Seychelles Islands Research Articles

The evolution of island gigantism and body size variation in tortoises and turtles

Extant chelonians (turtles and tortoises) span almost four orders of magnitude of body size, including the startling examples of gigantism seen in the tortoises of the Galapagos and Seychelles islands. However, the evolutionary determinants of size diversity in chelonians are poorly understood. We present a comparative analysis of body size evolution in turtles and tortoises within a phylogenetic framework. Our results reveal a pronounced relationship between habitat and optimal body size in chelonians. We found strong evidence for separate, larger optimal body sizes for sea turtles and island tortoises, the latter showing support for the rule of island gigantism in non-mammalian amniotes. Optimal sizes for freshwater and mainland terrestrial turtles are similar and smaller, although the range of body size variation in these forms is qualitatively greater. The greater number of potential niches in freshwater and terrestrial environments may mean that body size relationships are more complicated in these habitats.

Molecular Characterization of Hepatozoon Species in Reptiles from the Seychelles

Hepatozoon parasites were examined for the first time in reptiles from the Seychelles Islands. Although both prevalence and intensity were low, Hepatozoon species were detected in individuals from 2 endemic species, the lizard Mabuya wrightii and the snake Lycognathophis seychellensis. This was confirmed using visual identification and through sequencing part of the 18s rRNA gene. Phylogenetic analysis indicates that the Hepatozoon on the Seychelles form a monophyletic lineage, although more data are clearly needed to stabilize estimates of relationships based on this marker.

Eastward from Africa: palaeocurrent-mediated chameleon dispersal to the Seychelles islands

Madagascar and the Seychelles are Gondwanan remnants currently isolated in the Indian Ocean. In the Late Cretaceous, these islands were joined with India to form the Indigascar landmass, which itself then split into its three component parts around the start of the Tertiary. This history is reflected in the biota of the Seychelles, which appears to contain examples of both vicariance- and dispersal-mediated divergence from Malagasy or Indian sister taxa. One lineage for which this has been assumed but never thoroughly tested is the Seychellean tiger chameleon, a species assigned to the otherwise Madagascar-endemic genus Calumma. We present a multi-locus phylogenetic study of chameleons, and find that the Seychellean species is actually the sister taxon of a southern African clade and requires accomodation in its own genus as Archaius tigris. Divergence dating and biogeographic analyses indicate an origin by transoceanic dispersal from Africa to the Seychelles in the Eocene-Oligocene, providing, to our knowledge, the first such well-documented example and supporting novel palaeocurrent reconstructions.

Economic valuation of the influence of invasive alien species on the economy of the Seychelles islands

Biodiversity underpins most economic activities in Seychelles, and loss of biodiversity as a result of invasive alien species (IAS) could result in major negative economic impacts for the country. This paper assesses the value of impacts of IAS on biodiversity, natural resources and the national economy, using the principles of total economic value (TEV). The contingent valuation method was used to obtain a willingness to pay (WTP) estimate for a policy to protect important biodiversity from IAS. Tourists indicated a mean WTP of US$52–US$58 on top of their usual expenditures to fund conservation policy. At present approximately US$0.25 million per year is spent on IAS control while the economic damage associated with 4 key IAS is approximately US$21 million per year. Comparing the benefits from eradication with the costs involved gives a benefit-cost ratio greater than unity, indicating that the policy of eradicating IAS is economically justified. However, there is a long way to go before the resources devoted to the problem will be in proportion to the risks.

Mycorrhizal symbionts of Pisonia grandis and P. sechellarum in Seychelles: identification of mycorrhizal fungi and description of new Tomentella species

Nyctaginaceae includes species that are predominantly non-mycorrhizal or form arbuscular or ectomycorrhiza. Root-associated fungi were studied from P. grandis and P. sechellarum roots collected respectively on the islands of Cousin and Silhouette in Seychelles. In addition fungal sporocarps were collected from the sampling area. Fungal symbionts were identified from the roots by anatomotyping and rDNA sequencing; sporocarps collected were examined microscopically and sequenced. Three distantly related ectomycorrhizal fungal species belonging to Thelephoraceae were identified from the roots of P. grandis. Sporocarps also were found for two symbionts and described as new Tomentella species. In addition Tomentella species collected from other Seychelles islands were studied and described as new species if there was no close resemblance to previously established species. P. sechellarum was determined to be an arbuscular mycorrhizal plant; three arbuscular mycorrhizal fungal species were detected from the roots. P. grandis is probably associated only with species of Thelephoraceae throughout its area. Only five Tomentella species are known to form ectomycorrhiza with P. grandis and they never have been found to be associated with another host, suggesting adaptation of these fungi to extreme environmental conditions in host’s habitat.

