High Levels Of Phenotypic Diversity Research Articles

Agromorphological and Physiological Performance of Ethiopian Common Bean (Phaseolus vulgaris L.) Genotypes under Different Agroecological Conditions.

The objectives of this study were to assess the agronomic performance of common bean genotypes, previously selected for their response to infestation, by Mexican bean weevil and to identify promising lines that can be used as parents in a downstream breeding program. Field experiments were conducted using 144 genotypes under three different agro-ecologies in an unbalanced incomplete block design with three replications. Data on 15 agro-morphological traits were collected, and multivariate methods were used to examine the patterns of variation among the genotypes. The genotypes revealed a high level of phenotypic diversity for all agronomic traits. Six principal components, which contributed 84% of the total variation among the genotypes, were identified. The 15 agro-morphological traits classified the genotypes into three distinct major clusters and sub-clusters. The clustering patterns of the genotypes were according to the seed size, whereby the small and medium beans were distinctly separated from the large-seeded beans. The study established the existence of considerable genetic variations among common bean genotypes. Unique genotypes, such as Nasir, Awash Melka, and RAZ-36 from Cluster I, RAZ-2, RAZ-11, and RAZ-42 from Cluster II, and SER-125, SCR-15, MAZ-200, MAZ-203, and RAZ-120 from Cluster III, were selected based on their distinct agronomic performance. The selected genotypes could be useful for the common bean breeding program.

Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River.

Rainbow Trout, Oncorhynchus mykiss, exhibit high levels of phenotypic diversity leading to the recognition of numerous subspecies. A major distinction among Rainbow Trout subspecies exists between Coastal Rainbow Trout (O. m. irideus), which occurs west of the Cascade and Sierra Nevada mountain ranges, and interior Redband Trout (O. mykiss sspp.), largely distributed to the east. Interior Redband Trout are composed of three primary lineages and can share various outward, anatomical or physiological characteristics that are often symplesiomorphies or examples of convergence. We examine high-throughput DNA sequence data from Sacramento Redband Trout O. m. stonei from the Upper Pit and Upper McCloud Rivers along with representatives of Rainbow Trout and Golden Trout lineages to clarify the composition and relationships of the Sacramento Redband Trout. We find O. m. stonei to be polyphyletic, divided between populations in the Pit River and the Upper McCloud River. Redband Trout obtained from the Pit River are most-closely related to Great Basin Redband Trout O. m. newberrii and to fish of the Warner Lakes Basin and Surprise Valley within the O. m. newberrii lineage. The type specimen of O. m. stonei, collected from the Lower McCloud River, is phenotypically similar to Great Basin Redband Trout. We find as well that the isolated populations of trout in the Upper McCloud River Basin represent a lineage of Rainbow Trout now restricted to that region, are monophyletic and are not most closely related to the interior Redband Trout lineages of O. m. newberrii or O. m. gairdnerii. Furthermore, they are not represented by the type specimens of O. m. stonei or O. m. shasta. Consequently, we formally describe the McCloud River Redband Trout O. mykiss calisulat, new subspecies.

Weak population differentiation and high diversity in Salsola tragus in the inland Pacific Northwest, USA

Salsola tragus is a widespread and problematic weed of semi-arid wheat production globally, and in the inland Pacific Northwest region of the USA. The species exhibits high levels of phenotypic diversity across its range and, at least in California USA, previous work has described cryptic diversity comprising a multi-species complex. Such cryptic diversity could suggest the potential for a differential response to management inputs between groups, and have important implications for the spread of herbicide resistance or other adaptive traits within populations. We used a genotyping-by-sequencing approach to characterize the population structure of S. tragus in the inland Pacific Northwest. Our results indicated that the population in this region is comprised of a single, tetraploid species (S. tragus sensu latu) with weak population structure on a regional scale. Isolation-by-distance appears to be the primary pattern of structure, but an independent set of weakly differentiated clusters of unknown origin were also apparent, along with a mixed mating system and high levels of largely unstructured genetic diversity. Despite considerable phenotypic variability within S. tragus in the region, agronomic weed managers can likely consider it as a single entity across the region, rather than a collection of cryptic subgroups with possible differential responses to management inputs or agroecosystem conditions. A lack of strong barriers to migration and gene flow mean that adaptive traits, such as herbicide resistance, can be expected to spread rapidly through populations across the region. © 2022 Society of Chemical Industry.

