Insects and invasives: investigating threats to Turks and Caicos Islands plants
The native plants of the Turks and Caicos Islands (TCI) are under increasing threat from plants and animals that have been introduced to these Caribbean Islands in recent years. In an effort to understand the biology of the invasive species, a team of Kew botanists and conservationists spent three weeks studying them and investigating the problems they cause.
One of the goals of the expedition was to assess effects of the pine scale insect (Tourmeyella parvicornis), which has all but wiped out the national tree of TCI, Pinus caribaea var. bahamensis.
Pine scale insect is killing the pine trees on TCI
This tree grows in both TCI and the Bahamas; however, in the Bahamas the scale insect does not cause major problems at present. Martin Hamilton and Paul Green (RBG, Kew) began by visiting the islands of Abaco and New Providence in the Bahamas to collect pine chemical extractions and pine insect pest samples for identification.
Collecting pine samples in the Bahamas
Martin and Paul then travelled to TCI to meet Marcella Corcoran (RBG, Kew), Sara Green, and Alexandra Davey (Imperial College Conservation Science MSc students).
In the Bahamas the team worked in collaboration with staff from Bahamas National Trust (BNT) in the field and provided practical experience and hands-on training for relevant staff. In TCI, the team continued with its collaboration with the Department for Environment and Coastal Resources (DECR) to record, monitor and conserve the flora of TCI, and continue activities related to the Caicos Pine Recovery Project (CPRP).
We know that from previous chemical analyses of dried pine-needle samples that there are different chemicals in extracts of healthy and insect-infested pine. It became clear that extracts of fresh material would be needed for comparison. In the Bahamas samples were collected from healthy trees, and from trees stressed by salt-water flooding and fire. TCI samples were collected from trees with very varied levels of pine scale insect infestations. These will enable us to look for differences in chemistry resulting from various stresses and insect infestation. We can speculate that there is a link between the level of stress to which the trees are exposed and their susceptibility to insect attack.
Preparing extracts of pine needles
The extracts prepared during this trip will be analysed in the laboratories of the Sustainable Uses of Plants Group (Jodrell Laboratory, RBG, Kew). These analyses will allow us to look at differences in the compounds present in the healthy, healthy and fire damaged, and stressed trees. With additional pine-needle extracts prepared in TCI, we will be able to compare the extracts of Bahaman pines with TCI pines suffering from severe insect infestation. Chemical differences could explain why the TCI pines are severely infested with insects, while it is difficult to find insects in significant number on the pines on Abaco. The pines on New Providence are exposed to environmental stress and they also show frequent insect damage which does not appear to significantly affect the health of the trees at the moment.
Getting to grips with Casuarina invading the beaches
In addition to this work the two students from Imperial College MSc carried out research for their MSc dissertations. Sara Green collected data for the second year of a project recording a series of permanent monitoring plots in the TCI pine forests to assist the CPRP. She also monitored other species growing within the pine yards. Alexandra Davey started her project to map the invasive plant Casuarina equisetifolia and recommend areas for control of the species and assess its potential use as a charcoal source.
- Martin -