Working alongside high-resolution satellite imaging technology, researchers from Brown University in addition to the University of California, Los Angeles receive got uncovered novel clues inwards an age-old query most why tropical forests are then ecologically diverse.
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| In this photograph of the tropical pelting wood canopy inwards Panama, Handroanthus guayacan, the focus of a novel Brown/UCLA study, blooms inwards yellowish piece Jacaranda copaia has bluish flowers in addition to Cavanillesia plantanifolia has pinkish fruit. Taking payoff of regular annual changes, similar flowering in addition to fruiting, allowed Brown ecologist Jim Kellner to runway private trees through fourth dimension in addition to map distributions of or then species throughout a large area [Credit: Jonathan Dandois in addition to Helene Muller-Landau/Smithsonian Tropical Research Institute] |
"There are to a greater extent than tree species living inwards an surface area non much larger than a few football game fields inwards Panama than inwards all of North America northward of United Mexican U.S.A. combined," said Jim Kellner, start writer on the newspaper in addition to an assistant professor of ecology in addition to evolutionary biological scientific discipline at Brown. "How this variety originated, in addition to why it persists over fourth dimension is a paradox that has challenged naturalists for to a greater extent than than a century."
Until now.
"The take-home of the written report is that at that spot is a 'negative feedback' on population growth," Kellner said, which puts the brakes on population growth inwards locations where the species is common.
The findings confirm a prediction from the 1970s, which posited that tropical forests are various because natural enemies proceed populations inwards check. An enemy could last a seed eater, an plant eater or a pathogen, said Kellner, who is affiliated alongside the Institute at Brown for Environment in addition to Society.
For example, consider an oak tree in addition to a squirrel. The squirrel eats acorns in addition to prefers to provender where oak trees are abundant. Influenza A virus subtype H5N1 solitary acorn inwards the middle of a grove of maples is probable to move unnoticed past times a squirrel, whereas many acorns inwards an oak grove volition last eaten. If this sort of demeanour is widespread inwards tropical rainforests, it could proceed species from becoming besides common, Kellner said.
Earlier studies receive got shown that this negative feedback phenomenon holds truthful amidst immature trees -- seeds, seedlings in addition to saplings -- but ecologists hadn't been able to create upward one's ask heed whether it influences adult trees, the reproductive constituent of populations, he said.
"It takes decades for trees to move reproductive inwards tropical forests, in addition to the employment is compounded past times how rare each species is," Kellner said. "We flora that for this species, you lot would receive got to search most 250 acres to let on i novel adult tree every year."
That challenge isn't viable on foot, but remote sensing tin overcome the challenges of observing large areas.
Kellner in addition to co-author Stephen Hubbell, an ecology professor emeritus at UCLA, used high-resolution satellite images to runway individuals on Barro Colorado Island, a six-square-mile isle inwards the middle of the Panama Canal, over 10 years. They looked for Handroanthus guayacan, a tropical rainforest tree that produces vivid yellowish flowers for a few days a year.
"By timing the satellite ikon acquisition alongside seasonal flowering, nosotros were able to position most of the adults for this species on the island," said Kellner.
They flora 1,006 adult trees. Starting inwards 2012 in addition to looking backward over the 10-year written report period, Kellner in addition to Hubbell were able to position when novel trees joined the adult population for the start time. They used advanced statistical methods to brand certain that they were inwards fact identifying novel adults in addition to non only trees that had skipped a twelvemonth of flowering or had flowered early on or late.
The researchers flora that negative feedback affected the abundance of novel adult trees in addition to that it tin influence the population of novel adult trees inwards an surface area of almost 100 football game fields. This contrasts alongside prior studies of juvenile trees, which flora the effects of host-specific enemies are unremarkably restricted to pocket-size areas, Kellner said.
To confirm the locations of trees from the satellite data, they went to the isle in addition to independently flora 123 adult trees of the same species. Of these, 89 pct had been detected inwards the high-resolution images, suggesting that their information are a nearly consummate census of the species.
Kellner said the implications could last broad.
"I can't remember of whatever stance inwards ecology that is to a greater extent than of import than population dynamics," he said. "It's of import for everything from line-fishing licenses to forecasting illness outbreaks."
The written report is published inwards the Proceedings of the National Academy of Sciences.
Source: Brown University [October 15, 2018]
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