Genetic diversity of wild grape hyacinth (Muscari neglectum Guss. ex Ten.) germplasm with ornamental potential in the central region of Iran

Grape hyacinth (Muscari neglectum Guss ex Ten.) is one of the economically important species that can be cultivated as an ornamental crop as well as in pharmaceutical, food, and dyeing industries. In the present study, a total of 140 wild accessions of this species from central regions of Iran were evaluated using 29 morphological characteristics. Significant phenotypic variations were observed among the accessions; especially desirable variations were detected for commercial traits such as peduncle length, peduncle diameter, length and width of leaf, inflorescence length, inflorescence density, floral scent, and bulblet number. The highest variability corresponded to floral scent, bulblet number, inflorescence shape, peduncle color, and inflorescence color. Coefficient of variation (CV) was the lowest for bulb length /bulb diameter, floret length, bulb diameter, and bulb length. Peduncle length, the most important feature of cut flower, varied from 7.5 to 25.2 cm with an average of 14.7. Bottommost leaf length ranged from 5.8 to 30 cm, while bottommost leaf width varied from 1 to 6 mm. Inflorescence length varied from 6 to 37 mm with an average of 19, while inflorescence diameter ranged from 1 to 16 mm. Senjegan-8 accession with the highest values for inflorescence length, inflorescence density, and rate for the length of peduncle was one of the superior accessions. According to principal component analysis (PCA), the first seven components of data accounted for 70.92% of the total variance. Scatter plot showed high level of phenotypic diversity among the studied accessions. Some of the superior accessions such as Rudbaran-8, Rudbaran-20, Rudbaran-45, and Rudbaran-56 were separated from others in scatter plot and characterized by the highest values for inflorescence density, bulblet number, bulb length, and bulb diameter. According to ornamental potential, five accessions, including Senjegan-8, Rudbaran-8, Rudbaran-20, Rudbaran-45, and Rudbaran-56 can be utilized in breeding programs.

Pomegranate morpho-chemodiversity: computational investigations based on in-vivo and in-vitro screening

Pomegranate tree is cultivated since ancient times in Morocco, where a high genetic diversity is hosted mainly in traditional agroecosystems. Over the past decade, it regained importance through extension of cultivated area, but remains thus far little valued. To date, its genetic variability and chemodiversity have gone unheeded for many reasons, some of which are related to previous agricultural strategies. In this context, the present study aimed to screen an ex-situ collection of seven local cultivars and seven exotic varieties with regard to 50 fruit morphometric and biochemical descriptors. The results showed statistically significant variability within accessions (p < 0.01), based on all aforementioned traits, except for seed weight, with coefficients of variation greater than 49%. This indicated a high level of phenotypic diversity among the studied genetic pool. The 3D scatter plot built based on the principal component analysis displayed an interesting discrimination with regard to the genotypes' geographic origins with a total variance of about 50%. According to morphometric based-heatmap, four main clusters were identified distinguishing the typicality of some local cultivars compared to exotic varieties, mainly ‘Sefri’, ‘Bzou’, ‘Chioukhi’ and ‘Djeibi’. Traits having the highest impact on discrimination between accessions were, by order of importance, fruit weight and its dimensions, juice yield, aril yield, single aril diameter, soluble sugars (glucose and fructose) along with contents in some organic acids, including citric, palmitic, linoleic and malic acids. Potential statistically significant correlations were spotted through bi-dimensional heatmap analysis, particularly between the fruit size, shape and peel traits along with some biochemical attributes. As many areas of the species chemodiversity and functional properties are still needed to be investigated further, the results of the present study are of great interest for the species valorization and for breeding programs.

