Analyses Of Character Evolution Research Articles

Challenge accepted: Evolutionary lineages versus taxonomic classification of North American shrub willows (Salix).

The huge diversity of Salix subgenus Chamaetia/Vetrix clade in North America and the lack of phylogenetic resolution within this clade has presented a difficult but fascinating challenge for taxonomists to resolve. Here we tested the existing taxonomic classification with molecular tools. In this study, 132 samples representing 46 species from 22 described sections of shrub willows from the United States and Canada were analyzed and combined with 67 samples from Eurasia. The ploidy levels of the samples were determined using flow cytometry and nQuire. Sequences were produced using a RAD sequencing approach and subsequently analyzed with ipyrad, then used for phylogenetic reconstructions (RAxML, SplitsTree), dating analyses (BEAST, SNAPPER), and character evolution analyses of 14 selected morphological traits (Mesquite). The RAD sequencing approach allowed the production of a well-resolved phylogeny of shrub willows. The resulting tree showed an exclusively North American (NA) clade in sister position to a Eurasian clade, which included some North American endemics. The NA clade began to diversify in the Miocene. Polyploid species appeared in each observed clade. Character evolution analyses revealed that adaptive traits such as habit and adaxial nectaries evolved multiple times independently. The diversity in shrub willows was shaped by an evolutionary radiation in North America. Most species were monophyletic, but the existing sectional classification could not be supported by molecular data. Nevertheless, monophyletic lineages share several morphological characters, which might be useful in the revision of the taxonomic classification of shrub willows.

Comparative morphology of oral glands in snakes of the family Homalopsidae reveals substantial variation and additional independent origins of salt glands within Serpentes.

Using diffusible iodine-based contrast-enhanced computed tomography (diceCT), we examined the morphology of the oral glands of 12 species of the family Homalopsidae. Snakes of this family exhibit substantial interspecific morphological variation in their oral glands. Particular variables are the venom glands, ranging from large (e.g., Subsessor bocourti) to small (e.g., Erpeton tentaculatum). The supra- and infralabial glands are more uniform in morphology, being the second most developed in almost all the sampled species. Premaxillary glands distinct from the supralabial glands were observed in five species (Myron richardsonii, Bitia hydroides, Cantoria violacea, Fordonia leucobalia, and Gerarda prevostiana), in addition to Cerberus rynchops, the only species in which this condition was previously documented associated with the excretion of salt. In the three species of the saltwater group of homalopsids (C. violacea, F. leucobalia, and G. prevostiana), the premaxillary glands also extend posteriorly, occupying a large area above the supralabial gland, a condition not observed in any other species of snake studied thus far. Character evolution analyses indicate that premaxillary glands differentiated from the supralabial gland and evolved independently three or four times in the family, always in lineages that invaded marine habitats. Our results suggest that the differentiated premaxillary glands are likely salt glands, as is the case in C. rynchops. If corroborated, this increases to six or seven the number of independent evolutionary origins of salt glands in snakes that have undergone an evolutionary transition to marine life.

Plastomic data shed new light on the phylogeny, biogeography, and character evolution of the family Crassulaceae

AbstractCrassulaceae is a mid‐sized family of angiosperms, most species of which are herbaceous succulents, usually with 5‐merous flowers and one or two whorls of stamens. Although previous phylogenetic studies revealed seven major “clades” in Crassulaceae and greatly improved our understanding of the evolutionary history of the family, relationships among major clades are still contentious. In addition, the biogeographic origin and evolution of important morphological characters delimiting infrafamilial taxa have not been subject to formal biogeographic and character evolution analyses based on a well‐supported phylogeny backbone. In this study, we used plastomic data of 52 species, representing all major clades revealed in previous studies to reconstruct a robust phylogeny of Crassulaceae, based on which we unraveled the spatiotemporal framework of diversification of the family. We found that the family may originate in southern Africa and then dispersed to the Mediterranean, from there to eastern Asia, Macaronesia, and North America. The crown age of Crassulaceae was dated at ca. 63.93 million years ago, shortly after the Cretaceous–Paleogene (K‐Pg) boundary. We also traced the evolution of six important morphological characters previously used to delimit infrafamilial taxa and demonstrated widespread parallel and convergent evolution of both vegetative (life form and phyllotaxis) and floral characters (number of stamen whorls, petals free or fused, and flower merism). Our results provide a robust backbone phylogeny as a foundation for further investigations, and also some important new insights into biogeography and evolution of the family Crassulaceae.

