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Previous Hypotheses (previous + hypothesis)
Selected AbstractsIndiscriminate nursing in communal breeders: a role for genomic imprintingECOLOGY LETTERS, Issue 3 2003Alexandre Roulin Abstract In several communally nesting mammal species, females indiscriminately nurse each others' offspring. Previous hypotheses have suggested that the inability to recognize one's own young during lactation is the result of costs incurred from recognition errors. Here, we propose an alternative hypothesis based on sexual conflict theory and genomic imprinting. In polygynous species, males copulate with several females that may later breed communally. Under such conditions, males benefit from indiscriminate nursing of all their offspring and the reduced risk of female infanticide. This may have selected for paternally expressed genes that suppress kin recognition during lactation. [source] The Multipredator Hypothesis and the Evolutionary Persistence of Antipredator BehaviorETHOLOGY, Issue 3 2006Daniel T. Blumstein Invited Review Abstract Isolation from predators affects prey behavior, morphology, and life history, but there is tremendous variation in the time course of these responses. Previous hypotheses to explain this variation have limited predictive ability. I develop a ,multipredator' hypothesis to explain the evolutionary persistence of antipredator behavior after the loss of some, but not all, of a species' predators. The hypothesis assumes pleiotropy, whereby elements of antipredator behavior may function in non-predatory situations, and linkage, such that genes influencing the expression of antipredator behavior do not assort independently. The hypothesis is restricted to species with multiple predators (most species) and aims to predict the conditions under which antipredator behavior will persist following the loss of one or more of a species' predators. I acknowledge that the relative costs of non-functional antipredator behavior will influence the likelihood of linkage and therefore persistence. The hypothesis makes two main predictions. First, genes responsible for antipredator behavior will not be scattered throughout the genome but rather may be found close together on the same chromosome(s). Secondly, the presence of any predators may be sufficient to maintain antipredator behavior for missing predators. Advances in behavioral genetics will allow tests of the first prediction, while studies of geographic variation in antipredator behavior provide some support for the second. [source] THE HISTORY OF A NEARCTIC COLONIZATION: MOLECULAR PHYLOGENETICS AND BIOGEOGRAPHY OF THE NEARCTIC TOADS (BUFO)EVOLUTION, Issue 11 2004Gregory B. Pauly Abstract Previous hypotheses of phylogenetic relationships among Nearctic toads (Bufonidae) and their congeners suggest contradictory biogeographic histories. These hypotheses argue that the Nearctic Bufo are: (1) a polyphyletic assemblage resulting from multiple colonizations from Africa; (2) a paraphyletic assemblage resulting from a single colonization event from South America with subsequent dispersal into Eurasia; or (3) a monophyletic group derived from the Neotropics. We obtained approximately 2.5 kb of mitochondrial DNA sequence data for the 12S, 16S, and intervening valine tRNA gene from 82 individuals representing 56 species and used parametric bootstrapping to test hypotheses of the biogeographic history of the Nearctic Bufo. We find that the Nearctic species of Bufo are monophyletic and nested within a large clade of New World Bufo to the exclusion of Eurasian and African taxa. This suggests that Nearctic Bufo result from a single colonization from the Neotropics. More generally, we demonstrate the utility of parametric bootstrapping for testing alternative biogeographic hypotheses. Through parametric bootstrapping, we refute several previously published biogeographic hypotheses regarding Bufo. These previous studies may have been influenced by homoplasy in osteological characters. Given the Neotropical origin for Nearctic Bufo, we examine current distributional patterns to assess whether the Nearctic-Neotropical boundary is a broad transition zone or a narrow boundary. We also survey fossil and paleogeographic evidence to examine potential Tertiary and Cretaceous dispersal routes, including the Paleocene Isthmian Link, the Antillean and Aves Ridges, and the current Central American Land Bridge, that may have allowed colonization of the Nearctic. [source] Mainland colonization by island lizardsJOURNAL OF BIOGEOGRAPHY, Issue 6 2005Kirsten E. Nicholson Abstract Aim, We investigate biogeographic relationships within the lizard genus Anolis Daudin, 1802 to test the hypothesis that the mainland (Central and South American) Norops-clade species descended from a West Indian Anolis ancestor. Previous hypotheses have suggested that close island relatives of mainland Norops species (the Cuban Anolis sagrei and Jamaican A. grahami series) represent over-water dispersal from a mainland ancestor. These previous hypotheses predict that the A. sagrei and A. grahami series should be phylogenetically nested within a Norops clade whose ancestral geography traces to the mainland. If Norops is West Indian in origin, then West Indian species should span the deepest phylogenetic divergences within the Norops clade. Location, Central and South America and West Indian islands. Methods, The phylogenetic relationships of Anolis lizards are reconstructed from aligned DNA sequences using both parsimony and Bayesian approaches. Hypotheses are tested in two ways: (1) by reconstructing the ancestral geographic location for the Norops clade using Pagel & Lutzoni's (2002) Bayesian approach, and (2) by testing alternative topological arrangements via Wilcoxon Signed-Ranks tests (Templeton, 1983) and Shimodaira,Hasegawa tests (Shimodaira & Hasegawa, 1999). Results, Our evidence supports an origin of mainland Norops anoles from a West Indian ancestor. A West Indian ancestor to the Norops clade is statistically supported, and alternatives to the biogeographic pattern [Cuban (Jamaican, Mainland)] are statistically rejected by Shimodaira,Hasegawa tests, although not by Wilcoxon Signed-Ranks tests. Main conclusions, Our data support the hypothesis of a West Indian origin for mainland Norops. This result contradicts previous hypotheses and suggests that island forms may be an important source for mainland biodiversity. [source] Bite forces, canine strength and skull allometry in carnivores (Mammalia, Carnivora)JOURNAL OF ZOOLOGY, Issue 