Effects of diagenesis on the astrochronological approach of defining stratigraphic boundaries in calcareous rhythmites: The Tortonian GSSP

Since the establishment of astrochronology, calcareous rhythmites are frequently used as the basis of high‐resolution chronostratigraphy. In particular for the Neogene, calcareous rhythmites serve as stratotypes and for absolute dating of stratigraphic boundaries (Global Stratotype Sections and Points – GSSPs). However, the exact mechanisms responsible for the formation of the rhythmic intercalation of lithologies in such successions are complex and not easily reconstructed. To a large extent this is the effect of diagenetic modifications of the original sediment. Here, two examples of Neogene calcareous rhythmites are studied; the Monte dei Corvi section and the Monte Gibliscemi section. The first is the GSSP location of the Serravallian–Tortonian boundary, whereas the second is an auxiliary stratotype for the same boundary. During the past years, astrochronological approaches were applied to these successions to considerably increase time resolution compared to the elaborated biostratigraphic database. The present study focuses on micropetrographic, trace element and clay mineralogical methods in order to gain a better understanding of the genesis of the rhythmites. In the Monte Gibliscemi section, sediment parameters that are robust against diagenetic change clearly reflect primary differences, i.e. cyclical environmental changes. In contrast, no clear primary signal is determined for the Monte dei Corvi section on a couplet scale, leaving the origin of the rhythm ambiguous. This impedes the interpretation of the latter and the comparability between the two successions, and also compromises any bed‐by‐bed correlation between the two. The unclear origin of the rhythmites of Monte dei Corvi introduces uncertainty into the applicability of astrochronology to this succession.     

Molecular phylogenetic evidence for paraphyly of the genus Sooglossus, with the description of a new genus of Seychellean frogs

The Seychelles harbour an endemic frog family, the Sooglossidae, currently containing two genera: Sooglossus , with three species, and Nesomantis , with one species. These unique frogs are generally considered to be basal neobatrachians, although their relationships to other neobatrachian taxa, except the Nasikabatrachidae, remain unresolved. Our molecular phylogeny based on a dataset consisting of fragments of the nuclear rag-1 and rag-2 genes, as well as mitochondrial 16S rRNA in representatives of the major neobatrachian lineages, confirmed the previously postulated Sooglossidae + Nasikabatrachidae clade and the placement of the South American Caudiverbera with the Australian Myobatrachidae, but did not further resolve the position of sooglossids. Our results do, however, unambiguously show sooglossids to be monophyletic but the genus Sooglossus to be paraphyletic, with the type species Sooglossus sechellensis being more closely related to Nesomantis thomasseti than to Sooglossus gardineri and Sooglossus pipilodryas , in agreement with morphological, karyological, and bioacoustic data. As a taxonomic consequence, we propose to consider the genus name Nesomantis as junior synonym of Sooglossus , and to transfer the species thomasseti to Sooglossus . For the clade composed of the species gardineri and pipilodryas , here, we propose the new generic name Leptosooglossus . A significant genetic differentiation of 3% was found between specimens of Sooglossus thomasseti from the Mahé and Silhouette Islands, highlighting the need for further studies on their possible taxonomic distinctness.   © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 347–359.     

Colonization and speciation on volcanic islands: phylogeography of the flightless grasshopper genus Arminda (Orthoptera,Acrididae) on the Canary Islands

Abstract Volcanic archipelagos represent excellent areas to study colonization and speciation processes. The grasshopper genus Arminda is one of many endemic taxa of the Canary Islands. It consists of seven wingless species, most of which are single‐island endemics. We sequenced two mitochondrial (12s rRNA, ND5) and two nuclear gene fragments (28s rRNA, ITS2) to reconstruct the colonization pattern of the genus. Our results are in accordance with a stepping‐stone colonization model from east to west, corresponding to the prevailing ocean currents, but alternative hypotheses cannot be fully rejected. The populations of A. brunneri from Tenerife belong to two different lineages (east and west) consistent with the geological history of the island. It remains to be tested whether these lineages represent different species and whether further lineages exist on this island. The five clades of the four western islands (A. brunneri group) have approximately similar branch lengths. The short internodes between these lineages resulted in a poorer phylogenetic resolution. Specimens from La Palma were genetically distinct and are subsequently described as a new species, Arminda palmae sp.n. Our results suggest in situ speciation on Gran Canaria, which was accompanied by a stronger degree of morphological diversification than the inter‐island speciation processes. The aberrant species A. canariensis has formerly been assigned to a monotypic subgenus Chopardminda, which is now synonymized with Arminda syn.n. based on its phylogenetic position. Gran Canaria seems to be the only island where Arminda species occur sympatrically, although allopatric speciation seems likely due to the long history of volcanism and erosion on the island.     

A phenetic analysis and revision of Guineo-Congolean rain forest taxa of Chlorophytum (Anthericaceae)

The taxonomy of rain forest species of the genus Chlorophytum in central and west Africa has to date been difficult to resolve. Plants collected in the Guineo-Congolean plant geographical region deposited in several herbaria formed the basis for a morphometric analysis using Principal Component Analyses and including 16 characters. In total, 166 individuals were included from 461 herbarium collections, from which 57 seeds were scanned to investigate the surface structures. Eight species are recognized, including one with three subspecies and another with three varieties. Four new combinations are proposed ( Chlorophytum comosum (Thunb.) Jacques var. bipindense (Engl. & K. Krause) A.D. Poulsen & Nordal, C. comosum (Thunb.) Jacques var. sparsiflorum (Baker) A.D. Poulsen & Nordal, C. lancifolium Baker ssp. cordatum (Engl.) A.D. Poulsen & Nordal, and C. lancifolium Baker ssp. togoense (Engl.) A.D. Poulsen & Nordal), ten new synonyms are introduced and three lectotypes are designated.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 1–20.     

