西双版纳地区的陆生等足类(甲壳亚门:等足目:潮虫亚目)

本文记述西双版纳地区陆生等足类１７种,包括７新种。新种模式标本保存于中国科学院动物研究所。种类名录如下。喜阴虫科Ｐｈｉｌｏｓｃｉｄａｅ 叶肢缅甸虫Ｂｕｒｍｏｎｉｓｃｕｓ ｌｏｂａｔｕｓ Ｋｗｏｎ ＆ Ｔａｉｔｉ,１９９３,勐仑缅甸虫,新种Ｂｕｒｍｏｎｉｓｃｕｓ ｍｅｎｇｌｕｎｅｎｓｉｓ ｓｐ．ｎｏｖ．,版纳缅甸虫,新种Ｂｕｒｍｏｎｉｓｃｕｓ ｂａｎｎｉｃｕｓ ｓｐ．ｎｏｖ．,易武缅甸虫,新种Ｂｕｒ     

Spiders of the families Theridiidae, Tetragnathidae and Araneidae (Arachnida: Araneae) from Aldabra atoll

A total of 36 spider species of the families Theridiidae, Tetragnathidae and Araneidae are recorded from Aldabra atoll. Of these, 26 are described as new, together with one new subspecies. The taxonomy of the new species is discussed and, for comparative purposes, five other species not from Aldabra are illustrated. One new synonymy is established. Records for each species are given with, in some cases, notes on biology. The possible biological significance of the egg sac strings found in some species is considered. Finally, the biogeographical affinities of the Aldabra species are briefly discussed.     

The distribution of fishes on the outer reef slopes of Aldabra (Indian Ocean) in relation to bottom temperatures

Synopsis Ninety six fish belonging to 19 species were taken by deep water line fishing off Aldabra. Analysis of the results shows how various factors such as hooking time changed with depth. The change of bottom temperature with depth was examined. The zone between 100 m and 150 m was found to have considerable temperature variations. The distribution of some serranids and lutjanids appeared to be stratified though there was usually overlap in the range of adjacent species. The results are compared with previous line-fishing off the South coast of Aldabra from deeper water and other areas of the western Indian Ocean.     

Revision of the European species of the genus Trachelipus Budde-Lund, 1908 (Crustacea: Isopoda: Oniscidea)

The European species of Trachelipus Budde-Lund, 1908 are revised. The generic diagnosis is extended. The species T. aegaeus (Verhoeff, 1907), T. arcuatus (Budde-Lund, 1885), T. ater (Budde-Lund, 1896), T. camerani (Tua, 1900), T. dijfkilis (Radu, 1950), T. nodulosus (C. L. Koch, 1838), T. palustris (Strouhal, 1936), T. rathkii (Brandt, 1833), T. ratzeburgii (Brandt, 1833), T. razzautii (Arcangeli, 1913), T. rhinoceros (Budde-Lund, 1885), T. squamuliger (Verhoeff, 1907), T. trilobatus (Stein, 1859), (77 troglobius Tabacaru & Boghean, 1989) and 7T vespertilio (Budde-Lund, 1896) are recognized as valid. Except for T. troglobius , redesriptions, figures and distribution maps are given. A key to species is provided. Nineteen names are new synonyms of the above mentioned ones; nine names become nomina dubia.     

Plant dispersal by the Aldabran giant tortoise,Geochelone gigantea (Schweigger)

Summary A total of 28 species of grasses, herbs, and woody plants germinated from faeces of Aldabran giant tortoises. It seems likely that all members of the land flora can be ingested by tortoises and so may be dispersed by them over short distances.The tortoises are thought to have derived from a Madagascan stock and reached Aldabra from time to time by transmarine migration until the extermination of the Madagascan tortoises about 1100 years ago. The time taken by a tortoise to void its last meal is much longer than that required to float, at present current speeds, from Madagascar to Aldabra. If neither of these parameters have changed since the tortoise migrations to Aldabra, the tortoises may have been responsible for the introduction of plant species to Aldabra.     

