Uniformity of the nuclear and chloroplast genomes of Spartina maritima (Poaceae), a salt-marsh species in decline along the Western European Coast

Abstract

Spartina maritima is a salt-marsh species from European and African Atlantic coasts. In the northern range of the species (including north-west France), a rapid decline of the populations has been observed during the 20th century. In this paper, the molecular diversity of 10 populations of S. maritima from France has been investigated using nuclear and chloroplast DNA markers: inter-simple sequence polymorphism (ISSR), randomly amplified polymorphic DNA (RAPD), inter-retrotransposon amplified polymorphism (IRAP), and PCR-RFLP of a 5 kb long portion of chloroplast DNA. The results reveal an extremely low level of genetic variation in this species: only one nuclear marker (out of 98) was polymorphic, with the presence of two genotypes randomly distributed among the populations. The lack of genetic diversity is interpreted in light of the almost exclusive vegetative propagation of the species in its northern range, the colonization history of the populations, and the origin of S. maritima (2n ¼ 60) in the hexaploid lineage of the genus and in the context of the management of S. maritima populations.

Hybridization, polyploidy and invasion: lessons from Spartina (Poaceae)

“…All the individuals examined in the populations of S. anglica from England (Ferris et al 1997) and France (Baumel et al 2001(Baumel et al , 2003 exhibited the same chloroplast sequences as the F1 hybrids S. 9 townsendii and S. 9 neyrautii and as S. alterniflora, which was therefore deduced to be the maternal genome donor in both hybridization events (England and France). The presence of only one chlorotype (from S. alterniflora) together with the lack of interindividual variation in S. anglica reinforce the ''unique origin'' hypothesis of the allopolyploid; as the parental species S. maritima and S. alterniflora lack variation in the region where they hybridized (Raybould et al 1991b;Baumel et al 2003;Yannic et al 2004), any recurrent hybridization event would have involved very similar parental genotype. In any case, S. anglica seems to have experienced a strong genetic bottleneck at the time of its formation in southern England (Ainouche et al 2004a), which contrasts with the multiple origins reported in several recent allopolyploids (e.g.…”

Retro-transposon based genetic similarity within the genus Citrus and its relatives

“…Several retrotransposon-based marker systems have been developed that reveal insertion polymorphisms generated by the transposition of the retrotransposons. Inter-retrotransposon amplified polymorphism (IRAP) and Retro-element-microsatellite amplified polymorphism (REMAP) retrotransposon based marker methods successfully applied in fingerprinting (Breto et al 2001;Bernet et al 2004), linkage analysis and mapping of agronomic traits (Manninan et al 2000), analysis of genome evaluation and genetic diversity (Yannic et al 2004). Several reports has been published about retrotransposon based DNA fingerprint in many plant species such as Oryza (Castelo et al 2007), Triticum (Queen et al 2004), Musa (Ashalatha et al 2005), Diospyros (Dalong et al 2006), Malus (Kristiina et al 2006).…”

Transcriptome de novo assembly from next-generation sequencing and comparative analyses in the hexaploid salt marsh species Spartina maritima and Spartina alterniflora (Poaceae)

“…Within homoelogues (at strictly orthologous loci), levels of heterozygosity have been poorly investigated in S. maritima, although this species is well known for its predominant clonal propagation and weak interindividual genetic variation (Yannic et al, 2004). Spartina alterniflora has a mixed, predominantly outcrossing mating system (Travis et al, 2004); thus, more allelic variation within homoeologues might be expected than for S. maritima.…”

“…The recession of S. maritima in its northern range limit (southern England and Brittany) is interpreted as a consequence of climatic changes and anthropogenic habitat disturbance (Raybould et al, 1991), but may also be related to the biological and morphological differences between these two species. Spartina alterniflora exhibits strong rhizomes facilitating lateral expansion and sediment accretion, and thus has an important role in the salt marsh dynamics where it is considered as an ecosystem engineer, whereas S. maritima is a non-rhizomatous, genetically depauperate species (Yannic et al, 2004) with very low seed production (Marchant and Goodman, 1969;Castellanos et al, 1994;Castillo et al, 2008). Spartina maritima and S. alterniflora also exhibit chromosome number differences, as the former has a regular hexaploid number (2n ¼ 6x ¼ 60) whereas the latter presents aneuploidy (2n ¼ 62), and genome size differences (2C ¼ 3.8 pg for S. maritima and 2C ¼ 4.3 pg for S. alterniflora, Fortune et al, 2008).…”