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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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What determines plant species diversity in Central Africa?
Proosdij, Andreas S.J. van - \ 2017
Wageningen University. Promotor(en): M.S.M. Sosef, co-promotor(en): N. Raes; J.J. Wieringa. - Wageningen : Wageningen University - ISBN 9789463436618 - 161
plants - biodiversity - species diversity - species - distribution - biogeography - central africa - biosystematics - tropical rain forests - modeling - planten - biodiversiteit - soortendiversiteit - soorten - distributie - biogeografie - centraal-afrika - biosystematiek - tropische regenbossen - modelleren

Planet Earth hosts an incredible biological diversity. Estimated numbers of species occurring on Earth range from 5 to 11 million eukaryotic species including 400,000-450,000 species of plants. Much of this biodiversity remains poorly known and many species have not yet been named or even been discovered. This is not surprising, as the majority of species is known to be rare and ecosystems are generally dominated by a limited number of common species.

Tropical rainforests are the most species-rich terrestrial ecosystems on Earth. The general higher level of species richness is often explained by higher levels of energy near the Equator (latitudinal diversity gradient). However, when comparing tropical rainforest biomes, African rainforests host fewer plant species than either South American or Asian ones. The Central African country of Gabon is situated in the Lower Guinean phytochorical region. It is largely covered by what is considered to be the most species-rich lowland rainforest in Africa while the government supports an active conservation program. As such, Gabon is a perfect study area to address that enigmatic question that has triggered many researchers before: “What determines botanical species richness?”.

In the past 2.5 million years, tropical rainforests have experienced 21 cycles of global glaciations. They responded to this by contracting during drier and cooler glacials into larger montane and smaller riverine forest refugia and expanding again during warmer and wetter interglacials. The current rapid global climate change coupled with change of land use poses new threats to the survival of many rainforest species. The limited availability of resources for conservation forces governments and NGOs to set priorities. Unfortunately, for many plant species, lack of data on their distribution hampers well-informed decision making in conservation.

Species distribution models (SDMs) offer opportunities to bridge at least partly this knowledge gap. SDMs are correlative models that infer the spatial distribution of species using only a limited set of known species occurrence records coupled with high resolution environmental data. SDMs are widely applied to study the past, present and future distribution of species, assess the risk of invasive species, infer patterns of species richness and identify hotspots, as well as to assess the impact of climate change. The currently available methods form a pipeline, with which data are selected and cleaned, models selected, parameterized, evaluated and projected to other areas and climatic scenarios, and biodiversity patterns are computed from these SDMs. In this thesis, SDMs of all Gabonese plant species were generated and patterns of species richness and of weighted endemism were computed (chapter 4 & 5).

Although this pipeline enables the rapid generation of SDMs and inferring of biodiversity patterns, its effective use is limited by several matters of which three are specifically addressed in this thesis. Not knowing the true distribution limits the opportunities to assess the accuracy of models and assess the impact of assumptions and limitations of SDMs. The use of simulated species has been advocated as a method to systematically assess the impact of specific matters of SDMs (virtual ecologist). Following this approach, in chapter 2, I present a novel method to simulate large numbers of species that each have their own unique niche.

One matter of SDMs that is usually ignored but has been shown to be of great impact on model accuracy is the number of species occurrence records used to train a model. In chapter 2, I quantify the effect of sample size on model accuracy for species of different range size classes. The results show that the minimum number of records required to generate accurate SDMs is not uniform for species of every range size class and that larger sample sizes are required for more widespread species. By applying a uniform minimum number of records, SDMs of narrow-ranged species are incorrectly rejected and SDMs of widespread species are incorrectly accepted. Instead, I recommend to identify and apply the unique minimum numbers of required records for each individual species. The method presented here to identify the minimum number of records for species of particular range size classes is applicable to any species group and study area.

The range size or prevalence is an important plant feature that is used in IUCN Red List classifications. It is commonly computed as the Extent Of Occurrence (EOO) and Area Of Occupancy (AOO). Currently, these metrics are computed using methods based on the spatial distribution of the known species occurrences. In chapter 3, using simulated species again, I show that methods based on the distribution of species occurrences in environmental parameter space clearly outperform those based on spatial data. In this chapter, I present a novel method that estimates the range size of a species as the fraction of raster cells within the minimum convex hull of the species occurrences, when all cells from the study area are plotted in environmental parameter space. This novel method outperforms all ten other assessed methods. Therefore, the current use of EOO and AOO based on spatial data alone for the purpose of IUCN Red List classification should be reconsidered. I recommend to use the novel method presented here to estimate the AOO and to estimate the EOO from the predicted distribution based on a thresholded SDM.