2 2005Per Christiansen Abstract Skull variables were analysed for allometry patterns in 56 species of extant carnivores. As previously reported, many skull variables scale near isometrically with either skull length or lower jaw length. The maximal gape angle scales insignificantly (P<0.05) with skull size, but the clearance between the canines shows a significant relationship with skull size and scales near isometrically. Maximal bite forces were estimated from geometrical cross-sectional areas of dried skulls, and the bending strength of the canines was computed by modelling the canines as a cantilevered beam of solid, homogeneous material with an elliptical cross section. Previous hypotheses of large taxon differences in canine bending strengths, so that felids have stronger canines than canids, are corroborated when actual bite forces at the upper canine are ignored. Incorporation of bite force values, however, nullifies the differences in canine bending strength among felids and canids, and ursids seem to have stronger canines than felids. This is probably because of the significantly longer canines of felids compared to canids and ursids, and the generally high bite forces of felids. [source] Origin of planktotrophy,evidence from early molluscsEVOLUTION AND DEVELOPMENT, Issue 4 2006Alexander Nützel SUMMARY The size of early ontogenetic shells (protoconchs) of ancient benthic molluscs suggests that feeding larvae occurred at about 490 myr (approximately, transition from Cambrian to Ordovician). Most studied Ordovician protoconchs were smaller than Cambrian ones, indicating smaller Ordovician eggs and hatchlings. This suggests substitution of nutritious reserve matter such as yolk by plankton as an energy source for larvae. The observed size change represents the first direct empiric evidence for a late Cambrian to Ordovician switch to planktotrophy in invertebrate larvae. It corroborates previous hypotheses about a possible polyphyly of planktotrophy. These hypotheses were primarily based on molecular clock data of extant clades with different types of larva, change in the overall body size, as well as increasing predation pressure on Early Paleozoic sea floors. The Early Ordovician is characterized by an explosive radiation of benthic suspension feeders and it was suggested that planktotrophy would prolongate escape from benthic predation on hatchlings. This biological escalation hypothesis does not fully explain why planktotrophy and suspension feeding became important at the same time, during a major biodiversification. An additional factor that probably included availability of nutrients must have played a role. We speculate that an increasing nutrient supply and availability of photoautotrophic plankton in world oceans have facilitated both planktotrophy and suspension feeding, which does not exclude a contemporaneous predation-driven escalation. It is very likely that the evolution of planktotrophy as well as increasing predation contributed to the Ordovician radiation. [source] Vestigial prototroch in a basal nemertean, Carinoma tremaphoros (Nemertea; Palaeonemertea)EVOLUTION AND DEVELOPMENT, Issue 4 2004S. A. Maslakova Summary Nemerteans have been alleged to belong to a protostome clade called the Trochozoa that includes mollusks, annelids, sipunculids, echiurids, and kamptozoans and is characterized by, among other things, the trochophore larva. The trochophore possesses a prototroch, a preoral belt of specialized ciliary cells, derived from the trochoblast cells. Nemertea is the only trochozoan phylum for which presence of the trochophore larva possessing a prototroch had never been shown. However, so little is known about nemertean larval development that comparing it with development of other trochozoans is difficult. Development in the nemertean clade Pilidiophora is via a highly specialized planktonic larva, the pilidium, and most of the larval body is lost during a drastic metamorphosis. Other nemerteans (hoplonemerteans and palaeonemerteans) lack a pilidium, and their development is direct, forming either an encapsulated or planktonic "planuliform" larva, producing a juvenile without a dramatic change in body plan. We show that early in the development of a member of a basal nemertean assemblage, the palaeonemertean Carinoma tremaphoros, large squamous cells cover the entire larval surface except for the apical and posterior regions. Although apical and posterior cells continue to divide, the large surface cells cleavage arrest and form a contorted preoral belt. Based on its position, cell lineage, and fate, we suggest that this belt corresponds to the prototroch of other trochozoans. Lack of differential ciliation obscures the presence of the prototroch in Carinoma, but differentiation of the trochoblasts is clearly manifested in their permanent cleavage arrest and ultimate degenerative fate. Our results allow a meaningful comparison between the development of nemerteans and other trochozoans. We review previous hypotheses of the evolution of nemertean development and suggest that a trochophore-like larva is plesiomorphic for nemerteans while a pilidium type of development with drastic metamorphosis is derived. [source] Dynamics of common wasps in New Zealand beech forests: a model with density dependence and weatherJOURNAL OF ANIMAL ECOLOGY, Issue 4 2002N. D. Barlow Summary 1Nest densities of the common wasp ( Vespula vulgaris (L.)) were monitored at six sites for 13 years in the honeydew-rich southern beech ( Nothofagus spp.) forests of New Zealand's South Island. 2Densities of wasp nests were among the highest in the world, up to 30 ha ,1 , and at any one site varied approximately twofold over the study period. 3Strong but not overcompensating density dependence was identified, together with a negative effect of spring rainfall. 