Morphology of pollen and orbicules in the tribe Spiraeeae (Rosaceae) and its systematic implications

This study provides pollen data for 38 representative taxa belonging to all nine genera in the current classification of the tribe Spiraeeae (Rosaceae) including the monotypic Korean endemic genus Pentactina, and considers the distribution of orbicules for the first time. Pollen morphology and wall stratification were investigated using light, scanning electron and transmission electron microscopy. Spiraeeae pollen grains are small to medium in size (P = 6.9–34.0 μm, E = 7.1–28.0 μm), oblate to prolate in shape (P/E = 0.66–1.48) and tri-colporate. Spiraeeae pollen is generally characterised by striate sexine ornamentation, but four ornamentation types are recognised based on the length and direction of the ridge patterns. The observed variation in sexine ornamentation is particularly valuable at the generic level. The exine stratification of the representative Spiraeeae studied is similar and characterised by unbranched columellae and a continuous endexine. Orbicules are present in three genera of the tribe (Luetkea, Sibiraea and Xerospiraea). Orbicule distribution patterns indicate that the absence of orbicules is a synapomorphic condition of the more derived clade, comprising Pentactina + Petrophytum + Kelseya + Spiraea.     

A new mode of ammonite preservation – implications for dating of condensed phosphorite deposits

Unusual phosphatic casts of the ammonites Mortoniceras (Subschloenbachia) sp. and Stoliczkaia sp. from the upper Albian condensed phosphorite bed at Annopol, Poland, are discussed in terms of their taphonomic history. These specimens are interpreted as ‘secondary’ external casts of ammonite replicas preserved originally as attachment scars on oyster shells. The following genetic history is suggested for this previously undocumented mode of ammonite preservation: (1) settling of shells of dead ammonites on the seafloor; (2) colonization of these shells by oysters and formation of ammonite replicas on left valves of oysters; (3) dissolution of ammonite shells; (4) reworking and fragmentation of oyster shells; (5) casting of ammonite replicas by phosphatic material; and (6) separation of ammonite casts from oyster shells, either through mechanical disintegration or dissolution of the latter. The specimens studied were formed after dissolution of the ammonite conchs, not prior to this event as in the case of typical ammonite steinkerns (internal moulds). Therefore, they are here referred to as ‘pseudo‐steinkerns’. The time interval between loss of the original ammonite shells and the formation of oyster‐mediated pseudo‐steinkerns may be very extensive. Therefore, the pseudo‐steinkerns may potentially mislead in biostratigraphic dating of condensed phosphorite deposits.     

Systematics, similarity and Acanthaceae pollen morphology

SCOTLAND, R. W., 1992. Systematics, similarity and Acanthaceae pollen morphology. A brief discussion of the history of Acanthaceae classifications is provided. It is argued that several approaches utilizing pollen morphological data for the classification of the family can be identified. The Lindau pollen types are shown to have an indirect relationship to Lindau's own classification. Pollen morphological similarity is explored within the context of cladistic methodology. It is shown that some of the Lindau pollen types are analogous. It is demonstrated that shared similarities can be of three types: conflicting (homoplasious), plesiomorphic and apomorphic.     

Effaced preservation in the Ediacara biota and its implications for the early macrofossil record

Abstract: Ediacaran structures known as ‘pizza discs’ or Ivesheadia have long been considered enigmatic. They are amongst the oldest known members of the Ediacara biota, apparently restricted to the Avalonian successions of Newfoundland and the UK, c. 579–560 Ma. Here, we suggest that these impressions are taphomorphs, resulting from the post‐mortem decay of the frondose Ediacaran biota. Ediacaran fossils range from well‐preserved, high‐fidelity variants to almost completely effaced specimens. The effaced specimens are inferred to have undergone modification of their original morphology by post‐mortem microbial decay on the sea floor, combined with sediment trapping and binding. In this style of preservation, morphological details within the organism became variously subdued as a function of the extent of organic decay prior to casting by overlying sediments. Decay and effacement were progressive in nature, producing a continuum of grades of preservation on Ediacaran bedding planes. Fossils preserved by such ‘effaced preservation’ are those that have suffered these processes to the extent that only their gross form can be determined. We suggest that the lack of detailed morphology in effaced specimens renders such fossils unsuitable for use as type material, as it is possible that several taxa may, upon degradation and burial, generate similar morphological taphomorphs. We here reinterpret the genus Ivesheadia as a taphomorph resulting from extensive post‐mortem decay of frondose organisms. Blackbrookia, Pseudovendia and Shepshedia from beds of comparable age in England are likewise regarded as taphomorphs broadly related to Charnia or Charniodiscus spp. To reflect the suggestion that such impressions are likely to be taphomorphs, and not taxonomically discrete, we propose the term ivesheadiomorphs to incorporate all such effaced taphonomic expressions of Ediacaran macrofossil taxa in Avalonian assemblages. Our recognition of effaced preservation has significant implications for Ediacaran taxonomy, and consequently for measures of Ediacaran diversity and disparity. It is implied that Avalonian assemblages preserve both organisms that were alive and organisms that were already dead at the time of burial. As such, the fossil assemblages cannot be taken to represent census populations of living organisms, as in prior interpretations.     

