Southwestern Indian Research Articles

The epidemic of Dengue virus type-2 Cosmopolitan genotype on Reunion Island relates to its active circulation in the Southwestern Indian Ocean neighboring islands

Reunion Island is currently experiencing an epidemic caused by Dengue virus type-2 (DENV-2) resulting in over 6,763 cases from austral summer 2017 to winter 2018. Phylogenetic analyses on two non-imported cases of dengue infection from Reunion Island highlight a regional circulation of DENV-2 Cosmopolitan lineage 1 virus on both Reunion Island and the Seychelles.

Revalidation of Caridina natalensis De Man, 1908 (Crustacea: Decapoda: Atyidae) in the South Western Indian Ocean.

Numerous specimens of a freshwater shrimp with small eggs belonging to the Caridina nilotica complex collected in the South Western Indian Ocean were studied and compared with recent and old collection specimens genetically (16S mitochondrial analysis for recent and type specimens) and morphologically. The results revealed that, in the Indian Ocean, what has been identified by several authors under various species names of the complex C. nilotica, was in fact C. natalensis De Man, 1908. This valid species is re-described and compared with closely related species, often confused with it in this area: C. brachydactyla De Man, 1908, C. brevidactyla Roux, 1920, C. gracilipes De Man, 1892 and C. longirostris H. Milne Edwards, 1837.

Genetic difference between African and Japanese scombropid populations based on cytochrome c oxidase subunit I gene sequences

The fish family Scombropidae consists of a single genus, Scombrops, and is distributed in the waters of the northwestern Pacific Ocean, southwestern Indian Ocean and western Atlantic Ocean, including the Caribbean Sea. Among these, the population of South Africa has been renamed from Scombrops dubius to Scombrops boops, which is known to be distributed in waters around Japanese Archipelago. We are skeptical of this revision as the two populations are geographically isolated between the waters of the Far East and the southern end of the Africa coast. Recently, our lab determined the sequences of the complete mitochondrial genome of three Japanese gnomefish, S. boops, Scombrops gilberti and an undescribed scombropid species (Scombrops sp.). Here, we compared the partial sequence of cytochrome c oxidase subunit I (COI) from the three Japanese gnomefish with that of the African population. The African sequences showed 95.5–96.6% identity with the Japanese sequences, while the corresponding sequences from the Japanese species showed 98.2–100% identity with each other. A maximum likelihood tree based on the partial sequence of COI also demonstrated that the clade of African gnomefish is distinct from those of Japanese species including S. boops. These results suggest that the scombropid fish in the African waters is a different species from S. boops and that it is appropriate to resurrect the name Scombrops dubius for the African population.

An Observational Perspective of Sea Surface Salinity in the Southwestern Indian Ocean and Its Role in the South Asia Summer Monsoon

The seasonal variability of sea surface salinity anomalies (SSSAs) in the Indian Ocean is investigated for its role in the South Asian Summer Monsoon. We have observed an elongated spatial-feature of the positive SSSAs in the southwestern Indian Ocean before the onset of the South Asian Summer Monsoon (SASM) by using both the Aquarius satellite and the Argo float datasets. The maximum variable areas of SSSAs in the Indian Ocean are along (60 ° E–80 ° E) and symmetrical to the equator, divided into the southern and northern parts. Further, we have found that the annual variability of SSSAs changes earlier than that of sea surface temperature anomalies (SSTAs) in the corresponding areas, due to the change of wind stress and freshwater flux. The change of barrier layer thickness (BLT) anomalies is in phase with that of SSSAs in the southwestern Indian Ocean, which helps to sustain the warming water by prohibiting upwelling. Due to the time delay of SSSAs change between the northern and southern parts, SSSAs, therefore, take part in the seasonal process of the SASM via promoting the SSTAs gradient for the cross-equator currents.

