The species diversity of the genus Halimeda (Caulerpales, Bryopsidophyceae) in Indonesia and Papua New Guinea
Dargent, O.; Coppejans, E. (1998). The species diversity of the genus Halimeda (Caulerpales, Bryopsidophyceae) in Indonesia and Papua New Guinea. Biol. Jb. Dodonaea 65: 119-120
Beeckman, T.; Caemelbeke, K. (Ed.) (1998). Populations: Natural and manipulated, symposium organized by the Royal Society of Natural Sciences Dodonaea, University of Gent, 29 October 1997. Biologisch Jaarboek (Dodonaea), 65. Koninklijk Natuurwetenschappelijk Genootschap Dodonaea: Gent. 257 pp., more
The genera Halimeda and Caulerpa are the dominant algae (as well in biomass as in species richness) in numerous marine benthic ecosystems in the tropics. Moreover they can be important in monitoring these biotopes. The identification of Halimeda species remains difficult in spite of the existence of some monographs. This study clarifies the species delimitation in the area studied and proves the species richness in this contact zone between the Indian Ocean and the South Pacific Ocean. Morphological (prostrate, erect growth form, holdfast type, branching pattern, morphology of basal and upper segments, degree of calcification), anatomical (number, morphology and size of primary, secondary and tertiary utricles, eventual wall thickening of the utricles, eventual adhesion or fusion of utricles, type of fusion of the nodal filaments,) as well as ecological (soft or hard substrate, intertidal or subtidal, mangrove (channels), seagrass meadows, landward or seaward slope of the reef, reef pools, ...) data have been taken into account. They have been quantified and treated statistically as to objectively delimit the different taxa. Genetic analysis on central American representatives of this genus is actually carried out by Kooistra. Some species can be characterized morphologically as well as anatomically, others only morphologically (because of a very similar anatomy: H. micronesica and H. fragilis), others exclusively anatomically (becau- se of their morphological similarity: H. tuna and H. discoidea). This study results in the identification of 21 species sensu HILLIS- COLINVAUX (1980): 16 (+1) in Indonesia and 15 (+1) in Papua New Guinea. But according to our statistical analyses H. borneensis would be a growth form of H. simulans, and H. goreauii a growth forffi of H. minima. On the other hand a new taxon, related to H. macroloba, could be statistically isolated. This brings the actual number of species to 19, of which some have different growth forms, resulting in 22 taxa for the whole studied area (19 taxa in Indonesia and 16 taxa in Papua New Guinea) : H. copiosa, H. cylindracea, H. discoidea, H. distorta, H. fragilis, H. gracilis, H. lacunalis, H. macroloba, H. macrophysa, H. melanesica, H. micronesica, H. minima, H. opuntia, H. renschii, H. simulans, H. taenicola, H. tuna, H. velasquezii. The identification of 19 species of Halimeda in the melanesian region demonstrates 'the extreme species richness of this genus in this area. HILLIS-COLINVAUX ( 1980 : 90-91) mentions 23 species (including one of the synonymized species) for the whole Indo-Pacific. This species diversity is similar to that of the reefs between Cape York and Cooktown (Australia), with 18 species (DREW & ABEL 1985) and of the Fiji Islands with 16 species (N'YEURT & SOUTH 1996), hut is much higher than other so-called rich areas such as the Swains Reef complex (Australia) with 10 species (SAENGEN 1979, 1984), Madagascar with 13 species (FARGHALY 1980), or the area from Eniwetok Atoll to the Marshall Islands with 14 species (HILLIS-COLINVAUX 1980).
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