Plastid DNA Homogeneity inCeltis australisL. (Cannabaceae) andNerium oleanderL. (Apocynaceae) throughout the Mediterranean Basin

Abstract

Editor: Alan W. Meerow Premise of research. Riparian plants are highly dependent on water sources; consequently, general climatic conditions are less important to these taxa relative to woodland and shrubland species. This leads to interesting research questions regarding riparian plant taxa. Research on phylogeography of Mediterranean riparian tree and shrub species is scarce. In this article, we investigated the plastidial genetic diversity in Celtis australis L. (hackberry) and Nerium oleander L. (oleander) throughout the Mediterranean Basin. Both species are distributed in gullies, rivers, and stream banks under warm temperate climates.Methodology. Eighteen cpSSR loci and three noncoding cpDNA regions (rps16, rpl32-trnL, and trnQ-5′-rps16) were examined to assess the levels and geographic distribution of sequence variation in 41 hackberry and 56 oleander populations. The rpl32-trnL intergenic region was used for molecular dating analysis.Pivotal results. The respective 2762-and 3134-bp noncoding cpDNA regions sequenced in C. australis and N. oleander, as well as the 22 cpSSR analyzed fragments, exhibited the absence of variability in natural populations throughout the Mediterranean Basin. In N. oleander, two regions (rps16, rpl32-trnL) exhibited variability in three positions, and four cpSSR microsatellite motifs were polymorphic. The polymorphisms were geographically structured, and three haplotypes were characterized, two from Saharan populations and one from Mediterranean populations. Phylogeny and molecular dating analyses resulted in a tree with high consistency values of posteriori probability (PP p 1) and bootstrap support (98%) from the ingroup (N. oleander). The relaxed molecular clock model applied to the calibration of the tree estimates that the diversification of these haplotypes occurred in a range of 7.2-1.2 Ma.Conclusions. The absence of plastid variability in both hackberry and oleander is explained by a low mutation rate and/or recent recolonization of the Mediterranean Basin. Low temperatures during the Last Glacial Maximum produced freezing water along riparian corridors, with the consequent drastic contraction or even disappearance of both species in the Mediterranean Basin.

A strong east–west Mediterranean divergence supports a new phylogeographic history of the carob tree (Ceratonia siliqua, Leguminosae) and multiple domestications from native populations

“…These results contrast with the higher plastid diversity observed in other Mediterranean trees like Erica arborea L., O . europaea or Myrtus communis L. (Besnard, Terral, & Cornille, ; Désamoré et al, ; Migliore et al, ); but are congruent with the low plastid variation observed in Laurus nobilis L. (Rodriguez‐Sanchez, Guzmán, Valido, Vargas, & Arroyo, ) and even higher than in Celtis occidentalis L. and Nerium oleander L. (Mateu‐Andres et al, ). Nuclear and plastid markers therefore indicate low levels of allelic richness for the carob tree which are consistent with a strong decline scenario.…”

Phylogeographic sampling guided by species distribution modeling reveals the Quaternary history of the Mediterranean–Canarian Cistus monspeliensis (Cistaceae)

“…Fernández‐Mazuecos & Vargas (2011) postulated that Quaternary climate changes in the Mediterranean Basin caused a massive extinction of mainland populations. This extinction may have resulted in a dramatic genetic bottleneck, followed by recent expansion from some refugia, a pattern also described in other Mediterranean plants (Vendramin et al, 2008; Mateu‐Andrés et al, 2015). Nevertheless, the location of mainland refugia remains unknown for C. monspeliensis .…”

Phylogeography at the crossroad: Pleistocene range expansion throughout the Mediterranean and back‐colonization from the Canary Islands in the legume Bituminaria bituminosa

“…Traits refer to the following character states: SH = shrub versus PH = tree/woody climber; FD = deciduous, semi‐deciduous or facultative deciduous versus EV = evergreen sclerophylls; LL = large‐leaved (typically >5 cm long or >5 cm 2 in size) versus SL = small leaved. (a) Bello (2015), (b) Viruel et al (2020), (c) Coello et al (2020), (d) Fernández‐Mazuecos and Vargas (2010), (e) Désamoré et al (2011), (f) Rodríguez‐Sánchez et al (2009), (g) Kondraskov et al (2015), (h) Migliore et al (2012), (i) Besnard et al (2013), (j) García‐Verdugo et al (unpublished data), (k) Mateu‐Andrés et al (2015); (l) García‐Verdugo et al (2015, 2020), (m) Vendramin et al (2008), (n) Saladin et al (2017), (o) Vitelli et al (2017), (p) Mateu‐Andrés et al (2013), (q) Chen et al (2014) and (r) Grassi et al (2006).…”