Propagule Dispersal Research Articles

A Frailty Model to Assess Plant Disease Spread from Individual Count Data

Spread of airborne plant diseases from a propagule source is classically assessed by fitting a gradient curve to aggregated data coming from field experiments. But, aggregating data decreases information about processes involved in disease spread. To overcome this problem, individual count data can be collected; it was done in the case of short-distance spread of wheat brown rust. However, for such data, the gradient curve is a limited model since heterogeneity of hosts is ignored and, consequently, overdisper sion occurs. So, we propose a parametric frailty model in which the frailties represent propensities of hosts to be infected. The model is used to assess dispersal of propagules and heterogeneity of hosts.

Predictors of marine genetic structure in the Indo-Australian Archipelago

The spatial genetic structure of marine organisms is related to dispersal and life-history traits, historical processes, current oceanographic connectivity and habitat features. Here, we assessed the relative importance of these factors for the genetic structure of a broad range of marine species in the Indo Australian Archipelago (IAA). We collated published data on 99 marine species from eight taxonomic groups (ascidians, fishes, molluscs, crustaceans, echinoderms, corals, reptiles, and marine plants) and used generalized linear models (GLMs) to estimate the best predictors of genetic structure. Genetic structure was characterized by FST and the number of genetic clusters over the study area. Predictors tested were: the type of genetic markers; the number of marine ecoregions which are a proxy for habitat variation, historical processes and oceanographic features; species dispersal-related traits (i.e., pelagic larval duration-PLD, adult life habit, reproductive strategy, and egg type); and geographic distance separating populations. The genetic structure of marine species across the IAA was best predicted by traits related to dispersal of larvae or propagules and the mobility of adults; and the number of marine ecoregions sampled not distance was also an important predictor, especially in sedentary and free-swimming species. Our findings highlighted the importance of these key traits to help guide decision-making in spatial management and conservation. There were still many gaps in our understanding of genetic structure, both spatially and within certain taxa, and we recommended future genetic studies focus on habitat-forming taxa and sample sites that are representatively nested in each ecoregion within a marine province or a marine realm, over the spatial extent of the IAA.

A new model for settling velocity of non-spherical particles.

The settlement of non-spherical particles, such as propagules of plants and natural sediments, is commonly observed in riverine ecosystems. The settling process is influenced by both particle properties (size, density, and shape) and fluid properties (density and viscosity). Therefore, the drag law of non-spherical particles is a function of both particle Reynolds number and particle shape. Herein, a total of 828 settling data are collected from the literatures, which cover a wide range of particle Reynolds number (0.008-10000). To characterize the influence of particle shapes, sphericity is adopted as the general shape factor, which varies from 0.421 to 1.0. By comparing the measured drag with the standard drag curve of spheres, we modify the spherical drag law with three shape-dependent functions to develop a new drag law for non-spherical particles. Combined with an iterative procedure, a new model is thus obtained to predict the settling velocity of non-spherical particles of various shapes and materials. Further applications in hydrochorous propagule dispersal and sediment transport are projected based on deeper understanding of the settling process.

The Importance of Propagule Dispersal in Maintaining Local Populations of Rare Algae on Complex Coastlines: Padina pavonica on the South Coast of England

On dynamic coastlines, populations of protected algal species with poor dispersal might be especially vulnerable to infrequent recruitment events and local extinction. As a model, we here consider the dispersal of the alga Padina pavonica from the largest remaining and physically isolated enclaves on the south coast of England. A bio-physical model was used to investigate the likely importance of local propagule dispersal in maintaining populations. Dispersal kernels that simulate the position of propagules at different time steps over 5 days were examined from five release sites. Exceptionally steep declines in model propagule density were observed over the first few hours from release, yet over the first day, 75–85% of model propagules remained close to their source but had not reached other enclaves. After five days, the dispersal from source populations ranged from 0 to 50 km, with only ~5% remaining within the source 1 km2 area. Although distances of modelled propagule dispersal might be adequate for maintaining a regional population network, vegetative perrenation also appears to be important for persistence of P. pavonica. For rare and protected species on isolated and energetic coastlines, local conservation efforts, rather than a reliance on a wider meta-population network, remain very important to ensure long-term protection and survival.

