Phylogenomics, anatomy, and taxonomy of the genus Diplostephium (Asteraceae)

Diplostephium ericoides at Cotopaxi, Ecuador

Diplostephium ericoides at Cotopaxi, Ecuador

High elevation Andean ecosystems in South America are reservoirs of biodiversity. As a result of their elevation gradient and complex topography these ecosystems present a high number of endemics. Because of the high altitude, páramos can be considered “islands” in a sea of lower elevation forest. An “island” biogeographic speciation scenario combined with the recent origin of the páramos and the effects of Pleistocene glaciations are believed to be responsible for ca. 4700 species of plants living in the páramo, of which 60 percent is believed to be endemic (Luteyn 1999).

The genus Diplostephium includes 111 species distributed from Costa Rica to northern Chile in high elevation cloud forest, páramo, and puna habitats. The morphological variation and the high number of species make the genus an excellent candidate to study the evolutionary processes that affected speciation along the Andes and shaped the fauna and flora seen today.

New species of Diplostephium in the process of being described

New species of Diplostephium in the process of being described

The genus was largely studied by the Spanish botanist Jose Cuatrecasas, who described more than 90 new taxa in the genus along with two revisions (1943, 1969). While the first revision accounted for 64 species, the second one focused on the Colombian territory, accounting for 53 species. Jose Cuatrecasas, who lived and collected in Colombia focused his works on the Colombian taxa, which is the reason why the Diplostephium species outside Colombia have not been treated since 1948. In the absence of a complete treatment for the genus, Vargas (2011) published a nomenclator of the genus compiling all the names published and deciphering the circumscription of the names from the literature and herbarium specimens. On the grand scale the non-Colombian species have yet to be studied.

 

Cross section of Diplosptehium colombianum stem, arrow indicates a vessel.

Cross section of Diplosptehium colombianum stem, arrow indicates a vessel.

The phylogeny of the genus is poorly known. Previous studies (Vargas and Madriñan 2012) shown that Diplostephium radiated rapidly to the paramos. Due to the use of just one molecular marker (ITS), the phylogeny by Vargas and Madriñan (2012) is poorly supported. Therefore, authors concluded that more markers are necessary to fully elucidate Diplostephium phylogeny and test its monophyly. Currently I am using genome skimming to infer a robust phylogeny of Diplostephium, assess its monophylyand test multiple hypothesis about its diversification.

The main objectives of my project are: 1) Build a robust phylogeny of Diplostephium and test if Diplostephium is monophyletic using genome-skimming sequencing and phylogenetic methods. 2)  Test different hypotheses about the evolution of Diplostephium on the paramos along with the calculation paramo clade/s age and diversification rate(s) ; 3) Study the anatomical characteristics that associated with inhabiting the paramo.