African Coast Research Articles

The effects of gravity waves on ozone over the Tibetan Plateau

The ozone valley over the Tibetan Plateau (TP) has an important effect on global weather and climate. As a significant source of atmospheric gravity waves (GWs), TP is also a key area of global stratosphere-troposphere exchange (STE), yet the exploration of the causes of low ozone values over the TP has been scarce from the perspective of GW. In this paper, we used the hyperspectral Atmospheric Infrared Sounder (AIRS) data to extract GWs and deep convection over the TP and analyzed the statistical characteristics of ozone for corresponding events. The results show that: (1) The GWs observed by AIRS mainly occur in the mid-latitude region, with a maximum frequency of >10%, and their intensity varies with longitude. Three large-value regions have been identified on the coast of Southeast Asia, Central America, and Central Africa. (2) Most deep convection occurs in the Intertropical Convergence Zone (ITCZ), with three large value centers in the East Asian monsoon region, Central America and Central Africa. Among them, the Indian monsoon region, the Northwest Pacific region to the east of the Philippines, and the western side of the South China Sea (SCS) are the large-value areas within the East Asian monsoon region, with the maximum occurrence frequency exceeding 15%. (3) TP is a region with a large frequency of convective gravity waves. In most areas of the southern foothills of the TP, the frequency of GWs related to convection is 30%–50%. Almost all deep convection over the TP and its adjacent areas are accompanied by GWs, with a frequency of 60–90%. (4) The composite analysis results show that the occurrence of GWs or deep convection is accompanied by negative anomalies of ozone in most areas of the southern foothills of the TP, indicating a decrease in the integrated column amount of ozone. (5) By analyzing the anomaly distribution of meteorological elements such as cloud fraction, cloud top height, tropopause height, and outgoing longwave radiation (OLR), the results show a dual effect in the presence of GWs or deep convection. The effect involves not only an increased generation of clouds, conducive to convection but also elevated cloud top height, promoting the formation of high clouds, some even beyond the tropopause. In addition, the occurrence of GW or deep convection can also affect the tropopause height, strengthen convective activity, and facilitate the upward transfer of low-concentration ozone from the lower layer to the upper layer, thereby causing a decrease in the integrated column amount of ozone.

Local adaptation with gene flow in a highly dispersive shark.

Adaptive divergence in response to environmental clines are expected to be common in species occupying heterogeneous environments. Despite numerous advances in techniques appropriate for non-model species, gene-environment association studies in elasmobranchs are still scarce. The bronze whaler or copper shark (Carcharhinus brachyurus) is a large coastal shark with a wide distribution and one of the most exploited elasmobranchs in southern Africa. Here, we assessed the distribution of neutral and adaptive genomic diversity in C. brachyurus across a highly heterogeneous environment in southern Africa based on genome-wide SNPs obtained through a restriction site-associated DNA method (3RAD). A combination of differentiation-based genome-scan (outflank) and genotype-environment analyses (redundancy analysis, latent factor mixed models) identified a total of 234 differentiation-based outlier and candidate SNPs associated with bioclimatic variables. Analysis of 26,299 putatively neutral SNPs revealed moderate and evenly distributed levels of genomic diversity across sites from the east coast of South Africa to Angola. Multivariate and clustering analyses demonstrated a high degree of gene flow with no significant population structuring among or within ocean basins. In contrast, the putatively adaptive SNPs demonstrated the presence of two clusters and deep divergence between Angola and all other individuals from Namibia and South Africa. These results provide evidence for adaptive divergence in response to a heterogeneous seascape in a large, mobile shark despite high levels of gene flow. These results are expected to inform management strategies and policy at the national and regional level for conservation of C. brachyurus populations.

