Rescuing the threatened Caicos pine in the Turks and Caicos

The Caicos pine (Pinus caribaea var. bahamensis) also known as Caribbean pine, is the only native pine species of the Turks and Caicos Islands (TCI) and Bahamas. It is the dominant canopy species in the pine forests of this region and an important timber tree, but has undergone significant decline in recent years. The pine is a keystone species of the forests, supporting the diversity and functioning of this species-rich habitat, which is home to several threatened species, including Caroline’s pink (Stenandrium carolinae) and the TCI rock iguana (Cyclura carinata). The conservation and restoration of the Caicos pine forests is therefore vitally important for the biodiversity of these islands and for maintaining the associated ecosystem services.

The current and most damaging threat to the Caicos pine in TCI is the exotic invasive scale insect Toumeyella parvicornis (pine tortoise scale). The pest infestation resulted in the Caicos pine receiving Vulnerable status on the IUCN red list (Sanchez, Hamilton & Farjon, 2013). Scientific studies of the pine forests and a growing ex situ collection have been developed in recent years, but further scientific research is needed to guide future planning and restoration of the TCI pine forests. This will be undertaken as part of the new multidisciplinary Kew-led Darwin Plus project Caicos pine forests: mitigation against climate change and invasive species.

Background

The invasive pine tortoise scale insect was first recorded in TCI in 2005 by Martin Hamilton from Kew’s UK Overseas Territories (UKOTs) team. Since then, the infestation has spread to all TCI pine forests and killed most of the mature pine trees (Malumphy et al., 2012).

Crucial steps in rescuing and monitoring these pine trees in TCI and understanding the species' biology and ecological associations have already been taken in the past five years through collaborative work between Kew and TCI partners Department of Environment and Maritime Affairs (DEMA), Department of Agriculture (DoA) and TCI National Trust, among others.

Ex situ collections

Almost 500 pine trees are growing ex situ at the nursery on North Caicos, TCI, under the watch of DEMA’s staff, Bryan Naqqi Manco and Junel ‘Flash’ Blaise (pictured below showing the nursery to local school children and visitors). Another 90 seedlings are being cultivated by Marcella Corcoran from the UKOTs team in Kew’s Quarantine House, and 2,474 viable seeds are already banked in Kew’s Millennium Seed Bank at Wakehurst Place.

Prescribed fires

Natural low intensity fires occur mainly during the rainy season, May to October, and are important for pine forest regeneration, as pine seeds need open ground with enough light to germinate. However, non-seasonal fires, mostly human-induced, can burn at high intensity and kill trees and seedlings, as occurred in North Caicos in 2009 reducing local pine forest area by 91.5% (Sanchez, 2013). The presence of numerous dead pine trees and overgrown undergrowth increase the risk of future high intensity fires.

Prescribed fire under the guidance and supervision of Joe O’Brien, Ben Hornsby (US Forest Service) and David Grimm (Eglin Air Force Base, Florida, USA) was undertaken on Middle Caicos in three plots during May 2012 to investigate different treatments, fire intensity and pine survival.

Chemical compounds

In 2011-2012, Paul Green from Kew’s Sustainable Uses Group collected samples of pine needles and volatile compounds in TCI and Bahamas to analyse the chemical composition of healthy and infested trees, and to look for trends and local differences in tree resistance to pest attack. Initial data showed the presence of hundreds of compounds and variation in the levels of the major ten compounds in different islands.

Ectomycorrhizal fungi

Bryn Dentinger, Martyn Ainsworth and Laura Martinez-Suz from Kew’s Mycology Section investigated the presence of ectomycorrhizal fungi (ECM) in pine roots from the Bahamas and TCI. This mutualism between plants and fungi, essential in Pinaceae, becomes crucial in the early stages of pine seedling establishment and under adverse conditions such as drought and pest attack. 

In 2012, mycorrhizae collected from pine roots were identified through DNA sequencing at the Jodrell Laboratory. Four generalist ECM fungi and one pine specific, Rhizopogon sp., were detected. Knowledge on the ECM status of these pines and other co-occurring ECM plants will be important in restoration strategies.