CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

Polemoniaceae phylogeny and classification: implications of sequence data from the chloroplast gene ndhF

The chloroplast gene ndhF was used to study phylogenetic relationships of the Polemoniaceae at two levels: among members of the Ericales and among genera of the family. Sequence data for interfamilial analyses consisted of 2266 bp for 14 members of the Ericales, including four species of the Polemoniaceae, plus three outgroup taxa. The Polemoniaceae were found to be related to Diospyros, Fouquieria, the Primulales, Rhododendron, and Impatiens, but relationships among taxa were generally not well supported. The precise position of the Polemoniaceae within the Ericales remains obscure. Data for intrafamilial analyses consisted of 1031 bp for 27 species of the Polemoniaceae, including at least one species from most genera of the family, plus five outgroup taxa. A single most parsimonious tree was identified. The analyses suggested that subfamily Cobaeoideae, excluding Loeselia, is monophyletic and that Huthia is sister to Cantua. Acanthogilia was sister to the remainder of subfamily Cobaeoideae. Subfamily Polemonioideae plus Loeselia formed four subclades that were strongly supported as monophyletic and represent the major lineages of the subfamily.     

Monophyly and generic relationships of polemoniaceae based on matK Sequences

Polemoniaceae are often considered a model family for studying evolutionary processes, yet a reliable phylogeny for the family is only now beginning to emerge. To test the monophyly of this family and to elucidate intergeneric relationships, we employed comparative sequencing of the chloroplast gene matK. Parsimony analysis of matK sequences representing 18 genera of Polemoniaceae and nine families from Asteridae sensu lato places Polemoniaceae apart from Solanaceae near Fouquieriaceae, Ericaceae, Sarraceniaceae, and Diapensiaceae. Both this and a subsequent analysis of 59 species of Polemoniaceae indicate that Cobaea is derived from within Polemoniaceae, rather than being the sister to Polemoniaceae as suggested by some authors. The tropical genera Bonplandia, Cantua, and Cobaea form a clade, and the remaining, primarily temperate genera, excluding Acanthogilia, form a second monophyletic group. Acanthogilia is placed ambiguously as sister to either the tropical or temperate groups depending on the location of the root for Polemoniaceae. Within the temperate lineage, Polemonium is sister to three large clades: a well-supported clade comprising Phlox, Gymnosteris, Linanthus, Leptodactylon, and Gilia filiformis; a moderately well-supported clade comprising Allophyllum, Collomia, Navarretia, and several species of Gilia; and a weakly supported clade comprising Eriastrum, Ipomopsis, Langloisia, Loeseliastrum, Loeselia, and several species of Gilia. In addition to revealing the extreme polyphyly of Gilia, this analysis suggests that Ipomopsis and Linanthus are also polyphyletic.     

Plant size,geitonogamy and seed set in Ipomopsis aggregata

Summary We used powdered fluorescent dyes to estimate receipt of self vs. outcross pollen in the self-incompatible species Ipomopsis aggregata (Polemoniaceae). Flowers on small and large plants received equal amounts of outcross pollen, whereas flowers on large plants received more self pollen, so the proportion of self pollen delivered through geitonogamy increased with plant size. In natural populations emasculation of all flowers on a plant raised average seed set per flower from 5.19 to 6.99 and also raised fruit set, though not significantly. From these results one expects a negative correlation between plant size and seeds per flower. The opposite trend was observed in a sample of plants in the field, suggesting that deleterious effects of geitonogamy on female fecundity in large plants can be overruled by other factors such as size-related fruit or seed abortion. Results are discussed in relation to the evolution of gynodioecy.     

