Alec Downie
@aedownie.bsky.social
Postdoc studying evolutionary ecology, trait evolution, and immunity at the Max Planck Institute for Evolutionary Anthropology @mpi-eva-leipzig.bsky.social; he/him
We also take a brief detour into genetic architecture, on the heels of findings from both theoretical evolutionary genetics and ecological immunology suggesting that differing architectures (in polygenicity or pleiotropy) may have substantive implications for when and how immune defenses can evolve.
November 17, 2025 at 10:28 AM
We also take a brief detour into genetic architecture, on the heels of findings from both theoretical evolutionary genetics and ecological immunology suggesting that differing architectures (in polygenicity or pleiotropy) may have substantive implications for when and how immune defenses can evolve.
We briefly discuss how the overarching aspects of immune strategy hypothesized in immune theory may be encoded in phenotypes and in the genome, an ongoing challenge for translating between these two approaches.
November 17, 2025 at 10:28 AM
We briefly discuss how the overarching aspects of immune strategy hypothesized in immune theory may be encoded in phenotypes and in the genome, an ongoing challenge for translating between these two approaches.
3. How do immune differences across species originate? Many taxa display unusual immunological phenotypes (e.g., bats and constitutive cytokine expression) hypothesized to spring from their particular biology. Can we see signatures of this with broad phylogenetic analyses?
November 17, 2025 at 10:28 AM
3. How do immune differences across species originate? Many taxa display unusual immunological phenotypes (e.g., bats and constitutive cytokine expression) hypothesized to spring from their particular biology. Can we see signatures of this with broad phylogenetic analyses?
2. What constrains immune evolution? For example, resource-based trade-offs between immunity and life history traits are a common prediction. But are there genetic correlations in these traits in nature, such that these relationships can actually respond to selection?
![Screenshot of paper with text:
What constrains immune evolution?
A basic expectation, if parasite infection limits host fitness, is that immune phenotypes should adapt to this selective pressure 10•, 30. However, host resistance is typically far from complete. In some cases, hosts may simply not have had enough time to adapt [31]. But when hosts and parasites have interacted on long timescales, other explanations are necessary. In evolutionary genetics, a major focus has been on host–parasite co-evolution and evolutionary arms races 5, 32, where parasites undergo selection to evade host defenses at the same time that hosts experience selection to restrict parasites. For example, protein kinase R shows evidence of repeated adaptive evolution in primates to evade sabotage by poxviruses, which themselves rapidly evolve [33]. Evolutionary arms races are clearly important in cases where host defense and parasite evasion can evolve through relatively simple genetic mechanisms.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:3h4sde5pwexxzj7w5tof34p5/bafkreiggopnvb4advvg5rnmhd7ly4at3arz2xztmskovfg2f2ugewwkbwe@jpeg)
November 17, 2025 at 10:28 AM
2. What constrains immune evolution? For example, resource-based trade-offs between immunity and life history traits are a common prediction. But are there genetic correlations in these traits in nature, such that these relationships can actually respond to selection?
1. When and where should immune traits be targeted by natural selection? What should we actually expect the signatures of selection to look like – which traits, which genes – and how is that modulated by the ecology and demography of the host?
![Screenshot of paper with text:
Where and when should immune defense be targeted by natural selection?
Host immune systems include components that contribute to parasite recognition (e.g. pattern recognition receptors), signaling and coordination (e.g. cytokines, JAK-STAT pathway proteins), memory (e.g. vertebrate lymphocytes, CRISPR/Cas spacers in bacteria), and toxicity (e.g. vertebrate natural killer cells, antimicrobial peptides [AMPs]). The activity and efficiency of these components typically have a heritable component and so can evolve via natural selection. However, some classes of immune genes, such as the major histocompatibility complex (MHC) in vertebrates and components of...
(it cuts off)](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:3h4sde5pwexxzj7w5tof34p5/bafkreifg3i3tcjs3tiaiffsrgqfkcn7kwqwbsjdiprgubtegjafafjxk5y@jpeg)
November 17, 2025 at 10:28 AM
1. When and where should immune traits be targeted by natural selection? What should we actually expect the signatures of selection to look like – which traits, which genes – and how is that modulated by the ecology and demography of the host?