AsianScientist (Nov. 11, 2016) – Just three species of non-native herbivorous insects were enough to reduce the population of a tree species native to Guam by 90 percent within a decade, according to a study from Guam that was published in Communicative & Integrative Biology.
The island of Guam is home to a native cycad species called Cycas micronesica, which was the most abundant tree species on the island until the invasions of three non-native cycad herbivores: the cycad blue butterfly, the cycad aulacaspis scale, and a leaf miner.
According to the findings by Drs. Thomas Marler and Nirmala Dongol from the University of Guam, all three non-native insect herbivores caused changes in the cycad tree’s leaf chemistry following herbivory damage, and the population of the vulnerable plant was reduced by more than 90 percent within the first decade of damage.
The three herbivores come from highly disparate feeding guilds, so the authors predicted that changes in leaf chemistry would not be similar following herbivory. The experimental results proved the predictions correct, as no consistent pattern was observed among the various chemical traits that were quantified. However, the results revealed that herbivory by all three of the insects modified leaf chemistry in ways that speed up litter decomposition, which predicts profound changes in nutrient turnover rates as a result of the invasions. The research also revealed that non-native invaders may change properties at the level of the ecosystem.
“All of the elements that serve as nutrients for soil-borne decomposing organisms were altered by the invasive herbivores,” said Marler. “In addition, secondary compounds that are known to influence speed of leaf litter decomposition were also changed following the herbivory.”
The article can be found at: Marler and Dongol (2016) Three Invasive Insects Alter Cycas Micronesica Leaf Chemistry and Predict Changes in Biogeochemical Cycling.
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Source: University of Guam; Photo: Shutterstock.
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