Group Of Woody Plants Research Articles

Analysis of the flora of woody plants in the Reserve Park of the Siberian Botanical Garden of TSU

The article presents the results of the analysis of the flora of woody plants in the Reserve Park of the Siberian Botanical Garden of Tomsk State University. In the course of this study, taxonomic, geographical, ecological and biomorphological analyzes of the tree assortment of the park were carried out. The list of flora of the Reserve Park includes 126 species of woody plants belonging to 27 families and 57 genera. The largest families in terms of number of species are Rosaceae (26 %) and Salicaceae (11 %). In the park, angiosperms significantly predominate over gymnosperms. The most represented are species with East Asian (33.3 %), Eurasian (26.2 %) and North American (13.5 %) ranges. There are few Central Asian species (2.4 %). Introduced tree species (68 %) prevail over local Siberian species (32 %). Mesophytes account for a significant part of the park’s woody vegetation (64 %), hydromesophytes (32 %) and xeromesophytes (4 %) are less numerous. Woody plants of the park are mainly shade-tolerant (55 %) or light-loving (44 %). The park is dominated by upstanding shrubs (60 %), forest type trees account for 20 % of the total number of species, most of them are deciduous species. Upstanding shrubs with an East Asian habitat are included in the most numerous group of woody plants (22 % of the total number of species).

Pioneering polyploids: the impact of whole-genome duplication on biome shifting in New Zealand Coprosma (Rubiaceae) and Veronica (Plantaginaceae).

The role of whole-genome duplication (WGD) in facilitating shifts into novel biomes remains unknown. Focusing on two diverse woody plant groups in New Zealand, Coprosma (Rubiaceae) and Veronica (Plantaginaceae), we investigate how biome occupancy varies with ploidy level, and test the hypothesis that WGD increases the rate of biome shifting. Ploidy levels and biome occupancy (forest, open and alpine) were determined for indigenous species in both clades. The distribution of low-ploidy (Coprosma: 2x, Veronica: 6x) versus high-ploidy (Coprosma: 4-10x, Veronica: 12-18x) species across biomes was tested statistically. Estimation of the phylogenetic history of biome occupancy and WGD was performed using time-calibrated phylogenies and the R package BioGeoBEARS. Trait-dependent dispersal models were implemented to determine support for an increased rate of biome shifting among high-ploidy lineages. We find support for a greater than random portion of high-ploidy species occupying multiple biomes. We also find strong support for high-ploidy lineages showing a three- to eightfold increase in the rate of biome shifts. These results suggest that WGD promotes ecological expansion into new biomes.

Dendrocenosis of the Bila Tserkva national agricultural university main building courtyard: diversity, age and condition

The paper reveals the results of taxonomic assessment, phytosanitary monitoring and general condition of the dendrocenosis the BNAU main building the courtyard. It is established that the age structure of plantations ranges from 10 to 80 years, with 60 years old plants to make 12 %. The group of woody plants aged from 41 to 50 years is most numerous (33 % of the total number of trees); the larges number of shrubs ages 16–20 years (6 %). The structure of the dendrocenosis of the courtyard is formed by species of woody plants, the share of their participation ranges from 5.8 to 15 % of the total number of trees: Aesculus hippocastanum L. (15 %), Acer platanoides (9.2 %), Catalpa bignonioides Walt. (7.5 %), Populus tremula L. (6.7 %), Juglans cinerea L. (6.7 %), Ulmus glabra Huds. (6.7 %), Tilia platyphyllos Scop. (5.8 %). According to the life forms of plants, the dendrocenosis is represented by trees (81.7 %) and shrubs (183.%). The taxonomic assessment of the dendrocenosis reveals that that 120 specimens of shrubs are represented by 27 species, grouped into 23 genera of 17 families of 12 orders of 2 divisions. Magnoliophyta predominates in terms of species diversity, which is represented by 24 species from 20 genera of 16 families of 11 orders. According to the number of specimens represented by families, they can be ranked as follows: Sapindaceae Juss. > Juglandaceae DC. ex Perleb> Malvaceae Juss. > Bignoniaceae Juss. > Ulmaceae Mirb. > Salicaceae Mirb. > Oleaceae Hoffmanns. & Link> Anacardiaceae R.Br. > Fabaceae Juss. > Adoxaceae E.Mey. > Paeoniaceae Raf. According to the number of woody plants, the relative living condition of the dendrocenosis is 75 %, which characterizes the weakened condition of the stand of the BNAU main building courtyard. The best living condition was observed in 46 % of the species stand such as Picea abies L., Pinus sylvestris L., Pseudotsuga menziesii (Mirb.) Franco, Fraxinus excelsior L., Styphnolobium japonicum L., Carpinus betulus L., Rhus typhina L., Acer negundo L., Tilia cordata Mill. Under the influence of various biotic and abiotic factors, 26 % of shrubs are in a weakened state, 17 % are severely weakened, 11 % are withered. Key words: dendrocenosis, tree-shrub vegetation, species, genus, family, living condition.

