Research Article |
Corresponding author: Sergei Golovatch ( sgolovatch@yandex.ru ) Academic editor: Ivan H. Tuf
© 2015 Sergei Golovatch.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Golovatch SI (2015) Cave Diplopoda of southern China with reference to millipede diversity in Southeast Asia. In: Tuf IH, Tajovský K (Eds) Proceedings of the 16th International Congress of Myriapodology, Olomouc, Czech Republic. ZooKeys 510: 79-94. https://doi.org/10.3897/zookeys.510.8640
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The diversity of Diplopoda in caves of southern China is remarkably high, often 5–6 species per cave, consisting mostly of local endemics and presumed troglobionts. These are evidently biased to just a few lineages, mainly members of the orders Chordeumatida and Callipodida, the families Cambalopsidae (Spirostreptida) and Haplodesmidae (Polydesmida) or the genera Pacidesmus, Epanerchodus and Glenniea (all Polydesmida, Polydesmidae), Trichopeltis (Polydesmida, Cryptodesmidae), Dexmoxytes (Polydesmida, Paradoxosomatidae) and Hyleoglomeris (Glomerida, Glomeridae). All these taxa, especially the Paradoxosomatidae and Cambalopsidae (usually amounting to about 60% and 10% of the total species diversity in the Oriental fauna, respectively), are moderately to highly speciose across Southeast Asia, being largely epigean. However, the epigean Diplopoda of southern China are yet badly understudied, since much of the collecting and taxonomic exploration efforts still focus on cavernicoles. The Oriental Region is the only biogeographic realm globally that harbours all 16 orders of Diplopoda, of which 14 have already been encountered in China and/or the immediately adjacent parts of Indochina. Thus, China may actually prove to support no less than 1,000 millipede species of various origins, mainly Oriental and Palaearctic.
Millipede, fauna, richness, cavernicoly, China, Oriental realm
The class Diplopoda, or millipedes, is among the largest of the terrestrial arthropod groups globally, with about 8,000 described species in nearly 1,900 genera, 147 families and 16 orders (
Diplopods are largely detritivores, only a few species can be considered omnivores, even fewer as carnivores. The environment that can be postulated as the most typical of the Diplopoda as a whole is temperate (especially deciduous), subtropical or tropical forest (in particular, humid ones). The most typical habitats are leaf litter, the litter/soil interface, the uppermost soil, and dead wood. Being mainly hygro- to mesophilous, millipedes tend to be absent from or only marginal in most of the extreme habitats such as tundra or desert (
Several basic millipede morphotypes are known: polyxenoid (Polyxenida), glomeroid (Glomerida and Sphaerotheriida), juloid (virtually all Juliformia), polydesmoid (Polydesmida, some Chordeumatida) and platydesmoid (Colobognatha). Similarly, five life-forms, or ecomorphotypes, have been delimited in millipedes (
Figure
Main trends in the ecological evolution of Diplopoda. All are life forms except for arboricoles. 1 stratobionts 2 trunk and crown arboricoles, as well as subcorticolous xylobionts 3 epiphytobionts 4 troglobionts 5 geobionts. NB: The thickness of numbered arrows roughly corresponds to the share of the respective ecological grouping along a gradient of biome succession with age (uppermost arrows, the gap between them indicates the primary subtropical biome whence developed all the main extant biomes). After
To summarize, only a few millipede life-forms can be distinguished. Diplopoda as a group of soil/litter macrofauna are somewhat to markedly sensitive to water deficit and are often calciphilous as well. In general, they appear to have failed, both morphophysiologically and ecologically, to conquer environments and habitats significantly deviating from a forest floor (
Speaking of the Diplopoda, Southeast Asia is the only biogeographic region globally that supports all of its 16 orders (
The following examples illustrate the declining millipede orders Siphoniulida and Siphonocryptida, neither reported from continental China yet.
