Phylogenetics of Darwiniothamnus (Asteraceae: Astereae) – molecular evidence for multiple origins in the endemic flora of the Galápagos Islands

Abstract

Aim The aims of this study were (1) to investigate whether the two growth forms of Darwiniothamnus Harling (Asteraceae) originated from the colonization of a single ancestor, (2) to identify the closest relative(s) of Darwiniothamnus, and (3) to review molecular phylogenies from other plant groups to infer the origin of Galápagos endemics.Location Darwiniothamnus is endemic to the Galápagos Islands.Methods All putative relatives of Darwiniothamnus plus 38 additional species were included. Nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA were used for Bayesian and parsimony analyses.Results Darwiniothamnus is polyphyletic. Two species (D. lancifolius (Hook. f.) Harling and D. tenuifolius (Hook. f.) Harling) are woody shrubs that usually grow to 1-2 m in height; they belong to a clade composed of species otherwise restricted to the Caribbean. These two species are sister to Erigeron bellidiastroides Griseb., a herbaceous species endemic to Cuba. The third species (D. alternifolius Lawesson & Adsersen) is a perennial herbaceous plant, woody at the base and reaching only up to 50 cm in height. It is sister to two Chilean (CoquimboValparaiso region) species that also have a perennial herbaceous habit: E. fasciculatus Colla and E. luxurians (Skottsb.) Solbrig. They are placed in an assemblage restricted to South America. The review of previous molecular phylogenetic studies revealed that two of the endemic genera and endemic species of three non-endemic genera have their closest relatives in South America. Endemic species belonging to three non-endemic genera have sister species in North America or the West Indies. One endemic genus and endemic species in three non-endemic genera have sister taxa with a widespread continental distribution, or their molecular phylogenies yielded equivocal results.Main conclusions The flora of Galápagos has affinities with both North America (including the Antilles) and South America. Darwiniothamnus exhibits both patterns: two species of this genus are sister to a taxon endemic to Cuba, supporting a connection between the Cocos plate and the West Indies; the third species, D. alternifolius, provides a link with the Coquimbo-Valparaiso region, suggesting a biogeographical connection between the Nazca plate and southern South America.

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

“…Some of these links involve the eastern Pacific, as demonstrated recently for Darwiniothamnus Harling (Asteraceae), a Galapagos genus sister to Erigeron bellidiatroides Griseb. from western Cuba (Andrus et al 2009). However, other examples involve remote areas of the Pacific as shown by Narvalina Cass.…”

“…The latter is a coastal strand species occurring on tropical Africa (including Madagascar and Mascarene Islands), the Caribbean Basin, Baja California, the Galapagos Islands, Ecuador, Atlantic South America, Sri Lanka, and SW India. Andrus et al (2009) argue that long distance dispersal between the Caribbean and the Pacific Basin has been facilitated by relatively recent historical events. The tropical sea way connected the Caribbean Sea and the Pacific Ocean until the late Pliocene (ca.…”

Conservation of oceanic island floras: Present and future global challenges

“…For instance, pollen records show that the legume shrub Kanaloa kahoolawensis was a dominant species of lowland habitats in Hawaii before ca. 1550 A.D., but it was unknown to science until its discovery in 1992 (Lorence and Wood, 1994).The inception of DNA sequencing has enabled a wealth of studies on the origins and post-colonisation history of island plant groups (e. Andrus et al, 2009;Jaé n-Molina et al, 2009). DNA sequences are useful in detecting phylogenetic patterns important in biodiversity conservation planning, e.g.…”

“…Molecular population genetic or phylogenetic investigations are contributing to more refined insights into the population biology and systematics of endemics in several archipelagos (e.g. Crawford et al, 1987;Baldwin et al, 1991;Francisco-Ortega et al, 1996;Carine et al, 2004;Nuez et al, 2004;Ruiz et al, 2004;Moore et al, 2006;Archibald et al, 2006;Oliva-Tejera et al, 2006;Díaz-Pé rez et al, 2008;Maunder et al, 2008;Andrus et al, 2009;Gonzá lez-Pé rez et al, 2009). Currently, a sample of the endemic flora of Garajonay National Park (La Gomera, Canaries) is being used to test the potential usefulness of cpDNA sequences in complementing morphological variables for the identification of the whole Canarian Flora (Caujapé -Castells et al, 2007a, b).…”

Phylogenetics, Conservation, and Historical Biogeography of the West Indian Members of the Adelieae (Euphorbiaceae)

“…Most molecular phylogenetic studies concerning plant adaptive radiation of insular systems focus on remote volcanic oceanic islands such as the Galápagos, the Hawaiian Archipelago, Juan Fernández, Macaronesia, and St. Helena (Andrus et al, 2009;Eastwood et al 2004;Francisco-Ortega et al, 1996;Price & Wagner, 2004;Ruiz et al, 2004;Trusty et al, 2005;).…”