4The density dependence appeared to act from the number of autumn queens produced during one year to the number of mature (autumn) nests the next year, rather than through variations in queen production per nest. The same stage was also responsible for most of the variability in autumn nest numbers from year to year, with queen production per nest contributing less. 5Yearly changes in nest density could be summarized by a simple Ricker model including both density dependence and weather, thereby incorporating both previous hypotheses for the determination of wasp abundance. [source] Comparative phylogeography of pitvipers suggests a consensus of ancient Middle American highland biogeographyJOURNAL OF BIOGEOGRAPHY, Issue 1 2009Todd A. Castoe Abstract Aim, We used inferences of phylogenetic relationships and divergence times for three lineages of highland pitvipers to identify broad-scale historical events that have shaped the evolutionary history of Middle American highland taxa, and to test previous hypotheses of Neotropical speciation. Location, Middle America (Central America and Mexico). Methods, We used 2306 base pairs of mitochondrial gene sequences from 178 individuals to estimate the phylogeny and divergence times of New World pitviper lineages, focusing on three genera (Atropoides, Bothriechis and Cerrophidion) that are broadly co-distributed across Middle American highlands. Results, We found strong correspondence across three highland lineages for temporally and geographically coincident divergences in the Miocene and Pliocene, and further identified widespread within-species divergences across multiple lineages that occurred in the early,middle Pleistocene. Main conclusions, Available data suggest that there were at least three major historical events in Middle America that had broad impacts on species divergence and lineage diversification among highland taxa. In addition, we find widespread within-species genetic structure that may be attributable to the climatic changes that affected gene flow among highland taxa during the middle,late Pleistocene. [source] Mainland colonization by island lizardsJOURNAL OF BIOGEOGRAPHY, Issue 6 2005Kirsten E. Nicholson Abstract Aim, We investigate biogeographic relationships within the lizard genus Anolis Daudin, 1802 to test the hypothesis that the mainland (Central and South American) Norops-clade species descended from a West Indian Anolis ancestor. Previous hypotheses have suggested that close island relatives of mainland Norops species (the Cuban Anolis sagrei and Jamaican A. grahami series) represent over-water dispersal from a mainland ancestor. These previous hypotheses predict that the A. sagrei and A. grahami series should be phylogenetically nested within a Norops clade whose ancestral geography traces to the mainland. If Norops is West Indian in origin, then West Indian species should span the deepest phylogenetic divergences within the Norops clade. Location, Central and South America and West Indian islands. Methods, The phylogenetic relationships of Anolis lizards are reconstructed from aligned DNA sequences using both parsimony and Bayesian approaches. Hypotheses are tested in two ways: (1) by reconstructing the ancestral geographic location for the Norops clade using Pagel & Lutzoni's (2002) Bayesian approach, and (2) by testing alternative topological arrangements via Wilcoxon Signed-Ranks tests (Templeton, 1983) and Shimodaira,Hasegawa tests (Shimodaira & Hasegawa, 1999). Results, Our evidence supports an origin of mainland Norops anoles from a West Indian ancestor. A West Indian ancestor to the Norops clade is statistically supported, and alternatives to the biogeographic pattern [Cuban (Jamaican, Mainland)] are statistically rejected by Shimodaira,Hasegawa tests, although not by Wilcoxon Signed-Ranks tests. Main conclusions, Our data support the hypothesis of a West Indian origin for mainland Norops. This result contradicts previous hypotheses and suggests that island forms may be an important source for mainland biodiversity. [source] Zoogeography of the southern African ascidian faunaJOURNAL OF BIOGEOGRAPHY, Issue 12 2004Carmen Primo Abstract Aim, To describe the biogeography of the ascidian fauna of southern Africa, to compare the results obtained with those reported for other fauna and flora of the same region, and to speculate about the origin of ascidians in the region. Location, Southern Africa extending over 4000 km from Mossâmedes (15° S,12° E) to Inhaca Island (26°30, S,33° E), including Vema Seamount (31°40, S,8 °20, E), Amsterdam-Saint Paul Islands (38° S,77°30, E) and the Tristan-Gough Islands (38° S,12°20, W). Methods, We constructed a presence/absence matrix of 168 species for 26 biogeographical divisions, 21 classical biogeographical regions described by Briggs (Marine zoogeography, McGraw-Hill, New York, 1974) and five provinces within the southern African region. We considered the following limits and divisions into provinces for the southern African region: Namibia, Namaqua, Agulhas and Natal as proposed by Branch et al. (Two oceans. A guide to the marine life of southern Africa, David Philip Publishers, 1994), and the West Wind Drift Islands province (WWD) according to Briggs (Global biogeography, Elsevier Health Sciences, Amsterdam, 1995). To examine the biogeographical structure, species and divisions were classified using cluster analysis (based on UPGMA as the aggregation algorithm) with the Bray,Curtis index of similarity. This classification was combined with MDS ordination. Main conclusions, Four main groups were obtained from the analysis of affinities among species: (1) species present in the WWD, separated by a high percentage of endemisms and a low number of species with a southern African distribution. Moreover, in the light of the species distribution and the results of further analysis, which revealed that they are completely separated and not at all related to the southern African region, it appears that there are no close relationships among the different islands and seamounts of the West Wind Drift Island province. This province was therefore removed from the remaining analyses; (2) species with a wide distribution; (3) species of colder waters present in Namaqua and Agulhas provinces, a transitional temperate area in which gradual mixing and replacement of species negate previous hypotheses on the existence of a marked distributional break at Cape of Good Hope; (4) species of warmer waters related to Natal province. The classification into biogeographical components was dominated by the endemic (47%), Indo-Pacific (25%) and cosmopolitan (13%) components. The analysis of affinities among biogeographical areas separated Namibia from the rest of the southern African provinces and showed that it was related to some extent to the Antarctic region because of the cold-temperate character of the province and the low sampling effort; Namaqua, Agulhas and Natal were grouped together and found to be closely related to the Indo-West Pacific region. In general, our results were consistent with those obtained for other southern African marine invertebrates. The frequency distribution of solitary/colonial strategies among provinces confirmed the domination of colonial organisms in tropical regions and solitary