Generic delimitation in the Antillean Adelieae (Euphorbiaceae) with description of the Hispaniolan endemic genus Garciadelia

Abstract

The Caribbean Island Biodiversity Hotspot is the largest insular system of the New World and a priority for biodiversity conservation worldwide. The tribe Adelieae (Euphorbiaceae) has over 35 species endemic to this hotspot, representing a prime example of speciation in the West Indies and involving taxa from Cuba, Hispaniola, Jamaica, and the Bahamas. These species form a monophyletic group and have traditionally been accommodated in two endemic genera, Lasiocroton and Leucocroton. A study based on scanning electron microscopy of pollen, macromorphology, and molecular analysis was conducted to reveal generic relationships within this group. Phylogenies were based on nucleotide sequences of the nrITS region and the non‐coding cpDNA spacers psbM‐trnD and ycf6‐pcbM. Three major monophyletic assemblages were revealed; one of them is restricted to Hispaniola and is accommodated in a new genus, Garciadelia, with four species. The new genus is sister to a clade comprising two monophyletic groups, one including all species of Leucocroton and restricted to serpentine soils of Cuba, and a second including the species of Lasiocroton, occurring in Cuba, Hispaniola, Jamaica, and the Bahamas. Morphological, biogeographical, and ecological data provided additional support for each of these three monophyletic assemblages. Two new combinations (Lasiocroton microphyllus from Cuba, Garciadelia leprosa from Hispaniola) are made and four new species are described (Lasiocroton gutierrezii from Cuba, and Garciadelia abbottii, G. castilloae, and G. mejiae from Hispaniola).

Islands within islands: a molecular phylogenetic study of the Leucocroton alliance (Euphorbiaceae) across the Caribbean Islands and within the serpentinite archipelago of Cuba

“…The ingroup included five of the seven known species of Lasiocroton (Jestrow et al. , 2008, 2010) (Appendix S1).…”

“…Jestrow & Jiménez Rodr. because we were unable to obtain samples of this extremely rare species, last collected in 1924 (Jestrow et al. , 2010).…”

“…, 1996, 1999). The present delimitation of Leucocroton (Jestrow et al. , 2010) includes 26 species; all are Ni‐hyperaccumulators restricted to the serpentine soil areas across Cuba.…”

“…In a prior taxonomic study, we defined the Leucocroton alliance as a clade within the tribe Adelieae (Jestrow et al. , 2008, 2010).…”

Galápagos and Cocos Islands: Geographically Close, Botanically Distant

“…For instance, the monospecific genus Ixanthus (Gentianaceae) is confined in the Canary Islands to the laurel forest, a plant community restricted to the Macaronesian Islands, but Ixanthus is sister to Blackstonia, a Mediterranean genus with four species thriving in other habitats (Thiv et al 1999). The Greater Antillean genus Leucocroton (Euphorbiaceae) has more than 28 species-all of them restricted to the serpentine soils of Cuba, an unusual habitat in the Caribbean Islands-but Leucocroton is closely related to the West Indian genus Lasiocroton, which occurs only on limestone soils (Jestrow et al 2010).…”