FIG. 3. — Distribution of tree fern diversity in Madagascar. The number of collected taxa per grid cell of 0.25° × 0.25° is indicated on the varietal level and takes into account all currently recognized taxa of Cyathea sect. Alsophila (this treatment) and Cyathea sect. Gymnosphaera (Janssen & Rakotondrainibe 2007). This grid is superposed on a map indicating the remaining primary vegetation of Madagascar in dark green (DuPuy & Moat 1999) and outlining the bioclimatic regions of Madagascar according to Figure 2. All dark green areas in the humid and subhumid zones present high probabilities for the occurrence of Cyathea. Most specimens and hence most taxa have,however, been collected from the major mountain massifs and other well-known forests in the humid and subhumid zones (names indicated).