In my blog of October 11, 2018, I shared images and some information on various flora that are found on Bermuda and promised to talk about some of the species that have become invasive. You may wonder why invasive species on Bermuda might be relevant to us in Connecticut. Islands as small as Bermuda or as large as Australia may have species that are unique to their location and that have fewer defenses against introduced plants, animals, fungi, or microorganisms. These places are great concentrated studies in the effects of introduced species.
We have seen many invasive species become hot topics as they moved from other parts of North America or even other places on the planet into non-native locations in the Northeast. The Connecticut Invasive Plant Working Group lists over 80 plants that are currently problems, some of which moved into our region in just the course of a decade. Transported wood that is infested with the Emerald ash borer or the Asian longhorned beetle has enabled these insects to move easily from state to state.
Japanese barberry image, UConn Plant Database, EAB image, CT DEEP
The isolated volcanic islands of Bermuda were not subject to invasive species for most of its history. There were only 165 species of vascular plants, 5 species of bats, a species of skink and another of turtle on the islands when Bermuda was discovered. Over the next several hundred years thousands of plant and animal species were brought by ships to the islands, sometimes intentionally but more often not. Some came as stowaways as seeds in hay or soils, on ocean currents, as insects in food stores, or in the bilge water of the ships themselves.
Bermuda cedar (Juniperus bermudiana), Bermuda maidenhead fern (Adiantum bellum)
Until Bermuda was visited by the first Europeans in 1505 there had been no human-related importing of flora or fauna to the archipelago so it is a great microcosm of the effects of species introduction. When settlers come to a new place the first thing that they attempt is to make it ‘home-like’. The introduction of rabbits to Australia in 1788 by British penal colonies. Within ten years they numbered in the millions and ate enough vegetation to cause widespread erosion issues.
Rabbit around a waterhole, image from 1938/Australian National Museum
One of the first species introduced to Bermuda were the pigs that were released on Bermuda in the late 16th century. By the time a European settlement was established in the early 17th century the pigs had become abundant and feral. You may wonder why pigs were released in the first place. It was because the islands were used a place to replenish food and water, kind of a 17th century truck stop by ships. The pigs did untold damage to seabird and turtle breeding colonies.
Cockroaches, Periplaneta americana, came to Bermuda as egg cases in the bilges of a ship in 1621. Wireweed, Sida carpinifolia, was already a rampant invasive in 1669 when then-governor John Heydon was calling for tenants to pull it up by hand.
American cockroach (Periplaneta americana) egg case image
Many of the introduced species were brought in to control other species. The Jamaican anole, Anolis grahami, arrived in 1905 to control the Mediterranean fruit fly, Ceratitis capitata, and has since become naturalized. A beneficial introduction came in the form of honey bees, Apis mellifera. A beekeeping record dated May 25, 1617 stated that “The bees that you sent doe prosper very well.”. The Bermuda palmetto (Sabal bermudana), a native plant, is one of the main nectar sources for these bees. The giant Cane toad, Bufo marinus, an introduced species, was brought in to control garden pests but unfortunately consumes a lot of bees.
Honey bee, Bermuda palmetto, Cane toad
The Indian laurel, Ficus microcarpus, an ornamental garden tree was not considered an invasive species until the 1980s when a pollinating wasp was introduced to the island. Known as a strangler fig like its cousin the banyan, Ficus benghalensis, the Indian laurel can crack through walls and water tanks. It is a primary food source for the starling, an introduced species that does a lot of damage as they spread invasive seeds from the Brazilian pepper, Schinus terebinthifolia, the asparagus fern, Asparagus densiflorus, and the Indian laurel.
Indian laurel & banyan trees
Casuarina, Casaurina equisetifolia, over-shades native plant species and causes soil erosion. It was introduced from Australia in the 1940s as a windbreak but no plants grow beneath it. Kudzu, Pueraria montana, is familiar to Connecticut gardeners as it is also on the Connecticut Invasive Plant Working Group list.
Casaurina & kudzu
With 23 of the top 100 invasive species in the world, Bermuda is still at risk of additional invasive species as most of their food and consumer goods are brought in by ship. Visitors or traveling Bermudians also bring plants, fruits, and seeds on to the islands. When you travel anywhere in the world and see warnings about bringing back fruits and plants or prohibitions against moving wood, visiting farms, or petting livestock it is for the good of all to heed that advice.
Susan Pelton
Uconnladybug's Blog 