Phylogeny of Alpinia coriandriodora D. Fang and Implications for Character Evolution and Conservation.

Alpinia, the largest genus of Zingiberaceae, includes ca. 250 species. The A. coriandriodora D. Fang was recognized for Vietnamese flora. However, the systematic position of this species within Alpinia genus was unclear. The study aimed to understand the phylogenetic placement of A. coriandriodora based on the molecular data and interpret evolution of the key morphological characters. The phylogenetic analysis were conducted by using the combined dataset of two DNA regions by both Maximum Likelihood (ML) and Bayesian Inference (BI) methods. Seven morphological characters were selected for morphological character evolution and the analysis was performed in Mesquite. Alpinia coriandriodora was supported closely related to southern Chinese species of Alpinia. Morphological character optimizations suggest that the presence/absence of tomentum in leaf, inflorescence rachis and ovary is an important character for the taxonomy of Alpinia. The character evolution analyses indicated that panicle is ancestral character in Alpinia. The A. coriandriodora shares different evolutionary histories based on our character re-construction to most members of Southeast Asian Alpinia. The presence of filament is supposed to be an adaptation to the pollination by insects for species of Alpinia. The present study revealed the molecular phylogenetic relationship of A. coriandriodora within Alpinia. The presence of filament could be an adaptation to the pollination by insects for species of Alpinia. Some reasonable conservation strategies are proposed to protect the species including maintenance of the plant's natural habitats, seeds or seedlings collection for germplasm storage and artificial breeding using biotechnology.

The use of plant ontologies in comparative and evolutionary studies should be flexible

The use of plant ontologies in comparative and evolutionary studies should be flexible

A new balaenopterid species from the Southern North Sea Basin informs about phylogeny and taxonomy of Burtinopsis and Protororqualus (Cetacea, Mysticeti, Balaenopteridae)

Background An extensive radiation can be inferred among balaenopterid mysticetes in the last 10 million years based on a rich fossil record. Many extinct genera and species have been established in the past by the study of fossil rorquals from northern and southern hemispheres. In many cases, the new fossils are used to create new genera. However, in very recent times, new species of known genera have been described that help our understanding of the speciation processes and the biogeography of these whales. Here, a new species of balaenopterid whales is described in order to better understand the past diversity of Balaenopteridae and to analyze its paleobiogeographical implications. As the new species closely resembles a taxon established in the 19th century (i.e., Burtinopsis), a detailed analysis of this taxon was necessary to support the new taxonomic statements of this article. Methods A new partial skeleton including skull and earbones is described and compared to an extended sample of living and fossil mysticete species. A phylogenetic analysis including 355 character states scored in 88 taxa was performed to understand its relationships within the genus Protororqualus, to allow paleobiogeographic inferences and to better understand the relationships of Protororqualus within Balaenopteridae. Maximum parsimony analyses of character evolution were performed to understand morphological transformations within Balaenopteridae. The revision of Burtinopsis was carried out based on detailed descriptions and comparisons of the type materials that were figured and measured. Results Protororqualus wilfriedneesi sp. nov. was established based on a comparative analysis of the skull and earbone morphology. The specimen is dated back to the Zanclean (Lower Pliocene, between c. 5.3 and 3.6 Ma). A taphonomical study of the holotype skeleton revealed evidence of interactions with sharks and fishes before the definitive burial of the carcass. Based on the phylogenetic analysis, the monophyly of the genus Protororqualus was confirmed. Protororqualus wilfriedneesi sp. nov. was more derived than Protororqualus cuvieri suggesting that it resulted from an invasion of the North Sea Basin (and the North Atlantic ocean) from the Mediterranean basin. Several specimens from western and eastern sides of the Atlantic Ocean are described that suggest that Protororqualus wilfriedneesi had a trans-Atlantic distribution in the Pliocene.

