Velthorst, A.

Student Report

Abstract

The Caribbean is home to approximately 11,000 plants species, of which 72% are endemic to the region. However, the Caribbean has suffered from habitat loss and only 10% of the original vegeta- tion remains. Asclepiadoideae is the most diverse of the five subfamilies with most species endemic to the New World. Gonolobinae is a genus in the sub-family Asclepiadoideae with an estimated 100– 150 species occurring in the New World. Collections from St. Eustatius between 2008 and 2014 were amassed as part of an ongoing study of the vascular plant flora, and resulted in the discovery of a new endemic species; Gonolobus aloiensis. So far only three specimens have been collected. There- fore, very little is known about the phenology of G. aloiensis and how it is pollinated. Furthermore, little is known about the population size of G. aloiensis within its natural habitat, the evergreen sea- sonal forest of the dormant Quill volcano. Through a phased approach the aim of this research was to map all plants growing within the Quill crater and document the phenology, vitality and pollinators of G. aloiensis. Information about the dispersal and population size of G. aloiensis is crucial in order to be able to preserve this endemic plant species. A total of 264 plants were found in four months of searching the Quill crater. None of those were found in flower and/or fruit. However, the amount of rainfall in 2008 was three times as high as average, whereas in 2015 it was less than half. Significantly more individuals were found growing on the slopes than the relatively flat crater floor. Results suggest that individuals favour conditions on an incline compared with a relatively flat substrate. Over the study period, 54 of the 231 monitored plants died (23% mortality). On average, individuals grew 0.6 cm in total over a period of 6 weeks. Individuals that grew at lower elevations appeared to suffer less mortality or died later than those at higher elevations, possibly because of the amount of water available. There was no evidence of goat predation on G. aloiensis, despite the presence of goats within the crater, suggesting that goats may not present a threat to the species. Further research is necessary to better understand the processes and life cycle of this newly discovered species. 

Please contact STENAPA (research@statiapark.org)

Student report

Abstract

A reptile species that suffers from anthropogenic changes is Iguana delicatissima. This species was common on all Lesser Antillean islands from Martinique to Anguilla but since 1996 the species is vulnerable. Nowadays, however, the species only exists on St. Eustatius in the Dutch Caribbean. Native plant species might be dependent on I. delicatissima and its extinction could lead to biodiversity loss on St. Eustatius. Therefore it is important to gather as much data as possible on population size, feeding behaviour and habitat preferences, as well as create artificial nests. The information provided by this research can help the future conservation of I. delicatissima. Information about habitat preferences and feeding behaviour was documented. To create wooden artificial nests a literature study was used. A total of 128 individuals were located across the island during a secondary beading study, primarily next to roads. I. delicatissima were found in different trees and bushes and were documented eating invasive plants like Antigonon leptopus but also native plants such as Citharexylum spinosum. Earlier research on reptiles suggests that roadsides and surfaces attract reptiles for thermoregulatory purposes. Non-native plant species do not appear to have much influence on I. delicatissima. The 128 individuals located is below the recommended minimum viable population size of 5000 animals, however it is not currently possible to give an accurate population estimate from this study. There are a number of different threats to the population, such as free-roaming pets, habitat loss and habitat degradation. To conclude, more research is needed for the future conservation of I. delicatissima. 

Please contact STENAPA (research@statiapark.org)