Real-Time Correlates of Phonological Quantity Reveal Unity of Tonal and Non-Tonal Languages

Discrete phonological phenomena form our conscious experience of language: continuous changes in pitch appear as distinct tones to the speakers of tone languages, whereas the speakers of quantity languages experience duration categorically. The categorical nature of our linguistic experience is directly reflected in the traditionally clear-cut linguistic classification of languages into tonal or non-tonal. However, some evidence suggests that duration and pitch are fundamentally interconnected and co-vary in signaling word meaning in non-tonal languages as well. We show that pitch information affects real-time language processing in a (non-tonal) quantity language. The results suggest that there is no unidirectional causal link from a genetically-based perceptual sensitivity towards pitch information to the appearance of a tone language. They further suggest that the contrastive categories tone and quantity may be based on simultaneously co-varying properties of the speech signal and the processing system, even though the conscious experience of the speakers may highlight only one discrete variable at a time.     

Monitoring the European pine sawfly with pheromone traps in maturing Scots pine stands

Abstract

• 1 During 1989–93, field studies were conducted in Finland to develop a method based on pheromone traps to monitor and forecast population levels of the European pine sawfly (Neodiprion sertifer Geoffr.) and tree defoliation.
• 2 Three traps per site were baited with 100 µg of the N. sertifer sex pheromone, the acetate ester of (2S,3S,7S)‐3,7‐dimethyl‐2‐pentadecanol (diprionol), in maturing pine stands in southern and central Finland. In addition, three different dosages (1, 10 and 100 µg) of the pheromone were tested in 1991–92.
• 3 The highest number of males was observed in traps baited with the highest dose. On average, there was a 10‐fold increase in trap catch between lure doses.
• 4 Density of overwintering eggs was used to evaluate the effectiveness of pheromone traps in predicting sawfly populations. The proportion of healthy overwintering eggs was determined each year. A model based on the number of current shoots on sample trees, diameter at breast height and tree height was formulated to estimate eggs per hectare.
• 5 Linear regression analysis produced high coefficients of determination between number of males in traps and density of total eggs in the subsequent generation, when populations were at peak densities. The relationships were not significant for low population densities. The results indicate a risk of moderate defoliation when the seasonal trap catch is 800–1000 males per trap or higher.

     

DNPTrapper: an assembly editing tool for finishing and analysis of complex repeat regions

Background  

Many genome projects are left unfinished due to complex, repeated regions. Finishing is the most time consuming step in sequencing and current finishing tools are not designed with particular attention to the repeat problem.     

Evolution of migration in a metapopulation

In this paper a general deterministic discrete-time metapopulation model with a finite number of habitat patches is analysed within the framework of adaptive dynamics. We study a general model and prove analytically that (i) if the resident populations state is a fixed point, then the resident strategy with no migration is an evolutionarily stable strategy, (ii) a mutant population with no migration can invade any resident population in a fixed point state, (iii) in the uniform migration case the strategy not to migrate is attractive under small mutational steps so that selection favours low migration. Some of these results have been previously observed in simulations, but here they are proved analytically in a general case. If the resident population is in a two-cyclic orbit, then the situation is different. In the uniform migration case the invasion behaviour depends both on the type of the residents attractor and the survival probability during migration. If the survival probability during migration is low, then the system evolves towards low migration. If the survival probability is high enough, then evolutionary branching can happen and the system evolves to a situation with several coexisting types. In the case of out-of-phase attractor, evolutionary branching can happen with significantly lower survival probabilities than in the in-phase attractor case. Most results in the two-cyclic case are obtained by numerical simulations. Also, when migration is not uniform we observe in numerical simulations in the two-cyclic orbit case selection for low migration or evolutionary branching depending on the survival probability during migration.     

Chemical factors affecting the brown-rot decay resistance of Scots pine heartwood

The cell wall chemistry (amount of hemicellulose, f-cellulose, and total lignin) and the concentration of extractives (total acetone-soluble extractives, resin acids, pinosylvins and the total phenolics quantified as tannin acid equivalents) were studied in brown-rot resistant and susceptible juvenile heartwood of Scots pine (Pinus sylvestris L.). The study material consisted of a total of 18 trees from two 34-year-old progeny trials at Korpilahti and Kerimäki. The trees were selected from among 783 trees whose decay rate had previously been screened in a laboratory test using a brown-rot fungus, Coniophora puteana. Samples from neither location showed any significant difference in the concentration (mg/cm³) of hemicellulose, f-cellulose and total lignin between the decay resistant and susceptible trees. At both locations only the concentration of total phenolics was higher in the decay-resistant heartwood than in the decay-susceptible heartwood. At Korpilahti, the amount of acetone-soluble extractives and the concentration of pinosylvin and its derivatives were higher in the resistant than in the susceptible trees.     

