Asteraceae, a family of flowering plants that includes daisies, sunflowers, and asters, is the most varied category of flowering plants globally. This family consists of about 34,000 species, including well-known varieties like artichokes, chamomile, dahlias, and lettuce. A global research team, including participants from the University of Göttingen, has compiled and examined a new comprehensive database detailing the distribution and evolutionary background of all Asteraceae species. The researchers discovered an unexpectedly large number of evolutionary occurrences—referred to as ‘speciation,’ where new plant species evolve from a shared ancestor—taking place in the aster family over relatively brief time spans on numerous islands around the world. These findings were published in Nature Communications.
Asteraceae plants are notably present in the flora of isolated islands such as the Galápagos, Mauritius, and Polynesia. This family includes striking botanical species ranging from the diverse Bidens genus, called “two-toothed,” found in the Pacific islands, to the unique and highly endangered silverswords of Hawaii, and the massive Scalesia trees of the Galápagos Islands. While these plants are a prime example of island biodiversity, until now, the complete picture of their classification in the broader ecosystem has been unclear.
To address this issue, botanists and evolutionary biologists have worked together to create and analyze a global database containing data on the distribution and evolutionary background of all Asteraceae species across many islands. The team identified over 6,000 Asteraceae species native to islands, with nearly 60 percent existing solely on these islands. Their research supports a key theory in ecology and evolution, which posits that larger, isolated islands tend to have a higher number of unique species. Many of these species are at risk of extinction and are known only from a small number of individuals in the wild. “Asteraceae offers a wealth of information that assists researchers in understanding the factors driving the evolution of new species in some of the world’s most remote settings,” states Professor Holger Kreft, Head of Biodiversity, Macroecology and Biogeography at the University of Göttingen.
The researchers also pinpointed numerous potential speciation events yet to be discovered on islands globally. Speciation occurs within a limited geographical space over only several million years. During this interval, a common ancestor colonizes an island and gives rise to many new species that often vary greatly in size, shape, habitat, and other traits.
The volume of these newly detected evolutionary events surprised the researchers. “Botanists have long believed that Asteraceae has evolved in extraordinary ways on islands, but our study reveals that the degree of evolutionary innovation in this family may far exceed previous estimates,” remarks first author Lizzie Roeble from Naturalis Biodiversity Center in Leiden, the Netherlands. These insights emphasize the necessity of protecting this plant family.
