Wege der Mikroevolution und Artbildung bei Bienen (Apoidea, Hymenoptera): Populationsgenetische und empirische Aspekte

Bees are haplodiploid organisms: haploid males develop from unfertilized eggs, diploid females from fertilized eggs. Under haplodiploidy, deleterious mutations are effectively purged by purifying selection on haploid males. Therefore, genetic load and inbreeding depression are low in bees, which allow them to exist in very small populations, and facilitate the colonization of new areas and habitats by single fertilized females. Exceptions caused by distinct modes of genetic sex-determination are discussed. Owing to the purifying selection and the higher rate of genetic drift in small populations, the genetic variation of bees is only one third of the variation of diploid insects. As a consequence, bees have less genetic adaptability to environmental change, for which they compensate by exhibiting higher learning ability and greater behavioural plasticity than many other insect taxa. Most bee species need specific microclimatic conditions to perform the proper flight behaviour to provision their nests with larval food. Energy flow and metabolic rates in flight muscles of bees are among the highest ever measured in animal tissue. The temperature dependence of the enzymes which drive the flight muscle metabolism is therefore of critical importance for the functioning of the system. Mutations which change the thermal tolerance range of one of those enzymes might lead to changing habitat requirements, and parapatric or allochronous population divergence. The fact that bees choose their nesting site very carefully already hints at the critical role, temperature and humidity ranges play for bee development. Experiments show a remarkable dependence of learning ability and behaviour on developmental temperatures. Evolutionary and ecological aspects of social behaviour, social and cleptoparasitism, and flower choice in bees are discussed. Possible paths of population divergence and speciation are pointed out. The reproduction rate of bees is closer to the rates of primates than to that of other insects. Compared to other insects, bees evolve only slowly

Post-zygotic reproductive isolation among populations of Iris atropurpurea: The effect of spatial distance among crosses and the role of inbreeding and outbreeding depression in determining niche width

Question: What is the role of inbreeding and outbreeding depression in creating spatial patterns of reproductive isolation among populations within a species? Hypothesis: A combination of inbreeding and outbreeding effects create an optimal crossing distance at which reproductive isolation is minimal. Organism: 'Iris atropurpurea' Dinsm., an endangered and endemic Israeli plant, with a fragmented distriution throughout the coastal plain. Field sites: Two 'I. atropurpurea' populations, one in the Shafdan dunes, and one in the Netanya Iris Reserve, both ca. 19 km S or N (respectively) of Tel Aviv, on the coastal plain in Israel. Methods: We performed artificial cross-pollination within and between populations of 'I. atropurpurea' at various distances and measured seed germination and seedling survivorship. Results: Theoretical considerations led us to expect that inbreeding depression acts mostly at the small scale, and that higher offspring fitness is revealed at distances < 10 km. Results from the experiment showed that reproductive isolation acts differently in consequent stages of the hybrid life history. Pattern of total reproductive isolation among populations along a geographical axis showed different patterns in the two natural populations: while in the Netanya population no pattern appeared, in Shafdan we found a pattern of intermediate distance where reproductive isolation is the highest, and in short and long distances reproductive isolation relaxed

Speciation and the evolution of dispersal along environmental gradients

We analyze the joint evolution of an ecological character and of dispersal distance in asexual and sexual populations inhabiting an environmental gradient. Several interesting phenomena resulting from the evolutionary interplay of these characters are revealed. First, asexual and sexual populations exhibit two analogous evolutionary regimes, in which either speciation in the ecological character occurs in conjunction with evolution of short-range dispersal, or dispersal distance remains high and speciation does not occur. Second, transitions between these two regimes qualitatively differ between asexual and sexual populations, with the former showing speciation with long-range dispersal and the latter showing no speciation with short-range dispersal. Third, a phenotypic gradient following the environmental gradient occurs only in the last case, i.e., for non-speciating sexual populations evolving towards short-range dispersal. Fourth, the transition between the evolutionary regimes of long-range dispersal with no speciation and short-range dispersal with speciation is typically abrupt, mediated by a positive feedback between incipient speciation and the evolution of short-range dispersal. Fifth, even though the model of sexual evolution analyzed here does not permit assortative mating preferences, speciation occurs for a surprisingly wide range of conditions. This illustrates that dispersal evolution is a powerful alternative to preference evolution in enabling spatially distributed sexual populations to respond to frequency- dependent disruptive selection

