On the close relationship between speciation, inbreeding and recessive mutations.

Whilst the principle of adaptive evolution is unanimously recognised as being caused by the process of natural selection favouring the survival and/or reproduction of individuals having acquired new advantageous traits, a consensus has proven much harder to find regarding the actual origin of species. Indeed, since speciation corresponds to the establishment of reproductive barriers, it is difficult to see how it could bring a selective advantage because it amounts to a restriction in the opportunities to breed with as many and/or as diverse partners as possible. In this regard, Darwin himself did not believe that reproductive barriers could be selected for, and today most evolutionary biologists still believe that speciation can only occur through a process of separation allowing two populations to diverge sufficiently to become infertile with one another. I do, however, take the view that, if so much speciation has occurred, and still occurs around us, it cannot be a consequence of passive drift but must result from a selection process, whereby it is advantageous for groups of individuals to reproduce preferentially with one another and reduce their breeding with the rest of the population. 

In this essay, I propose a model whereby new species arise by “budding” from an ancestral stock, via a process of inbreeding among small numbers of individuals, driven by the occurrence of advantageous recessive mutations. Since the phenotypes associated to such mutations can only be retained in the context of inbreeding, it is the pressure of the ancestral stock which will promote additional reproductive barriers, and ultimately result in complete separation of a new species. I thus contend that the phenomenon of speciation would be driven by mutations resulting in the advantageous loss of certain functions, whilst adaptive evolution would correspond to gains of function that would, most of the time be dominant.

A very important further advantage of inbreeding is that it reduces the accumulation of recessive mutations in genomes. A consequence of the model proposed is that the existence of species would correspond to a metastable equilibrium between inbreeding and outbreeding, with excessive inbreeding promoting speciation, and excessive outbreeding resulting in irreversible accumulation of recessive mutations that could ultimately only lead to the species extinction. 
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The existence of species rests on a metastable equilibrium between inbreeding and outbreeding

Background: Speciation corresponds to the progressive establishment of reproductive barriers between groups of individuals derived from an ancestral stock. Since Darwin did not believe that reproductive barriers could be selected for, he proposed that most events of speciation would occur through a process of separation and divergence, and this point of view is still shared by most evolutionary biologists today. 

Results: I do, however, contend that, if so much speciation occurs, it must result from a process of natural selection, whereby it is advantageous for individuals to reproduce preferentially within a group and reduce their breeding with the rest of the population, leading to a model whereby new species arise not by populations splitting into separate branches, but by small inbreeding groups “budding” from an ancestral stock. This would be driven by several advantages of inbreeding, and mainly by advantageous recessive phenotypes, which could only be retained in the context of inbreeding. Reproductive barriers would thus not arise passively as a consequence of drift in isolated populations, but under the selective pressure of ancestral stocks. Most documented cases of speciation in natural populations appear to fit the model proposed, with more speciation occurring in populations with high inbreeding coefficients, many recessive characters identified as central to the phenomenon of speciation, with these recessive mutations expected to be surrounded by patterns of limited genomic diversity.

Conclusions: Whilst adaptive evolution would correspond to gains of function that would, most of the time, be dominant, the phenomenon of speciation would thus be driven by mutations resulting in the advantageous loss of certain functions since recessive mutations very often correspond to the inactivation of a gene. A very important further advantage of inbreeding is that it reduces the accumulation of recessive mutations in genomes. A consequence of the model proposed is that the existence of species would correspond to a metastable equilibrium between inbreeding and outbreeding, with excessive inbreeding promoting speciation, and excessive outbreeding resulting in irreversible accumulation of recessive mutations that could ultimately only lead to the extinction.
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Essay: On the close relationship between speciation, inbreeding and recessive mutations.

Whilst the principle of adaptive evolution is unanimously recognised as being caused by the process of natural selection favouring the survival and/or reproduction of individuals having acquired new advantageous traits, a consensus has proven much harder to find regarding the actual origin of species. Indeed, since speciation corresponds to the establishment of reproductive barriers, it is difficult to see how it could bring a selective advantage because it amounts to a restriction in the opportunities to breed with as many and/or as diverse partners as possible. In this regard, Darwin himself did not believe that reproductive barriers could be selected for, and today most evolutionary biologists still believe that speciation can only occur through a process of separation allowing two populations to diverge sufficiently to become infertile with one another. I do, however, take the view that, if so much speciation has occurred, and still occurs around us, it cannot be a consequence of passive drift but must result from a selection process, whereby it is advantageous for groups of individuals to reproduce preferentially with one another and reduce their breeding with the rest of the population. 
In this essay, I propose a model whereby new species arise by “budding” from an ancestral stock, via a process of inbreeding among small numbers of individuals, driven by the occurrence of advantageous recessive mutations. Since the phenotypes associated to such mutations can only be retained in the context of inbreeding, it is the pressure of the ancestral stock which will promote additional reproductive barriers, and ultimately result in complete separation of a new species. I thus contend that the phenomenon of speciation would be driven by mutations resulting in the advantageous loss of certain functions, whilst adaptive evolution would correspond to gains of function that would, most of the time be dominant.
A very important further advantage of inbreeding is that it reduces the accumulation of recessive mutations in genomes. A consequence of the model proposed is that the existence of species would correspond to a metastable equilibrium between inbreeding and outbreeding, with excessive inbreeding promoting speciation, and excessive outbreeding resulting in irreversible accumulation of recessive mutations that could ultimately only lead to the species extinction. 
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National Wildlife Refuges and Intensive Management in Alaska: Another Case for Preemption

