Similar Pollen Research Articles

Fine structure of Rossipollis reticulatus from the Upper Cretaceous of southern Sweden

Dispersed monosulcate pollen identified as Rossipollis reticulatus Ross and similar pollen in two pollen sacs from a single anther were recovered from Upper Cretaceous fluvial sediments in southern Sweden. In most pollen grains the wall consists of a foot layer, an inner solid reticulum, crowned by columellae, which appear as an infratectal reticulum, and a tectum with irregularly spaced fine perforations. An additional papillate innermost layer, interpreted as a transitory endexin, is present in some pollen grains. A monocotyledonous origin is indicated by the configuration of exine and aperture along with the presence of papillate endexine structures in grains considered to have aborted at earlier stages of development.Key words: Cretaceous, fossil pollen, endexine, monocots.

Pollen morphology, exine structure and systematics of Acalyphoideae (Euphorbiaceae), Part 4 : Tribes Acalypheae pro parte ( Erythrococca, Claoxylon, Claoxylopsis, Mareya, Mareyopsis, Discoclaoxylon, Micrococca, Amyrea, Lobanilia, Mallotus, Deuteromallotus, Cordemoya, Cococceras, Trewia, Neotrewia, Rockinghamia, Octospermum, Acalypha, Lasiococca, Spathiostemon, Homonoia), Plukenetieae ( Haematostemon, Astrococcus, Angostyles, Romanoa, Eleutherostigma, Plukenetia, Vigia, Cnesmone, Megistostigma, Sphaerostylis, Tragiella, Platygyna, Tragia, Acidoton, Pachystylidium, Dalechampia), Omphaleae ( Omphalea), and

This is the fourth, last and largest installment of a palynological study of the Acalyphoideae that examined in light, scanning electron and transmission electron microscopy, the pollen of a grand total of 460 collections representing 372 species from 112 of the 116 assigned genera. Part 4 describes the pollen of tribe Acalypheae pro parte, subtribes Claoxylinae ( Erythrococca, Claoxylon, Claoxylopsis, Mareya, Mareyopsis, Discoclaoxylon, Micrococca, Amyrea), Lobaniliinae ( Lobanilia), Rottlerinae ( Mallotus, Deuteromallotus, Cordemoya, Cococceras, Trewia, Neotrewia, Rockinghamia, Octospermum), Acalyphinae ( Acalypha), Lasiococcinae ( Lasiococca, Spathiostemon, Homonoia), tribe Plukenetieae, subtribe Plukenetiinae ( Haematostemon, Astrococcus, Angostyles, Romanoa, Eleutherostigma, Plukenetia, Vigia); subtribe Tragiinae ( Cnesmone, Megistostigma, Sphaerostylis, Tragiella, Platygyna, Tragia, Acidoton, ( Pachystylidium); subtribe Dalechampiinae ( Dalechampia) and tribe Omphaleae ( Omphalea). None of the above multigeneric tribes or subtribes have uniform morphology or exine structure, but, with the notable exception of Plukenetieae, neither do they have any genera with outstanding palynological distinctions. Most members of Cloaxylinae have pollen of a generalized type, although the data support the separation of Mareyopsis from Mareya. Pollen of Amyrea is distinguished by a striate sculpture. Pollen of Mallotus is uniform and representative of the subtribe Rottlerinae: punctate-microspinulose tecta, thin foot layers, small columellae and thick continuous tecta. Pollen of Acalypha is small, brevicolp(or)ate, and mostly angulaperturate in polar view. One genus of subtribe Lasiococcinae, Spathiostemon, has a supratectal sculpture of lirae with cross striations, while a second, Homonoia, has a tectum composed of elongate, vertically oriented individual rods with acute tips. The exine structure of the large tribe Plukenetieae is strikingly diverse with most variants unique in the Acalyphoideae if not the family. Pollen of most members of Plukenetiinae is of either the Conophora type (punctate tecta, prominent columellae, and granular area under the tectum) or the Loretensis type (reticulate exines, crenate muri, unremarkable structure). Pollen of subtribe Tragiinae is more diverse than Plukenetiinae. Three Asian genera, Cnesmone, Megistostigma and Pachystylidium, have poorly defined apertures, and reduced exines. Inaperturate pollen is present in Platygyna, two species of Acidoton and Tragia sellowiana, all of which have exines consisting mostly of columellae. Three pollen types are recognized in Tragia: (1) the Ramosa type is three-colpate, intectate, and has exines of large columellae and thick foot layers; (2) the Lukafuensis type is three-colpate and has reticulate exines with arched colpal margins at the equator; (3) the Urens type has poorly defined apertures, is tectate with exines lacking foot layers. Pollen of Tragiella is very similar to the Lukafuensis type of Tragia. The large grains of the monogeneric subtribe Dalechampiinae are characterized by two prominent equatorial bands (costae). In Plukenetieae, the pollen data support: the reduction of three monotypic genera, Eleutherostigma, Romanoa and Vigia to species of Plukenetia; a close relationship among Cnesmone, Megistostigma and Pachystylidium; a congeneric treatment of Platygyna and Acidoton microphyllus and A. urens, or at least the restriction of Acidoton to these two species; separate generic status for Tragia sect. Tragia which has the Ramosa pollen type; a congeneric treatment of Tragiella and those species of Tragia ( T. sect. Tagira) with the Lukafuensis pollen type; separate tribal status for Dalechampia. Pollen of Omphaleae is three-colpate, has irregular columellae and foot layers, and a non-apertural endexine that, after acetolysis, separates from the ectexine like the aperturate pollen of Crotonoideae. The results of the pollen study of the entire Acalyphoideae are discussed and Parts 1, 2 and 3 are summarized. Of the multigeneric tribes and subtribes, there are significant pollen differences among the taxa of Ampereae, of Chrozophoreae (subtribe Ditaxinae), of Pycnocomeae (subtribe Pycnocominae), and of Adelieae, as well as taxa of Plukenetieae. The nearly identical pollen of Ricininae and Adrianinae would support their treatment as one subtribe. The subtribes Mercurialinae and Dysopsidinae share similar pollen that is sufficiently distinct from the remaining Acalypheae to merit their treatment as one subtribe. Most pollen of Acalyphoideae is three-colporate with a lalongate endoaperture and punctate-microspinulose or punctate sculpture. Most exines consist of thin foot layers, modest columellae and continuous, mostly thick tecta.

