Ecosystems are more resilient than expected after natural disasters 

Most flowering plants rely on animals for pollination, and in tropical regions, over 90% of plant species are pollinated by animals.

On the Caribbean island of Dominica, researchers have discovered a specific mutualistic relationship between two species of heliconia plants (Heliconia bihai and H. caribaea) and their primary hummingbird pollinator, the purple-throated carib (Eulampis jugularis). 

This relationship is so specialized that it has been frequently cited in scientific literature as an example of plant-pollinator co-dependence.

Impacts of Hurricane Maria 

When Hurricane Maria, a Category 5 storm with sustained winds exceeding 250 kilometers per hour, devastated the region in 2017, it wiped out 75% of the entire E. jugularis population.

This led scientists to fear that the two heliconia species might face extinction due to the loss of their primary pollinator.

However, a recent paper published in the journal New Phytologist reveals that other birds have stepped in to pollinate these heliconia plants. 

Evidence of a resilient ecosystem 

Study co-author Fernando Gonçalves is an expert at the Center for Research on Biodiversity Dynamics and Climate Change and a postdoctoral researcher affiliated with Jordi Bascompte’s laboratory at the University of Zurich (UZH) in Switzerland.

“In 2022 we studied the region in great detail, analyzing bird-heliconia visitation types and rates, as well as pollen deposition and transportation patterns,” said Gonçalves.

“Our findings pointed to drastic changes: other hummingbird species and also the Bananaquit (Coereba flaveola) had begun to visit and pollinate heliconia flowers at similar rates to E. jugularis or even higher.”

According to Gonçalves, the analysis suggested that the decline in the population of E. jugularis resulted in a breakdown of the competitive exclusion of other species and allowed other birds to become effective pollinators. 

“We concluded that specialized pollination systems can become generalized after natural disturbances such as hurricanes, showing that the ecosystem was resilient.”

Monitoring hummingbird pollination

The researchers used mist nets to capture birds near the heliconia plants and sampled pollen from their beaks and feathers using a special jelly.

They also set up cameras to monitor the birds visiting the plants and inspected flower stigmas to measure pollen deposition after visits.

“E. jugularis is highly territorial and aggressive. When the population was large, no other bird species could get near the heliconias, but once the population had been reduced to only a quarter of its original size, there weren’t enough individuals to keep other hummingbird species and the Bananaquit away from the plants,” explained Gonçalves.

“These new pollinators are generalists. They collect pollen from several plant species. And the Bananaquit feeds on fruit.”

Significance of the research

This discovery is significant for two main reasons. First, it had been thought that only E. jugularis could pollinate H. bihai and H. caribaea because the shape of their flowers fits the size and curvature of the hummingbird’s beak. 

Female E. jugularis, with their long, curved beaks, are the primary pollinators of H. bihai, while both male and female birds pollinate H. caribaea, despite males having shorter and straighter beaks.

Second, the findings demonstrate that species extinction and ecosystem dynamics are more complex than often assumed.

The destruction caused by Hurricane Maria disrupted the long-standing co-adaptation between the heliconias and their hummingbird pollinators, allowing other birds to take over. 

Crucial insights into resilient ecosystems

This suggests that evolutionary processes may not always follow a strict, linear path and can shift in unpredictable ways, especially in the context of the current climate crisis, where extreme events such as hurricanes, droughts, and floods are becoming more frequent, and species are at greater risk of extinction.

“If no other mass destructions occur on Dominica, we believe the two species of heliconia and E. jugularis may reestablish their exclusive mutualism in 15 to 20 years or so. The population of E. jugularis will have grown again, and there will be plenty of individuals defending their territory,” Gonçalves said. 

His team is continuing to conduct research in the area to test this hypothesis and assess how natural events affect evolutionary behaviors in other species. “We’re on the lookout for hurricanes in the region so we can go back there and investigate the consequences.”

This study provides crucial insights into the resilience and adaptability of ecosystems following natural disasters and raises new questions about how species interactions evolve in response to environmental changes.

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