Post-mortem ‘soft flesh’ in three commercial fish species from off Atlantic Morocco associated with the myxosporean parasites Kudoa thyrsites and K. encrasicoli (Myxozoa)

Small pelagic fishes represent one of the most important food resources off the Northwest coast of Africa. Despite their economic significance, little is known about the infections with flesh invading myxosporean parasites of genus Kudoa (Cnidaria, Myxozoa). Heavy infections in the flesh may be associated with post-mortem myoliquefaction, commonly known as ‘soft flesh’. This condition may reduce the quality and marketability of the fish fillet, resulting in both economic losses to the fishing industry and loss of consumer confidence. In this study, we investigated Kudoa-induced ‘soft flesh’ occurrence in European anchovy Engraulis encrasicolus, European pilchard Sardina pilchardus, and Atlantic chub mackerel Scomber colias caught in 2019 off the Moroccan Atlantic coast. Five hundred specimens of each fish species were examined for ‘soft flesh’ by texture testing and visual inspection 48 h post-catch. ‘Soft flesh’ occurred in 0.2 % of the European anchovies, 1.4 % of the European pilchard, and in 4.4 % of the Atlantic chub mackerel. Microscopic examination of muscle samples revealed that ‘soft flesh’-affected fish were infected with myxospores of K. thyrsites-like morphotype. Analysis of the kudoid SSU rDNA sequence obtained from European pilchard and the Atlantic chub mackerel identified these as K. thyrsites (100 % identity), whereas analysis of the sequence from European anchovy identified the presence of K. encrasicoli (100 % identity). Even if there are no known human health consequences associated with the ingestion of these Kudoa species, the unsightly appearance of some infected fillets is a food quality issue, that can eventually lead to reduced marketability and value.

African Agency and Colonial Committees at Fourah Bay College

Fourah Bay College was the first Western-style university to be established along the West African coast in 1827. Primarily used to train missionaries and traders operating in British West Africa, it remained one of the premier educational establishments, overlooking the docks of Cline Town in Freetown, Sierra Leone. Following the Colonial Development and Welfare Acts and civil unrest in the aftermath of World War II, British colonial policy began to fund a series of secondary and tertiary education institutions. Modeled on the new University of the West Indies, these new universities adopted the residential college dorm typology coupled with the latest modernist architecture designed to enhance climatic comfort.A new campus was proposed for Fourah Bay, and in contrast to earlier precedents, the architectural approach was to be more humble and less monumental. Following a masterplan by London-based architects Norman and Dawbarn, the much smaller and relatively unknown British practice of Frank Rutter was appointed to design most of the campus buildings. The centerpiece is a large concrete tower named after John F. Kennedy, symbolic of the shifting political posturing for control and influence. Following Independence in 1961 and with increasing technical aid offered to neighboring Ghana and Nigeria from Socialist Eastern European powers, Fourah Bay College demonstrated how these political attempts for influence were directly played out through these newly formed institutions. Fourah Bay College also reveals the African agency in appointing architects and who was able to control the procurement processes and design teams. Rutter was dismissed as ‘college architect’ by a small contingent of newly qualified Sierra Leonean architects eager to ensure local appointments and architectural expressions were given opportunity. The campus, with its impressive architectural structures and innovative solutions, mirrors the political flux and shifting global power structures of the late 1950s and early 1960s, along with the local agency of Freetown architects and their quest to shape the future.

Lophelia reefs off North and West Africa–Comparing environment and health

The health status of cold-water coral reefs on the West African coast was investigated with the main objective of obtaining knowledge of the adaptive capacity of Lophelia pertusa to environmental stressors. Three coral sites were studied, in Northern Morocco, in the Morocco/Mauritania region (both in 2020) and, in the Ghana and Ivory coast region (visited in 2012, 2017, and 2019). Area cover of live colonies, explored through underwater videos, was used as an indicator of reef health and compared with the environmental variables: reef position, depth, water mass, temperature, dissolved oxygen concentration (DO), carbonate chemistry (pH, aragonite saturation (ΩAr), macronutrients and particles (visual). For a broader picture of the adaptations presented by Lophelia our results were compared with reefs in contrasting environments. Off Ghana and Mauritania healthy reefs (i.e., having areas with more than 20 % cover of live colonies) were found to reside at DO concentrations between 1.1 and 1.6 ml L−1, in corrosive waters (pH 7.7 and ΩAr 1.0) with high nutrient concentrations. By contrast, the reefs off the North of Morocco, sitting in well-oxygenated waters with oversaturated ΩAr, had no or few live colonies. Our findings together with data from other studies show that Lophelia has a wide tolerance to hypoxia and acidification, and that in relation to climate change increased temperature and silting could pose more serious threats. These findings highlight the importance of continued studies of Lophelia reefs in contrasting environmental conditions to better understand their adaptation potential to climate change-related stressors.