In Vitro Plant Regeneration in Conifers: The Role of WOX and KNOX Gene Families.

Conifers are a group of woody plants with an enormous economic and ecological importance. Breeding programs are necessary to select superior varieties for planting, but they have many limitations due to the biological characteristics of conifers. Somatic embryogenesis (SE) and de novo organogenesis (DNO) from in vitro cultured tissues are two ways of plant mass propagation that help to overcome this problem. Although both processes are difficult to achieve in conifers, they offer advantages like a great efficiency, the possibilities to cryopreserve the embryogenic lines, and the ability of multiplying adult trees (the main bottleneck in conifer cloning) through DNO. Moreover, SE and DNO represent appropriate experimental systems to study the molecular bases of developmental processes in conifers such as embryogenesis and shoot apical meristem (SAM) establishment. Some of the key genes regulating these processes belong to the WOX and KNOX homeobox gene families, whose function has been widely described in Arabidopsis thaliana. The sequences and roles of these genes in conifers are similar to those found in angiosperms, but some particularities exist, like the presence of WOXX, a gene that putatively participates in the establishment of SAM in somatic embryos and plantlets of Pinus pinaster.

Аналіз дендрофлори плоских озеленених дахів екстенсивного типу в місті Львові

Roof gardens, which perform many useful functions for humans, are one of the most modern ways to create a harmonious and aesthetic environment in cities. Therefore, the study of the list of woody plants that successfully overwinter and tolerate critical summer temperatures on the roofs with minimal tending, is an important task for green space workers. The taxonomic composition of the dendroflora of 24 flat of extensive type in the city of Lviv at heights from 5 to 40 m was studied and its system-structural analysis was performed. It was found that the dendroflora of the examined objects was composed of 167 taxonomic units of woody plants (of which 109 species, 76 cultivars, 10 hybrids). The family Rosaceae Juss is numerically superior (13 genera (21.1% of the total number of genera), 32 species and hybrids (26.9%); by the number of cultivars, the Cupressaceae family dominates - 32 cultivars (42.7%). The genus Juniperus dominates in the genus spectrum in terms of the number of species, hybrids and cultivars - 10 species (8.8% of the total number), 13 cultivars (17.1%). For greening the roofs, 93 species and cultivars of deciduous plants, 74 evergreen phanerophytes (28 mesophanerophytes, 69 microfanerophytes, 60 nanophanerophytes and 10 woody lianas) were used. According to the results of the chorological analysis, it was found that species from the East Asian region and North America predominate on the roofs, indigenous species are practically not used. The plant compositions on the roofs are dominated by species regionalized for USDA-frost resistance zones 4 and 5, while the territory of Lviv lies within zone 6. Our 4-year observations proved the success of the introduction on roofs of species of a higher USDA zone than that defined for Lviv. Further study of the dendroflora of green roofs is very important, taking into account several points: the system-structural patterns of species selection for greenery have not been fully clarified; methods of specific introduction of plants on roofs and the possibility of their acclimatization, which is different from terrestrial objects, have not been tested; the possibilities of introducing a list of plants that are not found in garden and park compositions of the city have not been fully studied. Compositional solutions of green roofs are determined by various ways of planting plants - directly into the substrate, in beds or containers raised above the surface. Such studies highlight the peculiarities of the taxonomic composition and structure of the dendroflora of green roofs, which will make it possible to significantly adjust the agronomic techniques of plant maintenance and identify the most promising group of woody plants for greening roofs.

