Structural and systematic study of an unusual tracheid type in cacti

Wide-band tracheids are a specialized tracheid type in which an annular or helical secondary wall projects deeply into the cell lumen. They are short, wide and spindle-shaped, and their bandlike secondary walls cover little of the primary wall, leaving most of it available for water diffusion. Wide-band tracheids appear to store and conduct water while preventing the spread of embolisms. They may be the most abundant tracheary element in the xylem, but they are always accompanied by at least a few vessels. Typically, fibers are absent wherever wide-band tracheids are present. Wide-band tracheids occur in the primary and secondary xylem of succulent stems, leaves and roots in genera of all three subfamilies of Cactaceae but were not found in the relictual genusPereskia, which lacks succulent tissues. In the large subfamily Cactoideae, wide-band tracheids occur only in derived members, and wide-band tracheids of North American Cactoideae are narrower and are aligned in a more orderly radial pattern than those of South American Cactoideae. Wide-band tracheids probably arose at least three times in Cactaceae.     

Wide-band tracheids in genera of Portulacaceae: novel, non-xylary tracheids possibly evolved as an adaptation to water stress

Wide-band tracheids (WBTs) are novel tracheids with wide, lignified secondary walls that intrude deeply into the cell lumen when viewed in transverse sections. These tracheids are found in a few genera in related families in the order Caryophyllales: Aizoaceae, Cactaceae, and Portulacaceae. WBTs in these three families vary in (1) systematic occurrence (found in more highly derived genera in each family), (2) location in plant organs, and (3) structure and dimensions. In addition, an analysis was conducted of WBT cell walls to test the hypothesis that WBTs evolved as an adaptation to water stress (i.e., the wide secondary walls should prevent collapse of the primary wall during water stress). The cell wall data show that primary cell walls in WBTs cannot inwardly collapse to occlusion, thus providing support for the water stress hypothesis of WBT evolution. With consideration of their systematic occurrence, the molecular phylogenetic data, and data here showing support for a water stress adaptive origin, it is logical to assume that WBTs evolved in genera that were adapting to environments undergoing a rapid trend toward aridification.     

A phylogenetic hypothesis for the Aizoaceae (Caryophyllales) based on four plastid DNA regions

The Aizoaceae is the largest family of leaf succulent plants, and most of its species are endemic to southern Africa. To evaluate subfamilial, generic, and tribal relationships, we produced two plastid DNA data sets for 91 species of Aizoaceae and four outgroups: rps16 intron and the trnL-F gene region (both the trnL intron and the trnL-F intergenic spacer). In addition, we generated two further plastid data sets for 56 taxa restricted to members of the Ruschioideae using the atpB-rbcL and the psbA-trnH intergenic spacers. In the combined tree of the rps16 intron and trnL-F gene region, three of the currently recognized subfamilies (Sesuvioideae, Mesembryanthemoideae, and Ruschioideae) are each strongly supported monophyletic groups. The subfamily Tetragonioideae is polyphyletic, with Tribulocarpus as sister to the Sesuvioideae and Tetragonia embedded in the Aizooideae. Our study showed that the group consisting of the Sesuvioideae, Aizooideae, and Tetragonioideae does not form a monophyletic entity. Therefore, it cannot be recognized as a separate family in order to accommodate the frequently used concept of the Mesembryanthemaceae or "Mesembryanthema," in which the subfamilies Mesembryanthemoideae and Ruschioideae are included. We also found that several genera within the Mesembryanthemoideae (Mesembryanthemum, Phyllobolus) are not monophyletic. Within the Ruschioideae, our study retrieved four major clades. However, even in the combined analysis of all four plastid gene regions, relationships within the largest of these four clades remain unresolved. The few nucleotide substitutions that exist among taxa of this clade point to a rapid and recent diversification within the arid winter rainfall area of southern Africa. We propose a revised classification for the Aizoaceae.     

