Evolutionary history of the seagrass genus Posidonia

Abstract

Seagrasses are the structural species of one of the most important coastal ecosystems worldwide and support high levels of biodiversity and biomass production. Posidonia is one of the most ancient seagrass genera and displays a contrasting disjunct biogeographic pattern. It contains one single species in the Northern Hemisphere, P. oceanica, which is endemic to the Mediterranean Sea, and has up to 8 recognized taxa in the Southern Hemisphere, which in Australia are divided into 2 complexes, P. ostenfeldii and P. australis. A phylogeny based on a nuclear marker (rRNA-ITS) revealed an ancient split between the northern (i.e. Mediterranean) and southern (i.e. Australian) taxa, followed by a separation of the 2 recognized Australian complexes. However, the species belonging to the P. ostenfeldii complex were indistinguishable, suggesting an ecotypic origin or a recent speciation. Therefore, among the 7 morphologically described Australian species only 4 species lineages can be discriminated. The organelle markers nad 7 intron, trnL-F and mat K/trnK intron were not informative for reconstructing the phylogeny of this genus, and the mitochondrial markers exhibited a strikingly slow evolutionary rate relative to other genome regions.KEY WORDS: Posidonia · Phylogeny · Low evolutionary rates · Ancient diversification Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 421: [117][118][119][120][121][122][123][124][125][126][127][128][129][130] 2011 (Den Hartog 1970). Fossils of Posidonia found in Europe and recorded from the Cretaceous to the Miocene have remained apparently almost unchanged over this long evolutionary history (Den Hartog 1970).Based on ecological, vegetative, reproductive and morphological characteristics, 9 species were initially described with a unique fragmented distribution. Posidonia oceanica is endemic to the Mediterranean Sea, whereas the other 8 described species (P. australis, P. sinuosa and P. angustifolia from the P. australis complex and P. coriacea, P. denhartogii, P. kirkmanii, P. ostenfeldii and P. robertsoniae from the P. ostenfeldii complex) are restricted to subtropical and temperate Australian waters (Cambridge & Kuo 1979, Kuo & Cambridge 1984 and are separated by about 17 000 km from their Mediterranean congeneric species. More recently, morphological information combined with allozymes revealed that P. coriacea and P. robertsoniae within the P. ostenfeldii complex are synonyms (Campey et al. 2000) resulting in 7 recognized species in the Australian complexes. Despite the relatively small number of Posidonia species, 3 groups are recognized based on the presence or absence of a primary root in the Australian and Mediterranean species respectively, on the width of their leaf (thicker but stiffer in the P. ostenfeldii complex) and on rhizome features (horizontal/vertical growth) as well as ecological characteristics associated with the 2 Australian groups (P. australis and P. ostenfeldii complexes) (Gobert et al. 2006).Australian...

Unravelling complexity in seagrass systems for management: Australia as a microcosm

“…Extreme variation in environmental conditions in this bioregion has led to significant morphological variation in the Posidonia species, though their taxonomic distinctness has been questioned (e.g. Aires et al, 2011;Campey et al, 2000). Four species are found in all bioregions: Halophila ovalis and Zostera muelleri are Table 1 Ecosystem services which are provided by transitory seagrass meadows.…”

Phylogenetic relationships of Mediterranean and North-East Atlantic Cantharidinae and notes on Stomatellinae (Vetigastropoda: Trochidae)

“…According to our results, the origin of the Mediterranean and NE Atlantic lineage occurred in the boundary between the Early and Middle Eocene around 47 MYA (about interestingly, the marine angiosperm genus Posidonia shows a similar geographic distribution with antipode (Australian and Mediterranean) clades. The divergence between these Posidonia clades is ancient, and was estimated based on ITS (internal transcribed spacer) sequence data to have occurred about 68 Myr (Aires et al, 2011), coinciding with the Cretaceous-Tertiary mass extinction (K-T boundary) event (Schulte et al, 2010). Other authors (Phillips and Meñez, 1988) (Harzhauser et al, 2009).…”

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…An exception is bull kelp that is classified as a fucoid. Taxonomic understanding of both groups remains incomplete and in need of further refinement (reviews Hartog and den Kuo, 2006;Bartsch et al, 2008;Bolton, 2010), despite recent advances (Lane et al, 2006;Aires et al, 2011;Coyer et al, 2013;Rothman et al, 2015Rothman et al, , 2017Jackson et al, 2017). The continued application of genome-wide markers and multigene phylogenies will likely reveal previously overlooked taxonomic and biogeographic lineages (e.g., Tellier et al, 2009Tellier et al, , 2011.…”