organisms in colder regions. Finally, we speculate that the southern African ascidian fauna mainly comprises Indo-Pacific, Antarctic and eastern Atlantic ascidians. [source] Phylogeography of the northern hogsucker, Hypentelium nigricans (Teleostei: Cypriniformes): genetic evidence for the existence of the ancient Teays RiverJOURNAL OF BIOGEOGRAPHY, Issue 8 2003Peter B. Berendzen Abstract Aim, To assess the roles of dispersal and vicariance in shaping the present distribution and diversity within Hypentelium nigricans, the northern hogsucker (Teleostei: Cypriniformes). Location, Eastern United States. Methods, Parsimony analyses, Bayesian analyses, pairwise genetic divergence and mismatch plots are used to examine patterns of genetic variation across H. nigricans. Results, Species relationships within the genus Hypentelium were consistent with previous hypotheses. However, relationships between haplotypes within H. nigricans revealed two deeply divergent groups, a clade containing haplotypes from the New and Roanoke rivers (Atlantic Slope) plus Interior Highlands and upper Mississippi River and a clade containing haplotypes from the Eastern Highlands, previously glaciated regions of the Ohio and Wabash rivers, and the Amite and Homochitto rivers of south-western Mississippi. Main conclusions, The phylogenetic history of Hypentelium was shaped by old vicariant events associated with erosion of the Blue Ridge and separation of the Mobile and Mississippi river basins. Within H. nigricans two clades existed prior to the Pleistocene; a widespread clade in the pre-glacial Teays-Mississippi River system and a clade in Cumberland and Tennessee rivers. Pleistocene events fragmented the Teays-Mississippi fauna. Following the retreat of the glaciers H. nigricans dispersed northward into previously glaciated regions. These patterns are replicated in other clades of fishes and are consistent with some of the predictions of Mayden's (Systematic Zoology, 37, 329, 1988) pre-Pleistocene vicariance hypothesis. [source] Muscular anatomy of the millipede Phyllogonostreptus nigrolabiatus (Diplopoda: Spirostreptida) and its bearing on the millipede "thorax"JOURNAL OF MORPHOLOGY, Issue 3 2002Heather M. Wilson Abstract The muscular anatomy of the millipede Phyllogonostreptus nigrolabiatus (Newport, 1844) (Diplopoda; Spirostreptida; Harpagophoridae) is comprehensively surveyed. The musculature of the first three postcollum pleurotergites, the "thorax," and their associated appendages was found to be more complex than that of the postthoracic rings. It is hypothesized that the musculature of the postthoracic segments is derived relative to that of the thoracic segments, which retain primitively free sternites and are not diplosegments. This hypothesis is discussed relative to previous hypotheses positing that the anteriormost three leg-bearing rings in millipedes are diplosegments. The musculature of spirostreptid gonopods is described in detail for the first time. Comparison of the cephalic musculature is made with previously described musculature in Julida showing that, while many aspects of the musculature are conserved, there exist interordinal differences, documenting the potential utility of comparative anatomical studies for resolving millipede phylogeny. J. Morphol. 251:256,275, 2002. © 2002 Wiley-Liss, Inc. [source] Geographical patterns of mitochondrial DNA variation in Apis mellifera iberiensis (Hymenoptera: Apidae)JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2008F. Cánovas Abstract An extensive survey of mitochondrial haplotypes in honeybee colonies from the Iberian Peninsula has corroborated previous hypotheses about the existence of a joint clinal variation of African (A) and west European (M) evolutionary lineages. It has been found that the Iberian Peninsula is the European region with the highest haplotype diversity (12 haplotypes detected of the M lineage and 10 of the A lineage). The frequency of A haplotypes decreases in a SW-NE trend, while that of M haplotypes increases. These results are discussed in relation to hypotheses about the African origin of Apis mellifera and an early colonization of west Europe during intermediate Pleistocene glaciation events, followed by a regional differentiation. The extant pattern of haplotype frequency and distribution seems to be influenced at a regional scale by adaptation to local climatic conditions and the mobile beekeeping that has become a large-scale practice during the last decades. Other previous anthropogenic influences (Greek, Roman and Arab colonizations) are thought to be of minor importance in present day populations. Resumen Un extenso estudio de los haplotipos mitocondriales en colonias de la abeja doméstica de la Péninsula Ibérica ha corroborado las hipótesis previas acerca de la existencia de una variación clinal conjunta de los linajes evolutivos africano (A) y europeo occidental (M). Se ha encontrado que la Peninsula Ibérica es la región europea con la mayor diversidad (12 haplotipos detectados pertenecientes al linaje M y 10 al linaje A). La frecuencia de los haplotipos africanos disminuye en la orientación SW-NE, al tiempo que aumenta proporcionalmente la de los M. Estos resultados se analizan en relación a las hipótesis recientes que ubican el origen de Apis mellifera en África, junto con otras que postulan una colonización temprana de esta especie en Europa occidental, seguida de una diferenciación durante el Pleistoceno. El patrón geográfico actual de haplotipos y frecuencias a escala regional, parece estar influido por la adaptación a las condiciones climáticas locales y la trashumancia, práctica que ha adquirido grandes proporciones en las últimas décadas. Otras influencias antrópicas acontecidas como las colonizaciones de griegos, romanos y árabes han tenido posiblemente poca influencia sobre las poblaciones ibéricas actuales. [source] Population genetics of Galápagos land iguana (genus Conolophus) remnant populationsMOLECULAR ECOLOGY, Issue 23 2008ATHANASIA C. TZIKA Abstract The Galápagos land iguanas (genus Conolophus) have faced significant anthropogenic disturbances since the 17th century, leading to severe reduction of some populations and the extinction of others. Conservation activities, including the repatriation of captive-bred animals to depleted areas, have been ongoing since the late 1970s, but genetic information has not been extensively incorporated. Here we use nine species-specific microsatellite loci of 703 land iguanas from the six islands where the species occur today to characterize the genetic