Status of coral-Symbiodiniaceae research in Western Indian Ocean

Underpinning the success of coral reefs in nutrient poor marine environments is mutualism established between corals and members of the phylum Symbiodiniaceae. In recent decades, reef-building corals have been affected by multiple stressors including bleaching, which results largely from elevated sea surface temperature and exposure to excessive solar radiation, ultimately caused by global warming. Accumulating evidence demonstrates differential resistance to bleaching among coral-Symbiodiniaceae partnerships; encouraging studies on the diversity and phylogenetics of Symbiodiniaceae. Examination of the existing knowledge reveals insights into both longitudinal and latitudinal partitioning of members of Symbiodiniaceae at genus level, throughout the Western Indian Ocean (WIO). Contrary to expectations, due to decreasing sea surface temperature with latitude, this review has revealed an increase of polymorphic symbioses involving bleaching susceptible coral genera with latitude. This could partly explain the low impacts of bleaching episodes in the South Western Indian Ocean. In order to substantiate this, we suggest long term monitoring of coral-Symbiodiniaceae symbioses in the WIO region. Such monitoring should take advantage of genetic approaches that can decipher the fine scale diversity of Symbiodiniaceae in coral tissues within a changing climate.

Notes on Afonsoconus Tucker & Tenorio, 2013 (Gastropoda, Conidae), with description of a new species from the Southwestern Indian Ocean

Although cone snails are among the most studied group of gastropods, new species are still regularly described. Here, we focus on Afonsoconus Tucker & Tenorio, 2013, a lineage that includes only two species from the Indo-Pacific Ocean. The analysis of molecular (partial mitochondrial cox1 gene sequences) and morphological (shell and radular tooth) characters revealed that the samples collected by dredging in deep water during a recent expedition carried out in the Mozambique Channel are different from the samples collected in the Pacific Ocean. We thus introduce here a new species, Afonsoconus crosnieri sp. nov., from the SW Indian Ocean including records from the Mozambique Channel, the Comoros and Glorieuses Islands, Madagascar, South Africa and Reunion Island.

High genetic differentiation and low connectivity in the coral Pocillopora damicornis type β at different spatial scales in the Southwestern Indian Ocean and the Tropical Southwestern Pacific

Studying genetic connectivity in marine populations aims to understand the dispersal of an organism through the seascape and thus its gene flow. Here, we focused on one lineage of the recently revised coral Pocillopora damicornis complex, P. damicornis type β, corresponding to Primary Species Hypothesis PSH05 in Gelin et al. (Mol Phylogenet Evol 109:430–446, 2017b): it had been hypothesized that P. damicornis type β encompasses four distinct lineages, representing Secondary Species Hypotheses (SSH05a, SSH05b, SSH05c and SSH05d). The aim of the present study was to confirm this partition and to infer the genetic structuring and connectivity among 27 populations for this widespread and common scleractinian. For this, a total of 1418 colonies were hierarchically sampled from two marine provinces of the southern parts of its distribution range, which remain largely understudied: the Western Indian Ocean and the Tropical Southwestern Pacific. Using 13 microsatellite loci and assignment tests, our findings confirmed the partition into four SSHs, each SSH splitting into clusters, suggesting that P. damicornis type β may represent a complex of cryptic species. Moreover, within each SSH, clonal propagation was evidenced in almost every population, but clonal dispersal was mostly restricted to sampling site (except in Reunion Island and northern Madagascar, where clones were found in several populations approximately 50 km apart). Nevertheless, wherever the cursor of species level is placed (one or several species), populations were highly differentiated both within the Western Indian Ocean and the Tropical Southwestern Pacific, suggesting restricted gene flow at different spatial scales (marine province, ecoregions, islands/regions), leading to diverging lineages.

Tomato leaf curl Mahé virus: a novel tomato-infecting monopartite begomovirus from the Seychelles.

This is the first description of the complete genome sequence of a new monopartite begomovirus isolated from tomato with symptoms of tomato (yellow) leaf curl disease collected in the Seychelles. The DNA-A-like nucleotide sequences share the highest nucleotide sequence identity (84%) with tomato leaf curl Anjouan virus (ToLCAnjV) from the Comoros islands. Phylogenetic analysis confirmed its recombinant nature and its relationship to Old World monopartite and bipartite begomoviruses. This discovery of a new member of a species confirms the high genetic diversity of begomoviruses in the south-western Indian Ocean islands.

