Pollination changes in the Caribbean after Hurricane Maria demonstrate ecological resilience

Most flowering plants rely on animals for pollination. In warm, humid tropical regions, more than 90% of plant species are pollinated by animals. In Dominica, an island country in the Caribbean, researchers have identified a mutualistic relationship between two species of heliconia (Heliconia bihai and H. caribaea) and their hummingbird pollinator, the purple-throated caribbean (Eulampis jugularis). The association is so specific that it has often been cited as an example in scientific literature.

It is for this reason that when Hurricane Maria (category 5, the highest on the Saffir-Simpson scale, with sustained winds of more than 250 km/h) hit the region in 2017 and killed 75% of the total population of E. jugularis, these two species of E. heliconias were expected to disappear.

However, an article recently published in New plant scientist shows that other birds have become pollinators of the plants in question. The authors are based in Brazil, Denmark, Switzerland, the United States and the United Kingdom, with contributions from the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima), a research center, d Innovation and Diffusion (RIDC) located in Rio Claro, Brazil. .

“In 2022, we studied the region in great detail, analyzing the types and rates of heliconia bird visitation, as well as the patterns of pollen deposition and transport. Our results highlighted drastic changes: d “Other hummingbird species as well as the Bananaquit (Coereba flaveola) had begun to visit and pollinate heliconia flowers at rates similar to those of E. jugularis or even higher,” said Fernando Gonçalves, a current CBioClima member. postdoctoral researcher affiliated with the laboratory of Jordi Bascompte at the University of Zurich (UZH) in Switzerland.

“Our analysis suggests that the population decline of E. jugularis led to a breakdown in competitive exclusion of other species and allowed other birds to become effective pollinators. We concluded that pollination systems “Specialized species can become widespread after natural disturbances such as hurricanes, showing that the ecosystem was resilient,” he said.

The birds were captured near heliconia plants using mist nets (made of nylon or polyester mesh suspended between two poles, resembling a volleyball net), and the pollen stuck to their beaks and to their feathers was sampled using a special jelly. The cameras allowed researchers to identify birds when they visited the plants, and pollen deposition was measured by inspection of floral stigmas after the visit.

“E. jugularis is very territorial and aggressive. When the population was large, no other bird species could approach the heliconias, but once the population was reduced to only a quarter of its original size, it did not There were no longer enough individuals to keep other species of hummingbirds and the Bananaquit away from the plants. These new pollinators are generalists. They collect pollen from several species of plants and the Bananaquit feeds on fruits. declared Gonçalves.

This discovery was important for two reasons. First, it was thought that only E. jugularis could pollinate H. bihai and H. caribaea because the shape of their flowers matches the size and curvature of this hummingbird’s beak. The females of E. jugularis have long curved bills and are the main pollinators of H. bihai, while H. caribaea is pollinated by both females and males, although the latter’s bills are shorter and straighter.

The second, even more important reason why this discovery is important is that it shows that species extinction is a much more complex process than is often realized. The devastation caused by Hurricane Maria disrupted the co-adaptation and co-dependence of plants and hummingbirds, leaving other birds to take their place.

Evolutionary paths can be winding instead of highly linear. This is particularly relevant in the context of the current climate crisis, in which extreme events such as severe droughts, torrential rains, floods, hurricanes, etc. are more common and where species disappear in a relatively short time.

“If no further mass destruction occurs in Dominica, we believe that the two species of Heliconia and E. jugularis could re-establish their exclusive mutualism within approximately 15 to 20 years. The population of E. jugularis will have increased again and there will be a lot of individuals defending their territory,” Gonçalves said, adding that his team is conducting more research in the area to test this hypothesis. They also plan to assess the impact of natural phenomena on the evolutionary behavior of other species.

“We are monitoring hurricanes in the area so we can go back and investigate the aftermath.”