Among-individual diet variation within a lake trout ecotype: Lack of stability of niche use.

In a polyphenic species, differences in resource use are expected among ecotypes, and homogeneity in resource use is expected within an ecotype. Yet, using a broad resource spectrum has been identified as a strategy for fishes living in unproductive northern environments, where food is patchily distributed and ephemeral. We investigated whether specialization of trophic resources by individuals occurred within the generalist piscivore ecotype of lake trout from Great Bear Lake, Canada, reflective of a form of diversity. Four distinct dietary patterns of resource use within this lake trout ecotype were detected from fatty acid composition, with some variation linked to spatial patterns within Great Bear Lake. Feeding habits of different groups within the ecotype were not associated with detectable morphological or genetic differentiation, suggesting that behavioral plasticity caused the trophic differences. A low level of genetic differentiation was detected between exceptionally large‐sized individuals and other piscivore individuals. We demonstrated that individual trophic specialization can occur within an ecotype inhabiting a geologically young system (8,000–10,000 yr BP), a lake that sustains high levels of phenotypic diversity of lake trout overall. The characterization of niche use among individuals, as done in this study, is necessary to understand the role that individual variation can play at the beginning of differentiation processes.

Unraveling the diversification and systematic puzzle of the highly polymorphicPsammobates tentorius(Bell, 1828) complex (Reptilia: Testudinidae) through phylogenetic analyses and species delimitation approaches

The high level of phenotypic diversity in southern African tent tortoises (Psammobates tentorius complex) has for decades prevented systematists from developing a stable taxonomy for the group. Here, we used a comprehensive DNA sequence dataset (mtDNA: Cytb, ND4, ND4 adjacent tRNA-His, and tRNA-Ser, 12S, 16S; and nDNA: PRLR gene) of 455 specimens, and the latest phylogenetic and species delimitation analytical procedures, to unravel the long-standing P. tentorius complex systematic puzzle. Our results for mtDNA and nDNA were incongruent, with the poorly supported nDNA phylogeny differentiating the three recognized subspecies, and showing potential hybridization in some regions. In contrast, the concatenated mtDNA phylogeny identified seven operational taxonomic units, with strong support. Clades 1, 4, 5, and 7 corresponded to tortoises identified as P. t. tentorius, clade 3 to P. t. trimeni, and clades 2 and 6 to P. t. verroxii. Our analyses showed conflicting topologies for the placement of C6 (P. t. verroxii north of the Orange River), with stronger support for it being sister to C2 + C3 than to the other clades. Clades 1, 2, and 6 had significantly higher genetic diversity than clades 3, 4, 5, and 7, perhaps because these clades inhabit substantially larger areas. The potential for future cladogenic radiations seems high in C1 and C6, particularly in C6 for which the within-clade diversification level was highest. Further research involving microsatellite DNA, phylogeographic evaluations, and morphological variation among clades is crucial for understanding the adaptive radiation of the P. tentorius complex and for modifying their taxonomy.

Assessment of genetic diversity in Moroccan fig (Ficus carica L.) collection by combining morphological and physicochemical descriptors

There are not many exhaustive works emphasizing the amount of genetic diversity based on multivariate analysis of a large sample of fig (Ficus carica L.) cultivars in Morocco. In this study, 96 local and 44 introduced fig cultivars were assessed using 41 descriptors. The studied genotypes exhibited a highly significant variability based on morphological, colorimetric and physicochemical traits. Most of characters showed a high coefficient of variations (> 30%) revealing a high level of phenotypic diversity among the genotypes. Principal component analysis showed that the first 10 components explained 60.26% of the total inertia. Fruit weight, caliber, stalk, neck size, fruit shape, and skin color coordinates contributed to most of the total variation. Matrix of correlations showed significant positive and negative correlations among variables particularly fruit sizes, shape and skin color. Cluster analysis using the Unweighted Pair Group Method with Arithmetic Averages procedure for studied accessions revealed two major clusters and five subclusters. Principal component analysis scatter plot expressed a low level of variance compared to the cluster. It confirmed the same classification of the fig accessions, where fruit dimensions and skin color coordinates were the most discriminant descriptors. The results highlight a high phenotypic diversity within studied fig germplasm, which is probably more genetically related. The accessions panel can be recognized as an important gene pool for future breeding programs. The present study is of importance for planning fig genetic resources inventory, preserving the existing genetic variability and establishing national collections.

