In the 1990s, when Kauai crickets in Hawaii sang love songs with their wings to attract mates, a new island visitor was listening: the parasitic fly Ormia ochracea. The flies laid their larvae inside the singers, killing them from within. By 2001, most of the crickets had vanished - until a twist appeared: some males grew flat, silent wings, unable to sing but able to survive. But not every species finds a way to endure in a new environment. In Costa Rica, the golden toad faced a sudden shift in its cloud-forest home: an unusually severe El Niño in the late 1980s dried up its breeding pools, and a fungal disease struck soon after. Within a few years, the golden amphibian was gone forever. Whether a species flourishes or fades depends on how well it can cope with sudden environmental change.
Today, with ecosystems shifting faster than ever due to climate change, habitat loss, and human activity, scientists are asking a crucial question: how do species survive in new hostile environments, and what makes some succeed while others fail?
A recent study from Dr Deepa Agashe’s lab at NCBS used the red flour beetle as a model to explore these questions. The researchers followed beetle populations for more than five years as they adapted to a difficult new environment. The findings show how traits of the founding populations shaped long-term survival of their descendants in a new environment.
“Red flour beetles are a great system for this kind of work”,says Dr Vrinda Ravi Kumar, the lead author of the study. “They live and breed in flour, and since they reproduce quickly and are easy to keep in the lab, we could follow them across tens of generations”, she added.
The research team collected red flour beetles from ten different locations across India. They raised these beetles for several generations in their natural wheat flour habitat within the lab to stabilize them. Then they challenged them with a harsh environment - corn flour. Three replicate populations taken from each of the ten wild populations were followed for seventy generations of beetle life, which adds up to over five years.
The researchers measured a wide range of traits in the original beetles: how long adults survived, how well they endured starvation, how many offspring females produced, whether larvae cannibalised eggs, and how quickly larvae developed into adults. Although the ten populations differed in survival, developmental speed, and reproduction, nearly all of them showed the same story: numbers first plummeted, then bounced back within about twenty generations. This pattern is called evolutionary rescue, where rapid adaptation prevents extinction in a harsh new environment. Although almost all the experimental populations were rescued, this did not mean they all performed equally well afterwards. Some populations remained smaller or more variable, while others recovered to much larger sizes and maintained more stable numbers over time.
What gave these populations their edge? The team found that one trait stood out as a powerful predictor of long-term average population size in the new environment: the speed at which larvae developed into pupae. Populations with larvae that matured faster likely generated fertile females earlier, and these populations went on to grow larger and more stable. Another trait also mattered. As Vrinda explains, “We also found that in the new environment, female lifespan and reproduction played an important role. This tells us that populations which can reproduce faster and in greater numbers tend to be more successful, probably because they already have enough variation in these traits to adapt quickly.”
“Counting thousands of beetles over many years can lead to interesting new insights,” says Dr Deepa Agashe, the principal investigator of the study. “The details of how quickly a population crashes or bounces back cannot be predicted just from the traits of founding populations, and they don’t always tell us which populations will thrive in the long run. That’s why long-term studies, both in the wild and in the lab, are so valuable. Our lab beetles have now passed 100 generations, and as they continue to evolve, they are teaching us more about how species adapt to new challenges than we ever imagined,” she added.
Full link to the study: https://www.pnas.org/doi/10.1073/pnas.2506244122
0 Comments