Splash-cups, springboards, and sink or swim – Preliminary study of the strategies for vegetative propagule dispersal in Pygmy Drosera

The Drosera of the subgenus Bryastrum, commonly referred to as pygmy sundews are unique to the genus in that all bar one produce vegetative clonal propagules known as gemmae. These gemmae are thought to be dispersed via a novel adaptation known as a splash-cup, but little is known about its effectiveness or other strategies employed by the plants. In this preliminary study, the splash-cup was tested and its effectiveness measured. The role of the stipules, which form the walls of the splash-cup were also examined along with other features of the plants’ architecture. The splash-cup was found to play a critical role in gemmae dispersal while the theory that the stipules perform as spring-loaded catapults was unsupported. Additionally, gemmae were found to either sink or float depending on the taxon. Observational evidence is provided which suggests the structure of a gemma plays a significant role in the success of each taxon in its preferred habitat.

Impact of Weed Managements and Anthropogenic Stress on Quantitative Attributes of Plant Community Composition in Gopegarh Ecopark, Paschim Medinipur, West Bengal, India

Eco-parks are generally set up worldwide for serving both recreational and conservation purposes of local biodiversity through limited maintenance. Gopegarh Eco Park was set by the Forest Department, Government of West Bengal in highlands bank of Kangsabati Kansai) river with a heritage ‘Garh’ area with remnants of Khan Raja’s establishment in Midnapore, West Bengal. This park was a place to study for its rich resources of indigenous vegetation, insects and birds for students and researchers. Increased development for amusements including picnic shades and human accessibility, intense weeding and mud ovens are set up. This study to measure quantitative characteristics of plant communities by quardrat method in low, moderate and severely disturbed zones revealed gradual decrease in indigenous flora with time; specially, herbaceous vegetation. The vegetation is gradually turning towards a monodominant tree community of Acacia auriculiformis, in low and moderate disturbed sites and Anacardium occidentale in severely disturbed sites; both planted earlier. Species frequency, diversity and density are decreasing with stress. The frequent cutting and weeding is affecting intensely on the ecosystem; decreasing soil moisture, organic carbon and changes in pH. This practice may affect propagule formation, dispersal and establishment of herbs, shrub and tree species. The park may gradually lose the indigenous flora and the flora dependant fauna and its utility as in situ sustainable maintenance of biodiversity and a resource place for practical study by students and researchers.

To the canopy and beyond: Air dispersal as a mechanism of ubiquitous protistan pathogen assembly in tree canopies

Cercozoa and Oomycota contain a huge biodiversity and important pathogens of forest trees and other vegetation. We analyzed air dispersal of these protistan phyla with an air sampler near-ground (~2 m) and in tree crowns (~25 m) of three tree species (oak, linden and ash) in a temperate floodplain forest in March (before leafing) and May (after leaf unfolding) 2019 with a cultivation-independent high-throughput metabarcoding approach. We found a high diversity of Cercozoa and Oomycota in air samples with 122 and 81 OTUs, respectively. Especially oomycetes showed a significant difference in community composition between both sampling dates. Differences in community composition between air samples in tree canopies and close to the ground were however negligible, and also tree species identity did not affect communities in air samples, indicating that the distribution of protistan propagules through the air was not spatially restricted in the forest ecosystem. OTUs of plant pathogens, whose host species did not occur in the forest, demonstrate dispersal of propagules from outside the forest biome. Overall, our results lead to a better understanding of the stochastic processes of air dispersal of protists and protistan pathogens, a prerequisite to understand the mechanisms of their community assembly in forest ecosystems.