First Finding of Melamphaes uniformis (Melamphaidae) in the Southwestern Indian Ocean

The catch of a rare species of Melamphaes uniformis (Melamphaidae) is reported for the first time in the southwestern Indian Ocean near the Walters underwater mountain. This species was previously known only by the holotype caught in the Tasman Sea, the Pacific Ocean.

Evidence of multiple colonizations as a driver of black fly diversification in an oceanic island.

True oceanic islands typically host reduced species diversity together with high levels of endemism, which make these environmental set-ups ideal for the exploration of species diversification drivers. In the present study, we used black fly species (Diptera: Simuliidae) from Reunion Island as a model to highlight the main drivers of insect species diversification in this young and remote volcanic island located in the Southwestern Indian Ocean. Using local and regional (Comoros and Seychelles archipelagos) samples as well as specimens from continental Africa, we tested the likelihood of two distinct scenarios, i.e. multiple colonizations vs. in-situ diversification. For this, posterior odds were used to test whether species from Reunion did form a monophyletic group and we estimated divergence times between species. Three out of the four previously described Reunion black fly species could be sampled, namely Simulium ruficorne, Simulium borbonense and Simulium triplex. The phylogenies based on nuclear and mitochondrial markers showed that S. ruficorne and S. borbonense are the most closely related species. Interestingly, we report a probable mitochondrial introgression between these two species although they diverged almost six million years ago. Finally, we showed that the three Reunion species did not form a monophyletic group, and, combined with the molecular datation, the results indicated that Reunion black fly diversity resulted from multiple colonization events. Thus, multiple colonizations, rather than in-situ diversification, are likely responsible for an important part of black fly diversity found on this young Darwinian island.

Sedimentation adjacent to atolls and volcano-cored carbonate platforms in the Mozambique Channel (SW Indian Ocean)

Recently acquired data from the Iles Eparses (southwestern Indian Ocean) reveal new information about the geomorphology, depositional processes, and sedimentary deposits on the slopes of atolls and atoll-like platforms. The deposits discussed here lie on the deepwater flanks of isolated, inactive volcanos that are capped by shallow, relatively flat carbonate platforms 45–210 km2 in area. Much of the slope geomorphology is controlled by the underlying volcanic edifice. Steep (~25–35°) upper slopes consist of outcrops of volcanic basement, smooth banks, failure scarps, and channels. Sedimentary features seen in the lower slope and proximal basin (2000–3500 m deep) consist of channels, levees, lobes, and mass transport deposits (MTDs). In places, channels terminate 13–18 km from the platform margin, ending in lobes up to 3.5 km across, a feature not often seen in modern carbonates. In the subsurface, MTDs are present near all platforms. Within MTDs, seismic character is variable, often consists of chaotic reflections indicative of sediment gravity flow processes. Subsurface units with organized (retro- or progradational) reflections are interpreted as turbidite lobes or MTDs with compressional features. Core taken within lobes and near the base of slopes reveal decimeter-scale turbidites and debrites composed primarily of graded and massive bioclastic grainstones and packstones with abundant neritic skeletal components, interbedded with hemipelagic aragonitic and clay-rich foraminiferal ooze. Slope depositional processes are therefore primarily gravity-driven and occur at different scales; i.e., bed-scale turbidites and muds may be remobilized and redeposited through slope failure and deposition of large MTDs. Dominant wind direction may also play a role in slope sedimentation: leeward slopes are generally less rugose and show increased sedimentation at the toe of the slope. This study thus provides new insight into depositional systems surrounding atoll-like carbonate platforms, and provides a new analogue for similar deposits in the geologic record.

Cryptic diversity, low connectivity and suspected human‐mediated dispersal among 17 widespread Indo‐Pacific hydroid species of the south‐western Indian Ocean

