Spatial pattern as an adaptive phenotype

Spatial patterns are common in nature across a broad range of scales, from body coloration patterns of animals to clustering of vegetation. The ultimate causes of these patterns are viewed very differently depending on whether they are traits of individuals or properties of aggregations. Traits of individuals are usually considered to be shaped directly by selection, while patterns of aggregation are typically viewed as incidental side effects of some other underlying processes or environmental heterogeneity. However, given the powerful influence that spatial structure can have on the susceptibility of a population to a dispersal-limited predator or pathogen, it may be useful to consider the possibility that spatial structure per se could serve as an anti-enemy adaptive phenotype. This group-level trait could evolve only if selection at the individual level does not overwhelm higher-level selection. To explore the plausibility of spatial structure as an adaptive phenotype, I consider the specific case of a spatially-explicit, evolutionary host–pathogen model. This model demonstrates the evolution of reproductive restraint, resulting in a low-density, poorly-connected landscape of host clusters that is resistant to the spread of the pathogen. Reimagining spatial structure as an adaptive phenotype may generate new insights of both theoretical and practical significance.     

Abstract biological systems as sequential machines

It is shown that a rather close relationship exists between the (ℳ,ℛ)-systems, defined previously as prototypes of abstract biological systems, and the sequential machines which have been studied by various authors. The theory of sequential machines is reformulated in a way suitable for its application to the study of the intertransformability of (ℳ,ℛ)-systems as a result of environmental alteration. The important concept of strong connectedness is most useful in this direction, and is used to derive a number of results on intertransformability. Some suggestions are made for further studies along these lines.     

Spatial correlograms of soil cover as an indicator of landscape heterogeneity

Soil cover, which is one of the most informative and integrative landscape factors, can be used for the analysis of landscape patterns. We studied the spatial autocorrelation (Moran's I) of raster format soil maps (1:10,000; 10 m pixel size) in 35 study areas representing all landscape regions in Estonia. The carbonate concentration of soils, volumetric soil moisture (%) and the depth of the groundwater table were taken into consideration in compiling a scale of contrast of 17 soil groups. We introduce a simple characteristic based on spatial correlograms: a half-value distance lag, h_I = 0.5—a distance where Moran's I drops below 0.5. Spatial autocorrelation decreased very rapidly in the case of heights with a very heterogeneous landscape composition, showing low values of h_I = 0.5 (<100 m in all 6 study areas). In uplands and depressions, the spatial autocorrelation also decreased relatively rapidly (h_I = 0.5 < 200 m). In most of the plains, coastal lowlands, sea islands and inland paludified lowlands, the values of Moran's I did decrease slowly with increasing lag, being >200 m in all forest and bog areas with complex topographical conditions due to the variety of glacial landforms and peatlands. All of the eight FRAGSTATS landscape metrics studied demonstrated significant correlations with h_I = 0.5, whereas five of them – Contrast Weighted Edge Density (CWED); Percentage of Like Adjacencies (PLADJ), Edge Density (ED), Patch Density (PD) and Mean Patch Area Distribution (AREA_MN) – had Spearman Rank Order Correlation values higher than 0.8. Landscapes with high ED, PD, and CWED values have a low autocorrelation: PD, ED, and CWED correlated negatively with h_I = 0.5. PD, ED, and CWED decreased and PLADJ increased with the power-law relationship with increasing h_I = 0.5. Spatial autocorrelation is lower in landscapes with complex structure and high contrast. The positive relationship with PLADJ indicates the same. Thus, spatial correlograms of potential landscape structure based on soil cover analysis can be used for the characterization of human-influenced landscape (land use) structure.     

