Correlation between the shoot-cutting behavior of the acorn weevil and the reproductive traits of host fagaceous trees

Many fagaceous species mature acorns during the second autumn after flowering and are called “2-year species.” In 2-year species of subgenus Cyclobalanopsis (genus Quercus), alternate bearing (2-year seed production cycle) is prominent, but this has not been reported for other 2-year species in the genera of Lithocarpus and Castanopsis. We tested the hypothesis that the difference in reproduction of 2-year species is linked to the weevil, Mechoris ursulus. After ovipositing on acorns, this insect cuts the shoots to which the acorns are attached. We examined the host preference of M. ursulus and reproductive traits of fagaceous 2-year species. Percentage infestation was remarkably high in the subgenus Cyclobalanopsis, whereas Lithocarpus and Castanopsis species suffered almost no damage. Furthermore, unlike Lithocarpus and Castanopsis, most of the acorn-producing shoots in subgenus Cyclobalanopsis had no current-year shoots. The clear relationship suggests that alternate bearing in subgenus Cyclobalanopsis is an adaptation to the shoot-cutting behavior of M. ursulus.     

Geometric determinants of the postrhinal egocentric spatial map

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The dependency game: Multiperson reciprocal sharing leads to stable cooperation which can evolve into group formation

In the standard model for reciprocal collaboration, the repeated prisoner's dilemma (PD), it has proved difficult to establish collaboration in larger groups, necessitating the introduction of additional mechanisms such as reputation or assortedness. The problem is corroborated because current multiperson PDs model simultaneous player action, known as a common goods situation, whereas multiperson collaboration could be easier to obtain in a PD with alternate player action, a private goods situation. Here we present such a game, called a dependency game, and show that stable collaboration can be obtained in a 255 player simulation if only players are allowed to remember three previous benefactors, so they can play advanced tit-for-tat. Furthermore, we show that such a freely collaborating population is threatened by assorted strategies, which define groups that parasitize on independent tit-for-tat players. By excluding others, these groups engage in indirect reciprocal behaviour. Our model therefore combines many hitherto separate collaboration-enhancing concepts into one game, and suggests that group formation and collaboration are two separate social phenomena.     

Relationship and genetic structure among autoecious and heteroecious populations of Cronartium pini in northern Fennoscandia

Epidemics of Scots pine blister rust, caused by Cronartium pini, have become an increasing problem in northern Finland and Sweden. The biology of the rust fungus is complex, with two different life cycle forms that cannot be morphologically distinguished, and it is unclear to what extent the two forms contribute to the epidemics. Genetic structure of fourteen populations of C. pini were investigated in Fennoscandia. Distinction between the two life cycle forms, a heteroecious and an autoecious one, was made by determining zygosity using microsatellite markers, and AFLP markers were developed to analyse population genetic relationships. The results showed that the two life cycle forms are clearly differentiated and occur in separate populations. Within the life cycle forms, geographic differentiation was evident, probably due to restricted gene flow as well as connection with different alternating hosts. The host-alternating form dominated in the epidemic regions in northern Fennoscandia. Implications for silvicultural practices are discussed.     

Tissue culture: the unrealized potential

Lack of differentiated functions of the tissue of origin in tissue culture thought to be due to dedifferentiation was shown to be due to selective overgrowth of fibroblasts. Enrichment culture techniques, (alternate animal and culture passage), designed to give the functionally differentiated cells selective advantage over the fibroblasts resulted in a large number of functionally differentiated clonal strains. Thus the dogma of dedifferentiation was destroyed. It is proposed to substitute the dedifferentiation hypothesis with the hypothesis that cells in culture accurately represent cells in vivo without the complex in vivo environment. With the development of hormonally defined media, combined with functionally differentiated clonal cell lines, the potential of tissue culture studies is greatly augmented. Hormonal responses and dependencies can be discovered in culture and the discovery of dependencies of cancer cells has led to a new rationale for therapy.     

The Bow and Cultural Complexity of the Canadian Plains

The timing and circumstances of the introduction of the bow and arrow into past North American economic and social lifeways have been sources of interest and controversy among archeologists for a very long time. Initial interpretations of the adoption of the bow and arrow generally seem to have been based on the rather straightforward assumption of functional superiority as a hunting tool. That is, the bow and arrow was simply a better instrument than the atlatl‐dart technology it replaced. 1 , 2 More recently, however, researchers exploring the effectiveness of the atlatl as a hunting tool have responded with studies that challenge the assumed universal functional superiority of the bow and arrow as a hunting device. 3 - 5 Social coercion and warfare theory presents an alternative perspective on the adoption of the bow and arrow.     