diversity within, and the levels of genetic differentiation among, current populations as well as test previous hypotheses about accidental translocations associated with early conservation efforts. Our analyses indicate that (i) five populations of iguanas represent distinct conservation units (one of them being the recently discovered rosada form) and could warrant species status, (ii) some individuals from North Seymour previously assumed to be from the natural Baltra population appear related to both Isabela and Santa Cruz populations, and (iii) the five different management units exhibit considerably different levels of intrapopulation genetic diversity, with the Plaza Sur and Santa Fe populations particularly low. Although the initial captive breeding programmes, coupled with intensive efforts to eradicate introduced species, saved several land iguana populations from extinction, our molecular results provide objective data for improving continuing in situ species survival plans and population management for this spectacular and emblematic reptile. [source] Ice-wedge pseudomorphs and frost-cracking structures in Weichselian sediments, central-west PolandPERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2009Marek Ewertowski Abstract Wedge-shaped structures are described from three sites in the central Wielkopolska region (central-west Poland) in two main positions: (1) within fluvioglacial deposits below the Weichselian subglacial till and (2) within recessional deposits above this subglacial till. The wedges are interpreted as ice-wedge pseudomorphs (Rensko site), relict frost cracks (Tomice site) and thermokarst-affected ice-wedge pseudomorphs (Annowo-Kiszkowo area). The pseudomorphs suggest that thermal-contraction cracking occurred in the region in front of the advancing Weichselian ice sheet, as well as following its recession. Frost structures, which are interpreted as having degraded slowly, were much more affected by thermokarst processes (Annowo-Kiszkowo area) than those in the Rensko and Tomice sites which probably thawed rapidly, due to an insulating and warming effect of the overlying ice masses. The development of ice wedges was influenced by wet conditions in former depressions between ice-cored ridges or by large amounts of meltwater in the proglacial environment. These periglacial features support previous hypotheses that climatic conditions in the Wielkopolska region after the last ice-sheet recession changed gradually from glacial to periglacial. Copyright © 2009 John Wiley & Sons, Ltd. [source] A comparative geochemical study of bituminous boat remains from H3, As-Sabiyah (Kuwait), and RJ-2, Ra's al-Jinz (Oman)ARABIAN ARCHAEOLOGY AND EPIGRAPHY, Issue 1 2005Jacques Connan This paper presents a geochemical analysis of fragments of bituminous amalgam from H3, As-Sabiyah (Kuwait), and RJ-2, Ra's al-Jinz (Oman). The fragments bear barnacles on one side and reed impressions on the other, and are thought to have been part of the coating of reed-bundle boats. The material from H3 dates to between 5300,4900 BC, while that of RJ-2 dates to 2500,2100 BC. Samples from both sites were geochemically compared to archaeological and ethnographic material from Kosak Shamali (northern Syria, c.5000,4400 BC), RH-5 (Oman, 4400,3500 BC) and Baghdad (central Iraq, 1900 AD). The composition of the bituminous amalgams was studied in detail. Rock-Eval Pyrolysis gave a measure of Total Organic Carbon in the samples, and allowed an initial comparison of the data sets using various parameters. Examination of the proportions of soluble and insoluble organic matter allowed an assessment of the quantity of vegetal matter added to the bitumen to make the bituminous amalgam. The composition of the Ra's al-Jinz material was studied using X-Ray Diffraction analysis and thin-section petrography, in order to assess the proportions of various minerals in the bituminous amalgams. It was concluded that the recipe for the bituminous mixture used to coat reed-bundle and wooden boats did not differ significantly from that commonly used to make ,mortar' for architectural purposes in Mesopotamia. Traces of animal fats or fish oils were not found in the analysed Ra's al-Jinz material, in contrast to previous hypotheses regarding the composition of the mixture. Comparison of the gross composition of extractable organic matter (the constituents of pure bitumen, soluble in chloroform or dichloromethane) showed the progressive effects of weathering on the samples. The isotopic composition of the bituminous material from H3 and the other sites was then compared to that of bitumen seeps and crude oils from Mesopotamia, Iran and Oman. The most significant result is that the material from As-Sabiyah originated in Kuwait, at a surface seep at Burgan, while the material from Ra's al-Jinz had a source in northern Mesopotamia. [source] The new framework for understanding placental mammal evolutionBIOESSAYS, Issue 8 2009Robert J. Asher Abstract An unprecedented level of confidence has recently crystallized around a new hypothesis of how living placental mammals share a pattern of common descent. The major groups are afrotheres (e.g., aardvarks, elephants), xenarthrans (e.g., anteaters, sloths), laurasiatheres (e.g., horses, shrews), and euarchontoglires (e.g., humans, rodents). Compared with previous hypotheses this tree is remarkably stable; however, some uncertainty persists about the location of the placental root, and (for example) the position of bats within laurasiatheres, of sea cows and aardvarks within afrotheres, and of dermopterans within euarchontoglires. A variety of names for sub-clades within the new placental mammal tree have been proposed, not all of which follow conventions regarding priority and stability. More importantly, the new phylogenetic framework enables the formulation of new hypotheses and testing thereof, for example regarding the possible developmental dichotomy that seems to distinguish members of the newly identified southern and northern radiations of living placental mammals. [source] Adaptive significance of food income in European snakes: body size is related to prey energeticsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010MARCO A. L. ZUFFI Feeding strategies and diet patterns have been extensively investigated in vertebrates and, more specifically, in snakes. Although it has been hypothesized that prey species may differ in terms of energy content, almost no theoretical or practical study has been carried out to determine actual nutritional values of the common