Glomerular hyperfiltration and increased proximal sodium reabsorption in subjects with type 2 diabetes or impaired fasting glucose in a population of the African region

BACKGROUND. Glomerular hyperfiltration (GHF) is a well-recognized early renal alteration in diabetic patients. As the prevalence of GHF is largely unknown in populations in the African region with respect to normal fasting glucose (NFG), impaired fasting glucose (IFG) and type 2 diabetes [diabetes mellitus (DM)], we conducted a cross-sectional study in the Seychelles islands among families including at least one member with hypertension. METHODS. The glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and proximal tubular sodium reabsorption were measured using inulin, p-aminohippurate (PAH) and endogenous lithium clearance, respectively. Twenty-four-hour urine was collected on the preceding day. RESULTS. Of the 363 participants (mean age 44.7 years), 6.6% had IFG, 9.9% had DM and 63.3% had hypertension. The prevalence of GHF, defined as a GFR >140 ml/min, was 17.2%, 29.2% and 52.8% in NFG, IFG and DM, respectively (P trend <0.001). Compared to NFG, the adjusted odds ratio for GHF was 1.99 [95% confidence interval (CI) 0.73-5.44] for IFG and 5.88 (2.39-14.45) for DM. Lithium clearance and fractional excretion of lithium were lower in DM and IFG than NFG (P < 0.001). CONCLUSION. In this population of African descent, subjects with impaired fasting glucose or type 2 diabetes had a high prevalence of GHF and enhanced proximal sodium reabsorption. These findings provide further insight on the elevated incidence of nephropathy reported among African diabetic individuals.

Insights into the evolutionary history of Indo-Pacific bloodfeeding terrestrial leeches (Hirudinida:Arhynchobdellida:Haemadipisdae)

Haemadipsidae is a clade of notorious bloodfeeding annelids adapted to tropical and sub-tropical rainforests found throughout the Indo-Pacific. This family traditionally includes duognathous (two-jawed) endemics, each placed in their own genus, from continental and volcanic islands including: Australia, Indonesia, Madagascar, Papua New Guinea, Philippines, Seychelles, and South Pacific islands, while trignathous (three-jawed) Tritetrabdella species and the speciose Haemadipsa are exclusive to the Indian subcontinent ranging into east and south-east Asia. One of the more compelling aspects of haemadipsids is their distribution on post-Gondwanan landmasses. In this study, the phylogenetic relationships, taxonomy and biogeographic patterns of Haemadipsidae were examined. Over 5 kb of sequence data from three genes (nuclear 18S rDNA and 28S rDNA and mitochondrial COI) for 37 haemadipsid exemplars, representing 12 of the 15 recognised genera, were analysed under the criteria of maximum parsimony and Bayesian inference. The results show that widespread duognathous species form a monophyletic group derived from trignathous ancestry and are sister to a new trignathous clade for Haemadipsidae. This phylogenetic hypothesis rejected Gondwanan vicariance as an explanation for the diversification of haemadipsids. Haemadipsidae is accepted as the formal name for these Indo-Pacific leeches. Whereas the subdivisions Haemadipsinae and Domanibdellinae are clarified, there is a need to establish a new subfamily, Tritetrabdellinae, for the newly identified trignathous clade that is sister to Domanibdellinae. This study provides a basis for continued elucidation of the evolutionary relationships and classification of these terrestrial annelids.