Smart forage selection could significantly improve soil health in the tropics

The use of tropical grasslands to graze livestock is of high economic importance. Declining grassland soil health leads to reduced sustainability of livestock systems. There are high levels of phenotypic diversity amongst tropical forage grasses. We hypothesise that this variation could lead to significant differences in soil health and that selection of forage cultivars to improve soil health could improve the sustainability of livestock production. We measured and compared key soil health metrics (soil organic carbon (SOC) concentration and sugar / alkane composition, aggregate stability, friability, litter decomposition rates, microbial community composition) under four tropical forage varieties (Brachiaria hybrid cv Mulato (BhMulato), B. humidicola cv Tully (CIAT679; Bh679), B. humidicola cv CIAT16888 (Bh16888), and Panicum maximum CIAT 6962 (Pmax)) and a bare soil control, there was a significant difference in soil aggregate stability, friability and SOC concentration between the forage varieties with soil under Bh679 and Bh16888 tending to have greater aggregate stability, friability and SOC concentrations compared to the soil under BhMulato and Pmax. We identified significant spatial variation in soils under BhMulato and Pmax due to their tussock forming growth habit; when compared to soil from adjacent to the tussocks, soil from the gaps between tussocks had significantly reduced aggregate stability under both species, significantly reduced friability under Pmax and significantly reduced SOC under BhMulato. We found limited impact of forage variety on soil microbial community composition, litter decomposition rates or soil alkane and sugar concentrations.

Morphological and pomological characterization of edible fig ( Ficus carica L.) to select the superior trees

Abstract Fig (Ficus carica L.) is one of the oldest traditional crops and sacred fruit tree widely present in the world. In the present investigation, the morphological and pomological variability of edible fig genotypes belonging to the Smyrna-type was evaluated from Estahban region located in Fars province in Iran. The studied genotypes exhibited significant variability in the characteristics analyzed and most of the measured traits showed the coefficient of variations (CV) more than 20.00%, revealing a high level of phenotypic diversity among the genotypes. Leaf length varied from 62.20 to 138.00 mm, while leaf width ranged from 41.00 to 153.00 mm. Ripening time ranged between very-early and late. The dried fruit weight ranged from 1.86 to 7.15 g and most of the genotypes showed high fruit quality. Simple correlation coefficient analysis revealed significant correlations among the variables measured. Dried fruit weight was positively correlated with leaf density, leaf dimensions, dried fruit length and dried fruit width. Cluster analysis revealed grouping of genotypes into two main clusters, where cluster II contained a large number of genotypes. While most of the genotypes studied showed high potential, nine genotypes were superior in terms of the fruit characters and are valuable gene pools. Further and future breeding programs with these genotypes can provide the better-quality cultivars. The results of the current work are framed in the context of a proper management of fig genetic resource.

Evolution of joint cooperation under phenotypic variations

Effects of phenotypic variation on the species-environment systems and the evolution of cooperation under prescribed phenotypic diversity have been well addressed respectively. Interspecies interactions in the context of evolvable phenotypic diversity remain largely unconsidered. We address the evolutionary dynamics by considering evolvable phenotypic variations under group interactions. Each individual carries a capacitor of phenotypes and pays a cost proportional to its volume. A random phenotype from the capacitor is expressed and the population is thus divided into subpopulations. Group interactions happen in each of these subpopulations, respectively. Competition is global. Results show that phenotypic diversity coevolves with cooperation under a wide range of conditions and that tradeoff between expanding capacitor and rising cost leads to an optimal level of phenotypic diversity best promoting cooperation. We also find that evolved high levels of phenotypic diversity can occasionally collapse due to the invasion of defector mutants, suggesting that cooperation and phenotypic diversity can mutually reinforce each other.