Canopy structure and pollination biology of the seagrasses Posidonia australis and P. sinuosa (Posidoneaceae)

The canopy structure and reproductive phenology of the seagrasses Posidonia australis Hook. f. and Posidonia sinuosa Cambridge and Kuo were studied at Warnbro Sound, near Perth, Western Australia. Canopy and inflorescence height, shoot density, leaf area, leaf biomass, inflorescence density and density of other reproductive units were obtained from six (0.04 m 2) cores of each of the species. Leaf area and biomass were divided into 5 cm height classes and constructed into an in situ canopy profile. Vegetative shoot density was 913±45 shoots m −2 in the P. australis canopy and 1.475±140 shoots m −2 in the P. sinuosa canopy. Total leaf area index of the P. australis canopy (4.1±0.1 m 2 m −2) was less than that of the P. sinuosa canopy (7.0±0.2 m 2 m −2). There were fewer flowers in the P. sinuosa canopy (10±2 flowers m −2) than in the P. australis canopy (16±2 flowers m −2). Mean inflorescence length was 36.5±1.2 cm in the P. australis canopy and 13.4±4.7 cm in the P. sinuosa canopy. Leaf area index at flower height was significantly higher in the P. sinuosa canopy (0.70±0.07 m 2 m −2) than the P. australis canopy (0.25±0.02 m 2 m −2). Reproductive phenology was studied from surveys of tagged inflorescence in situ. Anther dehiscence in P. australis canopy occurred from mid August to mid September and in the P. sinuosa canopy from early to late September. Pollen/ovule ratios of P. australis were similar to that of P. sinuosa. Pollen viability was longer in P. australis than in P. sinuosa. The similar pollen production but low leaf area around flowers, longer pollination period of P. australis flowers result in greater pollination success than for P. sinuosa flowers.