When nature meets the divine: effect of prohibition regimes on the structure and tree species composition of sacred forests in northern Greece

Abstract. Sacred forests are an integral component of the mountainous cultural landscape of northern Greece, hypothesized to be the result of both ecological processes and site-specific forest management regimes through strict religious prohibition. These practices acted as constraints on natural forest development by suppressing understory growth, while prohibition of woodcutting has preserved large trees. The aim of this study was to investigate the relative effects of physical site environment and management regimes on the structure and composition of woody plant groups in six such forests. Species rank–abundance curves, dissimilarity indices and cluster analyses were used to assess variation within and amongst the woody plant groups of the sites. Species abundance was found to be highly variable amongst the sites, with notable variation between canopy and understory layers indicating dynamic change in floristics and structure. Cluster analysis revealed four main woody plant groups statistically associated with environmental variables (aspect) and forest management (different forest prohibition regimes, and presence or absence of infrastructure). Our results indicate that tree composition is significantly associated with different prohibition regimes linked to the forests' sacred status, as well as the inherent environmental variation amongst sites. Exploring further the role of traditional management systems in shaping sacred forest structure is a relevant research path for designing effective conservation practices tailored to sacred natural sites facing cultural abandonment.

A heuristic classification of woody plants based on contrasting shade and drought strategies.

Woody plants vary in their adaptations to drought and shade. For a better prediction of vegetation responses to drought and shade within dynamic global vegetation models, it is critical to group species into functional types with similar adaptations. One of the key challenges is that the adaptations are generally determined by a large number of plant traits that may not be available for a large number of species. In this study, we present two heuristic woody plant groups that were separated using cluster analysis in a three-dimensional trait-environment space based on three key metrics for each species: mean xylem embolism resistance, shade tolerance and habitat aridity. The two heuristic groups separate these species into tolerators and avoiders. The tolerators either rely on their high embolism resistance to tolerate drought in arid habitats (e.g., Juniperus and Prunus) or rely on high shade tolerance to withstand shaded conditions in wet habitats (e.g., Picea, Abies and Acer). In contrast, all avoiders have low embolism resistance and low shade tolerance. In arid habitats, avoiders tend to minimize catastrophic embolism (e.g., most Pinus species) while in wet habitats, they may survive despite low shade tolerance (e.g., Betula, Populus, Alnus and Salix). Because our approach links traits to the environmental conditions, we expect it could be a promising framework for predicting changes in species composition, and therefore ecosystem function, under changing environmental conditions.

Phylogeny of the Detarioid Legume Genera Cynometra and Maniltoa (Leguminosae)

The genus Cynometra (Leguminosae, Detarioideae) is a large, pantropical group of woody plants ranging in size from 5–50 m. While many recent advances have been made in higher level legume systematics, many large genera still require more study to test their monophyly. Further, its relationship to the much smaller Pacific genus Maniltoa is unclear. Here we present the first broadly-sampled phylogeny of Cynometra and Maniltoa, based on molecular data from three chloroplast loci: matK, the trnL intron, and the trnL intergenic spacer. Our analyses indicate that Cynometra is not monophyletic as currently circumscribed, as several researchers had previously suspected. We recover two strongly supported clades of Cynometra s. l.; one that is most closely related to a clade consisting of the genera Dicymbe and Polystemonanthus and is composed of exclusively African taxa, and another clade that is pantropical and is nested in a larger clade with the Scorodolphoeus group and the genera Normandiodendron, Neochevalierodendron, and Zenkerella. Futhermore, the genus Maniltoa is nested within the pantropical Cynometra clade and is also non-monophyletic. The two clades are each supported by several morphological characters that can be used to distinguish between them (e.g. inflorescence structure, pedicel articulation, fruit dehiscence). These results will be used to modify the classification by moving the relevant African taxa to a new genus and placing Maniltoa in synonymy with Cynometra.

