A chloroplast genealogy of myrmecophyticMacarangaspecies (Euphorbiaceae) in Southeast Asia reveals hybridization, vicariance and long‐distance dispersals

Abstract

Macaranga (Euphorbiaceae) includes about 280 species with a palaeotropic distribution. The genus not only comprises some of the most prominent pioneer tree species in Southeast Asian lowland dipterocarp forests, it also exhibits a substantial radiation of ant-plants (myrmecophytes). Obligate ant-plant mutualisms are formed by about 30 Macaranga species and 13 ant species of the genera Crematogaster or Camponotus. To improve our understanding of the co-evolution of the ants and their host plants, we aim at reconstructing comparative organellar phylogeographies of both partners across their distributional range. Preliminary evidence indicated that chloroplast DNA introgression among closely related Macaranga species might occur. We therefore constructed a comprehensive chloroplast genealogy based on DNA sequence data from the noncoding ccmp2, ccmp6, and atpB-rbcL regions for 144 individuals from 41 Macaranga species, covering all major evolutionary lineages within the three sections that contain myrmecophytes. A total of 88 chloroplast haplotypes were identified, and grouped into a statistical parsimony network that clearly distinguished sections and well-defined subsectional groups. Within these groups, the arrangement of haplotypes followed geographical rather than taxonomical criteria. Thus, up to six chloroplast haplotypes were found within single species, and up to seven species shared a single haplotype. The spatial distribution of the chloroplast types revealed several dispersals between the Malay Peninsula and Borneo, and a deep split between Sabah and the remainder of Borneo. Our large-scale chloroplast genealogy highlights the complex history of migration, hybridization, and speciation in the myrmecophytes of the genus Macaranga. It will serve as a guideline for adequate sampling and data interpretation in phylogeographic studies of individual Macaranga species and species groups.

Progressive island colonization and ancient origin of Hawaiian Metrosideros (Myrtaceae)

“…As our data are from a maternally inherited organelle genome (the chloroplast), an argument can be made that the lack of correlation between morphotypes and genotypes is due to hybridization and chloroplast capture (resulting in reticulate inheritance of the chloroplast genome). Several studies have found evidence for extensive chloroplast capture (Steane et al 1998;Palme et al 2004;Bänfer et al 2006;Jakob & Blattner 2006) that in some cases explains the apparent non-monophyly of morphotypes. A study of New Zealand Metrosideros found that chloroplast capture within climatic refugia could entirely explain apparent non-monophyly of those species (Gardner et al 2004).…”

Phylogeny, geographic distribution, and new taxonomic circumscription of the Crocus reticulatus species group (Iridaceae)

“…but also proved useful to illustrate haplotype relationships at higher taxonomic levels (Bänfer et al, 2006;Jakob and Blattner, 2006;Kiefer et al, 2009;Gurushidze et al, 2010). Here a clear split is visible in nuclear and chloroplast data, separating a clade of taxa occurring in the west and northeast of the distribution area from the clade of Turkish taxa.…”

“…In addition to these nuclear loci, we also analyzed sequences of 3 chloroplast regions. One of these (trnL-F) is often used in plant phylogeography, as it is normally quite variable (e.g., Bänfer et al 2006;Jakob and Blattner, 2006). PCR primers for the other 2 regions (rps16-trnQ and matK-trnK) were newly designed for this study.…”

Patterns of avian diversification in Borneo: The case of the endemic Mountain Black-eye (Chlorocharis emiliae)

“…From work on lowland taxa and preliminary studies of montane populations (Moyle et al 2005, Moyle et (Sheldon et al 2009, Irham et al 2012. Substantial evidence indicates that lowland bird populations were subdivided, presumably during one or more glacial periods, into forest refugia in western Sundaland and eastern Borneo, as were other groups of Sundaic organisms (e.g., Brandon-Jones 1998, Thomas 2000, Gathorne-Hardy et al 2002, Gorog et al 2004, Bänfer et al 2006, Iwanaga et al 2012, Ohtani et al 2013). This subdivision would have occurred as lowland forest retreated or shifted position and montane forest expanded and dominated central Borneo ( Figure 2B).…”