Monitoring Fungicide Sensitivity Levels and Mycelial Compatibility Groupings of Sclerotium rolfsii Isolates from Florida Peanut Fields

ABSTRACT Sclerotium rolfsii, the causal agent of peanut stem rot, is a diverse pathogen that has exhibited decreases in sensitivity to fungicides in areas where they are frequently applied. To better understand this pathogen's diversity and its response to various fungicides in Florida, a monitoring survey was done to examine isolates from several peanut producing areas using morphological characteristics, mycelial compatibility groupings and fungicide sensitivity profiles. A high level of morphological diversity was observed among a small number (N = 15) of isolates which was affirmed by both Shannon-Weiner (E = 0.812) and Simpson's (D = 0.280) indices. However, despite this high level of diversity, fungicide sensitivity of these isolates to flutolanil (EC50 = 0.031 ppm) and tebuconazole (EC50 = 0.008 ppm) appears to remain relatively unchanged when compared to a previous baseline study. Utilizing a small number of isolates, this monitoring survey indicated the EC50 values for the products azoxystrobin (EC50 = 0.050 ppm), prothioconazole (EC50 = 0.213 ppm), penthiopyrad (EC50 = 0.016 ppm) and solatenol (EC50 = 0.005 ppm). A trend for hormesis was also noted in this survey (e.g. flutolanil), but further research is necessary to better understand sub-lethal fungicide dose effects on increasing mycelial growth. It is apparent from these results that despite the high levels of phenotypic diversity in S. rolfsii populations, current fungicide management practices should remain effective for disease control.

Revisiting historical Khoe-San skeletal remains in European collections: A search for identity through craniometric analysis

As the identity of a large number of Khoe-San skeletal material in European collections recently came into question during its documentation, a re-evaluation of the remains by employing a non-invasive method such as craniometrics was done to investigate the biological affinity. For this purpose, gene flow and population diversity present within the group, as well as between the study sample (N=63) and other modern and historic population groups from southern, central and east Africa were explored. Available comparative groups included the historic Khoe-San from Riet River (N=31), the Sotho-Tswana from southern Africa (N=61), the Basuku from central Africa (N=66) and the Bahutu (N=53) and Teita (N=24) from east Africa. Ten craniometric variables were selected and used to perform population structure analysis based on model bound quantitative genetics and multiple discriminant function analysis (MDA). Quantitative genetic distances revealed that the Khoe-San sample was closest to the Riet River group. Residual variance analysis performed on two-sample subsets of the Khoe-San group (Cape KS and Various KS) showed a higher level of heterogeneity in the Cape KS than seen in the Khoe-San from various other areas in southern Africa. MDA revealed that Khoe-San intra-sample variance is relatively high, with 44% of the sample (sexes pooled) classified into the Riet River group. The remaining individuals were classified (in decreasing order) into Bahutu (24%), Basuku (24%) and Sotho-Tswana (8%). Although the Khoe-San specimens are closest to the Riet River group, they are clearly not homogenous. Their high level of phenotypic diversity most likely originated from a complex population history involving many group interactions driven by social and political marginalization.

Coevolutionary dynamics of phenotypic diversity and contingent cooperation.

Phenotypic diversity is considered beneficial to the evolution of contingent cooperation, in which cooperators channel their help preferentially towards others of similar phenotypes. However, it remains largely unclear how phenotypic variation arises in the first place and thus leads to the construction of phenotypic complexity. Here we propose a mathematical model to study the coevolutionary dynamics of phenotypic diversity and contingent cooperation. Unlike previous models, our model does not assume any prescribed level of phenotypic diversity, but rather lets it be an evolvable trait. Each individual expresses one phenotype at a time and only the phenotypes expressed are visible to others. Moreover, individuals can differ in their potential of phenotypic variation, which is characterized by the number of distinct phenotypes they can randomly switch to. Each individual incurs a cost proportional to the number of potentially expressible phenotypes so as to retain phenotypic variation and expression. Our results show that phenotypic diversity coevolves with contingent cooperation under a wide range of conditions and that there exists an optimal level of phenotypic diversity best promoting contingent cooperation. It pays for contingent cooperators to elevate their potential of phenotypic variation, thereby increasing their opportunities of establishing cooperation via novel phenotypes, as these new phenotypes serve as secret tags that are difficult for defector to discover and chase after. We also find that evolved high levels of phenotypic diversity can occasionally collapse due to the invasion of defector mutants, suggesting that cooperation and phenotypic diversity can mutually reinforce each other. Thus, our results provide new insights into better understanding the coevolution of cooperation and phenotypic diversity.