Sequence Capture Phylogenomics of True Spiders Reveals Convergent Evolution of Respiratory Systems.

The common ancestor of spiders likely used silk to line burrows or make simple webs, with specialized spinning organs and aerial webs originating with the evolution of the megadiverse "true spiders" (Araneomorphae). The base of the araneomorph tree also concentrates the greatest number of changes in respiratory structures, a character system whose evolution is still poorly understood, and that might be related to the evolution of silk glands. Emphasizing a dense sampling of multiple araneomorph lineages where tracheal systems likely originated, we gathered genomic-scale data and reconstructed a phylogeny of true spiders. This robust phylogenomic framework was used to conduct maximum likelihood and Bayesian character evolution analyses for respiratory systems, silk glands, and aerial webs, based on a combination of original and published data. Our results indicate that in true spiders, posterior book lungs were transformed into morphologically similar tracheal systems six times independently, after the evolution of novel silk gland systems and the origin of aerial webs. From these comparative data, we put forth a novel hypothesis that early-diverging web-building spiders were faced with new energetic demands for spinning, which prompted the evolution of similar tracheal systems via convergence; we also propose tests of predictions derived from this hypothesis.[Book lungs; discrete character evolution; respiratory systems; silk; spider web evolution; ultraconserved elements.].

Mass estimation of extinct taxa and phylogenetic hypotheses both influence analyses of character evolution in a large clade of birds (Telluraves).

Incorporating extinct taxa in phylogenetic comparative methods is rapidly becoming invaluable in studies of character evolution. An increasing number of studies have evaluated the effects of extinct taxa, and different numbers of extinct taxa, on model selection and parameter estimation. Body mass is a well-studied phenotype, but individual mass estimates may vary dramatically depending on the particular measurement used. Here, we perform an analysis of body mass evolution in a large clade of principally arboreal birds, incorporating 76 extinct species. We evaluate how different methods for estimating body mass of extinct taxa, and different phylogenetic hypotheses, affect our understanding of the rate and pattern of body mass evolution. Our results show that model selection can vary dramatically depending on the phenotypic and phylogenetic hypothesis used in the reconstruction. Even small changes in phenotype estimates can lead to different model selection and, as a result, affect the inferred evolutionary history. The best-fit models support an increase in the rate of evolution following the K-Pg boundary, with variation accumulating linearly through the Cenozoic. These results provide additional insight into the application of comparative models of evolution, as well as the evolutionary history of one of the most spectacular vertebrate radiations.

Ontogeny and phylogeny of the mammalian chondrocranium: the cupula nasi anterior and associated structures of the anterior head region

BackgroundThe study of chondrocrania has a long tradition with a focus on single specimens and stages. It revealed great interspecific diversity and a notion of intraspecific variation. As an embryonic structure, the chondrocranium is subject to major changes in ontogeny with resorption and ossification of different cartilaginous structures. The cupula nasi anterior is the anteriormost portion of the cartilaginous nasal capsule and is expected to mirror much of the animal's life history and lifestyle. Its diversity in mammals is reflected in the external nasal anatomy of newborns. Marsupials and placentals show marked differences, likely related to breathing and suckling behavior.ResultsWe examined histological sections of five marsupial and three placentals species and traced the development of the cupula nasi anterior and the anterior nasal capsule. We found ontogenetic variation for nearly 50% of the 43 characters defined herein. By comparing to the literature and considering ontogenetic variation, we performed an analysis of character evolution in 70 mammalian species and reconstructed the nasal anatomy of the therian ancestor.ConclusionsAt birth, marsupials have a complete but simple cupula nasi anterior, whereas placentals display a more diverse morphology due to reductions and variations of chondrocranial elements. The more compact nasal capsule in marsupials is related to a long and strong fixation to the mother’s teat after birth. Within marsupials and placentals, several derived characters distinguish major taxa, probably related to developmental and functional constraints. The reconstructed ancestral anatomy of the cupula nasi anterior supports the hypothesis that the therian ancestor was placental-like and that the marsupial lifestyle is more derived.

