New insights into the pollen morphology of the genus Gunnera (Gunneraceae)

Pollen grains from ten species of Gunnera, chosen to represent the six different subgenera in the genus, were examined using light and scanning electron microscopy. The aim of the study was to explore characters that have the potential to define different types of pollen within Gunnera and to study the evolution of these characters in light of the phylogeny of the genus. According to our results, there are three main types of pollen in the examined species of Gunnera. Type 1, unique for the South American species G. herteri (subgenus Ostenigunnera), is characterised by an imperfect reticulum with sinuous undulating-creasted muri. A reticulum with equidimensional polygonal lumina is typical for the plesiomorphic type of pollen (type 2) present in subgenera Gunnera, Misandra and Panke. Lastly, pollen grains of subgenera Pseudogunnera and Milligania are characterised by a reticulum with lumina of variable shape and size (type 3). In G. macrophylla (subgenus Pseudogunnera), the lumina in the apocolpia are of a different shape and size from the lumina in the mesocolpia (type 3a), while in G. dentata, G. monoica and G. cordifolia (subgenus Milligania), the lumina are identical in the apocolpium and the mesocolpium (type 3b).

The identification of pollen types will possibly allow the interpretation of the different specimens of Tricolpites reticulatus, the fossil species believed to be allied to the extant Gunnera.

In addition to the revision on the pollen of Gunnera, a brief comparison between the pollen of this genus and its sister group Myrothamnus is reported.     

Amorphophallus: New insights into pollen morphology and the chemical nature of the pollen wall

In pollen characters, Amorphophallus is one of the most diverse genera in the Araceae. The present work is a critical survey of contradicting reports on the impact of acetolysis treatment on Amorphophallus pollen, on the chemical nature of the outer pollen wall layer and of electron-dense (dark) granules found within it. Furthermore, we wanted to clarify the pollen polarity and to test conclusions based on different preparation techniques. Pollen morphology of 25 species is investigated by light microscopy, scanning electron microscopy and transmission electron microscopy. Our results show that Amorphophallus pollen is not resistant to acetolysis treatment. The use of different transmission electron microscopy staining methods proved the polysaccharide nature of the outer pollen wall layer and of the granules within it. Moreover, an additional thin surface layer was found in all investigated species. Microspores in early and late tetrad stages show that the less convex side of the microspore is the proximal face and the more convex side the distal face. The extrusion of pollen in strands is illustrated for the first time by light microscopy and scanning electron microscopy. Furthermore, observations of pollen in water showed that in some of the investigated species the pollen wall is shed immediately before pollen tube formation.     

Evolution of secondary heads in Nassauviinae (Asteraceae, Mutisieae)

The evolution of the inflorescence head in Asteraceae is important in the diversification of this largest angiosperm family. The aggregation of heads into higher-order capitulescences (secondary heads or syncephalia) is considered evolutionarily advanced. The genera Moscharia, Nassauvia, Polyachyrus, and Triptilion of the subtribe Nassauviinae (Mutisieae) have syncephalia with differing degrees of capitula condensation. ITS and plastid trnL-trnF regions were analyzed separately and together using maximum parsimony and maximum likelihood to examine the evolution of syncephalia in the Nassauviinae. The four genera displaying syncephalia do not form a clade minus taxa without syncephalia, indicating that secondary heads in Nassauviinae have either convergently evolved twice in the subtribe (or, very unlikely) once with multiple reversions. Strong support was obtained for a sister relationship between Leucheria (without syncephalium) and Polyachyrus, and both sister to Moscharia. Nassauvia and Triptilion form a distinct clade but are sister to other genera, Perezia and Panphalea, without syncephalium. Previous hypotheses postulated the evolution from simple to more complex secondary heads. We show that the ancestor of Moscharia, Polyachyrus, and Leucheria, in a more arid habitat, had a complex type of secondary head, and loss of complexity occurred in response to a shift from arid to mesic conditions.     

The infraspecific taxa of Pleiotaxis huillensis (Mutisieae, Asteraceae)

The species from Angola Pleiotaxis huillensis (Mutisieae, Asteraceae) is subdivided into three subspecies and one variety. Specifically, P. huillensis subsp axillaris and P. huillensis subsp. huillensis var. macrocephala are described as new taxa, and a new nomenclatural combination is proposed ( P. huillensis subsp. argentea ).     

A new taxonomic interpretation of the Dicoma anomala complex (Mutisieae, Asteraceae)

The polymorphic African species D. anomala is subdivided in three subspecies and two new nomenclatural combinations in the genus Dicoma (Mutisieae, Asteraceae) are proposed: Dicoma anomala subsp. attenttata and D. anomala subsp. gerrardii .     