prey types of wild snakes. Our model taxa were a selection of widely distributed and well known European snake species, which have all been studied in depth: approximately 76% of their diet is composed of mammals, reptiles, and insects. We therefore selected a single model species for each of these categories and proceeded with the analyses. Nutritional values were determined using a standard procedure: lizards and mice were richer in proteins than insects (crickets); insects and mice were richer in lipids than lizards, and mice and crickets have a higher energy content than lizards; lizards were rich in ashes. We then applied our experimental results to a selected sample of European terrestrial snakes (11 populations, ten species, seven genera, two families) characterized by different body size (50,160 cm total length) and reproductive strategies (oviparous versus viviparous), aiming to correlate these parameters with patterns of energy income. A direct relationship was found between body mass/body length ratio (BCI, body condition index) and meal energetics: the higher the BCI, the higher was the metabolic requirement, whereas BCI was independent of species or of reproductive system effect. Large-sized snakes thus need a highly diversified and more energy-rich diet than smaller snakes, supporting previous hypotheses. The simple applicability of this method could be of valuable support in further comparative research work, reducing experimental costs and stimulating further ecological, behavioural, and, possibly, phylogenetic comparisons. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 307,317. [source] Ectoparasite load is linked to ontogeny and cell-mediated immunity in an avian host system with pronounced hatching asynchronyBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2008RADOVAN VÁCLAV Several contrasting hypotheses have been proposed to account for host age-biased parasite distribution, with some of them suggesting a key role of ectoparasites in the evolution and maintenance of weight hierarchies within broods. We examined parasite distribution among individual hosts across the whole period of host exposure to the parasite in a host system that shows distinct within-brood differences in age and age-related mortality. By contrast to previous hypotheses, we found that the abundance of a haematophagous, mobile ectoparasite Carnus haemapterus on nestling European rollers (Coracias garrulus) was highest approximately during the mid-nestling stage of their host, coinciding with the inflection point of the host growth phase. Parasite load increased neither with absolute resource availability (i.e. body size), nor body condition index. By contrast to previous evidence, higher parasite load under natural conditions was associated with a stronger cell-mediated immune response. However, this association was moderated by low parasite densities, as well as a better brood body condition index. Overall, although we revealed remarkable host ontogenetic effects on parasite distribution, the present study suggests that a highly mobile ectoparasite generally prefers healthier hosts. We propose that, in host systems with a marked asynchrony of hatching and background mortality within the brood, parasites favour persistence rather than nutritional attractiveness of the host. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 463,473. [source] Karyotype differentiation in Chromaphyosemion killifishes (Cyprinodontiformes, Nothobranchiidae): patterns, mechanisms, and evolutionary implicationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2008MARTIN VÖLKER Chromaphyosemion killifishes are a karyotypically highly diverse group of small, sexually dimorphic fishes living in rainforest rivulets in tropical West and Central Africa. In the present study, we used various chromosome banding and staining techniques to analyse the karyotypes of 13 populations representing seven described species (Chromaphyosemion loennbergii, Chromaphyosemion punctulatum, Chromaphyosemion splendopleure, Chromaphyosemion volcanum, Chromaphyosemion malumbresi, Chromaphyosemion melanogaster, Chromaphyosemion bitaeniatum) and two undescribed forms (Chromaphyosemion cf. lugens, Chromaphyosemion sp. Rio Muni GEMHS00/41). Diploid chromosome numbers (2 n) and the number of chromosome arms (NF) ranged from 2 n = 24 in C. malumbresi to 2 n = 40 in C. bitaeniatum and from NF = 40 in C. volcanum and C. cf. lugens to NF = 54 in one population of C. loennbergii. A tentative XX/XY sex chromosome system was revealed in C. loennbergii, C. melanogaster, C. malumbresi, and Chromaphyosemion sp. Rio Muni GEMHS00/41. Mapping cytogenetic data for all described Chromaphyosemion species onto a recently published mitochondrial DNA phylogeny revealed a complex pattern of chromosomal evolution with several independent reductions of 2 n and independent modifications of NF and nucleolus organizer region phenotypes. Together with the results of preliminary crossing and mate choice experiments, the cytogenetic and molecular phylogenetic data suggest that, contrary to previous hypotheses, chromosomal rearrangements are probably not the most important and certainly not the only factor driving speciation in Chromaphyosemion killifishes. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 143,153. [source] Simultaneous analysis of basal Hymenoptera (Insecta): introducing robust-choice sensitivity analysisBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2003SUSANNE SCHULMEISTER Molecular characters are analysed on their own and in combination with morphological data to examine the phylogenetic relationships of the basal lineages of Hymenoptera (,Symphyta'). This study covers 47 sawfly genera and nine apocritan families and includes molecular sequences from five genes , 12S, 16S, 18S and 28S ribosomal genes and cytochrome oxidase 1 , as well as 343 morphological characters. A robust-choice sensitivity analysis is performed with the data. First, the simultaneous analysis is repeated three times, each time employing a different step matrix for weighting the transformations of the molecular characters. Then, the results of all three simultaneous analyses are summarized in a strict consensus in order to avoid basing the conclusions on a narrow set of assumptions. This methodology is discussed in the paper. The relationships among superfamilies largely confirm previous hypotheses, being (Xyeloidea (Tenthredinoidea s.l. (Pamphilioidea (Cephoidea (Siricoidea (Xiphydrioidea (Orussoidea Apocrita))))))), where Siricoidea is understood as