Flow cytometry and cytogenetic tools in eucalypts: genome size variation × karyotype stability

The eucalypts comprise a group of woody plants used in commercial forest plantations owing to their high growth rates, adaptability to various ecological conditions and multiple applications. Despite the enormous amount of molecular data available for eucalypts, a basic understanding of the nature of its genome still requires information regarding the DNA amount in the genus. In this work, we estimated the genome size and base composition of 25 eucalypt species. With a comparative karyotype approach, we aimed to identify possible chromosomal alterations correlated with the genome size variation. Classical cytogenetic and genomic in situ hybridization experiments were conducted for this purpose. The studied species showed genome size ranging from 2C = 0.91 (Corymbia intermedia) to 2C = 1.37 pg (Eucalyptus paniculata) and AT/CG ratios varying from AT = 61.3 (Eucalyptus urophylla) to AT = 62.85% (C. intermedia). Comparative karyotype analysis revealed no remarkable differences in chromosome number (2n = 22) or morphology among eucalypt species despite considerable differences in nuclear DNA content. The genome in situ hybridization method did not distinguish non-homologous chromosomal regions of Eucalyptus baileyana and Corymbia citriodora, despite the difference of 0.45 pg between their genome sizes. The results found in the present work corroborate the consideration of small and dispersed DNA changes as the main cause of genome size variation in eucalypts.

Analyses of Black Grouse (Tetrao tetrix) faeces with infrared spectroscopic methods

In recent years, the Fourier transform infrared spectroscopy (FT-IR) was used to assess the diet, digestibility or nutritional values of food items of ruminants. However, it has never been used to analyse the diet of grouse species. Commonly used methods have so far been direct observations of birds and microscopical analyses of droppings. The sample preparation and comparison of microscopical analyses is a highly time-consuming procedure. The comparison is based on morphological structures of epidermal cells, like the shape of cells, stomata or trichomes. In contrast, the sample preparation for the FT-IR and the subsequent measuring is simple and quickly done. We investigated the diet of Black Grouse (Tetrao tetrix L.) in two study areas with infrared spectroscopic methods comparing summer and winter droppings’ content with plant reference material. The study areas are located in the provinces of Salzburg and Upper Austria, Austria. In our study, samples were measured in the mid- and near-infrared range. We tried to determine the dominating content of faecal samples at species, genera or family level or at least to assign samples to one of four main plants groups (i.e. woody plants, heathers, herbs and grasses). Our results showed a dominance of Larix decidua within the group of woody plants in both areas and, within the group of heathers, a dominance of Calluna vulgaris and Rhododendron hirsutum in one study area. Partially, our results are in marked contrast to other studies conducted in the Alps, as Vaccinium myrtillus was not detected in the samples. For further methodological studies, faecal sampling over larger areas, larger samples of plant reference material (including seeds and other parts of plants at different seasons), taking more samples per dropping and synchronous comparisons of microscopic analyses as well as FT-IR spectroscopy, are recommended.

Are leaf functional traits ‘invariant’ with plant size and what is ‘invariance’ anyway?

Summary Studies of size‐related plant traits have established a suite of mathematical functions describing whole plant investment and allocation. In parallel, studies of plant ‘economic spectra’ have measured the scaling and variance composition of traits related to the major dimensions of both structure and function. Here, we explore the intersection of these two broad areas by exploring the notion that many leaf economic traits are invariant with species differences in adult plant size. Invariant traits are those that do not change with plant size and are invoked as a key simplifying assumption of prominent models that purport to explain the scaling of plant size and metabolism. Unfortunately, leaf trait invariance is neither well defined nor understood and has never been critically evaluated. Using a global plant trait data set, we evaluated whether nine key traits can be considered as effectively invariant as a function of the maximum height of plant species, within and across plant growth forms and within and across broad taxonomic groups. We also examine the influence of habitat, biome and global spatial scales on the size‐relative variance in plant functional traits. We suggest that while invariance is an intuitive concept, an objective statistical definition is elusive. Expanding on ideas drawn from the study of life‐history invariants, we propose five criteria to identify traits that are effectively invariant, depending on the research question. We show that all studied ‘leaf economic spectrum’ (LES) traits approach invariance within and between herbaceous and woody plant groups, angiosperms and gymnosperms, and within most biome and habitat types. Individual leaf area, however, shows a modest increase with plant size, and there are significant shifts in the average LES trait values at a given plant maximum height, among the plant growth forms and taxonomic groups. Our results demonstrate that generally, LES traits show little interspecific variation with maximum plant height, which provides some support for attempts to model plants with ‘average’ leaf properties. Our work also highlights the need for a better understanding of the drivers of leaf size variation within and across individuals, functional groups, clades, biomes and habitats.

