Why can some species adapt rapidly to environmental adversity, while other species do not? In fact, there easily could be inter-individual differences, even among one species (e.g. human, mouse, fish, bacteria, tumor cells within the same cancer) in which one individual shows strong resistance whereas the next individual shows enhanced susceptibility. This paper [attached] is an example involving Atlantic killifish populations and their ability to rapidly adapt to “normally lethal levels” of “pollution” in four urban estuaries.
Authors analyzed 384 whole killifish genome sequences, and comparative transcriptomics, in four pairs of “highly-sensitive” versus “highly-resistant” populations. They identified aryl hydrocarbon receptor (AHR)–based signaling pathways as a shared target of selection. In many ways, this is no different from studies in the 1970s (from the lab of That Nebert Guy), comparing “highly-sensitive” to “highly-resistant” mice in which the environmental signal (in those observations, long ago) was dosage of polycyclic aromatic hydrocarbons (PAHs) and dioxin. Which also turned out to reflect AHR-signaling pathways.
These killifish data suggest “evolutionary constraint” as on adaptive solutions to complex toxicant mixtures at each urban estuary site. However, distinct molecular variants apparently contribute to adaptive-pathway modification –– among tolerant populations. Selection in response to this environmental stress (i.e. in this case, aquatic polluation) also targets other toxicity-mediating genes and genes of associated signaling pathways. Authors conclude that their findings indicate “complex tolerance phenotypes” and potentially compensatory adaptations. These molecular changes are consistent with inter-individual differences –– due to each individual’s genomic architecture. Authors conclude that, in killifish, their “high nucleotide diversity” appears to have been a crucial property for “selective sweeps to propel rapid adaptation.” To me, this sounds like very eloquent language, but little actual meaning or substance….. 🙁
Science 9 Dec 2o16; 354: 1305–1308