Molecular systematics of mantelline frogs from Madagascar and the evolution of their femoral glands

Several genera of frogs from Madagascar, classified in the family Mantellidae, subfamily Mantellinae, possess structures commonly called 'femoral glands' on the ventral side of their shanks. The question arises as to the origin and phylogenetic significance of these glands. A molecular phylogeny based on 3601 nucleotide DNA sequences of three mitochondrial and two nuclear genes of 30 mantellid species provided strong support for monophyly of the included mantellines, all characterized by enlarged femoral gland clusters, as well as for those with gland clusters of coordinated central arrangement of secretion ducts. However, the phylogeny also strongly supported the hypothesis of convergent evolution of structurally similar glands in unrelated frogs ( Indirana , Petropedetes ), and several trends of convergent evolution of gland structure within mantellines. We studied the light microscopic structure of the femoral glands in a representative array of 18 mantellid species. Males of all species of the subfamily Mantellinae were characterized by clusters of distinct single glands. Each was structurally similar to an enlarged granular gland and secreted independently, probably through a single duct. By contrast, the largely semi-aquatic frogs in the genus Mantidactylus had a specialized cluster of glands, in which the secretion ducts led into a macroscopically recognizable central depression. In Boophis opisthodon , a mantellid species of the subfamily Boophinae without externally recognizable femoral glands, we observed a large number of enlarged granular glands of various sizes in the ventral skin of the shank. This observation is consistent with the hypothesis that the large and more uniform organs of mantellines are derived granular glands.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 529–539.     

A DISCUSSION AND PROPOSAL CONCERNING THE USE OF THE TERM CALCISPHERES

Abstract:  The terminology and grouping of spherical, calcareous microfossils of unknown biological affinity, usually referred to as calcispheres, are diffuse. The term calcispheres is inconsistently used, the morphological and taxonomical concepts are mostly ill-defined and a formal definition is lacking. To resolve this issue, we propose, in analogy with the erection of the Acritarcha for organic microfossils of unknown origin, a new group called Calcitarcha, including all calcareous microfossils with a central cavity for which the biological affinities remain unknown.     

Higher and lower‐level relationships of the deep‐sea fish order Alepocephaliformes (Teleostei: Otocephala) inferred from whole mitogenome sequences

Fishes of the order Alepocephaliformes, slickheads and tubeshoulders, constitute a group of deep‐sea fishes poorly known in respect to most areas of their biology and systematics. Morphological studies have found alepocephaliform fishes to display a mosaic of synapomorphic and symplesiomorphic characters, resulting in great difficulties when attempting to resolve intra‐ and interrelationships. Molecular data recently added to the confusion by removing Alepocephaliformes from the Euteleostei and placed them as incertae sedis within the Otocephala. In the present study we attempt to further clarify relationships of Alepocephaliformes by adding newly determined whole mitogenome sequences from 19 alepocephaliforms in order to address 1) phylogenetic position of Alepocephaliformes within the Otocephala; and 2) intrarelationships of Alepocephaliformes. The present study includes 96 taxa of which 30 are alepocephaliforms and unambiguously aligned sequences were subjected to partitioned maximum likelihood and Bayesian analyses. Results from the present study support Alepocephaliformes as a genetically distinct otocephalan order as sister clade to Ostariophysi (mostly freshwater fishes comprising Gonorynchiformes, Cypriniformes, Characiformes, Siluriformes and Gymnotiformes). The disputed family Bathylaconidae was found to be an artificial assemblage of the two genera Bathylaco and Herwigia, with the former as the sister group of the family Alepocephalidae and the latter nested within Alepocephalidae. Platytroctidae was found to be monophyletic as sister clade to the rest of Alepocephaliformes. Previously unrecognized clades within the family Alepocephalidae are presented and a clade comprising Alepocephalus, Conocara and Leptoderma was recovered as the most derived. As long as the current classification is being followed, the genera Alepocephalus, Bathytroctes, Conocara and Narcetes were all found non‐monophyletic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 923–936.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.     

Temporal dynamics of soil organic carbon after land‐use change in the temperate zone – carbon response functions as a model approach

Land‐use change (LUC) is a major driving factor for the balance of soil organic carbon (SOC) stocks and the global carbon cycle. The temporal dynamic of SOC after LUC is especially important in temperate systems with a long reaction time. On the basis of 95 compiled studies covering 322 sites in the temperate zone, carbon response functions (CRFs) were derived to model the temporal dynamic of SOC after five different LUC types (mean soil depth of 30±6 cm). Grassland establishment caused a long lasting carbon sink with a relative stock change of 128±23% and afforestation on former cropland a sink of 116±54%, 100 years after LUC (mean±95% confidence interval). No new equilibrium was reached within 120 years. In contrast, there was no SOC sink following afforestation of grasslands and 75% of all observations showed SOC losses, even after 100 years. Only in the forest floor, there was carbon accumulation of 0.38±0.04 Mg ha^?1 yr^?1 in afforestations adding up to 38±4 Mg ha^?1 labile carbon after 100 years. Carbon loss after deforestation (?32±20%) and grassland conversion to cropland (?36±5%), was rapid with a new SOC equilibrium being reached after 23 and 17 years, respectively. The change rate of SOC increased with temperature and precipitation but decreased with soil depth and clay content. Subsoil SOC changes followed the trend of the topsoil SOC changes but were smaller (25±5% of the total SOC changes) and with a high uncertainty due to a limited number of datasets. As a simple and robust model approach, the developed CRFs provide an easily applicable tool to estimate SOC stock changes after LUC to improve greenhouse gas reporting in the framework of UNFCCC.