Woody Plant Diversity, Evolution, and Ecology in the Tropics: Perspectives from Seasonally Dry Tropical Forests

This review suggests that the ecology and patchy global distribution of seasonally dry tropical forest (SDTF) has distinctively structured the evolutionary history and biogeography of woody plant groups that are confined to it. SDTFs have few widespread woody plant species causing high β-diversity between separate areas of forests. These separate areas contain geologically old, monophyletic clades of endemic plant species that often have geographically structured intraspecific genetic variation. These patterns of diversity, endemism, and phylogeny indicate a stable, dispersal-limited SDTF system. SDTF species tend to belong to larger clades confined to this vegetation, exemplifying phylogenetic niche conservatism, and we argue that this is evidence that the SDTF is a metacommunity (biome) for woody plant clades. That phylogenetic, population genetic, biogeographic, and community ecological patterns differ in woody plants from tropical rain forests and savannas suggests a hypothesis that broad ecological settings strongly influence plant diversification in the tropics.

Long-term trends in atmospheric pollen levels in the city of Thessaloniki, Greece

We examined the long-term trends in pollen atmospheric levels in Thessaloniki, the second largest city of Greece. On the basis of data collected during the period 1987–2005, we estimated trends in the atmospheric pollen levels for the 16 different taxa, each of whose contribution to the total atmospheric pollen concentration was at least 0.5%. We also tested for trends towards earlier, longer or more highly peaked pollen seasons. The salient feature of these data is that the levels of pollen have been increasing; this is true for the majority of the individual taxa examined (12 out of 16) and for their aggregate. On average, the atmospheric pollen concentration is doubling every decade, but for some species the rate is much higher, with doubling times less than 5 years. Among the taxa with the highest rate of long-term trend in atmospheric pollen concentration, four belong to the group of woody plants (Cupressaceae, Quercus, Platanus, Pinaceae) and only one to that of herbs (Urticaceae). For the pollen-season-related attributes (onset, peak, end and duration), there was no systematic tendency and the changes were more nuanced. The observed increase in pollen abundance coincides with a rise in air temperature, which is the only meteorological factor to have experienced a sustained and significant change over the same period in Thessaloniki. Our results suggest that changes in pollen distributions are dominated by increases in pollen production rather than changes in flowering phenology and that several species showing strong trends might serve as bio-indicators of expected climate change. Given that the pollen-producing reservoir around the city has not increased, these results provide further evidence of the impact of climate change on plant biota.

Testing the Value of Six Taxonomic Groups as Biodiversity Indicators at a Local Scale

Abstract: We examined six groups of taxa—woody plants, aquatic and terrestrial herpetofauna, small terrestrial birds, orchids, and Orthoptera—to determine their efficiency as biodiversity indicators in the Dadia Reserve in northern Greece. We investigated the indicator value of each group by examining the degree of congruence of its species‐richness pattern with that of the other groups and the efficiency of its complementary network in conserving the other groups and biodiversity. The two techniques differed in many respects in their outputs, but they both showed woody plants as the best biodiversity indicator. There was in general low congruence in the species richness patterns across the different groups. Significant relationships were found between woody plants and birds, Orthoptera and terrestrial herpetofauna, and birds and aquatic herpetofauna. None of the optimal complementary networks of the groups we examined protected all species of the other groups. Nevertheless, the complementary network of woody plants adequately conserved all groups except orchids. We conclude that the principle of complementarity must be integrated into the methodology of evaluating an indicator. In an applied context, our results provide a scientific background on which to base a biomonitoring program for the Dadia Reserve. In a wider scope, if the group of woody plants prove an adequate biodiversity indicator for other Mediterranean areas as well, this will be important because it will facilitate conservation‐related decisions for the entire Mediterranean region.

Epicormic strand structure in Angophora, Eucalyptus and Lophostemon (Myrtaceae) – implications for fire resistance and recovery

Summary Epicormic bud producing structures in the eucalypts, a large group of woody plants of considerable ecological, horticultural and silvicultural importance, are described here. The outer portion of epicormic strands excised from the bark of large diameter stems of 18 Eucalyptus species, two Angophora species and Lophostemon confertus was examined anatomically in semithin sections. In the inner bark each eucalypt strand usually possessed 5–12 radially orientated strips of tissue of meristematic appearance. The meristem strips were c. 30–50 µm high, 70–110 µm wide and 2000–10 000 µm long, with a lacuna above the meristem surface. Few buds or bud primordia were associated with the strands and the strands appeared to have a reduced regenerative potential in the outer bark. In most angiosperm trees dormant epicormic buds are present in the outer bark, a position where they could be killed by fire. By contrast, in eucalypts the greatest epicormic bud initiation potential is at the level of the vascular cambium, which is protected by the maximum bark thickness. This might explain the pronounced ability of eucalypts to produce bole and branch epicormic shoots after moderate to intense fire.