An assay to investigate factors influencing initial orientation in nocturnally fledging seabirds

The first solitary migration of juvenile birds is difficult to study because of a low juvenile survival rates and sometimes long delays in return to the breeding grounds. Consequently, little is known about this crucial life event for many bird species, in particular the sensory guidance mechanisms facilitating the first migratory journey. Initial orientation during the first migration is a key measure to investigate these mechanisms. Here, we developed an assay to measure initial orientation as flight direction upon first take‐off in nocturnally fledging juvenile seabirds. We dorsally deployed a coloured LED on juvenile birds to allow researchers to observe the vanishing bearings of individuals as they flew out to sea. Additionally, we co‐deployed either a small Neodymium magnet or glass bead (control) on top of the bird's head to investigate the use of magnetoreception, previously unexplored in this early life stage. We used this assay to observe the first flight of Manx shearwaters Puffinus puffinus and found that they did not orient towards their wintering ground straight after taking off. Further, we did not find an effect of the magnetic treatment on juveniles' flight direction, though whether this is due to the birds not using magnetoreception, other salient cues being available or a lack of motivation to orient to the migratory beeline is unclear. We were, however, able to identify wind direction and topography as drivers of first flight direction in Manx shearwaters, which fledged with wind component between a crosswind and a tailwind and directed their maiden flight towards the sea and away from the land. This novel assay will facilitate the study of the maiden flight of nocturnally fledging birds and will help advance the study of sensory guidance mechanisms underpinning migratory orientation in a wide range of taxa, including species which are traditionally challenging to study.     

基于“三生空间”的福建省城市综合承载力研究

基于“三生空间”构建城市综合承载力指标体系,分析2011—2016年福建省各设区市城市综合承载力的时空分布特征,引入耦合协调度模型和障碍度诊断对各设区市生产、生活、生态空间承载力的耦合协调度及主要制约因素进行分析。结果表明:①2011—2016年福建省各设区市城市综合承载力整体变化不大,闽东南沿海地区城市综合承载力较高,闽东北和闽西内陆地区城市综合承载力相对较低;②2011—2016年各设区市“三生空间”耦合协调度相对较低,以濒临失调和轻度失调为主;③2011—2016年各设区市城市综合承载力制约因素主要分布于生产空间和生态空间,未来应加强这两方面的发展。据此研究结果,提出加强区域协作,促进共同发展等协调福建省各设区市未来发展的对策建议。     

The role of large environmental noise in masting: General model and example from pistachio trees

Masting is synchronous, highly variable reproduction in a plant population, or synchronized boom-bust cycles of reproduction. These pulses of resources have cascading effects through ecosystems, and thus it is important to understand where they come from. How does masting happen and synchronize? In this paper, we suggest a mechanism for this. The mechanism is inspired by data from a pistachio orchard, which suggest that large environmental noise may play a crucial role in inducing masting in plant populations such as pistachio. We test this idea through development and analysis of a mathematical model of plant reproduction. We start with a very simple model, and generalize it based on the current models of plant reproduction and masting. Our results suggest that large environmental noise may indeed be a crucial part of the mechanism of masting in certain types of plant populations, including pistachio. This is a specific example of an important functional consequence of the interactions between stochasticity and nonlinearity.     

Availability and utilization of fertilizer nitrogen by rice under alternate flooding

Summary A greenhouse pot experiment with three N sources—¹⁵N-depleted ammonium sulfate, urea and sulfur-coated urea (SCU), three N levels—0, 50 and 200 ppm, and three irrigation treatments was conducted with rice in an Alamo clay soil. The irrigation treatments consisted of continuous flooding, alternating flooded-saturated and alternating flooded-drained conditions. The kinetics of NH ₄ ⁺ and NH ₄ ⁺ +NO ₃ ⁻ (available N) in soil was investigated under rice culture. Alternating flooded-drained conditions maintained a significantly lower level of available N in the soil than the other irrigation treatments. Among the N sources evaluated, urea and A/S had similar effects but SCU maintained significantly lower levels of available N in the soil during the growth of rice. Appreciable quantities of NO ₃ ⁻ accumulated during the draining periods of alternating flooded-drained treatments were apparently lost from the soil system upon reflooding.