In chapter 4, I apply the currently best possible methods to generate accurate SDMs and estimate the range size of species to the large dataset of Gabonese plant species records. All significant SDMs are used here to assess the unique contribution of narrow-ranged, widespread, and randomly selected species to patterns of species richness and weighted endemism. When range sizes of species are defined based on their full range in tropical Africa, random subsets of species best represent the pattern of species richness, followed by narrow-ranged species. Narrow-ranged species best represent the weighted endemism pattern. Moreover, the results show that the applied criterion of widespread and narrow-ranged is crucial. Too often, range sizes of species are computed on their distribution within a study area defined by political borders. I recommend to use the full range size of species instead. Secondly, the use of widespread species, of which often more data are available, as an indicator of diversity patterns should be reconsidered.

The effect of global climate change on the distribution patterns of Gabonese plant species is assed in chapter 5 using SDMs projected to the year 2085 for two climate change scenarios assuming either full or no dispersal. In Gabon, predicted loss of plant species ranges from 5% assuming full dispersal to 10% assuming no dispersal. However, these numbers are likely to be substantially higher, as for many rare, narrow-ranged species no significant SDMs could be generated. Predicted species turnover is as high as 75% and species-rich areas are predicted to loose many species. The explanatory power of individual future climate anomalies to predicted future species richness patterns is quantified. Species loss is best explained by increased precipitation in the dry season. Species gain and species turnover are correlated with a shift from extreme to average values of annual temperature range.

In the final chapter, the results are placed in a wider scientific context. First, the results on the methodological aspects of SDMs and their implications of the SDM pipeline are discussed. The method presented in this thesis to simulate large numbers of species offers opportunities to systematically investigate other matters of the pipeline, some of which are discussed here. Secondly, the factors that shape the current and predicted future patterns of plant species richness in Gabon are discussed including the location of centres of species richness and of weighted endemism in relation to the hypothesized location of glacial forest refugia. Factors that may contribute to the lower species richness of African rainforests compared with South American and Asian forests are discussed. I conclude by reflecting on the conservation of the Gabonese rainforest and its plant species as well as on the opportunities SDMs offer for this in the wider socio-economic context of a changing world with growing demand for food and other ecosystem services.

Comparative genomics and trait evolution in Cleomaceae, a model family for ancient polyploidy
Bergh, Erik van den - \ 2017
Wageningen University. Promotor(en): M.E. Schranz; Y. van de Peer. - Wageningen : Wageningen University - ISBN 9789463431705 - 106
capparaceae - genomics - polyploidy - evolution - genomes - reproductive traits - flowers - colour - glucosinolates - genetic variation - biosystematics - taxonomy - identification - capparaceae - genomica - polyploïdie - evolutie - genomen - voortplantingskenmerken - bloemen - kleur - glucosinolaten - genetische variatie - biosystematiek - taxonomie - identificatie

As more and more species have been sequenced, evidence has been piling up for a fascinating phenomenon that seems to occur in all plant lineages: paleopolyploidy. Polyploidy has historically been a much observed and studied trait, but until recently it was assumed that polyploids were evolutionary dead-ends due to their sterility. However, many studies since the 1990’s have challenged this notion by finding evidence for ancient genome duplications in many genomes of current species. This lead to the observation that all seed plants share at least one ancestral polyploidy event. Another polyploidy event has been proven to lie at the base of all angiosperms, further signifying the notion that ancient polyploidy is widespread and common. These findings have led to questions regarding the apparent disadvantages that can be observed in a first generation polyploid. If these disadvantages can be overcome however, duplication of a genome also presents an enormous potential for evolutionary novelty. Duplicated copies of genes are able to acquire changes that can lead to specialization of the duplicated pair into two functions (subfunctionalization) or the development of one copy towards an entirely new function (neofunctionalization).

Currently, most research towards polyploidy has focused on the economically and scientifically important Brassicaceae family containing the model plant Arabidopsis thaliana and many crops such as cabbage, rapeseed, broccoli and turnip. In this thesis, I lay the foundations for the expansion of this scope to the Cleomaceae, a widespread cosmopolitan plant family and a sister family of Brassicaceae. The species within Cleomaceae are diverse and exhibit many scientifically interesting traits. They are also in a perfect position phylogenetically to draw comparisons with the much more studied Brassicaceae. I describe the Cleomaceae and their relevance to polyploid research in more detail in the Introduction. I then describe the important first step towards setting up the genetic framework of this family with the sequencing of Tarenaya hassleriana in Chapter 1.