The vegetation of Holocene coastal dunes of the Cape south coast, South Africa.

The vegetation of calcareous coastal dunes of Holocene age along the south coast of South Africa's Cape Floristic Region is poorly described. This vegetation comprises a mosaic of communities associated with two biomes, Fynbos and Subtropical Thicket. Previously, expert knowledge rather than quantitative floristic analysis has been used to identify and delimit vegetation units. In many areas, mapped units conflate vegetation on Holocene sand with that on unconsolidated sediments of late Pleistocene age, despite pronounced species turnover across this edaphic boundary. Despite dominance by Cape lineages and fynbos vegetation, dune vegetation in the eastern part of the region has been included in the Subtropical Thicket Biome rather than the Fynbos Biome. The high levels of local plant endemism associated with this dune vegetation and the small and fragmented configuration of these habitats, makes it an urgent conservation priority especially when placed in the context of rising sea levels, increasing development pressures and numerous other threats. Here we provide a quantitative analysis of 253 plots of the 620 km2 of Holocene dune vegetation of the study area using phytosociological and multivariate methods. We identified six fynbos and two thicket communities based on the occurrences of 500 species. Following a long tradition in Cape vegetation typology, we used the Strandveld (beach vegetation) concept as our first-order vegetation entity and identified six units based on the fynbos floras. These were, from east to west, Southeastern Strandveld, St Francis Strandveld, Goukamma Strandveld, Southwestern Strandveld and Grootbos Strandveld. Each unit was differentiated by a suite of differential species, most being Holocene dune endemics. The two thicket communities-Mesic and Xeric Dune Thicket-showed limited variation across the study area and were subsumed into the Strandveld units. We discussed our findings in terms of vegetation-sediment relationships, emphasizing the need for a greater geographical coverage of sediment ages to facilitate a better understanding of deposition history on vegetation composition. We also discussed the role of soil moisture and fire regime on structuring the relative abundance of fynbos and thicket across the Holocene dune landscape. Finally, we address the conservation implications of our study, arguing that all remaining Holocene dune habitat should be afforded the highest conservation priority in regional land-use planning processes.

Virtual coastal altimetry tide gauges along the West African coast

Low-lying coastal regions are generally vulnerable to climate change, and particularly to sea level variations. Understanding how these variations affect the coastal population requires an access to sea level measurements. Good quality in-situ sea level data are seldom available, with most long, research quality data in Europe and North America. In contrast, satellite altimetry provides more than three decades of near-global, continuous and freely available sea level measurements. Thanks to recent advances in processing and instruments, these observations have now become reliable to a few kilometers from the coast. In this study, using the available in-situ tide gauge data as a reference, we explore the ability of the recent X-TRACK/ALES high-resolution coastal altimeter product to derive the ocean tide and the long-term sea level changes along the West African coast. This region was chosen because it is under-sampled in terms of in-situ observations and would benefit greatly from the availability of freely accessible satellite data sets. To select the altimetry observations closest to the coast, we first define virtual tide gauges as close as possible to the intersection between each satellite track and the land. Sea level anomalies derived from the virtual stations were observed to be similar to those from the corresponding tide gauge stations: correlation values are between 0.58 and 0.78, root mean square differences between 5.6 and 8.3 cm. The virtual stations reproduce the observed tide with errors less or equal to 6.5 cm (i.e. 5.8% or less than the sea level variations of the tide). We show that part of the differences in tides between the two datasets is explained by differences in position between tide gauges and virtual stations. The combined analysis of sea level trends derived from tide gauges and from virtual stations shows how it is an efficient strategy to correct their respective errors and progress towards increasingly accurate sea level trend estimates in a region with little or no research-quality tide gauge data suitable for long-term sea level studies. The conclusion from this study is that in coastal regions poorly covered by tide gauges, our altimetry-based approach can be used to study and monitor sea-level variations related to tides or to long-term sea level changes.