Decaying in different clays: implications for soft‐tissue preservation

Lagerstätten, places where soft‐bodied organisms became mineralized, provide a substantial bulk of palaeobiological information, but the detailed mechanisms of how soft‐tissue preservation takes place remain debatable. An experimental taphonomy approach, which allows for direct study of decay and mineralization, offers a means to study the preservational potential of different soft‐bodied organisms under controlled conditions. Here we compare the preservational capacity of two types of clay (kaolinite and montmorillonite) through a long‐term (24 month) experiment involving the burial and decay of small crustaceans. Our experimental design is innovative in that it models catastrophic sedimentation in fine‐grained colloidal suspension, which is believed to form Lagerstätten deposits. We demonstrated better preservation of buried organisms in clays compared to water, and in kaolinite compared to montmorillonite. As aluminium cations were present in high concentrations in kaolinite sediment but not in montmorillonite, the better preservation in kaolinite is attributed to the tanning properties of aluminium, which catalyses cross‐linking in proteins, protecting them from bacterial degradation. Anaerobic environments and acidification also slow down decay, but they are less effective than tanning. Kaolinite and montmorillonite replaced the crustacean integuments differently: in the remains buried in kaolinite, Al and Si were detected in equal proportions, while in those buried in montmorillonite, the Si content appeared to be much higher even in comparison with the initial sample of the clay. These variations probably arose from the different dynamics of acidic hydrolysis in the two clays associated with anaerobic decomposition of organic matter. Our results show that the preservation mechanism includes multi‐component interactions between the solution, mineral, sediment and organic remains; taken separately, any single component explains little. The specific conditions that occur within the colloidal clay sediments can facilitate conservation and start fast mineralization according to chemical properties and elemental content.     

Aerodynamics of saccate pollen and its implications for wind pollination

Pollen grains of many wind-pollinated plants contain 1-3 air-filled bladders, or sacci. Sacci are thought to help orient the pollen grain in the pollination droplet. Sacci also increase surface area of the pollen grain, yet add minimal mass, thereby increasing dispersal distance; however, this aerodynamic hypothesis has not been tested in a published study. Using scanning electron and transmission electron microscopy, mathematical modeling, and the saccate pollen of three extant conifers with structurally different pollen grains (Pinus, Falcatifolium, Dacrydium), we developed a computational model to investigate pollen flight. The model calculates terminal settling velocity based on structural characters of the pollen grain, including lengths, widths, and depths of the main body and sacci; angle of saccus rotation; and thicknesses of the saccus wall, endoreticulations, intine, and exine. The settling speeds predicted by the model were empirically validated by stroboscopic photography. This study is the first to quantitatively demonstrate the adaptive significance of sacci for the aerodynamics of wind pollination. Modeling pollen both with and without sacci indicated that sacci can reduce pollen settling speeds, thereby increasing dispersal distance, with the exception of pollen grains having robust endoreticulations and those with thick saccus walls. Furthermore, because the mathematical model is based on structural characters and error propagation methods show that the model yields valid results when sample sizes are small, the flight dynamics of fossil pollen can be investigated. Several fossils were studied, including bisaccate (Pinus, Pteruchus, Caytonanthus), monosaccate (Gothania), and nonsaccate (Monoletes) pollen types.     

