Researchers at the Western Pacific Tropical Research Center at the University of Guam have documented what biologists call a "host shift" of the coconut rhinoceros beetle in Guam. The beetle, first documented as an invasive species in Guam in 2007, has been devastating the island's ubiquitous coconut palms and is now also burrowing into Guam's endangered native cycad tree, Cycas micronesica. The results were published in June in Volume 13 of the Communicative & Integrative Biology journal.
The fact that coconut palms were the second most abundant tree on the island prior to the beetle's invasion was one factor that enabled the beetle's explosive population growth. The sustained efforts to develop an effective biological control program have not been effective, allowing the pest to establish a foothold throughout the island.
"Our initial alarm after documenting the CRB burrowing activity on cycad trees was the fact that Guam's cycad species was actually the most abundant tree on the island only 20 years ago," said Irene Terry, one of the authors of the study. "Where else have the most abundant and second most abundant forest species been threatened by the recent invasion of one non-native herbivore?"
The authors used direct measurements of starch concentrations of the plant tissues to show that the island's heavily damaged coconut palms have declined in starch content so greatly that the host shift may have occurred in order to exploit the large doses of starch that are available in the cycad stems.
Read on: https://www.sciencedaily.com/releases/2020/09/200916113515.htm
This is very bad news.