Proliferation and differentiation of bovine type A spermatogonia during long-term culture

The present study was aimed at developing a method for long-term culture of bovine type A spermatogonia. Testes from 5-mo-old calves were used, and pure populations of type A spermatogonia were isolated. Cells were cultured in minimal essential medium (MEM) or KSOM (potassium-rich medium prepared according to the simplex optimization method) and different concentrations of fetal calf serum (FCS) for 2-4 wk at 32 degrees C or 37 degrees C. Culture in MEM resulted in more viable cells and more proliferation than culture in KSOM, and better results were obtained at 37 degrees C than at 32 degrees C. After 1 wk of culture in the absence of serum, only 20% of the cells were alive. However, in the presence of 2.5% FCS, approximately 80% of cells were alive and proliferating. Higher concentrations of FCS only enhanced numbers of somatic cells. In long-term culture, spermatogonia continued to proliferate, and eventually, type A spermatogonial colonies were formed. The majority of colonies consisted mostly of groups of cells connected by intercellular bridges. Most of the cells in these colonies underwent differentiation because they were c-kit positive, and ultimately, cells with morphological and molecular characteristics of spermatocytes and spermatids were formed. Occasionally, large round colonies consisting of single, c-kit-negative, type A spermatogonia (presumably spermatogonial stem cells) were observed. For the first time to our knowledge, a method has been developed to allow proliferation and differentiation of highly purified type A spermatogonia, including spermatogonial stem cells during long-term culture.     

Intercellular organelle traffic through cytoplasmic bridges in early spermatids of the rat: mechanisms of haploid gene product sharing

Stable cytoplasmic bridges (or ring canals) connecting the clone of spermatids are assumed to facilitate the sharing of haploid gene products and synchronous development of the cells. We have visualized these cytoplasmic bridges under phase-contrast optics and recorded the sharing of cytoplasmic material between the spermatids by a digital time-lapse imaging system ex vivo. A multitude of small (ca. 0.5 microm) granules were seen to move continuously over the bridges, but only 28% of those entering the bridge were actually transported into other cell. The average speed of the granules decreased significantly during the passage. Immunocytochemistry revealed that some of the shared granules contained haploid cell-specific gene product TRA54. We also demonstrate the novel function for the Golgi complex in acrosome system formation by showing that TRA54 is processed in Golgi complex and is transported into acrosome system of neighboring spermatid. In addition, we propose an intercellular transport function for the male germ cell-specific organelle chromatoid body. This mRNA containing organelle, ca. 1.8 microm in diameter, was demonstrated to go over the cytoplasmic bridge from one spermatid to another. Microtubule inhibitors prevented all organelle movements through the bridges and caused a disintegration of the chromatoid body. This is the first direct demonstration of an organelle traffic through cytoplasmic bridges in mammalian spermatogenesis. Golgi-derived haploid gene products are shared between spermatids, and an active involvement of the chromatoid body in intercellular material transport between round spermatids is proposed.     

Evolutionary branching of dispersal strategies in structured metapopulations

 Dispersal polymorphism and evolutionary branching of dispersal strategies has been found in several metapopulation models. The mechanism behind those findings has been temporal variation caused by cyclic or chaotic local dynamics, or temporally and spatially varying carrying capacities. We present a new mechanism: spatial heterogeneity in the sense of different patch types with sufficient proportions, and temporal variation caused by catastrophes. The model where this occurs is a generalization of the model by Gyllenberg and Metz (2001). Their model is a size-structured metapopulation model with infinitely many identical patches. We present a generalized version of their metapopulation model allowing for different types of patches. In structured population models, defining and computing fitness in polymorphic situations is, in general, difficult. We present an efficient method, which can be applied also to other structured population or metapopulation models. Received: 6 March 2001 / Revised version: 12 February 2002 / Published online: 17 July 2002     

Evolutionary suicide and evolution of dispersal in structured metapopulations

 We study the evolution of dispersal in a structured metapopulation model. The metapopulation consists of a large (infinite) number of local populations living in patches of habitable environment. Dispersal between patches is modelled by a disperser pool and individuals in transit between patches are exposed to a risk of mortality. Occasionally, local catastrophes eradicate a local population: all individuals in the affected patch die, yet the patch remains habitable. We prove that, in the absence of catastrophes, the strategy not to migrate is evolutionarily stable. Under a given set of environmental conditions, a metapopulation may be viable and yet selection may favor dispersal rates that drive the metapopulation to extinction. This phenomenon is known as evolutionary suicide. We show that in our model evolutionary suicide can occur for catastrophe rates that increase with decreasing local population size. Evolutionary suicide can also happen for constant catastrophe rates, if local growth within patches shows an Allee effect. We study the evolutionary bifurcation towards evolutionary suicide and show that a discontinuous transition to extinction is a necessary condition for evolutionary suicide to occur. In other words, if population size smoothly approaches zero at a boundary of viability in parameter space, this boundary is evolutionarily repelling and no suicide can occur. Received: 10 November 2000 / Revised version: 13 February 2002 / Published online: 17 July 2002