A common origin for woody Sonchus and five related genera in the Macaronesian islands: molecular evidence for extensive radiation.

Abstract

Woody Sonchus and five related genera (Babcockia, Taeckholmia, Sventenia, Lactucosonchus, and Prenanthes) of the Macaronesian islands have been regarded as an outstanding example of adaptive radiation in angiosperms. Internal transcribed spacer region of the nuclear rDNA (ITS) sequences were used to demonstrate that, despite the extensive morphological and ecological diversity of the plants, the entire alliance in insular Macaronesia has a common origin. The sequence data place Lactucosonchus as sister group to the remainder of the alliance and also indicate that four related genera are in turn sister groups to subg. Dendrosonchus and Taeckholmia. This implies that the woody members of Sonchus were derived from an ancestor similar to allied genera now present on the Canary Islands. It is also evident that the alliance probably occurred in the Canary Islands during the late Miocene or early Pliocene. A rapid radiation of major lineages in the alliance is consistent with an unresolved polytomy near the base and low ITS sequence divergence. Increase of woodiness is concordant with other insular endemics and refutes the relictural nature of woody Sonchus in the Macaronesian islands.

Δ6-Desaturase sequence evidence for explosive Pliocene radiations within the adaptive radiation of Macaronesian Echium (Boraginaceae)

“…Trait utility of plant habit in Macaronesia is additionally manifested by further shifts. Reversal to an herbaceous condition had not, however, been documented in Macaronesian plant groups after acquisition of bush-like forms once (Sonchus, Isoplexis, Aeonium group) or multiple times (Pericallis) (Kim et al, 1996;Panero et al, 1999;Mort et al, 2002;Bräuchler et al, 2004). We herein confirm reversal to an herbaceous condition in woody lineages of Echium (Böhle et al, 1996) and report for the first time three independent formations of annual species (E. bonnetii, E. pitardii, E. triste) in dry habitats of Macaronesia (Fig.…”

“…The Sonchus alliance (Kim et al, 1996), the Aeonium alliance (Mort et al, 2002), Argyranthemum , and the Echium group (Böhle et al, 1996), with over 25 species each, provide opportunities to investigate multiple patterns of evolution. They are ideal plant groups to test hypotheses of adaptive radiation and the adaptive significance ('utility') of some typical characters developed on islands such as the acquisition of woodiness.…”

“…Many phylogenetic studies, however, reveal that remarkable shifts from herbaceous to bush and tree-like species across different plant groups (taxonomic families) is the predominant pattern (see revisions in Carine et al, 2004;Vargas, 2007). Among the 1062 genera of Macaronesian vascular plants, secondary acquisition of woodiness has been documented by means of molecular phylogenetics in Sonchus (Kim et al, 1996), Pericallis (Panero et al, 1999), the Aeonium alliance (Mort et al, 2002), Sideritis (Barber et al, 2002), Tolpis (Moore et al, 2002), and Convolvulus (Carine et al, 2004). Remarkably, significant morphological diversity (as exemplified by growth habits), is found in 28 Macaronesian Echium species (Böhle et al, 1996), surpassing that of the remaining 40 continental relatives.…”

Flowering-time genes modulate meristem determinacy and growth form in Arabidopsis thaliana

“…Conversely, evolution from annual herbaceous ancestors to perennial woody taxa has also repeatedly occurred 1 . For example, in various annual herbaceous lineages, such as Sonchus and Echium, woody perennial species evolved on isolated islands from their continental annual ancestors [26][27][28] . Here we have shown the strong impact of only three genes (FT, SOC1 and FUL) on plant growth form and longevity in Arabidopsis.…”

Candidate Genes, Quantitative Trait Loci, and Functional Trait Evolution in Plants

“…Some of the richest examples of evolution in morphological and ecophysiological traits with recognized adaptive function (Robichaux et al 1990;Kim et al 1996) are in wild nonmodel plant lineages, which will need to be studied directly if the genetic basis for their trait differences is to be understood. Fortunately, the wealth of genetic resources and data generated from model plants should greatly facilitate evolutionary studies in other plant lineages.…”