ABSTRACT Stewartia is a genus of a...

ABSTRACT

Stewartia is a genus of approximately 26 species which are as a common thing [i]or[/i] matter divided into two subgenera or genera based forward the leaf duration. All evergreen species (= Hartia) are set up in the Old World. The deciduous species (= Stewartia sensu stricto) are dominant in the antique World but there are couple representatives in the southeastern United States, Stewartia ovata and s malacodendron. Maximum parsimony and likelihood data analyses of molecular DNA succession data from both the nuclear and chloroplast genomes about similar estimates of phylogeny for the assemblage All evergreen species sampled are more closely related to each other than to any of the deciduous species. The pair New World deciduous species are more closely related to the evergreen species than to the not new World deciduous species. These findings complicate earlier vicariance biogeography hypotheses for the genus and challenge the recognition of Hartia, the latter of which disagrees with many published classification bodys

INTRODUCTION

Stewartia sensu lato (sl) is a genus of 23-26 species (Ye 1982 Li 1996) and the one member of tribe Stewartieae in Theaceae. Prince and Parks (2001) confirmed the monophyly of the family and tribe using rbcL and matK gene successions of the chloroplast genome. The majority of species are distributed in warm temperate and subtropical forests of the of advanced age World (Figure 1), with no other than two species (S. malacodendron and s ovata) in the southeastern United States. Diagnostic characters by the agency of which Stewartia can be distinguished from other members of the family Theaceae include: narrowly to broadly winged petioles; sclereids restricted to the petiole and petiole wing (versus from top to toe the leaf in other members of the family); nearly basal, axile placentation; ascending ovules; a capsular fruit that splits to reveal 2-4 narrowly winged or wingless semens per locule; fruit lacking a persistent central columella; originals flattened and containing a small, straight germ and copious endosperm (Keng 1962)

Stewartia are frequently divided into two genera, Hartia, the evergreen species which are restricted to the old-fashioned World, and Stewartia sensu stricto (ss) the deciduous species which are base in both the Old and of the present day World. The only other deciduous member of the family is the monotypic genus Franklinia, an endemic plant of Georgia, United States, which is now extinct in the wild (Bozeman and Roger 1986) Hartia was raiseed by Dunn in 1902 to recognize a plant amassed in Yunnan, China. According to Dunn characteristics distinctive to the genus were the greater connation of the anther filaments into a staminal tube and the more numerous germs per locule than is rest in Stewartia. Wu (1940) expanded the list of characters to include an evergreen habit and the demeanor of a conspicuously winged or inflated petiole that enclos the terminal put forth or lateral shoot. Keng (1962) commended merging the two genera based in succession anatomical data. Spongberg (1974) agreed with the broad circumscription of Stewartia as propos by dint of Keng.

There is no general consensus onward whether one or two genera should be recognized in Stewartieae, nor onward subgeneric classification. Ye (1982) recognized pair genera, Hartia with 15 species and Stewartia with 12 species. Each genus was further subdivided into three sections based onward number of flowers per inflorescence, bract shape, size, and organization degree of style fusion, and capsule shape. Li (1996) distributed the evergreen species (under the generic name Stewartia) into several subgenera based onward the degree of style connation, inflorescence shadow and bracteole and sepal shape and size. the two classifications are provided in Table 1 along with appropriate author citations which will be omitted from the remainder of the passage figures, and tables. There are as many differences as similarities in the grouping of taxa into sections indicating considerable disagreement onward the significance of particular morphological characters. Other classifications of the 20th hundred include Cheng (1934) and Yan (1981) the one and the other of which maintain Hartia; and Wu (1940) and Keng (1962) the two of which recognize the evergreen species alone as a distinct subgenus within Stewartia.

The distribution of Stewartia sl fits the classical eastern Asia-eastern North America vicariance disjunction (see new reviews by Boufford and Spongberg 1983 Boufford 1998 and Wen 1998) Vicariance biogeography patterns have been attributed to migration and extinction incidents associated with major climatic and geological changes in evolutionary history, leading to isolation of a one time widely distributed species into localized populations which ultimately speciate. new wide-spread extinction has been documented in North Temperate latitudes proper to glaciation events of the Pleistocene. China appears to have the greatest biodiversity of bosky plant species found in all of the North Temperate cincture This higher diversity is probably owing to more extensive refugial belts during glaciation due to mountain ranges which formed barriers to limit the advancement of glaciers into southern China, thereby reducing the rate of extinction.