Ethan Gyllenhaal
@ethanofthegulls.bsky.social
NSF Postdoc at Texas Tech and Cornell studying the evolution of south Pacific birds with genomics, museums, and simulations. Birder. SLiM enjoyer. He/him.
Look forward to more about Solomon Island phylogeography in the future, but in the mean time, @lukemusher.bsky.social and I have a pre-print that highlights how a similar phenomenon can occur on continents (with bias in both topology and branch lengths): doi.org/10.1101/2025...
November 21, 2025 at 6:29 PM
Look forward to more about Solomon Island phylogeography in the future, but in the mean time, @lukemusher.bsky.social and I have a pre-print that highlights how a similar phenomenon can occur on continents (with bias in both topology and branch lengths): doi.org/10.1101/2025...
One big question that still lingers is when this gene flow occurs. Theory suggests that dispersal start high and declines over time in island birds, but it is hard to observe modern inter-island migration. But we found a lucky breadcrumb: an F1 inter-island hybrid (formerly intergrade, now split).
November 21, 2025 at 6:29 PM
One big question that still lingers is when this gene flow occurs. Theory suggests that dispersal start high and declines over time in island birds, but it is hard to observe modern inter-island migration. But we found a lucky breadcrumb: an F1 inter-island hybrid (formerly intergrade, now split).
Although we have some evidence suggesting biased inference in this system, we wanted to generalize these findings using coalescent simulations with gene flow based on island biogeographic theory. For a wide parameter space, the Makira-sister pattern dominated regardless of the split history.
November 21, 2025 at 6:29 PM
Although we have some evidence suggesting biased inference in this system, we wanted to generalize these findings using coalescent simulations with gene flow based on island biogeographic theory. For a wide parameter space, the Makira-sister pattern dominated regardless of the split history.
So what could explain the dominance of this topology? Well, it turns out the island most isolated from propagules is also most isolated from gene flow from the central Bukida group. This was both true in theory and with tests of gene flow.
November 21, 2025 at 6:29 PM
So what could explain the dominance of this topology? Well, it turns out the island most isolated from propagules is also most isolated from gene flow from the central Bukida group. This was both true in theory and with tests of gene flow.
Indeed, when we ran simulations of colonization history with SLiM, we found that only ~1% of simulations produced a colonization history consistent with this topology. Note that the GIF has very low population size/dispersal rate for visualization.
November 21, 2025 at 6:29 PM
Indeed, when we ran simulations of colonization history with SLiM, we found that only ~1% of simulations produced a colonization history consistent with this topology. Note that the GIF has very low population size/dispersal rate for visualization.
However, the island of Makira was most isolated from lineages moving between island from their source population to the west, but was also inferred as sister to all other populations. This was counter-intuitive as first, especially because the genus doesn't make it east of the Solomons.
November 21, 2025 at 6:29 PM
However, the island of Makira was most isolated from lineages moving between island from their source population to the west, but was also inferred as sister to all other populations. This was counter-intuitive as first, especially because the genus doesn't make it east of the Solomons.
Just out in Systematic Biology, we explore the role of gene flow in island phylogeography of the Solomons Black-and-white Monarch complex. doi.org/10.1093/sysb...
Up first, strong genetic structure between islands groups and weak (but present!) structure between Pleistocene-connected islands (🧵)
Up first, strong genetic structure between islands groups and weak (but present!) structure between Pleistocene-connected islands (🧵)
November 21, 2025 at 6:29 PM
Just out in Systematic Biology, we explore the role of gene flow in island phylogeography of the Solomons Black-and-white Monarch complex. doi.org/10.1093/sysb...
Up first, strong genetic structure between islands groups and weak (but present!) structure between Pleistocene-connected islands (🧵)
Up first, strong genetic structure between islands groups and weak (but present!) structure between Pleistocene-connected islands (🧵)
It’s because they couldn’t stop staring at the bird’s clown face.
October 29, 2025 at 2:51 AM
It’s because they couldn’t stop staring at the bird’s clown face.
At the end of a productive scouting and networking trip to Fiji. It was such a treat to see the species (and some additional specimens) that I worked on from afar during my PhD. Even more exciting was to meet long-term collaborators and connect with new ones. Excited to return next year!
August 7, 2025 at 7:28 AM
At the end of a productive scouting and networking trip to Fiji. It was such a treat to see the species (and some additional specimens) that I worked on from afar during my PhD. Even more exciting was to meet long-term collaborators and connect with new ones. Excited to return next year!
Already missing the #Evol2025 meeting in verdant Athens! It was inspiring to hear the amazing science everyone has been doing, and as always, see old and meet new evolutionary biologists.
June 25, 2025 at 8:07 PM
Already missing the #Evol2025 meeting in verdant Athens! It was inspiring to hear the amazing science everyone has been doing, and as always, see old and meet new evolutionary biologists.
Excited for #Evol2025! I'll be sharing work on the island size-genetic diversity relationship in the avifauna of the Solomon Islands. Come hear about results from single-radiation, comparative, and simulation work.
Check it out in Phylogeography 2 (Mon 6/23 11:15am, Athena GH)!