Piracy in the Gulf of Guinea and the Role of African Regional Organisations in Ensuring Security of Maritime Shipping

The first decade of the XXI century witnessed a rise in piracy in some regions of the world, including the Gulf of Guinea. The purposes of this article are to find out historical reasons of the emergence of piracy in off the West coast of Africa and to analyse the participation of African regional organisations in the struggle for ensuring security of maritime shipping in the Gulf of Guinea. The initial surge in incidence of attacks against merchant ships was caused by anti-governmental groups, which adopted pirate tactics. Later, piracy off the shores of Central and West Africa turned into a profitable type of organised crime. Pirates of the Gulf of Guinea inflicted significant damage to economic development of the countries of the region and began to pose a threat to shipping off the West African shore of the Atlantic. The article describes how interregional cooperation with external partnership was organised to counter transborder nature of pirate activities. Based on regional organisations, specifically, the Economic Community of Central African States (ECCAS) and the Economic Community of West African States (ECOWAS), the maritime security summit held on June 24–25, 2013 in Yaoundé adopted the Code of Conduct, which contained a list of measures to combat piracy. The Code of Conduct envisaged close cooperation among the nations of Central and West Africa with help of “external” partners in order to ensure rapid reaction to counter pirate attacks. Research of the problem indicates that only consecutive realisation of these measures allowed to reach a tangible result almost 10 years later, namely, in 2022. Nevertheless, if control over waters of the Gulf of Guinea is weakened, piracy may resurge, because its social and economic roots still exist.

A little bit of Sargassum goes a long way: seafloor observations of Sargassum fluitans and Sargassum natans in the Western Atlantic Ocean

The North Atlantic Ocean features high seasonal productivity of the brown seaweed Sargassum, which floats on the ocean surface and accumulates in large numbers in the Sargasso Sea. Sargassum blooms can stretch from the west coast of Africa to the Gulf of Mexico, and have created the largest seaweed blooms ever observed. Sargassum blooms have increased in intensity in recent years, and can negatively impact coastal communities when they wash up onshore in large quantities and decay. While seaweed sinking from surface waters to the seafloor may be an important carbon sink by removing carbon from the atmosphere, the magnitude of carbon sequestration by Sargassum and other macroalgae remains poorly understood. Given the magnitude of Sargassum blooms in the North Atlantic, they may pose a significant mechanism for carbon sequestration in the deep sea, though direct observations are rare. In this study, we documented the presence and distribution of Sargassum seaweed on the seafloor using video from ten remotely operated vehicle dives conducted on NOAA Ship Okeanos Explorer. Locations included sites in the Gulf of Mexico, in the Caribbean Sea, and off the Southeastern United States. Sargassum was observed in numbers ranging from 0 to over 112 per dive, and a frequency of between 0-11.23 observations for every 100 meters of horizontal distance. These observations suggest that Sargassum does make its way to the deep sea in potentially significant amounts. Natural systems like Sargassum sinking could serve as natural laboratories for understanding and managing seaweed burial as a climate mitigation strategy. Long-term monitoring of the fate of sunken Sargassum on the seabed is needed in order to determine how much is ultimately sequestered rather than recycled back into the system. Such observations would inform the feasibility of Sargassum farming and/or facilitated sinking as potential carbon dioxide removal strategies.