All 2–3 species of Siphoniulida are only known from Sumatra (1) and Mexico+Guatemala (1–2). The pattern demonstrated by the Siphonocryptida is also quite peculiar. This small order contains two genera with three species in each. Hirudicryptus Enghoff & Golovatch, 1985 has a species living on Madeira and the Canaries, where it is largely confined to the relict laurisilva biome, one species from a 2500 m elevation in Nepal, and one from Taiwan. Siphonocryptus Pocock, 1894 contains one species from Sumatra, Indonesia, and two from the southern half of Malay Peninsula. Such patterns seem to date back at least to the Oligocene times of the so-called “Warm Earth” and have firm causal explanations (
Faunistic records in southern China (not only of Diplopoda, but of many other arthropod groups) appear to be strongly biased towards caves; many if not most of the species are suspected or confirmed troglobionts, often with up to 5 or 6 troglomorphs per cave, for example in the Mulun Karst in Guangxi which hosts perhaps the richest cave fauna at least in China (
The cave millipedes of Southeast Asia, including the adjacent areas of southern China, in contrast to their epigean faunas, appear to be strongly biased and restricted to rather few lineages. In other words, even though the Oriental Region does support perhaps the richest and most diverse diplopod fauna globally (Table
Millipedes of Southeast Asia (and the world) versus those in southern China.
Orders | Distribution pattern | Troglobionts |
Polyxenida | Cosmopolitan | very few troglobionts, but none in E & SE Asia |
Glomeridesmida | Pantropical | very few troglobionts, but none in E & SE Asia |
Glomerida | Holarctic + Oriental | numerous troglobionts, including E & SE Asia |
Sphaerotheriida | Old World | no troglobionts |
Siphoniulida | Neotropical + Oriental | no troglobionts |
Siphonophorida | Pantropical | no troglobionts |
Siphonocryptida | Palaearctic + Oriental | no troglobionts |
Polyzoniida Platydesmida | Subcosmopolitan | no troglobionts |
Chordeumatida | Holarctic + Neotropical + Oriental | no troglobionts |
Callipodida | Subcosmopolitan, but mainly Holarctic | numerous troglobionts, including E & SE Asia |
Stemmiulida | mainly Holarctic + Oriental | rather few troglophiles, but hardly any true troglobionts, which are mostly restricted to SE Asia |
Julida | Pantropical | no troglobionts |
mainly Holarctic + Oriental | numerous troglobionts, including E Asia, but excluding SE Asia | |
Spirostreptida | Pantropical | numerous troglobionts, including E & SE Asia |
Spirobolida | Pantropical | very few troglobionts, but none in E & SE Asia |
Polydesmida | Cosmopolitan | numerous troglobionts, including E & SE Asia |
Biogeographically, the millipede fauna of southern China, including cavernicoles, is clearly dominated by Oriental elements, whereas the influence of the Palaearctic is low. Such a pattern fully agrees with common wisdom. The same concerns the obvious preponderance of troglobitic Diplopoda to particularly local endemism, mostly restricted to a single cave or cave system, even as compared to the low-vagile and also mostly highly locally distributed epigean counterparts (
The most common, often also highly abundant group clearly dominating the cave millipede fauna of Southeast (and partly South) Asia is the family Cambalopsidae (Spirostreptida). The most speciose genera are Glyphiulus Gervais, 1847 (
The huge, Eurasian, basically warm-temperate to tropical genus Hyleoglomeris Verhoeff, 1910 (Glomeridae, Glomerida) currently contains nearly a hundred species, including at least two dozen cavernicoles. Unlike the glomerid fauna of the adjacent Indochina which harbours a considerable proportion of endemic genera (60% in Vietnam, see
Species of the large order Chordeumatida dominate the Holarctic, being much more subordinate in Australasia (including southern India and Sri Lanka in the West, through Malay Peninsula and Indonesia, to tropical and subtropical eastern Australia and New Zealand), Madagascar (absent from the remaining Afrotropical areas), Central America (only north of Panama) and South America (only Chile). In Southeast Asia together with the adjacent areas of southern China, the fauna is restricted to a few genera only. The most important is Nepalella Shear, 1979 (Megalotylidae), with 23 species or subspecies from Nepal (10), Thailand (2), Myanmar (2), Vietnam (1) and southern China (8, several presumed troglobionts, e.g. Figs
The rather small, mostly Holarctic order Callipodida is represented in the Oriental realm by 3–4 genera and three families. Perhaps the most interesting is Sinocallipus Zhang, 1993, with six described species, largely cavernicolous, from Indochina and the adjacent parts of southern China (