Check it out in Phylogeography 2 (Mon 6/23 11:15am, Athena GH)!
June 20, 2025 at 7:22 PM
Excited for #Evol2025! I'll be sharing work on the island size-genetic diversity relationship in the avifauna of the Solomon Islands. Come hear about results from single-radiation, comparative, and simulation work.
Check it out in Phylogeography 2 (Mon 6/23 11:15am, Athena GH)!
Check it out in Phylogeography 2 (Mon 6/23 11:15am, Athena GH)!
Stay tuned for more research on these whistlers, focusing on some fine-scale work on the contact zone, and how the lessons we learn from it can be applied to the rest of the genus!
April 17, 2025 at 4:19 PM
Stay tuned for more research on these whistlers, focusing on some fine-scale work on the contact zone, and how the lessons we learn from it can be applied to the rest of the genus!
Although the exact story has changed with genomic data, the important lesson of a lack of reproductive isolation upon secondary contact in these allopatric "great speciators" held true.
April 17, 2025 at 4:19 PM
Although the exact story has changed with genomic data, the important lesson of a lack of reproductive isolation upon secondary contact in these allopatric "great speciators" held true.
We used this data to revisit Mayr's 80 year old hypothesis (left), painting a picture of fast plumage evolution and post-contact gene flow within an archipelago as opposed to "failed" contact after inter-archipelago divergence.
April 17, 2025 at 4:19 PM
We used this data to revisit Mayr's 80 year old hypothesis (left), painting a picture of fast plumage evolution and post-contact gene flow within an archipelago as opposed to "failed" contact after inter-archipelago divergence.
There were other intermediates from the Ovalau, which were inferred as the first branch in the yellow-throated clade. However, this is because they are a hybrid population (more common on islands than zones) between an unsampled or genetically swamped population and one on nearby Viti Levu.
April 17, 2025 at 4:19 PM
There were other intermediates from the Ovalau, which were inferred as the first branch in the yellow-throated clade. However, this is because they are a hybrid population (more common on islands than zones) between an unsampled or genetically swamped population and one on nearby Viti Levu.
...because of a contact zone on the island of Vanua Levu between an unbanded and banded lineage. Island hybrid zones are quite rare in birds, so this is a particular great system for understanding allopatric speciation.
April 17, 2025 at 4:19 PM
...because of a contact zone on the island of Vanua Levu between an unbanded and banded lineage. Island hybrid zones are quite rare in birds, so this is a particular great system for understanding allopatric speciation.
We found that the Fiji Whistlers represented a monophyletic group that recently and rapidly evolved the high plumage diversity that drove interest in the group. Notably, the white-throated lineages were non-monophyletic, and there was lots of uncertainty in the north part of the archipelago...
April 17, 2025 at 4:19 PM
We found that the Fiji Whistlers represented a monophyletic group that recently and rapidly evolved the high plumage diversity that drove interest in the group. Notably, the white-throated lineages were non-monophyletic, and there was lots of uncertainty in the north part of the archipelago...
We sampled individuals from across the Fijian archipelago to test Mayr's hypotheses about the dynamics of secondary contact, particularly if there was evidence of hybridization after inter-archipelago colonization producing one of the main phenotypes in the archipelago.
April 17, 2025 at 4:19 PM
We sampled individuals from across the Fijian archipelago to test Mayr's hypotheses about the dynamics of secondary contact, particularly if there was evidence of hybridization after inter-archipelago colonization producing one of the main phenotypes in the archipelago.
Some species had an outsized role in shaping evolutionary theory. The Fiji Whistlers featured heavily in Ernst Mayr's development of the biological species concept and its application to allopatric taxa. In our new paper, we revisited this system with genomic data 🧵
doi.org/10.1093/sysb...
doi.org/10.1093/sysb...
April 17, 2025 at 4:19 PM
Some species had an outsized role in shaping evolutionary theory. The Fiji Whistlers featured heavily in Ernst Mayr's development of the biological species concept and its application to allopatric taxa. In our new paper, we revisited this system with genomic data 🧵
doi.org/10.1093/sysb...
doi.org/10.1093/sysb...
However, as you might expect, these variables are highly correlated with each other, both for the varied role pop size has on genomic diversity and analytical reasons. We attempted to disentangle them with LASSO regression, and inferred unique signals of derived TEs, ROH, and recent pop. size.
March 5, 2025 at 5:17 PM
However, as you might expect, these variables are highly correlated with each other, both for the varied role pop size has on genomic diversity and analytical reasons. We attempted to disentangle them with LASSO regression, and inferred unique signals of derived TEs, ROH, and recent pop. size.
We found that most of these metrics correlated significantly with island size, showing the elevated role of drift in smaller islands. Note that this is the logarithm of island size, so it isn't a simple 1:1 relationship between Ne and our proxy for population size (think Lewontin's paradox).
March 5, 2025 at 5:17 PM
We found that most of these metrics correlated significantly with island size, showing the elevated role of drift in smaller islands. Note that this is the logarithm of island size, so it isn't a simple 1:1 relationship between Ne and our proxy for population size (think Lewontin's paradox).