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

Effects of BRCA2 deficiency on telomere recombination in non-ALT and ALT cells

This article has been made available through the Brunel Open Access Publishing Fund - Copyright @ 2011 Sapir et al.Background: Recent studies suggest that BRCA2 affects telomere maintenance. Interestingly, anti cancer treatments that involve BRCA2 and telomerase individually are currently being explored. In the light of the above recent studies their combinatorial targeting may be justified in the development of future treatments. In order to investigate effects of BRCA2 that can be explored for this combinatorial targeting we focused on the analysis of recombination rates at telomeres by monitoring T-SCEs (Telomere Sister Chromatid Exchanges). Results: We observed a significant increase in T-SCE frequencies in four BRCA2 defective human cell lines thus suggesting that BRCA2 suppresses recombination at telomeres. To test this hypothesis further we analyzed T-SCE frequencies in a set of Chinese hamster cell lines with or without functional BRCA2. Our results indicate that introduction of functional BRCA2 normalizes frequencies of T-SCEs thus supporting the notion that BRCA2 suppresses recombination at telomeres. Given that ALT (Alternative Lengthening of Telomeres) positive cells maintain telomeres by recombination we investigated the effect of BRCA2 depletion in these cells. Our results show that this depletion causes a dramatic reduction in T-SCE frequencies in ALT positive cells, but not in non-ALT cells. Conclusion: BRCA2 suppresses recombination at telomeres in cells that maintain them by conventional mechanisms. Furthermore, BRCA2 depletion in ALT positive cells reduces high levels of T-SCEs normally found in these cells. Our results could be potentially important for refining telomerase-based anti-cancer therapies.This work is supported in part by grants from European Commission RISC-RAD contract FI6RCT2003-508842 and British Counci

Soaring migrants flexibly respond to sea-breeze in a migratory bottleneck: using first derivatives to identify behavioural adjustments over time.

Millions of birds travel every year between Europe and Africa detouring ecological barriers and funnelling through migratory corridors where they face variable weather conditions. Little is known regarding the response of migrating birds to mesoscale meteorological processes during flight. Specifically, sea-breeze has a daily cycle that may directly influence the flight of diurnal migrants. We collected radar tracks of soaring migrants using modified weather radar in Latrun, central Israel, in 7 autumns between 2005 and 2016. We investigated how migrating soaring birds adjusted their flight speed and direction under the effects of daily sea-breeze circulation. We analysed the effects of wind on bird groundspeed, airspeed and the lateral component of the airspeed as a function of time of day using Generalized Additive Mixed Models. To identify when birds adjusted their response to the wind over time, we estimated first derivatives. Using data collected during a total of 148 days, we characterised the diel dynamics of horizontal wind flow relative to the migration goal, finding a consistent rotational movement of the wind blowing towards the East (morning) and to the South-East (late afternoon), with highest crosswind speed around mid-day and increasing tailwinds towards late afternoon. Airspeed of radar detected birds decreased consistently with increasing tailwind and decreasing crosswinds from early afternoon, resulting in rather stable groundspeed of 16-17 m/s. In addition, birds fully compensated for lateral drift when crosswinds were at their maximum and slightly drifted with the wind when crosswinds decreased and tailwinds became more intense. Using a simple and broadly applicable statistical method, we studied how wind influences bird flight through speed adjustments over time, providing new insights regarding the flexible behavioural responses of soaring birds to wind conditions. These adjustments allowed the birds to compensate for lateral drift under crosswind and reduced their airspeed under tailwind. Our work enhances our understanding of how migrating birds respond to changing wind conditions during their long-distance journeys through migratory corridors

Body mass and geographic distribution determined the evolution of the wing flight-feather molt strategy in the Neornithes lineage

The evolutionary history of many organisms is characterized by major changes in morphology and distribution. Specifically, alterations of body mass and geographic distribution may profoundly influence organismal life-history traits. Here, we reconstructed the evolutionary history of flight-feather molt strategy using data from 1,808 Neornithes species. Our analysis suggests that the ancestral molt strategy of first-year birds was partial or entirely absent, and that complete wing flight-feather molt in first-year birds first evolved in the late Eocene and Oligocene (25–40 Ma), at least 30 Myr after birds first evolved. Complete flight-feather molt occurred mainly at equatorial latitudes and in relatively low body mass species, following a diversification of body mass within the lineage. We conclude that both body mass and geographic distribution shaped the evolution of molt strategies and propose that the evolutionary transition towards complete juvenile molt in the Neornithes is a novel, relatively late adaptation

Seasonal dynamics of native and invasive Halophila stipulacea populations—A case study from the northern Gulf of Aqaba and the eastern Mediterranean Sea