Linking pollinator visitation rate and pollen receipt

The majority of flowering plants require animals for pollination, a critical ecosystem service in natural and agricultural systems. However, quantifying useful estimates of pollinator visitation rates can be nearly impossible when pollinator visitation is infrequent. We examined the utility of an indirect measure of pollinator visitation, namely pollen receipt by flowers, using the hummingbird-pollinated plant, Ipomopsis aggregata (Polemoniaceae). Our a priori hypothesis was that increased pollinator visitation should result in increased pollen receipt by stigmas. However, the relationship between pollinator visitation rate and pollen receipt may be misleading if pollen receipt is a function of both the number of pollinator visits and variation in pollinator efficiency at depositing pollen, especially in the context of variable floral morphology. Therefore, we measured floral and plant characters known to be important to pollinator visitation and/or pollen receipt in I. aggregata (corolla length and width and plant height) and used path analysis to dissect and compare the effect of pollinator visitation rate vs. pollinator efficiency on pollen receipt. Of the characters we measured, pollinator visitation rate (number of times plants were visited multiplied by the mean percentage of flowers probed per visit) had the strongest direct positive effect on pollen receipt, explaining 36% of the variation in pollen receipt. Plant height had a direct positive effect on pollinator visitation rate and an indirect positive effect on pollen receipt. Despite the supposition that floral characters would directly affect pollen receipt as a result of changes in pollinator efficiency, corolla length and width only weakly affected pollen receipt. These results suggest a direct positive link between pollinator visitation rate and pollen receipt across naturally varying floral morphology in I. aggregata. Understanding the relationship between pollinator visitation rate and pollen receipt may be of critical importance in systems where pollinator visitation is difficult to quantify.     

Tests of pre- and postpollination barriers to hybridization between sympatric species of Ipomopsis (Polemoniaceae)

The Ipomopsis aggregata species complex (Polemoniaceae) includes species pairs that hybridize readily in nature as well as pairs that meet along contact zones with no apparent hybridization. Artificial hybrids can be made between I. aggregata and I. arizonica, yet morphological intermediates between these two species have not been observed in natural populations. This apparent lack of hybridization is perplexing given that plants of the two species often grow within a few metres of each other and both species have red flowers visited by the same species of hummingbirds. We used trained hummingbirds to examine pollen transfer within and between species. We also hand-pollinated flowers to examine paternal success of heterospecific and conspecific pollen, testing paternity with electrophoretic examination of seeds. Hummingbirds were not simply better at transferring pollen within than between species. Instead, I. arizonica was a better pollen donor so that considerable pollen transfer was observed from I. arizonica to I. aggregata, but very little in the opposite direction. Conversely, once pollen arrived at stigmas, I. arizonica pollen performed very poorly on I. aggregata pistils. However, pollen from I. aggregata could, in some cases, sire seeds on I. arizonica. We hypothesize that hybrids are scarce in nature, in part, because of asymmetric barriers to reproduction: little pollen transfer in one direction and poor pollen performance in the other.     

Nuclear and cpDNA sequences combined provide strong inference of higher phylogenetic relationships in the phlox family (Polemoniaceae)

Members of the phlox family (Polemoniaceae) serve as useful models for studying various evolutionary and biological processes. Despite its biological importance, no family-wide phylogenetic estimate based on multiple DNA regions with complete generic sampling is available. Here, we analyze one nuclear and five chloroplast DNA sequence regions (nuclear ITS, chloroplast matK, trnL intron plus trnL-trnF intergeneric spacer, and the trnS-trnG, trnD-trnT, and psbM-trnD intergenic spacers) using parsimony and Bayesian methods, as well as assessments of congruence and long branch attraction, to explore phylogenetic relationships among 84 ingroup species representing all currently recognized Polemoniaceae genera. Relationships inferred from the ITS and concatenated chloroplast regions are similar overall. A combined analysis provides strong support for the monophyly of Polemoniaceae and subfamilies Acanthogilioideae, Cobaeoideae, and Polemonioideae. Relationships among subfamilies, and thus for the precise root of Polemoniaceae, remain poorly supported. Within the largest subfamily, Polemonioideae, four clades corresponding to tribes Polemonieae, Phlocideae, Gilieae, and Loeselieae receive strong support. The monogeneric Polemonieae appears sister to Phlocideae. Relationships within Polemonieae, Phlocideae, and Gilieae are mostly consistent between analyses and data permutations. Many relationships within Loeselieae remain uncertain. Overall, inferred phylogenetic relationships support a higher-level classification for Polemoniaceae proposed in 2000.     

