Damselflies in Distress

Scope Correspondent

Dainty neon-blue damselflies, flitting along the streams of southern Europe, might soon be replaced by a different species, perhaps one that doesn’t even exist right now.
Many organisms are coping with a warming climate by moving to new areas. There, they sometimes bump into similar species that are already present. The outcome of these interactions could be serious. “Increased overlap [of species] will have massive consequences,” said Maren Wellenreuther of Lund University.

One consequence could be interbreeding, resulting in a genetically souped-up version of the invading species or even a brand new hybrid species that replaces the original one. Hybridization is not new, but it might become more frequent as climate change impacts species’ ranges. These hybridization events are happening around the world in all sorts of animals, from birds such as warblers to grizzly and polar bears.

It could also happen in seven related species of Mediterranean damselfly, according to a recently published study led by Rosa Ana Sanchez-Guillén of the Autonomous University of Barcelona. Previous work in collaboration with Wellenreuther, who was not part of the most recent study, showed that hybridization is already underway between two of these damselfly species.

The recent work is part of a newer trend to incorporate more biology into models to try to figure out what climate change really means for life on Earth. “The novel part of this paper is that it combines range shifts with an eye toward hybridization,” said Mark Urban at the University of Connecticut, who was not part of the research.

The researchers used both computer models that predict where each damselfly species will be in the future and biological knowledge about their mating behavior. This combination technique could help identify species that are threatened by hybridization and inform conservation efforts, hopes Sanchez-Guillén.

Damselflies are similar to dragonflies but smaller and weaker fliers. Unlike dragonflies, which rest with their wings perpendicular to their spindly tails, damselflies keep their wings parallel to their body.

Previous work by Sanchez-Guillén and her collaborators had shown that the amount of genetic difference between separate species of damselfly could predict whether or not the species would be physically able to mate. Given this observation, the scientists examined barriers between species that could prevent interbreeding, such as different mating seasons or a physical mismatch in how the male and female line up their relevant organs. They found that five of the seven Mediterranean species of damselflies they studied are similar enough to interbreed and create hybrids. Next, the researchers predicted where each damselfly species might be found in the years 2020, 2050, and 2080 based on two environmental variables describing their habitat: precipitation and temperature.

These are only two of the relevant factors in the environment of any damselfly species, but they could be enough to describe where that species lives with relative accuracy. “We can predict a lot for insects with temperature alone, even, because it is so crucial for insects,” said Wellenreuther.

Other scientists, however, think the models’ predictions should be interpreted with care. “It works well in modeling current ranges, but there’s a big question of how well it models other periods. There’s an assumption that the relationship between the animal and the environment will be the same into the future even as that environment is changing,” said Morgan Tingley, a fellow of the Woodrow Wilson School at Princeton University not involved in the study.

The quality of the available data to build a model can vary too, said Keith Larson of Umeå University, who also did not participate in the study. The authors of the study tried to avoid this problem by focusing on a small number of well-characterized environmental factors, explained Jesús Muñoz of the Real Jardin Botanico in Madrid, one of the study’s coauthors. “Most models with only climactic information are really accurate,” Muñoz said. Adding geographical features like running water to the model is difficult because parts of the damselflies’ range had very little of this data.

A third concern is that important information might be missing from the models. “To my mind, a more important factor is invasive species,” said Jürgen Ott, a conservation scientist who was not part of the study. These kinds of biological interactions could be more important that non-biological factors like temperature in determining a species’ range, explained Wim van der Putten at the Netherlands Institute of Ecology, who was also unaffiliated with the study. “You have to realize that this is not representing the whole reality,” he said.

Even with these concerns, many scientists seemed to agree that the work is, as Tingley put it, “definitely the right direction to be going in” to understand the biological consequences of range shifts. “It was a first step, but not everything,” said van der Putten. “It implies we need to do more research from different viewpoints to see what is more or less important [for determining species range].”

“The models set you up with hypotheses you can go out and test, and that’s useful,” said Larson. “I think these models do have a lot of potential benefit.”
Currently, Sanchez-Guillén and her colleagues are applying their models to examine what might happen to the rare damselfly Ischnura gemina, which is unique to the San Francisco Bay area.

Conservationists have already tried to reintroduce I. gemina, so Sanchez-Guillén and her team hope their research will indicate whether these efforts are useful or a losing battle against the damselfly’s displacement through hybridization with an invading species.
In seven years’ time, scientists should be able to begin to test the models’ hypotheses of species range and interbreeding both in California and around the Mediterranean, and maybe they’ll even discover a new species of damselfly.