Pollen morphology of Croton sect. Lamprocroton (Müll. Arg.) Pax (Euphorbiaceae) and its taxonomic implications

A palynological analysis of 22 taxa of Croton sect. Lamprocroton (Müll. Arg.) Pax was accomplished in order to obtain evidence for a good interspecific delimitation and phylogenetic characterization of this group. Samples of 22 taxa (from which approximately 90% of the species belonged to this section) were obtained from herbarium specimens; moreover, pollen grains were analyzed with light and scanning electron microscopy. Characters observed from pollen grain diameter and from exine ornamentation were registered and compared. Pollen grains were found to be spherical, apolar, inaperturate and with a diameter ranging from 49.32±0.94 μm in C. ehrenbergii Schltdl. to 86.42±1.33 μm in C. muellerianus L. R. Lima . Pollen morphology of three recently described species of Croton was analyzed for the first time herein. In addition the results of this study confirm the distinctness of these species but do not support a recently proposed new variety of C. pallidulus Baill.     

Pollen morphology of Euchaetis and Macrostylis (Diosminae-Rutaceae) and its taxonomic implications

Pollen morphology of Euchaetis and Macrostylis , both members of the taxonomically problematic subtribe Diosminae (Rutaceae), was investigated by LM, SEM and TEM. Here we report on the taxonomic significance of pollen morphology based on a comparative study of 28 infrageneric taxa. Three pollen types were found, namely reticulate (common to both genera), perforate (in Euchaetis ) and striato-reticulate (in Macrostylis ). Pollen data provide evidence of relationships between the two genera as well as with other genera, and further support for the macromorphological evidence suggesting the generic re-classification of the Diosminae.     

Pollen morphology of Strobilanthes Blume (Acanthaceae) in China and its taxonomic implications

The pollen morphology of 37 Chinese species of Strobilanthes Blume (Acanthaceae), a large and taxonomically problematic genus, was investigated by LM and SEM. Two distinct pollen shape classes, ellipsoid and spheroidal, recognised by earlier workers were found. Eight pollen types could be distinguished on the basis of variation in ornamentation, and the number, distribution and type of apertures. Five of these fall within twenty two pollen types reported from Strobilanthes in southern India and Sri Lanka. Three new pollen types are also described, further extending the palynological diversity of the genus. From the results presented, the characters of palynological diversity and the related taxonomic implications are discussed.     

Primula cusickiana (Primulaceae) and its varieties

Primula domensis Kass & S. L. Welsh,P. maguirei L. O. Williams, andP. nevadensis N. H. Holmgren are reduced to varietal status underP. cusickiana (A. Gray) A. Gray.     

Pollen grain morphology ofCoris (Primulaceae)

Pollen grain morphology, sculpturing, and wall ultrastructure are investigated in two species ofCoris (Primulaceae),C. monspeliensis L. andC. hispanica Lange. The study includes both acetolysed and unacetolysed pollen. No evidence of any major palynological difference is recorded between these two species, apart from a somewhat larger pollen inC. monspeliensis. However,Coris can be distinguished from the remaining members of thePrimulaceae by the conjunction of relatively large pollen grains, prominent margo, and particular tectal pattern causing a reticulate surface with minute luminal perforations decreasing towards the colpi. From both these distinctive features, and others typically primulaceous, some evolutionary considerations are inferred. Finally, the higher proportion of irregular grains inC. hispanica is interpreted in light of environmental stress.     

Pollen morphology of Phyllosma and Sheilanthera (Diosminae: Rutaceae) and its taxonomic implications

Phyllosma (two species) and Sheilanthera (one species) are members of the taxonomically problematic subtribe Diosminae, Rutaceae. Pollen morphology of all three species was investigated by LM, SEM and TEM to shed light on their relationships to other genera of the subtribe. Sheilanthera shares pollen morphological features with many other species in the subtribe, but the pollen of Phyllosma is distinctive. Possible relationships between Sheilanthera and Acmadenia, and between Phyllosma and Agathosma are suggested. The macromorphological characters of the species correspond to the pollen morphology.     

Pollen morphology of Diosma and Coleonema (Rutaceae: Diosminae) and its taxonomic implications

The pollen morphology of Diosma and Coleonema of the taxonomically problematic subtribe Diosminae (Rutaceae) was investigated to determine its taxonomic relevance. Pollen of 26 of the 28 species of Diosma and of each of the eight species of Coleonema was investigated by LM, SEM and TEM. In pollen of Diosma the exine sculpturing is uniform, and only one pollen type, reticulate, could be distinguished. In contrast, exine sculpturing shows interspecific variation in Coleonema and three distinct types, striate, reticulate and perforate, could be discerned. Species groupings indicated by the pollen types suggest possible relationships between species within Coleonema and with other genera that were not previously apparent. Pollen data support macromorphological evidence that suggests the generic re-classification of the Diosminae.     

