That smaller islands will typically sustain fewer species than large ones is a widespread pattern in nature. Now a team of researchers shows that smaller area will mean not only fewer species, but also shorter food chains. This implies that plant and animal communities on small islands may work differently from those on large ones.
Top predators the first to go
Working across a set of 20 islands off the Finnish coast, a group of Finnish scientists found that a disproportionate number of small islands were lacking the highest levels of the food chain. The results are freshly online in the journal Ecography.
"Ecologists have known for decades that less area means fewer species", explains Tomas Roslin, who spearheaded the current analyses. "What we show is that the decrease in species richness with decreasing area gets steeper when you climb up the food chain. That means that when you move towards smaller island size, you run out of top predators before you run out of intermediate predators, and that you lose the last plant-eaters before you lose the last plant."
The study comes with broad implications for a world shattered by human activities. "While we worked on a set of real islands, you can probably think of habitat fragments as 'islands' in a broader sense", says Tomas. "What our results then mean is that if we keep splitting natural habitats into smaller and smaller pieces, we may not only lose a lot of species from the resultant fragments, but also change the structure and functioning of local food webs."
Knowing your species the key to insights
To explore the effects of island size, the research team focused on islands spanning a hundred-fold range in area. On each of these islands, the team took samples of local food chains consisting of four levels: plants, predators feeding on the herbivores, and top predators feeding on the predators themselves.
Among predators, the researchers targeted a specific
|Contact: Tomas Roslin|
University of Helsinki