Phylogenetic Relationships in Trichilia (Meliaceae) Based on Ribosomal Its Sequences

Abstract

The internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) was used to investigate phylogenetic relationships in Trichilia (Meliaceae). Analyses focused on the neotropical Trichilia and consisted of 112 accessions (95 neotropical Trichilia, 6 African Trichilia and 11 Meliaceae Outgroups). Bayesian and Parsimony approaches demonstrated that the Cuban species T. havenensis is the earliest diverging lineage in the genus. The African species of Trichilia are nested within the neotropical clade. Section Moschoxylun (primarily Amazonian rainforest species) shows significantly lower levels of sequence divergence than section Trichilia (primarily dry/ seasonally dry forest species). Recently diverged rainforest taxa have been documented in several other Angiosperm families and our results therefore confirm this phenomenon.

Biogeography and ecology in a pantropical family, the Meliaceae

“…It is sometimes suggested that the evolutionary history of Meliaceae has been one of radiation. Koenen et al (2015) concluded that the family as a whole evolved by "recent radiations", while Pennington & Clarkson (2013) proposed recent radiation in Guarea, Clarkson et al (2016) proposed "recent rapid radiation" in Trichilia, and Grudinski et al (2014a) discussed the "major radiation" in Aglaia Lour.…”

“…Notes. An initial molecular phylogeny indicated that Trichilia sensu lato comprises three main clades (Clarkson et al, 2016): with a phylogeny Trichilia havanensis of America (35 American Trichilia species (6 African Trichilia species, Pseudobersama + Pterorrhachis, both from Africa, and T. trifolia of America)).…”

“…The phylogeny is: New World (New World (New World and Old World)), and so Clarkson et al (2016) wrote that: "The African species of Trichilia are nested within the neotropical clade". However, strictly speaking, they are nested in an African + Neotropical clade.…”

“…In their study of Trichilia phylogeny, Clarkson et al (2016) wrote that: "within the monophyletic crown group (sect. Moschoxylum) the majority of the species are on short branches with low sequence divergence between species, suggesting recent speciation… The causes of these recent rapid radiations within this seemingly stable and unchanging tropical environment are not immediately straightforward to understand".…”

“…Trichilia reticulata and T. trachyantha have normal, non-spiny leaves, but the five other species all have distinctive, spiny leaves. The spiny-leaved species were regarded as a related group, but the molecular study by Clarkson et al (2016) sampled two of the species, Trichilia aquifolia and T. triacantha, and these did not form a clade. (The non-spinyleaved species were not sampled).…”