Weevil Borers Affect the Spatio-Temporal Dynamics of Banana Fusarium Wilt.

Dispersal of propagules of a pathogen has remarkable effects on the development of epidemics. Previous studies suggested that insect pests play a role in the development of Fusarium wilt (FW) epidemics in banana fields. We provided complementary evidence for the involvement of two insect pests of banana, the weevil borer (Cosmopolites sordidus L., WB) and the false weevil borer (Metamasius hemipterus L., FWB), in the dispersal of Fusarium oxysporum f. sp. cubense (Foc) using a comparative epidemiology approach under field conditions. Two banana plots located in a field with historical records of FW epidemics were used; one was managed with Beauveria bassiana to reduce the population of weevils, and the other was left without B. bassiana applications. The number of WB and FWB was monitored biweekly and the FW incidence was quantified bimonthly during two years. The population of WB and the incidence (6.7%) of FW in the plot managed with B. bassiana were lower than in the plot left unmanaged (13%). The monomolecular model best fitted the FW disease progress data, and as expected, the average estimated disease progress rate was lower in the plot managed with the entomopathogenic fungus (r = 0.002) compared to the unmanaged plot (r = 0.006). Aggregation of FW was higher in the field with WB management. WB affected the spatial and temporal dynamics of FW epidemics under field conditions. Management of the insects may reduce yield loss due to FW.

Dispersión y transporte de propágulos micorrícicos en el bosque seco tropical

Los animales son un factor importante en la dispersión de propágulos de los hongos formadores de micorrizas en los ecosistemas de bosque seco tropical. En la presente revisión bibliográfica, se hace énfasis en las diferentes formas de dispersión que pueden realizar los animales por medio de la ingesta o adherencia a estructuras externas para dispersar los propágulos de micorrizas tanto horizontal como verticalmente. La mayoría de las publicaciones provienen de estudios realizados en diversos ecosistemas (tundra, selva, sabanas y praderas), sin embargo, en esta revisión se puso especial énfasis en los estudios que reportan aquellos grupos de organismos que se encuentran en el ecosistema de bosque seco tropical. En el caso de los invertebrados, se evidencia el potencial de dispersión de los hongos micorrícicos en los diferentes estadios de desarrollo de los animales, así como por su movilidad en actividades realizadas para su alimentación y construcción de madrigueras. La dispersión efectiva de hongos micorrícicos se efectúa especialmente por medio de colémbolos, ácaros, lombrices de tierra, nemátodos, hormigas, isópodos, diplópodos, crustáceos, dípteros, avispas, escarabajos y saltamontes. La dispersión fúngica también puede verse favorecida por diferentes grupos de vertebrados, como los mamíferos, aves, reptiles y anfibios. Destacándose principalmente los roedores y las aves, quienes dispersan hongos micorrícicos a largas distancias por el consumo de propágulos adheridos a sus alimentos y estructuras externas. La literatura evidencia la importancia de la fauna en la dispersión de hongos micorrícicos en los ecosistemas de bosque seco. La presente revisión promueve la disminución de las brechas de conocimientos en torno a la dispersión de estructuras fúngicas, dinámicas especializadas y funcionamiento espacial del ecosistema.

Hydrological connectivity drives the propagule pressure of Limnoperna fortunei (Dunker, 1857) in a tropical river–floodplain system

River–floodplain systems are characterized by high connectivity, which favours the spread of non-native species. In floodplain, floods increase connectivity, which increases the similarity of abiotic conditions among environments. High connectivity and low environmental variability may favour the establishment of non-native species such as Limnoperna fortunei, but this has not yet been tested. We sampled L. fortunei larvae in nine connected lakes and nine isolated lakes to rivers in the upper Parana River floodplain to evaluate how spatial (connection) and abiotic (environmental variability) factors affect the larvae density of L. fortunei. We considered the rivers as propagule source of L. fortunei because this invasive species has successfully established in rivers, but not in lakes. Our findings revealed that connected lakes had a high larval density of L. fortunei, while isolated lakes had a low density. Isolated lakes presented a high multi-environmental variability, which was strong negatively related with the larval density of L. fortunei. However, the connectivity decreased the multi-environmental variability, indirectly increasing the larval density of L. fortunei. Our study illustrates that permanent connectivity with invaded environments increase the larvae density of L. fortunei in non-invaded environments, which occurs both directly (through propagule dispersion) and indirectly (by decreasing multi-environmental variability).