Phylogeny of Spiraea (Rosaceae) based on plastid and nuclear molecular data: Implications for morphological character evolution and systematics

Spiraea (Rosaceae) is a plant genus of great horticultural value, comprising 50–80 species distributed throughout the northern hemisphere, seemingly with particular affinity to eastern Asia. Phylogenetic relationships within the genus have not been well studied and patterns of evolution of morphological characters remain unclear. Here, we present the first comprehensive phylogenetic analysis of the genus based on one nuclear and two plastid markers. Phylogenetic analysis was done using maximum parsimony, maximum likelihood, and Bayesian inference on the plastid DNA sequences (2446 bp), composed of the contiguous trnL-F region and matK, the nuclear internal transcribed spacer (727 bp), and the concatenated datasets (3173 bp). Separate analyses of the plastid, nuclear and concatenated datasets yielded five well-supported major clades within Spiraea that also received high support from morphological characters. Our results suggest that reliance on a few morphological characters in past classifications failed to recover monophyletic infrageneric taxa. All previous sections are recognized as paraphyletic or polyphyletic except section Spiraea which is nested within section Calospira. Character evolution analyses indicate that the trait, inflorescence type, was over-emphasized in earlier taxonomic treatments, which artificially divided the genus into three groups. Our analyses indicate that characters such as leaf blade margin, development of reproductive shoot, and flower color are valuable for infrageneric classification, while others, such as number of bud scale, branchlet shape, and leaf blade shape are of limited value.

Dissecting the basis of novel trait evolution in a radiation with widespread phylogenetic discordance.

Phylogenetic analyses of trait evolution can provide insight into the evolutionary processes that initiate and drive phenotypic diversification. However, recent phylogenomic studies have revealed extensive gene tree-species tree discordance, which can lead to incorrect inferences of trait evolution if only a single species tree is used for analysis. This phenomenon-dubbed "hemiplasy"-is particularly important to consider during analyses of character evolution in rapidly radiating groups, where discordance is widespread. Here, we generate whole-transcriptome data for a phylogenetic analysis of 14 species in the plant genus Jaltomata (the sister clade to Solanum), which has experienced rapid, recent trait evolution, including in fruit and nectar colour, and flower size and shape. Consistent with other radiations, we find evidence for rampant gene tree discordance due to incomplete lineage sorting (ILS) and to introgression events among the well-supported subclades. As both ILS and introgression increase the probability of hemiplasy, we perform several analyses that take discordance into account while identifying genes that might contribute to phenotypic evolution. Despite discordance, the history of fruit colour evolution in Jaltomata can be inferred with high confidence, and we find evidence of de novo adaptive evolution at individual genes associated with fruit colour variation. In contrast, hemiplasy appears to strongly affect inferences about floral character transitions in Jaltomata, and we identify candidate loci that could arise either from multiple lineage-specific substitutions or standing ancestral polymorphisms. Our analysis provides a generalizable example of how to manage discordance when identifying loci associated with trait evolution in a radiating lineage.

Comprehensive evolutionary analysis of the Anthroherpon radiation (Coleoptera, Leiodidae, Leptodirini).

The genus Anthroherpon Reitter, 1889 exhibits the most pronounced troglomorphic characters among Coleoptera, and represents one of the most spectacular radiations of subterranean beetles. However, radiation, diversification, and biogeography of this genus have never been studied in a phylogenetic context. This study provides a comprehensive evolutionary analysis of the Anthroherpon radiation, using a dated molecular phylogeny as a framework for understanding Anthroherpon diversification, reconstructing the ancestral range, and exploring troglomorphic diversity. Based on 16 species and 22 subspecies, i.e. the majority of Anthroherpon diversity, we reconstructed the phylogeny using Bayesian analysis of six loci, both mitochondrial and nuclear, comprising a total of 4143 nucleotides. In parallel, a morphometric analysis was carried out with 79 landmarks on the body that were subjected to geometric morphometrics. We optimized morphometric features to phylogeny, in order to recognize the way troglomorphy was expressed in different clades of the tree, and did character evolution analyses. Finally, we reconstructed the ancestral range of the genus using BioGeoBEARS. Besides further elucidating the suprageneric classification of the East-Mediterranean Leptodirini, our main findings also show that Anthroherpon dates back to the Early Miocene (ca. 22 MYA) and that the genus diversified entirely underground. Biogeographic reconstruction of the ancestral range shows the origin of the genus in the area comprising three high mountains in western Montenegro, which is in the accordance with the available data on the paleogeography of the Balkan Peninsula. Character evolution analysis indicates that troglomorphic morphometric traits in Anthroherpon mostly evolve neutrally but may diverge adaptively under syntopic competition.

