November 21, 2019 — The threespine stickleback, a small fish found throughout the coastal areas of the Northern Hemisphere, is famously variable in appearance from one location to another, making it an ideal subject for studying how species adapt to different environments. A new study shows that stickleback populations in estuaries along the coast of California have evolved over the past 40 years as climate change has altered their coastal habitats.
The study, published November 21 in Global Change Biology, looked at variation in the armoring that protects the stickleback from predators, specifically the number of bony plates along their sides (called lateral plates). Previous research showed that populations in northern California have a more complete set of this armoring than populations in southern California, corresponding to differences in their habitats.
“There’s a gradient from drier systems in the south, where the estuaries are more pond-like, with more vegetation, to increasingly more open, river-like systems as you go north,” explained coauthor Eric Palkovacs, associate professor of ecology and evolutionary biology at UC Santa Cruz.
The new study found that threespine stickleback in some California estuaries are evolving to have fewer lateral plates as their habitats become more pond-like due to a warmer, drier climate. Stickleback populations at some central California sites are now looking more like the low-plated populations typical of southern California.