PECKIANA ·
Volume 4 (2005)
·
189 – 193
ISSN 1618-1735
Giant-pill millipede diversity on Madagascar (Diplopoda: Sphaerotheriida) THOMAS WESENER Abstract The collections of the California Academy of Sciences, the Field Museum of Natural History, Chicago, and new samples were examined for Malagasy sphaerotheriid species. Samples from 38 collection sites, all situated in main Malagasy ecosystems, included 80 sphaerotheriid species. This inventory at least doubles the number of known Malagasy sphaerotheriid species. The largest number of species was detected in the montane rainforest (23 species), whereas the littoral forest and spiny forest yielded the lowest number (8 species in each). Every ecosystem includes a high number of endemic giant-pill millipedes. The number of species occurring at only one site was exceptionally high (87.5 %). This study highlights the need for faunal inventories to focus on diplopod species in order to find invertebrate hotspots for conservation efforts.
1. Introduction Madagascar has a very rich and unique flora and fauna. It has been considered one of the eight biodiversity hotspots on our planet (Ganzhorn et al. 2001). The long isolation (Rabinowitz et al. 1983) and the diversity of its ecosystems are the two main factors causing the extraordinary richness of organisms seen nowhere else on earth. Unfortunately, the Malagasy millipedes are little known. A total of 160 species (123 endemic, Enghoff 2003) in 34 genera and 15 families are recorded from Madagascar to date (Enghoff 2003). Considering its diversity of biotas, it would be expected that Madagascar host a great number of Diplopoda species. One of the most conspicuous diplopod groups on Madagascar is that of the giant-pill millipedes of the order Sphaerotheriida. Members of this order have a number of conservative characters (with the exception of the ability to roll into a perfect ball). The Sphaerotheriida are represented on Madagascar by the endemic tribe Zoosphaerinii (Jeekel 1974) with the genera Zoosphaerium Pocock, 1895 and Sphaeromimus de Saussure & Zehntner, 1902. The main apomorphy of the tribe Zoosphaerinii is a stridulation organ on the male anterior telopods called »harp« (de Saussure & Zehntner 1897, 1902). The females possess a stridulation organ on the sub-anal plate, the »washboard« (Jeekel 1999). This washboard is also present in Indian Sphaerotheriida. The first results seem to indicate that the giant-pill millipedes on Madagascar are more species-rich than in other regions, representing the second largest order of diplopods on Madagascar after the Spirostreptida. Representatives of Sphaerotheriida have colonised the big island from the driest areas in the southwest on the Mahafaly plateau to the very wet eastern rainforests, from littoral forest to the mountains. With a mass of over 50 g,
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sometimes as large as an orange, Malagasy pill millipedes are much bigger than Sphaerotheriida anywhere else. They are possibly the heaviest diplopods. Because of their high diversity and large body size, giant pill millipedes play an important but completely understudied role in the processing of litter on Madagascar (Ashwini & Sridhar 2002, Lawrence & Samways 2003). This study presents preliminary findings regarding the habitat-specific richness of millipede species on Madagascar as can be deducted from available collection materials. The aim of this study is to provide an overview of giant-pill millipede diversity associated with different ecosystems. 2. Materials and methods The material studied for this paper was collected by S. M. Goodman (FMNH) and B. L. Fisher (CAS) during general conservation inventories that mainly focused on vertebrate and ant species and took place between 1995 and 2002. The specimens were borrowed from the FMNH and CAS and were collected using pitfall traps or sifted from leaf litter. The author gathered other materials by hand during an expedition to Madagascar in the Spring of 2003. This material will be deposited in the FMNH, and details of collecting sites will be published with taxonomic revisions. The original species descriptions (e.g. de Saussure & Zehntner 1897, 1902, Brölemann 1922, Jeekel 1999) were used to identify the material. Abbreviations: CAS
= California Academy of Sciences, San Francisco
FMNH
= Field Museum of Natural History, Chicago, USA
MNHN = Muséum National dHistoire Naturelle, Paris, France
3. Results As with millipedes in most regions of the world, the Malagasy millipede fauna is somewhat poorly known. Thirty-four sphaerotheriid species from Madagascar have been recorded (Jeekel 1999, Enghoff 2003). The vast majority of them were discovered between 1855 and 1904 (28 species, Tab. 1). Tab.1
Described Sphaerotheriida species from Madagascar.
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Examining the collections of the Field Museum, the California Academy of Sciences and newly collected material by the author yielded 80 Sphaerotheriida species from Madagascar. Collection sites, widespread throughout the island, include all four main ecosystems of Madagascar: spiny forests, dry forests, lowland forests and montane rainforests. Collections were also made in the eastern littoral forests, in gallery forests of rivers and in one mossy forest (Tab. 2). There were between four and six sampling sites per forest type with the exception of the mossy forest, where only one site was sampled. All ecosystems and most sites included endemic species, whose range appears to be restricted to the immediate area around the collection site, since they were not found at any other collecting site. Up to eight species occurred sympatrically in the same area. In one species tree climbing was observed, which might play a role in niche separation. The largest number of species recorded was in the montane rainforest, with 23 species, followed by the dry forest with 16 (Tab. 2). The other ecosystems yielded fewer species. There were ten in lower montane forests, nine in lowland forests/rainforests and nine in gallery forests. Still fewer species live in the littoral forests and in the spiny forests ecosystems with eight a piece. Every ecosystem hosts a great number of species restricted to that one ecosystem. The fewest endemic species (7 of 9, Tab. 2) occur in the gallery forest and in spiny and littoral forests (both 7 of 8, Tab. 2). The montane rainforest has the greatest number of endemic species (22 of 23). Tab. 2 Ecosystems, number of species, ecosystem-endemics and species occurring at one site only. At least 50 species, mainly from the genus Zoosphaerium, are undescribed.