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.     

Biodiversity and pollen analysis: modern pollen studies and the recent history of a floodplain woodland in S. W. Ireland

One of the problems with biodiversity for palynologists is that their samples come from an unbounded area and source area varies with both pollen/spore type and vegetation type. There have been two broad approaches to the problem of inferring diversity from pollen/spore samples; firstly the use of pollen type richness as a proxy for species richness, and secondly the ‘identification’ of past vegetation communities aided by ecological inference and historical or modern data concerning species affinities and typical diversity. The estimation of biodiversity from pollen analysis depends upon the pollen count, taxonomic precision, source strength for individual types and dispersal/transport of pollen from source areas to the site. A transect of surface pollen samples is used here to test the effect of a vegetation boundary on pollen/spore diversity and compare the pollen/spore diversity with the species richness of the woodland. Palynological richness (at a constant count sum) does, to some extent, reflect changing local vegetation along the transect. Type count curves also reflect the changes in vegetation type along the transect due to the partial influence of species richness on pollen/spore richness. This study suggests that depending upon the woodland composition, the woodland may not entirely drown-out the pollen signal of the surrounding vegetation, and that a small woodland may be more representative (as a sampling site) of the valley floor diversity than a raised mire. The surface transect is also used in the interpretation of Medieval pollen levels from The Gearagh.     

Experimental taphonomy of giant sulphur bacteria: implications for the interpretation of the embryo-like Ediacaran Doushantuo fossils

The Ediacaran Doushantuo biota has yielded fossils interpreted as eukaryotic organisms, either animal embryos or eukaryotes basal or distantly related to Metazoa. However, the fossils have been interpreted alternatively as giant sulphur bacteria similar to the extant Thiomargarita. To test this hypothesis, living and decayed Thiomargarita were compared with Doushantuo fossils and experimental taphonomic pathways were compared with modern embryos. In the fossils, as in eukaryotic cells, subcellular structures are distributed throughout cell volume; in Thiomargarita, a central vacuole encompasses approximately 98 per cent cell volume. Key features of the fossils, including putative lipid vesicles and nuclei, complex envelope ornament, and ornate outer vesicles are incompatible with living and decay morphologies observed in Thiomargarita. Microbial taphonomy of Thiomargarita also differed from that of embryos. Embryo tissues can be consumed and replaced by bacteria, forming a replica composed of a three-dimensional biofilm, a stable fabric for potential fossilization. Vacuolated Thiomargarita cells collapse easily and do not provide an internal substrate for bacteria. The findings do not support the hypothesis that giant sulphur bacteria are an appropriate interpretative model for the embryo-like Doushantuo fossils. However, sulphur bacteria may have mediated fossil mineralization and may provide a potential bacterial analogue for other macroscopic Precambrian remains.     

Recent advances in amniote palaeocolour reconstruction and a framework for future research

Preserved melanin pigments have been discovered in fossilised integumentary appendages of several amniote lineages (fishes, frogs, snakes, marine reptiles, non‐avialan dinosaurs, birds, and mammals) excavated from lagerstätten across the globe. Melanisation is a leading factor in organic integument preservation in these fossils. Melanin in extant vertebrates is typically stored in rod‐ to sphere‐shaped, lysosome‐derived, membrane‐bound vesicles called melanosomes. Black, dark brown, and grey colours are produced by eumelanin, and reddish‐brown colours are produced by phaeomelanin. Specific morphotypes and nanostructural arrangements of melanosomes and their relation to the keratin matrix in integumentary appendages create the so‐called 'structural colours'. Reconstruction of colour patterns in ancient animals has opened an exciting new avenue for studying their life, behaviour and ecology. Modern relationships between the shape, arrangement, and size of avian melanosomes, melanin chemistry, and feather colour have been applied to reconstruct the hues and colour patterns of isolated feathers and plumages of the dinosaurs Anchiornis, Sinosauropteryx, and Microraptor in seminal papers that initiated the field of palaeocolour reconstruction. Since then, further research has identified countershading camouflage patterns, and informed subsequent predictions on the ecology and behaviour of these extinct animals. However, palaeocolour reconstruction remains a nascent field, and current approaches have considerable potential for further refinement, standardisation, and expansion. This includes detailed study of non‐melanic pigments that might be preserved in fossilised integuments. A common issue among existing palaeocolour studies is the lack of contextualisation of different lines of evidence and the wide variety of techniques currently employed. To that end, this review focused on fossil amniotes: (i) produces an overarching framework that appropriately reconstructs palaeocolour by accounting for the chemical signatures of various pigments, morphology and local arrangement of pigment‐bearing vesicles, pigment concentration, macroscopic colour patterns, and taphonomy; (ii) provides background context for the evolution of colour‐producing mechanisms; and (iii) encourages future efforts in palaeocolour reconstructions particularly of less‐studied groups such as non‐dinosaur archosaurs and non‐archosaur amniotes.     