Correlates of hyperdiversity in southern African ice plants (Aizoaceae)

The exceptionally high plant diversity of the Greater Cape Floristic Region (GCFR) comprises a combination of ancient lineages and young radiations. A previous phylogenetic study of Aizoaceae subfamily Ruschioideae dated the radiation of this clade of > 1500 species in the GCFR to 3.8–8.7 Mya, establishing it as a flagship example of a diversification event triggered by the onset of a summer‐arid climate in the region. However, a more recent analysis found an older age for the Ruschioideae lineage (17 Mya), suggesting that the group may in fact have originated much before the aridification of the region 10–15 Mya. Here, we reassess the tempo of radiation of ice plants by using the most complete generic‐level phylogenetic tree for Aizoaceae to date, a revised calibration age and a new dating method. Our estimates of the age of the clade are even younger than initially thought (stem age 1.13–6.49 Mya), supporting the hypothesis that the radiation post‐dates the establishment of an arid environment in the GCFR and firmly placing the radiation among the fastest in angiosperms (diversification rate of 4.4 species per million years). We also statistically examine environmental and morphological correlates of richness in ice plants and find that diversity is strongly linked with precipitation, temperature, topographic complexity and the evolution of highly succulent leaves and wide‐band tracheids. © 2013 The Authors. Botanical Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 110–129.     

Genetic differentiation in the genus Lithops L. (Ruschioideae, Aizoaceae) reveals a high level of convergent evolution and reflects geographic distribution

Southern Africa is one of the hot spots for plant biodiversity, with ca. 80% of species endemic to this area. Rapid and recent radiations in Southern African plant genera were triggered by fine-scale differences in climate, topography and geology. The genus Lithops (Ruschioideae, Aizoaceae) contains 37 species and is widely distributed in Southern Africa. Species delimitation within the genus is challenging because the limited number of morphological characters in these reduced succulents varies intensely between populations, presumably as adaptations to local geological environments. We analysed phylogenetic relationships within Lithops using non-coding chloroplast DNA (trnS-trnG intergenic spacer), nuclear ribosomal internal transcribed spacer (nrITS) sequences and AFLP data. Genetic variability of the sequence data was very low, but AFLP data detected nine clades within Lithops that do not fit current morphology-based taxonomy. Two of these clades are separated by their distribution on the northern and eastern border of the distribution area, and four clades are found in the Gariep Centre in the estuary of the Orange River. Morphological similarities, especially colour of leaves, evolved repeatedly within the clades, thus we hypothesise that closely related species became adapted to different soil types in a mosaic-like geological environment. One-third of the species are found in the Gariep Centre, characterised by extremely diverse edaphic habitats.     

The Phylogeny of the Lophopidae and the Impact of Sexual Selection and Coevolutionary Sexual Conflict

A cladistic analysis of Lophopidae was performed, using 73 observed morphological characters and 41 taxa. This analysis involved 36 genera belonging to the Lophopidae family and 5 outgroups. For a better understanding of the selected characters some illustrations are provided. The most parsimonious cladograms obtained show that the Lophopidae cannot be considered as a monophyletic lineage unless two genera are withdrawn from this family: Hesticus Walker, 1862, and Silvanana Metcalf, 1947. The systematic position of these two genera remains uncertain. They cannot yet be included in another family of Fulgoromorpha. A cladistic analysis of each of the 19 remaining Fulgoromorphan families must be performed first. A new family could be created for these two genera, but not before we are sure that these two genera are in no way members of an existing family. The outgroup problem is discussed. The monophyletic lineage represented by the Lophopidae can be divided into four natural groups: Carriona⁺, Makota⁺, Sarebasa⁺, and Bisma⁺. When a cladistic analysis is completed using a data matrix without characters linked to females, the cladogram obtained presents a disrupted basal resolution. Female characters appear to bring a phylogenetic signal important basally in the evolution of the Lophopidae but also apically, directly between the relationships of some genera. A similar analysis, using a matrix without characters linked to males, provides a phylogeny disrupted between the groups that form the Lophopidae and in the basal resolution in these groups. The respective impacts of the genitalic characters are discussed in relation to sexual selection conflict.     

