Stability of networks of delay-coupled delay oscillators

Dynamical networks with time delays can pose a considerable challenge for mathematical analysis. Here, we extend the approach of generalized modeling to investigate the stability of large networks of delay-coupled delay oscillators. When the local dynamical stability of the network is plotted as a function of the two delays then a pattern of tongues is revealed. Exploiting a link between structure and dynamics, we identify conditions under which perturbations of the topology have a strong impact on the stability. If these critical regions are avoided the local stability of large random networks can be well approximated analytically

Pygmy moths (Lepidoptera, Nepticulidae) from Baltic Amber (Eocene)

Pygmy moths (Nepticulidae, Lepidoptera) from Eocene Baltic amber are described with five new specimens, representing the only specimens beyond one described before. Some of the findings differ from Stigmellites baltica Kozlov in species and sex. They are formally described as new species Bohemannia butzmanni and B. aschaueri. Phylogenetic and paleoecological aspects of Nepticulidae from Baltic amber are discussed.Fünf neue Arten von Zwergminiermotten (Nepticulidae, Lepidoptera) werden aus Baltischem Bernstein (Eozän) beschrieben; zusammen mit einer bereits früher beschriebenen Form (Stigmellites baltica Kozlov) stellen sie die einzig bekannten Fossilien dieser Tiergruppe dar. Da einige der hier beschriebenen Fossilien sich von S. baltica deutlich unterscheiden, werden sie als neue Arten, Bohemannia butzmanni und B. aschaueri, beschrieben. Phylogenetische und paläoökologische Aspekte der Nepticulidae im Baltischen Bernstein werden diskutiert

Bucculatrix rycki – the first fossil adult Ribbed Cocoon Maker Moth (Bucculatricidae, Lepidoptera)

An adult of a Ribbed Cocoon Maker Moth (Bucculatricidae) from Eocene Baltic amber is described as a new species (Bucculatrix rycki). This is the first description of a fossil adult of this microlepidopteran family, but previous evidence for this family comes from typical leaf mines in fossil leaves that provide evidence dating to the Upper Cretaceous. The minimal geological age for this adult specimen is here confirmed to be at least upper Eoceneand likely middle Eocene based on stratigraphic evidence. A putative host-plant range of the fossil taxon is proposed, based on host-plant records of extant species of the genus in association with paleobotanical data from Baltic amber.Ein fossiler Zwergwickler (Bucculatricidae) wird als neue Art Bucculatrix rycki aus dem Eozän des Baltischen Bernsteins beschrieben. Es scheint die erste Beschreibung eines fossilen Adulten dieser Familie von Mikrolepidopteren zu sein, aber es gibt Nachweise dieser Familie durch ihre typischen Minen in fossilen Blättern, die bis in die obere Kreide zurückreichen. Das minimale geologische Alter durch direkten Nachweis eines Imagos wird also mindestens für das obere Eozän und, nach stratigraphischen Daten, wahrscheinlich auch für das mittlere Eozän bestätigt. Ein mögliches Wirtspflanzenspektrum des fossilen Taxons wird diskutiert, basierend auf Wirtspflanzenspektren rezenter Arten im Vergleich zu paläobotanischen Daten für den Baltischen Bernstein

Pupal exuvia of an adelid case-bearing moth (Lepidoptera) from Bitterfeld Amber (Eocene)

A pupal exuvia of an adelid case-bearing caterpillar is described from Eocene Bitterfeld amber. The dumpbell-shaped case differs from the more abundant conical cases of bagworms (Psychidae), and is typical of either Longhorn Moths (Adelidae) or Clothes Moths (Tineidae). Based on the large antennal scape and elongate flagellomers of the pupal antennas the fossil is tentatively affiliated to Adelidae. This discovery represents the first record of a fossil pupa of this type from amber. The fossil indicates that the site of Bitterfeld/Baltic amber formation was the natural habitat of these case-bearing caterpillars, and also the site where they finally pupated and hatched.Eine Puppen-Exuvie einer Sack-tragenden Adeliden-Raupe aus dem Eozänen Bitterfelder Bernstein wird beschrieben. Die hantelförmigen Säcke unterscheiden sich von den häufiger vorkommenden konischen Säcken der Sackträger (Psychidae) und sind typisch sowohl für Langhornmotten (Adelidae) als auch Echte Motten (Tineidae). Basierend auf dem großen Antennenschaft und gestreckten Flagellomeren wird der Fund eher den Adelidae zugeordnet. Dies ist die erste Beschreibung einer solchen Puppe in Bernstein. Der Fund unterstreicht, dass derartige Sack-tragenden Raupen am Bildungsort des Bitterfeld bzw. Baltischen Bernsteins lebten und sich dann auch dort verpuppten und schlüpften

Control of pore geometry in soil microcosms and its effect on the growth and spread of <i>Pseudomonas </i>and <i>Bacillus</i> sp.