Why did some larger benthic foraminifera become so large and flat?

AbstractBiostromes and low‐relief bioherms, some of which are characterized by exceptionally large, flat specimens of larger benthic foraminifera, are common in Palaeogene and Miocene carbonates, most notably those deposited along the Neotethys Seaway and tropical Pacific islands. By incorporating insights from palaeoceanographic research and the biology of living larger benthic foraminifera, a scenario is proposed that can account for palaeontological and sedimentological features while augmenting previous interpretations. Sexual reproduction by gamete broadcasting is common in foraminiferal taxa, including extant Nummulitidae and Amphisteginidae. Resultant zygotes can develop into tiny, resistant, easily dispersed propagules that recruit in suitable benthic‐environmental conditions. The role of algal symbiosis in the biology of larger benthic foraminifera is well‐documented. Palaeoceanographically, such taxa proliferated during times of reduced thermal stratification of the oceans. In regions with exceptionally clear, nutrient‐depleted waters, ‘twilight‐zone’ light penetration was sufficient, at least intermittently, to support some photosynthesis. On outer‐shelf or promontory sites at depths of ca 100 to 200 m, the tiny propagules of larger benthic foraminiferal species, incorporating algal symbionts with the lowest light requirements, could have settled and recruited, growing very slowly, nourished by feeding on bacteria and the limited photosynthate produced by their algal symbionts. Under such conditions, thin microspheric individuals of one or two larger benthic foraminiferal taxa could have survived and grown slowly over several years to very large shell diameters, seldom reproducing asexually. Resulting carbonate accumulation rates would have been very slow, such that even rare disturbances by currents, major storms or internal waves could have produced evidence of winnowing and sedimentary structures. The fossil evidence of such habitats should include biostromes or possibly low‐relief bioherms of low diversity assemblages characterized by abundant, exceptionally large, flat, microspheric larger benthic foraminifera.

Egg morphology may underpin the successful distribution of large branchiopods in temporary waters

Invertebrate species from temporary aquatic ecosystems produce resistant dormant stages (i.e. eggs) that accumulate in long lived mixed egg banks in the sediment. These dormant eggs not only bridge dry phases but also act as propagules for passive dispersal. Large branchiopod crustaceans (e.g. Notostraca, Anostraca and Spinicaudata) produce dormant eggs of variable shapes, sizes and external ornamentation. While these characteristics are often species-specific and have been used in taxonomy, little is known about their ecological significance, for example, their contribution to colonisation success. Here, we explore the idea that variation in egg morphology may impact vector-mediated dispersal and colonisation success of large branchiopods. We studied egg banks from 98 temporary waters across the Northern Cape, South Africa and assessed whether distribution and densities of eggs carried a morphological signal. Overall, our results imply that both size and external structures may impact dispersal to and successful colonisation of temporary waters by large branchiopods. Specifically, our results show that small propagules ( 400 µm), smooth eggs and medium sized (200–300 µm), polygonal eggs were most widely distributed. Ultimately, our approach provides insight in actual colonisation success of species with different egg types and not only on the propensity of the eggs to be picked up and transported by vectors.