Inference on the biological history of the Comoros archipelago using the CD4 Alu/STR compound system

The Comoros Archipelago is located at the northern end of the Mozambique Channel between Madagascar and the East African coast. Its settlement would have been influenced by contacts and possibly migratory waves that would have come from the East African coast, Middle East and Southeast Asia. This finding was the conclusion of various previous genetic studies carried out on Comorian populations to answer the question of its settlement and its biological history. These studies have used many kinds of molecular markers, although the autosomal markers (Alu/STR CD4) used in the present study have never been studied on the archipelago's populations. Nevertheless, they have been used on populations all over the world and have provided valuable information on genetic affinities and differentiation between populations and have also shed more light on the origins of modern human.In this study, we aimed to characterize for the first time the populations of the 3 main islands of the Comoros Archipelago using the CD4 Alu/STR compound system. Due to its robustness, this system allowed us to include, in our comparative analyses, populations having shared a common history with Comoros islanders (through migrations, commercial relations, or others).Our results showed by island, peculiar frequencies of STR and Alu alleles, as well as haplotypic ones. Genetic diversity values at the allelic level, ranged between 0.798 and 0.836 for the STR, and between 0.254 and 0.327 for the Alu. The most frequent haplotypes were 85+, followed by 115+ and 120+ in all the three islands. Phylogenetic and comparative analyses highlighted that our populations exhibit more affinities with sub-Saharan populations especially the Kenyans. However some Middle Eastern signals are perceptible in Anjouan Islanders through 90+ and 110− haplotypes.Finally, the results obtained contribute to a further understanding of the biological history of the Comoros population and provide new insights into the gene flows such as haplotypes of Middle Eastern origin.

Cryptic diversity and phylogeographic patterns of Deto echinata (Isopoda: Detonidae) in southern Africa

Recent phylogeographic studies of poorly-dispersing coastal invertebrates in highly biodiverse regions have led to the discovery of high levels of cryptic diversity and complex phylogeographic patterns that suggest isolation, geological, and ecological processes have shaped their biodiversity. Studies of southern African coastal invertebrates have uncovered cryptic diversity for various taxa and phylogeographic patterns that, although sharing some similarities across taxa, do differ. These findings underscore the need for additional studies to better understand the biodiversity levels, distributional patterns, and processes responsible for producing coastal biodiversity in that region. The coastal isopod Deto echinata is of particular interest, as its complex taxonomic history, poor dispersal capabilities, and broad geographic distribution suggest the potential for cryptic diversity. We use mitochondrial and nuclear sequences to characterize D. echinata individuals from localities ranging from northern Namibia to Glentana, about 2,500 km along the coastline on the south coast of South Africa. These are used to assess whether D. echinata harbors cryptic genetic diversity and whether phylogeographic distributional patterns correlate with those previously documented for other coastal isopods in the region. Analysis of mitochondrial and nuclear sequences revealed two deeply-divergent lineages that exhibit a distributional break in the Cape Peninsula region. These findings suggest D. echinata is a cryptic species complex in need of taxonomic revision and highlight the need for further taxonomic and phylogeographic studies of similarly poorly-dispersing coastal invertebrates in southern Africa.

Deep Learning Approaches for Disease Detection in Groundnut Crops using CNN Models

A major oilseed crop grown in tropical and subtropical parts of the world, groundnuts are a major crop in India. In the sixteenth century, groundnuts were likely transported from Brazil to West Africa, later making their way to India and the African east coast. According to earlier research, various strategies are employed to prevent diseases of groundnut leaves. The main methods include artificial intelligence (AI), machine learning (ML), convolutional neural networks (CNN), and more. Several CNN techniques for leaf disease identification and methodology will be employed in this study. Different CNN models, such as MobileNet, VGG-16, and EfficientNet, are compared to determine which model is most frequently used to identify leaf disease. The accuracy and precision will be computed and presented as a result of utilizing the dataset.