Tardigrades of the Seychelles Islands, with the description of three new species

Tardigrades of the Seychelles Islands, with the description of three new species

The Goblin Spider Genus Heteroonops (Araneae, Oonopidae), With Notes on Oonops

The goblin spider genus Heteroonops is relimited to include those soft-bodied oonopids with anteriorly situated, posteriorly directed projections on the endites of males, and elongated, highly spinose pedipalps in females, and is hypothesized to be natively circum-Caribbean. The type species, H. spinimanus (Simon), has attained a pantropical distribution, has been known only from females, and has therefore been hypothesized to be parthenogenetic. Although the species may have some parthenogenetic populations, males have apparently been collected together with females twice, once in the Seychelle Islands and once in Florida. We therefore place Matyotia tetraspinosus Saaristo (a monotypic genus and species established for that Seychelle specimen) as the male (and hence a junior synonym) of H. spinimanus; Oonopinus hunus Suman, described from Hawaii, is also newly synonymized with H. spinimanus, which is newly recorded from Mexico, the Bahama Islands, Colombia, Madeira, Madagascar, the Marquesas Islands, the Cook Islands, Pitcairn Island, Fiji, New Caledonia, and Queensland. Four specific names are transferred to Heteroonops Oonops singulus Gertsch and Davis (from Mexico), O. validus Bryant (from Hispaniola), O. castellus Chickering (from the Virgin Islands), and O. delegenus Chickering (from Puerto Rico); H. delegenus is placed as a junior synonym of H. castellus, and the female of H. validus is described for the first time. Ten new species are described: H. murphyorum from Costa Rica, H. andros from the Bahama Islands, H. spinigata from Jamaica, H. vega, H. iviei, and H. castelloides from Hispaniola, H. toro from Puerto Rico, H. croix from the Virgin Islands, H. saba from Saba and Montserrat, and H. macaque from Dominica. Because the status of Heteroonops as a genus separate from Oonops Templeton has been questioned, we present a redescription of the family's type species, Oonops pulcher Templeton, based on topotypical specimens from Scotland; it is unlikely that any of the plethora of New World species that have been assigned to Oonops are actually congeneric with O. pulcher.

Species composition and distribution of scleractinians on the reefs of the Seychelles Islands

New data on the species composition and distribution of reef-building corals on some reefs of the Seychelles Islands are presented. The study revealed 236 species belonging to 68 genera, which exceeds the well-known values of scleractinian species composition in this region by almost two times. Representatives of the families Acroporidae, Poritidae, and Faviidae dominated. Settlements of the blue coral Heliopora coerulea and the hydroid Millepora dichotoma were fairly numerous and in aggregate covered up to 40% of the substratum. In its species composition, the coral fauna of the Seychelles reefs makes a single unit with the Indo-Pacific tropical fauna.

Implementing carbon neutral destination policies: issues from the Seychelles

It is now accepted that tourism is a significant contributor to global climate change, especially through air travel's high greenhouse gas emissions. This paper analyses the dilemmas facing tourism planning in many small island developing states and presents a model approach toward overcoming those dilemmas by adapting carbon neutral tourism policies. It researches the implementation issues facing carbon neutral tourism policies on the Seychelles Islands: tourism to the islands is energy-intensive, and current plans to increase tourist numbers will entail growing emissions of greenhouse gases. This paper analyses tourism's current levels of energy use and emissions, and explores ways to reduce them. Based on a survey of tourists and industry representatives in the Seychelles, it discusses options for tourism-dependent small island developing states to implement and finance carbon neutrality, while outlining the complexities and limitations of such an objective.

Can land crabs be used as a rapid ecosystem evaluation tool? A test using distribution and abundance of several genera from the Seychelles

Habitat destruction and the introduction of exotic species are the primary causes of biodiversity loss in tropical island ecosystems. Conservation efforts on oceanic islands are often biased towards charismatic vertebrate faunas, neglecting invertebrate assemblages. We sampled the land crab community on five islands in the central Seychelles; in the intertidal zone, in the supralittoral zone and in nine different inland habitat types to explore the impacts of exotic vegetation and environmental variables on land crab abundance and community composition, and investigate whether land crabs can be used as a tool for the rapid assessment of habitat quality on tropical oceanic islands. We found that species richness and the abundance of the dominant ghost crab Ocypode cordimana was higher in native habitat types than habitats dominated by exotic vegetation. Available ground substrate suitable for burrowing may be a limiting factor for O. cordimana in exotic habitat types. Coenobita rugosus, the dominant crab in the supralittoral zone is largely absent where there is no supralittoral vegetation. These results suggest that land crabs could be reliable indicators of habitat quality on oceanic islands. The abundance of land crabs could be used in the rapid assessment of ecosystem perturbation and identification of sites requiring restoration or management.