Changes in mangroves at their southernmost African distribution limit

Mangroves in South Africa occur at one of the most southerly locations in the world, which provides a unique opportunity to study their dynamic responses to anthropogenic and natural perturbations. The exposed high-energy South African coastline restricts mangroves to 32 sheltered estuaries of which 18 (56%) are predominantly open to the sea. A large area of mangrove (47% of the country total) occurs in the uMhlathuze Estuary – a novel ecosystem formed by the creation of an artificial mouth. A Drivers-Pressures-State-Impacts-Response (DPSIR) framework was applied to understand factors of change and highlight governance and management responses. The largest mangrove area (440 ha) was lost during the construction of Durban Bay harbour. Mangroves (~7 ha) no longer occur in 10 small KwaZulu-Natal estuaries as a result of catchment and mouth disturbance. In the Eastern Cape, pressures are escalating in the form of harvesting for wood, cattle browsing and changes in mouth condition. Climate related warming and an increase in CO2 are positive conditions for mangroves to expand their distribution to higher latitudes but this will depend on propagule dispersal between estuaries and the availability of suitable habitats. Many of the small estuaries are temporarily closed to the sea for different periods thus limiting recruitment. An increase in the intensity of freshwater floods will scour banks and completely remove mangroves. It is important that these dynamic responses are understood and incorporated into management plans so that mangrove forests can be better protected and conserved.

Saltmarsh seeds in motion: the relative importance of dispersal units and abiotic conditions

Propagule dispersal is fundamental to the colonization of new habitats, metapopulation connectivity, and gene flow and thus enables saltmarsh species to cope with global change. In this study, mesocosm and flume experiments were used to quantify the effects of different dispersal units (i.e. seed, spikelet, inflorescence, and plant fragment-containing seeds) and abiotic conditions on the dispersal processes of 4 globally distributed saltmarsh species: Salicornia europaea, Scirpus maritimus, Spartina anglica, and Elymus athericus. The results showed that (1) moving seawater has a species-specific effect on buoyancy, leading to prolonged floatability of high tidal-flat species E. athericus and reduced floatability of pioneer species; (2) tidal currents increase dispersal speed, whereas wind can have additive or antagonistic effects on current-dominated dispersal speed depending on its direction; (3) wave action reduces dispersal speed, but this effect becomes smaller with increasing wave magnitudes and/or applied co-directional wind; (4) dispersal speed may vary depending on the physical forcing and type and morphology of the dispersal units, but the largest species effect is related to the period in which units remain buoyant; and (5) the dispersal potential of saltmarsh species in wind wave-dominated coastal environments can be ordered as follows: E. athericus > S. maritimus > S. anglica > S. europaea. This study provides valuable guidance for future numerical hydrodynamic models of saltmarsh dispersal and establishment, allowing more accurate prediction of the distributional responses of saltmarsh species to climate change, thereby supporting appropriate management and restoration strategies.

Floristic influence of Amazonian Lowland Dense Rain Forest on the pioneer vegetation with marine influence, Restinga of Pará state, Brazil

Abstract The coastal region of the municipalities of Curuçá and Maracanã, on the northeastern coast of Pará, shelters a valuable biological heritage, the last two remnants of Dense Rain Forest on the shores of the Atlantic Ocean. On the Ipomonga Island (Curuçá) and at the Marieta Beach (Maracanã), the Lowland Dense Rain Forest is notable for its abrupt contact with the pioneer formation with marine influence, called as Restinga. This geomorphological interface favors floristic connectivity between different ecosystems. The research objective was to evaluate, through vegetation inventories, whether these forests remnants, about Lowland Dense Rain Forest, are sources of dispersal of woody species in Restinga. A total of 189 species were recorded in 50 botanical families with the greatest richness corresponds to the dense forest (67 species). Of this flora, 46 species (24%) were common to both vegetation typologies, with 18 species considered new occurrences in Restinga of the Amazonian coastal plains. The floristic affinities founded support the effect of Lowland Dense Rain Forest acting as the source for propagule dispersion over the pioneer formation with marine influence (Restinga), mostly dispersed by animals (zoocory).