Effects of Dry Tropical Forest Fragmentation on the Reproductive Success and Genetic Structure of the Tree Samanea saman.

Tropical trees are particularly vulnerable to forest fragmentation because of their low densities, self-incompatibilty system, and high rates of outbreeding. Forest fragmentation is likely to decrease gene flow, increase endogamy, and eventually produce a high differentiation among remnant populations. Our objectives were to evaluate the effect of forest fragmentation on the reproductive success, progeny vigor, and genetic variation of the tropical dry-forest tree Samanea saman. We conducted our study in the dry forest of Costa Rica and compared two tree conditions to evaluate forest fragmentation: (1) isolated, individual trees more than 500 m from the nearest conspecific and surrounded by agricultural fields, pastures, or small remnant forest patches and (2) trees in continuous populations of 10 or more individuals per hectare and surrounded by undisturbed forest. We compared the probability of natural pollination, seed production, genetic variation, and progeny vigor of trees in isolation and in continuous populations. The probability of flowers receiving more than 23 pollen tubes at the base of styles (the flowers more likely to produce a mature fruit) was significantly greater for trees in continuous populations (2.1%) than for trees in isolation (0.4%). However, flowers from the two tree conditions received similar pollen loads on their stigmas. Fruits of trees from continuous populations produced similar numbers of seeds as isolated trees did and had a similar probability of seed abortion. The probability of seed predation by bruchid beetles was significantly greater in continuous populations (30%) than in isolated trees (20%). The number of undamaged seeds ( potentially viable) was similar for both tree conditions. A genetic analysis of progeny showed that levels of genetic diversity in trees in isolation and in continuous populations were comparable. The effective self-fertilization rate and inbreeding coefficient of the progeny were slightly higher for isolated trees than for trees in continuous populations. In addition, there was more genetic similarity in the progeny of isolated trees, within and between fruits. Seeds produced by different fruits within a tree were more likely to be related in an isolated tree than in a tree from continuous populations. Seeds produced by trees from continuous populations were more likely to germinate and to produce greater leaf area and biomass as seedlings than progeny from isolated trees. We concluded that the fragmentation of tropical dry forests affects the genetic variation and vigor of S. saman progeny. Isolated trees showed high reproductive capacity, however, in spite of their habitat condition.

A comparison of Betula pollen seasons at two European sites; Derby, United Kingdom and Poznan, Poland (1995–1999).

A comparison of Betula pollen, animportant European aeroallergen, was undertakenat two sites of similar latitude, Derby, UnitedKingdom and Poznan, Poland from 1995–1999. Bothsites routinely monitor Betula pollenusing a Burkard continuous volumetric sampler.Daily and two-hourly March–June Betulapollen counts per cubic metre of air werestudied at both sites, together withcorresponding meteorological data. Detailedanalysis was undertaken to compare start dates,duration and quantity of Betula pollen.Derby usually had an earlier start of seasonthan Poznan, and both cities showed very littledifference between start dates determined byusing the SUM 75 or 2.5% method. The longestseasonal durations at Derby and Poznan yieldedthe lowest seasonal pollen indexes. Every yearfrom 1995–1999 the Betula seasonal pollenindex was higher in Poznan than in Derby. Poznanhad more daily counts of Betula pollengrains per cubic metre above 500, and at leastone daily count of 1000, each year. At bothsites the yearly seasonal variation correlatedwith the number of April days per year having amaximum temperature of 17 °C or above.There was a similar diurnal periodicity ofApril Betula pollen in Derby and Poznan.Although the two cities, at approximately thesame latitude, have different regional andmeteorological characteristics, the weatherappears to influence Betula pollenseasons in a similar manner. Local clinicianscould use the SUM 75 method as indicative ofthe start of the Betula pollen season atboth sites.

