Infrageneric Relationships and the Origin of the Hawaiian Endemic Genus Lipochaeta (Compositae)

Infrageneric relationships of Lipochaeta were assessed by way of a controlled crossing program that produced 14 intrasectional and 5 intersectional hybrid combinations involving the two sections Aphanopappus and Lipochaeta. Results from uniform culture and hybridization studies confirm that specific differences involving many traits such as leaf shape, the number of disk floret lobes, and achene morphology have a genetic basis. Fertility data based on pollen stainability and achene set of some of the hybrids revealed that members of the same section are highly interfertile, whereas the two sections are extremely well isolated from each other reproductively. Cytogenetic evidence suggests that this isolation is due primarily to a difference in the ploidy level of the two sections and that section Lipochaeta, with n = 26, has an allopolyploid origin from a IS-paired taxon similar to a diploid Lipochaeta and an unknown II-paired taxon in the extra-Hawaiian genus Wedelia. Chromosome counts for three diploid species and one tetraploid variety are reported for the first time

Patterns of Loss and Regeneration of Tropical Dry Forest in Madagascar: The Social Institutional Context

Loss of tropical forests and changes in land-use/land-cover are of growing concern worldwide. Although knowledge exists about the institutional context in which tropical forest loss is embedded, little is known about the role of social institutions in influencing regeneration of tropical forests. In the present study we used Landsat images from southern Madagascar from three different years (1984, 1993 and 2000) and covering 5500 km(2), and made a time-series analysis of three distinct large-scale patterns: 1) loss of forest cover, 2) increased forest cover, and 3) stable forest cover. Institutional characteristics underlying these three patterns were analyzed, testing the hypothesis that forest cover change is a function of strength and enforcement of local social institutions. The results showed a minor decrease of 7% total forest cover in the study area during the whole period 1984–2000, but an overall net increase of 4% during the period 1993–2000. The highest loss of forest cover occurred in a low human population density area with long distances to markets, while a stable forest cover occurred in the area with highest population density and good market access. Analyses of institutions revealed that loss of forest cover occurred mainly in areas characterized by insecure property rights, while areas with well-defined property rights showed either regenerating or stable forest cover. The results thus corroborate our hypothesis. The large-scale spontaneous regeneration dominated by native endemic species appears to be a result of a combination of changes in precipitation, migration and decreased human population and livestock grazing pressure, but under conditions of maintained and well-defined property rights. Our study emphasizes the large capacity of a semi-arid system to spontaneously regenerate, triggered by decreased pressures, but where existing social institutions mitigate other drivers of deforestation and alternative land-use

Chromosome Numbers of Madagascar Plants

Volume: 74Start Page: 123End Page: 12

Conservation of Madagascar’s granite outcrop orchids: the influence of fire and moisture

Quelle est la réponse aux perturbations, et la limitation de l’humidité, par des taxons similaires basés sur l’hétérogénéité des micro-site de l’habitat? Pour cette étude nous avons examiné comment la disponibilité de feu et de l’humidité influence la répartition des orchidées endémiques malgaches spécifique des affleurements de granit (inselbergs). Trois ans après le passage du feu, nous avons compare les modes de distribution et l’abondance d’orchidées dans un habitat d’une mosaïque complexe de brûlures, en tenant compte de la densité par rapport à l’intensité des dégâts d’incendie et de la disponibilité de l’humidité. Les espèces du sous- tribu Angraecinae ont été sensibles au feu, mais tolérant à une disponibilité limitée de l’humidité. orchidées Angraecinae avait un modèle uniforme de la distribution influencée par la taille du tapis de végétation. Les espèces de la sous-tribu Habenariae étaient tolérants de feu, mais limitée aux pentes rocheuses humides par des écoulements d’eau. Habenariae ont été randomizes regroupés en masses compactes, influencée par des facteurs non encore identifiés. Les résultats suggèrent l’existence de différentes stratégies de survie des espèces. Il serait inexact de penser que les orchidées voisins sur un substrat de granite aurait la même réponse à des facteurs environnementaux ou de perturbation. orchidées Angraecoid sur les inselbergs sont exposés à des menaces spécifiques et doivent être considérées comme des espèces indicatrices de la conservation est prioritaire à l’avenir. Is there a difference in response to disturbance, or resource limitation, by similar taxa based on micro-site habitat heterogeneity? For this study we examined how fire and moisture availability influences the distribution of terrestrial and lithophytic orchids specific to Madagascar’s granite outcrops (inselbergs). We compared orchid density in an area with a complex mosaic of burned and non-burned vegetation patches (three years after the event). Lithophytic species (subtribe Angraecinae) were sensitive to fire, but tolerant of limited moisture availability, and had a uniform distribution pattern associated with vegetation mat size. In contrast, most terrestrial species (subtribe Habenariinae) were not impacted by fire, but were limited to slopes with high water seepage, and had a clumped distribution pattern. The results suggest varying ecological niches between orchid subtribes, and among species, occurring on shared substrate. Within the larger area, we also compared three inselbergs with different fire disturbance history. One site with potential for lightning based fires, but absence of anthropogenic fires, had the greatest diversity (subtribes, genera, and species) of orchids and the highest occurrence of species restricted to a single site. For land management purposes it is inappropriate to assume that inselberg specific orchids will have the same response to environmental stressors. Angraecinae orchids are especially at risk from human associated fire disturbance and should be regarded as indicators for future conservation efforts.

Figure 2

<p>Pictures from the four surveyed areas a) degraded/thinned forest (Area I), b) regenerating forest (Area II), c) stable forest (Area III), d) forest patch protected by local taboos (Area IV). Pictures taken in January 2005.</p

Figure 1

<p>The Androy region is situated in the southernmost part of Madagascar between Lat 24°13′ and 25°24′S and Long 45°20′ and 46°26′ E. Four areas (I–IV) were selected for detailed field investigations. Yellow squares with numbers indicate plots used in ground truthing.</p

Figure 4

<p>In the NDVI analysis (Normalised Difference Vegetative Index), the dense mature forests show multiple peaks due to differences in species composition, the regenerating forest is separated with lower NDVI values, while degraded forest and open land has distinctly different patterns. The examples given here are subsets (1.5×1.5 km) from the 2000 Landsat 7ETM+image.</p