No embargo required, pre-print. Full version requires 24 month embarg

Correlation Differences in Heartbeat Fluctuations During Rest and Exercise

We study the heartbeat activity of healthy individuals at rest and during exercise. We focus on correlation properties of the intervals formed by successive peaks in the pulse wave and find significant scaling differences between rest and exercise. For exercise the interval series is anticorrelated at short time scales and correlated at intermediate time scales, while for rest we observe the opposite crossover pattern -- from strong correlations in the short-time regime to weaker correlations at larger scales. We suggest a physiologically motivated stochastic scenario to explain the scaling differences between rest and exercise and the observed crossover patterns.Comment: 4 pages, 4 figure

Differences in flowering sex ratios between native and invasive populations of the seagrass Halophila stipulacea

Deviations from the 1:1 sex ratio are common in dioecious plants. The tropical seagrass Halophila stipulacea is among an extremely rare group of dioecious plants which is widely recognized as female-biased. Here we report on differences in sex ratios between native (Eilat, northern Red Sea) and invasive (Cyprus, Mediterranean Sea) populations. While H. stipulacea populations were female-biased in the native region, invasive populations were either male- or female-biased. The existence of both sexes simultaneously in the Mediterranean invasive population, might help its ongoing expansion in the Mediterranean, thereby threatening local seagrasses species

Newly identified nematodes from Mono Lake exhibit extreme arsenic resistance

Extremophiles have much to reveal about the biology of resilience, yet their study is limited by sampling and culturing difficulties [1, 2, 3]. The broad success and small size of nematodes make them advantageous for tackling these problems [4, 5, 6]. We investigated the arsenic-rich, alkaline, and hypersaline Mono Lake (CA, US) [7, 8, 9] for extremophile nematodes. Though Mono Lake has previously been described to contain only two animal species (brine shrimp and alkali flies) in its water and sediments [10], we report the discovery of eight nematode species from the lake, including microbe grazers, parasites, and predators. Thus, nematodes are the dominant animals of Mono Lake in species richness. Phylogenetic analysis suggests that the nematodes originated from multiple colonization events, which is striking, given the young history of extreme conditions at Mono Lake [7, 11]. One species, Auanema sp., is new, culturable, and survives 500 times the human lethal dose of arsenic. Comparisons to two non-extremophile sister species [12] reveal that arsenic resistance is a common feature of the genus and a preadaptive trait that likely allowed Auanema to inhabit Mono Lake. This preadaptation may be partly explained by a variant in the gene dbt-1 shared with some Caenorhabditis elegans natural populations and known to confer arsenic resistance [13]. Our findings expand Mono Lake’s ecosystem from two known animal species to ten, and they provide a new system for studying arsenic resistance. The dominance of nematodes in Mono Lake and other extreme environments and our findings of preadaptation to arsenic raise the intriguing possibility that nematodes are widely pre-adapted to be extremophiles

The Impact of COVID-19 on Well-Being: A Systems Approach

In addition to its health and economic implications, COVID-19 has a widespread effect on social relations, stress, livelihood, and on the environment. However, analyses of the effects of COVID-19 tend to focus on the health and economic implications of the pandemic. In recent years well-being is increasingly promoted as a measure to assess the state of countries and citizens, taking into account a broad set of factors such as social relations, the environment, health, and livelihood. Previous work at IIASA has produced a national well-being map, in which the variables that affect both current and future well-being were spelled out, as well as the relations between them. In the current study, we utilize the IIASA national well-being map as a basis for analyzing the effects of COVID-19 on social well-being, focusing on Israel as a case study. Thus, while the indicators used are based on the OECD well-being indicators, they are contextualized to account for both the setting and for the focus on social well-being of current generations (those that are most likely to be affected by COVID-19). However, the approach we suggest can be useful for other cases, and the results may shed light on the COVID-19 effects elsewhere. To this end, we first identify the direct effects of COVID-19 and the measures undertaken to mitigate the immediate health effects on the variables included in the social well-being map, a modified version of the original national well-being map. These served to identify both the primary and secondary effects of COVID-19. By relating these primary and secondary effects on the variables that affect social well-being, we can identify how COVID-19 affects current social well-being, differentiating these effects by timing. Then we show that there are synergic effects that will lead to long-term implications, also after the pandemic is brought under control. COVID-19 does not affect all population groups equally. We find that the effects of COVID-19 on employment serve as the stratifying variable that differentiates the effects. Hence, we analyzed the well-being effects of COVID-19 on different groups based on the effects the pandemic has had on employment. This analysis shows that while the well-being of all groups is affected, they are particularly wide and strenuous for those who lose their jobs or businesses. Therefore, job retention and mitigation of the job insecurity effects of COVID-19 are found to be of critical importance, more than income maintenance. These variables are also essential for the maintenance of trust in government, as such trust is crucial when the next wave of the pandemic erupts. However, additional measures that may mitigate the effects on other well-being indicators are also called for. Thus, it is advisable to formulate policy packages that will address the multi-dimensional effects on well-being