Phenotypic diversity of Greek dill (Anethum graveolens L.) landraces

ABSTRACTDill has multiple culinary and medicinal purposes and the use of their landraces into a plant breeding program, requires the analysis of their phenotypic diversity. In this study, 33 Greek dill landraces collected from diverse areas were evaluated using traits based on UPOV descriptor list. Phenotypic diversity was assessed using Shannon-Weaver diversity index (H΄) and non-linear principal component analysis. Grouping of landraces was further performed through hierarchical cluster analysis. The H' index ranged from 0.32 (stem waxiness) to 0.98 (density of foliage) with a mean value of 0.68 indicating a high level of phenotypic diversity. High H' values were recorded for the foliage width, stem color and anthocyanin coloration. Multivariate analysis revealed three common genetic groups: 1) North mainland Greece, 2) Aegean islands and 3) Central mainland Greece. The landraces’ heterogeneity was attributed to various traits linked to specific geographic origin, such as early time of flowering and high stem waxiness allied with the landraces originated from the Aegean islands. Greek dill landraces revealed useful variation on yield component traits related to fresh herb weight and to seed production, such as high number of leaves/plant and large diameter of main umbel that can be promptly exploited in breeding programs.

Whole-genome sequencing of eight goat populations for the detection of selection signatures underlying production and adaptive traits

The goat (Capra hircus) is one of the first farm animals that have undergone domestication and extensive natural and artificial selection by adapting to various environments, which in turn has resulted in its high level of phenotypic diversity. Here, we generated medium-coverage (9–13×) sequences from eight domesticated goat breeds, representing morphologically or geographically specific populations, to identify genomic regions representing selection signatures. We discovered ~10 million single nucleotide polymorphisms (SNPs) for each breed. By combining two approaches, ZHp and di values, we identified 22 genomic regions that may have contributed to the phenotypes in coat color patterns, body size, cashmere traits, as well as high altitude adaptation in goat populations. Candidate genes underlying strong selection signatures including coloration (ASIP, KITLG, HTT, GNA11, and OSTM1), body size (TBX15, DGCR8, CDC25A, and RDH16), cashmere traits (LHX2, FGF9, and WNT2), and hypoxia adaptation (CDK2, SOCS2, NOXA1, and ENPEP) were identified. We also identified candidate functional SNPs within selected genes that may be important for each trait. Our results demonstrated the potential of using sequence data in identifying genomic regions that are responsible for agriculturally significant phenotypes in goats, which in turn can be used in the selection of goat breeds for environmental adaptation and domestication.

Estimating population structure and genetic diversity of five Moroccan sheep breeds by microsatellite markers

Investigating the genetic variability and structure of Moroccan sheep breeds will reveal crucial information for the conservation and management of this population. This study used 22 microsatellite markers to assess the genetic diversity among and within five Moroccan sheep breeds: Sardi (N=35), Boujaad (N=31), Timadhite (N=35), Beni Guil (N=35), and D⿿man_Morroco (N=35). In the whole sample, a total of 299 alleles were detected. The five breeds showed a relatively high level of gene diversity ranging between 0.725 (D⿿man_Morocco) and 0.764 (Timahdite). The Analysis of Molecular Variance (AMOVA) indicated that variability among populations contributed only 3.64% of the observed genetic diversity. Wilcoxon tests of excess heterozygosity under the two-phase model (TPM) did not provide strong evidence for recent bottlenecks in the five studied breeds. Unrooted neighbour joining (NJ) tree for the modified Cavalli-Sforza chord distance (DA), pairwise multilocus estimates of an effective number of migrants (Nm) and the Bayesian clustering method cohesively revealed poor structure of genetic variation among breeds. Our results also show that in spite of the high level of phenotypic diversity in the Moroccan sheep breeds, the past breeding strategies could lead to genetic admixture occurring as a result of relatively high gene-flow among the breeds.

