Biological factors influencing production of xanthones in Aphloia theiformis.

Xanthones, and more specifically mangiferin, are molecules used in cosmetics for their photoprotective and anti-aging properties. The richness in xanthones of Aphloia theiformis leaves, a common shrub in Madagascar, can reach almost 12% (in relation to dry biomass). Amongst the A. theiformis studied, two major groups of individuals have been determined: those presenting a high proportion of mangiferin (up to 80% of the xanthones) and those presenting a high proportion of polar xanthones (not yet identified). Our study shows that: i) for each subject, the xanthone content remains stable over time (no seasonal variation); ii) the majority of the trees developing in the light belong to the first group (rich in mangiferin), whereas the individuals growing in the undergrowth are richer in polar xanthones; iii) the distribution of the two groups seems not to have any correlation with taxonomy and, moreover, with the known varieties of A. theiformis, although the micrantha variety is richer in mangiferin. Overall, this information indicates that A. theiformis is a reservoir of xanthones and makes it possible to define a framework for its reasoned management.

Deforestation and plant diversity of Madagascar's littoral forests.

Few studies have attempted to quantify the reduction or document the floristic composition of forests in Madagascar. Thus, we focused specifically on deforestation and plant diversity in Madagascar's eastern littoral community. We used a data set of approximately 13,500 specimen records compiled from both historical and contemporary collections resulting from recent intensive inventory efforts to enumerate total plant species richness and to analyze the degree of endemism within littoral forests. Change in littoral forest cover from original to current extent was estimated using geographical information systems tools, remote sensing data (satellite imagery and low-elevation digital photography), and environmental data layers. Of the original littoral forest only 10.3% remains in the form of small forest parcels, and only 1.5% of these remaining fragments are included within the existing protected-areas network. Additionally, approximately 13% of Madagascar's total native flora has been recorded from these forests that originally occupied <1% of its total land surface, and over 25% of the 1535 plant species known from littoral forests are endemic to this community. Given the ongoing pressure from human settlement along Madagascar's eastern coast, protection of the remaining forest fragments is critical for their survival. Fifteen of the largest intact littoral forest fragments we identified, collectively representing 41.5% of remaining littoral forest, are among priority sites recommended to the government of Madagascar for plant conservation and incorporation into the protected-areas network.