Dragonfly Predators Offer a New Route to the Future of Biodiversity

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Dragonfly Predators Offer a New Route to the Future of Biodiversity

Scientists have had a hard time trying to predict the future of biological diversity in the past. But according to a new scientific development, the mystery may have reached its end. A recent study carried out by a team of researchers from Rice University shows that predators that prey on dragonfly and damselfly communities can provide vital information about future consequences of biodiversity loss.

Rudolf and his students spent four years exploring seasonal changes in 45 remote ponds spread across Angelina and Davy Crockett forests in East Texas. They collected and examined more than 18,000 insects, fish, and amphibians in quarterly visits, starting from 2011 to 2015.

According to their findings, as the size of top predators increased, habitats exhibited a lower turnover of species across different locations and years. However, there was a relatively larger seasonal turnover within specific sites. Their discovery points to the important role played by ecological filters in the regulation of prey populations. In this case, observations made on voracious fish - an ecological filter that feeds on dragonflies and damselflies – provide key information that can aid ecologists in making accurate predictions of biodiversity loss and the sustainability of future habitats.

The finding has enflamed new hope for many scientists who have been struggling to predict the effects of biodiversity loss, mainly because of the obscurity that lies in the biological composition of various habitats across time and space. According to Volker Rudolf, an associate professor of biosciences at Rice and the lead researcher in the latest study, ecologists have, in the past, thought of biodiversity as a concept primarily bound by space. As a result, they have disregarded the aspect of time and, instead, relied on maps to study changes in biodiversity across various habitats.

This is hugely in contrast with Rudolf’s findings, which point towards time as a significant variable. "In reality, biodiversity changes over time just as much and in many different ways,” he says. "There are ecological theories that suggest that community dynamics should be connected in both time and space, but we typically just infer the temporal dynamics from the spatial patterns. In a sense, people have sort of done this backward. They assume that if these dynamics happen over time, then here's what we should see in space. In our case, we don't assume. We actually show what happens."

Based on the four years of research, study co-author and a postdoctoral researcher at the University of California, Davis, Nick Rasmussen believes that dragonflies and damselflies were the most reliable organisms to use in their analysis in East Texas because the region is home to more than 60 species. "We've got a lot of the tropical species, and a lot of the North American species, and if you go out and look at a specific pond, you'll see there is a lot of variation in what species is where," said Rasmussen.

Rather than just investigating the extent to which life varied in each pond from season to season, the research team at Rice also examined and compared changes observed in the same seasons across the four-year study period. Rudolf and his colleagues returned each spring, summer, winter, and fall, and recorded four sets of data on a seasonal basis as well as four additional sets of data on an annual basis.

They proceeded by analysing the differences and identifying systematic changes in spatial and temporal patterns of a variety of dragonfly populations across ponds with different ecological filters (top predators). The results indicated that there was a connection between the number of dragonfly communities and the presence of predatory fish that lived in each pond.

According to study lead author and postdoctoral researcher at the University of California Benjamin Van Allen, each of the fish ponds exhibited dramatic variations in the diversity of dragonflies, although the observed changes were reasonably consistent with the number of fish predators that lived in the same pond.

On the other hand, Rudolf’s research team recorded more diversity in ponds that lacked fish or those that contained few numbers of them. Such ponds also showed less consistency in changes observed across seasons and years compared to those that had top predators. Thus, dragonfly communities flourished considerably over time where no predators existed. The study, which is the first of its kind, demonstrates that ecologists can get a sense of the total biodiversity in habitats by observing and recording data concerning strong ecological filters that live there. Co-author Chris Dibble, who is a postdoctoral researcher at Indiana University, says that if ecological filters are absent, then researchers should increase the frequency of the sites under study and analyse them across larger time intervals to increase reliability and precision. More importantly, the research shows that the presence or absence of ecological filters can alter the biodiversity of a certain habitat significantly, and thus, it is key for ecologists to account for such differences as they seek to predict future consequences of biodiversity loss.

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