一株氨氧化链霉菌的分类鉴定及其氨氧化特性的研究

从硝化反应器中分离获得一株链霉菌。根据其形态特征、培养特征、生理生化特性,（G+C）mol％含量以及16S rDNA序列和DNA杂交结果,将其归入链霉菌属中的比基尼链霉菌（Streptomycesbikiniensis）。该菌株既能在YD培养基上异养生长,也能在无机培养基上自养生长,异养生长速率(Vmax为0.39mg/L\5d)明显高于自养生长速率（Vmax为0.22mg/L.d）。异养生长时,氨氮主要用于合成细胞物质;自养生长时,部分氨氮用于合成细胞物质,部分氨氮转化成亚硝酸盐。在无机培养基上自养生长时,最适氨浓度为118mgN/L。最适生长pH值为9.36,最适氨氧化pH值为9.29。最适生长温度为31℃,最适氨氧化温度为40.6℃。提高溶解氧浓度有利于该菌株生长和氨氧化,菌体生长对溶解氧浓度的敏感性高于氨氧化。     

A taphonomic study of modern pollen assemblages from dung and surface sediments in arid environments of Spain

Coastal plant communities in arid southeastern Spain are characterized by insect-pollinated scrub species, which fail to occur in Quaternary pollen sequences from valleys, marshlands and marine cores. We investigate pollen–vegetation relationships in samples from soil surfaces, animal dung, and sediments in depressions or basins that, in theory, should have pollen spectra that are comparable to those from sedimentary basins elsewhere. Pollen spectra from basins or depressions are very susceptible to long-distance wind and water transport. This can mask representation of pollen from the surrounding insect-pollinated vegetation, as can over-representation of basin-margin halophilous and hydrophilous pollen. Pollen spectra from biogenic materials of animal origin are the best analogues of local and regional vegetation, and show the best analytical potential in terms of pollen concentration and taxon diversity. Pollination properties of the species studied indicate they will rarely be found in most conventional pollen records. It cannot be stressed too strongly that insight into Quaternary vegetation of arid regions demands complementary pollen analysis of coprolites, urine-cemented deposits, and cave sediments with preserved biotic remains, in addition to water-lain sediments.     

A 6500-year pollen record from the Polistovo-Lovatskaya Mire System (northwest European Russia). Vegetation dynamics and signs of human impact

New pollen and plant macrofossil evidence from the Polistovo-Lovatskaya Mire System is presented. The results show that local vegetation of the mire system was affected by various factors such as climate, hydrogeology and autochthonous processes in the peat bog. An important palaeoecological event took place around 6500 cal bp and led to a dramatic increase of paludification processes and lateral expansion of the mire. Forests of spruce and broad-leaved species in various combinations represented primary vegetation of uplands; they began to degrade around 1500 years ago and disappeared in historical times (400–500 cal bp). First signs of arable farming in the area occurred around 4200 cal bp, regular and mild human pressure established about 1000 years cal bp, and a significant impact at the regional level became evident around 400 years ago.     

A well‐preserved isopod from the Middle Jurassic of southern Germany and implications for the isopod fossil record

A new isopod species, Eonatatolana geisingensis gen. et sp. nov., is described from Middle Jurassic shallow‐water sediments of southern Germany. It shows not only the almost completely preserved dorsal morphology but, in addition, details of the cephalic appendages, the pereiopods, pleopods and uropods. The presence of ambulatory pereiopods I–VII of a wide tridentate mandibular incisor with prominently developed posteriormost tooth and a narrow frontal lamina indicates that the new species belongs to the subfamily Conilerinae of family Cirolanidae within the suborder Cymothoida. It is closer to the species of the modern genus NatatolanaBruce than to any fossil isopod hitherto described. The isopod fossil record as well as current practices of isopod taxonomy in palaeontology are discussed, and the facies distribution and fossilization of isopods is reviewed with examples from the Jurassic.     