Association Between White-Coat Effect and Blunted Dipping of Nocturnal Blood Pressure

In this study, we assessed whether the white-coat effect (difference between office and daytime blood pressure (BP)) is associated with nondipping (absence of BP decrease at night). Data were available in 371 individuals of African descent from 74 families selected from a population-based hypertension register in the Seychelles Islands and in 295 Caucasian individuals randomly selected from a population-based study in Switzerland. We used standard multiple linear regression in the Swiss data and generalized estimating equations to account for familial correlations in the Seychelles data. The prevalence of systolic and diastolic nondipping (<10% nocturnal BP decrease) and white-coat hypertension (WCH) was respectively 51, 46, and 4% in blacks and 33, 37, and 7% in whites. When white coat effect and nocturnal dipping were taken as continuous variables (mm Hg), systolic (SBP) and diastolic BP (DBP) dipping were associated inversely and independently with white-coat effect (P < 0.05) in both populations. Analogously, the difference between office and daytime heart rate was inversely associated with the difference between daytime and night-time heart rate in the two populations. These results did not change after adjustment for potential confounders. The white-coat effect is associated with BP nondipping. The similar associations between office-daytime values and daytime-night-time values for both BP and heart rate suggest that the sympathetic nervous system might play a role. Our findings also further stress the interest, for clinicians, of assessing the presence of a white-coat effect as a means to further identify patients at increased cardiovascular risk and guide treatment accordingly.

First described Patu spiders (Araneae, Symphytognathidae) from Asia

Five new species of the spider family Symphytognathidae (Araneae) are described and illustrated from southern China: Patu bicorniventris spec. nov., P. nigeri spec. nov., P. quadriventris spec. nov., P. shiluensis spec. nov. and P. spinathoraxi spec. nov. These spiders were collected in the leaf litter and tree canopy of tropical rainforests by sieving and fogging. The genus Patu Marples, 1951, known from Colombia, Hispaniola, Oceania, and African Seychelles Islands, except that web structure and web-building behavior of undescribed Patu species were reported before, is described from Asia for the first time.

Tardigrades of the Seychelles Islands, with the description of three new species

In the context of the project “The Nature Protection Trust of Seychelles”, three species new to science are described (Macrobiotus creber sp. n., Macrobiotus perfidus sp. n. and Macrobiotus diguensis sp. n.) and two species (Macrobiotus madegassus and Minibiotus continuus) are recorded for the Seychelles for the first time. Macrobiotus creber sp. n. belongs to the furciger group but it differs from the members of this group in some metric characters of the buccopharyngeal apparatus, or of the claws, and in some characters of the eggs. Macrobiotus perfidus sp. n. is similar to M. pseudocoronatus but it differs from it in having small cuticular tubercles, in lacking an anterior band of teeth and a less developed posterior ring of triangular teeth in the buccal cavity, in having slightly shorter macroplacoids, slightly longer and slender claws and in characters of the eggs. Macrobiotus diguensis sp. n. is similar to M. snaresensis and M. erminiae but it differs from them in metric characters of the bucco-pharyngeal apparatus, in having more slender claws and in some characters of the eggs.

Ecosystem effects of climate change on the Seychelles islands: Current impacts and the potential for resolution

This article was submitted without an abstract, please refer to the full-text PDF file.

Ecosystem effects of climate change on the Seychelles islands: Current impacts and the potential for resolution

Ecosystem effects of climate change on the Seychelles islands: Current impacts and the potential for resolution

Divergent fifteen-year trends in traditional and cardiometabolic risk factors of cardiovascular diseases in the Seychelles

