Systematics Of Heterolamium (Lamiaceae) And Tribe Urticeae (Urticaceae)

Phytotaxonomy is one of the most basic subjects of biology.It relies on the evidence from several other subjects which could solve the taxonomic problems.Therefore,it is comprehensive and needs to constantly absorb the new evidence from different disciplines.A Chinese endemic genus Heterolamium(Lamiaceae)and tribe Urticeae(Urticaceae)are examples in this taxonomic study,combining with molecular sustematics,traditional morphology,cytology and seed micro-morphological.Main results are as follows:A Chinese endemic genus Heterolamium(Lamiaceae),the phylogenetic position of this genus is still a controversy.This genus consists of 3 species: H.debile var.debile(Hemsley)C.Y.Wu,H.debile var.cardiophyllum(Hemsley)C.Y.Wu and H.debile var.tochauense(Kud?)C.Y.Wu.Based on its distinct morphological features,it was previously regarded as the only genus of the tribe Heterolamieae,sister to the tribes Stachydeae and Saturejeae of the subfamily Lamioideae(Lamiaceae).However,recent palynological studies identified this genus as sister to the rest of subtribe Nepetinae(Lamiaceae).To resolve the dispute,we used comprehensive sampling and DNA sequence data from both the nuclear(ITS and ETS)and the plastid(rbc L,rps16,trn L-F,and rpl32-trn L)genomes to reconstruct molecular phylogeny of Heterolamium and identify the generic relationship with subtribe Nepetinae.Maximum parsimony and Bayesian inference were used to analyze sequence data.Our results strongly support the conclusion that Heterolamium is a member of Nepetinae.There are two clades inferred in subtribe Nepetinae: Clade I including Heterolamium,Hymenocrater,Marmoritis,Nepeta,Drepanocaryum and Lophanthus;Clade II including Meehania,Lallemantia,Dracocephalum,Glechoma,Agastache,and Hyssopus.Furthermore,some typical Heterolamium morphological traits,such as 15-nerved calyx,stamens and so on,are similar with species in subtribe Nepetinae,which provide powerful support for our conclusion as well.Tribe Urticeae(= Urereae(Gaud.)Wedd.(1854))belongs to the nettle family(Urticaceae),comprising eleven genera about 210 species.The members of the tribe are heterogeneous in life forms,ranging from herbs or shrubs,lianas to trees.Their obvious morphological synapomorphies such as stinging hairs and perianth four-lobed of pistillate flowers are often used to distinguish a species as being a member of Urticeae.There are eleven genera of tribe Urticeae,including Dendrocnide,Discocnide,Girardinia,Hesperocnide,Laportea,Nanocnide,Obetia,Poikilospermum,Urera,Urtica,and Zhengyia.Owing to its great constancy under the influence of environmental pressures than other morphological traits,seed morphology and micromorphology is likely to provide new possibilities to understand and clarify the evolutionary relationships among species of Urticeae.In this study,we analyzed seed morphological and micro-morphological traits of tribe Urticeae to demonstrate the discrepancies and to explain the relationships among these genera.We investigated achenes from more than 70 species,corresponding to eleven genera of tribe Urticeae.Our main results are obtained to enhance current classifications and indicate that achene morphology provides useful information to delimitate tribe Urticeae.Achene shape,symmetry,surface sculpture and stigma are helpful characters at the genus level and offer a method to comprehend interrelationships within this tribe.Urtica,Laportea and Urera are not monophyletic groups.Moreover,we can infer the evolutionary trend of achene characters(achene shape,symmetry and surface sculpture).Most achenes in modern Urticeae are ovoid and symmetric or approximate symmetric,whereas some species of Laportea and Urera are different.As a consequence,ovoid and symmetric achenes could be considered as potential synapomorphies for this tribe.Micro-sculpture becomes complex,but ridge of reticulum turns inconspicuous except in Girardinia.Even in Girardinia,mesh has been changed into polygon.