A test of Simpson's "rule of the survival of the relatively unspecialized" using fossil crinoids

Temporally long-ranging (=long-lived) taxa have been postulated to have unusual properties that aid their prolonged geologic survival. Past studies have examined dispersal capabilities, geographic ranges, and single-character morphological adaptations as factors that may contribute to geologic longevity. Here, I test whether long-lived fossil crinoid taxa are morphologically unusual using a whole suite of morphological characters. I define long-lived taxa in several explicit, comparative ways. I find that long-lived crinoid genera and families are often less distant from mean morphologies of their crinoid orders than their shorter-lived relatives; that is, they are relatively less specialized. I also compare the morphology of crinoid genera relative to basal members of their respective orders; mean morphological distances of long-lived genera from basal morphologies are seldom distinct from those of their shorter-lived relatives. I observe that long-lived crinoid genera are less distant from mean morphologies of their temporal cohorts compared with shorter-lived genera but not in a statistically significant manner. I conclude that long-lived crinoids are relatively unspecialized, in the sense that they are relatively closer to mean morphologies of their taxonomic groups.     

Phylogenetic implication of the chloroplast rpoC1 intron loss in the Aizoaceae (Caryophyllales)

A representative sample of 69 species from all recognized infrafamilial taxa of the family Aizoaceae (angiosperms, eudicotyledons, Caryophyllales) was surveyed for the presence/absence of the rpoC1 intron. PCR fragments of the samples fall into two size classes: a long fragment of approximately 1200 bp, and a short fragment of approximately 500 bp which was found in all samples from the tribes Drosanthemeae and Ruschieae of subfamily Ruschioideae. The length difference of about 700 bp corresponds to the length of the intron (738 bp in tobacco). Sequencing of the short fragment from Monilaria moniliformis revealed the precise excision of the intron as found in a previous study of the cactus family. It is concluded that the intron lacks in all samples from the clade including the tribes Drosanthemeae and Ruschieae of subfamily Ruschioideae, thus providing valuable PCR-based, sequence- and morphology-independent evidence for the monophyly of this lineage.     

Phylogenetic reassessment of the five forewing radial-veined tribes of Riodininae (Lepidoptera: Riodinidae)

The relationships among the genera and tribal groupings of Riodininae with five forewing radial veins, and between these and tribes with four forewing radial veins, were examined using a phylogenetic analysis. Using the type species from all sixteen genera in the tribal groupings Eurybiini, Mesosemiini and incertae sedis (a presumed paraphyletic group of loosely related genera), and representatives from the four forewing radial‐veined riodinine tribes, thirty‐five new and traditional characters were coded from adult ecology, wing venation and pattern, the adult head and body, male and female genitalia, and early stage ecology and morphology. The majority of characters are illustrated. Phylogenetic analysis of these data produced five equally most parsimonious cladograms using equal weights and after successive weighting. The strict consensus of these confirms the monophyly of Eurybiini and Mesosemiini as currently conceived, but also indicates several higher‐level relationships not previously hypothesized. Mesosemiini is here more broadly defined to also include the entire incertae sedis section, and the tribe is divided into Mesosemiina, for the previously delimited Mesosemiini plus Eunogyra and Teratophthalma, and Napaeina, subtr.n. for the incertae sedis section minus these two genera. The following hypothesis of relationships is tentatively proposed for the basal clades of Riodininae: Mesosemiini + (Eurybiini + remainder of Riodininae). These new hypotheses, and the characters supporting them, are discussed and compared with those previously proposed.     