AbstractAimTo investigate whether the populations of 17 widespread hydroid species are connected on a demographic level (one to few generations) or are mostly connected on evolutionary timescales.LocationCoral reefs of the South‐western Indian Ocean.Taxon17 widespread hydroid species (Cnidaria, Hydrozoa).MethodsUsing mitochondrial (16S) and nuclear (Calmodulin) sequences, we analysed 17 co‐distributed hydroid species with contrasting life history traits (with or without a pelagic life history phase). We used DNA‐based species delimitation methods, haplotype networks, analysis of molecular variance, and Bayesian skyline plots to investigate diversification and connectivity patterns in the region.ResultsPutative cryptic species were revealed in half of the species and the 17 species resulted in 54 cryptic lineages. The high isolation of hydroid populations in the region is underlined by the rarity of shared haplotypes among localities in most of the species studied. In contrast, haplotypes shared between specimens collected in different ocean basins were found in three species and suggest recent introductions via human activities. The presence of a short pelagic dispersal phase did not seem to increase the connectivity levels of the studied populations, as no significant differences in genetic structure were detected between species with contrasting life history traits.Main conclusionsThese results highlight once again our incomplete knowledge of the marine invertebrate fauna, as we might be underestimating hydroid diversity by two‐thirds, and are discussed in terms of diversification processes, dynamics of the Indo‐Pacific biodiversity and the role of its peripheral marine provinces.

Status and trends of albatrosses in the French Southern Territories, Western Indian Ocean

Today albatrosses are threatened worldwide, especially by fishing activities, and many populations are currently in decline. Albatrosses breeding at the French Southern Territories in the south-western Indian Ocean, on the Crozet, Kerguelen and Saint-Paul–Amsterdam island archipelagos, are monitored regularly. This monitoring has been based on a sample of species and sites, and there was a need for an assessment of the population trends for all species at each site. During the past 3 years most populations have been surveyed, allowing an assessment of the trends of albatrosses breeding at the archipelagos of the French Southern Territories over the past 40 years. Wandering Albatrosses show similar trends at all sites within the Crozet and Kerguelen archipelagos, with a recent recovery of colonies after strong declines in the 1970s. Amsterdam Albatrosses are increasing, albeit at lower rates during recent years. Indian Yellow-nosed Albatrosses show a global decline over the entire range. The trends among Black-browed and Grey-headed Albatrosses vary between colonies and archipelagos. Sooty Albatrosses have continuously decreased in numbers whereas Light-mantled Albatross numbers vary considerably between years, with an overall increase over the past 30 years. These results confirm that the French Southern Territories in the south-west Indian Ocean support a significant portion of the world populations of several albatross species. Several species appear to be steadily decreasing probably because of the impact of fisheries and disease outbreaks. The reasons for different trends among populations of the same species are not well understood and require further investigation.

First record and a new species of Sericosura Fry Hedgpeth, 1969(Arthropoda: Pycnogonida: Ammotheidae) from a hydrothermal ventof Southwestern Indian Ridge.

This is the first record of the genus Sericosura from the "Duanqiao" hydrothermal field on the Southwestern Indian Ridge. Collected material included two juvenile specimens temporarily assigned to S. bamberi and S. heteroscela respectively, and one male specimen with dimorphic legs here proposed as a new species, S. duanqiaoensis sp. nov. The discovery suggests potential connectivity among the hydrothermal vents of the Atlantic, Indian and Southern Oceans, expecting obtaining more specimens for further evolutionary studies to clarify the relationships of these hydrothermal vents.

Interdecadal modulation of the Atlantic Multi-decadal Oscillation (AMO) on southwest China’s temperature over the past 250 years

The temperature gradient between southwestern China and Indian Ocean is one key driver of the Indian Summer Monsoon, suggesting the necessity to understand temperature variability in southwestern China. Contrary to the general warming experienced in most of China, a few regions in southwestern China have undergone a cooling trend since the 1950s. To place this cooling trend in a historical context, this study develops an Abies fabri tree-ring width chronology in the Sichuan Basin, the most populated region in southwest China. The chronology spans from 1590 to 2012, with its reliable portion from 1758 to 2012, by far the longest in the Sichuan Basin. To better extract regional climate signals encoded in tree rings with strong local disturbances, we incorporate climate signals of nearby tree-ring chronologies to generate a large-scale tree-ring chronology (LSC). The LSC shows higher correlations with temperature near the sampling site on Mount Emei and sea surface temperatures of the northern Atlantic Ocean than chronologies developed using traditional methods. The highest correlations between the LSC and temperature are found from current February to July in the Sichuan Basin for the period 1901–1950 (r = 0.70), with a sharp decrease afterwards. Interdecadal variations of the LSC match well with Atlantic Multi-decadal Oscillation reconstructions, except for the late nineteenth century and after ~ 1980s. This study provides evidence that southwest China is a transitional region both affected by the interdecadal temperature variations of the northern Atlantic and Asian areas, although their influences weakened in recent possible due to enhanced human activities.