Siricidae+Anaxyelidae. However, the relationships within Tenthredinoidea s.s. proposed here are novel: ({Argidae Pergidae}[Athalia{(Diprionidae Cimbicidae) Tenthredinidae minus Athalia}]). © 2003 The Linnean Society of London. Biological Journal of the Linnean Society, 2003, 79, 245,275. [source] Clinical characteristics and outcomes for a modern series of primary gliosarcoma patientsCANCER, Issue 5 2010Seunggu J. Han BS Abstract BACKGROUND: Primary gliosarcoma (PGS) is a rare central nervous system tumor with limited experience reported in the literature. In the current study, the authors present a modern series of confirmed PGS cases treated in the era of magnetic resonance imaging (MRI), after the accepted glioblastoma management of resection, radiation, and temozolomide. METHODS: Using a retrospective review, patients with confirmed PGS were identified (1996-2008). Cases were determined to be PGS by central pathology review using the 2007 World Health Organization criteria. Extensive chart review was performed to gather clinical and pathologic data on these cases. RESULTS: All but 1 patient had undergone a preoperative MRI, with 1 patient receiving a computed tomography scan due to a cardiac pacemaker. A total of 10 patients received radiotherapy with concurrent and adjuvant temozolomide chemotherapy, and 8 patients received radiotherapy alone or in combination with other chemotherapeutic agents. In 2 patients, the history of adjuvant treatment could not be confirmed. The overall median survival was 13.9 months (range, 2.2-22.9 months). Patients with gliosarcomas resembling meningioma were found to have a significantly prolonged median survival compared with patients harboring gliosarcoma resembling glioblastoma multiforme (16 months vs 9.6 months; P = .011). However, no difference in survival was noted between patients who received concurrent radiotherapy and temozolomide compared with those who did not (10.4 months vs 13.9 months; P = .946). CONCLUSIONS: The results of the current study support previous hypotheses that there are 2 distinct types of PGS. The type mimicking the appearance of a meningioma appears to carry a significantly more favorable prognosis, most likely due to an increased chance at achieving macroscopic total resection. Cancer 2010. © 2010 American Cancer Society. [source] The phylogeny of the Histeroidea (Coleoptera: Staphyliniformia)CLADISTICS, Issue 4 2002Michael S. Caterino For its size (ca. 4000 species) the Histeridae is one of the most ecologically and morphologically diverse families of beetles. Its mostly predaceous members occupy a wide variety of habitats for which their morphologies may be highly modified. Previous attempts to resolve the phylogeny of the family based on morphological data have left many difficult issues unresolved. This study is the first to utilize either larval or molecular (18S rDNA) data in combination with adult morphology in an attempt to resolve these issues. We compare the performance of optimization alignment with a fixed positional homology approach, over a range of parameter space. Optimizing alignment parameters for combined analyses of 18S and morphology for both approaches resulted in very similar topologies. Contrary to previous hypotheses which held the cylindrical, subcortical forms of the family (e.g., Niponius, Trypanaeus, Trypeticus) to be the most primitive, our analyses find these to be highly specialized forms derived from within other more generalized taxa. Basal lineages within the family instead include Onthophilus, Anapleus, and Dendrophilus, all of which are ovoid, mainly generalist forms. [source] Phylogeny and Systematic Position of Opiliones: A Combined Analysis of Chelicerate Relationships Using Morphological and Molecular Data,CLADISTICS, Issue 1 2002Gonzalo Giribet The ordinal level phylogeny of the Arachnida and the suprafamilial level phylogeny of the Opiliones were studied on the basis of a combined analysis of 253 morphological characters, the complete sequence of the 18S rRNA gene, and the D3 region of the 28S rRNA gene. Molecular data were collected for 63 terminal taxa. Morphological data were collected for 35 exemplar taxa of Opiliones, but groundplans were applied to some of the remaining chelicerate groups. Six extinct terminals, including Paleozoic scorpions, are scored for morphological characters. The data were analyzed using strict parsimony for the morphological data matrix and via direct optimization for the molecular and combined data matrices. A sensitivity analysis of 15 parameter sets was undertaken, and character congruence was used as the optimality criterion to choose among competing hypotheses. The results obtained are unstable for the high-level chelicerate relationships (except for Tetrapulmonata, Pedipalpi, and Camarostomata), and the sister group of the Opiliones is not clearly established, although the monophyly of Dromopoda is supported under many parameter sets. However, the internal phylogeny of the Opiliones is robust to parameter choice and allows the discarding of previous hypotheses of opilionid phylogeny such as the "Cyphopalpatores" or "Palpatores." The topology obtained is congruent with the previous hypothesis of "Palpatores" paraphyly as follows: (Cyphophthalmi (Eupnoi (Dyspnoi + Laniatores))). Resolution within the Eupnoi, Dyspnoi, and Laniatores (the latter two united as Dyspnolaniatores nov.) is also stable to the superfamily level, permitting a new classification system for the Opiliones. [source] Aberrant trajectory of thalamocortical axons associated with abnormal localization of neurocan immunoreactivity in the cerebral neocortex of reeler mutant miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005Hong-Peng Li Abstract We examined the molecular mechanisms underlying the formation of the thalamocortical pathway in the cerebral neocortex of normal and reeler mutant mice. During normal development of the mouse neocortex, thalamic axons immunoreactive for the neural cell adhesion molecule L1 rarely invaded the cortical plate and ran centered in the subplate which is immunoreactive for neurocan, a brain-specific chondroitin sulfate proteoglycan. On the other hand, in homozygous reeler mutant mice, thalamic axons took an aberrant course to run obliquely through the cortical plate. Injection of bromodeoxyuridine at embryonic day 11 specifically labeled subplate neurons in normal mice, whilst in the reeler neocortex it labeled cells scattered in the cortical plate as well as in the superficial layer (superplate). Neurocan immunoreactivity was associated