In Chapter 2, I have studied the effects of polyploidy on the development of C4 photosynthesis by comparing the transcriptome of C3 photosynthesis based species Tarenaya hassleriana with the C4 based Gynandropsis gynandra. C4 photosynthesis is an elaboration of the more common C3 form of photosynthesis that concentrates CO2 in specific cells leading to decreased photorespiration by the RuBisCO and higher photosynthetic efficieny in low CO2 environments. I find that polyploidy has not led to sub- or neofunctionalization towards the development of this trait, but instead find evidence for another important phenomenon in postpolyploid evolution: the dosage balance hypothesis. This hypothesis states that genes which are dependent on specific dosage levels of their products will be maintained in duplicate; any change in their function would lead to dosage imbalance which would have deleterious effects on their pathway. We show that most genes involved in photosynthesis have returned to single copy in G. gynandra and that the changes leading to C4 have mostly taken place at the expression level confirming current assumptions on the development of this trait.

In Chapter 3, I have studied the effects of polyploidy on an important class of plant defence compounds: glucosinolates. These compounds, sometimes referred to as ‘mustard oils’, play an important role in the defence against herbivores and have radiated widely in Brassicaceae to form many different ‘flavors’ to deter specific herbivores. I show that in Cleomaceae many genes responsible for these compounds have benefited from the three rounds of polyploidy that T. hassleriana has undergone and that many duplicated genes have been retained. We also show that more than 75% is actively expressed in the plant, proving that the majority of these duplications has an active function in the plant.

Finally, in Chapter 4 I investigate a simple observation made during experiments with T. hassleriana in the greenhouse regarding the variation in flower colour between different individuals: some had pink flowers and some purple. Using LC-PDA mass spectrometry we find that the two colours are caused by different levels of two anthocyanin pigments, with cyanidin dominating in the purple flowers and pelargonidin being more abundant in pink flowers. Through sequence comparison and synteny analysis between A. thaliana and T. hassleriana we find the orthologs of the genes involved in this pathway. Using a Genotyping by Sequencing method on a cross between these two flower colours, we produce a collection of SNP markers on the reference genome. With these SNPs, we find two significant binary trait loci, one of which corresponds to the location of the F3’H ortholog which performs the conversion of a pelargonidin precursor to a cyanidin precursor.

In the General Conclusion, I combine all findings of the previous chapters and explain how they establish part of a larger species framework to study ancient polyploidy in angiosperms. I then put forth what these findings can mean for possible future research and the directions that are worth to be explored further.

Genetic diversity and difference within and between bitter and sweet African bush mango trees (Irvingia spp., Irvingiaceae) in West and Central Africa
Vihotogbé, R. ; Berg, R.G. van den; Missinhoun, A.A. ; Sinsin, B. ; Sosef, M.S.M. - \ 2015
African journal of biotechnology 14 (2015)45. - ISSN 1684-5315 - p. 3062 - 3074.
bush mango - biosystematics
Economically important food tree species in sub-Saharan Africa should be domesticated to enhance their production within agro forestry systems. The African bush mango trees (Irvingia species) are highly preserved and integrated in agro forestry systems in tropical Africa. However, the taxonomic debate related to the species or varietal status of the bitter and sweet fruited African bush mango trees hinders their domestication process and rational use. Amplified fragment length polymorphisms (AFLPs) and chloroplast simple sequence repeats (cpSSRs) were used in this study to assess the genetic diversity of African bush mango trees and to test the distinction between bitter and sweet fruited trees, sampled across Togo, Benin, Nigeria and Cameroon. Both the AFLPs and cpSSRs showed low genetic diversity for the Dahomey Gap bitter trees population. This is due to the higher fragmentation and the continuous reduction of this small sized population occurring in a limited forest ecosystem. The higher polymorphism and genetic diversity of the sweet mango tree populations in Benin and Togo showed the effects of domestication of materials of different geographical origin coupled with the frequent long distance transfer of genetic materials. When used separately, the AFLPs and cpSSRs failed to consistently discriminate the populations and type of trees. From the combined dataset, both markers differentiated geographically recognizable groups; bitter from sweet mango trees. However, Nigerian sweet mango trees clustered with the bitter ones. The suitability of AFLPs and cpSSRs to test our hypotheses within Irvingia needs to be thoroughly reassessed.
Systematics, evolution and historical biogeography of the family Ochnaceae with emphasis on the genus Campylospermum
Bissiengou, P. - \ 2014
Wageningen University. Promotor(en): Marc Sosef, co-promotor(en): Lars Chatrou; L. Ngok Banak. - Wageningen : Wageningen University - ISBN 9789462572225 - 357
ochnaceae - biosystematiek - taxonomie - evolutie - biogeografie - plantengeografie - fylogenie - taxonomische revisies - fylogenetica - ochnaceae - biosystematics - taxonomy - evolution - biogeography - phytogeography - phylogeny - taxonomic revisions - phylogenetics

