbanos que protejan nuestra biodiversidad polinizadoresdecanarias.org/hacia-un-nue...

Una toma de ángulo bajo mirando a través de un denso campo de flores de cabezón hacia un árbol drago (Dracaena draco) y varias palmeras canarias bajo un cielo azul despejado

Brent Emerson @brentcemerson.bsky.social · 5mo ago

It’s like finding out that one of your favourite singers has been lip syncing .

Reese Richardson@reeserichardson.bsky.social · 5mo ago

TL;DR: We've identified more than 100 cases of apparent manipulation in Thermo Fisher Scientific's antibody verification data. @sholtodavid.bsky.social @johanduchene.bsky.social reeserichardson.blog/2026/05/28/h...

Drhoz @drhoz.bsky.social · 5mo ago

drhoz.tumblr.com/post/8174720... #3735 - Feijoa sellowiana - Feijoa An iconic tree in New Zealand gardens, beloved for its fruit. Which is ironic, since it’s native to the highlands of Columbia, Brazil & Uraguay, & reached New Zealand via France then California. The flowers are pretty amazing too.

#3735 - Feijoa sellowiana - Feijoa

An iconic tree in New Zealand gardens, beloved for its fruit. Which is a bit ironic, since it's native to the highlands of Columbia, Brazil and Uraguay, and reached New Zealand via France then...

drhoz.tumblr.com

Dr Conrad P.D.T. Gillett 🇪🇺@coleopteriste.bsky.social · 5mo ago

Join the Name It To Save It campaign to bring taxonomy into the spotlight on Taxonomy Recognition Day on the 23rd of May! 1) Take a photo of any organism 2) Find its scientific name 3) Post the photo & name together with the hashtag #NameItToSaveIt

José Cerca @naturalselection.bsky.social · 6mo ago

Change my mind? (:

𝔸𝕞𝕓𝕖𝕣 𝔻𝕒𝕨𝕟 @amberdawn1116.bsky.social · 7mo ago

BREAKING: Huge win for the Endangered Species Act! Today’s ruling restores the Endangered Species Act to the status it held for decades before the *first* Trump administration attacked the ESA.

Federal Court Strikes Down President Trump’s Attacks Against Endangered Species Act, Restores Bedrock Environmental Law to Pre-Trump Status

Ruling derails future attempts to weaken law

earthjustice.org

Lars Chittka @larschittka.bsky.social · 7mo ago

The new James Cameron-produced NatGeo documentary "Secrets of the Bees" is out tomorrow. I hope it's good - our bees and team members are in it, but I haven't seen the final product yet. Here's a trailer.

@lourdeschamorro.bsky.social · 8mo ago

Very proud of this one: hbs.bishopmuseum.org/pubs-online/...

Cover of Annotated Catalog of Hawaiian Weevils

Harry McKillen @harrymckillen.com · 8mo ago

When I hear lovely birdsong in the morning, I remember this comic and laugh

A comic of a bird singing about somebody eating their babies, and a crow responding that they did and they'd do it again.

And below them, it is a man listening to a cd of their conversation entitled "relaxing bird sounds"

Brent Emerson @brentcemerson.bsky.social · 8mo ago

Some good advice for everyone, not just guys. No need to read the article, just listen to what William has to offer in the clip: bbc.com/news/article...

Prince William shares personal message on mental health and male suicide

Prince William has offered his advice to those struggling with their mental health, in a special Radio 1 panel discussion.

bbc.com

Javier Martín @txaverius.bsky.social · 8mo ago

Las diminutas semillas de un dragoncillo Antirrhinum miden apenas medio mm, pero a 20x muestran valles y cordilleras. Los detalles son unas 20 milésimas de milímetro. No deja de sorprenderme que algo tan diminuto lleve un embrión latente. Para enfocarlo todo tuve que apilar unas 300 imágenes.

Rafael Marcondes @rafamarcondes.bsky.social · 8mo ago

Woah @davetoews.bsky.social this has got to be the coolest and (IMHO) most important ornithology paper I've read in a good while. Already added it to my class this semester! doi.org/10.1093/orni...

Syntopic diet divergence inferred from metabarcoding in a pair of parulid warblers: Setophaga virens (Black-throated Green Warbler) and Seiurus aurocapilla (Ovenbird)

Abstract. The role of diet in driving ecological differences across the radiation of parulid wood warblers has been a topic of substantial debate. The infe

doi.org

Brent Emerson @brentcemerson.bsky.social · 8mo ago

Without the last three words this would be a more interesting, albeit troubling, news item www.bbc.com/news/article...

Julie Inman Grant: The woman tasked with kicking Australian kids off social media

After decades working in the private tech industry, Julia Inman Grant now finds herself on the other side.

bbc.com