Simplified experimental systems, often referred to as microcosms, have played a central role in the development of modern ecological thinking on issues ranging from competitive exclusion to examination of spatial resources and competition mechanisms, with important model-driven insights to the field. It is widely recognized that soil architecture is the key driver of biological and physical processes underpinning ecosystem services, and the role of soil architecture and soil physical conditions is receiving growing interest. The difficulty to capture the architectural heterogeneity in microcosms means that we typically disrupt physical architecture when collecting soils. We then use surrogate measures of soil architecture such as aggregate size distribution and bulk-density, in an attempt to recreate conditions encountered in the field. These bulk-measures are too crude and do not describe the heterogeneity at microscopic scales where microorganisms operate. In the current paper we therefore ask the following questions: (i) To what extent can we control the pore geometry at microscopic scales in microcosm studies through manipulation of common variables such as density and aggregate size?; (ii) What is the effect of pore geometry on the growth and spread dynamics of bacteria following introduction into soil? To answer these questions, we focus on Pseudomonas sp. and Bacillus sp. We study the growth of populations introduced in replicated microcosms packed at densities ranging from 1.2 – 1.6 g cm-3, as well as packed with different aggregate sizes at identical bulk-density. We use X-ray CT and show how pore geometrical properties at microbial scales such as connectivity and solid-pore interface area, are affected by the way we prepare microcosms. At a bulk-density of 1.6 g cm-3 the average number of Pseudomonas was 63% lower than at a bulk-density of 1.3 g cm-3. For Bacillus this reduction was 66 %. Depending on the physical conditions, bacteria in half the samples took between 1.62 and 9.22 days to spread 1.5 cm. Bacillus did spread faster than Pseudomonas and both did spread faster at a lower bulk-density. Our results highlight the importance that soil physical properties be considered in greater detail in soil microbiological studies than is currently the case

Fossil water lily fruits with seeds Nymphaea subgenus Lotos, from the Oligocene of Armissan/Narbonne (France)