Hardly surprisingly, the order Polydesmida, which is the largest globally, is also the most diverse in the Oriental Region. However, only a few families are represented in caves while even fewer seem to comprise troglobionts. The most common is the principally Holarctic family Polydesmidae only marginally represented in tropical Asia, reaching Indochina in the South. Two polydesmid genera dominate the fauna of China and adjacent areas, showing lots of cavernicoles as well. Thus, Epanerchodus Attems, 1901 is the largest genus of Polydesmida in Central to East Asia, including southern China. Altogether it contains 70+ species, mainly in Japan from where numerous troglobionts are known. Only 17 species of Epanerchodus have hitherto been recorded in mainland China (
Habitus photos of Pacidesmus armatus Golovatch, Geoffroy & Mauriès, 2010, Desmoxytes scolopendroides Golovatch, Geoffroy & Mauriès, 2010, Eutrichodesmus filisetiger Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2009, and E. aster Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2009, all presumed trogloionts from Guangxi, Guangxi, Vietnam, and Vietnam, respectively. After
The family Paradoxosomatidae (Polydesmida) is among the largest in the entire class Diplopoda (nearly 200 genera and >950 species, amounting to about 60% of the total species diversity in the Oriental fauna), but it is highly uncharacteristic of caves. Like the Cambalopsidae (probably another 10% of the total species richness of Oriental Diplopoda), the Paradoxosomatidae are largely epigean, in part because much of the collecting and taxonomic exploration efforts still focus on cavernicoles alone. Only the large (35 species, mainly epigean), basically Southeast Asian genus Desmoxytes Chamberlin, 1923, often referred to as “dragon millipedes”, encompasses 11 unquestioned troglobionts (e.g. Fig.
In contrast, species of the small, generally Oriental family Opisotretidae (Polydesmida) also occur epigeically in the karst regions of southern China, but the few likely troglobionts have only been encountered in Sulawesi, Indonesia and in Papua New Guinea (
Not only is the fauna of cavernicolous diplopods of China clearly biased to rather few lineages, but also the morphotypes they represent appear to be fewer compared to epigean counterparts. Thus, only juloid, glomeroid and polydesmoid morphotype millipedes occur among troglobionts in southern China.
The representation of millipede orders in the fauna of southern China, also roughly showing the proportion of presumed troglobionts, is summarized in Table
Generally speaking, southern China harbours a very rich and diverse fauna of Diplopoda, probably numbering several hundred species. It consists of not only clearly dominating Oriental elements, but also a proportion of Palaearctic ones. Yet only a highly limited number of lineages appear to have successfully colonized the cave environment, not only in China, but in the entire Oriental realm. Biogeographically, these lineages, however few, also demonstrate the dominance of presumably Oriental groups (Kashmireumatidae, Megalotylidae, Cambalopsidae, Sinocallipodidae, Paracortinidae, Hyleoglomeris, Desmoxytes, Pacidesmus, Glenniea, Trichopeltis, Piccola) over the clearly Palaearctic ones (Bollmania, Epanerchodus). In full agreement with common wisdom, the fauna is actually a mixture of components from both these realms, definitely with numerous further troglobitic species still to be revealed. Because truly cave-dwelling genera, tribes or families are nearly absent among the Chinese or even entire Oriental Diplopoda, future explorations seem far more likely to yield lots of further new species, but barely anything else of a higher taxonomic rank. The only remarkable exceptions in southern China are the endemic family Guizhousomatidae, monobasic, and the oligotypic genus Lipseuma, both these taxa likely highly relictual troglobionts. Continental China may well prove to support about 1,000 millipede species of various origins, mainly Oriental and Palaearctic. Most of this impressive diversity is expectedly confined to the warmer, highly montane, humid tropical and subtropical parts of the country where numerous karst massifs are also known to often dominate the landscapes.
The exceptional biotic richness and abounding local endemism of the karsts and their caves in southern China (
I am most grateful to the Organizing Committee of the International “Guangxi Karst and Cave Biodiversity and Conservation Symposium”, held in Nanning, Guangxi, China on 1–5 December 2012, for the kind invitation to participate in the conference and to present a lecture on the same topic. Louis Deharveng and Anne Bedos (Paris, France) have generously rendered their technical assistance. Helen Read (Burnham Beeches, UK), Robert Mesibov (Penguin, Tasmania, Australia) and Pavel Stoev (Sofia, Bulgaria) kindly edited advanced drafts and made several important suggestions.