A phylogenetic analysis of the Primnoidae (Anthozoa: Octocorallia: Calcaxonia) with analyses of character evolution and a key to the genera and subgenera

BackgroundPrevious phylogenetic analyses of primnoid octocorals utilizing morphological or molecular data have each recovered evolutionary relationships among genera that are largely incongruent with each other, with some exceptions. In an effort to reconcile molecular-based phylogenies with morphological characters, phylogenetic reconstructions were performed with 33 of 43 primnoid genera using four loci (mtMutS, COI, 28S and 18S), and ancestral state reconstructions were performed using 9 taxonomically relevant characters. In addition, an updated illustrated key to the current 48 genus-level (43 genera, 5 subgenera) primnoids is presented.ResultsAncestral state reconstruction recovered the ancestral colony shape of primnoids as dichotomous planar. Convergence was detected among all 9 characters, and reversals to the character state of the common ancestor occurred in 4 characters. However, some characters were found to be informative. For example, the weak ascus scale of Metafannyella is not likely homologous to the ascus scales of Onogorgia and Fannyella, and the monophyly of two subgenera within Thouarella, which contain polyps in either whorls or an isolated arrangement, was supported. Phylogenetic analyses were generally consistent with previous studies, and resulted in the synonymy of one genus and a subgenus, the elevation of two subgenera, and the transfer of two species back to an original genus. For example, body wall ornamentation of Fanellia was re-evaluated, indicating a synonymy with Callogorgia; the utility of polyp arrangement for the subgenus Plumarella (Dicholaphis) was not supported, and is synonymized with the nominate subgenus Plumarella (Plumarella); the subgenera Plumarella (Faxiella) and Plumarella (Verticillata) are raised to generic status; and the two Plumarella species (P. diadema and P. undulata) are transferred back to Thouarella based on the homology of their marginal scales.ConclusionsAltogether, and similar to other octocorallian groups, these results indicate that many of the morphological characters examined among primnoids, particularly colony morphology, are labile and exhibit complex evolutionary histories. However, some morphological characters such as coordination of polyps, presence of the ascus body wall scale, number of rows of body wall scales, and number of marginal scales help identify many clades, and are suitable for robust systematic assessments among primnoids.

Testing hypotheses on suprageneric relationships and morphological evolution in the Leucobryaceae (Bryophyta)

We studied suprageneric relationships and patterns of morphological character evolution within the moss family Leucobryaceae, based on phylogenetic analyses of markers from all three genomes and representatives from 11 out of 14 genera. Three main lineages are strongly supported within the Leucobryaceae, which display different morphologies of the leaf costa, two dicranoid clades (Campylopus clade and Dicranodontium clade) and a leucobryoid clade. Character evolution analyses resolved the leucobryoid morphology as a synapomorphy for the leucobryoid clade and provided data to evaluate generic circumscriptions within the family. Patterns of molecular variation, species richness, geographical distribution, ecological amplitude and variation in costa structure seem to covary: The two lineages with the most modified morphologies (deviating from the basic dicranoid type; Campylopus and leucobryoid clades) are also the most molecularly variable, species diverse, and occupy the broadest distributions and widest variety of habitats. Most sampled genera have clear morpho-molecular circumscriptions, except Campylopodiella, Dicranodontium and Leucobryum. For the latter, two alternative topologies were resolved (Leucobryum monophyletic or the Asian genera Cladopodanthus and Schistomitrium nested within Leucobryum).