with the bromodeoxyuridine-positive cells in the superplate, as well as being present in oblique bands within the cortical plate, along which L1-bearing thalamic axons preferentially ran. The present results support our previous hypothesis proposed for normal rats that a heterophilic molecular interaction between L1 and neurocan is involved in determining the thalamocortical pathway within the neocortical anlage [T. Fukuda et al. (1997)Journal of Comparative Neurology, 382, 141,152]. [source] Diisobutylaluminium Hydride (DIBAL-H) Promoted Secondary Rim Regioselective Demethylations of Permethylated ,-Cyclodextrin: A Mechanistic ProposalEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2010Sulong Xiao Abstract Diisobutylaluminium hydride (DIBAL-H) promotes secondary rim regioselective bis-de- O -methylation at the 2A - and 3B -positions of permethylated ,-cyclodextrin. This result contrasts with the selective bis-de- O -benzylation of perbenzylated cyclodextrins in which regioselective deprotection occurs at the primary rim. To gain an insight into the mechanism of this remarkable contrasting behavior, the two corresponding permethylated cyclodextrins with an alcohol function at either the 2- or 3-position were synthesized. The cyclodextrin with the alcohol at the 3-position reacts withDIBAL-H to afford the 2A,3B -diol whereas the cyclodextrin with the alcohol at the 2-position is unreactive. This observation allows us to propose a mechanism for the demethylation reaction that involves for each demethylation step two molecules of aluminium reagent, in accord with the previous hypothesis on the debenzylation reaction. The second demethylation step appears to be faster than the first, the coordination of aluminium now being an intramolecular process. [source] Comparative mtDNA sequence (control region, ATPase 6 and NADH-1) divergence in Hucho taimen(Pallas) across four Siberian river basinsJOURNAL OF FISH BIOLOGY, Issue 4 2005E. Froufe Hucho taimen from eight populations spanning four drainage basins (Amur, Lena, Enisei and Khatanga) were analysed for nucleotide sequence variation across three mitochondrial genes (ATP6, NADH-1 and control region). Samples of H. hucho, Brachymystax lenok(sharp-snouted and blunt-snouted forms) and Parahucho perryi were also included for comparison. Nucleotide variation across a total of 1826 base pairs in H. taimen revealed shared haplotypes between the Amur and Lena basins, further supporting a previous hypothesis of late to post-Pleistocene hydrological exchange between these now disjunct basins. In contrast to an earlier study using the control region alone, clear phylogeographic structure was seen at a large geographic scale, reflected by two phylogroups, one corresponding to the Amur and Lena basins, and the other to the Enisei and Khatanga basins. Comparative rates of divergence revealed considerably faster and less heterogeneous substitution rates for the two coding genes, especially at interspecific levels compared to the mtDNA control region. [source] Ontogeny and homology of the claustra in Otophysan Ostariophysi (Teleostei)JOURNAL OF MORPHOLOGY, Issue 8 2006Ralf Britz Abstract We studied the ontogeny of the claustrum comparatively in representatives of all otophysan subgroups. The claustrum of cypriniforms has a cartilaginous precursor, the claustral cartilage, which subsequently ossifies perichondrally at its anterior face and develops an extensive lamina of membrane bone. The membrane bone component of the claustrum and its close association with the atrium sinus imparis, a perilymphatic space of the Weberian apparatus, are both synapomorphies of cypriniforms. The characiform claustrum is not preformed in cartilage and originates as a membrane bone ossification, a putative synapomorphy of that taxon. Among siluriforms, the claustrum is present only in more basal groups and originates as an elongate cartilage that ossifies in a characteristic ventrodorsal direction, possibly a synapomorphy of catfishes. Gymnotiforms lack the claustral cartilage and claustrum. We review all previous hypothesis of claustrum homology in light of the above findings and conclude that the most plausible hypothesis is the one originally proposed by Bloch ([1900] Jen Z Naturw 34:1,64) that claustra are homologs of the supradorsals of the first vertebra. J. Morphol. © 2006 Wiley-Liss, Inc. [source] Time-series nasal epithelial transcriptomics during natural pollen exposure in healthy subjects and allergic patientsALLERGY, Issue 2 2010P. Mattila To cite this article: Mattila P, Renkonen J, Toppila-Salmi S, Parviainen V, Joenväärä S, Alff-Tuomala S, Nicorici D, Renkonen R. Time-series nasal epithelial transcriptomics during natural pollen exposure in healthy subjects and allergic patients. Allergy 2010; 65: 175,183. Abstract Background:, The role of epithelium has recently awakened interest in the studies of type I hypersensitivity. Objective:, We analysed the nasal transcriptomics epithelial response to natural birch pollen exposure in a time series manner. Methods:, Human nasal epithelial cell swabs were collected from birch pollen allergic patients and healthy controls in winter season. In addition, four specimens at weekly intervals were collected from the same subjects during natural birch pollen exposure in spring and transcriptomic analyses were performed. Results:, The nasal epithelium of healthy subjects responded vigorously to allergen exposure. The immune response was a dominating category of this response. Notably, the healthy subjects did not display any clinical symptoms regardless of this response detected by transcriptomic analysis. Concomitantly, the epithelium of allergic subjects responded also, but with a different set of responders. In allergic patients the regulation of dyneins, the molecular motors of intracellular transport dominated. This further supports our previous hypothesis that the birch pollen exposure results in an active uptake of allergen into the epithelium only in allergic subjects but not in healthy controls. Conclusion:, We showed that birch pollen allergen causes a defence response in healthy subjects, but not in allergic subjects. Instead, allergic patients actively transport pollen allergen through the epithelium to tissue mast cells. Our study showed that new hypotheses can arise from the application of discovery driven methodologies. To understand complex multifactorial diseases, such as type I hypersensitivity, this kind of hypotheses might be worth further analyses. [source] | ||||||||||||||||||||||||||||||||||||||||