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Selected Abstracts

Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2009
R. J. BUTLER
Abstract Palaeobiologists frequently attempt to identify examples of co-evolutionary interactions over extended geological timescales. These hypotheses are often intuitively appealing, as co-evolution is so prevalent in extant ecosystems, and are easy to formulate; however, they are much more difficult to test than their modern analogues. Among the more intriguing deep time co-evolutionary scenarios are those that relate changes in Cretaceous dinosaur faunas to the primary radiation of flowering plants. Demonstration of temporal congruence between the diversifications of co-evolving groups is necessary to establish whether co-evolution could have occurred in such cases, but is insufficient to prove whether it actually did take place. Diversity patterns do, however, provide a means for falsifying such hypotheses. We have compiled a new database of Cretaceous dinosaur and plant distributions from information in the primary literature. This is used as the basis for plotting taxonomic diversity and occurrence curves for herbivorous dinosaurs (Sauropodomorpha, Stegosauria, Ankylosauria, Ornithopoda, Ceratopsia, Pachycephalosauria and herbivorous theropods) and major groups of plants (angiosperms, Bennettitales, cycads, cycadophytes, conifers, Filicales and Ginkgoales) that co-occur in dinosaur-bearing formations. Pairwise statistical comparisons were made between various floral and faunal groups to test for any significant similarities in the shapes of their diversity curves through time. We show that, with one possible exception, diversity patterns for major groups of herbivorous dinosaurs are not positively correlated with angiosperm diversity. In other words, at the level of major clades, there is no support for any diffuse co-evolutionary relationship between herbivorous dinosaurs and flowering plants. The diversification of Late Cretaceous pachycephalosaurs (excluding the problematic taxon Stenopelix) shows a positive correlation, but this might be spuriously related to poor sampling in the Turonian,Santonian interval. Stegosauria shows a significant negative correlation with flowering plants and a significant positive correlation with the nonflowering cycadophytes (cycads, Bennettitales). This interesting pattern is worthy of further investigation, and it reflects the decline of both stegosaurs and cycadophytes during the Early Cretaceous. [source]

Molecular phylogeny of Enchytraeidae (Oligochaeta) indicates separate invasions of the terrestrial environment

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2010
Bent Christensen
Abstract Enchytraeidae is a family of soil inhabiting small- to medium-sized oligochaete worms using degradable plant material as a food source and primarily adapted to terrestrial or semi-terrestrial environments. The molecular phylogeny based upon both mitochondrial and nuclear genes indicates early segregations of the two genera Enchytraeus and Lumbricillus leaving the remaining genera included in this study as a later segregated major monophyletic branch. Extant members of the two former genera dominate in decaying seaweed in the littoral zone along the sea although members of in particular the genus Enchytraeus have also invaded other habitats. Historically the littoral zone of the sea is undoubtedly the first terrestrial or semi-terrestrial habitat where dead plant material accumulates to any greater extent and Enchytraeus and Lumbricillus may represent early successful attempts to exploit this resource. Inland soils probably had to await the emergence of land plants in order to provide a similar food resource and here the major branch of enchytraeid genera diversified into a high number of species in the numerous decomposer networks of this varied environment. A subdivision into the genera Enchytraeus and Lumbricillus on the one hand and a branch of mainly inland genera on the other is supported by differences in two somewhat neglected morphological features. Firstly, in Enchytraeus and Lumbricillus the testes are enclosed in a testis sac within which the male cells mature, by one possible exception a unique feature among Oligochaeta, The other enchytraeid genera studied and Oligochaeta in general lack this sac and the male cells mature directly in the cavity of the testicular segment. Secondly, species of Enchytraeus and Lumbricillus generally have a higher reproductive output than species of the inland terrestrial branch and this may represent an adaptation to the unpredictable littoral zone compared to the more stable nature of inland habitats. In the older literature the genus Mesenchytraeus is considered to have a basic position within the entire family but our molecular data do not support this expectation. In Enchytraeidae the nephridia are elaborate organs of a characteristic and constant shape covering species from different genera in a pattern following the molecular phylogeny. Other much used morphological features such as shape of setae, anteclitellar origin of the dorsal vessel and various modifications of the intestine have arisen more than once. Zusammenfassung Enchytraeidae sind eine Familie kleiner bis mittelgroßer edaphischer Oligochaeten, welche abbaubares Pflanzenmaterial als Nahrungsquelle nutzen und primär an terrestrische oder semiterrestrische Lebensräume angepaßt sind. Die hier vorgestellte, auf mitochondrialen und nukleären Genen beruhende molekulare Phylogenie indiziert eine frühe Abtrennung der beiden Gattungen Enchytraeus und Lumbricillus und beläßt die übrigen der in dieser Studie untersuchten Gattungen als eine später abgezweigte monophyletische Großgruppe. Rezente Glieder der beiden erwähnten Gattungen dominieren in verrottendem Strandanwurf des Meereslitorals, obwohl Arten insbesondere der Gattung Enchytraeus auch andere Lebensräume erobert haben. Historisch gesehen ist das Meereslitoral zweifelsohne das erste terrestrische oder semiterrestrische Habitat, in dem totes Pflanzenmaterial in größerem Ausmaß akkumulierte, und Enchytraeus und Lumbricillus könnten frühe erfolgreiche Versuche der Nutzung dieser Ressource darstellen. Festlandsböden dagegen bedurften wahrscheinlich der Entwicklung von Landpflanzen, um eine vergleichbare Nahrungsquelle zur Verfügung zu stellen, und hier diversifizierte sich der Hauptzweig der Enchytraeidengattungen in viele Arten in den diversen Zersetzernetzen dieses vielgestaltigen Lebensraums. Eine Unterteilung in die Gattungen Enchytraeus und Lumbricillus auf der einen Seite und einen Zweig mit vorwiegend terrestrischen Gattungen auf der anderen wird durch zwei bislang eher vernachlässigte morphologische Merkmale gestützt. Erstens, bei Enchytraeus und Lumbricillus wird der Hoden von einem Testis-Sack, in dem die männlichen Zellen reifen, umschlossen. Dies ist mit einer möglichen Ausnahme einzigartig bei Oligochaeten. Bei den übrigen untersuchten Enchytraeidengattungen und bei Oligochaeten generell fehlt dieser Sack, und die männlichen Zellen reifen unmittelbar in der Körperhöhle des Hodensegmentes. Zweitens, die Reproduktionsrate von Enchytraeus und Lumbricillus ist generell höher als die der Arten des Festlandszweigs. Dies könnte eine Anpassung an die im Vergleich zu Festlandsböden instabileren Bedingungen des Meereslitorals bedeuten. In der älteren Literatur wird der Gattung Mesenchytraeus eine basale Position innerhalb der gesamten Familie zugewiesen, aber unsere molekularen Daten stützen diese Annahme nicht. Die Nephridien der Enchytraeiden sind komplexe Organe mit einer charakteristischen und artübergreifend konstanten Form, deren gattungsmäßige Abwandlungen der molekularen Phylogenie entsprechen. Andere oft verwendete morphologische Merkmale wie Borstenform, anteclitellarer Ursprung des Dorsalgefäßes und verschiedene Darmmodifikationen sind mehr als einmal entstanden. [source]

