The polyphyletic origin of the "Cheilostomata" (Bryszoa)

The relative appearance of the parietal muscles in the development of the zooids has been studied in several ctenostomatous and “cheilostomatous” species. A comparison of the different on-togenetical sequences demonstrated that a “cheilostomatous” type of organization of the zooids with a great probability has been achieved in minimum three times independentl and originated from different ctenostomatous sub-grous: the Membranidea from plesiomorgic victorelloids (ancestors of Bulbella with not yet developed peristomial tube), the Inoviceiata (Aetea) from advanced forms of victorelloids with reduced primary parietal muscles (perhaps stcies related to Pottsiella), and Penetrantia from arachnidioid or vesicularioid ancestors (?). Therefore, the classical orders ^α“Ctenostomata” and “Cheilostomata” represent only “stage groups” but no monohyletic systematical units. Because of the new concept and interpretation I propose a new name for the united group: Cteno-Cheilostomata, supra-ord. nov.     

DIFFERING ONTOGENETIC ORIGINS OF PCR (“KRANZ”) SHEATHS IN LEAF BLADES OF C4 GRASSES (POACEAE)

The origin and early development of procambium and associated ground meristem of major and minor veins have been examined in the leaf blades of seven C₄ grass species, representing different taxonomic groups and the three recognized biochemical C₄ types (NAD-ME, PCK, and NADP-ME). Comparisons were made with the C₃ species, Festuca arundinacea. In “double sheath” (XyMS+) species (Panicum effusum, Eleusine coracana, and Sporoboìus elongatus), the procambium of major veins gives rise to xylem, phloem, and a mestome sheath; associated ground meristem differentiates into PCA (“C₄ mesophyll”) tissue and the PCR (“Kranz”) sheath. Development in the C₃ species parallels this pattern, except that associated ground meristem differentiates into mesophyll and a parenchymatous bundle sheath. In contrast, major vein procambium of “single sheath” (XyMS–) species (Panicum bulbosum, Digitaria brownii, and Cymbopogon procerus) differentiates into xylem, phloem and a PCR sheath; associated ground meristem gives rise to PCA tissue. These observations of major vein development support W. V. Brown's hypothesis that the PCR sheaths of “double sheath” (XyMS+) C₄ grasses are homologous with the parenchymatous bundle sheaths of C₃ grasses, while in “single sheath” (XyMS–) C₄ species they are homologous with the mestome sheath. Although there are some similarities in the development of the major and minor vascular bundle procambium in the C₄ species examined, the ontogeny of the smaller minor veins is characterized by a precocious delineation of the PCR sheath layer that may even precede the appearance of the distinctive cytological features of ground meristem and procambium. This contracted development in minor veins appears to be related to their close spacing in mature leaves and to their comparatively late appearance during leaf ontogeny.     

Morphology of ctenostome bryozoans: 1. Arachnidium fibrosum

The morphology of ctenostome bryozoans remains little investigated with only few species having been subject to more detailed studies. From all the seven main different superfamilies, only few representatives have been studied. The superfamily Arachnidioidea has particularly been neglected concerning detailed morphological and histological details. So far, not a single analysis specifically studied a representative of the family Arachnidiidae. Arachnidium-like forms have, however, often been regarded as potential cheilostome ancestors, the most successful group of bryozoans to date. The lack of any morphological data on this family called for a detailed investigation of one of its representatives. Hence, we analysed the general morphology and histology of Arachnidium fibrosum. Most striking morphological features previously unrecognized are a cardiac constrictor, previously almost unknown in the family, a single pair of apertural muscles consisting of proximal parieto-diaphragmatic and distal parieto-vestibular muscles, six pairs of duplicature bands, a lophophoral anus and retractor muscles attaching to the foregut. Although comparative data are limited, there seem to be two distinct different clades of arachnidiid ctenostomes that are characterized by their aperture and details of gut morphology. Further analysis of additional arachnidioidean species are required to confirm this.     

The interpretation of voltage-concentration relations

The dependence of a cell's membrane potential upon ion concentrations is often described via a Goldman constant field equation (with coefficients called permeabilities) or what may be called the Hodgkin-Horowicz equation. The latter is derived by assuming that different ion species traverse separate pathways of at least formally constant conductance. If one assumes truly constant “permeabilities” or “conductances”, then these two equations have essentially different forms. So the literature has been culled for voltage-concentration data which unambiguously fit an equation of one of these two forms. Eight or nine are found to fit a Hodgkin-Horowicz relation; none, a Goldman one. This adds to the evidence that different ion species traverse relatively separate pathways through cell membranes (and that these pathways are long compared to a Debye length). It also indicates the desirability of generally describing voltage-concentration data with a Hodgkin-Horowicz relation rather than a Goldman one.     

