PALYNOLOGY AND SYSTEMATICS OF CUPHEA (LYTHRACEAE). I. MORPHOLOGY AND ULTRASTRUCTURE OF THE POLLEN WALL

A survey of pollen from 153 species of Cuphea has revealed a remarkable array of morphological forms. The survey involved light and electron microscope investigations of C. crassiflora, jorullensis, and koehneana to determine details of exine morphology, and a more general study of pollen from an additional 150 species. Comparison of pollen types within a single morphological category and within taxonomic groups (i.e., sections or subsections) indicates considerable variation at subgeneric levels. The genus is distinctly eurypalynous, and the extent to which pollen varies among the sections, subsections, species and varieties is probably exceeded by few genera of comparable size. The pollen is also variable within each taxon, but size studies of single-anther lactic acid preparations demonstrate the genus is not polymorphic, as in Lythrum, where pollen polymorphism is associated with heterostyly. The latter phenomenon is as yet unknown in Cuphea. These results reveal that pollen morphology constitutes an important and useful character for taxonomic studies of Cuphea.     

PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. I. INTRODUCTION AND GENERA ADENARIA THROUGH GINORIA

A palynological survey, including LM, SEM, and TEM, is presented for 10 genera of the Lythraceae s.s. (plus Alzatea to be assigned separate family status): Adenaria, Ammannia, Capuronia, Crenea, Cuphea, Decodon, Didiplis, Diplusodon, Galpinia, and Ginoria. Discussion of the results is deferred until the survey is complete, but already information of taxonomic interest is available for the 11 genera studied. The pollen data, consistent with results from cytology, anatomy, and embryology, suggest the current subgeneric classification into the Tribes Lythreae and Nesaeeae based on complete or incomplete septation of the ovary is not valid. The pollen of Alzatea is a generalized type and lacks the morphological features most characteristic of the Lythraceae (pseudocolpi, sculptured exine). The genus is being described as a separate family, and the pollen morphology is consistent with this treatment. The pollen of Cuphea is more diverse and shows little similarity to other genera in the family. It also has a unique combination of floral characters and lipid chemistry that suggests a separate category within the developing subfamilial classification of the Lythraceae.     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

绣球属(Hydrangea L.)及近缘属花粉形态的研究

为深入研究绣球属植物花粉形态的分类学价值和系统学意义,厘清绣球属与近缘属之间的系统发育关系,该文利用扫描电子显微镜(SEM,scanning electron microscope)对国产绣球属及其近缘属41种绣球花科(Hydrangeaceae)植物的花粉形态以及表面纹饰进行了观察。结果表明:绣球属及其近缘属的花粉为三孔沟;形状多数为长圆体形或近球体形;赤道面观为椭圆形或圆形;极面观多为圆形,少数为三角形或圆三角形。花粉外壁纹饰可分为网状和孔穴状。网眼内的三级纹饰可分为光滑和具颗粒状突起。根据花粉形状和外壁纹饰类型将上述物种划分为4个组,即花粉的形状为长圆体形,表面纹饰为孔穴纹饰;花粉的形状为长圆体形,表面纹饰为网状纹饰;花粉的形状为近球体形,表面纹饰为孔穴纹饰;花粉的形状为近球体形,表面纹饰为网状纹饰。以上可进一步细分为8个类型。上述表明花粉形态证据可为绣球属及其近缘属的属下分类和种间界定提供重要佐证;但结合前人的系统发育重建分析该属植物花粉形态的系统学意义相对有限,如花粉形态证据对于该属及其近缘种属系统发育树上大支的界定难以提供有力的证据。     

PHYLOGENETIC IMPLICATIONS OF DIVERSE SEED TYPES,CHROMOSOME NUMBERS,AND POLLEN MORPHOLOGY IN HOUSTONIA (RUBIACEAE)

Seed and pollen morphology were studied by light microscopy and scanning electron microscopy in 39 North and Central American species of Houstonia (including Hedyotis, but excluding Oldenlandia). Chromosome counts were obtained for eight taxa, of which five lacked previous chromosome data. A chromosome number of n = 17 for Houstonia gracilis is a new base number for the genus. Seed external morphology in the genus is very diverse, including variation in compression, margins, testa surfaces, and elaboration of ventral cavities or depressions and hilar ridges or their absence. Three types of pollen apertures are recognized: colporate with type A os, colpororate, and colporate with type B os, the last the most advanced type, occurring in H. caerulea and related species. The 39 species are arranged in twelve groups, based on correlation of seed, pollen, and chromosome data. Geographic distribution provides supplementary evidence for the distinctness and integrity of the six principal groups each composed of 2–9 species. Five of the six minor groups each with one species need chromosome data to facilitate future taxonomic decisions. Chromosome numbers of x = 6, 7, 8, 9, 10, 11, 13, and 17 are now known in this genus, and phylogenetic implications of the combined data are discussed.     

