A research team led by the University of Göttingen studied the morphological and functional differences between island and mainland plants. Oceanic islands are important platforms for studying ecology, biogeography and evolution. Many groundbreaking discoveries, including Darwin's theory of evolution, were made by studying the interactions of species on these islands with their surrounding biotic and abiotic environments. Recently, an international research team led by the University of Göttingen took an in-depth look at plant life on the Canary Islands of Tenerife.
The results were unexpected: the island has a wide variety of plant species. Functionally, however, these plants are not significantly different from those found on the continent. However, unlike mainland flora, Tenerife's flora is dominated by slow-growing woody shrubs with a "low-risk" life strategy. The findings were recently published in the journal Nature.
Researchers investigated how Tenerife's plants function differently from those in other parts of the world. They conducted extensive field studies and measurements at more than 500 sites using the latest functional ecology methods. These sites are distributed across the island from sea level to mountainous areas above 3,300 meters above sea level.
Island plants like this flowering herbaceous plant (Echium wild pretii) known as "jewel tower" display wonderful adaptations to their living and non-living environments. Research shows that medium-sized, slow-growing woody shrubs dominate the flora of Tenerife. Photo credit: Jose María Fernandez Palacios
The scientists documented approximately 80% of Tenerife's native seed plants and investigated eight plant characteristics: plant size, specific wood density, leaf thickness, absolute and specific leaf area, leaf dry matter, nitrogen concentration in leaf tissue, and seed weight. They compared this data with that of more than 2,000 plant species found on the continent.
"Our study shows for the first time that, contrary to all expectations, species groups evolving on the Canary Islands do not promote an expansion of the breadth of different traits," explains Professor Holger Kreft from the Biodiversity, Macroecology and Biogeography Research Group at the University of Göttingen, who led the study.
Previous comparisons have shown that species that occur on islands can be very different from their mainland relatives. A famous example is the Galapagos giant tortoise: this species is found only in the Galapagos Islands and is much larger than giant tortoises on the mainland due to its adaptation to the environmental conditions on the islands.
The team had expected that the island's plants would be similar to those on the mainland, but this was not the case. "Instead, we found that most species followed the constraints of the island's climate. As a result, medium-sized woody species developed. These species tend to live on islands with limited resources and a high risk of extinction. That is, they grow slowly. The high functional diversity is mainly due to species that are widely distributed on the island and on the nearby mainland," explains Kreft.
First author Dr. Paola Barajas Barbosa explains: "At the beginning of the study, we hypothesized that island plants would show fundamental differences and that their functional diversity would be rather limited due to their geographical isolation. These results were produced as part of her doctoral thesis at the University of Göttingen. She is now working as a researcher at the German Center for Integrated Biodiversity Research (iDiv) in Leipzig. We were even more surprised to find that the plants on Tenerife have a relatively high functional diversity."