ObjectiveFew studies have assessed secular changes in the levels of cardiovascular risk factors (CV-RF) in populations of low or middle income countries. The systematic collection of a broad set of both traditional and metabolic CV-RF in 1989 and 2004 in the population of the Seychelles islands provides a unique opportunity to examine trends at a fairly early stage of the "diabesity" era in a country in the African region.MethodsTwo examination surveys were conducted in independent random samples of the population aged 25–64 years in 1989 and 2004, attended by respectively 1081 and 1255 participants (participation rates >80%). All results are age-standardized to the WHO standard population.ResultsIn 2004 vs. 1989, the levels of the main traditional CV-RF have either decreased, e.g. smoking (17% vs. 30%, p < 0.001), mean blood pressure (127.8/84.8 vs. 130.0/83.4 mmHg, p < 0.05), or only moderately increased, e.g. median LDL-cholesterol (3.58 vs. 3.36 mmol/l, p < 0. 01). In contrast, marked detrimental trends were found for obesity (37% vs. 21%, p < 0.001) and several cardiometabolic CVD-RF, e.g. mean HDL-cholesterol (1.36 vs. 1.40 mmol/l, p < 0.05), median triglycerides (0.80 vs. 0.78 mmol/l, p < 0.01), mean blood glucose (5.89 vs. 5.22 mmol/l, p < 0.001), median insulin (11.6 vs. 8.3 μmol/l, p < 0.001), median HOMA-IR (2.9 vs. 1.8, p < 0.001) and diabetes (9.4% vs. 6.2%, p < 0.001). At age 40–64, the prevalence of elevated total cardiovascular risk tended to decrease (e.g. WHO-ISH risk score ≥10; 11% vs. 13%, ns), whereas the prevalence of the metabolic syndrome (which integrates several cardiometabolic CVD-RF) nearly doubled (36% vs. 20%, p < 0.001). Data on physical activity and on intake of alcohol, fruit and vegetables are also provided. Awareness and treatment rates improved substantially for hypertension and diabetes, but control rates improved for the former only. Median levels of the cardiometabolic CVD-RF increased between 1989 and 2004 within all BMI strata, suggesting that the worsening levels of cardiometabolic CVD-RF in the population were not only related to increasing BMI levels in the interval.ConclusionThe levels of several traditional CVD-RF improved over time, while marked detrimental trends were observed for obesity, diabetes and several cardiometabolic factors. Thus, in this population, the rapid health transition was characterized by substantial changes in the patterns of CVD-RF. More generally, this analysis suggests the importance of surveillance systems to identify risk factor trends and the need for preventive strategies to promote healthy lifestyles and nutrition.

Climate change and identification of terrestrial protected areas in the Seychelles Islands

The Seychelles islands are notable for the high proportion of land area designated as National Parks (43%). These sites were designated with the aim of protecting water catchments and threatened species, mostly in the 1960s and 1970s. Their location does not take into consideration the likely impacts of climate change. It is anticipated that changes in organism and habitat distributions in the Seychelles islands will occur over the next 50-100 years largely as a result of sea level change and altered rainfall patterns. Species and sites at particular risk will be those associated with low-lying areas and high altitude moss forest habitats. Due to the small area of the Seychelles islands and their isolated nature there is no significant potential for redesign of protected areas to allow migration and mitigation, unlike continental ecosystems. The impacts on particularly threatened protected areas, both existing (e.g. Aldabra World Heritage Site) and potential, are highlighted.

Setting Conservation Priorities - A Key Biodiversity Areas Analysis for the Seychelles Islands

Key Biodiversity Areas (KBAs) are areas identified as being important for the conservation of biodiversity due to the presence of threatened species or habitats, or particularly high levels of biodiversity. They are a useful concept for setting site conservation priorities, combining other categories such as biodiversity hotspots, Important Bird Areas and 'ecoregions'. An analysis of the terrestrial KBAs of the Seychelles islands based on comprehensive biodiversity assess- ments identifies 48 sites of conservation importance. A high proportion of the land area of Seychelles is designated as pro- tected areas, however, the KBA analysis indicates that this needs to be expanded by a further 47km 2 . The KBAs are threatened by development (6 sites), sea-level rise (13 sites) and unpredictable climate change (16 sites). Habitat degrada- tion caused by invasive species is the most significant threat to the largest number of KBAs, affecting all 48 sites with in- vasive species dominating the plant communities in 15 sites. There is an urgent requirement for future conservation in Seychelles to combine effective legal protection of KBAs with large-scale habitat restoration.