Representation of vegetation dynamics in the modelling of terrestrial ecosystems: comparing two contrasting approaches within European climate space

Abstract Advances in dynamic ecosystem modelling have made a number of different approaches to vegetation dynamics possible. Here we compare two models representing contrasting degrees of abstraction of the processes governing dynamics in real vegetation. Model (a) (GUESS) simulates explicitly growth and competition among individual plants. Differences in crown structure (height, depth, area and LAI) influence relative light uptake by neighbours. Assimilated carbon is allocated individually by each plant to its leaf, fine root and sapwood tissues. Carbon allocation and turnover of sapwood to heartwood in turn govern height and diameter growth. Model (b) (LPJ) incorporates a ‘dynamic global vegetation model’ (DGVM) architecture, simulating growth of populations of plant functional types (PFTs) over a grid cell, integrating individual‐level processes over the proportional area (foliar projective cover, FPC) occupied by each PFT. Individual plants are not simulated, but are replaced by explicit parameterizations of their growth and interactions. The models are identical in their representation of core physiological and biogeochemical processes. Both also use the same set of PFTs, corresponding to the major woody plant groups in Europe, plus a grass type. When applied at a range of locations, broadly spanning climatic variation within Europe, both models successfully predicted PFT composition and succession within modern natural vegetation. However, the individual‐based model performed better in areas where deciduous and evergreen types coincide, and in areas subject to pronounced seasonal water deficits, which would tend to favour grasses over drought‐intolerant trees. Differences in model performance could be traced to their treatment of individual‐level processes, in particular light competition and stress‐induced mortality. Our results suggest that an explicit individual‐based approach to vegetation dynamics may be an advantage in modelling of ecosystem structure and function at the resolution required for regional‐ to continental‐scale studies.

Representation of vegetation dynamics in the modelling of terrestrial ecosystems: comparing two contrasting approaches within European climate space

1 Advances in dynamic ecosystem modelling have made a number of different approaches to vegetation dynamics possible. Here we compare two models representing contrasting degrees of abstraction of the processes governing dynamics in real vegetation. 2 Model (a) (GUESS) simulates explicitly growth and competition among individual plants. Differences in crown structure (height, depth, area and LAI) influence relative light uptake by neighbours. Assimilated carbon is allocated individually by each plant to its leaf, fine root and sapwood tissues. Carbon allocation and turnover of sapwood to heartwood in turn govern height and diameter growth. 3 Model (b) (LPJ) incorporates a ‘dynamic global vegetation model’ (DGVM) architecture, simulating growth of populations of plant functional types (PFTs) over a grid cell, integrating individual-level processes over the proportional area (foliar projective cover, FPC) occupied by each PFT. Individual plants are not simulated, but are replaced by explicit parameterizations of their growth and interactions. 4 The models are identical in their representation of core physiological and biogeochemical processes. Both also use the same set of PFTs, corresponding to the major woody plant groups in Europe, plus a grass type. 5 When applied at a range of locations, broadly spanning climatic variation within Europe, both models successfully predicted PFT composition and succession within modern natural vegetation. However, the individual-based model performed better in areas where deciduous and evergreen types coincide, and in areas subject to pronounced seasonal water deficits, which would tend to favour grasses over drought-intolerant trees. 6 Differences in model performance could be traced to their treatment of individual-level processes, in particular light competition and stress-induced mortality. 7 Our results suggest that an explicit individual-based approach to vegetation dynamics may be an advantage in modelling of ecosystem structure and function at the resolution required for regional- to continental-scale studies.