Byron and Slavery

Byron makes frequent references to slavery in his work. The word ‘slave’ occurs some 160 times in his verse and peppers his letters and journals. The aspect of slavery that most concerns twenty-first-century readers in Western democracies (the fifteenth- to nineteenth-century transatlantic trade in enslaved people between the west coast of Africa and the east coast of the Americas) accounts, however, for only a fraction of Byron’s subject-matter concerning this topic. In his hands this is a wide-ranging and complex subject, relating not only to historical and political matters in different geographical locations, but also to metaphorical, personal and emotional themes. This essay therefore begins by looking at Byron’s biography and writing to outline his own connections with transatlantic slavery and with people impacted by enslavement, and then moves on to make what can only be a very modest attempt to consider his writing about slaves and slavery more generally.

Clientage, debt, and the integrative orientation of non-elites on the East African Swahili coast

Ceramic trends on Unguja Island in Zanzibar, Tanzania provide insights into non-elite political strategies on the East African Swahili Coast. Synthesizing imported ceramic data from two seasons of systematic field survey across rural Unguja with historical, ethnographic, and archaeological evidence from coastal East Africa, this paper argues that an integrative orientation toward power characterized bottom-up action on the Swahili Coast over the second millennium CE. While theories of bottom-up action have emphasized commoner autonomy and resistance to clientage, debt, and social inequality, evidence from the Swahili Coast attests to efforts by non-elites to seek entrance into cycles of reciprocal obligation as a means for recognition and social mobility—a specifically non-egalitarian orientation toward power. In response, elites competed with one another to accumulate wealth-in-people, resulting in a competitive patron-client system that prevented political consolidation. Elucidating these dynamics contributes to an understanding of how non-elite political strategies have shaped sociopolitical systems globally.

Bedform characteristics and implications for seafloor-bottom current interactions along the Wild Coast shelf, South Africa

Antecedent conditions and geology influence bedform dynamics and other sea-bed bottom current interactions on the continental shelf. However, the nature of this influence has not been well constrained, particularly on current-swept shelves. A variety of bedforms (narrow and broad sediment ribbons, comet marks and subaqueous dunes) are revealed by high resolution multibeam bathymetry and side scan sonar surveys of the mid-to outer “Wild Coast” shelf along the east coast of South Africa. The bedforms demonstrate a relationship to the geological framework of the shelf.The various bedforms occur in conjunction with bedrock-incised valleys and topographic depressions filled with transgressive sediment and bounded laterally by prominent rocky outcrops. These sediment sources are siphoned and mobilised by the Agulhas Current to create the contemporary shelf bedforms. Mechanisms of bedform development are associated with the interplay between the loci of sediment supply and associated grain size on the one hand and the current velocity and pathway of the Agulhas Current on the other.Sediment ribbons form parallel to the flow path of the Agulhas Current in narrow or broad forms that can be differentiated primarily by sediment grain size. With increased sediment availability from nearby bedrock-bound depocenters these transition along shelf to 2D dunes. A cross-shelf transition to 3D dunes on the outer shelf is marked by increased current velocity, grain size and decreased sediment availability outside of rock-bound depocenters. Rock outcrops affect current velocity and flow paths sufficiently to favour localised deposition over sediment stripping from the shelf. Comet mark forms develop from interactions between availability of finer sediment and perturbations of current flow paths by rock outcrops. This creates conditions that favour localised sediment scouring over deposition.With variability in sediment size, grain size and current flow, dunes fluctuate between active (sharp crested), inert (round crested) and degraded (flat crested) states. A lack of available sediment to replenish outer shelf dunes sees prolonged stasis, eventual dune splitting and breakdown under progressive current influence. Mid-shelf dunes have a greater capacity to recover from periods of stasis and short-term degradation due to greater availability of sediment.Dune migration rates are slower than previous regional estimates. Reasons for this are inconclusive and may be multifaceted. Possible reasons include inertial constraints, prolonged downcurrent reformation periods and longer dune relaxation associated with coarser grain sizes and a paucity of sediment on the outer shelf coupled with the Agulhas Current core migrating further in and offshore. This may explain the stability of the large barchan dunes and reduced movement of other sharp crested dunes relative to the regional migration rates.