Mycorrhizal status of some plants of the Araucaria forest and the Atlantic rainforest in Santa Catarina, Brazil

 In Brazil, the Araucaria forest and the Atlantic rainforest are two threatened ecosystems, with 10% or less of their original areas presently existing. To assess the mycorrhizal status in these forests, roots of 29 native species, belonging to 19 families, were collected throughout the year from different regions of Santa Catarina, Brazil. Roots were washed, and then cut in a cryo-microtome to seek ectomycorrhizal colonization. Other roots were stained before being examined for vesicular-arbuscular mycorrhizas (VAM). Patterns of colonization were identified and photographed. All plants presented evidence of vesicular-arbuscular mycorrhizal colonization. No evidence of ectomycorrhizal colonization was found. Vesicular-arbuscular mycorrhizal colonization patterns varied from single intracellular aseptate hyphae, coils, and/or appressoria, to vesicles and/or arbuscules. Results confirmed that VAM hosts are predominant in South American forests while ectomycorrhizas are extremely rare even among genera known as ectomycorrhizal in other regions of the humid tropics. Accepted: 27 August 2000     

Redefinition and phylogenetic relationships of the family Pinguipedidae (Teleostei: Perciformes)

The phylogenetic relationships of the family Pinguipedidae plus the genus Cheimarrichthys von Haast, 1874, were studied to redefine the family. Based on a phylogenetic analysis using derived characters belonging to 21 transformation series, accepting the monophyly of Pinguipedidae plus Cheimarrichthys provisionally for the operational procedure of the analysis, it was hypothesized that Cheimarrichthys is not closely related to Parapercis Bleeker, 1863, although these genera had been considered as having a close affinity. Although the Pinguipedidae and Cheimarrichthys share nine derived characters, it was determined that these characters are also found in other trachinoid families. In addition, several families, such as the Leptoscopidae, Uranoscopidae, and Trichodontidae, have many more derived characters in common with Cheimarrichthys than the pinguipedids have with that genus. The conclusion drawn here is that it is not parsimonious to recognize the monophyly of the Pinguipedidae and Cheimarrichthys based on these nine derived characters, and that these characters are not compelling enough to link these groups. The redefined Pinguipedidae is proposed to include the following five genera: Parapercis, Prolatilus Gill, 1865, Pinguipes Cuvier, 1829, Pseudopercis de Miranda-Ribeiro, 1903, and Kochichthys Kamohara, 1960. Cheimarrichthys, excluded from the Pinguipedidae, is put into its own family, Cheimarrichthyidae.     

Wood anatomy of Krameriaceae with comparisons with Zygophyllaceae: phylesis, ecology and systematics

Wood of nine species of Krameria (including all clades proposed within the genus) reveals a few characters related to infrageneric systematics; most relate primarily to ecology and habit. Wood of Krameria closely fits quantitative data reported for desert shrubs. Lack of vessel grouping correlates with the presence of densely pitted tracheids. Wood xeromorphy in Krameria may relate in part to hemiparasitism. Tracheid presence may also account for relatively low vessel density. Wood anatomy of six species of Zygophyllaceae (including both genera of Morkillioideae) is compared with that of Krameriaceae because recent phylogenies propose that these two families comprise the order Zygophyllales. Several wood characters appear to represent synapomorphies reflecting this relationship. Differences in wood anatomy between Krameriaceae and Zygophyllaceae are believed to represent autapomorphies. Notable among these include Paedomorphic Type II rays (Krameriaceae), storying (Zygophyllaceae), presence of vestured pits (Zygophyllaceae), and differentiation into vasicentric tracheids and fibre-tracheids (Zygophyllaceae). The latter feature is referable to the concept of fibre-tracheid dimorphism. Recognition of Krameriaceae as separate from Zygophyllaceae is supported by wood characters. Wood of Zygophyllales does not conflict with the idea that the order belongs to rosids, with Malpighiaceae as the outgroup of Zygophyllales.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 257–270.     