Origins and Evolution of Subfam. Maloideae (Rosaceae)

Subfam. Maloideae (x = 17) has been held to be tetraploid since 1931 while later, Sax elaborated by Stebbins, specifically implicated subfam. Spiraeoideae (x = 9) and Amygdaloideae (x = 8) in an allotetraploid ancestry. The allotetraploid theory has gained considerable credibility with many workers on Rosaceae but, although support for it is not unanimous, and it is sometimes ignored, there has never been any attempt at refutation. To date, the theory has depended mainly on chromosome constitution, and, in a rather general way, on the morphological characteristics of the respective taxa. In this paper we review the allotetraploid hypothesis and generally verify it by an extensive character analysis of the Maloideae, Amygdaloideae, and Spiraeoideae. Since no specifically rosoid or quillajoid characters exist in the Maloideae, no candidate near-ancestral genera in subfam. Rosoideae or tribe Quillajeae can be pinpointed. The autapomorphic fruit of the Maloideae-the pome-is derivable from spiraeoid or proto-amygdaloid characters. In a parsimony analysis of a 96 taxa x 36 variable data matrix the phenetic genera were, for the most part, returned as clades, but their placement was to a significant extent, peculiar. The consistency index was extremely low. Furthermore, the addition of only three OTUs resulted in major relocations of some of the genera. We concluded that, in this type of situation, parsimony analysis is not robust, and sought other explanations for the relationships suggested. We favour the idea that several clades of Maloideae originated independently in a highly reticulate system existing shortly after the original allotetraploid cross. This notion of polychotomous early evolution alone, we feel, makes sense of the general correspondence of phenetic genera to cladistic genera, remarkably low consistency index, great instability of the cladogram with respect to changing only a few OTU's, and the manifestly great ability of most maloidean genera to hybridize. Thus, the precise phylogeny of the Maloideae must remain quite unknown until a very different kind of investigation has been successfully conducted. The present paper is one of a series by the authors reviewing generic limits and examining evolutionary pathways in the subfam. Maloideae. We develop the Sax-Stebbins hypothesis on the allotetraploid origin of the Maloideae and seek to define more clearly the characteristics of the original maloid in order to inform the search for evolutionary pathways. The Maloideae are an important group of woody plants containing close to 1000 species and 20-30 genera dependent on circumscription (Phipps et al. 1990). As one of the four subfamilies of the Rosaceae, which is often considered quite pivotal in dicotyledonous evolution, Maloideae have received a great deal of taxonomic and revisionary attention since the time of their first formal recognition by de Jussieu in 1791. However, little of this attention has been explicitly cladistic. Subfamily Maloideae constitutes a natural group of plants, with synapomorphic pome fruit, base chromosome number of x = 17 and an autapomorphic suite of rust parasites (Savile 1979). The widespread occurrence of gameto-

Woody Plants-Evolution and Distribution Since the Tertiary.

Paleobotany has enormously expanded the documentation of fossil plant groups, floras and vegetation types, supporting its conclusions by technically much improved analyses of microfossils (pollen) and anatomical details. An increasing quantity and quality of all these informations from the geosciences is available when we follow the history of the biosphere up to the present. Simultaneously, research from the biosciences on the morphology, ecology, distribution, systematics and evolution of extant vascular plants, and on the ecogeographical differentiation of the vegetation cover of our planet, has made enormous progress. Thus, a synthetic geo- and bioscientific approach becomes more and more feasible and urgent for further advances in the many problems of common concern. A symposium organized by the 'Deutsche Akademie der Naturforscher LEOPOLDINA', attractive to paleo - and neobotanists, stimulated the discussion between specialists of the two disciplines. The main results of the symposium are now presented in this volume: sixteen international contributions outline the current knowledge about the historical differentiation and evolution of woody plant groups and forests, covering the whole biosphere. This survey, from the beginning of the Tertiary up to the present, is a first synthesis of relevant data from the geo- and biosciences.

Paleobotanical evidences of the Tertiary history and origin of the Mediterranean sclerophyll dendroflora

The evolution of important woody plant groups, ancestral to the modern Mediterranean dendroflora, is surveyed. Altogether, the history and phytogeography of 86 fossil species or species-groups is considered. The major part of the Paleomediterranean woody plants appears in Miocene mixed mesophyllous and mesoxerophyllous, evergreen and deciduous forests. The initial formation of basic Mediterranean sclerophyllous woody vegetation types is referred to periods from the Late Sarmatian to the Late Pontian, in geographic areas between 37° and 45° N latitude.