Phylogeny of Riama (Squamata: Gymnophthalmidae), impact of phenotypic evidence on molecular datasets, and the origin of the Sierra Nevada de Santa Marta endemic fauna.

Riama is the most speciose genus of the Neotropical lizard family Gymnophthalmidae. Its more than 30 montane species occur throughout the northern Andes, the Cordillera de la Costa (CC) in Venezuela, and Trinidad. We present the most comprehensive phylogenetic analysis of Riama to date based on a total evidence (TE) approach and direct optimization of molecular and morphological evidence. Analyses use DNA sequences from four loci and 35 phenotypic characters. The dataset consists of 55 ingroup terminals representing 25 of the 30 currently recognized species of Riama plus five undescribed taxa, including an endemic species from the Sierra Nevada de Santa Marta (SNSM) in Colombia, and 66 outgroup terminals of 47 species. Analysis results in a well-supported hypothesis in which Riama is polyphyletic, with its species falling into three clades. The Tepuian Anadia mcdiarmidi nests within one clade of Riama, and the recently resurrected Pantodactylus nests within Cercosaura. Accordingly, we propose a monophyletic taxonomy that reflects historical relationships. Analysis of character evolution indicates that the presence/absence of prefrontals-a cornerstone of the early genus-level taxonomy of cercosaurines-is optimally explained as having been plesiomorphically present in the most recent common ancestor of Cercosaurinae and lost in that of the immediately less inclusive clade. Multiple independent reversals to present and subsequent returns to absent occur within this clade. To evaluate the impact of phenotypic evidence on our results, we compare our TE results with results obtained from analyses using only molecular data. Although phenotypic evidence comprises only 1.2% of the TE matrix, its inclusion alters both the topology and support values of the clades that do not differ. Finally, current phylogenetic evidence reveals a SNSM-CC-Trinidad-tepuis biogeographical link. We hypothesize that an ancient connection facilitated the exchange of species between the SNSM and the CC.

Irrational exuberance for resolved species trees.

Phylogenomics has largely succeeded in its aim of accurately inferring species trees, even when there are high levels of discordance among individual gene trees. These resolved species trees can be used to ask many questions about trait evolution, including the direction of change and number of times traits have evolved. However, the mapping of traits onto trees generally uses only a single representation of the species tree, ignoring variation in the gene trees used to construct it. Recognizing that genes underlie traits, these results imply that many traits follow topologies that are discordant with the species topology. As a consequence, standard methods for character mapping will incorrectly infer the number of times a trait has evolved. This phenomenon, dubbed "hemiplasy," poses many problems in analyses of character evolution. Here we outline these problems, explaining where and when they are likely to occur. We offer several ways in which the possible presence of hemiplasy can be diagnosed, and discuss multiple approaches to dealing with the problems presented by underlying gene tree discordance when carrying out character mapping. Finally, we discuss the implications of hemiplasy for general phylogenetic inference, including the possible drawbacks of the widespread push for "resolved" species trees.

The origin and divergence of Gobioninae fishes (Teleostei: Cyprinidae) based on complete mitochondrial genome sequences

The gudgeons (subfamily Gobioninae) are a group of cyprinid fishes primarily distributed in East Asia. However, studies on their origins and divergence are scarce. Here the whole mitochondrial genome sequences of 27 gudgeon species (including one newly determined), 22 other cyprinid species, and two non-cyprinids as outgroups are applied to infer the evolution of the gudgeons. Based on Bayesian and maximum likelihood phylogenetic analyses, the gudgeons were determined to be a monophyletic group which can be further subdivided into four monophyletic clades with strong supports. The divergence times of the gudgeons were estimated using a relaxed molecular clock method; the results indicate that these fishes originated in the early Paleocene (approx. 63.5 Mya) and that the basal Hemibarbus group diverged from the other gudgeon fishes (approx. 58.3 Mya). As an independent group the Coreius began to diverge from the remaining two groups (approx. 54.6 Mya); the most derived two groups diverged from each other (approx. 53.6 Mya). The divergences of the four gudgeon groups were within a relatively short time frame (approx. 58–53 Mya). Based on the reconstruction of evolutionary trends of gudgeon habitat, evidence is provided that supports the origin and differentiation of this fauna as being associated with some special paleo-environmental events occurring from the early Paleocene to the Pliocene. The study represents comprehensive molecular dating and character evolution analyses of the gudgeons, and providing a valuable framework for future research in the evolution of the Gobioninae fishes.

