18,363 research outputs found
ADAM SMITH'S OPTIMISTIC TELEOLOGICAL VIEW OF HISTORY
No full textAdam Smith's four-stage theory provides the framework for his writings on history. The fourth stage is the commercial epoch; the culmination of history in this stage is a key component in the conventional interpretation of Adam Smith as a prophet of commercialism. In two historical case studies Smith shows the capacity of commercial society to regenerate itself. This potent capacity suggests that commercial society is inevitable. At a certain point in time it also overcomes the major obstacles to its permanence. Smith's philosophy of history anticipates the end of history views of Kant and Hegel.Political Economy,
Cryptic diversity of Keratella cochlearis – genetical, morphological and demographic aspects
No full textBiodiversity is under threat in recent decades, with many natural habitats irreversibly
disappearing due to global warming and human activity. Our perception of species loss
highly depends on an accurate species estimate. However, occurrence of cryptic species (i.e.
distinct species that are impossible or difficult to distinguish based on their morphology)
hinders a correct assessment of biodiversity. Cryptic species have been described for rotifers
of the class Bdelloidea and Monogononta. Rotifers of the class Monogononta are
widespread in freshwater lakes all over the world and can serve as model organisms for
speciation and adaptation. The main aim of this thesis was to investigate and describe the genetic diversity of one of
the most common freshwater rotifer - Keratella cochlearis - in relation to its morphological
variability. Beside the assessment of genetic diversity, a detailed study of K. cochlearis life
cycle and reproductive strategy was performed. The results of the first study demonstrated that based on the cytochrome c oxidase subunit
1 (COI) gene different putative evolutionary significant units (ESU; a.k.a. cryptic species) can
be delimited in Keratella cochlearis (I). Based on morphology, two ESUs can be delimited
from the other six ESUs found. We also reported on co-occurrence of different putative ESUs
of K. cochlearis in the same lakes, and presented the first SEM pictures of K. cochlearis
females showing some detailed morphological characteristics. Life histories and demographic parameters differences between various haplotypes of K.
cochlearis were determined in the second study (II). Several differences between life history
traits and demographic parameters of haplotypes were found corroborating their status as
cryptic species and demonstrating that genetic diversity of K. cochlearis is also reflected in
demographic diversity. Additionally, morphologically deformed females occurring during the
life table experiment were documented and photographed for the first time in this species.
Moreover, the first case of an amphoteric female (producing both males and females) in K.
cochlearis was reported. In the third study (III), mitonuclear discordance in three rotifer species complexes was
assessed. Mitonuclear discordance hinders the assessment of species delimitation based on
only one gene (single-locus). Discordance between mitochondrial and nuclear phylogenies
was reported for three rotifer species complexes (K. cochlearis, Polyarthra dolichoptera,
Synchaeta pectinata) with different levels of discordance between the mitochondrial COI
and the nuclear ITS gene. The results corroborated the previous description of two ESUs in K.
cochlearis. During our studies on K. cochlearis males, we developed a method to film zooplankton in
general and rotifers specifically (IV). We connected a commercial single-lens reflex camera to
a microscope and presented an affordable system with widely available components for
filming. In filming male-female interactions of Brachionus angularis, our film showed a
thread-like structure linking male and female. However, the purpose of this structure
remained unclear. In conclusion, this PhD provided evidence for a high genetic and morphological diversity of K.
cochlearis. Existence of a species complex of K. cochlearis was corroborated by
mitochondrial and nuclear genetic information. This high genetic diversity in K. cochlearis
was reflected to some extent in life histories and morphology. First videos of K. cochlearis
males and of B. angularis males interaction with females were presente
How Might Adam Smith Pay Professors Today?
No full textAdam Smith’s proposal for paying professors was intended to induce increased faculty knowledge. If students have imperfect information about what they learn, and universities can only imperfectly measure the input of faculty time in student learning, publications may be used to measure faculty knowledge. If professors’ ability to publish is positively related to their ability to produce student learning, which universities can imperfectly measure, publications may be necessary to attract more able professors. Since research signals faculty knowledge, schools that do not value publications per se could require higher publication standards and pay higher wages than schools that value only publications.
High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence
No full textRotifers are ubiquitous freshwater animals for which many complexes of cryptic species (i.e. distinct species that are morphologically difficult to distinguish) are described. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region (Italy) and investigated mitochondrial genetic diversity in K. cochlearis in relation to detailed lorica measurements. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units (ESUs). Based on 248 sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology. Specifically, several morphological characteristics (i.e. spinelets, bended median ridge, and posterior spine) were found in specimens of different putative ESUs, and thus, these characters seem to be of poor discriminatory value. Furthermore, different putative ESUs of K. cochlearis were found in the same lake. We conclude that the high mitochondrial genetic diversity may be linked to tolerance of K. cochlearis to varying environmental condition
ADAM SMITH'S VIEW OF HISTORY: CONSISTENT OR PARADOXICAL?