New insights into pollen morphology and its implications in the phylogeny of Sanguisorba L. (Rosaceae; Sanguisorbeae)

Pollen morphology of 13 species of the genus Sanguisorba (Rosaceae) was examined by light and scanning electron microscopy. The pollen morphology divided the genus into two main groups: (A) tricolporate with tapered colpus tips, and (B) either tricolporate with opened colpus tip or hexacolporate. The former group was further subdivided into those without vestibulum (A1: S.?alpina, S.?dodecandra, and S.?filiformis) and those with vestibulum (A2: S.?agrimonoides, S.?ancestroides, S.?annua, S.?cretica, S.?minor, and S.?verrucosa), whereas the latter group was subdivided into those with colpus narrow and similar to the A1 type (B1: S.?canadensis and S.?diandra), those with colpus and mesocolpus somewhat equally wide and forming hexacolporate aperture (B3: S.?albiflora, S.?armena, S.?media, S.?menziesii, S.?parviflora, S.?stipulata, and S.?tenuifolia), and those with colpus intermediate between the B1 and B3 types (B2: S.?hakusanensis, S.?microcephala, S.?obtusa, S.?officinalis, S.?polygama, and S.?sitchensis). It is suggested that the A1 type aperture would have evolved to the A2 type as a specialized form and the B types (B1 to B3) in a direction in which the hexacolporate aperture was derived. Implications of pollen morphology for infrageneric classification of Sanguisorba are discussed and the results are compared with molecular phylogenetic studies.     

New chromosome counts in the genus Cousinia and the related genus Schmalhausenia (Asteraceae, Cardueae)

Twenty chromosome counts are reported in the genus Cousinia and the monotypic genus Schmalhausenia , which are part of the Arctium group, from Armenia, Iran, Kazakhstan and Uzbekistan. Twelve are new and eight provide confirmation of scarce or disputable previous data. The correlation between karyological data, pollen type and molecular phylogeny is very close, and on this basis two main groups can be defined. One is the arctioid group, which comprises the genera Arctium and Schmalhausenia , and a small part of the genus Cousinia , with x  = 18. The other is the genus Cousinia s.s. , with a dysploid series ranging from x  = 13–11. Some considerations on the chromosomal evolution in the group are made.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Socety , 2003, 143 , 411–418.     

Flower morphology and pollen germination in the genus Capsella (Brassicaceae)

Evolutive changes in mating systems are often accompanied by changes in flower morphology, such as the reduction in size or even loss of petals, changes in production of volatiles, pollen/ovule ratio, the position between anthers and stigma and the germination time of pollen after pollination. These changes have been merged under the term “selfing syndrome” and often result in new taxonomic species. The evolutionary shift frequently happens parallel within many families and genera, for example within the Brassicaceae family. Within the genus Capsella, which is closely related to the molecular model species pair Arabidopsis lyrata (SI)/A. thaliana (SC), we studied self-incompatible and self-compatible species. SC species C. rubella and C. bursa-pastoris produce in comparison with the SI species C. grandiflora (i) smaller petals as the result of decreased cell division and only less of decreasing cell volume, (ii) less production of pollen in one flower, (iii) show a lesser incision between the two valves of the fruits, in combination with a shorter style, and (iv) have a much quicker fertilization of SC pollen after pollination. Crossing success between the diploid species, between different provenances of the tetraploid C. bursa-pastoris, and between the two diploid species and particular individuals of the self-incompatible C. grandiflora has been proven.     

Phylogeny and evolution of Perezia （Asteraceae： Mutisieae： Nassauviinae）

A molecular phylogenetic analysis of most of the species of Perezia reveals that, as traditionally defined, the genus is not monophyletic with two species more closely related to Nassauvia than to Perezia. In addition, our results show that Burkartia （Perezia） lanigera is related to Acourtia and is the only member of that clade in South America. The remaining species are monophyletic and show a pattern of an early split between a western temperate and an eastern subtropical clade of species. Within the western clade, the phylogeny indicates a pattern of diversification that proceeded from southern, comparatively low-elevation habitats to southern high-elevation habitats, and ultimately into more northern high-elevation habitats. The most derived clades are found in the high central Andes, where significant radiation has occurred.     