Mutants highlight the modular control of butterfly eyespot patterns

SUMMARY The eyespots on butterfly wings are thought to be serially homologous pattern elements. Yet eyespots differ greatly in number, shape, color, and size, within and among species. To what extent do these serially homologues have separate developmental identities, upon which selection acts to create diversity? We examined x‐ray–induced mutations for the eyespots of the nymphalid butterfly Bicyclus anynana that highlight the modular control of these serially homologous wing pattern elements. These mutations reduce or eliminate individual eyespots, or groups of eyespots, with no further effect on the wing color pattern. The collection of mutants highlights a greater potential developmental repertoire than that observed across the genus Bicyclus. We studied in detail one such mutation, of codominant effect, that causes the elimination of two adjacent eyespots on the ventral hindwing. By analyzing the expression of genes known to be involved in eyespot formation, we found an alteration in the differentiation of the “organizing” cells at the eyespot's center. No such cells differentiate in the wing subdivisions lacking the two eyespots in the mutants. We propose several developmental models, based on wing compartmentalization in Drosophila, that provide the first framework for thinking about the molecular evolution of butterfly wing pattern modularity.     

Impact of the invasion of the imported fire ant

The impact of the imported fire ant (IFA) is complex, in large part, because several very different species of “Fire Ants” have invaded and one of these has two forms, all of which are hard to separate by the public, as well as, some investigators not focused on the ant. Each of these different “IFA” species and forms differ in their impact. Further, these ants impact a number of “things” ranging from the environment and wildlife (plants and animals) as well as people, their environment and infrastructure. In addition, they can not only lead to death of living things (including people), but they can destroy many aspects of our environment and infrastructure at the cost of millions of dollars. But there are some beneficial aspects and some people can make many thousands of dollars due to their presence. This is an attempt to look at these issues.     

Differences in evolutionary history translate into differences in invasion success of alien mammals in South Africa

Attempts to investigate the drivers of invasion success are generally limited to the biological and evolutionary traits distinguishing native from introduced species. Although alien species introduced to the same recipient environment differ in their invasion intensity – for example, some are “strong invaders”; others are “weak invaders” – the factors underlying the variation in invasion success within alien communities are little explored. In this study, we ask what drives the variation in invasion success of alien mammals in South Africa. First, we tested for taxonomic and phylogenetic signal in invasion intensity. Second, we reconstructed predictive models of the variation in invasion intensity among alien mammals using the generalized linear mixed‐effects models. We found that the family Bovidae and the order Artiodactyla contained more “strong invaders” than expected by chance, and that such taxonomic signal did not translate into phylogenetic selectivity. In addition, our study indicates that latitude, gestation length, social group size, and human population density are only marginal determinant of the variation in invasion success. However, we found that evolutionary distinctiveness – a parameter characterising the uniqueness of each alien species – is the most important predictive variable. Our results indicate that the invasive behavior of alien mammals may have been “fingerprinted” in their evolutionary past, and that evolutionary history might capture beyond ecological, biological and life‐history traits usually prioritized in predictive modeling of invasion success. These findings have applicability to the management of alien mammals in South Africa.     

Cranial muscles of the anurans leiopelma hochstetteri and ascaphus truei and the homologies of the mandibular adductors in lissamphibia and other gnathostomes

The frogs Ascaphus truei and Leiopelma hochstetteri are members of the most basal lineages of extant anurans. Their cranial muscles have not been previously described in full and are investigated here by dissection. Comparison of these taxa is used to review a controversy regarding the homologies of the jaw adductor muscles in Lissamphibia, to place these homologies in a wider gnathostome context, and to define features that may be useful for cladistic analysis of Anura. A new muscle is defined in Ascaphus and is designated m. levator anguli oris. The differences noted between Ascaphus and Leiopelma are in the penetration of the jaw adductor muscles by the mandibular nerve (V³). In the traditional view of this anatomy, the paths of the trigeminal nerve branches define homologous muscles. This scheme results in major differences among frogs, salamanders, and caecilians. The alternative view is that the topology of origins, insertions, and fiber directions are defining features, and the nerves penetrate the muscle mass in a variable way. The results given here support the latter view. A new model is proposed for Lissamphibia, whereby the adductor posterior (levator articularis) is a separate entity, and the rest of the adductor mass is configured around it as a folded sheet. This hypothesis is examined in other gnathostomes, including coelacanth and lungfish, and a possible sequence for the evolution of the jaw muscles is demonstrated. In this system, the main jaw adductor in teleost fish is not considered homologous with that of tetrapods. This hypothesis is consistent with available data on the domain of expression of the homeobox gene engrailed 2, which has previously not been considered indicative of homology. Terminology is discussed, and “adductor mandibulae” is preferred to “levator mandibulae” to align with usage in other gnathostomes. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Characterization of topological keystone species: Local,global and “meso-scale” centralities in food webs

