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.
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.
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.
Determining if the small pine populations from TCI were genetically different from the larger and healthier Bahamas populations was key in deciding the future conservation strategy for the Caicos pine. As part of my PhD research (Sanchez, 2012), DNA samples I collected in both countries were analysed at Kew’s Jodrell Laboratory under the supervision of Mike Fay, and the diversity of the TCI ex situ collections was also assessed. Ten nuclear and plastid microsatellite markers were used to reveal past and recent gene flow among populations and to detect genetic differentiation and diversity.
Nuclear DNA revealed recent differentiation and genetic isolation of the TCI pine populations from those in the Bahamas and a strong correlation between genetic and geographical distance. Despite the 600km distance between populations in both regions, no genetic isolation was observed in plastid DNA, indicating high gene flow in the past. The ex situ collection was found not to be representative of the total gene pool for the taxon in TCI (Sanchez et al., 2014). Main recommendations for pine conservation in TCI were to maintain the island source in future re-introductions and improve genetic diversity of ex situ collections.
Mapping of the pine forests was used to estimate forest extent/size, to plan the data collection strategy, to look at potential plots for restoration and to develop access trails. The TCI pine forests were mapped by Susana Baena from Kew’s GIS Unit in 2008 and the Bahamas pine forests by me in 2008 to 2011 based on aerial photography/satellite imagery and ground truthing (Sanchez, 2012).
Permanent monitoring plots were set up in May 2010 with three on each island of Pine Cay, Middle Caicos and North Caicos for long-term monitoring of the scale infestation, testing control treatments and recording pine regeneration (Earle-Mundil, 2010). Research has detected a reduction in the abundance of native plants in the pine forests with the increase of pine mortality (Green, 2011) and indicated that broadleaf removal plus soap spray applications are currently the most effective treatment to control the insect infestation (Mark, 2012).
More than 200 pine trees were also planted out in six restoration plots established in 2012 and 2013 by DEMA, Kew's UKOTs team, and volunteers Bob McMeekin and Piotr Kaminski. Identification of potential pests and beneficial insects has been done by Chris Malumphy from the Food and Environment Research Agency (FERA) in the UK.
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.
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.
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.
The project, Caicos pine forests: mitigation against climate change and invasive species, is led by M. Hamilton, with my coordination and local management by B.N. Manco, and financially supported by the UK Government’s Darwin Initiative and the John Ellerman Foundation. It started this April, combining the expertise of Kew scientists and TCI partners to enhance scientific knowledge on the Caicos pine and expand the ex situ collections. Past and new data/experience will be combined to create protocols for the development of a strategy for safeguarding the future of the Caicos pine in TCI.
Research will include:
a) genetic analysis of the current ex situ collection and live trees in the monitoring plots
b) expanded sampling and ECM associations with other plant groups
c) chemistry of volatile compounds in healthy and infested trees and relation to pest resistance
d) seed viability and banking
e) growth conditions, improvement and maintenance of ex situ collections
f) mapping live seeding trees, current and predicted forest area
g) population viability analysis and forest restoration
This May the project will be officially launched in TCI during fieldwork by seven team members from Kew and local partners. Watch out for UKOTs blogs, the Caicos Pine Recovery Project Facebook page and UKOTs Twitter for news from the field.
- Michele -