The conserved nature and taxonomic utility of pollen morphology in Cantua (Polemoniaceae)

Pollen exine morphology of nine of the ten species of Cantua (Polemoniaceae) is examined using light and scanning electron microscopy. A total of 28 specimens of C. bicolor, C. buxifolia, C. candelilla, C. cuzcoensis, C. flexuosa, C. pyrifolia, C. quercifolia, C. volcanica, and an as yet undescribed species (Cantua sp. nov.) are examined using either fresh or herbarium material. Pollen grains are found to be spheroidal, pantoporate, and quite large; mean diameter varies from 62 to 87?μm. Mean number of pores varies from 4.5 to 21.2 and mean pore size varies from 4.86 to 12.40?μm. Pollen grains of all species have insulate semitectate sexines. This feature distinguishes the pollen of Cantua species from the remainder of the Polemoniaceae. Insulae are evenly distributed over the surface of the pollen grain, with the exception of C. flexuosa and occasionally C. buxifolia, where insulae are more sparsely and haphazardly distributed. The majority of the species examined have irregularly shaped tectal insulae, with the exception of the large rounded insulae in C. quercifolia and the elongated narrow insulae in C. volcanica. Cantua quercifolia and C. volcanica have supratectal verrucae, a possible synapomorphy. In comparison to close relatives, the pollen grains of Cantua are evolutionarily conserved, and show little variation among species.     

VARIATION IN POLLEN FLOW WITHIN AND AMONG POPULATIONS OF IPOMOPSIS AGGREGATA

Pollen dispersal is a major component of gene flow in plant populations. It can influence microevolution within and among populations as well as the evolution of floral characters that affect dispersal. Most previous studies have relied on point estimates to characterize dispersal distances, even though there is likely to be substantial intrapopulational and interpopulational variation. We measured variation in pollen dispersal for the hummingbird-pollinated herb Ipomopsis aggregata (Polemoniaceae), using powdered fluorescent dyes to estimate pollen movement. Analysis of 5–6 natural populations in each of three years indicated that mean and mean squared distances of pollen dispersal, measured over the reproductive lifespan of individual plants, varied more than threefold among populations and years. Dispersal distances also shifted over the season within a given population. Unlike the variation among populations, these seasonal changes were associated in part with changes in flower density. The mean distance of pollen dispersal from an individual plant was unrelated to the date of first flowering, but did reflect two floral characters. Plants with higher variance in stamen length across flowers delivered pollen farther on average, as predicted by computer simulations of pollen carryover. Plants with lower mean stamen lengths also delivered pollen farther. Such effects of plant characters on pollen dispersal are a critical prerequisite for dispersal to evolve in response to its effects on fitness.     

中国柽柳科（Tamaricaceae）花粉形态研究及其分类意义的探讨

研究观察了中国柽柳科（Tamaricaceae)4属27种植物的花粉形态。中国柽柳科植物花粉为三沟类型,无三拟孔沟类型,形态及外壁雕纹属间差异明显。根据花粉资料,探讨了属间的进化关系和分类地位及本科植物花粉外壁的演化途径。     

单性木兰花粉壁超微结构的研究

本文首次报道单性木兰花粉的形态特征和外壁超微结构。花粉外部形态与木兰科各属特征一致,表明单性木兰花粉的原始性。但花粉外壁超微结构显示其外壁表面具皱波状纹饰;覆盖层波浪状,具稀疏的小穿孔;柱状层很薄,小柱典型,直立,短而细。外壁超微结构表明单性木兰属在木兰亚族中是一个较进化的属。扫描电镜和透射电镜资料揭示出单性木兰在植物分类系统中的特殊地位和重要学术价值。     

Studies on the Pollen Morphology of the Chinese Palmae

This paper deals with morphology of the recent pollen grains of 26 species representing 16 genera and some fossil pollen of the Chinese Palmae. They are examined with the light microscope and scanning electron microscope. On the basis of the types of aperture and the distribution of fossil pollen and lithophyll in the strata, the trends of the evolution of the family Palmae are discussed. This paper points out that the monosulcate pollen belongs to the most predominent and more primitive aperture type in this family and that there is a trend in which the trichotomosulcate, annulocolpate, disulcate etc. are derived from the monosulcate pollen.     

