Abstract
Clearing of forest land for agriculture and urbanization following colonization have reduced the forest cover in Mauritius to 3% of total land cover. Today exotic species such as Psidium cattleianum (wild guava), Araucaria columnaris, and Ravenala madagascarensis dominate at Pigeon Wood, the only site in Mauritius where Beclardia can be found, leaving little space for very few indigenous tree species like Labourdonnaisia glauca, Apholoia theiformis and Foetida mauritiana. Beclardia macrostachya is an orchid endemic to Mauritius, Madagascar andReunion. Though it is abundant in the latter countries, it is one of the rarest orchids in Mauritius. An assessment of the factors associated with the stability of this orchid was carried out in forests of these three countries to understand the drastic decline of this orchid in Mauritius. Morphometric and fertility counts carried out at different forests revealed differences in fitness and fertility rates among forests of the same countries and between different countries. Stability of the different Beclardia populations was carried out based on counts of juveniles and adults. Higher fertility rates and most stable populations were observed in the forests of Reunion Island (Bebours) and Madagascar (Ambohitanteley), whereas very low fruit set were observed in Mauritius, unless manual pollination was carried out. Microscopic analysis revealed the presence of pelotons of endomycorrhiza during the early development of the seedlings, in vivo. Based on comparative studies among the different sites, pollinator limitation and absence of suitable hosts were the primary factors that led to the present decline in Mauritius. The high density of wild guava, Psidium cattleianum, which has slowly taken up most of the forest areas inMauritiushas affected the regenerating capacity of Beclardia macrostachya and the density of putative hosts of this orchid. GC-MS/MS analysis of nectar revealed α-D- glucopyranose to be the primary reward of the pollinators and benzyl alcohol, methoxybenzyl alcohol and methoxy methyl phenol to be components floral fragrance.
Highlights
Beclardia macrostachya, is one of the rarest orchid in Mauritius
This study focused on five main criteria for the assessing the biology of this orchid: 1) Population dynamics—Population census gives relevant data about the existing populations, and successive census data can be used to assess the population tendencies
Of the other aromatic compounds detected in Beclardia macrostachya, methoxybenzyl alcohol and methoxy methyl phenol are reported to be a component of floral scents in orchids [37]
Summary
Beclardia macrostachya, is one of the rarest orchid in Mauritius. Such a low population of this orchid requires urgent measures to develop conservation strategies for propagation. Before starting any conservation strategy certain biological factors that govern the growth of the target taxon should be evaluated such as spatial distribution of diversity, ecological relationships, altitude, rainfall levels, and even human factors such as movements that leads to disturbed habitat. Assessments should be carried out in the different populations present at different localities to study the changes that are occurring and the significance of these changes in terms of viability, performance and survival of the species. Optimal conditions for stable populations can be evaluated, and artificial simulations created for conservation of the species. This study aimed at defining the different factors affecting the stability of the Beclardia macrostachya populations and conse-
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