An Outport for Gedi?—Archaeological Survey in Mida Creek, Kenya

Communities of the East African coast have had a long history of international interaction. Swahili maritime networks linked African port towns across the Indian Ocean seaboard, thus enabling merchandise to reach the hinterlands of the continent. One of these Swahili towns is the ancient city of Gedi, located on the central Kenyan coast near the medieval town of Malindi. Located inshore, 6 km from the main ocean to the southeast and 3 km from Mida Creek to the southwest, Gedi’s lack of seaward connectivity has perplexed scholars. To effectively function within the vibrant Indian Ocean maritime trade networks of the 10th to 16th centuries CE, Gedi needed access to the sea. Inevitably goods had to be transported overland from a port or landing place. The ‘MUCH to Discover in Mida Creek’ project carried out an archaeological survey around the Creek to form a broader understanding of the region’s maritime past. The study identified a range of sites that evidence past coastal activity. In particular, a concentration of contemporary house sites at Chafisi near the closest point on the Creek to Gedi would suggest it may have acted as an outport for the stone town.

First report of Fusarium wilt of Cavendish bananas caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 in the Grande Comoros Island.

Fusarium wilt of banana, caused by the soil-borne pathogen Fusarium oxysporum f. sp. cubense (Foc), is a major constraint to banana production worldwide (Viljoen et al., 2020). Currently, Cavendish bananas are severely affected by Foc Tropical Race 4 (TR4) globally. In Africa, Foc TR4 was first detected in northern Mozambique in 2013 (Viljoen et al., 2020), and has since been found on the island of Mayotte in the Mozambique Channel off the coast of southeastern Africa (Aguayo et al., 2021). In early 2023, severe leaf-yellowing and wilting of Cavendish banana plants was observed on Cavendish banana plants at several small holder farmer properties in Grande Comoros (Ngazidja) including in Ntsinimoipanga (-11,790054 S, 43°25'47,04384 E), Batou (-11,499716 S, 43°21'51,71976''E), Madjeweni (-11,8217 S , 43°16'41''E) and Mdé (-11°41'54'' S, 43°15'20''E). When the pseudostems of these plants were split open, a reddish-brown internal discoloration of the vascular tissue became apparent. Discolored strands of diseased plants were collected, and the causal agent identified using DNA-based techniques, vegetative compatibility group (VCG) analysis and pathogenicity testing. The samples were plated onto potato dextrose agar and single-spored and isolated from individual diseased plants identified as F. oxysporum based on cultural and morphological characteristics. These include the production of white fungal colonies with a purple center, infrequent production of macroconidia, but an abundance of microconidia on short monophialides, and terminal or intercalary chlamydospores (Leslie and Summerell, 2006). Foc TR4 was identified from seven isolates by conventional (Dita et al., 2010) and quantitative-PCR (Matthews et al., 2020), and with loop-mediated isothermal amplification (LAMP) (Ordóñez et al., 2021). All seven isolates were confirmed as members of the VCG 01213/16 complex when nit-1 mutants of the unknown Foc isolates were compatible with Nit-M mutants of the Foc VCG 01213 and VCG 01216 tester strains. Two isolates were then selected for pathogenicity testing, and 2-month-old tissue culture-derived Cavendish plants (cv. Williams) inoculated by using the method described by Ndayihanzamaso et al. (2022). After 4 weeks, the Foc TR4-inoculated plants produced wilting symptoms and internal rhizome discoloration typical of Fusarium wilt. Foc TR4 was reisolated from the inoculated plants and identified by qPCR (Matthews et al. 2020), thereby fulfilling Koch's postulates. These results provide scientific proof of the presence of Foc TR4 in a second island in the Comoros archipelago. Comprehensive surveys will be conducted in all three of the Comoros Islands to assess the presence and impact of Foc TR4 to implement containment strategies. Collaborative initiatives and coordinated actions among growers and other stakeholders are needed to prevent the spread of Foc TR4 to more Southwest Indian Ocean islands and countries on the East African coasts. The importance of banana for food security and livelihoods, and the unique genetic diversity of bananas found on the Comoros islands, requires the eradication and isolation of diseased bananas on the short term, and the screening of local banana varieties for Foc TR4 resistance on the longer term.