Discovery of Hemilepistus elongatus Budde-Lund, 1885 (Isopoda, Oniscidea) in Iran: redescription and intraspecific character variability

In the present study, Hemilepistus elongatus Budde-Lund, 1885 is reported from Iran for the first time, redescribed and its diagnostic characters are figured. This species reveals a high variability in morphological characters. The division of the species at the subspecific level can not be supported anymore. This species differs from other species of the genus by the unique shape of male pleopod-endopodite I.     

A new species of Oniscus Linnaeus, 1758 (Crustacea: Isopoda: Oniscidea) from northern Spain, with a revised key to members of the genus

Oniscvs ancarenisis from the Sierra de Ancares in northern Spain is described as new. The genus Oniscus now contains four species: ancarensis sp. nov. , asellus Linnaeus, lusitanus Verhoeff and simoni Budde-Lund. The distribution of these species is figured and discussed, and a key is given for their determination.     

DUETTING AND VOCAL RECOGNITION BY ALDABRA WHITE-THROATED RAILS DRYOLIMNAS CUVIERI ALDABRANUS

Sonagrams of duets and solo song of the Aldabra White-throated Rail are presented and their behavioural contexts and functions noted. Visual inspection of sonagrams suggests that the structure of elements of high intensity song is individually characteristic. Elements of low intensity song are characteristic for some but not all individuals. The elements of medium intensity song are the most variable within individuals, and it is least likely that these could permit individual recognition. However, it is noted that the temporal pattern of delivery of song elements may provide cues for vocal recognition.
Both male and female Aldabra Rails respond to the playback of their mate's song by either approaching the sound source or vocalizing. A greater number of positive responses was given to playbacks of the mate's song than to playbacks of a song of a strange bird of the same sex as the mate. It is suggested that this difference in responsiveness may in part result from a more rapid habituation to unfamiliar song.
The function of duetting in the Aldabra Rail and other tropical rails is discussed. It is considered that the major function of duetting in the Aldabra Rail may be co-operative territorial defence. The extent and precision of duetting in the Rallidae is considered. It is concluded that precise duetting has not yet been demonstrated in any rail species and that the rates of calling in duets may be internally derived.     

Persistence of distinctive morphotypes in the native range of the CITES‐listed Aldabra giant tortoise

Understanding the extent of morphological variation in the wild population of Aldabra giant tortoises is important for conservation, as morphological variation in captive populations has been interpreted as evidence for lingering genes from extinct tortoise lineages. If true, this could impact reintroduction programmes in the region. The population of giant tortoises on Aldabra Atoll is subdivided and distributed around several islands. Although pronounced morphological variation was recorded in the late 1960s, it was thought to be a temporary phenomenon. Early researchers also raised concerns over the future of the population, which was perceived to have exceeded its carrying capacity. We analyzed monthly monitoring data from 12 transects spanning a recent 15‐year period (1998–2012) during which animals from four subpopulations were counted, measured, and sexed. In addition, we analyzed survival data from individuals first tagged during the early 1970s. The population is stable with no sign of significant decline. Subpopulations differ in density, but these differences are mostly due to differences in the prevailing vegetation type. However, subpopulations differ greatly in both the size of animals and the degree of sexual dimorphism. Comparisons with historical data reveal that phenotypic differences among the subpopulations of tortoises on Aldabra have been apparent for the last 50 years with no sign of diminishing. We conclude that the giant tortoise population on Aldabra is subject to varying ecological selection pressures, giving rise to stable morphotypes in discrete subpopulations. We suggest therefore that (1) the presence of morphological differences among captive Aldabra tortoises does not alone provide convincing evidence of genes from other extinct species; and (2) Aldabra serves as an important example of how conservation and management in situ can add to the scientific value of populations and perhaps enable them to better adapt to future ecological pressures.     