Isolation of Cryptococcus spp. from several environmental niches in São Luís, MA

Cryptococcosis is an invasive mycosis triggered by a complex of fungal pathogens present in various environmental niches. Cryptococcus neoformans, C. gattii, and emerging pathogens such as C. laurentii and C. albidus are found in aged excreta of Columba livia (pigeon), its natural disseminator. As the pigeon population has increased in São Luís, the objective of this research was to demonstrate the presence of Cryptococcus spp. in the excreta of C. livia in public environments. Twenty-three samples were collected at 14 sites, dispensed into conical tubes, homogenized with saline and chloramphenicol, and allowed to rest until processing. Twenty-four hours after collection, aliquots were distributed in a fungal culture medium and incubated. The macromorphological examination revealed levaduriform, mucoid, bright, isolated colonies compatible with Cryptococcus spp. In the micromorphological examination, 11 of the 23 samples (42.85%) showed the presence of cells with a thick, refringent capsule and mucopolysaccharide around the blastoconidia, typical of Cryptococcus spp. fungi. The other samples (57.14%) were negative for the fungus. The environmental isolation of this fungus in public areas is relevant to public health since the growing pigeon population in São Luís increases the risk of exposure and infection by dispersion of infectious propagules in the environment.

Presencia de Coccotrypes rhizophorae (Curculionidae) en propágulos de Rhizophora mangle (Rhizophoraceae) en el manglar de Sontecomapan, Catemaco, Veracruz, México

Rhizophora mangle es una especie abundante en el manglar de Sontecomapan. Sus individuos presentan el parásito Coccotrypes rhizophorae, perforador de corteza en los propágulos y corteza de R. mangle. Se determinó la abundancia de larvas, juveniles y adultos de C. rhizophorae en propágulos antes de ser dispersados en época de lluvias. El estudio se hizo en el sitio Ramsar 1342 “Manglares y Humedales de la Laguna de Sontecomapan”. A cada propágulo recolectado se le midió la longitud y diámetro medio del hipocótilo, y se determinó la abundancia del parásito en fase de larva, juvenil y adulto. Se encontró diferencia significativa en la abundancia de larvas y adultos de C. rhizophorae en propágulos predispersión en época de lluvias, siendo ausente la fase juvenil. No se encontró tendencia positiva al correlacionar la abundancia de C. rhizophorae en sus tres fases de desarrollo con la longitud y diámetro de los propágulos. Los resultados sugieren que los propágulos predispersión en la época de lluvias son más vulnerables para establecerse y desarrollarse al presentar mayor abundancia de C. rhizophorae.

Combining seascape connectivity with cumulative impact assessment in support of ecosystem‐based marine spatial planning

Abstract Cumulative impact assessment (CIA) is a promising approach to guide marine spatial planning (MSP) and management. One limitation of CIA is the neglect of seascape connectivity, which may spread the impact of localized pressures to ambient areas, e.g. through lost dispersal and recruitment of organisms. We here, for the first time, incorporate seascape connectivity into a traditional CIA model using a connectivity matrix, exemplified by dispersal of propagules estimated through biophysical modelling. Two connectivity impacts are identified: the source impact represents downstream areas losing recruits because of reduced larval dispersal from sites affected by the pressure, and the sink impact represents loss of recruits originating from upstream areas prevented from settlement in the site affected by the local pressure. By including seascape connectivity in the Swedish MSP‐guiding CIA tool Symphony we demonstrate how to practically account for remote effects of local environmental impact. Our example on blue mussel shows how reducing mussel fitness in a given area may have impacts on mussels far from the acting pressures. Overall, results indicate that connectivity impact for blue mussels plays a minor role in most areas, <10% of the ordinary cumulative impact. However, in some smaller areas, e.g. on offshore banks and the Danish Straits, seascape connectivity may increase ordinary cumulative impact with 20%–30%. In an example of scenario‐based CIA analyses of MSP projections, we demonstrate how impacts of particular management actions, e.g. shipping rerouting and wind power developments, can be tracked far from the original area of influence. Depending on the dispersal ability of ecosystem components, a local pressure may impact a considerable area through seascape connectivity, transgressing management units and national borders. Although the mean connectivity impact may be modest for a single ecosystem component, the consideration of seascape connectivity across multiple ecosystem components may significantly alter the mapping of cumulative impact and the assessment of different MSP scenarios. Synthesis and applications. Our extension of Cumulative Impact Assessment offers a new method for mapping and practically integrating seascape connectivity with ecosystem‐based MSP and other spatial instruments for policy making, such as marine protected areas.

