Pollen morphologyof the least known families of the order Asterales

TELLERÍA, M.C.; BARREDA, V.; PALAZZESI, L

REVIEW OF PALAEOBOTANY AND PALYNOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019 vol. 262 p. 1 - 9

0034-6667

The order Asterales comprises ca. 26000 species distributed in 11 unevenly sized families (Table 1). The MGCA core of Asterales (Menyanthaceae, Goodeniaceae, Calyceraceae and Asteraceae)along with Campanulaceae, represents about 98% of the total diversity of the order (Lundberg, 2009).The remaining families of the Asterales includeRoussaceae, the smallest family (four genera and six species), Phellinaceae (one genus and 10 species), Alseuosmiaceae (five genera and 11 species), Argophyllaceae (two genera and 21 species), and Pentaphragmataceae (one genus and 30 species) (Lundberg, 2009; APG, 2016).Most of these small families comprise shrubs or trees with the exception of Pentaphragmataceae which are mostly herbs. These small families inhabit the Southern Hemisphere: Australia, New Guinea, New Zealand, New Caledonia and Solomon Islands, with the exception of the subfamily Rousseoideae (Roussaceae) which isendemic to Mauritius (Lundberg, 2009). Lundberg & Bremer (2003) reconstructed a reliable phylogeny of the order Asterales on the basis of both, molecular and morphological data. These authors, however, found weak to moderate support in the circumscription of some basal clades, in particular the named APA clade formed by the familiesAlseuosmiaceae, Phellinaceae and Argophyllaceae. The necessity of additional data to define new potential synapomorphies within Asterales was later stressed by Lundberg (2009). The knowledge about pollen morphology of these small families within Asterales is relatively scarce comparing with the great amount of morphological pollen data coming from the MGCA clade. Only 13 out of 49 species were studied (Dunbar, 1978; Praglowski and Grafstrom, 1985 and; Polevova, 2006). Herewe explore the pollen morphology of 18 species of the smallest Asteralean families:Alseuosmiaceae, Argophyllaceae, Pentaphragmataceae, Phellinaceae and Roussaceae, on the basis of detailed microscopy analysis (light microscope, scanning electron microscope and transmission electron microscope), providing additional characters, some of them overlooked in previous analyses.Our new data will provide novel structures for future taxonomic and phylogenetic studies. These characters can be potentially useful for accurate identification of dispersedfossil pollen grains found in sediments.