Pollen morphology and phylogenetic analysis of Eperua Aublet (Detarieae: Caesalpinioideae: Leguminosae)

The diverse pollen morphology of fourteen species of the genus Eperua is described and illustrated using light, scanning electron and transmission electron microscopy. Six pollen types are described and a key for their identification is provided. A cladistic analysis was carried out using macromorphological and palynological characters to form a hypothesis of relationships between taxa. The pollen morphology is discussed with regard to systematic relationships, function and phylogenetic significance of certain pollen morphological structures within the genus.     

The systematic value of pollen morphology in Smilacaceae

Smilacaceae are a small family of dioecious, mostly climbing, net-veined monocotyledons with a cosmopolitan distribution. Relatively little is known about the variation of pollen morphology within the family. For this reason, and to investigate the systematic value of palynology in Smilacaceae, pollen from 125 species of Smilax, Heterosmilax, and Ripogonum was examined using light and scanning electron microscopy. Ten of these were examined further by transmission electron microscopy. Four distinct pollen types grouped into two major pollen classes were distinguished: Class 1, represented by the pollen of all Smilax and Heterosmilax species, is mostly spheroidal, inaperturate, and spinulate or microspinulate, with a thin, fragile exine of varied sculpturing; three pollen types are represented within this class. Class 2 is found only in Ripogonum and contains a single pollen type with prolate, monosulcate, reticulately-sculptured pollen. The unique pollen morphology of Ripogonum supports its removal from Smilacaceae. In contrast, the characteristics of Heterosmilax pollen intergrade with those seen in Smilax, suggesting that the former might be better reduced to synonymy with the latter. A key to the identification of these pollen types is presented along with a discussion of geographic and possible evolutionary trends among them.     

Palynological characters and their phylogenetic signal in Rubiaceae

In the 1990s Rubiaceae became a hot spot for systematists, mainly due to the comprehensive treatment of the family by Robbrecht in 1988. Next to the exploration of macromolecular characters to infer the phylogeny, the palynology of Rubiaceae finally received the attention it deserves. This article aims to present a state-of-the-art analysis of the systematic palynology of the family. The range of varíation in pollen morphology is wide, and some of the pollen features are not known from other angiosperm taxa; e.g., a looplike or spiral pattern for the position of apertures in pantoaperturate grains. We compiled an online database at the generic level for the major pollen characters and orbicule presence in Rubiaceae. An overview of the variation is presented here and illustrated per character: dispersal unit, pollen size and shape, aperture number, position and type, sexine ornamentation, nexine pattern, and stratification of the sporoderm. The presence/absence and morphological variation of orbicules at the generic level is provided as well. The systematic usefulness of pollen morphology in Rubiaceae is discussed at the (sub)family, tribal, generic, and infraspecific levels, using up-to-date evolutionary hypotheses for the different lineages in the family. The problems and opportunities of coding pollen characters for cladistic analyses are also treated.     

我国罂粟科(Papaveraceae)植物的花粉形态

本文用光学显微镜对我国16属60种5变种罂粟科植物花粉形态进行了系统地观察研究。其中对15属27种进行了扫描观察。本科花粉形态为多类型。3沟为原始的、基本的花粉类型。根据萌发孔的形状、数目和特征,将罂粟科的花粉分为2沟,3沟,4-6沟、散沟、散孔和无萌发孔6个花粉类型。根据孢粉学资料,本文对绿绒蒿属(Meconopsis Vig.)花粉粒和其它器官的进化趋势,罂粟科在进化上的亲缘关系和本科花粉萌发孔的演化趋向等问题进行了讨论。