Abstract

Ochnaceae s.l. is a family of trees, shrubs or rarely herbs widely distributed in tropical and subtropical forests and savannas of the Old and New World, and has about 500 species in 32 genera. The family is divided into three subfamilies: Medusagynoideae, Quiinoideae and Ochnoideae. We have provided, for the first time, a nearly complete molecular phylogenetic analysis of Ochnaceae s.l. resolving most of the phylogeny backbone of the family using five DNA regions. Based on this, dating analyses were performed using a secondary calibration, and relaxed molecular clock models. The historical biogeography of Ochnaceae s.l. was reconstructed using Dispersal-Vicariance Analysis and Bayesian Binary MCMC. The Neotropics were inferred as being the geographical origin of the family and the Old World was most likely colonized via the North Atlantic Land Bridge during a period when climatic conditions allowed establishment of a boreotropical flora. A full taxonomic revision of the continental African species of the genus Campylospermum has been prepared and additional historical biogeographic analyses were performed with a focus on the genus Campylospermum.

Conserving the genetic diversity of Bolivian wild potatoes
Cadima Fuentes, X. - \ 2014
Wageningen University. Promotor(en): Marc Sosef, co-promotor(en): Ronald van den Berg; Rob van Treuren. - Wageningen : Wageningen University - ISBN 9789462571686 - 229
solanum - bolivia - wilde verwanten - gewassen - genetische bronnen van plantensoorten - conservering - ex-situ conservering - in-situ conservering - genenbanken - biosystematiek - genetische diversiteit - verzamelmissies - solanum - bolivia - wild relatives - crops - plant genetic resources - conservation - ex situ conservation - in situ conservation - gene banks - biosystematics - genetic diversity - collecting missions

Abstract thesis Ximena Cadima Fuentes (to be defended on 8 Dec 2014):

Conserving the genetic diversity of Bolivian wild potatoes

The wild relatives of potatoes (Solanum sect. Petota) form the genetic reservoir for the improvement of the cultivated potato. Bolivia harbours 39 wild taxa of these wild potatoes, 21 of which are endemic species. This study aimed to evaluate to what level the current ex situ and in situ management efforts have conserved the genetic diversity of Bolivian wild potato species, and what recommendations can be formulated for improvement.

The current conservation status of Bolivian endemic wild potato species was assessed using both the globally accepted IUCN criteria and a methodology developed within the framework of the UNEP/GEF-Crop Wild Relative Project (CWR Project). These two methods led to different estimates of threat status for some of the species. Spatial analysis allowed to distinguish eight priority areas for in situ conservation of the 21 Bolivian endemic wild potato species. These areas represent a high concentration of endemic species and have a relatively low level of threat, but only one of them has a conservation status. This is a first step to direct the conservation efforts for wild potato species.

The genetic stability and diversity of material from different species under ex situ management was evaluated using microsatellite markers. The analysis was performed on accessions that went through a process of seed regeneration and multiplication during ex situ conservation. Genetic changes between different generations of ex situ germplasm were observed for the majority, but not all, of the investigated species. Potential causes of these changes include genetic drift and contamination resulting from human error during regeneration. The populations generated under ex situ conditions were also compared with re-collected in situ populations from the same location or area as the original collection. The results showed highly significant differences in all cases. Potential causes for these differences are changes during ex situ maintenance, sampling effects during collecting and in situ genetic change over time.

The integrated conservation of Bolivian wild potatoes requires a combination of in situ and ex situ activities. The principle recommendation for the in situ conservation is to move from a passive to an active approach, where conservation areas are prioritized, conservation plans are designed according to the type of area (protected area or agro-ecosystem) and local stake holders are involved. To make sure that ex situ material provides a good representation of the in situ genetic variability, regular re-collecting of species with few accessions (and therefore less variability), endangered in situ, and with known or potential favorable traits is necessary. Gene bank management procedures should follow the FAO gene bank standards and this should be monitored by a national body responsible for genetic resources. And finally, periodic monitoring of the genetic integrity should be implemented as part of good practices during regeneration procedures in order to detect possible changes and to help combat human errors.

