Understanding Mediterranean‐Californian disjunctions: molecular evidence from Chenopodiaceae‐Betoideae

Abstract

Chenopodiaceae subfam. Betoideae is distributed in both western Eurasia (four genera) and western North America (one genus). To understand the origin of this disjunction, the phylogeny of the subfamily was reconstructed and dated using ndhF, matK/trnK, trnL‐trnF spacer, and ITS sequence variation, penalized likelihood and Langley‐Fitch, and calibration with three different fossils. Maximum Parsimony and Maximum Likelihood analyses of the molecular data show that Betoideae are monophyletic, but that relationships of the Himalayan Acroglochin, traditionally included in Betoideae because of the shared possession of a circumscissile capsule, are uncertain. Among the betoidean genera, Beta (excl. sect. Procumbentes) is sister to a clade of Hablitzia, Patellifolia (= Beta sect. Procumbentes), Oreobliton, and Aphanisma. Apart from the strongly supported sister group relationship between the North African Oreobliton and the Californian Aphanisma interrelationships among these four genera are not unambiguously resolved. The crown group age of Betoideae was estimated to 38.4–27.5 my using different DNA sequences, and the age of the Oreobliton/Aphanisma split to 15.4–8.1 my. Considering all evidence available, we conclude that the western Eurasian‐western North American disjunction of Oreobliton/Aphanisma is more likely to have resulted from the fragmentation of a Beringian than a North Atlantic ancestral range. Irrespective of the geographical location of this ancestral range we postulate that the evolution into dry habitats of Oreobliton and Aphanisma took place in parallel in western Eurasia and western North America. Evidence for this may be the very different life form and habitat of the two genera, of which Oreobliton is a subshrub of rocky ground at montane altitude, and Aphanisma an annual from coastal habitats. Hablitzia, a perennial vine of deciduous forests in the Caucasus area, is sister to Patellifolia/Oreobliton/Aphanisma in the ndhF and ITS data sets. The habitat requirements of Hablitzia may be similar to those of the ancestor of the subfamily. Comparing the age of the Oreobliton/Aphanisma disjunction with ages estimated for East Asian‐eastern North American disjunctions, we conclude that in many cases these two types of disjunction represent different ecological trajectories of essentially the same historical phenomenon.

Old-New World and trans-African disjunctions of Thamnosma (Rutaceae): Intercontinental long-distance dispersal and local differentiation in the succulent biome

“…The estimated age of the split between the American and the African taxa in the Miocene (12.63, Ma, node F in Table 3 ) falls outside the time frames of both Axelrod ' s (1975) Madrean-Tethyan (37.2 -23 Ma) and Tiffney ' s (1985b) Eocene North Atlantic land bridge (55.8 -33.9 Ma) hypotheses. This is inconsistent with vicariance across the North Atlantic, and these results are congruent with those of Lavin et al (2004) for legumes and Hohmann et al (2006) for the Californian -Mediterranean Aphanisma -Oreobliton (Amaranthaceae) disjunction. Moreover, the Madrean-Tethyan hypothesis referred to the Mediterranean area rather than the succulent biome in the strict sense of Schrire et al (2005a) .…”

“…Moreover, the Madrean-Tethyan hypothesis referred to the Mediterranean area rather than the succulent biome in the strict sense of Schrire et al (2005a) . Our age estimates cannot reject vicariance across an early Miocene (23 -16 Ma) migration route via the Bering land bridge ( Stebbins and Day, 1967 ;Tiffney, 1985a ;Hohmann et al, 2006 ). The much larger distance between North America and Africa via Beringia and the absence of Thamnosma in Asia argue against it (cf.…”

Phylogenetic analyses of nucleotide sequences confirm a unique plant intercontinental disjunction between tropical Africa, the Caribbean, and the Hawaiian Islands

“…Such species provide some of the best insights on how global environmental changes or long-distance dispersal events have shaped plant biodiversity on our planet (Lavin and Luckow 1993;Sanmartín and Ronquist 2004;Galley and Linder 2006;Milne 2006;Donoghue 2008). Molecular systematic tools have been useful in understanding the evolutionary history of these taxa (e.g., Wen 1999;Hohmann et al 2006;Barker et al 2007;Dick and Heuertz 2008). In addition, DNA phylogenies have identified clades with intercontinental discontinuities that traditionally were not considered as examples of these unique biogeographical distributions [e.g., the CryptotaeniaPimpinella clade (Apiaceae) between East-Central Africa and Eurasia; Spalik and Downie (2007)].…”

Biodiversity Assessment of Sugar Beet Species and Its Wild Relatives: Linking Ecological Data with New Genetic Approaches

“…15,16]. In the present paper, we will use the taxonomic system as described by Hohmann et al [17], which was based on molecular studies indicating that the section Procumbentes should be separated from the genus Beta. Table 1 gives the distribution of Beta and Patellifolia species, which occur in the West Mediterranean Region, including the Macaronesian Re- …”