No full textThe conventional interpretation of Adam Smith is that he is a prophet of commercialism. The liberal capitalist reading of Smith is consistent with the view that history culminates in commercial society. The first part of the article develops this optimistic interpretation of Smith's view of history. Smith implies that commercial society is the end of history because 1) it supplies the ends of nature that he identifies; 2) it is inevitable; and 3) it is permanent. The second part of the article shows that Smith has some dark moments in his writings where he seems to reject completely such teleological notions. In this more civic humanist mood he confesses that commercial society does not supply the ends of nature, nor is it inevitable, nor is it permanent. Both views exist in Smith and the commentator is forced to choose between passages in Smith's work in order to support a particular interpretation of the former's view of history.Political Economy,
Inter-species sex: male-inducing experiments with the rotifer Keratella cochlearis
No full textIn the genus Brachionus (Monogononta) the switch from asexual to sexual reproduction is triggered by a chemical signal produced by the species. In Brachionus, the main environmental trigger for production of this chemical cue is crowding but for other rotifer species daylight or dietary quality may also serve as trigger. The species-specific property of the signal is variable depending on genetic relatedness of the trigger responding species.
We performed male-induction experiments with different cryptic species of the monogonont rotifer Keratella cochlearis. Cryptic species were identified by the Generalized Mixed Yule Coalescent model.
We performed a set of laboratory experiments in chambers of 20 mL volume separated by a 30 μm mesh where chemical releasing (trigger) species and receiving (response) species were present, respectively. Because the nature of the sex-inducing chemical is not known, this approach allowed us to expose different cryptic species of K. cochlearis by almost direct contact, mimicking natural conditions.
We discuss our results in the light of genetic relatedness of the tested cryptic species and compare our results to Brachionus
Filming of zooplankton: a case study of rotifer males and Daphnia magna
No full textFilming live organisms can give new insights into the hidden life of plankton. Accessibly priced digital cameras are now available for a large range of users. Here, we demonstrate the technical setup and workflow of using a single-lens reflex (DSLR) camera to film the behaviour of males of two rotifer species, Brachionus angularis Gosse (1851) and Keratella cochlearis Gosse (1851), and of the cladoceran Daphnia magna Straus (1820). Rotifers are cyclical parthenogens that produce males only under certain environmental conditions. Thus, knowledge on rotifer males is still limited because of their ephemeral nature and because they are often smaller than females. We filmed males of B. angularis and K. cochlearis with a DSLR camera connected to a compound microscope to better understand their morphology and behaviour in comparison to conspecific females. While written descriptions have their scientific value, seeing is complementary because everyone can verify what has been described. We made our videos publicly accessible through links connected to the paper. Our videos are, to our best knowledge, the first on males of B. angularis and K. cochlearis. Furthermore, we filmed the behavioural response of D. magna to ultraviolet (UV) radiation with a macro lens attached to the DSLR camera. Approaches like this are valuable tools in environmental teaching. To see live organisms with one’s own eyes may contribute to raising public awareness about the value of water resources and their hidden communities. In summary, filming can be a valuable tool to ignite scientific discussion, but the videos need an open-access platform where they can be referenced in a topic-related order.</p
Rotifer cryptic diversity: case study Keratella cochlearis
No full textTraditional taxonomy may underestimate biodiversity because of the occurrence of cryptic species (i.e. different morphologically indistinguishable species). This seems to be especially true for microscopic animals such as rotifers. The merging of different cryptic species that have different environmental preferences in one taxon may hinder our understanding of species-environment relationships. Here wWe investigated the occurrence of cryptic diversity within the monogonont rotifer Keratella cochlearis. Keratella cochlearis is a ubiquitous species occurring across environmental gradients and the presence of cryptic species can be suspected.
We sampled 17 lakes of differenting in their trophic state, chemical parameters and altitude in the region Trentino-South Tyrol region (North Italy). We measured the main morphological characteristics of the lorica for each single individual of K. cochlearis prior to sequencing that was also investigated genetically. We sequenced the partial cytochrome c oxidase subunit 1 and inferred cryptic species by the Generalized Mixed Yule Coalescence (GMYC) model.
We found 8 GMYC entities (cryptic species) whose lorica measurements showed a large phenotypic plasticity. Furthermore, most cryptic species occurred in many lakes with few exceptions. We discuss our results in relation to ecological key variables such as trophic state, conductivity, altitude and chemical parameters
Life history traits and demographic parameters in the Keratella cochlearis (Rotifera, Monogononta) species complex
No full textA recent study based on DNA taxonomy indicated that the widespread rotifer Keratella cochlearis comprises several evolutionarily significant units (ESUs). Identification of ESUs based on DNA taxonomy alone is problematic and usually requires morphological, demographic, and/or ecological evidence. We isolated three haplotypes belonging to two ESUs of K. cochlearis and conducted life table experiments to investigate if this genetic diversity is reflected in demography. We found significant differences between haplotypes in life history traits (average lifespan, number of offspring, and percent of rejected eggs) and in demographic parameters (instantaneous growth rate, generation time, and net reproductive rate of the populations). During the experiments, all the haplotypes produced abnormal females with a deformed lorica, which was never reported before in K. cochlearis. We also report the first case of an amphoteric female (producing both females and males) in K. cochlearis. We hypothesize that K. cochlearis haplotypes and thus ESUs may exhibit niche differentiation through their different life histories. The link between demographic parameters of K. cochlearis and niche utilization requires further research
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