Ocean heat budget analysis on sea surface temperature anomaly in western Indian Ocean during strong-weak Asian summer monsoon

This study presents ocean heat budget analysis on seas surface temperature (SST) anomalies during strong-weak Asian summer monsoon (southwest monsoon). As discussed by previous studies, there was close relationship between variations of Asian summer monsoon and SST anomaly in western Indian Ocean. In this study we utilized ocean heat budget analysis to elucidate the dominant mechanism that is responsible for generating SST anomaly during weak-strong boreal summer monsoon. Our results showed ocean advection plays more important role to initate SST anomaly than the atmospheric prcess (surface heat flux). Scatterplot analysis showed that vertical advection initiated SST anomaly in western Arabian Sea and southwestern Indian Ocean, while zonal advection initiated SST anomaly in western equatorial Indian Ocean.

Year-round movements of white-chinned petrels from Marion Island, south-western Indian Ocean

AbstractWhite-chinned petrelsProcellaria aequinoctialisL. are the most frequently recorded procellariiform species in the bycatch of Southern Hemisphere longline fisheries. Our study investigated the year-round movements of ten adult white-chinned petrels (seven breeders, three non-breeders/suspected pre-breeders) from Marion Island tracked with global location sensor (GLS) loggers for three years. Additionally, 20 global positioning system (GPS) tracks were obtained from breeding white-chinned petrels during incubation (n=9) and chick-rearing (n=11). All GLS-tagged birds remained, year-round, in the area between southern Africa and Antarctica, not making any major east/west movements. Three core areas (50% kernels) were utilized: around the Prince Edward Islands (PEI; incubation and early chick-rearing),c. 1000 km west of PEI (pre-breeding and early incubation) and around South Africa (non-breeding birds). The only area where 50% utilization kernels overlapped with intensive longline fishing effort was off the Agulhas Bank (non-breeding season). Our results confirm the lack of foraging overlap between the two subspecies; nominate birds (South Georgia/south-western Indian Ocean) utilize separate areas toP. a. steadi(New Zealand/sub-Antarctic islands), and thus should be treated as separate management units. Knowledge of the year-round movements of a vagile species, such as the white-chinned petrel, is important for its continued conservation.

Circulation mechanisms responsible for wet or dry summers over Zimbabwe

Climate change has resulted in increased rainfall variability over many parts of the world including Southern Africa. As such, droughts and floods have become a frequent phenomenon in Zimbabwe and have potential to intensify socio-economic stressors. This study examined possible forcing factors behind the occurrence of extreme summer events using re-analysis datasets. Composite analysis and correlation methods were used to identify circulation mechanisms and their strength in determining rainfall patterns in Zimbabwe. Predominantly northerly airflow in the lower troposphere was found to favor wet while southerly airflow favors dry seasons. Negative geopotential anomalies (minimum of −20 hPa) to the west of Zimbabwe in the middle levels characterize wet summers which swing to positive anomalies (+24 hPa) during dry summers. Positive SST anomalies (maximum of 0.4) exist to the southwest of Madagascar extending to the western shore on the Angola-Namibian border characterize wet summers which swing to negative anomalies (−0.2 oC) during dry summer seasons. SST anomalies in the South western Indian and South eastern Atlantic oceans are crucial in the determination of the strength of both the South Indian and Atlantic Ocean high pressure systems which in turn control moisture advection and convergence into Zimbabwe during the summer period. If these SST anomalies at lag times of about 3 months can be used to predict the incoming summer circulation patterns then the accuracy of summer seasonal outlook forecasts can be improved. Studying the mechanisms behind drought and flood occurrence is important to the country which is in the process of downscaling regional prediction products to improve the accuracy of seasonal forecasts. These findings are useful in crafting relevant measures to maximize the benefits and minimize the risks of extreme rainfall events.