POLLEN BRUSH OF PAPILIONOIDEAE (LEGUMINOSAE): MORPHOLOGICAL VARIATION AND SYSTEMATIC UTILITY

The pollen brush commonly is referred to as a “bearded” or “pubescent” style in taxonomic literature and traditionally is taken to be an aggregation of trichomes on the distal end of the style, and occasionally including the stigma. We present data that support the taxonomic utility of the pollen brush but define it more specifically as a dense aggregation of erect trichomes emanating from the style (not stigma or ovary) and functioning in secondary pollen presentation. We recommend avoiding such vague terminology as bearded or pubescent styles as these refer not only to the pollen brush but also to ciliate and penicillate stigmas and ciliate styles. The latter three conditions have some taxonomic use, and since their occurrence is not necessarily correlated with the presence of a pollen brush, they should be distinguished from it. We estimate that the pollen brush has arisen independently in the following eight taxa: 1) Crotalaria and Bolusia (Crotalaraieae), 2) subtribe Coluteinae (Galegeae), 3) Tephrosia subgenus Barbistyla (Millettieae), 4) Adenodolichos (Phaseoleae subtribe Cajaninae), 5) Clitoria (Phaseoleae subtribe Clitoriinae), 6) the subtribe Phaseolinae (Phaseoleae), 7) the Robinia group (Robinieae), and 8) the tribe Vicieae. Its hypothesized homology within each of these groups is supported by a cooccurrence with other taxonomic characters, both morphological and molecular.     

POLLEN MORPHOLOGY OF THE TRIBE SWARTZIEAE (SUBFAMILY PAPILIONOIDEAE: LEGUMINOSAE). 1. INTRODUCTION AND ALL GENERA EXCLUDING ALDINA AND SWARTZIA

The pollen morphology of 9 of the 11 genera of the tribe Swartzieae is described together with that of Holocalyx and Cyathostegia, two genera recently removed from the tribe based on macromorphology. The pollen is small, spheroidal to subprolate, primarily tricolporate with a perforate tectum and generally typical of the Leguminosae. Nonetheless, many of the genera have distinctive pollen morphology. Baphiopsis is 6-colporate. The genera Harleyodendron, Lecointea and one species of Exostyles have supratectal spinules. Bocoa viridiflora has striate/rugulate ornamentation very distinct from the other species of the genus Bocoa. The exine stratification is varied but Candolleodendron has a very thick endexine and narrow foot layer. The pollen of African taxa does not differ significantly from that of South American taxa. Pollen morphology does not clarify the taxonomic relationships of the tribe and provides little evidence to assist in positioning Holocalyx and Cyathostegia.     

Pollen morphology of Chamaebuxus (DC.) Schb., Chodatia Paiva and Rhinotropis (Blake) Paiva (Polygala L., Polygalaceae)

Polygala L. is a large and highly diverse genus with complex taxonomy, but pollen morphological information for this taxon is scarce. In the present study, pollen characters have been used to assess the taxonomic delimitation and phylogenetic relationships of three newly established subgenera of Polygala: Chamaebuxus, Chodatia and Rhinotropis (sensu Paiva). The pollen morphology of 22 species has been examined using light microscopy and scanning electron microscopy of acetolysed material. The pollen of 15 of the species is examined for the first time. The pollen grains are isopolar, radially symmetrical, tectate and, typically, polyzonocolporate with numerous colpi running parallel to the polar axis, and an endocingulum around the equator. Two pollen types can be distinguished: Type I, which includes species belonging to Rhinotropis, and Type II, which includes species from Chamaebuxus and Chodatia. The two pollen types are described and the pollen of the three studied subgenera is illustrated. Despite the low infrageneric morphological diversity observed within the genus Polygala, quantitative characters of pollen grains support the current classification of the subgenera Chamaebuxus, Chodatia and Rhinotropis, and reveal a closer relationship between the first two taxa. Pollen characters are shown to be a useful and informative tool for assessing taxonomic position and phylogenetic relationships within Polygalaceae, especially at higher taxonomic levels.     