Spatial repartition and genetic relationship of green and albino individuals in mixed populations of Cephalanthera orchids

PLANT BIOLOGY, Issue 4 2010
V. Tranchida-Lombardo
Abstract Several green orchids of the Neottieae tribe acquire organic carbon both from their mycorrhizal fungi and from photosynthesis. This strategy may represent an intermediate evolutionary step towards mycoheterotrophy of some non-photosynthetic (albino) orchids. Mixed populations of green and albino individuals possibly represent a transient evolutionary stage offering opportunities to understand the evolution of mycoheterotrophy. In order to understand the emergence of albinos, we investigated patterns of spatial and genetic relationships among green and albino individuals in three mixed populations of Cephalanthera damasonium and one of C. longifolia using spatial repartition and Amplified fragment length polymorphism (AFLP) markers. Two of these populations were monitored over two consecutive flowering seasons. In spatial repartition analyses, albino individuals did not aggregate more than green individuals. Genetic analyses revealed that, in all sampled populations, albino individuals did not represent a unique lineage, and that albinos were often closer related to green individuals than to other albinos from the same population. Genetic and spatial comparison of genets from the 2-year monitoring revealed that: (i) albinos had lower survival than green individuals; (ii) accordingly, albinos detected in the first year did not correspond to the those sampled in the second year; and (iii) with one possible exception, all examined albinos did not belong to any green genet from the same and/or from the previous year, and vice versa. Our results support a scenario of repeated insurgence of the albino phenotypes within the populations, but unsuccessful transition between the two contrasting phenotypes. Future studies should try to unravel the genetic and ecological basis of the two phenotypes. [source]

William Hunter's Gravid Uterus: The specimens and plates

CLINICAL ANATOMY, Issue 4 2002
N.A. McCulloch
Abstract William Hunter's collection of anatomical specimens of the pregnant uterus forms one of the finest displays in the Anatomy Museum at the University of Glasgow. We were interested to know which specimens in the Museum matched the plates in Hunter's The Anatomy of the Human Gravid Uterus Exhibited in Figures (1774). In our investigation we were greatly assisted by Teacher's Catalogue of the Anatomical and Pathological Preparations of Dr William Hunter (1900). Thirteen specimens in the Museum and one from the pathological collection at the Royal Infirmary are represented in Hunter's book. The specimens can be recognized in 25 of its illustrations. A further three specimens may correspond to figures but we could not prove this. With one possible exception, all the specimens matching plates noted in Teacher's catalogue remain in the Museum and one believed missing in Marshall's (1970) revision of the catalogue has been found. Clin. Anat. 15:253,262, 2002. © 2002 Wiley-Liss, Inc. [source]