An important question in the network representation of ecological systems is to determine how direct and indirect interactions between species determine the positional importance of species in the ecosystem. Here we present a quantitative analysis of the similarities and differences of six different topological centrality measures as indicators of keystone species in 17 food webs. These indicators account for local, global and “meso-scale” – intermediate between local and global – topological information about species in the food webs. Using factor analysis we shown that most of these centrality indices share a great deal of topological information, which range from 75% to 96%. A generalized keystone indicator is then proposed by considering the factor loadings of the six-centrality measures, which contains most of the information encoded by these indices. However, the individual ordering of species according to these criteria display significant differences in most food webs. We simulate the effects of species extinction by removing species ranked according to a local and a “meso-scale” centrality indicator. The differences observed on three network characteristics – size, average distance and clustering coefficient of the largest component – after the removal of the most central nodes indicate that the consideration of these indices have different impacts for the ranking of species with conservational biology purposes. The “meso-scale” indicator appears to play an important role in determining the relative importance of species in epidemic spread and parasitism rates.     

Suppression of Homoeologous Pairing by <Emphasis Type="Italic">B</Emphasis> Chromosomes in a <Emphasis Type="Italic">Lolium</Emphasis> Species Hybrid

INTERSPECIFIC hybridization together with polyploidy has been an important force in the evolution of many of our graminaceous crop plants. Both wheat (Triticum aestivum) and oats (Avena sativa), for example, are natural allohexaploids derived in each case from the hybridization of three separate but related diploid species. The efforts of plant breeders to synthesize stable and fertile polyploids of this kind have, on the whole, been unsuccessful. The main reason for this is that whereas meiosis in natural allopolyploids such as wheat is extremely regular this is not the case with “synthetic” polyploids. In wheat precise control over pairing at meiosis is achieved by a gene or a cluster of genes on chromosome SB. The gene acts by restricting the pairing to homologous chromosomes with the result that only bivalents are formed, disjunction is regular and inheritance is completely disomic^1,2. In the artificial polyploids at pachytene there is pairing between both homologous chromosomes (from the same species) and “corresponding” homoeologous chromosomes (from different species). The result is an extremely irregular metaphase 1 comprising multivalents and univalents as well as bivalents. Segregation is irregular and a certain degree of infertility is inevitable.     

Invasion success and threat status: two sides of a different coin?

The characteristics possessed by invasive species have been suggested to be the reverse of those possessed by species threatened with extinction, such that relationships of species’ traits to invasion success should be opposite in sign to relationships of the same traits to extinction threat. A recent study (Jeschke, J. M. and Strayer, D. L. 2008. Are threat status and invasion success two sides of the same coin? – Ecography 31: 124–130) found no evidence for this “two‐sides‐of‐the‐same‐coin” hypothesis but compared characteristics of species in each taxon that were invasive to a control group consisting of all other species. A different view of the “two‐sides‐of‐the‐same‐coin” hypothesis may be obtained if the characters of invasive species are compared to those of a control group consisting of species that have not invaded despite actually being introduced. Here, we show that changing the control group for comparison with invasive species does not change the lack of support for the “two‐sides‐of‐the‐same‐coin” hypothesis but does change views about which specific traits are consistent with the hypothesis.     

Ontogeny of the cranial musculature in Corydoras aeneus Callichthyidae,Siluriformes

A complete study of the early ontogeny of the cranial muscles of Corydoras aeneus (Callichthyidae) was undertaken and results were compared with those for the loricariid Ancistrus cf. triradiatus. This comparison reveals a high degree of similarity in the ontogeny of both species' cranial muscles. Both species lack a musculus protractor hyoidei, and the musculus intermandibularis posterior is divided into two different parts that have partly obtained a novel function (serving the lower lip) in A. cf. triradiatus. A similar increase in muscular complexity in this species is found in the dorsal constrictor of the hyoid muscle plate. This constrictor gives rise to the same muscles in both C. aeneus and A. cf. triradiatus, but in A. cf. triradiatus the musculus levator operculi later hypertrophies. In C. aeneus the musculus extensor tentaculi forms a single muscle diverging posteriorly, whereas in A. cf. triradiatus the musculus extensor tentaculi differentiates into two separate bundles. Also, a loricariid neoformation is present called the musculus levator tentaculi.     