Development of a semi-automatic system for pollen recognition

A semi-automatic system for pollen recognition is studied for the european project ASTHMA. The goal of such a system is to provide accurate pollen concentration measurements. This information can be used as well by the palynologists, the clinicians or a forecast system to predict pollen dispersion. At first, our emphasis has been put on Cupressaceae, Olea, Poaceae and Urticaceae pollen types. The system is composed of two modules: pollen grain extraction and pollen grain recognition. In the first module, the pollen grains are observed in light microscopy and are extracted automatically from a pollen slide coloured with fuchsin and digitized in 3D. In the second module, the pollen grain is analyzed for recognition. To accomplish the recognition, it is necessary to work on 3D images and to use detailed palynological knowledge. This knowledge describes the pollen types according to their main visible characteristerics and to those which are important for recognition. Some pollen structures are identified like the pore with annulus in Poaceae, the reticulum in Olea and similar pollen types or the cytoplasm in Cupressaceae. The preliminary results show the recognition of some pollen types, like Urticaceae or Poaceae or some groups of pollen types, like reticulate group.

Phylogeny of Stephanomeria and related genera (compositae–lactuceae) based on analysis of 18S–26S nuclear rDNA ITS and ETS sequences

A phylogenetic analysis of DNA sequences from the internal transcribed spacer (ITS), the external transcribed spacer (ETS), and the 5.8S regions of 18S-26S nuclear rDNA from all diploid species of Stephanomeria and related genera shows that Stephanomeria does not include either Munzothamnus blairii (previously S. blairii) or Pleiacanthus spinosus (previously S. spinosa). Without these two taxa, Stephanomeria is a well-supported (100% bootstrap), monophyletic group of ten perennial and six annual species. Munzothamnus blairii and Pleiacanthus spinosus, both now considered members of monotypic genera, had been placed in Stephanomeria primarily because they have the same chromosome number as Stephanomeria and similar pollen surface features, but many disparities were ignored in previous classifications. Within Stephanomeria, an unsuspected sister relationship was detected between the montane S. lactucina and coastal S. cichoriacea. A second clade contained all the annual taxa and five of the perennial species. Among the annuals, strong bootstrap support was obtained for the previously recognized relationships between S. diegensis and S. exigua (98%) and between S. malheurensis and its progenitor, S. exigua subsp. coronaria (96%). Among the five perennial species that constitute a clade with the annuals, the recently described S. fluminea was shown to be sister to S. runcinata, and both of them were closely allied to S. tenuifolia and S. thurberi. The clade including the annuals (and five of the perennial species) was subtended by perennial lineages and pairwise divergence values among the annual taxa were much lower than among the perennial taxa as a group (though not too different than among the perennials in the same clade). The annuals probably originated recently within the genus.

A Comparison of Floral Structures of Anisophylleaceae and Cunoniaceae and the Problem of their Systematic Position

Flowers of Anisophyllea(Anisophylleaceae, Cucurbitales) andCeratopetalum (Cunoniaceae, Oxalidales) are surprisingly similar in appearance. To date, these families have never been interpreted as closely related, and even in present molecular (rbcL) studies they appear in different orders of eurosids I (APG, Annals of the Missouri Botanical Garden85:531–553, 1998). In this investigation, flowers of selected taxa of both families are morphologically and anatomically compared. In addition, previous work on the two families is reviewed. The results strongly emphasize the great similarity in all floral organs. Some special similarities include the occurrence of trimerous flowers, isomerous organ whorls (including the gynoecium), valvate sepals, digitate petals, obdiplostemony, incurved filaments in bud with similar anthers, similar pollen, similar nectaries, carpels with free styles, a canal in the centre of each individual carpel as well as in the centre of the entire gynoecium along the symplicate zone, and similar ovules with a slit-shaped micropyle. In addition, recently recovered Late Cretaceous floral fossils that share features of both families further emphasize a potential close relationship. However, if more extensive molecular studies are performed in the future that support the current disparate position of the two families, then an explanation of the biological/functional similarities in floral structure should be attempted: specifically, whether this suite of features is a symplesiomorphy for basal rosids, or an autapomorphy for each family.