The number of Sphaerotheriida species occurring at only one collection site is exceptionally high. Seventy of a total of 80 species were collected in a single limited area. Both results indicate that the species accumulation curve is far from levelling off, and that a large portion of Malagasy giant-pill millipede species remains to be discovered and described.
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4. Discussion It should be mentioned that faunal inventories of only 38 collection sites were the basis of these results. Most collection sites were only sampled during a short period of time (up to one week) using in the most cases no diplopod-specific collection techniques like hand collecting (Mesibov et al. 1995). A large number of areas, like in mountains at an elevation ofover 2000 m or the northwestern Sambirano region, have never been or have only in a few cases been the target of diplopod inventories. Furthermore, only two museum collections were considered for this study. More material is likely to be housed in some of the large millipede collections, such as the Muséum National dHistoire Naturelle, Paris or the Smithsonian Institute (see Sierwald & Reft 2004). Only a few of these collections are cataloged, and many millipede collections are not sorted or identified to the family or genus level, hampering access to the material. This study does, however, demonstrate the pivotal role museum collections play in biodiversity research and conservation biology. Other museums, especially French ones, might still keep an invaluable treasure of diplopod species in their collections. It can be predicted that the majority of giant-pill millipede species remain to be discovered. Furthermore, it is still unknown which kind of evolutionary processes have led to a radiation, so up to eight species of giant-pill millipedes might coexist in the same forest. As this study has shown, many diplopod species are micro-endemics (each species has only a small distribution), so they are very vulnerable to the destruction of their natural habitat. The proportion of micro-endemics is much higher than in South Africa, where more than 50 % of diplopod species are site-endemics (Hamer & Slotow 2002). The Malagasy Sphaerotheriida are no exception. Most of the giant-pill millipede species are only found at one collection site. These facts should motivate a fast inventory of Malagasy Diplopoda to find hotspots of invertebrate diversity before they become extinct. 5. Acknowledgements The author gratefully acknowledges the support and advice by Prof. Dr J.-W. Wägele. During fieldwork QIT Madagascar provided logistical support (arranged by J. B. Ramanamanjato). Collecting permits were procured by Dr Ravoahangimalala Ramilijona Olga (Department de Biologie Animale, Université dAntananarivo). Special thanks go to the Ministerie dEaux et Fôret, Antananarivo, for providing collection and export permits immediately. The author conducted the fieldwork on an expedition organized by Prof. Dr J. U. Ganzhorn (University of Hamburg). Thanks go to Dr Charles Griswold and Mr Darrell Ubick (California Academy of Sciences) and Dr Petra Sierwald (Field Museum of Natural History, Chicago) for the loan of material. Special thanks go to Dr Christian Schmidt for his continuous advice throughout the study. Dr Petra Siewald provided useful comments on a preliminary version of this paper. The very useful comments of Dr Karin Voigtländer and Dr Michelle Hamer are gratefully acknowledged.
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6. References Ashwini, K. M. & K. R. Sridhar (2002): Towards organic farming with millipede Arthrosphaera magna. Curr. Sci. (Bangalore) 82 (1): 20 22 Brölemann, H. W. (1922): Liste des myriapodes de lAcademie Malgache de Tananarive. B. Soc. Zool. Fr., Paris 47: 223 248 de Saussure, H. & L. Zehntner (1897): Atlas de lhistoire naturelle des Myriapodes. In: Grandidier, G. (ed.): Histoire physique, naturelle et politique de Madagascar, Paris, 27 (53): pl. 1 12 (1902): Myriapodes de Madagascar. In: Grandidier, G. (ed.): Histoire physique, naturelle et politique de Madagascar, Paris, 27 (53): i viii, 1 356, pl. 13 15 Enghoff, H. (2003): Diplopoda, Millipedes. In: Goodman, S. M. & J. P. Benstead (eds): The Natural History of Madagascar. University of Chicago Press: 617 627 Ganzhorn, J. U., P. P. Lowry II, G. E. Schatz & S. Sommer (2001): The biodiversity of Madagascar: one of the worlds hottest hotspots on its way out. Oryx 35 (4): 346 348 Hamer, M. L. & R. H. Slotow (2002): Conservation application of existing data for South African millipedes (Diplopoda). Afr. Entomol. 10 (1): 29 42 Jeekel, C. A. W. (1974): The group taxonomy and geography of the Sphaerotheriida (Diplopoda). Symp. Zool. Soc. London 32: 41 52 (1999): A new pill-millipede from Madagascar, with a catalogue of the species hitherto described from the island (Diplopoda, Sphaerotheriida). Myriapod Memoranda 1: 5 20 Lawrence, J. M. & M. J. Samways (2003): Litter breakdown by the Seychelles giant millipede and the conservation of soil process on Cousine Island, Seychelles. Biol. Conserv. 113: 125 132 Mesibov, R., R. J. Taylor & R. N. Brereton (1995): Relative efficiency of pitfall trapping and handcollecting from plots for sampling of millipedes. Biodiv. Conserv. 4: 429 439 Pocock, R. I. (1895): Description of new genera of Zephronidae, with brief preliminary diagnoses of some new species. Ann. Mag. Nat. Hist. 16: 409 415 Rabinowitz, P. D., M. F. Coffin & D. Falvey (1983): The separation of Madagascar and Africa. Science 220: 67 69 Sierwald, P. & A. J. Reft (2004): The Millipede Collections of the World. Fieldiana Zoology, new series, 100 pp.
Authors address: Thomas Wesener Department of Animal Morphology & Systematics Ruhr-University Bochum Universitätsstr. 150 44801 Bochum, Germany e-mail:
[email protected]