A combined light and scanning electron microscopy study

The uppermost Eocene Florissant Formation, Rocky Mountains, Colorado, has yielded numerous insect, vertebrate and plant fossils. Three previous comprehensive palynological studies investigated sections of lacustrine deposits of the Florissant Formation and documented the response of plant communities to volcanic eruptive phases but overall found little change in plant composition throughout the investigated sections. These studies reported up to 150 pollen and spore phenotypes. In the present paper, we used a taxonomic approach to the investigation of dispersed pollen and spores of the Florissant Formation. Sediment samples from the shale units containing macrofossils were investigated using light microscopy (LM) and scanning electron microscopy (SEM). The general picture of the palynoflora is in agreement with previous studies. However, the combined LM and SEM investigation provides important complementary information to previous LM studies. While a fairly large amount of previous pollen determinations could be confirmed, the purported taxonomic affinities of several pollen phenotypes need to be revised. For example, pollen referred to as Podocarpus or Podocarpidites sp. belongs to the Pinaceae Cathaya, Malus/Pyrus actually belongs to Dryadoideae, pollen of the form genus Boehlensipollis referred to as Proteaceae/Sapindaceae/Elaeagnaceae or Cardiospermum belongs to Sapindaceae but not to Cardiospermum, and pollen of Persicarioipollis sp. B with previously assumed affinities to Polygonaceae actually belongs to Thymelaeaceae. Pandaniidites and one type of Malvacipollis cannot be linked with Pandanaceae and Malvaceae. A few taxa are new records for Florissant (Ebenaceae: Diospyros; Mernispermaceae; Trochodendraceae: Tetracentron). In general, SEM investigations complement the LM palynological studies and improve the identification of dispersed pollen and spores and enable integration of data from dispersed fossil pollen into a wide range of comparative morphological, taxonomic, evolutionary, biogeographic and phylogenetic studies.     

POLLEN MORPHOLOGY AND ULTRASTRUCTURE OF KRAMERIA (KRAMERIACEAE): UTILITY IN QUESTIONS OF INTRAFAMILIAL AND INTERFAMILIAL CLASSIFICATION

The genus Krameria is currently recognized as an enigmatic, monotypic family of dicotyledons. Previous studies of morphology, anatomy, and cytology have been unable to establish unequivocably its phyletic affinities. We report here the results of an intensive investigation of the pollen of Krameria using light, scanning electron (SEM), and transmission electron microscopy (TEM). Pollen characteristics of the genus were compared to those of all families referred to the Polygalales and to selected species of the Leguminosae-Caesalpinoideae, both groups with which Krameria has historically been allied. Superficially, the pollen of Krameria resembles that of the legumes more than that of genera in the Polygalales. However, in ultrastructure, it differs from the pollen of all taxa investigated from both groups. Within Krameria, several variations of a basic type of 3-colporate pollen are discernible. Species with similar pollen variants appear, on the basis of other morphological data, to represent natural groups within the genus. Nevertheless, an arrangement of groups of species of Krameria from “least” to “most” specialized, based on a logical sequence of modification of the pollen morphology, does not agree with any sequence of specialization using other morphological or ecological characters. It is concluded that pollen morphology and ultrastructure has systematic value for intrafamilial groupings of the Krameriaceae but that palynological modifications are incongruous with trends of specializations of other characters and, like many other lines of investigation, pollen studies do not provide significant data as to the phylogenetic affinities of the family.     

Palynotaxonomy of Brazilian species of Polygala subgenus Hebeclada

This study used pollen morphology to address taxonomic controversies related to several species belonging to subgenus Hebeclada of the genus Polygala (Polygalaceae). According to the last traditionally accepted revision of this subgenus, it comprises 40 species. Nevertheless, a recent taxonomic treatment applying more comprehensive criteria reduced this number to only nine species. Our work focused on 15 traditionally accepted species that occur in Brazil, fourteen of which have been considered as only six species in this recent taxonomic study. Pollen grains from floral buds at pre‐anthesis were collected from herbarium specimens and analysed using both visible light and scanning electron microscopy. Most of the traditionally accepted species were distinguished by different combinations of several pollen‐related features, in particular colpi number (13 or 15), pollen size and shape, and endoaperture type (endocingulate or not) and arrangement (parallel or sinuous). The species accepted in the recent taxonomic treatment could not be discriminated by pollen characters. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 609–619.     

Pollen morphology in the family Asphodelaceae (Asphodeleae,Kniphofieae)

Pollen of 72 species from 7 genera of the Asphodelaceae was studied by means of LM and SEM in order to investigate their taxonomic relationships. The pollen of all the genera investigated is heteropolar, monosulcate, non-operculate and differs in size, form and exine ornamentation. The species of Eremurus are homogenous palynologically and studies of this genus do not support the segregation of the genera Henningia, Selonia, and Ammolirion. The pollen of Bulbinopsis mainly differs from the pollen of Bulbine species in having a perforate-areolate exine surface (B. bulbosa) but the genera are close in their other palynological features. The genera Asphodelus and Asphodeline have the largest, almost spheroidal grains with the thickest exine but differ in details of exine ornamentation. The species of Kniphofia are very close palynologically.     

On the pollen morphology of Scyphosyce and Dorstenia (Moraceae)

The pollen grains of the two species of Scyphosyce are alike and show distinct resemblances with those of several species of Dorstenia. Pollenmorphological data confirm the taxonomic suggestion to place Scyphosyce and Dorstenia together in the tribe Dorsteniae.     