Palynology of the perigoniate Aroideae: Zamioculcas, Gonatopus and Stylochaeton (Araceae)

The pollen of the perigoniate Aroideae sensu Mayo et al. (1997) ( Zamioculcas Schott, Gonatopus Hook. f. ex Engl. and Stylochaeton Lepr.) differs ultrastructurally from that of the aperigoniate Aroideae in several important exine and aperture characters. The almost identical zona-aperturate pollen of Zamioculcas and Gonatopus has outside the aperture an elaborated, thick ectexine, while the aperture consists of a thin, but continuous ectexine and a thick, lamellate endexine. In contrast, the omniaperturate pollen of Stylochaeton has a thin, not clearly stratified ectexine and a thin, heterogeneous endexine below. However, the zona-aperturate pollen of Zamioculcas and Gonatopus deviates significantly from the superficially similar zona-aperturate pollen of the unrelated Monstereae (e. g., Monstera Adans., Amydrium Schott): in the apertures of Monstera or Amydrium both the thin, but continuous ectexine and the lamellate endexine, which are typical features for Zamioculcas and Gonatopus , are absent. The palynological data underline not only the present classification of Zamioculcas , Gonatopus and of Stylochaeton into two tribes (Zamioculcadeae and Stylochaetoneae) and the differences of both tribes from the other Aroideae, but show also significant deviations in the respective zona-aperturate condition in Monstereae (Monsteroideae) and Zamioculcadeae (Aroideae).

Stratigraphic significance of some angiosperm pollen from the Tinali Oilfield, Upper Assam, India

Twelve fossil pollen taxa Polygonacidites frequens, Perfotricolpites neyvelii, Lanagiopollis eocaenicus, Tiliaepollenites cf. rotundus. Tiliaepollenites sp. A. Durgaipollenites galsii, Strobilanthidites cf. africanus, Retitrescolpites africanus, Retitricolporites cf. guianensis, Corsinipollenites jussiaeensis, Discoidites borneensis and tinalipollenites duttae gen. et sp. nov. are described from the Barail Group to Dhekiajuli Formation (mid Tertiary to Quatenary) of the subsurface Tinali area. Upper Assam. The fossil pollens are compared with similar pollen types from extant dicotyledonous species. The geological record and stratigraphic and palaeoecologic significance of the fossil forms are considered in relation to the geographic distribution and habitat of modem taxa with similar pollen.

Androdioecy in the entomophilous tree Fraxinus ornus (Oleaceae)

Androdioecy (the coexistence of two genders, cosexuals and males, in a single population) is a rare breeding system. In terms of functional gamete production, androdioecy has been reported in a small number of wind‐pollinated and insect‐pollinated species. In this study we examine the floral biology, stability of gender, and fruit and seed production after self‐pollination and outcrossing pollination in a potentially androdioecious tree, Fraxinus ornus, in southern France. Individual trees have either hermaphrodite flowers or male flowers, the latter lacking a well‐developed gynoecium. The two genders produce morphologically similar pollen and were present in 1∶1 or slightly male‐biased ratios. Only hermaphrodites set fruit during 2–4 yr of observation at four different sites in southern France. Experimental pollinations of eight trees in two different sites showed that hermaphrodites produce viable pollen in dehiscent anthers and viable seeds. Thus, in terms of functional gamete production, F. ornus is a new case of functional androdioecy. Seven hermaphrodites were self‐compatible, and such self‐compatibility of hermaphrodites might improve the colonizing ability of F. ornus in a region where this species is actively expanding its range.

Calibrating Late Quaternary terrestrial climate signals: radiometrically dated pollen evidence from the southern Sierra Nevada, USA

We constructed a radiometrically calibrated proxy record of Late Pleistocene and Holocene climate change exceeding 230,000yr duration, using pollen profiles from two cores taken through age-equivalent dry lakes—one core having greater age control (via 230Th alpha mass-spectrometry) and the other having greater stratigraphic completeness. The better dated of these two serial pollen records (Searles Lake) served as a reference section for improving the effective radiometric age control in a nearby and more complete pollen record (Owens Lake) because they: (1) are situated ∼90km apart in the same drainage system (on, and immediately leeward of, the eastern flank of the Sierra Nevada), and (2) preserved strikingly similar pollen profiles and concordant sequences of sedimentological changes. Pollen assemblages from both lakes are well preserved and diverse, and document serial changes in Late Pleistocene and Holocene plant zone distribution and composition in the westernmost Great Basin; they consist of taxa now inhabiting montane forest, woodland, steppe, and desert-scrub environments. The studied core intervals are interpreted here to be the terrestrial equivalent of marine δ18O stages 1 through 9; these pollen profiles now appear to be among the best radiometrically dated Late Pleistocene records of terrestrial climate change known.

