Population genetic diversity and structure of a dominant tropical seagrass, Cymodocea rotundata, in the Western Pacific region

Abstract

Cymodocea rotundata is an ecologically important tropical pioneer seagrass species distributed in the Indo-Pacific region. The population genetic diversity and structure of this species were analysed at 46 sites spanning the Philippines, Ryukyu Islands (northern limit) and Hainan Island, by using microsatellite simple sequence repeat (SSR) markers. Analyses revealed the persistence of C. rotundata likely relies on local population dynamics and fitness influenced by environmental gradients, with sexual reproduction prevalent in the Philippines while the Ryukyu and Hainan populations were predominantly established by clonal spread. Analysis of molecular variance showed significant genetic differentiation (P < 0.001) among three geographic regions: the Philippines, Ryukyu and Hainan. Furthermore, the mean fixation index value was very high (F ST = 0.36), indicating poor dispersal potential or limited gene flow. Allelic richness and heterozygosity of C. rotundata was comparable in the Philippines and Ryukyu Islands populations. More private alleles were found in the Philippines and excess heterozygotes in the Ryukyu Islands. STRUCTURE analysis revealed that the Ryukyu and Hainan populations were mosaics of admixed alleles of individuals from the Philippines. An assignment test suggested that recruitment occurs from the Northeast Philippines to Ryukyu Islands. These results suggest that the Philippine populations are tropical seagrass hotspots and perhaps the origin of the populations in the Ryukyu and Hainan Islands. This scenario is most likely driven by the Kuroshio Current and island integration events during plate tectonic activities. The Philippine Archipelago is considered of high importance for conservation objectives and management plan of seagrasses. Likewise, the Ryukyu Islands are also important in terms of conserving regional diversity because locally adapted genotypes have important evolutionary potential in the face of environmental change. 786Marine Ecology 37 (2016) 786-800 ª

Genetic patterns in peripheral marine populations of the fusilier fish Caesio cuning within the Kuroshio Current

“…Though not explicitly examining population dynamics across this central‐peripheral junction, a microsatellite analysis of a seastar ( Acanthaster planci ) showed no differentiation between a site in the central Philippines and the Ryukyu Islands and no decrease in genetic diversity (Yasuda et al., ). Microsatellite analyses of three species of seagrass ( Cymodocea serrulata, Cymodocea rotunda, and Enhalus acoroides ) indicate that recruitment to the Ryukyus occurs from the northeastern Philippines (Arriesgado et al, ; Nakajima et al, ). Reduced genetic diversity was only found in Ryukyu Island populations of E. acoroides and C. serrulata , however, providing further evidence that many tropical taxa may not experience measurable edge effects in peripheral populations within the Kuroshio Current.…”

“…The NEC bifurcation occurs between the latitudes of 11°-16.5°N (Qiu & Lukas, 1996) (Arriesgado et al, 2015(Arriesgado et al, , 2016Nakajima et al, 2014).…”

“…The steady, northerly stream of warm surface water flowing through the Ryukyu Islands that results in the persistence of coral reef organisms at higher‐than‐normal latitudes is provided by a powerful western‐boundary current known as the Kuroshio Current (Veron, ; Yamano, Hori, Yamauchi, Yamagawa, & Ohmura, ), but the role that western boundary currents such as the Kuroshio Current and its Atlantic Ocean counterpart, the Gulf Stream, may play in shaping the genetic patterns in the northern peripheral populations of tropical species relative to central counterparts remains mostly unexamined. The only taxon sampled across the flow path of the Kuroshio Current to address questions about genetic connectivity and diversity in central and peripheral populations is passive propagule‐dispersing seagrass (Arriesgado et al, ; Kurokochi et al, ; Nakajima et al, ) leaving a majority of the tropical species and ecosystems whose peripheral populations are found in the Ryukyu Islands unstudied.…”

Shared genomic outliers across two divergent population clusters of a highly threatened seagrass

“…Previous studies have shown that the genetic diversity, clonality and connectivity of seagrasses globally is highly context dependent (Jover et al 2003;Olsen et al 2004;Procaccini et al 2007;Sinclair et al 2014;Arriesgado et al 2016;Kendrick et al 2016;Hernawan et al 2017;Putra et al 2018), with some studies reporting high genetic diversity and population structuring at regional and local scales (Diekmann et al 2005;van Dijk & van Tussenbroek 2010;Becheler et al 2010;Sherman et al 2016), emphasizing the role of near and off-shore currents (Muñiz-Salazar et al 2005;Nakajima et al 2014). Conversely, in a few cases, low levels of genetic diversity and shared genotypes, even across exceptionally large spatial scales, have been recorded (van Dijk & van Tussenbroek 2010;Evans et al 2014;Nakajima et al 2014;Phan et al 2017).…”

Local-Level Genetic Diversity and Structure of Matsutake Mushroom (Tricholoma matsutake) Populations in Nagano Prefecture, Japan, Revealed by 15 Microsatellite Markers

“…Microsatellite (SSR: simple sequence repeat) markers for polymorphism analysis are known to be effective for analyzing the reproductive mechanisms of many organisms. Nuclear SSR markers with high polymorphism might also contribute to the analysis of parenthood, kinship, genetic structure, and population genetics [ 8 , 9 , 10 , 11 , 12 , 13 ]. Nagano prefecture is one of the most productive areas for matsutake mushroom growth and has recently had the highest annual yield of this product in Japan (Forestry Agency, Ministry of Agriculture, Forestry and Fisheries: Japan Annual report on trends in forest and forestry in Japan, Fiscal year 2009 (Summary)).…”