Pollen morphology ofPyrola and its taxonomic significance

Pollen from 152 collections representing 16Pyrola species was examined with LM, SEM and TEM. The genusPyrola is stenopalynous in having tetrads and 3-colporoidate grains. However, a continuous and serial variation in the exine sculpture and the tetrad diameter (D) was revealed within the genus. Křísa's system ofPyrola (1971) was re-examined in the light of these palynological characters which may have a taxonomic significance, as well as the external morphology. P. minor (only member of the subgenusAmelia), which is characterized by having small (D=30–35 μm) pollen tetrads with verrucate sculpture must best be placed near sectionPyrola of the subgenusPyrola. P. faurieana must be segregated from sectionChlorantha and together withP. media placed intermediate between the subgenusAmelia and sectionPyrola of the subgenusPyrola based on their larger (D=ca. 40 μm) pollen tetrads with verrucate sculpture. Two series of sectionChlorantha excludingP. faurieana are differentiated in the exine sculpture. Therefore, they are regarded as the distinct taxonomic groups. SectionScotophylla is characterized by having psilate sculptured pollen tetrads, which indicates that its sectional rank is sufficiently asserted. The evolutionary trend in the exine sculpture from verrucate through rugulate to psilate is suggested withinPyrola.     

Pollen morphology and its taxonomic significance of the monotropoideae (Ericaceae)

A palynological survey, including LM, SEM and TEM is presented for eight genera, nine species and 76 samples of the Monotropoideae which is composed of 10 genera and 13 species. On the basis of the aperture number and shape, the following six pollen types are recognized: 1) 3-colp(oroid) ate—Allotropa, 2) 2-colpor(oid)ate—Monotropsis andHemitomes, 3) 4-colpor(oid)ate—Pterospora, Sarcodes andPleuricospora, 4) 2- and 3-colpor(oid)ate—Monotropa hypopitys, 5) 3-colporate and-porate —Monotropa uniflora, 6) 3- to 4- porate—Monotropastrum humile. Relationships among taxa within the Monotropoideae are illustrated on the palynological characters including the aperture type, exine sculpture and structure. Both pollen grains with two and four apertures have evolved independently from pollen grains with three apertures, according to the infraspecific variation of aperture numbers and the usual occurrence of three-aperturate pollen grains in the Ericaceae. 3-colp(oroid)ate pollen ofAllotropa is the most primitive and occupies an isolated position in the subfamily, on the other hand 3- to 4-porate pollen ofMonotropastrum humile is most advanced in the subfamily, probably even in the Ericaceae. A reduced sexine inMonotropastrum humile appears to be a specialized pollen character. Infraspecific geographical difference in palynological characters is revealed in two species ofMonotropa for the first time.M. hypopitys is basically characterized by pollen grains with two apertures in the New World vs. three apertures in the Old World.M. uniflora is basically characterized by 3-porate pollen in the New World vs. 3-colporate in the Old World. In both species pollen grains with more primitive characters usually occur in the Old World.     

Pollen morphology inLinum sect.Macrantholinum

Pollen of the two distylous species which make upLinum sect.Macrantholinum differs from that of other distylous species in the genus in being multiporate and in having much more modest differences in exine sculpturing between grains from long- and short-styled plants. Pollen morphology does not help in relating the two species to others in the genus but does support their retention in a separate section.     

Pollen morphology of Justicia L. (Acanthaceae) from Thailand and its taxonomic value

The acetolysed pollen of 33 species of the genus Justicia in Thailand is investigated using both light and scanning electron microscopy. The pollen of the genus is characterised as being isopolar, bilaterally or radially symmetrical, with mostly prolate or prolate spheroidal shape. Based on characters with high factor loading in the cluster analysis and principal components analysis, the studied species are divided into two major groups; one with 3-colporate with six pseudocolpi and the other with 2-porate or 2–3-colporate with aperture areas. The pollen morphology of each group is described and illustrated. Pollen characters are useful for taxonomic delimitation and relationships among Thai species.     

