An analysis of insect damage found on fossilized plant leaves reveals that Southern Hemisphere ecosystems recovered twice as fast as Northern Hemisphere ecosystems from the mass extinction event that wiped out the dinosaurs. The findings, reported in a paper published online this week as part of the first batch of content in the new journal Nature Ecology & Evolution, provide new insights into the ecological effects of mass extinctions, and the various impacts they had in different parts of the world.
The interactions between plants and insect herbivores are a crucial component of terrestrial food webs. Previous research has shown that in North America these interactions took nine million years to recover from the extinction event at the end of the Cretaceous period, which was caused by the impact of a large meteor at Chicxulub in Mexico approximately 66 million years ago. However, it has been suggested that the extinction event might have been less severe in the Southern Hemisphere, it serving as a refuge for species that went extinct in the Northern Hemisphere.
Michael Donovan and colleagues examined the diversity of insect-caused leaf damage at sites in Patagonia, Argentina, representing a period before and after the extinction event. Contrary to the refugium hypothesis, they find the extinction event was as severe in South America as in North America, with no evidence of individual insect species surviving it. However, they also find that ecosystem recovery was much faster in South America, with the full diversity of insect--plant interactions restored within only four million years (compared with nine million in North America).