Development and evolution of the female gametophyte and fertilization process in Welwitschia mirabilis (Welwitschiaceae).

The female gametophyte of Welwitschia has long been viewed as highly divergent from other members of the Gnetales and, indeed, all other seed plants. However, the formation of female gametes and the process of fertilization have never been observed. Standard histological techniques were applied to study gametophyte development and the fertilization process in Welwitschia. In Welwitschia, fertilization events occur when pollen tubes with binucleate sperm cells grow down through the nucellus and encounter prothallial tubes, free nuclear tubular extensions of the micropylar end of the female gametophyte that grow up through the nucellus. Entry of a binucleate sperm cell into a vacuolate prothallial tube appears to stimulate the rapid coagulation of cytoplasm around a single female nucleus, which differentiates into an egg cell. One sperm nucleus enters the female gamete, while the second sperm nucleus remains outside and ultimately degenerates. Only a single fertilization event occurs per mating pair of pollen tube and prothallial tube. Welwitschia lacks the gnetalean pattern of regular double fertilization, as found in Ephedra and Gnetum, involving sperm from a single pollen tube to yield two zygotes. Moreover, an analysis of character evolution indicates that the female gametophyte of Welwitschia is highly apomorphic both among seed plants, and specifically within Gnetales, but also shares several key synapomorphies with its sister taxon Gnetum. Finally, the biological role of prothallial tubes in Welwitschia is examined from the perspectives of gamete competition and kin conflict.

Towards a new classification of Salvia s.l.: (re)establishing the genus Pleudia Raf.

Salvia L. In its traditional circumscription is the largest genus within the mint family. To date, the magnitude of the task has rendered it difficult to provide a genus-wide revision based on morphological data. Current molecular investigations based on a dense taxon sampling representing the whole phenotypic diversity and distribution range of Salvia confirmed that the genus is polyphyletic. Salvia species fall in 4 distinct clades, although all of them, except Clade IV, also include non-Salvia genera. A taxonomic revision is thus urgently needed with two different approaches that have to be considered: (1) to include the 5 morphologically distinct non-Salvia genera in Salvia or (2) to split Salvia s.l. Into Salvia s.s. And several additional genera. Since Salvia is already highly heterogeneous in species distribution, morphology, and chromosome number, we prefer to split the genus into molecularly well-supported clades. This new concept may facilitate monographic studies and more focused analyses of character evolution within or between the clades. Species representing Salvia sect. Eremosphace Bunge (subclade III-A) were chosen exemplarily to provide arguments for elevating this particular group to the level of genus (Pleudia Raf.).

Evolution of cyme architecture in Celastraceae

Celastraceae are characterized by a cymose pattern of inflorescence ramification. Under this basic pattern, many inflorescence forms have been described within the family, e.g., dichasium, monochasium, pleiochasium, botryoid, thyrsoid, fascicle. Thus, the question has arisen—how have these varieties evolved or transformed from one to another? Through morphogenetic observations using paraffin sections, scanning electron microscopy (SEM), and stereomicroscopy, we studied the architecture and developmental processes of the inflorescences of five species of Celastrus and Euonymus. We found in C. orbiculatus that the reduction of subtending leaves of the axillary dichasia on a developing flowering shoot made it become a terminal thyrsoid. A dichasium in the leaf axil as commonly seen in Euonymus is the most frequent type of inflorescence in Celastraceae. An analysis of character evolution suggested that a dichasium is the ancestral state for Celastraceae. Therefore, within Celeastaceae, an axillary dichasium may be the basic type or unit of inflorescences. Transitions from dichasium to thrysoid and other types of cymes, and even to solitary flowers might have occurred repeatedly in the family, probably a phenomenon of evolutionary convergence due to changing environmental conditions. The present study provided helpful information for understanding the evolution of the cymose type of inflorescence in flowering plants.