Genetic and morphological insights into the Carpobrotus hybrid complex around the world

The genus Carpobrotus N.E.Br. comprises between 12 and 25 species, most of which are native to South Africa. Some Carpobrotus species are considered among the most damaging invasive species in coastal dune systems worldwide. In their introduced areas, these species represent a serious threat to native species and significantly impact soil conditions and geochemical processes. Despite being well studied, the taxonomy of Carpobrotus remains problematic, as the genus comprises a complex of species that hybridize easily and are difficult to distinguish from each other. To explore the population genetic structure of invasive Carpobrotus species (i.e., C. acinaciformis and C. edulis) across a significant part of their native and non-native ranges, we sampled 40 populations across Argentina, Italy, New Zealand, Portugal, South Africa, Spain, and the USA. We developed taxon-specific microsatellite markers using a Next Generation Sequencing approach to analyze the population genetic structure and incidence of hybridization in native and non-native regions. We identified three genetically distinct clusters, which are present in both the native and non-native regions. Based on a set of selected morphological characteristics, we found no clear features to identify taxa morphologically. Our results suggest that the most probable sources of global introductions of Carpobrotus species are the Western Cape region of South Africa and the coastline of California. We suggest that management actions targeting Carpobrotus invasions globally should focus on preventing additional introductions from the east coast of South Africa, and on searching for prospective biocontrol agents in the Western Cape region of South Africa.

Observations on some reproductive features of the threatened limpet Patella ferruginea Gmelin, 1791 in north‐western Mediterranean Italian waters

Abstract Information about the reproductive biology of the threatened limpet Patella ferruginea has been historically restricted to some of the few enclaves where healthy and conspicuous populations still persist, all located on the African coasts of the Alboran Sea, at the extreme south west of the species’ distribution range, in the western basin of the Mediterranean. This paper provides data on sex ratio by size and sex change of the species from specimens in the northernmost extreme of its distribution, between the north east of Sardinia (Italy) and the Gulf of Genoa (Liguria, Italy), where much more restricted and small populations are found. In the study area, the population parameters were found to be quite similar to those known from the Alboran Sea: The ratio between males and females tends to decrease with size and the prevalence of females versus males (i.e. >50% females) from the 60–65 mm size class upwards. Notwithstanding the small sample size (n = 13), several sex changes were observed in 38.5% of specimens. Noteworthy is that this change not only occurred in the male to female direction (considered ‘normal’ for limpet species) but was also recorded in the female to male direction, confirming the complexity of the reproductive mode of P. ferruginea. The evidence of regular gonadal maturation of specimens and the occurrence of sex changes in the area investigated supports the potential viability of the species at its northernmost limit of distribution, where the species has only recently been reported. Such evidence provides important information for the implementation of management and conservation actions, such as restocking initiatives.

Crime, conflict, and commodities: Peruvian piracy and the natural resource curse

ABSTRACT Over the last two decades, Peru has become a global piracy hotspot, eliciting surprise and concern among the international maritime community. Despite increased attention, Peru remains underexamined in maritime piracy research. In this case-study analysis, we brought together two research fields (e.g. maritime piracy and the natural resource curse) to investigate socio-historical factors that accounted for long-term trends in Peruvian piracy. The maritime piracy literature, which largely examines famous sites off the coasts of Africa and southern Asia, identifies several determinants, including state weakness, economic opportunity, and geography. Because Peru is a heavily extraction-dependent state, we also examined mechanisms of the natural resource curse. Considerable overlap in explanatory factors exist. While we found several determinants identified in the maritime piracy literature present in the Peru case, such as state weakness and social conflict, analyses also indicated that mechanisms of the natural resource curse, particularly commodity price volatility and rent seeking, are also positively related to piratical activity. Overall, our findings extend the maritime piracy and natural resource curse literatures and suggest that counter-piracy efforts in Peru critically examine extractive policies for latent effects.