Seasonal variation in surface soil pollen taxa over 12 months in three English mature woodlands

This study aimed to determine whether or not a seasonal, or even monthly, pattern of pollen accumulation could be found in surface soil. Three mature woodlands in the English Midlands were selected and soil samples were taken from the same area, each month, for 12 months. Pollen types were recorded and compared across the woodlands. Pollen condition was assessed for seasonal differences in Bannam’s woodland. Two of the woodlands (Windmill Naps and Wirehill) had pollen assemblages that were dominated heavily by Quercus pollen but the third (Bannam’s) was more balanced. Each pollen type found was present in almost every month and winter was, for some types, a time of increased pollen. No clear, consistent patterns were visible in the results across the woodlands or for each pollen type. Although some pollen types showed an increase in levels during their flowering season, this was only consistent across all three woodlands for grasses (Poaceae). The condition of the pollen grains remained similar across the 12 months with a small (up to 12%) increase in fresh pollen in May. This study concludes that for damp woodland soil in the English Midlands, a clear, seasonal or monthly pattern cannot be determined.     

Coordination abilities of neurokinin A and its derivative and products of metal-catalyzed oxidation

The classical tachykinins, substance P, neurokinin A and neurokinin B are predominantly found in the nervous system where they act as neurotransmitters and neuromodulators. Significantly reduced levels of these peptides were observed in neurodegenerative diseases and it may be suggested that this reduction may also result from the copper(II)-catalyzed oxidation. The studies of the interaction of copper(II) with neurokinin A and the copper(II)-catalyzed oxidation were performed. Copper(II) complexes of the neurokinin A (His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH₂) and acetyl-neurokinin A (Ac-His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH₂) were studied by potentiometric, UV-Vis (UV-visible), CD (circular dichroism) and EPR spectroscopic methods to determine the stoichiometry, stability constants and coordination modes in the complexes formed. The histidine residue in first position of the peptide chain of neurokinin A coordinates strongly to Cu(II) ion with histamine-like {NH₂, N_Im} coordination mode. With increasing of pH, the formation of a dimeric complex Cu₂H₂L₂ was found but this dimeric species does not prevent the deprotonation and coordination of the amide nitrogens. In the Ac-neurokinin A case copper(II) coordination starts from the imidazole nitrogen of the His; afterwards three deprotonated amide nitrogens are progressively involved in copper coordination. To elucidate the products of the copper(II)-catalyzed oxidation of the neurokinin A and Ac-neurokinin A, liquid chromatography-mass spectrometry (LC-MS) method and Cu(II)/hydrogen peroxide as a model oxidizing system were employed.Oxidation target for both studied peptides is the histidine residue coordinated to the metal ions. Both peptides contain Met and His residues and are very susceptible on the copper(II)-catalyzed oxidation.     

Variation and similarities in pollen features in some basal angiosperms, with some taxonomic implications

Species within three families of basal angiosperms (Trimeniaceae, Winteraceae, Monimiaceae) illustrate differences and similarities in pollen within a species, between species and between genera. Trimenia papuana (Trimeniaceae) has dimorphic pollen (inaperturate, polyforate), each confined to different individual plants. Other species have either disulculate or polyforate pollen. Evolution seems to be from disulculate to inaperturate to polyforate. Present-day Winteraceae have pollen in permanent tetrads except four species of Zygogynum with monads. Why? Did such monads appear as fossils before tetrads in Winteraceae? Molecular studies of Takhtajania perrieri indicate it is basal but its unique bicarpellate unilocular gynoecium seems derived. Although Hedycarya arborea and Kibaropsis caledonica have near-identical permanent pollen tetrads, many other features are very different. Hedycarya species have permanent tetrads or inaperturate monads with spinulose, `starry' or other sculpturing, and it is suggested this and recent molecular data indicate further studies are needed to determine generic limits.     

