Diversity of Diplazium Based on Elevation

19

2.3.2. Diversity of Diplazium Based on Elevation

Table 2.3.. and Figure 2.2. show the diversity of Diplazium based on elevation. The species number of Diplazium culminate at 1000-1500 m. Amount of 19 species of Diplazium distribute at the elevation. Some studies on diversity across elevation Shmida Wilson 1985; Gentry Dodson 1987; Colwell Hurtt 1994 also reveal that peak diversity occur at intermediate elevations. Lomolino 2001 predicted that species-density should peak at an intermediate elevation and the peak should occur at transition zone between the two species- rich, juxtaposed communities. Because detailed information on climatic gradients, dispersal, population persistent and anthropogenic disturbance are generally unavailable, it is difficult to evaluate critically some of the predictions associated with causal explanation for peaks in diversity at intermediate elevations Lomolino 2001. Some species of Diplazium, such as D. atrosquamosum, D. beamanii, and D. squarrosum, are only occurring at upper elevation zones Table 2.3.. Above 3000 m, there was only found D. moultonii. Some scientists Kikkawa Wlliams 1971; Gentry Dodson 1987; McCoy 1990; Rahbek 1995 reported that speciation and endemicity peak at the intermediate to high elevations. Rahbek 1995 presumed that upper elevation zones may provide the geographical isolation required for speciation. If the montane zones are both isolated and large enough to allow population persistence and divergence over evolutionary time, they may represent hotspots of speciation and endemicity. Some species that presumed to be closely related have different in the range of distribution based on altitude. D. lobbianum and D. bantamense are presumed closely related. The two species share character combination as follow: scales toothed; fronds imparipinnate; pinnae oblong-ovate; vein free, forked, texture chartaceous. Ecologically D. lobbianum is found at 1500-1800 m, whereas D. bantamense usually below 1500 m. 20 Table 2.2. Diversity of Diplazium based on Elevation Elevation m Species 20- 500 D. accedens, D. acuminatum, D. aequibasale, D. angustipinna, D. bantamense, D. batuayauense, D. crenatoserratum, D. crinitum, D. hewittii, D. lomariaceum, D. pallidum, D. petiolare, D. polypodioides, D. porphyrorachys, D. riparium , D. tomentosum, D. wahauense, D. xiphophyllum 500-1000 D. accedens, D. acuminatum, D. bantamense, D.. cordifolium, D. crenatoserratum, D. cumingii, D. hewittii, D. hottae, D. laevipes, D. lomariaceum, D. pallidum, D. petiolare, D. poiense, D. polypodioides, D. simplicivenium, D. sorzogonense, D. tomentosum, D. umbrosum, D. xiphophyllum 1000-1500 D. accedens, D. asymmetricum, D. barbatum, D. cordifolium, D. crenatoserratum, D. cumingii, D. dilatatum, D. halimunense, D. hewittii, D. laevipes, D. lomariaceum, D. latisquamatum, D. moultonii, D. pallidum, D. petiolare, D. poiense, D. polypodioides; D. sorzogonense; D. tomentosum, D. tricholepis, D. umbrosum, D. velutinum, D. xiphophyllum. 1500-2000 D. atrosquamosum, D. barbatum, D. cordifolium, D. fuliginosum, D. latisquamatum, D. lomariaceum, D. moultonii, D. poiense, D. polypodioides, D. sorzogonense, D. speciosum, D. tricholepis, D. umbrosum, D. velutinum 2000-2500 D. atrosquamosum, D. barbatum, D. cordifolium, D. fuliginosum, D. latisquamatum, D. moultonii, D. sorzogonense, D. speciosum, D. tricholepis 2500-3000 D. cordifolium, D. fuliginosum, D. latisquamatum, D. moultonii, D. speciosum 3000-3400 D. moultonii The individuals with different ploidy level in the same species sometimes grow in the different altitude See Chapter 5. Diploid D. pallidum from Java, Borneo, and Sumatra were found at 200 m, 240 m and 30 to 85 m, respectively. Whereas the tetraploid ones were found at 1000 – 13000 m. Some closely related species may occur in overlapped distribution. D. insigne is evidently closely allied to D. accedens Holttum 1940. The two species share in characters: dull brown toothed scales with narrow thickening black strands, the deltoid deeply lobed apex of fronds and copiously goniopterid venation. The first species distributes from 600 m to 1200 m and the second species from 80 m to 1400 m. 21 Figure 2.1. a-b. Light shade-ferns of Diplazium. a. D. hottae; b. D. loerzingii; c-d. Deep shade-ferns. c. D. cordifolium; d. D. tomentosum. 5 10 15 20 25 0-500 501-1000 1001-1500 1501-2000 2001-2500 2501-3000 3000-3500 Elevation Range meter N umber of Spec ies Fig. 2.2. Elevational distribution of Diplazium species in West Malesia 22

2.4. Conclusions

Based on their main habitat, Diplazium can be divided into three major groups: dryland, riparian and rheophytic. Most of species are terrestrial dryland ferns and found at 20 – 3400 m above sea level in the primary and secondary forest on moist humus-rich soil in light and deep shady places 64 species. There are only found five of the riparian species, namely D. aequibasale, D. riparium, D. fuliginosum, D. lomariaceum, and D. porphyrorachis. The rheohytic species are found in D. aequibasale and D. wahauense. The most species number of Diplazium were culminated at 1000-1500 m. The lowest number of species occurred at 2500-3400 m. The individuals with different ploidy level in the same species sometimes grow in the different gradient habitats.