Searching for species, relationships and resistance in Solanum section Petota
Jacobs, M.M.J. - \ 2008
Wageningen University. Promotor(en): Marc Sosef; Richard Visser, co-promotor(en): Ben Vosman; Ronald van den Berg. - [S.l.] : S.n. - ISBN 9789085852049 - 187
solanum - taxonomie - plantkunde - taxa - soorten - moleculaire taxonomie - biosystematiek - fylogenetica - ziekteresistentie - phytophthora infestans - genexpressieanalyse - solanum - taxonomy - botany - taxa - species - molecular taxonomy - biosystematics - phylogenetics - disease resistance - phytophthora infestans - genomics
AFLP markers support separation of Solanum nodiflorum from Solanum americanum sensu strictio (Solanaceae)
Manoko, M.L.K. ; Berg, R.G. van den; Feron, R.M.C. ; Weerden, G.M. van der; Mariani, C. - \ 2007
Plant Systematics and Evolution 267 (2007)1-4. - ISSN 0378-2697 - p. 1 - 11.
genetic-relationships - l. - biosystematics - relatives - homology - barley - wild
This study was aimed at examining the relationships between the African material of Solanum americanum (also designated as S. nodiflorum), accessions of this taxon from other geographical areas, and American S. americanum using AFLP markers. 96 individuals representing 39 accessions of S. americanum sensu lato and related diploid species from the widest possible geographical range, and one accession of S. dulcamara (as outgroup) were used. The AFLP results suggested that American S. americanum differs from S. nodiflorum and that the material investigated in this study can be assigned to three different species: S. americanum sensu stricto, S. nodiflorum and a Solanum species from Brazil. These species can be differentiated based on a combination of floral and fruit characteristics.
Het snuitkevergenus Larinus in Nederland, met Larinus turbinatus als nieuwe soort voor de fauna (Coleoptera: Curculionidae).
Heijerman, Th. - \ 2007
Nederlandse Faunistische Mededelingen 26 (2007). - ISSN 0169-2453 - p. 1 - 16.
larinus - biologische bestrijding - biosystematiek - curculionidae - coleoptera - zoögeografische gebieden - biogeografie - verspreiding - dierecologie - biological control - biosystematics - zoogeographical regions - biogeography - dispersal - animal ecology
Met enige regelmaat worden nieuwe kevers voor de Nederlandse fauna gerapporteerd. In deze bijdrage wordt Larinus turbinatus voor het eerst gemeld. Deze soort werd in 2004 voor het eerst in ons land aangetroffen en is sindsdien op diverse locaties waargenomen en verzameld. Het is verleidelijk om de komst van weer een nieuwe soort te verklaren op grond van het veranderende klimaat. Maar gezien de Europese verspreiding lijkt het in dit geval geen aannemelijke verklaring
Evolutie in de systematiek
Sosef, M.S.M. - \ 2007
Wageningen : Wageningen Universiteit - 26
biosystematiek - taxonomie - evolutie - biodiversiteit - openbare redes - biosystematics - taxonomy - evolution - biodiversity - public speeches
Contribution to the biosystematics of Celtis L. (Celtidaceae) with special emphasis on the African species
Sattarian, A. - \ 2006
Wageningen University. Promotor(en): Jos van der Maesen, co-promotor(en): Freek Bakker. - [S.l. ] : S.n. - ISBN 9085044456 - 142
celtis - ulmaceae - biosystematiek - soorten - taxonomie - plantenmorfologie - fylogenie - taxonomische revisies - biologische naamgeving - moleculaire taxonomie - afrika - celtis - ulmaceae - biosystematics - species - taxonomy - plant morphology - phylogeny - taxonomic revisions - biological nomenclature - molecular taxonomy - africa
Plant species-level systematics : New perspectives on pattern & process
Bakker, F.T. ; Chatrou, L.W. ; Gravendeel, B. ; Pelser, P.B. - \ 2005
Liechtenstein : A.R.G. Gantner Verlag (Regnum vegetabile vol. 143) - ISBN 3906166392 - 348
planten - taxonomie - biosystematiek - soorten - evolutie - fylogenetica - soortvorming - genomen - plants - taxonomy - biosystematics - species - evolution - phylogenetics - speciation - genomes
Biosystematic studies on Brassicaceae (Cruciferae) in Egypt
Abdel Khalik, K.N.E. - \ 2002
Wageningen University. Promotor(en): L.J.G. van der Maesen; M.N. El Hadidi. - S.l. : S.n. - ISBN 9789058086853 - 278
brassicaceae - numerieke taxonomie - biosystematiek - plantengeografie - fylogenetica - plantenmorfologie - zaden - stuifmeel - egypte - brassicaceae - numerical taxonomy - biosystematics - phytogeography - phylogenetics - plant morphology - seeds - pollen - egypt