Pollen morphology, exine structure and systematics of Acalyphoideae (Euphorbiaceae): Part 2. Tribes Agrostistachydeae ( Agrostistachys, Pseudagrostistachys, Cyttaranthus, Chondrostylis), Chrozophoreae ( Speranskia, Caperonia, Philyra, Ditaxis, Argythamnia, Chiropetalum, Doryxylon, Sumbaviopsis, Thyrsanthera, Melanolepis, Chrozophora), Caryodendreae ( Caryodendron, Discoglypremna, Alchorneopsis), Bernardieae ( Bernardia, Necepsia, Paranecepsia, Discocleidion, Adenophaedra) and Pycnocomeae ( Pycnocoma, Droceloncia, Argomuellera, Blumeodendron, Podadenia, Ptychopyxis, Botryophora)

This is the second paper of an extensive study of pollen morphology and exine structure of Acalyphoideae (Euphorbiaceae) following the most recent system of Webster. Part 2 describes the pollen of 30 genera assigned to tribes Agrostistachydeae, Chrozophoreae, Caryodendreae, Bernardieae and Pycnocomeae. In Agrostistachydeae, members of Agrostistachys and Pseudagrostistachys have similar but unspecialized pollen; grains of Cyttaranthus have weakly suprareticulate tecta of widely varying thickness and small densely spaced columellae; pollen of Chondrostylis has a croton sculpture and precisely defined bridges of ectexine over the endoaperture. Of the 11 genera assigned to tribe Chrozophoreae, pollen of Caperonia has prominent opercula, thick exines and punctate tecta, pollen of Ditaxis and Argythamnia is colpate, has large columellae, and the unevenly thick and complete tecta associated with suprareticulate sculpture or derivations thereof, and pollen of Chiropetalum has operculate apertures, diminutive columellae, and an incomplete finely reticulate tectum, characteristics which argue against a supposedly close relationship to Ditaxis and Argythamnia. Three of the four genera assigned to subtribe Doryxylinae, Doryxylon, Sumbaviopsis, and Melanolepis have similar pollen — thin exines with irregular foot layers, and irregular short columellae, whereas pollen of the fourth genus, Thyrsanthera, has thicker exines with a well-defined foot layer and more elongate columellae. The eight examined species of Chrozophora have 6–9 aperturate pollen and robust exines; two species have punctate tecta and zonorate endoapertures; the remaining species have heterobrochate tecta and lolongate endoapertures. The three genera comprising Caryodendreae, Caryodendron, Discoglypremna and Alchorneopsis, have small 3-colporate pollen with punctate tecta. Pollen of the five genera assigned to tribe Bernardieae, Bernardia, Necepsia, Paranecepsia, Discocleidion and Adenophaedra is of a similar, but unspecialized type — a punctate, deeply punctate, or microreticulate tectum, small endoaperture, and usually a prominent margo. The present concept of tribe Pycnocomeae as comprising Pycnocoma, Droceloncia, Argomuellera, Blumeodendron, Podadenia, Ptychopyxis and Botryophora is not supported by the pollen data. Members of Pycnocoma have pollen with a derived exine structure — a conspicuously thick endexine throughout the grain, threadlike foot layers, and columellae reduced to a point on the proximal side of the tectal elements. The pollen data are somewhat ambiguous about a close relationship between Droceloncia and Argomuellera, the two remaining genera in the subtribe Pycnocominae. The genera allied as subtribe Blumeodendrinae, Blumeodendron, Podadenia, Ptychopyxis, and Botryophora, share pollen with short narrow colpi, a croton sculpture, and mostly irregular columellae.