Pollen morphology and its taxonomic significance in the tribe Gochnatieae (Compositae, Gochnatioideae)

In the context of recent molecular phylogenies of the basal grades of Compositae, we investigated the utility of pollen morphology within the tribe Gochnatieae. The pollen of 64 species of Anastraphia, Cnicothamnus, Cyclolepis, Gochnatia, Pentaphorus, and Richterago was studied using light microscopy and scanning electron microscopy. In addition, three extra-Gochnatieae genera (Ianthopappus, Leucomeris, and Nouelia) were examined as they were traditionally morphologically related to members of the tribe Gochnatieae. Three of the species of Gochnatieae were examined using transmission electron microscopy. Two pollen types, and two new subtypes, have been recognized on the basis of the pollen shape, size, and exine sculpture. The pollen features of Gochnatia sect. Moquiniastrum and G. cordata are similar and distinctive within the genus and support the recently re-circumscribed section Hedraiophyllum. Within the species with echinate pollen surface, the distinctive spine length of Anastraphia supports its recent resurrection as a genus. The identity of Pentaphorus could not be supported by pollen features as was for other morphological characteristics. The pollen features shared across Cyclolepis, Ianthopappus, Leucomeris, Nouelia and Gochnatia sect. Moquiniastrum, as well as those shared by Richterago and Anastraphia could be a result of parallel evolution.     

Pollen morphology of Hosta Tratt. in China and its taxonomic significance

In this study, pollen morphology of 11 taxa of Hosta in China, three Chinese species, five introduced species, and three cultivars, was observed by scanning electron microscopy (SEM) and compared with that of related genera (Hemerocallis, Agave, and Yucca). Pollen grains of Hosta were long-ellipsoidal or ellipsoidal, 20?C65?×?52.5?C142.5???m in size, bilaterally symmetrical, and monosulcate on the distal face. Reticulate and rugulate exine ornamentation was observed in different taxa, and the rugulate type can be further divided into rugulate, rugulate?Cbaculate, and rugulate?Cgranulate subtypes. The exine ornamentation may have evolved in the order: reticulate????rugulate????rugulate?Cbaculate????rugulate?Cgranulate. Furthermore, the rugulate exine ornamentation was the predominant ornamental type in Hosta except for one species with the reticulate type; this is markedly different from that of Hemerocallis, Agave and Yucca. Thus, our data support the proposal by Dahlgren and Clifford (The Monocotyledons: a comparative study. Academic Press, London, 1982) that these Hosta species constitute an independent family?CHostaceae.     

DNA barcoding in closely related species: A case study of Primula L.sect.Proliferae Pax (Primulaceae) in China

DNA barcoding is a method of identifying species by analyzing one or a few short standardized DNA sequences. There are particular challenges in barcoding plants, especially for distinguishing closely related species. Hence, there is an urgent need to evaluate the performance of candidate loci for distinguishing between species, especially closely related species, to complement the rbcL + matK combination suggested as the core barcode for land plants. We sampled 48 individuals representing 12 species in Primula sect. Proliferae Pax in China to evaluate the performance of eight leading candidate barcode loci (matK, rbcL, rpoB, rpoCl, trnH-psbA, psbK-psbI, atpFatpH, and internal transcribed spacer (ITS)). The core combination rbcL + matK gave only 50% species resolution in sect. Proliferae. In terms of intraspecies and interspecies divergence, degree of monophyly, and sequence similarity, ITS, trnH-psbA, and psbK-psbI showed good performance as single-locus barcodes. Internal transcribed spacer displayed the highest genetic divergence and best discriminatory power, both alone and in combination with rbcL +matK (83.3% species resolution). We recommend evaluating the use of ITS for barcoding in other species. Low or single copy nuclear regions would provide more sophisticated barcoding tools in the long term, even though further research is required to find suitable loci.     

Nutlet sculpturing inScutellaria sect.Resinosa (Lamiaceae) and its taxonomic utility

Nutlet sculpturing of 22 taxa ofScutellaria sect.Resinosa, representing 18 of its 19 species, and the monotypic genusSalazaria was studied by scanning electron microscopy (SEM). The nutlets of sect.Resinosa, while remarkably variable among themselves, differed from hypothetically closely related sections in lacking circumferential banding and sessile glands. Species could be grouped by surface sculpturing into seemingly meaningful phenetic clusters.Scutellaria potosina var.platyphylla was sufficiently distinct micromorphically so as to be elevated to specific status asScutellaria platyphylla comb. and stat. nov. The significance of nutlet microcharacters within sect.Resinosa is discussed, especially as compared to closely related sections. The genusSalazaria had nutlet sculpturing quite different from all taxa belonging to sect.Resinosa.