Volume 80, Issue 4, April 2026

Mate choice for a dissimilar partner is a mechanism by which the MHC repertoire of offspring can be improved. In this study of reed warblers, we provide evidence that this could be achieved through extra-pair mating at random. Because, when MHC similarity with the social male is very high, any other male may represent a better prospect for the female in terms of MHC dissimilarity.

Humans significantly altered the shape and composition of the dog brain relative to wolves. Frontal lobes and areas associated with social behavior are larger in dogs, and in cooperative breeds compared to independent ones, emphasizing the role of social behavioral selection on dog brain evolution. Ancient breeds, i.e., Siberian Husky, retain wolf-like neuroanatomy compared to modern breeds, i.e., German Shepherd. The dog brain is more integrated, or coordinated across subregions, challenging the conventional understanding of the brain’s capacity to evolve. We highlight the extraordinary evolvability of the mammalian brain under domestication, and how humans have impacted on our closest companions.

Is evolution predictable? To explore this, we studied three hybrid zones between the yellow Lemon-rumped (R. f. icteronotus) and red Flame-rumped (R. f. flammigerus) Tanagers in western Colombia, where independent low mountain passes provide natural tests of repeatability. We found that under similar demographic and environmental conditions, the overall magnitude and directionality of neutral introgression was predictable—from yellow to red—but that only traits putatively involved in reproductive isolation, such as plumage color, showed consistent patterns of introgression. Additionally, because hybrid zones differed in age, we were able to track the progression of introgression over time. We show that while interbreeding produces variable outcomes at the level of individual genomic regions, similar ecological and demographic contexts can drive repeatable hybrid zone movement, with key loci stabilizing divergence despite gene flow.

Homeostatic traits exhibit both active and passive phenotypic plasticity—but how do these components interact? Using a new model that enables separating the passive and active dynamics, we analyzed 653 experiments tracking ion and osmolality shifts in aquatic organisms experiencing environmental salinity change. Clear phylogenetic patterns emerged: ray-finned fishes regulate faster and more strongly than crustaceans, and magnesium stands out as the most tightly controlled ion. By disentangling the passive vs. active components of homeostatic trait regulation, our approach provides new opportunities for studying novel ecological and evolutionary aspects of phenotypic plasticity.