Based on specimens from a historical collection from the classical Oligocene locality Armissan (Southern France) fossil fruits of Nymphaeaceae are described that can be affiliated to the Nymphaeaceae genus Nymphaea subgenus Lotos with confidence. Such findings were first described in 1865 by Saporta from Armissan as an extinct genus, Anoectomeria. However, in the absence of preserved seeds, and due to a misinterpretation of the organisation of the fruits, the fossils could only be affiliated to Nymphaeaceae in general. The identification of the historical specimens with preserved seeds allows a new interpretation of such fossils and, hence their identification as fruits of the subgenus Lotos. Especially the characteristical mode of fruit dehiscence, which leads to typical stigmatic discs in extant as well as in fossil specimens, confirms this affiliation. In this study, the flowers/fruits described by Saporta (rhizome, leaves and isolated seeds were also included in his taxa) are revised to Nymphaea (subgenus Lotos) brongniartii. Comparable Paleogene fossils from other localities are also discussed. Based on N. (L.) brongniartii the minimal geological age of the subgenus Lotos can be determined as Late Oligocene. By interpretation of the comparable Paleogene fossils as belonging to subgenus Lotos the minimal geological age of this taxon would even be Middle Eocene. The Late Oligocene minimal geological age of Lotos is in agreement with phylogenetic trees based on molecular data and allows a better calibration of molecular phylogenetic trees of Nymphaeaceae.Nach Exemplaren einer historischen Aufsammlung von der klassischen Oligozän-Fundstelle Armissan (Südfrankreich) werden fossile Nymphaeaceen-Früchte mit Samen beschrieben, die eindeutig der rezenten Nymphaeaceen Gattung Nymphaea Untergattung Lotos zuzuordnen sind. Derartige Funde wurden zuerst 1865 von Saporta ebenfalls von Armissan als Anoectomeria brongniartii, A. nana und A. media beschrieben, und konnten aber wegen des Fehlens von Samen und der Fehldeutung des Fruchtaufbaus nur dieser Kunstgattung und allgemein den Nymphaeaceae zugeordnet werden. Die Auffindung der historischen Exemplare, die anders als die von Saporta beschriebenen, Samen aufweisen und die damit mögliche Neuinterpretation dieser fossilen Früchte erlaubt eine eindeutige Zuordnung zur Untergattung Lotos. Besonders die sehr charakteristische Fruchtdehiszenz, die rezent wie fossil zu isolierten Scheiben aus verwachsenen Griffelnarben führt, erlaubt nur diese Zuordnung. Die Blüten bzw. Früchte der Saporta-Taxa (Rhizome, Blätter und isolierte Samen wurden von ihm auch jeweils in die Taxa mit einbezogen) werden hier zu Nymphaea (subgenus Lotos) brongniartii revidiert. Vergleichbare paläogene Funde von anderen Lokalitäten werden diskutiert. Mit Nymphaea (Lotos) brongniartii kann das minimale geologische Alter der Untergattung Lotos als Oberoligozän bestimmt werden. Mit der Zuordnung vergleichbarer paläogener Funde zu Lotos wäre das minimale geologische Alter sogar Mitteleozän. Das Oberoligozäne minimale geologische Alter von Lotos ist mit den aus molekularen Daten erstellten Stammbäumen vereinbar und ermöglicht eine bessere Kalibrierung molekularer Stammbäume der Nymphaeaceae

Generalized Structural Kinetic Modeling: A Survey and Guide

Many current challenges involve understanding the complex dynamical interplay between the constituents of systems. Typically, the number of such constituents is high, but only limited data sources on them are available. Conventional dynamical models of complex systems are rarely mathematically tractable and their numerical exploration suffers both from computational and data limitations. Here we review generalized modeling, an alternative approach for formulating dynamical models to gain insights into dynamics and bifurcations of uncertain systems. We argue that this approach deals elegantly with the uncertainties that exist in real world data and enables analytical insight or highly efficient numerical investigation. We provide a survey of recent successes of generalized modeling and a guide to the application of this modeling approach in future studies such as complex integrative ecological models

Combination of techniques to quantify the distribution of bacteria in their soil microhabitats at different spatial scales

To address a number of issues of great societal concern at the moment, like the sequestration of carbon, information is direly needed about interactions between soil architecture and microbial dynamics. Unfortunately, soils are extremely complex, heterogeneous systems comprising highly variable and dynamic micro-habitats that have significant impacts on the growth and activity of inhabiting microbiota. Data remain scarce on the influence of soil physical parameters characterizing the pore space on the distribution and diversity of bacteria. In this context, the objective of the research described in this article was to develop a method where X-ray microtomography, to characterize the soil architecture, is combined with fluorescence microscopy to visualize and quantify bacterial distributions in resin-impregnated soil sections. The influence of pore geometry (at a resolution of 13.4 μm) on the distribution of Pseudomonas fluorescens was analysed at macro- (5.2 mm × 5.2 mm), meso- (1 mm × 1 mm) and microscales (0.2 mm × 0.2 mm) based on an experimental setup simulating different soil architectures. The cell density of P. fluorescens was 5.59 x 107(SE 2.6 x 106) cells g−1 soil in 1–2 mm and 5.84 x 107(SE 2.4 x 106) cells g−1 in 2–4 mm size aggregates soil. Solid-pore interfaces influenced bacterial distribution at micro- and macroscale, whereas the effect of soil porosity on bacterial distribution varied according to three observation scales in different soil architectures. The influence of soil porosity on the distribution of bacteria in different soil architectures was observed mainly at the macroscale, relative to micro- and mesoscales. Experimental data suggest that the effect of pore geometry on the distribution of bacteria varied with the spatial scale, thus highlighting the need to consider an “appropriate spatial scale” to understand the factors that regulate the distribution of microbial communities in soils. The results obtained to date also indicate that the proposed method is a significant step towards a full mechanistic understanding of microbial dynamics in structured soils