Morphological characterization of Korean and Turkish watermelon germplasm

A total of 67 watermelon accessions which include 37 accessions from Korean and 27 accessions from Turkish germplasm and 3 accessions of other related species from USA were investigated for morphological characteristics. The UPOV descriptor list for 56 characters (6 seedlings, 4 plants, 11 leaves, 5 flowers, 23 fruits and 7 seeds) was used in characterization. In addition, eight quantitative characters, hypocotyl length, cotyledon width, cotyledon length, fruit weight, fruit length, fruit width, thickness of outer layer of pericarp and soluble solid content were also measured. The 56 qualitatively scored characters were analyzed by principle coordinate analysis (PCoA) while the eight quantitative ones were subjected to principle component analysis (PCA). Morphological characterization result demonstrated that the accessions displayed high morphological diversity(how much percent?). A high level of phenotypic diversity was observed from the results of morphological characterization. However, plant growth habit and leaf blade flecking showed constant characters for all of the accessions. The Korean and Turkish watermelon genotypes are diverse groups and can be separated by both multivariate analysis of morphological characters although the grouping was more apparent in PCoS results.

Phenotypic evaluation and characterization of a collection of Malus species

A collection of 337 Malus accessions representing 46 species of the Fruit Genebank in Dresden-Pillnitz, Germany, were evaluated for 64 morphological and phenological traits to proof the classification of the accession and to analyze genetic relationships. Morphological characteristics were determined for the whole tree, shoots, leaves, flowers and fruits. Data were subjected to principal component analysis (PCA), and a dendrogram was constructed to demonstrate morphological relationship. According to PCA the most important variables integrated in the first principal component were mainly fruit descriptors and three traits characterizing pubescence (1 year old shoot, leaf blade, and pedicel). Cluster analysis clearly separated the accessions in Malus series. The results showed the polyphyletic origin of the section Sorbomalus. The North American apple species, M. fusca, was closely related to the species contributing to the East Asian center of the genus origin. The relict species of the European continent (M. trilobata) was grouped in near distance to the North American species belonging to section Chloromeles. The species of Sieversinae and Baccatae dominated in one main cluster indicating their close relatedness. Most of M. ×domestica accessions were grouped with M. sieversii and M. orientalis; this supports the Sievers apple as an ancestor of domesticated apple. The morphological evaluations in this study indicated a high level of phenotypic diversity in the genebank collection. These phenotypical data will increase the feasibility of prioritizing accessions based on the uniqueness of desirable morphological traits.

Evolution of clonal populations approaching a fitness peak

Populations facing novel environments are expected to evolve through the accumulation of adaptive substitutions. The dynamics of adaptation depend on the fitness landscape and possibly on the genetic background on which new mutations arise. Here, we model the dynamics of adaptive evolution at the phenotypic and genotypic levels, focusing on a Fisherian landscape characterized by a single peak. We find that Fisher's geometrical model of adaptation, extended to allow for small random environmental variations, is able to explain several features made recently in experimentally evolved populations. Consistent with data on populations evolving under controlled conditions, the model predicts that mean population fitness increases rapidly when populations face novel environments and then achieves a dynamic plateau, the rate of molecular evolution is remarkably constant over long periods of evolution, mutators are expected to invade and patterns of epistasis vary along the adaptive walk. Negative epistasis is expected in the initial steps of adaptation but not at later steps, a prediction that remains to be tested. Furthermore, populations are expected to exhibit high levels of phenotypic diversity at all times during their evolution. This implies that populations are possibly able to adapt rapidly to novel abiotic environments.