Ocean Currents Drove Genetic Structure of Seven Dominant Mangrove Species Along the Coastlines of Southern China

Abstract

Mangrove forest ecosystems, which provide important ecological services for marine environments and human activities, are being destroyed worldwide at an alarming rate. The objective of our study was to use molecular data and analytical techniques to separate the effects of historical and contemporary processes on the distribution of mangroves and patterns of population genetic differentiation. Seven mangrove species (Acanthus ilicifolius, Aegiceras corniculatum, Avicennia marina, Bruguiera gymnorrhiza, Kandelia obovata, Lumnitzera racemosa, and Rhizophora stylosa), which are predominant along the coastlines of South China, were genotyped at nuclear (nSSR) and chloroplast (cpSSR) microsatellite markers. We estimated historical and contemporary gene flow, the genetic diversity and population structure of seven mangrove species in China. All of these seven species exhibited few haplotypes, low levels of genetic diversity (HE = 0.160–0.361, with the exception of K. obovata) and high levels of inbreeding (FIS = 0.104–0.637), which may be due to their marginal geographical distribution, human-driven and natural stressors on habitat loss and fragmentation. The distribution patterns of haplotypes and population genetic structures of seven mangrove species in China suggest historical connectivity between populations over a large geographic area. In contrast, significant genetic differentiation [FST = 0.165–0.629 (nSSR); GST = 0.173–0.923 (cpSSR)] indicates that populations of mangroves are isolated from one another with low levels of contemporary gene flow among populations. Our results suggest that populations of mangroves were historically more widely inter-connected and have recently been isolated, likely through a combination of ocean currents and human activities. In addition, genetic admixture in Beibu Gulf populations and populations surrounding Hainan Island and southern mainland China were attributed to asymmetric gene flow along prevailing oceanic currents in China in historical times. Even ocean currents promote genetic exchanges among mangrove populations, which are still unable to offset the effects of natural and anthropogenic fragmentation. The recent isolation and lack of gene flow among populations of mangroves may affect their long-term survival along the coastlines of South China. Our study enhances the understanding of oceanic currents contributing to population connectivity, and the effects of anthropogenic and natural habitat fragmentation on mangroves, thereby informing future conservation efforts and seascape genetics toward mangroves.

Land Use Scenario Simulation and Ecosystem Service Management for Different Regional Development Models of the Beibu Gulf Area, China

“…However, the mud flat area in the ecotourism development scenario was the largest and was mainly gathered in the coastal areas. The main reason for this was that mangroves not only provide important natural resources for tourism, but also provided important ecosystem services for the marine environment and industries including fisheries, timber, and plant products, which was one of the priority land use types for conservation in this scenario [29].…”

“…For example, mud flat in the Beibu Gulf area is being destroyed at an alarming rate. This loss has led to some serious ecological problems such as sea level fluctuations and biodiversity degradation, which will have a huge impact on the coastal areas [29]. Therefore, understanding the changing pattern of ecosystem structure and function in the Beibu Gulf area and its driving factors, as well as assessing its ecotourism potential and possible impacts, have become one of the key scientific issues in this region's development.…”

Physiological and Biochemical Responses of Kandelia obovata to Upwelling Stress

“…Plenty of studies have investigated mangrove extinction due to anthropogenic activities such as aquaculture and urban development [12,13] and environmental changes such as extreme weather events, sea level rise affected by climate change, and plastic and microplastic pollution [14][15][16][17]. This loss causes a serious ecological problem and mangroves need urgent conservation to deal with further increases in climate change, which is expected to have a dramatic effect on coastal areas [18,19].…”

Evaluating the physiological and biochemical responses of different mangrove species to upwelling

“…Avicennia marina, Aegiceras corniculatum and Kandelia obovata are dominant mangrove species in South China, and it has been reported that these three species show different resistances to low temperature (Lin, 1997;Geng et al, 2021). The leaves of Avicennia marina suffered more serious damages than Aegiceras corniculatum and Kandelia obovata under 2008 chilling event in southern China (Chen et al, 2017).…”