Root niche partitioning between shallow rooted succulents in a South African semi desert: implications for diversity

With a high percentage of endemics along the west coast of South Africa, especially in the family Aizoaceae, the region is considered one of the earth’s biodiversity hot spots. It has been suggested that the diversity and radiation of the Aizoaceae are coincident with low but predictable rainfall and lack of competition between species. In this study we examine the relationship between water source and the efficiency of PSII photochemistry for representative Aizoaceae and non-Aizoaceae. We do this to determine the extent to which the different genera are adapted to the frequent, low volume, precipitation characteristic of the region and to ascertain the extent to which there is competition for water. Our water isotope results show that the Aizoaceae use shallow surface water while the non-Aizoaceae use a deeper water source. We are however not able to show the extent to which the Aizoaceae utilize fog or dew. Our chlorophyll fluorescence results show that there are no differences in efficiency of PSII photochemistry between the species in the wet season. The decline from wet to dry season for the Aizoaceae is, however, more dramatic than that of the non-Aizoaceae reflecting the differences in rooting depth between the different families. These results suggest that, during the dry season, there is no competition for resources between families but there is competition between species. We conclude that the adaptation to using shallow water, coupled with susceptibility to drought of adult short lived Aizoaceae may be a, mechanism for the diversification of this family.     

The fauna of bivalves of the superfamily Pisidioidea in the small waterbodies and watercourses of Northwestern Russia (Vologda oblast)

This study of freshwater bivalves of the superfamily Pisidioidea was carried out in small waterbodies and watercourses of the central part of Vologda oblast in 2000–2005. It revealed 24 species from 13 genera and 3 families. The investigated bodies of water were grouped according to the similarity of the mollusk species composition. An analysis of the distribution of ecological and biogeographical groups of Pisidioidea was also made.     

A contribution to the rust flora (Uredinales) on Aizoaceae in southern Africa

Rust fungi on Aizoaceae in southern Africa have been examined and reported based on 27 specimens collected during a biodiversity study and previously collected herbarium specimens. Eight species including five new species have been recognized, and they are described in detail and illustrated. Together with two additional species in literature, ten species of rust fungi are now recognized on Aizoaceae in southern Africa. Part 223 in the series “Studies in Heterobasidiomycetes” from the Botanical Institute, University of Tübingen.     

Phylogeny and early evolution of the Cynipoidea (Hymenoptera)

Based on several structural and biological characteristics, the Cynipoidea can be divided into two groups, 'macrocynipoids' and 'microcynipoids'. The macrocynipoids (i.e. the family Liopteridae and the genera Austrocynips, Eileenella, Heteribalia and Ibalia ) are generally large insects that parasitize wood- or cone-boring insect larvae. The microcynipoids are smaller insects that are either phytophagous gall inducers and inquilines (Cynipidae) or parasitoids of larvae of Hymenoptera, Neuroptera or Diptera (Figitidae sensu lato , including the families Eucoilidae, Charipidae and Anacharitidae). The phylogenetic relationships among genera of macrocynipoids and between these and a sample of four genera representing the Figitidae and Cynipidae were examined by parsimony analysis of 110 external morphological characters of adults. Within the macrocynipoids, three monophyletic lineages emerged, classified here as different families: the Austrocynipidae, with a single species, Austrocynips mirabilis , the only cynipoid with a true pterostigma; the Ibaliidae, including the genera Eileenella, Ibalia and Heteribalia ; and the Liopteridae, comprising the remaining genera of macrocynipoids. The analysis further supported the monophyly of the microcynipoids and indicated that the macrocynipoids form a paraphyletic group relative to the microcynipoids, with the shortest tree suggesting the relationship (Austrocynipidae, (Ibaliidae, (Liopteridae, microcynipoids))). These results imply that cynipoids were originally parasitoids of wood-boring insect larvae and that the other modes of life evolved secondarily within the group.     

