Plants from fragmented populations may be more susceptible to disease, according to a 12-year study of a weedy herb in Finland. The findings, which appear today in Science, are somewhat worrisome given how much of the global landscape has
Plants from fragmented populations may be more susceptible to disease, according to a 12-year study of a weedy herb in Finland. The findings, which appear today in Science, are somewhat worrisome given how much of the global landscape has been broken up into small, isolated pieces.
Habitat fragmentation is not uncommon. Land may be crisscrossed by roads, replaced by farm fields or towns, or drowned in the reservoirs created by hydroelectric dams. It’s easy to understand what the loss of those spaces can means for the plants and wildlife that no longer have homes—less so for the creatures and vegetation left behind in the patchy landscape.
How plant diseases spread through landscapes isn’t particularly well known; research has often focused on disease outbreaks, particularly among the agricultural crops people depend on for food. But pathogens are a natural part of the ecosystem. And scientists would like to know more about how they persist in the wild, and how human activities change things.
In the new study, Jussi Jousimo of the University of Helsinki and colleagues collected data from populations of the weedy herb Plantago lanceolata in the Åland archipelago of southwestern Finland. This area is home to thousands of populations of P. lanceolata, some of which are more fragmented and isolated than others due to the size and distribution of the islands.
Every year, a small percentage of the plants become infected with the powdery mildew Podosphaera plantaginis. The mildew is easy to spot on the leaves of the plant, and for 12 years, some 40 field assistants went out to the islands and tracked where the powdery mildew could be found among 4,000 populations of the herb.
The number of infected plants varied from year to year, from a low of 1.1 percent to as high as 16.9 percent in 2012. But overall, the mildew was more likely to infect plants from the highly fragmented areas than the highly connected ones. And when the researchers attempted to delibe