The Adaptive Radiation of Cichlid Fish in Lake Tanganyika: A Morphological Perspective

Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation

Untersuchungen zur Oxidationsstabilität von Leinöl

Leinöl ist wegen seines hoch ungesättigten Grades leicht oxidationsanfällig. Aufgrund der schonenden Kalt- oder Warmpressung beträgt die Ölausbeute nur etwa 25-27%, der Rest verbleibt im Presskuchen. Diese dienten in dieser Arbeit dem Versuch, die Lebensdauer des warm- und kaltgepressten Leinöls durch die Zugabe antioxidativ wirksamer Substanzen aus ethanolischem Presskuchen-Extrakt zu verlängern. Zur Überprüfung des Oxidationszustandes wurden die Thiobarbitursäurezahl sowie die Tocopherole im Normalphasen-HPLC mit Fluoreszenzdetektor bestimmt, für die Ermittlung der Oxidationsstabilität wurde ein Rancimat eingesetzt. Es wurden verschiedene Kombinationen bestimmter Mengen an Presskuchen-Extrakt zu 20 g Leinöl mit zusätzlicher Unterscheidung des Zeitpunkts der Ethanol-Entfernung im Ranzimat bei 120°C untersucht. Daraus erwies sich das kaltgepresste Leinöl mit Extrakt aus 20 g Presskuchen und nachfolgender Entfernung des Ethanols am geeignetsten. Leinöl enthält vorwiegend das γ-Tocopherol mit etwa 45 mg/100 g und nur Spuren der α- und δ-Tocopherole. Extraktzusätze konnten lediglich den Gehalt der letzten beiden Tocopherole etwas erhöhen. Die Entwicklung des angereicherten, kaltgepressten Leinöls im Vergleich zum Kontrollöl wurde anschließend während eines 11-tägigen Schaal-Ofen-Tests bei 60°C beobachtet. Mit der Anreicherung konnte ein Protektionsfaktor von 7,8 erzielt werden. Alle Tocopherole wurden beim Kontrollöl bereits während bzw. am Ende der Lagerung (α > δ > γ) aufgebraucht, wohingegen sie beim angereicherten Leinöl auch gegen Ende der Untersuchung noch immer relativ unverändert erschienen. Interaktionen mit den im ethanolischen Extrakt mitgewonnenen glycosylierten phenolischen Säuren dürften für die erhöhte Oxidationsstabilität ausschlaggebend gewesen sein. Weitere Untersuchungen hinsichtlich der Zusammensetzung des Presskuchen-Extrakts sowie der Aktivität der enthaltenen phenolischen Substanzen wären nötig

Zur Wirksamkeit von Mindfulness-Based Stress Reduction (MBSR) in Pflegeberufen hinsichtlich Konzentration

In der vorliegenden Studie wurde der Einfluss eines kurzen 4-wöchigen Mindfulness-Based Stress Reduction-Training (kurz: MBSR) auf die voluntäre Aufmerksamkeit und das autonome Nervensystem (ANS) untersucht. Wichtiges Ziel war ebenfalls theoretische Konzeptionalisierungen zur Beziehung zwischen Mindfulness und Aufmerksamkeitsprozessen zu analysieren. Die Untersuchung wurde am Krankenpflegepersonal durchgeführt, welches einem MBSR-Treatment (n=23) oder einer Wartelisten-Kontrollgruppe (n=21) zugeordent wurde. Zu beiden Messzeitpunkten vor und nach der Intervention wurden Tests und subjektive Fragebögen zur voluntären Aufmerksamkeit, Wohlbefinden und Burnout vorgegeben. Mindfulness wurde mittels eines Fragebogens nur zum zweiten Messzeitpunkt erhoben. Zusätzlich wurden physiologische Variablen (Elektrodermale Aktiviät, Herzratenvariabilität, Atrial und Herzrate) während der Zeit des Fragebogenausfüllens, Pause oder Meditationsbedingung und während eines Aufmerksamkeitstests gemessen. Die Teilnahme an einem kurzen MBSR-Training konnte nicht mit einer signifikanten Verbesserung in der voluntären Aufmerksamkeit im Vergleich zur Kontrollgruppe assoziiert werden. Hohe Scores in Mindfulness nach dem MBSR-Training korrelierten jedoch signifikant mit erhöhten Werten in der voluntären Aufmerksamkeit. Ein Einfluss des MBSR-Trainings konnte auch auf das autonome Nervensystem in der Low Frequency, welche für sympathische Aktivität steht, gezeigt werden. Abschließend wurde mittels eines Feedbackbogens die Mindfulness-Intervention von den Versuchsteilnehmern als ein wirksames Treatment im Umgang mit Stress bewertet. Die Auswirkungen dieser Ergebnisse auf die zukünftige empirische Forschung hinsichtlich des Effekts von Mindfulness auf das autonome Nervensystem und Aufmerksamkeit wird diskutiert.This study was designed to test the impact of a brief 4-week Mindfulness-Based Stress Reduction (MBSR) course on voluntary attention and the autonomous nervous system (ANS). One corollary aim of this study was to analyze theoretical conceptualizations that highlight the fundamental relationship between mindfulness and attentional processes. Towards that end, nurses and nurse aids were tested before and after assignment to MBSR (n= 23) or a wait-list control (n= 21). Testing included measures of voluntary attention, as well as self-report measures of emotional well-being, burnout and mindfulness. Additionally, physiological assessments (skin conductance level, atrial, heart rate and heart rate variability indices of time and frequency domain methods) were obtained in three instances: during the period of answering the self-report questionnaires, a 5-minute break and during the attention task. Participation in the MBSR course was not associated with significant improvements in voluntary attention relative to the control group. However, high scores in mindfulness after MBSR were correlated with improvements in voluntary attention. Furthermore, the impact of MBSR on the autonomous nervous system could be seen in the low frequency component of heart rate variability, which suggests greater sympathetic influence. The mindfulness intervention itself was rated, by nurses and nurse aids as a helpful treatment to deal with stress. Implications of these results and future directions for empirical study related to the influence of mindfulness an autonomous nervous system and attention are discussed