A phylogenetic analysis of higher-level gall wasp relationships (Hymenoptera: Cynipidae)

We present the most comprehensive analysis of higher-level relationships in gall wasps conducted thus far. The analysis was based on detailed study of the skeletal morphology of adults, resulting in 164 phylogenetically informative characters, complemented with a few biological characters. Thirty-seven cynipid species from thirty-one genera, including four genera of the apparently monophyletic Cynipini and almost all of the genera in the other tribes, were examined. The outgroup included exemplar species from three successively more distant cynipoid families: Figitidae (the sister group of the Cynipidae), Liopteridae and Ibaliidae. There was considerable homoplasy in the data, but many groupings in the shortest tree were nonetheless well supported, as indicated by bootstrap proportions and decay indices. Partitioning of the data suggested that the high level of homoplasy is characteristic of the Cynipidae and not the result of the amount of available phylogenetically conservative characters being exhausted. The analysis supported the monophyly of the Cynipini (oak gall wasps) which, together with the Rhoditini (the rose gall wasps), Eschatocerini and Pediaspidini formed a larger monophyletic group of gall inducers restricted to woody representatives of the eudicot subclass Rosidae. The inquilines (Synergini) were indicated to be monophyletic, whereas the Aylacini, primarily herb gall inducers, appeared as a paraphyletic assemblage of basal cynipid groups. The shortest tree suggests that the Cynipidae can be divided into three major lineages: one including the inquilines, the Aylacini genera associated with Rosaceae, and Liposthenes ; one consisting entirely of Aylacini genera, among them Aulacidea , Isocolus and Neaylax ; and one comprising the woody rosid gallers (the oak and rose gall wasps and allies), the Phanacis-Timaspis complex and the Aylacini genera associated with Papaveraceae.     

Seed coat morphology of Aizoaceae–Sesuvioideae, Gisekiaceae and Molluginaceae and its systematic significance

Macro- and micromorphological characters of the seeds of 32 species belonging to Aizoaceae (26 species), Gisekiaceae (one species) and Molluginaceae (five species) were analysed for their taxonomic value. Seed morphology is found to be of considerable taxonomic value within the taxa investigated, although additional criteria are usually necessary for distinguishing the species. However, a subgroup of Trianthema , consisting of T. cussackiana , T. megasperma , T. pilosa , T. rhynchocalyptra and T. oxycalyptra var. oxycalyptra (Aizoaceae) shares the synapomorphy of seeds with scattered idioblast cells (papillae). There is little infrageneric variation within Sesuvium and Zaleya in contrast to Trianthema , whose seeds are considerably polymorphic. The fairly different seed structures found in Aizoaceae s.s . and Molluginaceae support their treatment as two distinct families. However, the position of Lineum (Molluginaceae) remains uncertain. Moreover, seed characters support the independence of Gisekia (Gisekiaceae) in a family of its own.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 189–206.     

Perforated pit membranes in imperforate tracheary elements of some angiosperms

BACKGROUND AND AIMS: The structure of pit membranes in angiosperms has not been fully examined and our understanding about the structure is incomplete. Therefore, this study aims to illustrate the micromorphology of pit membranes in fibres and tracheids of woody species from various families. METHODS: Specimens from ten species from ten genera and eight families were prepared using two techniques and examined by field-emission scanning electron microscopy. KEY RESULTS: Interfibre pit membranes with an average diameter of <4 microm were frequently perforated or appeared to be very porous. In contrast, pit membranes in imperforate tracheary elements with distinctly bordered pits and an average diameter of >or=4 microm were homogeneous and densely packed with microfibrils. These differences were observed consistently not only among species but also within a single species in which different types of imperforate tracheary elements were present. CONCLUSIONS: This study demonstrates that the structure of interfibre pit membranes differs among cell types and the differences are closely associated with the specialization of the fibre cells. It is suggested that perforated pit membranes between specialized fibres contribute to the dehydration of the fibre cells at or soon after maturation.