Feeding response of the Aldabra giant tortoise (Geochelone gigantea) to island plants showing heterophylly

Aim Heterophylly is present in many plant species on oceanic islands. Almost all of these plants are island endemics, and heterophylly may have evolved as a response to feeding from large insular browsers such as giant tortoises and flightless birds. We tested this anti‐browser hypothesis by feeding Aldabra giant tortoises (Geochelone gigantea) with leaves of native Mauritian plants to see if they distinguished between juvenile and adult leaves and between heteophyllous and homophyllous species. Location Mauritius. Methods In a choice experiment we recorded feeding response of four captive Aldabra giant tortoises to 10 species of Mauritian plants, of which seven were heterophyllous and three homophyllous. Results In general, juvenile leaves of heterophyllous species showed convergence in shape and midrib coloration. Homophyllous foliage was preferred to heterophyllous, and among heterophyllous species adult foliage was preferred to juvenile. Main conclusions Several Mascarene heterophyllous plants show convergence in morphology of juvenile leaves and these are avoided by giant tortoises. This indicates a strong selection history from large browsers such as the giant tortoises. The Mascarene example is in accordance with several other comparable cases of plant‐large browser interactions from other archipelagos.     

Giant tortoise habitats under increasing drought conditions on Aldabra Atoll—Ecological indicators to monitor rainfall anomalies and related vegetation activity

Aldabra Atoll has the largest population of giant tortoises (Aldabrachelys gigantea) in the world. As such an important biological resource, it is necessary to understand how the effects of climate change will impact this keystone species; in particular the frequency of drought, which is likely to affect tortoise habitat. To assess whether drought frequency has changed over the last 50 years on Aldabra, we calculated the standardized precipitation index (SPI) to identify drought periods using monthly rainfall data collected during 1969–2013. We found that drought frequency has increased to more than six drought months per year today compared with about two months per year in the 1970s (t = 2.884, p = 0.006). We used MODIS normalized difference vegetation index (NDVI) as a proxy for vegetation activity, to determine how vegetation has responded to the changing drought frequency between 2000 and 2013. We found that Aldabra’s vegetation is highly responsive to changes in rainfall: anomalies in long-term mean monthly NDVI across Aldabra were found to decrease below the mean during most drought periods and increase above the mean during most non-drought periods. To investigate the response of tortoise habitat to rainfall, we extracted mean NDVI anomalies for three key habitat types. Open mixed scrub and grasslands, the preferred habitat of tortoises, showed the greatest decrease in vegetation activity during drought periods, and the greatest increase in average greenness during non-drought periods. Recent analysis has shown vegetation changes on Aldabra in recent decades. If these changes are caused by decreased precipitation, then the increased frequency of drought could impact the tortoise population, in both the short and long term, by limiting the quality and quantity of forage and/or shade availability within favoured habitats, and by changing the habitat composition across the atoll.     

Was there a second adaptive radiation of giant tortoises in the Indian Ocean? Using mitochondrial DNA to investigate speciation and biogeography of Aldabrachelys (Reptilia,Testudinidae)

A radiation of five species of giant tortoises (Cylindraspis) existed in the southwest Indian Ocean, on the Mascarene islands, and another (of Aldabrachelys) has been postulated on small islands north of Madagascar, from where at least eight nominal species have been named and up to five have been recently recognized. Of 37 specimens of Madagascan and small-island Aldabrachelys investigated by us, 23 yielded significant portions of a 428-base-pair (bp) fragment of mitochondrial (cytochrome b and tRNA-Glu), including type material of seven nominal species (A. arnoldi, A. dussumieri, A. hololissa, A. daudinii, A. sumierei, A. ponderosa and A. gouffei). These and nearly all the remaining specimens, including 15 additional captive individuals sequenced previously, show little variation. Thirty-three exhibit no differences and the remainder diverge by only 1-4 bp (0.23-0.93%). This contrasts with more widely accepted tortoise species which show much greater inter- and intraspecific differences. The non-Madagascan material examined may therefore only represent a single species and all specimens may come from Aldabra where the common haplotype is known to occur. The present study provides no evidence against the Madagascan origin for Aldabra tortoises suggested by a previous molecular phylogenetic analysis, the direction of marine currents and phylogeography of other reptiles in the area. Ancient mitochondrial DNA from the extinct subfossil A. grandidieri of Madagascar differs at 25 sites (5.8%) from all other Aldabrachelys samples examined here.     