The Evolution of Conditional Dispersal and Reproductive Isolation Along Environmental Gradients

Dispersal modulates gene flow throughout a population's spatial range. Gene flow affects adaptation at local spatial scales, and consequently impacts the evolution of reproductive isolation. A recent theoretical investigation has demonstrated that local adaptation along an environmental gradient, facilitated by the evolution of limited dispersal, can lead to parapatric speciation even in the absence of assortative mating. This and other studies assumed unconditional dispersal, so individuals start dispersing without regard to local environmental conditions. However, many species disperse conditionally their propensity to disperse is contingent upon environmental cues, such as the degree of local crowding or the availability of suitable mates. Here, we use an individual-based model in continuous space to investigate by numerical simulation the relationship between the evolution of threshold-based conditional dispersal and parapatric speciation driven by frequency-dependent competition along environmental gradients. We find that, as with unconditional dispersal, parapatric speciation occurs under a broad range of conditions when reproduction is asexual, and under a more restricted range of conditions when reproduction is sexual. In both the asexual and sexual cases, the evolution of conditional dispersal is strongly influenced by the slope of the environmental gradient: shallow environmental gradients result in low dispersal thresholds and high dispersal distances, while steep environmental gradients result in high dispersal thresholds and low dispersal distances. The later, however, remain higher than under unconditional dispersal, thus undermining isolation by distance, and hindering speciation in sexual populations. Consequently, the speciation of sexual population under conditional dispersal is triggered by a steeper gradient than under unconditional dispersal. Enhancing the disruptiveness of frequency-dependent selection, more box-shaped competition kernels dramatically lower the speciation-enabling slope of the environmental gradient

Epidemiological, evolutionary, and economic determinants of eradication tails

Despite modern medical interventions, infectious diseases continue to generate huge socio-economic losses. The benefits of eradicating a disease are therefore high. While successful with smallpox and rinderpest, many other eradication attempts have failed. Eradications require huge and costly efforts, which can be sustained only if sufficient progress can be achieved. While initial successes are usually obtained more easily, progress often becomes harder as a disease becomes rare in the eradication endgame. A long eradication tail of slowly decreasing incidence levels can frustrate eradication efforts, as it becomes unclear whether progress toward eradication is still being made and how much more needs to be invested to push the targeted disease beyond its extinction threshold. Realistic disease dynamics are complicated by evolutionary responses to interventions and by interactions among different temporal and spatial scales. Models accounting for these complexities are required for understanding the shapes of eradication tails. In particular, such models allow predicting how hard or costly eradication will be, and may even inform in which manner progress has to be assessed during the eradication endgame. Here we outline a general procedure by analyzing the eradication tails of generic SIS diseases, taking into account two major ingredients of realistic complexity: a group-structured host population in which host contacts within groups are more likely than host contacts between groups, and virulence evolution subject to a trade-off between host infectivity within groups and host mobility among groups. Disentangling the epidemiological, evolutionary, and economic determinants of eradication tails, we show how tails of different shapes arise depending on salient model parameters and on how the extinction threshold is approached. We find that disease evolution generally extends the eradication tail and show how the cost structure of eradication measures plays a key role in shaping eradication tails

Distance learning training in genetics and genomics testing for Italian health professionals: results of a pre and post-test evaluation