The present work deals with a systematic investigation of 45 taxa belonging to 23 genera of the tribes Arabideae, Euclidieae, Hesperideae, Lunarieae, Matthioleae and Sisymbrieae of the family Brassicaceae from Egypt. This work is largely based on herbarium material received on loan from B, BM, BR, E, HUJ, K, KSU, L, LY, NMGM, OXF & FHO and W, and collections kept in the following herbaria; B, CAI, CAIM, WAG and Sohag University Herbarium (SHG, proposed abbreviation). In addition, fresh material of most of the taxa was studied and field observations were made from several localities in Egypt.

Chapter 1 describes the family as a whole, presenting a historical review, its phytogeography, uses and economic importance, an outline of the thesis, aims and general objectives.

Chapter 2 deals with the materials and methods used in this chapter. A full discussion for all morphological characters is provided; systematic treatment, based on macro-characters such as habit, leaf, floral, fruit, embryo and seed and micro-characters of trichomes. An artificial key applies the most reliable characters for the distinction of the genera.

In the systematic treatment 45 taxa are recognized, presenting up-to-date nomenclature, literature citations, type specimens and their locations, synonyms, specimens examined, and distribution maps.

Some taxonomic and nomenclature problems in Rorippa, Neslia, Eremobium, Malcolmia, Matthiola, Arabidopsis and Neotorularia are discussed and changes proposed.

Chapter 3 presents macro-morphological characters of the seeds such as seed shape, colour, size, radicle, and micro- morphological characters by (SEM examination) of the epidermal cell shape, anticlinal boundaries, the outer periclinal cell wall and relief of outer cell walls are presented. Three types of basic anticlinal cell wall boundaries are recognized and, six different shapes of the outer periclinal cell wall are described. A key for the identification of the investigated taxa based on seed characters is provided.

Chapter 4 deals with morphological characters of the pollen grains using SEM. In general the pollen morphology varies within a narrow range. The pollen grains are tricolpate. The shape varies from prolate spheroidal, subprolate to prolate. Three pollen types can be distinguished based on the size of lumina. The exine ornamentation of pollen grains varies between genera within tribes and between species within the same genus. The exine ornamentation of pollen was found useful to distinguish between closely related genera.

Chapter 5 deals with the systematics of the tribes of the Brassicaceae, by means of numerical analysis based on sixty-two morphological characters, including vegetative parts, pollen grains and seeds. Morphological characters have been analyzed using two types of analyses: firstly, we performed a cluster analysis using average taxonomic distance and UPGMA clustering (procedures SIMINT, SAHN, and TREE). Secondly, we performed a principal coordinates analysis (PCO), using the product-moment correlation as a coefficient. The procedures STAND and SIMINT were used to calculate the distance matrix, the procedures EIGEN, PROJ, and MXPLOT to perform the PCO. Four main groups are recognised: Lunarieae, Euclidieae, Matthioleae and a mixed group. Representatives of these groups cluster together based on characters with high factor loading in the PCO analysis. The tribe Euclidieae is the most homogeneous group, and the tribe Arabideae is the most heterogeneous and probably of polyphyletic origin.

Chapter 6 deals with phylogenetic relationships of 83 species belonging to 39 genera of tribes Brassiceae, Alysseae, Arabideae, Euclidieae, Hesperideae, Lepidieae, Lunarieae, Matthioleae and Sisymbrieae. In total 44 species belonging to 28 genera from Egypt were investigated using nucleotide sequences variation of the chloroplast matK gene to assess relationships among genera within tribe and tribes within the family. The topology of Jackknife, parsimony analysis, and Maximum Likelihood trees are largely in agreement. The analysis indicates that tribes Arabideae, Sisymbrieae, Hesperideae, and Lepidieae are polyphyletic.

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