By: Emily Desrosiers, Molly Nyhan, and Tyler Umbra (Stonehill College, BIO323: Evolution, Spring 2026)
In the forests of Europe and Asia, there is a group of small, greenish birds called leaf-warblers. These birds look physically identical to the average person as well as many experts. For years, they have been an evolutionary puzzle: how do species that look so similar end up living in such vastly different environments?
To answer questions like these, researchers make use of phylogenetic trees—diagrams that show how different groups of living things are related and from whom they evolved. If we can trace the ancestry of a bunch of these leaf-warblers, surely, we can get a picture of how and when they spread across vast distances, right? This is where the work of Gräf et al. (2025) comes in, with their recent article published in the journal Diversity, titled “Climate-Niche Evolution in Leaf-Warblers (Aves: Phylloscopidae): A Matter of Phylogeny”.
By: Haley Lussier, Madison Navega, and Madison Warren (Stonehill College, BIO323: Evolution, Spring 2025)
Did you know humans are most closely related to chimpanzees? Chimpanzees are remarkably diverse in their adaptation to different habitats, just like we are. Whether you are from Australia or the United States, your population can adapt to the habitat you are in. One cannot deny that change affects habitats, species, and the planet as a whole. Conservation biology has become a vital field for understanding and preserving biodiversity. One key concept in this field is local genetic adaptation, which ensures a species is well-suited to its environment and retains the potential to adapt over time. The recent Science article “Local genetic adaptation to habitat in wild chimpanzees,” by Dr. Harrison Ostridge and 73 coauthors, investigates the differences in the genetic makeup of wild chimpanzee populations to look for evidence that these differences provide an advantage in different environments. Dr. Ostridge completed this research as part of his Ph.D. dissertation at University College London, where he focused on population genomics and its relationship to disease adaptation.
By: Savannah Jeffrey, Julia Ciccolo, & Julia Bennett (Stonehill College, BIO323: Evolution, Spring 2025)
Overview: In many populations of cave-adapted animals, there is an increased presence of single-nucleotide premature termination codons, known as PTCs, that lead to traits losing function. PTCs are a type of mutation that cause a random stop to genetic replication processes, which can have deleterious effects on how traits are expressed. PTCs have been observed in the genetic makeup of many evolved cave species like cavefish, specifically the Mexican tetra, Astyanax mexicanus. Mexican tetras can be found in central and eastern Mexico, as well as in Texas. They originated in bodies of waters such as lakes and rivers, where eventually some Mexican tetras colonized cave systems and formed new populations. Due to these smaller population sizes in these environments, these mutations are subject to much stronger genetic drift, which occurs when alleles increase or decrease by chance in a population. This phenomenon causes traits to become more common or disappear entirely, thus making a population genetically distinct from their ancestors. Cave environments have their own unique selective pressures and allow the loss of traits to be advantageous for organisms, mainly features like eyesight, pigmentation, and circadian cycling. Allocating resources to these traits in an environment where they are not required provides no benefit to these organisms, therefore the loss of them actually positively impacts the species’ fitness, allowing them to invest in other metabolic processes. Additionally, the majority of PTCs arise in redundant genes, reducing the risk of losing genes that are vital for survival.