Viability and sunlight sensitivity of oak pollen and its implications for pollen-mediated gene flow

Pollen-mediated gene flow and the male reproductive success of wind-pollinated trees depend on the initial viability of the pollen and the changes that occur in its viability during transport in the atmosphere. The viability of Quercus robur pollen was determined before and during exposure to sunlight by in vitro germination and the fluorescein diacetate reaction (FCR) in 2002 and 2003, respectively. These experiments allowed us to calculate initial pollen viability and pollen sensitivity to sunlight. The germination test revealed a lower initial pollen viability (25–65%) than the FCR (53–92%). Following 9.5 h of irradiation the viability was reduced to 75–100% as determined by the in vitro germination test or to 40–70% as determined by the FCR. The actual values of initial pollen viability and pollen sensitivity to sunlight were used to define a range of values for modelling pollen dispersal using the mesoscale meteorological model METRAS. The deposition patterns of viable pollen varied by as much as a factor of 14 by changing the viability parameters in the range of the observed values. This suggests significant differences in male reproductive success. Variations in initial pollen viability have stronger effects on the gene-flow pattern than do variations in pollen sensitivity to sunlight. In particular, pollen distribution throughout the local environment is shaped by the initial pollen viability, while pollen sensitivity to sunlight mainly influences long-distance pollen dispersal.This revised version was published online in February 2005 with corrections to an incorrect sentence in the Results section. Under Pollen Sensitivity it should read: decreased faster when assessed by the germination test than by the FCR.     

A new methodology for reconstructing climate and vegetation from modern pollen assemblages: an example from British Columbia

Aim We used modern pollen assemblages to develop a method for climate reconstruction that reduces the spatial autocorrelation of residuals and accounts for the strong topographic and climatic variation that occurs in British Columbia, Canada. Location British Columbia, Canada, including sites both on the mainland and on adjacent islands (Queen Charlotte Islands and Vancouver Island). Methods New pollen assemblages from surface‐sediment samples collected in British Columbia were combined with other published and unpublished samples (n = 284). Multivariate rank‐distances between sample sites and a randomized set of sites within the province were calculated for climate parameters to determine whether gaps in the current network of present‐day pollen sample sites exist. Lacustrine surface‐sediment pollen assemblages (n = 145) were ordinated using non‐metric multidimensional scaling (NMDS), and a generalized additive model (GAM) was used to reconstruct modern mean warmest month temperature (MWMT) and mean annual precipitation (MAP) from the NMDS ordination. The results were compared with standard climate reconstruction techniques, including the modern analogue technique, partial least squares, weighted averaging, weighted averaging–partial least squares and factor analysis. Results Reconstructions of MWMT and MAP using NMDS and GAM were comparable to those of existing models. When reconstructing MWMT, the NMDS/GAM method had a lower root‐mean‐squared error of prediction (RMSEP), lower spatial autocorrelation and higher correlation with observed temperature values than the other methods tested. When reconstructing MAP, the partial least squares method performed better than the NMDS/GAM method for RMSEP and correlation with observed values; however, the NMDS/GAM method had a lower spatial autocorrelation of residuals. Main conclusions NMDS reveals strong relationships among modern pollen assemblages, vegetation and climate parameters. Climate models using NMDS and GAM are comparable to other palaeoecological reconstruction models, but provide lower spatial autocorrelation of residuals for both parameters tested. An inverse distance‐weighted surface of multivariate rank‐climate distances generated from the network of pollen sample sites indicates that greater sampling intensity in north‐western and central‐interior British Columbia is required in order to obtain an accurate representation of climatic and vegetation diversity in the province.     

The relation between pollen exine sculpturing and self-incompatibility mechanisms

In angiosperm pollen the reticulate-perforate exine sculpturing is associated with sporophytic self-incompatibility (S.S.I.) and imperforate and microperforate exine sculpturing is associated with gametophytic self-incompatibility. The earliest unequivocal angiosperm pollen conforms to exine morphology of pollen from plants with S.S.I. The orgin of S.S.I. is hypothesized to have coincided with the appearance of what is now the earliest recognizable angiosperm pollen. Other angiosperm characteristics correlated with S.I., functional stigmatic areas, large showy flowers (or aggregated inflorescences), and passive seed dispersal, provide some insight into the biological aspects of the earliest angiosperms.