Study On The Pollen Morphology And Evolution Of Malva, Saxifraga And Grape

Malvids,Saxifragales and Vitales form a paraphyletic group in the APG? classification system,which belongs to superrosids in eudicots and includs Geraniales,Myrtales,Crossosomatales,Picramniales,Sapindales,Huerteales,Malvales,Brassicales,Saxifragales and Vitales.This group comprises of 75 families,1766 genera and c.34981 species,and make up about 9.9% of present angiosperm.Using 17 sequence data sets(18S r DNA,26 S r DNA,atp B,mat K,ndh F,psb BTNH,rbc L,rpo C2,rps16,rps4,atp1,mat R,nad5,rps3),we constructed the phylogenetic tree of these clades with 162 genera,75 families,including 52 genera,49 families,15 orders in core eudicots.Nineteen pollen characters were selected and coded.We reconstructed pollen character evolution by ML and MP analyses.The main results are as followings:.The paraphyletic group of malvids,Saxifragales and Vitales is mostly characterized by pollen released as monads,with grains isopolar,radially symmetrical,compound aperture structure and globose.The pollen characters,including dispersal unit,aperture structure,infratectum,foot layer and viscin threads,are conservative,while pollen size,aperture numbers,endoaperture shape,superatectal element shape and tectum sculpture show rich diversity and complex evolutionary.Except pollen size,endoaperture shape and tectum sculpture,all the other pollen characters present distinct ancestral states,like circular in polar view,with three equatorially-distributed aperture,endoapertures present,granulate aperture membrane,ectoaperture colpate,superatectal elements and viscin threads absent,infratectum and foot layer present.Evolutionary tendencies of some pollen characters were shown,pollen getting bigger,increasing of aperture numbers,aperture position turning to polar and global from equatorial,aperture structure changing from simple to compound,superatectal elements present,superatectal element shape and tectum sculpture getting more complex.Pollen morphology can offer evidence for phylogenetic relationship among different classes of the clades.Small pollen is the synapomophy for Huertales-Malvales-Brassicales clade and supporting its monophyly.Pollen released as tetrads,with grains heteropolar and oblate,triangular in polar view,large pollen,porate ectoaperture,granulate foot layer and viscin threads present are synapomophies for Onagraceae,supporting monophyly of Onagraceae.Lobate in polar view,rugulate tectum sculpture,infratectum and foot layer absent are synapomophies for Gyrostemonaceae,supporting monophyly of this family.Striate tectum sculpture is a synapomophy for Nitrariaceae-Biebersteiniaceae clade,suggesting them as sister group.Lalongate endoaperture shape is the synapomophy for Burseraceae-Anacardiaceae clade and Simaroubaceae-Rutaceae clade,supporting monophyly of these two clades separately.Simple aperture structure is the synapomophy for Altingiaceae-Daphniphyllaceae-Cercidiphyllaceae-Hamamelidaceae clade,supporting its monophyly.Circular endoaperture shape is the synapomophy for Koeberlingiaceae-Salvadoraceae-Bataceae clade,and supporting monophyly of this clade.