A taxonomic revision and pollen morphology of the genus Dendrokingstonia (Annonaceae)

The genus Dendrokingstonia (Annonaceae) is taxonomically revised and palynologically studied. Three species are recognized, one of which, D. gardneri , is described as new to science. One new combination, D. acuminata , is made. The genus occurs from southern Thailand to Peninsular Malaysia and Sumatra. On the basis of macromorphology and pollen characters, it is considered to be related to Monocarpia. Both genera show a combination of macromorphological characters that is rare in the family, i.e. considerably enlarged stigmas, leaves with percurrent tertiary veins, a highly reduced number of carpels per flower and relatively large monocarps with a thick, hard wall. Scanning and transmission electron microscopy show that the pollen grains of Dendrokingstonia and Monocarpia are monosulcate monads with a columellate infratectum and a more or less bulging intine at the sulcus. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 76–90.     

Revision of the genus Clibadium (Asteraceae, Heliantheae)

Clibadium L. (Asteraceae, Heliantheae) is a genus of 29 species distributed throughout latin America, from Mexico to Peru, and in the West Indies, with high numbers of species in Costa Rica, Colombia, and Ecuador.Clibadium includes shrubs and small trees; usually with loosely aggregated capitula; herbaceous phyllaries arranged in 1–5 series; receptacles usually paleaceous throughout; corollas of pistillate florets 2–4-lobed; corollas of the staminate florets 4–5-lobed; purple to black anthers; and chromosome numbers alln=16. Two sections of species previously recognized are here considered as subgenera (subg.Paleata and subg.Clibadium) containing two and four sections, respectively.Clibadium subg.Paleata contains five species distributed in sects.Eggersia (3 spp.) andTrixidium (2 spp.), and subg.Clibadium has 24 species distributed among sects.Clibadium (6 spp.),Glomerata (9 spp.),Grandifolia (5 spp.), andOswalda (4 spp.).     

New chromosome counts in the genus Centaurea (Asteraceae) from Turkey

Twenty‐two chromosome counts are reported in 16 species, four subspecies and two varieties of the genus Centaurea. These are mostly Turkish local endemics of section Cheirolepis, a complicated group from the Eastern clade of the Jacea group. Twenty‐one reports are new. Prevalence of the basic chromosome number x = 9 among the eastern sections of the Jacea group is confirmed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 280–286.     

New chromosome counts in the genus Cousinia (Asteraceae) from Iran

Chromosome counts are reported of 38 populations representing 24 species of the genus Cousinia from Iran, one of the main centres of speciation of the genus. Sixteen of the counts are new to science. Our results confirm that Cousinia exhibits a complex dysploid series ranging from x  = 13 to x  = 9. One of the basic chromosome numbers, x  = 9, is new for the genus and must be confirmed. Some considerations on the correlation between chromosome numbers and section classification are made.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 411–419.     

Comparative pollen morphology of the Iberian species of Pulicaria (Asteraceae, Inuleae, Inulinae) and its taxonomic significance

To better understand the taxonomy of Pulicaria, the pollen wall architecture of the six Iberian species were investigated using light (LM) and scanning electron microscopy (SEM). The exine structure of Pulicaria odora was also investigated using transmission electron microscopy (TEM). Statistical analysis was performed to distinguish taxonomically significant morphometric information from all the measured parameters of pollen grains. It was found that the exine sculpture characters, with special importance paid to the spines, were the most useful of all characters to define Pulicaria pollen types and separate the species. Three pollen types distinguishable through the spines morphology and the inter-spinular sculpture are described: P. microcephala pollen type (incl. P. microcephala), P. vulgaris pollen type (incl. P. vulgaris), and P. dysenterica pollen type (incl. P. dysenterica, P. odora, P. paludosa and P. sicula). A dichotomous key to these Pulicaria pollen types is proposed. The distribution of P. dysenterica, P. odora, P. paludosa and P. sicula in more than one leaf node in the classification tree reveals that the pollen grains of these species are difficult to segregate. Therefore, the construction of a satisfactory dichotomous key to the P. dysenterica pollen type species is not feasible. Yet, the different spines apex morphology between P. microcephala and P. paludosa and the existence of significant differences in five of the eight studied quantitative pollen characters of these two taxa, supports the opinion that the Berlengas Islands endemic P. microcephala should be accepted as a separate species. In addition, the differences among the spines morphology of P. vulgaris, P. microcephala, and the other four Iberian (and European) species, strengthen the conclusion that the section Pulicaria is non-monophyletic.     

Petrodavisia,a new genus inCentaureinae (Asteraceae)

A new monotypic genus based onPtosimopappus bracteatus Boiss. =Centaurea ptosimopappa Hayek is described. The history of its classification and relationships toCheirolophus Cass. andMicrolophus Cass. are discussed.