Decolonizing Pathways Through Indigenous Education: Native Student Conceptions of Nation Building

Decolonizing Pathways Through Indigenous EducationNative Student Conceptions of Nation Building Leola Tsinnajinnie Paquin (bio) Celina listened intently at a celebratory event while a political leader of her Native1 Nation spoke enthusiastically about the opening of its newest economic enterprise: a gas station.2 She attended this presentation armed with knowledge about Native sovereignty and nation building attained through her studies at the Southwestern Indian Polytechnic Institute (SIPI) a federally operated college for American Indians (AI) in Albuquerque, New Mexico. An eager learner concerned about AI issues, she took as many Native studies-oriented courses as possible at SIPI. Celina had obtained an Indigenous-oriented education made possible in large part by the rise of Native American Studies programs across the nation resulting from Indian demands for culturally relevant education in post-secondary institutions.3 A faculty-driven movement at SIPI sought to establish a strong Native nation building foundation within the framework of the college's general education program. That objective of empowering Natives with useful [End Page 93] knowledge eventually became a value that transcended all facets of SIPI.4 Although SIPI did not offer a specific degree in Native American Studies (NAS), its curriculum included a number of courses with Native content. Those offerings enabled her and her advisor to develop a program of study within an NAS framework to accommodate her career goal (to teach Native children). Thus, she exemplified this vision in terms of what qualities and Indigenous-centered perspectives a Native Nations community college graduate should embody. Returning to Celina's thoughts while at the gas station, as the political leader's speech gained momentum he proclaimed that the business represented an act of nation building. Because Celina understood that the new enterprise was solely a profit-making venture, she reached a conclusion saying to herself: "That is not nation building." INTRODUCTION What is nation building? This article explores the perspectives of a group of students at Southwestern Indian Polytechnic Institute in 2014 during a time of cultural revitalization and upon the restoration of Higher Learning Commission (HLC) accreditation. As demonstrated by the vignette, nation building has become a popular term in academia as well as in the words spoken by Native leadership. From the vantage point of various roles, but primarily as an educator, I wanted to uncover how nation building was articulated through the eyes of tribal college students who: studied nation building curriculum; heard from the experiences of speakers invested in Indigenous communities; engaged in service learning projects that served Native children; and who were immersed in an educational setting that was grounded in valuing the sovereignty of tribal nations. Celina shared her story with me during an interview. She was a key participant in a phenomenological study that was completed shortly after the gas station event described above. The purpose of the study was to capture the collective phenomenological experience and pay tribute to the many projects that led to the accomplishments of students like Celina. These students shared the common experience of taking a set of Native Studies–centered courses and attending SIPI from 2013–14 during a general education movement in cultural relevancy. These [End Page 94] courses were designed to establish an understanding of nation building through Indigenous education pedagogy. The research study sought to answer the question "How do Indigenous students plan their academic, career, and cultural goals in relationship to nation building in practice?" The use of the word "practice" was to highlight the theme of what nation building really looks like to those who serve Native communities. Furthermore, the study explored three subquestions. How do students define nation building? What are the core values that guide student engagement with nation building as a learning process? Do students identify and apply decolonization in this process? My hope was that the students who took the courses could demonstrate immediate applications of the lessons they learned to their future trajectory. In Celina's case, she based her assessment of the gas station on the readings, guest presenters, lectures, discussions, and, most significantly, her participation in service learning projects. In her mind, nation building encompassed the finding of common ground and unity, education, core values, community, self...

DNA barcoding post-larvae can improve the knowledge about fish biodiversity: an example from La Reunion, SW Indian Ocean

The aim of this study was to demonstrate that fish larvae identified using their COI sequences offer a unique opportunity for improving the knowledge of local fish richness. Fish larvae were sampled at the end of their pelagic phase using light-traps set off the West Coast of La Reunion Island, southwestern Indian Ocean, once per month from October 2014 to March 2015. Among the 5174 larvae caught, 214 morphologically different specimens were selected, 196 successfully barcoded, giving a total of 101 different Barcode Index Numbers (BINs). Among these BINs, 55 had never been recorded in La Reunion exclusive economic zone (EEZ), and 13 were new for the BOLD database. Even if the sampling effort for collecting fish post-larvae during this study was relatively low, it allowed adding at least nine new species to an updated checklist of fishes of La Reunion EEZ.