Developing high quality software is difficult. Traditional software engineering methods emphasizes on structured and linear workflow of activities methods that have been criticized due to their rigid and inflexible nature. Recently, agile software engineering approaches such as Scrum have gained popularity in the software industry. These methods emphasize flexibility, speed, transparency, and teamwork aspects. In this thesis, investigation and comparison of three modern production practices and principles done, these include; Kanban, the 5S workplace organization method and Toyota Production System (TPS). The goal has been to identity features of these production philosophies and analyzed how they might contribute to software engineering processes, particularly to improve Scrum. The study indicates that many principles from these production approaches have been implemented in Scrum. However, the Kanban, 5S and TPS principles of Visibility are just partially implemented in Scrum. Scrum overlooks many aspects of programming that need to be visualized such as code quality aspects (testing) and representations of the actual software structure under development

The Effects of Private Equity-Backing in the European Acquisitions of Unlisted Companies.

Using a sample of acquisitions of unlisted firms completed by public companies from 17 Western European countries over the period 2003-2008, this study investigates whether private equity (PE)-backing of acquired firms has an impact on announcement period abnormal returns to acquirers. 12.5% of the unlisted targets are PE-backed. Acquisitions of PE-backed firms are more likely to involve larger acquirers, larger targets relative to acquirer size, and high-tech targets; they are more likely to occur in an unrelated industry and to be partially stock-financed. Of most importance for this study, I find that the presence of PE investors in the targets leads to significantly lower acquirer announcement returns. This effect remains after controlling for a large set of deal and acquirer characteristics. Moreover, these results are robust to the use of a propensity score matching method on multiple deal characteristics and suggest that PE investors increase the negotiating power of target shareholders.Private Equity; Acquisitions; Acquirer Returns; Unlisted Targets;

Test of the relation between travel and activities times : different representations of a demand derived from activity participation

The paper tests linear and non-linear specifications of the relationship between travel times and activity times, in 4 four French and three Swiss cities, observed at two different periods. First, following Kitamura et al. (1992), we test proportional assignment of total daily available time to activities (including transport). Second, proportionality is tested between (1) daily travel time associated with a given purpose with respect of the daily activity duration and (2) the travel time associated with the duration of the activity at destination. This last specification tests the travel time ratio proposed by Dijst and Vidakovic (2000). Third, because of the non appropriateness of the OLS method for analysing non-normally distributed duration data, we estimate travel time budgets in the duration model framework. We obtain non-linear relation between travel time and activity times. Only daily leisure time and daily travel time are fixed proportion of total daily available time. At disaggregated level, the trip duration do not show proportionality with activity duration. Leisure and shopping activities exhibit increasing and convex relation with travel time.TIME USE;TRAVEL TIME;ACTIVITY BASED ANALYSIS

The role of travel time budgets – Representation of a demand derived from activity participation

The paper exams the relationships between travel and activity times, in 7 travel surveys from 4 French and 3 Swiss cities, observed at two different periods. First, we test proportional assignment of total daily available time to activities (including transport). Second, proportionality is tested between (1) daily travel time of a given purpose with respect of the daily activity duration and (2) the trip time associated to the duration of the activity at destination. Only daily leisure time and daily travel time are fixed proportion of total daily available time. At disaggregated level, the trip duration do not show proportionality with activity duration. Finally questioning the proportionality and the linear adjustment, we regress the travel time budgets using duration models. This methodology is particularly adapted to the duration analysis and leads to non-linear relation between travel time and activity times. Leisure and shopping activities exhibit increasing and convex travel time intensities.activity-based analysis - time use - travel time

Travel Time Budget – Decomposition of the Worldwide Mean

The paper is concerned with the travel activity and more specifically the urban travel time during a day. This individual mean travel time budget (TTB) has been hypothesised by Zahavi (1980) to be a constant amount of time close to 1 hour per day. This TTB seems to be stable between different cities and between different time periods. Under the TTB stability hypothesis, travel time-savings are totally reinvested in transport. This reinvestment mechanism could then explain the urban sprawl, and give to the increasing speeds all the responsibilities of the “urban transport diseases”. However, the TTB stability seems to be valid at the world aggregate level only. The paper proposes to explore finer scales of observation of the TTB: from the aggregate to the desaggregate levels of observation. First, a worldwide comparison of the mean TTB of 100 cities is produced. Second a hazard based model for the individual TTB of the French city of Lyon is constructed. Hence, two opposite urban models appear at the aggregate level: an extensive urban model of which development is based on extensive consumption of space and time resources, and an intensive urban model restricting its spatial and temporal extension. At the desaggregate level, the analysis identifies the relationships between the individual TTB and the socio-economic variables and the mobility and activities attributes. Finally, the model seems to indicate that the traditional hypothesis of the minimisation of the temporal costs of travel is unsuitable to model the behaviour of the whole urban population.Duration model ; Travel Time Budget ; Zahavi's hypothesis ; Worldwide comparison