Diversification of plant species in a subtropical region of eastern South American highlands: a phylogeographic perspective on nativePetunia(Solanaceae)

Abstract

In the Southern and Southeastern Brazilian highlands, a clade of seven species of Petunia that are endemic to the region (P. altiplana, P. bonjardinensis, P. guarapuavensis, P. mantiqueirensis, P. reitzii, P. saxicola and P. scheideana) exists in association with grassland formations. These formations are isolated in high-altitude regions, being surrounded by forested areas, and experienced contraction-expansion cycles associated with the glacial cycles of the Pleistocene. To understand the evolutionary history of this group, the divergence of which is probably linked to these past shifts in habitat, we analysed the sequences of the plastidial intergenic spacers trnH-psbA and trnS-trnG from populations throughout the known distributions of all seven species. The common ancestor of this highland clade started to differentiate ∼0.9 million years (Myr) ago, which corresponds to a high diversification rate of 2.06 species per Myr in the intervening period. The high level of haplotype sharing among several species in the clade and the absence of reciprocal monophyly suggest the persistence of ancestral polymorphisms during speciation events and/or past hybridization, because no hybrid was found. Four of the five species displayed very low genetic diversity and possessed either one or two haplotypes, which is consistent with long-term isolation in restricted areas. The three more diverse species displayed significant population structure, and P. altiplana showed a clear signs of population growth during the last glacial period. These results suggest that diversification occurred as a result of expansion of the ancestral species of the clade during glacial periods followed by fragmentation and isolation during retraction in interglacial periods.

Phylogeographical structure inferred from cpDNA sequence variation of Zygophyllum xanthoxylon across north-west China

“…Chloroplast DNA (cpDNA) is maternally inherited in the most angiosperm plants and is considered a single, nonrecombinant unit of inheritance (Hewitt 2000;Liu et al 2009;Lorenz-Lemke et al 2010), it is associated with seed dispersal and range expansion (Cruzan and Templeton 2000), and can show the contribution of seed movement to total gene flow (Orive and Asmussen 2000;Song et al 2002), and so it is a useful molecule for phylogeographical investigation. In present study, we used two chloroplast DNA regions, rpl32-trnL and psbK-psbI, to examine the phylogeographical pattern of 31 populations of Z. xanthoxylon across entire distribution range in China.…”

Contribution of WUSCHEL-related homeobox (WOX) genes to identify the phylogenetic relationships among Petunia species

“…As a result of their high phenotypic diversity and rapid speciation (Lorenz-Lemke et al , 2010), Petunia species are an ideal model to examine evolutionary innovations and adaptation.…”

“…Petunia bajeensis , a species that occurs just in lowlands, was the sister group of the highland species (Figure 1B), confirming previous findings of phylogenies based on combined nuclear and plastid markers (Reck-Kortmann et al , 2014). However, such relationships were not observed in phylogenies obtained through plastid sequence analysis (Lorenz-Lemke et al , 2010) or plastid RFLP (Ando et al , 2005a), in which P. bajeensis is placed in the lowland group of species, or those based only on nuclear sequences (Chen et al , 2007; Kriedt et al , 2014), in which P. bajeensis is placed in the highland group, with different sister species. All highland species share morphological traits with P. bajeensis , especially the stamen filaments adnated up to half of the corolla tube (Stehmann et al , 2009).…”

“…Despite that P. guarapuavensis and P. scheideana share several morphological traits and have a similar geographic distribution (Figure 1A), they occupy different branches in molecular biology-based analyses (Chen et al , 2007; Lorenz-Lemke et al , 2010; Reck-Kortmann et al , 2014). Ando et al (2005b) suggested as valid the taxa P. integrifolia subsp.…”

“…Petunia Juss. has undergone rapid diversification during the Pleistocene climatic changes (Lorenz-Lemke et al , 2010), and molecular phylogenies did not resolve all morphological species (Kulcheski et al. , 2006; Chen et al.…”