Nuclear and mitochondrial data reveal different evolutionary processes in the Lake Tanganyika cichlid genus Tropheus

<p>Abstract</p> <p>Background</p> <p>Cichlid fishes are notorious for their wealth of intra- and interspecific colour pattern diversity. In Lake Tanganyika, the endemic genus <it>Tropheus </it>represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved. Previous studies of mitochondrial DNA sequence data revealed polyphyly of the six nominally described species and complex phylogeographic patterns influenced by lake level fluctuations and population admixture, and suggested the parallel evolution of similar colour patterns in divergent evolutionary lineages. A gene tree of a rapidly radiating group may be subject to incomplete and stochastic lineage sorting, and to overcome this problem we used multi-locus, nuclear AFLP data in comparison with mtDNA sequences to study diversification, migration and introgression in <it>Tropheus </it>colour morphs in Lake Tanganyika.</p> <p>Results</p> <p>Significant incongruence between phylogenetic reconstructions from mitochondrial and AFLP data suggested incomplete sorting of mitochondrial haplotypes as well as frequent introgression between differentiated lineages. In contrast to the mitochondrial phylogeny, the AFLP phenogram was largely congruent with species classifications, colour pattern similarities, and in many cases also with the current geographic distribution of populations, and did not produce evidence of convergent colour pattern evolution. Homoplasy in the AFLP data was used to identify populations that were strongly affected by introgression.</p> <p>Conclusion</p> <p>Different evolutionary processes were distinguished by the combination of mitochondrial and AFLP data. Mitochondrial phylogeographic patterns retained signals of large-scale migration events triggered by historical, major lake level fluctuations, whereas AFLP data indicated genetic cohesion among local groups of populations resulting from secondary contact of adjacent populations in the course of the more frequently occurring, minor lake level fluctuations. There was no support for the parallel evolution of similar colour patterns in the AFLP data. Genetic signatures of introgression and hybridisation detected in several populations suggest that lake level fluctuations drove the stunning diversification of <it>Tropheus </it>morphs not only through population fragmentation, but also by promoting hybridisation between differentiated morphs in secondary contact.</p

Ancestral state reconstruction reveals multiple independent evolution of diagnostic morphological characters in the "Higher Oribatida" (Acari), conflicting with current classification schemes