Comparison of different treatments for LM and SEM studies and systematic value of pollen grains in Cyperaceae

The pollen grain morphology of 30 species of 27 genera from the four subfamilies of the Cyperaceae have been studied with LM and SEM. Several methods were tested in order to find the optimal treatment for the delicate Cyperaceae pollen grains. For LM, treatment with wetting agent Agepon and KOH yielded the best results, while critical point drying (CPD) after fixation with alcohol proved to be the best method for studying pollen grains of Cyperaceae with SEM. Our results show that the Mapanioideae have a pollen grain type (only one distal ulcus) clearly different from the other Cyperaceae. Representatives of the examined Sclerioideae and Caricoideae show a similar pollen grain type (mostly one distal ulcus and three lateral pores) while in the Cyperoideae different pollen grain types are found.

Interpreting pollen diagrams from wetlands: pollen representation in surface samples from Oil Well Bog, southern Ontario

Pollen and spore analysis of surface sediment samples from 45 points within Oil Well Bog, a coniferous swamp near Cambridge, Ontario, was used to determine the possibility of identifying different wetland vegetation communities from their palynological record, and to assess the effects of variable wetland vegetation on the pollen representation of surrounding upland communities. The data obtained were mapped for individual taxa to allow direct comparison of the spatial patterns of vegetation abundance and the associated palynological assemblages, and cluster analysis was used to identify palynologically similar assemblages. Some wetland communities, such as swamp dominated by black spruce, do have distinctive pollen signatures, but not all the vegetational diversity observed is reflected in the palynological data, with similar pollen assemblages deriving from some communities which are vegetationally very different (e.g., shrub swamps dominated by Chamaedaphne calyculata and Ilex verticillata). The wetland pollen assemblages do reflect much of the floristic diversity of the surrounding uplands, although the different communities receive varying proportions of their pollen influx from upland sources (varying from less than 5% to over 90%), and wide variations in the percentage of a given upland pollen morphotype can be found within quite a short distance, depending on the nature of local wetland communities.Key words: palynology, swamp, surface samples, wetland.

Herb pollen representation in surface moss samples from mown meadows and pastures in western Norway

Grazed and mown vegetation types in western Norway were investigated with the aim of describing their modern pollen/vegetation relationships as an aid to the interpretation of fossil pollen diagrams. Pollen surface samples and vegetation data were obtained from 186 square metre plots within 39 different sites of 10×10 m. Scatter plots that show the relationship between pollen percentages and vegetation percentages are presented forTrifolium pratense-type,Trifolium rcpens-type,Lotus, Campanula-type,Succisa, Ranunculus acris-type,Cirsium-type, Asteraceae Cichorioideae,Achillea-type,Potentilla-type, Apiaceae,Rumex sect.Acetosa, Galium-type, Cyperaceae,Calluna, Plantago lanceolata and Poaceae. Pollen representation factors relative to Poaceae (Rrel) are calculated for 54 pollen taxa. Differences in the values from different geographical areas were found in the case of some taxa, due to either different genera or species being included in the pollen taxa and/or to the different representation of high pollen producers in the different regional vegetation types. Background pollen influences the estimates for taxa such asR. sect.Acetosa, P. lanceolata, Poaceae, Cyperaceae, andCalluna, and an extended R-value (ERV) model was used to investigate the magnitude of this pollen component. Groups of roughly similar pollen representation were identified and factors to convert pollen percentages to vegetation abundances are suggested.

Morfologia polínica de Camarea St.-Hil. (Malpighiaceae)

(Morfologia polinica de Camarea St.-Hil. (Malpighiaceae)). Graos de polen de oito especies de Camarea, incluindo uma especie hibrida, sao descritos e ilustrados. As especies apresentam graos de polen muito semelhantes mostrando algumas diferencas nas aberturas e tipo de ornamentacao. Uma chave de identificacao das especies estudadas e tambem apresentada.