Impacts of the yellow River and Qingtongxia dams on genetic diversity of Phragmites australis in Ningxia Plain, China

• The downstream population has a higher genetic diversity than the upstream one. • Gene flow of common reed along the Yellow River is enhanced. • Dams could hinder rhizome floating of common reed along the Yellow River. • Rivers weaken functional and genetic isolations by geographic distances. • Rivers reduce correlation between genetic and functional variation. Rivers favour gene flow by hydrochory and habitat connectivity, and bring heterogeneous selection pressures on genotypes. River regulations (e.g. dams) could influence the hydrologic conditions and then change the effects of rivers on genetic diversity of riverine plants. In Ningxia Plain of China, we investigated the intraspecific variation of Phragmites australis using nine plant functional traits, eleven nuclear microsatellites and two chloroplast DNA fragments. Along the Yellow River for approximately 390 km in Ningxia Plain, we collected P. australis from eleven sampling sites upstream of Qingtongxia Dams and eleven sites downstream. We also added eight sites far from the watercourse in the northwest of Ningxia Plain as the non-riverine population. The downstream population had a higher genetic diversity than the upstream population, but a lower haplotype richness. The downstream population had a weaker genetic differentiation with the upstream population ( Fst = 15.98) than with the non-riverine population ( Fst = 27.76). The same genotype occurred mostly within sites, but two occurred in several sites along the Yellow River. In the individual level, the pattern of isolation by geographical distance was most significant in the non-riverine population, and there was a significant correlation between functional and genetic variation in the non-riverine and upstream populations but not in the downstream. Our findings provide empirical evidence for the significant role of river corridor in propagule dispersal and genetic diversity, and highlight the potential negative effects of dams on genetic connectivity and local adaptation of riverine plants.

Spatial Structure and Genetic Variation of a Mangrove Species (Avicennia marina (Forssk.) Vierh) in the Farasan Archipelago

Avicennia marina (Forssk.) Vierh is distributed in patches along the Farasan archipelago coast and is the most common mangrove species in the Red Sea. However, to date, no studies have been directed towards understanding its genetic variation in the Farasan archipelago. In this investigation, genetic variations within and among natural populations of Avicennia marina in the Farasan archipelago were studied using 15 microsatellite markers. The study found 142 alleles on 15 loci in nine populations. The observed (Ho) and expected (He) heterozygosity values were 0.351 and 0.391, respectively, which are much lower than those of earlier studies on A. marina in the Arabian Gulf. An inbreeding effect from self-pollination might explain its heterozygote deficiency. Population genetic differentiation (FST = 0.301) was similar to other mangrove species. Our findings suggest that the sea current direction and coastal geomorphology might affect genetic dispersal of A. marina. The more isolated populations with fewer connections by sea currents exhibited lower genetic variation and differentiation between populations. The genetic clustering of populations fell into three main groups—Group 1 (populations of Farasan Alkabir Island), Group 2 (populations of Sajid Island), and Group 3 (mix of one population of Farasan Alkabir Island and a population of Zifaf Island). More genetic variation and less genetic differentiation occurred when the population was not isolated and had a direct connection with sea currents. Both of these factors contributed to limited propagule dispersal and produced significant structures among the population. It is expected that the results of this research will be useful in determining policy and species-conservation strategies and in the rehabilitation of A. marina mangrove stands on the Farasan islands in an effort to save this significant natural resource.