Migrant pool model of dispersal explains strong connectivity of Avicennia officinalis within Sundarban mangrove areas: Effect of fragmentation and replantation

Hasan, Sharmin; Triest, Ludwig; Afrose, Sania; Ryck, Dennis J. R. De

doi:10.1016/j.ecss.2018.09.007

Cited by 10 publications

(15 citation statements)

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“…Reduced flow rates may restrict dispersal and promote local establishment and regeneration, with the established trees thus leaving a trace of elevated kinship values compared to the population's average kinship value. Such traces have also been detected in other studies within spatial stretches of a few meters up to several hundreds of meters (Mori et al, 2015;Do et al, 2019;Chablé Iuit et al, 2020;Triest et al, 2020), and it has been shown that kinship can also be enhanced when populations became severely fragmented and confined within artificial dikes (Hasan et al, 2018). Sp-values for A. marina, whenever showing FSGS, are among the ranges reported for mixed mating systems in general (Vekemans and Hardy, 2004) and, more importantly, a dispersal mode suggesting local conditions of retention.…”

Section: Discussionsupporting

confidence: 73%

“…Similarly, evidence for genetic differentiation between estuarine and open-coast ecotypes of the seaweed Hormosira banksii has been found (Coleman et al, 2018). Despite the importance of identifying the influence of environmental settings on a species' dispersal characteristics and the genetic structure of populations, only recently did a few studies consider potential differences in genetic structure and diversity between mangrove populations that occupy different environmental settings (Hasan et al, 2018;Chablé Iuit et al, 2020;Triest et al, 2020), whereas several fine-scale genetic structure (FSGS) analyses delivered relevant information and revealed patterns at the within-site level (Céron-Souza et al, 2012;Mori et al, 2015;Millán-Aquilar et al, 2016;Do et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Coastal Landform Constrains Dispersal in Mangroves

Triest

Stocken

2021

Front. Mar. Sci.

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Mangrove forests are dynamic ecosystems found along low-lying coastal plains along tropical, subtropical, and some warm-temperate coasts, predominantly on tidal flats fringing deltas, estuaries, bays, and oceanic atolls. These landforms present varied hydrodynamic and geomorphological settings for mangroves to persist and could influence the extent of within-site propagule transport and subsequent local regeneration. In this study, we examined how different landform characteristics may influence local genetic diversity, kinship, and neighborhood structure of mangrove populations. To do so, we considered independent populations of Avicennia marina, one of the most abundant and widespread mangrove species, located in estuarine and coastal bay environments spread across the Western Indian Ocean region. A transect approach was considered to estimate kinship-based fine-scale spatial genetic structure using 15 polymorphic microsatellite markers in 475 adult A. marina trees from 14 populations. Elevated kinship values and significant fine-scale structure up to 30, 60, or 90 m distances were detected in sheltered systems void of river discharge, suggesting a setting suitable for very local propagule retention and establishment within a neighborhood. Slopes of a linear regression over restricted distance within 150 m were significantly declining in each sheltered transect. Contrastingly, such a spatial structure has not been detected for A. marina transects bordering rivers in the estuarine systems considered, or alongside partially sheltered creeks, suggesting that recruitment here is governed by unrelated carried-away mixed-origin propagules. South African populations showed strong inbreeding levels. In general, we have shown that A. marina populations can locally experience different modes of propagule movement, explained from their position in different coastal landforms. Thus, the resilience of mangroves through natural regeneration is achieved by different responses in coastal landforms characterized by different hydrodynamic conditions, which can be important information for their management and protection within the variety of coastal environments.

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Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Coastal Landform Constrains Dispersal in Mangroves

Triest

Stocken

2021

Front. Mar. Sci.

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“…Mangrove forest cover worldwide became fragmented or degraded due to over-exploitation for fuelwood and timber production (Valiela et al, 2001), pollution events such as oil spills (Burns et al, 1993), agricultural catchment runoff (Duke et al, 2005), extreme sedimentation (Ellison et al, 1999), and alteration of hydrological regimes (Gordon, 1988). Habitat fragmentation intrinsically encompasses population fragmentation, and potential loss of genetic diversity of the mangrove tree species (Giri et al, 2011;Wee et al, 2015;Hasan et al, 2018). Though continuous conservation efforts have been done, the recovery success of replanted mangrove trees appeared inadequate because factors such as changes in hydrodynamics, salt content, acidity and levels of nutrients may have prevented successful regeneration of mangroves (Sandilyan and Kathiresan, 2012).…”