<p>Abstract</p> <p>Background</p> <p>The use of molecular genetic data in phylogenetic systematics has revolutionized this field of research in that several taxonomic groupings defined by traditional taxonomic approaches have been rejected by molecular data. The taxonomic classification of the oribatid mite group Circumdehiscentiae ("Higher Oribatida") is largely based on morphological characters and several different classification schemes, all based upon the validity of diagnostic morphological characters, have been proposed by various authors. The aims of this study were to test the appropriateness of the current taxonomic classification schemes for the Circumdehiscentiae and to trace the evolution of the main diagnostic traits (the four nymphal traits scalps, centrodorsal setae, sclerits and wrinkled cuticle plus octotaxic system and pteromorphs both in adults) on the basis of a molecular phylogenetic hypothesis by means of parsimony, likelihood and Bayesian approaches.</p> <p>Results</p> <p>The molecular phylogeny based on three nuclear markers (28S rDNA, <it>ef-1α</it>, <it>hsp82</it>) revealed considerable discrepancies to the traditional classification of the five "circumdehiscent" subdivisions, suggesting paraphyly of the three families Scutoverticidae, Ameronothridae, Cymbaeremaeidae and also of the genus <it>Achipteria</it>. Ancestral state reconstructions of six common diagnostic characters and statistical evaluation of alternative phylogenetic hypotheses also partially rejected the current morphology-based classification and suggested multiple convergent evolution (both gain and loss) of some traits, after a period of rapid cladogenesis, rendering several subgroups paraphyletic.</p> <p>Conclusions</p> <p>Phylogenetic studies revealed non-monophyly of three families and one genus as a result of a lack of adequate synapomorphic morphological characters, calling for further detailed investigations in a framework of integrative taxonomy. Character histories of six morphological traits indicate that their evolution followed a rather complex pattern of multiple independent gains (and losses). Thus, the observed pattern largely conflicts with current morphological classifications of the Circumdehiscentiae, suggesting that the current taxonomic classification schemes are not appropriate, apart from a recently proposed subdivision into 24 superfamilies.</p

Mitochondrial phylogeny and phylogeography of East African squeaker catfishes (Siluriformes: Synodontis)

BACKGROUND: Squeaker catfishes (Pisces, Mochokidae, Synodontis) are widely distributed throughout Africa and inhabit a biogeographic range similar to that of the exceptionally diverse cichlid fishes, including the three East African Great Lakes and their surrounding rivers. Since squeaker catfishes also prefer the same types of habitats as many of the cichlid species, we hypothesized that the East African Synodontis species provide an excellent model group for comparative evolutionary and phylogeographic analyses. RESULTS: Our analyses reveal the existence of six major lineages of Synodontis in East Africa that diversified about 20 MYA from a Central and/or West African ancestor. The six lineages show a clear geographic patterning. Two lineages are endemic to Lake Tanganyika (plus one non-endemic representative), and these are the only two Synodontis lineages that diversified further into a small array of species. One of these species is the cuckoo catfish (S. multipunctatus), a unique brood parasite of mouthbrooding haplochromine cichlids, which seems to have evolved in parallel with the radiation of its cichlid host lineage, the Tropheini. We also detect an accelerated rate of molecular evolution in S. multipunctatus, which might be the consequence of co-evolutionary dynamics. CONCLUSION: We conclude that the ancestral lineage of today's East African squeaker catfish fauna has colonized the area before the Great Lakes have formed. This ancestor diversified rapidly into at least six lineages that inhabit lakes and rivers in East Africa. Lake Tanganyika is the only lake harboring a small species flock of squeaker catfishes

Evolutionary History of Lake Tanganyika's Predatory Deepwater Cichlids

Hybridization among littoral cichlid species in Lake Tanganyika was inferred in several molecular phylogenetic studies. The phenomenon is generally attributed to the lake level-induced shoreline and habitat changes. These allow for allopatric divergence of geographically fragmented populations alternating with locally restricted secondary contact and introgression between incompletely isolated taxa. In contrast, the deepwater habitat is characterized by weak geographic structure and a high potential for gene flow, which may explain the lower species richness of deepwater than littoral lineages. For the same reason, divergent deepwater lineages should have evolved strong intrinsic reproductive isolation already in the incipient stages of diversification, and, consequently, hybridization among established lineages should have been less frequent than in littoral lineages. We test this hypothesis in the endemic Lake Tanganyika deepwater cichlid tribe Bathybatini by comparing phylogenetic trees of Hemibates and Bathybates species obtained with nuclear multilocus AFLP data with a phylogeny based on mitochondrial sequences. Consistent with our hypothesis, largely congruent tree topologies and negative tests for introgression provided no evidence for introgressive hybridization between the deepwater taxa. Together, the nuclear and mitochondrial data established a well-supported phylogeny and suggested ecological segregation during speciation

In vacancies in InN grown by plasma-assisted molecular beam epitaxy

The authors have applied positron annihilation spectroscopy to study the effect of different growth conditions on vacancy formation in In- and N-polar InN grown by plasma-assisted molecular beam epitaxy. The results suggest that the structural quality of the material and limited diffusion of surface adatoms during growth dictate the In vacancy formation in low electron-density undoped epitaxial InN, while growth conditions and thermodynamics have a less important role, contrary to what is observed in, e.g., GaN. Further, the results imply that in high quality InN, the electron mobility is likely limited not by ionized point defect scattering, but rather by threading dislocations.Comment: 15 pages, 2 figure