A comparison of two pollinators: the introduced honey bee Apis mellifera and an indigenous bee Centris tarsata on cashew Anacardium occidentale in its native range of NE Brazil

1. Aspects of the flowering biology of wild cashew Anacardium occidentale, an andro monoecious, self‐fertile tree, were studied in the north‐east of Brazil, where this species is endemic. Comparison was made among two bee species, Apis mellifera and Centris tarsata, in their pollination of cashew flowers using a number of measures including single bee visits to marked flowers. 2. Cashew flowering is protandrous within a day. Male flowers greatly outnumber hermaphrodite flowers. Stigmas lose receptivity rapidly and pollen is quickly removed from anthers yet flowers remain intact for several days. 3. Only females of C. tarsata collected pollen from cashew flowers, and then only from male flowers. The similar foraging behaviour of the nectar collectors of the two bee species under investigation when visiting hermaphrodite cashew flowers suggests that they may both act as good pollinators. 4. We develop an index of efficiency of pollen removal from anthers (PREi) whereby the relative benefits of flower visitors to a component of a plant’s male reproductive success can be quantified. 5. Comparisons of single bee visits to flowers with unvisited flowers and others receiving unlimited visits were used to show that: C. tarsata pollen collectors were more efficient than nectar collectors of either bee species at removing pollen from anthers; nectar collectors of both bee species had similar pollen removal efficiencies; C. tarsata was more efficient at depositing pollen on stigmas than A. mellifera; both bee species had statistically similar efficiencies at setting seed. 6. The indices of efficiency for some of the stages in the pollination of cashew suggest that C. tarsata flower visits may enhance plant reproductive success over flower visits by A. mellifera but that both bee species may be suitable for the pollination of commercially grown cashew. 7. Despite cashew’s single ovule per flower, high nut set demands a high rate of pollinator visitation during the peak time of stigma receptivity. Provision of additional bee pollination in commercial orchards is recommended to obtain good nut yields.

The Late Devensian Lateglacial palaeoenvironmental record from Whitrig Bog, SE Scotland. 1. Lithostratigraphy, geochemistry and palaeobotany

This is the first of a series of articles presenting the results of a multi‐proxy investigation aimed at reconstructing changes in the ecosystem and climate of Whitrig Bog, SE Scotland, during the last glacial‐inter‐glacial transition (Devensian Lateglacial, c. 14–10 ka BP). We present here the results from sediment lithology, chemistry, pollen, and plant macrofossil analyses. These data are used to infer the nature of the local catchment soils and both local and regional terrestrial vegetation. The interstadial period (c. 13–11 ka BP) is characterized by a successional sequence developing from a landscape with bare, poorly developed minerogenic soils supporting a sparse herbaceous flora into open birch woodland with juniper scrub and stable organic soils. At c. 11 ka BP the Younger Dryas climatic cooling event caused an abrupt reversion to an open herbaceous arctic/alpine flora (e.g. macrofossil evidence of Silene furcata and Oxyria digyna) and high levels of minerogenic erosion into the basin, indicating environmental response to a cold Arctic climate. In addition to this Younger Dryas climatic reversal, two lesser reversion episodes occurred earlier during the interstadial. The more pronounced of the two, late in the intersladial, is characterized by high levels of erosion and a change from birch/juniper woodland to an open herbaceous flora. The older oscillation occurs approximately mid‐way through the interstadial sequence and is marked by similar pollen changes, albeit shorter lived and more subtle.

The functional ecology of gynodioecy in Eritrichum aretioides (Boraginaceae), the Alpine Forget‐Me‐Not

Eritrichum aretioides is a gynodioecious species with female and hermaphrodite individuals. In populations on Pennsylvania Mountain in central Colorado (USA), the frequency of females ranges from 22 to 41%. Flower number and the number of seeds produced per flower were similar in hermaphrodites and females. However, hermaphrodites produced larger flowers, while females produced larger seeds (P < 0.05 for both). In the field, seed germination was higher for seeds from females than for seeds from hermaphrodites (20 vs. 9% germination; P < 0.05). Unvisited flowers and open-pollinated flowers of hermaphrodites had similar pollen receipt (approx 20 pollen grains per stigma), but seed set following autogamous pollination was significantly lower than seed set following natural pollination. This finding indicates that hermaphrodites have a barrier to selfing and implies that the larger seed size and greater establishment advantage of offspring from females is unlikely to have resulted from female outcrossing advantage. Rather, differences in the quality of seed progeny between morphs probably reflect a trade-off in sexual allocation or pleiotropic effects of the sex-determining genes.