BACKGROUND: Progressive advances in technologies for DNA sequencing and decreasing costs are allowing an easier diffusion of genetic and genomic tests. Physicians' knowledge and confidence on the topic is often low and not suitable for manage this challenge. Tailored educational programs are required to reach a more and more appropriate use of genetic technologies. METHODS: A distance learning course has been created by experts from different Italian medical associations with the support of the Italian Ministry of Health. The course was directed to professional figures involved in prescription and interpretation of genetic tests. A pretest-post-test study design was used to assess knowledge improvement. We analyzed the proportion of correct answers for each question pre and post-test, as well as the mean score difference stratified by gender, age, professional status and medical specialty. RESULTS: We reported an improvement in the proportion of correct answers for 12 over 15 questions of the test. The overall mean score to the questions significantly increased in the post-test, from 9.44 to 12.49 (p-value < 0.0001). In the stratified analysis we reported an improvement in the knowledge of all the groups except for geneticists; the pre-course mean score of this group was already very high and did not improve significantly. CONCLUSION: Distance learning is effective in improving the level of genetic knowledge. In the future, it will be useful to analyze which specialists have more advantage from genetic education, in order to plan more tailored education for medical professionals

The Formation of Structured Cooperative Communities

A society relying upon public goods must avoid a tragedy of the commons; it will otherwise wither owing to the collapse of cooperative enterprises. This long recognized phenomenon has repeatedly caught the attention of thinkers across a variety of fields. Game theory has, through stylized quantitative models, served to unfold core processes governing the nature of cooperation on public goods. While caught between oversimplification and intractability, research is pushing to understand cooperation in complex systems. Large organizational units, such as whole communities, are typically subdivided into a multiple of different localized groups between which individuals may transfer. Although the group structure of such heterogeneous units is known to be important to the success of cooperation, knowledge on how group structures dynamically unfold and develop jointly with cooperative efforts is limited. Public economist Charles Tiebout suggested in 1956 that foot voting as an inter-group migration behavior could constitute a powerful bottom-up solution to the free-rider problem in local governance, as he believed that large communities would self-organize into an optimal type of group-structure. We apply evolutionary game-theory to social group-formation, and find that foot voting spontaneously emerges in large self-organized, public-goods communities. In turn, the emergence of foot voting makes way for cooperation to develop in non-cooperative communities which transform into highly cooperative group-structured societies. As such, the Tiebout hypothesis gets support in evolutionary game theory, and at the same time is revealed as an example of a wider concept, as it builds on a sorting principle that appears inevitable and that may represent a general mechanism for triggering invasion of altruism, potentially at many, and much more basic, levels of social and biological organization

Neoadjuvant therapy for breast cancer

Objective: To evaluate the frequency of neoadjuvant therapy (NT) in women with stage I–III breast cancer in Italy and whether it is influenced by biological characteristics, screening history, and geographic area. Methods: Data from the High Resolution Study conducted in 7 Italian cancer registries were used; they are a representative sample of incident cancers in the study period (2009–2013). Included were 3546 women aged &lt;85 years (groups &lt;50, 50–69, 70–64, and 75+) with stage I–III breast cancer at diagnosis who underwent surgery. Women were classified as receiving NT if they received chemotherapy, target therapy, and/or hormone therapy before the first surgical treatment. Logistic models were built to test the association with biological and contextual variables. Results: Only 8.2% of women (290 cases) underwent NT; the treatment decreases with increasing age (14.5% in age &lt;50 and 2.2% in age 75+), is more frequent in women with negative receptors (14.8%), HER2-positive (15.7%), and triple-negative (15.6%). The multivariable analysis showed the probability of receiving NT is higher in stage III (odds ratio [OR] 3.83; 95% confidence interval [CI] 2.83–5.18), luminal B (OR 1.87; 95% CI 1.27–2.76), triple-negatives (OR 1.88; 95% CI 1.15–3.08), and in symptomatic cancers (OR 1.98; 95% CI 1.13–3.48). Use of NT varied among geographic areas: Reggio Emilia had the highest rates (OR 2.29; 95% CI 1.37–3.82) while Palermo had the lowest (OR 0.41; 95% CI 0.24–0.68). Conclusions: The use of NT in Italy is limited and variable. There are no signs of greater use in hospitals with more advanced care