Short-term climate change and the extinction of the snail Rhachistia aldabrae (Gastropoda: Pulmonata)

The only known population of the Aldabra banded snail Rhachistia aldabrae declined through the late twentieth century, leading to its extinction in the late 1990s. This occurred within a stable habitat and its extinction is attributable to decreasing rainfall on Aldabra atoll, associated with regional changes in rainfall patterns in the late twentieth and early twenty-first century. It is proposed that the extinction of this species is a direct result of decreasing rainfall leading to increased mortality of juvenile snails.     

Low‐coverage reduced representation sequencing reveals subtle within‐island genetic structure in Aldabra giant tortoises

Aldabrachelys gigantea (Aldabra giant tortoise) is one of only two giant tortoise species left in the world and survives as a single wild population of over 100,000 individuals on Aldabra Atoll, Seychelles. Despite this large current population size, the species faces an uncertain future because of its extremely restricted distribution range and high vulnerability to the projected consequences of climate change. Captive‐bred A. gigantea are increasingly used in rewilding programs across the region, where they are introduced to replace extinct giant tortoises in an attempt to functionally resurrect degraded island ecosystems. However, there has been little consideration of the current levels of genetic variation and differentiation within and among the islands on Aldabra. As previous microsatellite studies were inconclusive, we combined low‐coverage and double‐digest restriction‐associated DNA (ddRAD) sequencing to analyze samples from 33 tortoises (11 from each main island). Using 5426 variant sites within the tortoise genome, we detected patterns of within‐island population structure, but no differentiation between the islands. These unexpected results highlight the importance of using genome‐wide genetic markers to capture higher‐resolution genetic structure to inform future management plans, even in a seemingly panmictic population. We show that low‐coverage ddRAD sequencing provides an affordable alternative approach to conservation genomic projects of non‐model species with large genomes.     

A new species of Colpocephalum (Phthiraptera) on Threskiornis (Aves) from Aldabra

A new species, Colpocephalum abhotti, is described for specimens off the type-host, Threskiornis aethio-pica ahbotti, from Aldabra.     

C4 photosynthesis in the vegetation of Aldabra Atoll

Summary The occurrence of the C₄ photosynthetic system, based upon an examination of leaf anatomy, of nearly all species of the vegetation of Aldabra Atoll, western Indian Ocean, is reported. About 19% of the flora has the C₄ system. It only occurs in herbaceous plants, which grow either in grasslands or as an understorey to tall shrubs. Both C₃ and C₄ species compete side by side in the mixed-species communities.The Royal Society Aldabra Research Station     

Habitats, abundance and diets of Muricacean gastropods at Aldabra Atoll

Twenty-three species of predatory Muricacean gastropods are common on the intertidal rocky shores of Aldabra Atoll. Species show a division of the habitat space by vertical zonation along the intertidal gradient, longitudinal zonation around an exposure gradient and by choice of substrate type. Co-occurring species usually overlap very little in size and this may indicate utilization of different parts of the habitat/food resource.
Most species of Thais, Purpura and Morula feed by drilling sedentary or semi-mobile prey and most suitable prey species are exploited. Species show a broad partitioning of the available food resources and overlap between species is usually low. Large species have generally more varied diets than small species. Size variation of some species around the Atoll may be attributed to differences in diet. Species of Drupa do not drill but feed upon eunicid, nereid and sipunculid worms and small Crustacea. Drupella cornus and two species of Coralliophilidae feed upon coral polyps.
The Muricacea occur together with other predatory gastropods, such as the Conidae, Mitridae and Buccinidae, but these families have generally different diets and largely independent food webs.
The Muricacea at Aldabra appear to have narrower habitat ranges than muricids in temperate areas.     