Pollen morphology in the genus Coffea (Rubiaceae) and its taxonomic significance

The pollen morphology of 38 representative species and varieties within the genus Coffea L. is described. Eight pollen types, placed in two major groups, have been identified on the basis of the number of colpi, colpus characteristics, exine morphology and pollen size. Differences in pollen structures of the species studied do not correspond to present taxonomic groupings, but support a current proposal to place some of the species in the genus Paracoffea Leroy. Among the four sections in the genus, the section Eucoffea contains a high degree of pollen polymorphism.     

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 diversity in the genus Ptilostemon (Asteraceae,Cardueae) from Italy and its taxonomic and palynoecological implications

The results of a study on pollen morphology of the species of the genus Ptilostemon growing in Italy: Ptilostemon niveus, P. greuteri, P. gnaphaloides, P. casabonae, P. strictus, P. stellatus by light and scanning electron microscopy were presented and discussed including in relation to their taxonomic position. The exine shows two different ornamentation patterns: echinae and scabrae. This last ornamentation pattern together with other features was previously described in the genus Ptilostemon. Of 6 species analysed, P. stellatus is the only one that shows a scabrate ornamentation of exine. Two pollen types were recognized through the exine ornamentation, length of ectocolpus and polar outline: P. stellatus type and P. niveus type. A multivariate analysis (principal component analysis and linear discriminant analysis) was carried out with the aim of examining potential morphological characters which could be used to identify taxa. The data suggest that several characteristics can be used to delimit the species in particular the exine ornamentation. The results of our studies support the actually subgeneric classification, and several features of the pollen grains analysed seem to have a palynoecological role and an important taxonomic significance. A dichotomous key based on palynological data is also given.     

PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. II. GENERA HAITIA THROUGH PEPLIS

Pollen morphology for 12 genera of the Lythraceae is described, using light microscopy (LM), scanning (SEM) and transmission electron microscopy (TEM). The genera surveyed are Haitia, Heimia, Hionanthera, Lafoensia, Lagerstroemia, Lawsonia, Lythrum, Nesaea, Orias (= Lagerstroemia), Pehria, Pemphis, and Peplis. Among results of taxonomic significance are 1) the similarity of pollen between Haitia and Ginoria, suggesting that future classifications reflect a close relationship between these genera, 2) a comparable similarity in pollen between Pehria and Adenaria, 3) the distinction of Hionanthera pollen from that of Ammannia, 4) an exine similar in certain ultrastructural characteristics between Orias and some species of Lagerstroemia, although in general aspect they appear quite different, 5) that within the Didiplis-Lythrum-Peplis complex, there are three palynologically distinct groups, with Didiplis standing apart from the somewhat more similar, but nevertheless, distinct Lythrum and Peplis, and 6) that considerable differences exist between pollen of Pemphis acidula and Pemphis madagascariensis, supporting removal of the latter species to a new genus. This pollen survey is part of a multi-disciplinary effort to clarify generic limits in the Lythraceae, and evaluate relationships within the family and among families of the Myrtales.     

FUNCTIONAL DIOECY AND ANDROMONOECY IN SOLANUM

Field and laboratory studies of 19 diclinous species endemic to Australia help to clarify the nature and evolution of andromonoecy, androdioecy, and dioecy in the genus Solanum. Ten species are andromonoecious; typically these species bear inflorescences with a single, large basal hermaphroditic flower and 12–60 distal, smaller staminate flowers. We suggest that the andromonoecious condition was derived from hermaphroditic-flowered ancestors in part by hemisterilization of flowers but largely by addition of staminate flowers. The resultant larger inflorescences are hypothesized to serve both to attract and to entrain pollinators, yielding more or higher-quality seed set in hermaphroditic flowers and/or greater dispersion of pollen from staminate flowers. We suggest that andromonoecy may also serve to reduce selling. Nine other species are morphologically androdioecious but functionally dioecious. In these species, staminate flowers, like those of the andromonoecious species, bear anthers with copious tricolporate pollen and a highly reduced gynoecium. The morphologically hermaphroditic flowers are functionally pistillate and borne singly in inflorescences, and they bear anthers with inaperturate pollen. The inaperturate pollen, although viable, never germinates and is hypothesized to be retained in pistillate flowers as a reward to pollinators in the nectarless Solanum flowers. All other species of Solanum studied with pollen dimorphism in which one pollen morph is inaperturate are also best treated as functionally dioecious. We conclude that there is no evidence for androdioecy in Solanum. A review of other families suggests that there is little support for this unusual breeding system in any other angiosperm group either. Preliminary analyses suggest that andromonoecy and dioecy are polyphyletic in Solanum. Furthermore, dioecy is as likely to have arisen from hermaphroditic as from andromonoecious ancestors.