Harder, better, faster, stronger. Climate change enhances the spread and impacts of an invasive thistle by advancing reproductive phenology
Written by Dan Buonaiuto, edited by Matt Brincka
Summary:
Shifts in phenology (the timing of seasonal life cycle events such as flowering or leafout) are one of the most widely observed biological responses to climate change. Earlier flowering and seed release may increase the number of offspring plants produced, enhancing survival and growth rates. For invasive species, these kinds of changes may accelerate their spread and increase their impacts on local diversity, but generally, the demographic consequences of phenological shifts are not well studied. Keller and Shea (2021) investigated this link between climate warming, phenological shifts and population dynamics in a field experiment with the invasive musk thistle (Carduus nutans). By manipulating temperature and seed release phenology, they integrated their results into a common-use demographic model to predict population growth and spread. Warming temperatures increased the probability of survival and individual growth rates of seedlings, and earlier phenology resulted in larger offspring and a 10% increase in the proportion of the population that flowered as annuals. Based on these changes to the life cycle of musk thistle, the demographic models projected a 15% increase in the population growth rate with climate change.
Higher population growth rates that result from earlier phenology, increased annualism and increased seedling survival may become more common for invasive species in general, especially those growing in low competition environments such as agricultural areas, which could threaten food security and require more intensive management. Understanding phenology’s role in populations’ growth and decline can guide the conservation of species that are negatively impacted by climate change as well as reduce the impacts of invasive species.
Take home points:
Warming significantly increased the survival and growth of thistle seedlings.
Earlier seed release increased annualism and size at flowering.
Together these factors increased population growth rate by ~15%, suggesting an increase in the spread and impacts of musk thistle with climate change.
Management implications:
Managers will need to increase management efforts to maintain acceptable levels of population control.
Keywords:
Phenology, Shifting Seasons, Annualism, Demography