Morphological diversity in the postnatal skull development in representatives of two families of rodents (Spalacidae,Castoridae, Rodentia)

This is the first study to describe the results of measurement of three information parameters of morphological diversity (entropy, the measure of organization, and the Kullback-Leibler divergence) in the course of postnatal development of the skull in the populations of two rodent species (greater mole rat (Spalax microphthalmus Guld.) and Eurasian beaver (Castor fiber (L.)). The terms “morphosystem” and “morphological space” and its structure are introduced. Within the framework of the developed approach, “morphological diversity” is considered as a variable associated with the morphological space structure. Testing the hypothesis of the dominance of self-organization processes and an increase in the organization of the morphological diversity of the skull in the course of ontogeny showed its inconsistency. The morphosystem of the skull of the studied species undergoes transitions between more organized and less organized states, periodically approaching and departing from the “steady state.” Such dynamics characterizes the morphosystem of the skull as a dynamic and nonlinear system.     

Paraphysomonas faveolata sp. nov. (Chrysophyceae), a fourth marine species with meshwork body-scales

Paraphysomonas faveolata sp. nov., the eighth described species of this genus of colourless chrysophycean flagellates, has heterokont flagellation, parabasal nucleus and silicified body-scales. It is the fourth known species with meshwork scales, these being of two types: flat “cobweb” scales and scales with a planar “honeycombed” extension arising from a “cobweb” base. The organism is compared with the other species of the genus and the case considered for placing forms with meshwork scales in a new genus, separate from forms with spined scales. This step is not taken and the taxonomic status of the genus is discussed in relation to the Ochromonadaceae and other genera of the Synuraceae.     

Ontogeny of the jaw and maxillary barbel musculature in the armoured catfish families Loricariidae and Callichthyidae (Loricarioidea,Siluriformes), with a discussion on muscle homologies

The neotropical loricarioid catfishes include six families, the most species‐rich of which are the Callichthyidae and the Loricariidae. Loricariidae (suckermouth armoured catfishes) have a highly specialized head morphology, including an exceptionally large number of muscles derived from the adductor mandibulae complex and the adductor arcus palatini. Terminology of these muscles varies among the literature, and no data exist on their ontogenetic origin. A detailed examination of the ontogeny of both a callichthyid and a loricariid representative now reveals the identity of the jaw and maxillary barbel musculature, and supports new hypotheses concerning homologies. The adductor mandibulae muscle itself is homologous to the A1‐OST and A3′ of basal catfishes, and the A3′ has given rise to the newly evolved loricariid retractor veli as well. The A2 and A3″ have resulted in the retractor tentaculi of Callichthyidae and the retractor premaxillae of Loricariidae. Thus, these two muscles are shown to be homologous. In Loricariidae, the extensor tentaculi consists of two separate muscles inserting on the autopalatine, and evidence is given on the evolutionary origin of the loricariid levator tentaculi (previously and erroneously known as retractor tentaculi) from the extensor tentaculi, and not the adductor mandibulae complex. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 76–96.     

Guest-Editorial Introduction: Converging Evolutionary Patterns in Life and Culture

The natural world demonstrates signs of spatial–temporal order, an order that appears to us through a series of recognizable, recurring and consecutive patterns, i.e. regularities in forms, functions, behaviors, events and processes. These patterns lend insight into the modes and tempos of evolution and thus into the units, levels, and mechanisms that underlie the evolutionary hierarchy. Contributors to this special issue analyze converging patterns in the biological and sociocultural realm across and beyond classic divisions between micro- and macro-evolution; horizontal/reticulate and vertical evolution; phylogeny, ontogeny and ecology; synchronic and diachronic sociocultural and linguistic research; and tree and network diagrams. Explanations are sought in complexity theory, major transitions of evolution, and process and mechanism approaches to change; and consequences for notions such as “life”, “species”, “biological individuality”, “units” and “levels” of evolution are given.     

The Taxonomic Status and Intraspecific Differentiation of the Black Sea Horse Mackerel, <Emphasis Type="Italic">Trachurus mediterraneus ponticus</Emphasis> (Aleev, 1956) (Carangidae)

The taxonomic status of the horse mackerel, Trachurus mediterraneus ponticus (Aleev, 1956), which inhabits the Black Sea, has been clarified based on the analysis of variation in the nucleotide sequence of the mtDNA cytochrome b (Cyt-b) locus. A comparison of this species with the horse mackerel from the Mediterranean basin and the World Ocean has shown that the Black Sea horse mackerel is neither an independent species nor a subspecies and can only be qualified as the species Trachurus mediterraneus (Steindachner, 1868) distributed throughout the Mediterranean Sea basin. A hypothesis has been made about the possible cause of the origin and existence of two forms, “large” and “small”, of the horse mackerel. By using the technique of calculating ontogenetic trajectories, it has been found that these are two morpho-ecological forms, whose differentiation is most likely determined by the type of feeding.