Evolution of pollen morphology in Loranthaceae

Abstract

Earlier studies indicate a strong correlation of pollen morphology and ultrastructure with taxonomy in Loranthaceae. Using high-resolution light microscopy and scanning electron microscopy imaging of the same pollen grains, we document pollen types of 35 genera including 15 studied for the first time. Using a molecular phylogenetic framework based on currently available sequence data with good genus-coverage, we reconstruct trends in the evolution of Loranthaceae pollen and pinpoint traits of high diagnostic value, partly confirming earlier intuitive hypotheses based on morphological observations. We find that pollen morphology in Loranthaceae is strongly linked to phylogenetic relationships. Some pollen types are diagnostic for discrete genera or evolutionary lineages, opening the avenue to recruit dispersed fossil pollen as age constraints for dated phylogenies and as independent data for testing biogeographic scenarios; so far based exclusively on modern-day data. Correspondences and discrepancies between palynological and molecular data and current taxonomic/systematic concepts are identified and suggestions made for future palynological and molecular investigations of Loranthaceae.

Eocene Loranthaceae pollen pushes back divergence ages for major splits in the family

“…5). Notanthera heterophylla is one of two species that comprise the two monotypic genera of the South American Notantherinae; a subtribe of the Psittacantheae neither resolved as clade nor rejected with high support in molecular-phylogenetic inferences (Grímsson, Grimm & Zetter, 2017: Files S1, S6). The sculpturing of Profen MT2 is furthermore in line with the description and TEM image provided by Feuer & Kuijt (1980).…”

“…Tiegh. ex B.D.Jacks., has not only a different pollen (Feuer & Kuijt, 1980; Grímsson, Grimm & Zetter, 2017) but is also genetically distinct (Fig. 7).…”

“…Although molecular and morphological interrelationships of Loranthaceae genera are considered now to be relatively clear (Nickrent et al, 2010; Su et al, 2015; but see Grímsson, Grimm & Zetter, 2017), the timing of divergence between the genera has not been cross-checked with available evidence from the fossil record (e.g. Muller, 1981; Song, Wang & Huang, 2004; Macphail et al, 2012).…”

“…Grímsson, Grimm & Zetter (2017) distinguished four general types (Pollen Type A, B, C, D), of which only one (Pollen Type A) could be confused with pollen of other Santalales lineages, and would unlikely be recognised as Loranthaceae pollen if found in a fossil pollen sample. Combined application of light microscopy (LM), scanning-electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that pollen morphologies—including the many variants of B-type pollen—are conserved at various taxonomic levels within Loranthaceae (Feuer & Kuijt, 1978, 1979, 1980, 1985; Caires, 2012; Grímsson, Grimm & Zetter, 2017). Thus, dispersed fossil pollen can aid in the reconstruction of past distributions of Loranthaceae lineages and shed light on the timing of the origin of the modern clades.…”

Antimicrobial activity of crude extracts of endophytic fungi from Oryctanthus alveolatus (Kunth) Kuijt (Mistletoe)

“…This plant, commonly known as mistletoe, like other species of the family Loranthaceae, is a parasite found on the branches and trunks of trees (Vinod et al, 2005). The species occurs in temperate to tropical climates of Central and South America, Europe, Africa, the Middle East, and throughout Asia and Australia, and it currently consists of 76 genera and 1076 species (Grímsson et al, 2017). The species O. alveolatus is used in folk medicine to treat several diseases, such as stomach cancer (Scudeller et al, 2009), malaria, and the treatment of fractures (Salgado, 2007).…”