Browsing by Subject "Natural selection"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Natural Selection on Testosterone Production in a Wild Songbird Population
    (The American Naturalist, 2010-04-15) McGlothlin, Joel W.; Whittaker, Danielle J.; Schrock, Sara E.; Gerlach, Nicole M.; Jawor, Jodie M.; Snajdr, Eric; Ketterson, Ellen D.
    Because of their role in mediating life‐history trade‐offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how natural selection acts on hormonal variation in the wild. In a songbird, the dark‐eyed junco (Junco hyemalis), field experiments have shown that exogenous testosterone alters individuals’ resolution of the survival‐reproduction trade‐off, enhancing reproduction at the expense of survival. Here we used standardized injections of gonadotropin‐releasing hormone (GnRH) to assay variation in the testosterone production of males. Using measurements of annual survival and reproduction, we found evidence of strong natural selection acting on GnRH‐induced increases in testosterone. Opposite to what would be predicted from the survival‐reproduction trade‐off, patterns of selection via survival and reproduction were remarkably similar. Males with GnRH‐induced testosterone production levels that were slightly above the population mean were more likely to survive and also produced more offspring, leading to strong stabilizing selection. Partitioning reproduction into separate components revealed positive directional selection via within‐pair siring success and stabilizing selection via extrapair mating success. Our data represent the most complete demonstration of natural selection on hormones via multiple fitness components, and they complement previous experiments to illuminate testosterone’s role in the evolution of life‐history trade‐offs.
  • Thumbnail Image
    Item
    Three unconventional maxims in the natural selection of cancer cells: Generation of induced tumor-suppressing cells (iTSCs)
    (Ivyspring, 2023-02-27) Li, Kexin; Huo, Qingji; Li, Bai-Yan; Yokota, Hiroki; Biomedical Engineering, School of Engineering and Technology
    Induced tumor-suppressing cells (iTSCs) can be generated from cancer and non-cancer cells. Here, three paradoxical maxims for the action of iTSCs are reviewed: the secretion of tumor-suppressing proteins, their role as a "double-edged" sword, and the elimination of lesser-fit cancer cells. "Super-fit" cancer cells secrete an array of proteins, most of which contribute to enhancing their growth and removing "lesser-fit" cancer cells. These maxims explain the potential dilemma with therapeutic agents since the inhibitory agents tend to promote the synthesis of tumor-promoting proteins. The maxims suggest the possibility of a novel treatment option using cancer-guided evolutionary-fit iTSCs.