Section: Introductionmentioning

confidence: 99%

Avicennia Genetic Diversity and Fine-Scaled Structure Influenced by Coastal Proximity of Mangrove Fragments

et al. 2021

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Avicennia dominated mangrove forests occur from seaward to landward sites and hence are subject to different dynamics within estuarine ecosystems. Regeneration of mangrove forests primarily depends on the extent of propagule spread and subsequent establishment in suitable habitats. The complex nature of estuarine systems induces a wide variety of local conditions for within-site propagule retention and settlement thereby allowing spontaneous regeneration of mangroves. In this study, we estimated the fine-scale spatial genetic structure (FSGS) of Avicennia populations and examined whether their position relative to the seaside or the size of mangrove patches could have influenced the extant local population genetic structure. A kinship-based FSGS was performed using microsatellite markers in 523 A. marina, 189 A. rumphiana and 60 A. alba adult trees of 24 sites in The Philippines. Transects within each estuary were taken both parallel and perpendicular to the coastline or tidal river edge. The extent of local mangrove areas and various human-induced encroachments as such did not show any trend in allele diversity, heterozygosity values or inbreeding levels. However, farther inland situated mangrove patches showed a larger FSGS extent across the neighborhood (up to 75 m) though less diversity along with inbreeding, most likely due to retention of related propagules and lowered chance of external propagule input. Estimation of connectivity along a same coastline stretch supported a unidirectional steppingstone or adjacent migration model for populations of either A. marina, A. alba or A. rumphiana. These were congruent with ocean currents across mangrove estuaries of the Tablas Strait and along Western Leyte, thereby emphasizing the relevance of coastal connectivity for long term persistence. From this study, we conclude that both proximity to open water and narrowness of mangrove patches may affect their captured diversity, inbreeding and fine-scale structure caused by propagule movement within or beyond a local mangrove fragment during recent generations. Higher levels of allele diversity for seaward sites and highest likelihood of migration for adjacent mangroves both add to the importance of coastal connectivity that is the only natural cohesive force on longer term and necessary to counteract short term effects of increasingly encroached mangrove environments.

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“…It is important to consider the proportional loss of mangroves, as areas with small amounts of mangrove forest will be particularly negatively affected by deforestation and resulting fragmentation, even though such small patches can still provide a disproportionate amount of ecosystem services for local populations 13 . Similarly, in addition to simply conserving mangrove forests, there is now also a focus on quantifying mangrove connectivity [14][15][16] . Although measurement of total areal loss is an important step towards informing conservation priorities, other metrics of environmental change, such as fragmentation, are also important indicators of habitat health 17-21 .…”

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Global trends in mangrove forest fragmentation

Bryan-Brown

Connolly

Richards

et al. 2020

Sci Rep

233

118

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fragmentation is a major driver of ecosystem degradation, reducing the capacity of habitats to provide many important ecosystem services. Mangrove ecosystem services, such as erosion prevention, shoreline protection and mitigation of climate change (through carbon sequestration), depend on the size and arrangement of forest patches, but we know little about broad-scale patterns of mangrove forest fragmentation. Here we conduct a multi-scale analysis using global estimates of mangrove density and regional drivers of mangrove deforestation to map relationships between habitat loss and fragmentation. Mangrove fragmentation was ubiquitous; however, there are geographic disparities between mangrove loss and fragmentation; some regions, like cambodia and the southern caribbean, had relatively little loss, but their forests have been extensively fragmented. in Southeast Asia, a global hotspot of mangrove loss, the conversion of forests to aquaculture and rice plantations were the biggest drivers of loss (>50%) and fragmentation. Surprisingly, conversion of forests to oil palm plantations, responsible for >15% of all deforestation in Southeast Asia, was only weakly correlated with mangrove fragmentation. Thus, the management of different deforestation drivers may increase or decrease fragmentation. Our findings suggest that large scale monitoring of mangrove forests should also consider fragmentation. this work highlights that regional priorities for conservation based on forest loss rates can overlook fragmentation and associated loss of ecosystem functionality.Mangroves are intertidal wetlands found along coastlines in much of the tropical, subtropical and warm-temperate world. These forests provide valuable ecosystem services including preventing erosion 1 , providing habitat for fisheries species 2 , protecting coastal communities from extreme weather events 3,4 and storing large reserves of blue carbon, thus mitigating global climate change 5 . The services provided by mangroves are threatened by anthropogenic processes including deforestation 6 and sea-level rise 7,8 . Historically, mangroves were subject to high rates of deforestation of up to 3.6% per annum 9 . However, since the turn of the millennium global mangrove deforestation rates have slowed, with annual loss rates of 0.2-0.7% 10,11 . Lower rates of loss are due to near total historical loss of forest patches in some regions, but also improved conservation practices 11 and improvements in large scale monitoring techniques that provide more accurate estimates of cover and loss than were available historically 10,12 . The majority of contemporary mangrove loss occurs in Southeast Asia, where ~50% of the remaining global mangrove forest area is located, with nations such as Indonesia, Malaysia and Myanmar continuing to show losses of 0.26, 0.41 and 0.70% per year, respectively 10 .Recently, researchers have highlighted that simply reporting mangrove total loss rates is insufficient for prioritising conservation actions 11 , if there is insufficient knowledge...

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Migrant pool model of dispersal explains strong connectivity of Avicennia officinalis within Sundarban mangrove areas: Effect of fragmentation and replantation

Cited by 10 publications

References 65 publications

Coastal Landform Constrains Dispersal in Mangroves

Coastal Landform Constrains Dispersal in Mangroves

Avicennia Genetic Diversity and Fine-Scaled Structure Influenced by Coastal Proximity of Mangrove Fragments

Global trends in mangrove forest fragmentation

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