The biology of terns nesting at Aldabra Atoll, Indian Ocean, with particular reference to breeding seasonality

Five species of tern breed on Aldabra Atoll (09° 24' S; 46° 20' E). The Caspian tern Sterna caspia and Crested tern S. bergii feed exclusively in very shallow reef/lagoon water, the Fairy tern Gygis alba and Brown noddy Anous stolidus feed out at sea, and the Black-naped tern Sterna sumatrana is intermediate in its foraging. Both of the shallow-water species lay during the south-east monsoon season, the Caspian tern from April to August and the Crested tern from June to August, but the Crested tern also lays in December and January. The remaining three species have extended laying periods largely circumscribed by the north-west monsoon season from November to March. Breeding population size of the Caspian tern is in the low tens and of the Brown noddy in the low thousands, with the other species each numbering in the hundreds. The distribution and abundance of the nine species of tern breeding within the Seychelles ( sensu lato ) vary on the different island groups in a manner interpretable in terms of depth of the surrounding waters. Systematic differences between the central Seychelles and Aldabra groups in timing of breeding by terns which feed out at sea may be associated with seasonal latitudinal movement of the divergence zone between the South Equatorial Current and the Equatorial Counter-current, acting via correlated latitudinal shifts of prey species and game-fish abundance.     

The Indian Ocean giant tortoise Testudo gigantea on Aldabra

The Indian Ocean giant tortoise survives on Aldabra, an atoll north-west of Madagascar. The Bristol Seychelles Expedition estimated the total numbers as 33,000 during visits in 1964 and 1965. Growth and movements were recorded during marking experiments. The growth rate with size is plotted, the time scale being derived from the number of rings on the shields of the shell; and the growth curve is compared with that for captive tortoises.
Variation in many characters of supposed taxonomic value is explained as the influence of environmental factors on the normal growth pattern, and of non-adaptive differences expressed during adult life. The present separation of north and south Aldabra, and Seychelles forms is not supported.
An explanation is suggested for the uniformity of shape among tortoises.
Observations were made on the feeding, diurnal movements and mortality of tortoises on Aldabra.     

Reconstructing an island radiation using ancient and recent DNA: the extinct and living day geckos (Phelsuma) of the Mascarene islands

Mitochondrial (12SrRNA and cyt b, 1086 bp) and nuclear (c-mos, 374 bp) DNA sequences were used to investigate relationships and biogeography of 24 living and extinct taxa of Phelsuma geckos. Monophyly of Phelsuma and sister relationship to the SW African Rhoptropella is corroborated. Phelsuma originated on Madagascar and made multiple long-distance invasions of oceanic islands including the Mascarenes, Aldabra, Comores, Seychelles, Andamans, and perhaps Pemba. The Mascarenes were probably colonised once, about 4.2-5.1Ma, and here Phelsuma rosagularis and Phelsuma inexpectata are newly recognised as species, as are three lineages of Phelsuma cepediana. Mascarene relationships are: Phelsuma edwardnewtoni, Phelsuma gigas (Phelsuma guentheri ((((P. cepediana A (P. cepediana B, C)) P. rosagularis) Phelsuma borbonica) ((Phelsuma ornata, P. inexpectata) Phelsuma guimbeaui))). The two recently extinct species, P. edwardnewtoni and the giant secondarily nocturnal Phelsuma gigas, differentiated on Rodrigues while on Mauritius the large nocturnal P. guentheri separated from a small diurnal form that radiated into six species, a likely result of volcanic activity. Two small-bodied lineages from Mauritius invaded the more recent island of Réunion producing two more species. Outside the Mascarenes, two mainly Madagascan assemblages are substantiated: Phelsuma serraticauda (Phelsuma lineata, Phelsuma laticauda, Phelsuma quadriocellata); (Phelsuma m. kochi (Phelsuma m. grandis, Phelsuma abboti)) (Phelsuma astriata, Phelsuma sundbergi). Their relationships to the Mascarene clade, and to Phelsuma mutabilis, Phelsuma standingi and Phelsuma andamanensis are unresolved.