Spatial signal repression as an additional role of Sprouty2 protein variants

Sprouty2 (Spry2) is a prominent member of a protein family with crucial functions in the modulation of signal transduction. One of its main actions is the repression of mitogen-activated protein kinase (MAPK) pathway in response to growth factor-induced signalling. A common single nucleotide polymorphism within the Spry2 gene creates two protein variants where a proline adjacent to the serine rich domain is converted to an additional serine. Both protein variants perform similar functions although their efficiency in fulfilling these tasks varies. In this report, we used biochemical fractionation methods as well as confocal microscopy to analyse quantitative and qualitative differences in the distribution of Spry2 variants. We found that Spry2 proteins localize not solely to the plasma membrane, but also to other membrane engulfed compartments like for example the Golgi apparatus. In these less dense organelles, predominantly slower migrating forms reside indicating that posttranslational modification contributes to the distribution profile of Spry2. However there is no significant difference in the distribution of the two variants. Additionally, we found that Spry2 could be found exclusively in membrane fractions irrespective of the mitogen availability and the phosphorylation status. Considering the interference of extracellular signal-regulated kinase (ERK) activation in the cytoplasm, both Spry2 variants inhibited the levels of phosphorylated ERK (pERK) significantly to a similar extent. In contrast, the induction profiles of pERK levels were completely different in the nuclei. Again, both Spry2 variants diminished the levels of pERK. While the proline variant lowered the activation throughout the observation period, the serine variant failed to interfere with immediate accumulation of nuclear pERK levels, but the signal duration was shortened. Since the extent of the pERK inhibition in the nuclei was drastically more pronounced than in the cytoplasm, we conclude that Spry2 – in addition to its known functions as a repressor of general ERK phosphorylation – functions as a spatial repressor of nucleic ERK activation. Accordingly, a dominant negative version of Spry2 was only able to enhance the pERK levels of serum-deprived cells in the cytosol, while in the nucleus the intensity of the pERK signal in response to serum addition was significantly increased.     

Reasoning with an Attitude: Johannes Fabian's Ecstatic Trek

Out of Our Minds: Reason and Madness in the Exploration of Central Africa. Johannes Fabian. Berkeley: University of California Press, 2000. 320 pp.
Anthropology with an Attitude: Critical Essays. Johannes Fabian. Stanford: Stanford University Press, 2001. 356 pp.     

Spatial Variability in Biodegradation Rates as Evidenced by Methane Production from an Aquifer

Accurate predictions of carbon and energy cycling rates in the environment depend on sampling frequencies and on the spatial variability associated with biological activities. We examined the variability associated with anaerobic biodegradation rates at two sites in an alluvial sand aquifer polluted by municipal landfill leachate. In situ rates of methane production were measured for almost a year, using anaerobic wells installed at two sites. Methane production ranged from 0 to 560 μmol · m^-2 · day^-1 at one site (A), while a range of 0 to 120,000 μmol · m^-2 · day^-1 was measured at site B. The mean and standard deviations associated with methane production at site A were 17 and 57 μmol · m^-2 · day^-1, respectively. The comparable summary statistics for site B were 2,000 and 9,900 μmol · m^-2 · day^-1. The coefficients of variation at sites A and B were 340 and 490%, respectively. Despite these differences, the two sites had similar seasonal trends, with the maximal rate of methane production occurring in summer. However, the relative variability associated with the seasonal rates changed very little. Our results suggest that (i) two spatially distinct sites exist in the aquifer, (ii) methanogenesis is a highly variable process, (iii) the coefficient of variation varied little with the rate of methane production, and (iv) in situ anaerobic biodegradation rates are lognormally distributed.     

Herbivore-Alga Interaction Strength Influences Spatial Heterogeneity in a Kelp-Dominated Intertidal Community

There is a general consensus that marine herbivores can affect algal species composition and abundance, but little empirical work exists on the role of herbivores as modifiers of the spatial structure of resource assemblages. Here, we test the consumption/bulldozing effects of the molluscan grazer Enoplochiton niger and its influence on the spatial structure of a low intertidal community dominated by the bull kelp Durvillaea antarctica and the kelp Lessonia spicata. Through field experiments conducted at a rocky intertidal shore in north-central Chile (~30°-32°S), the edge of the grazer and algae geographic distributions, we estimated the strength and variability of consumptive effects of the grazer on different functional group of algae. We also used data from abundance field surveys to evaluate spatial co-occurrence patterns of the study species. Exclusion-enclosure experiments showed that E. niger maintained primary space available by preventing algal colonization, even of large brown algae species. The grazing activity of E. niger also reduced spatial heterogeneity of the ephemeral algal species, increasing bare space availability and variability through time in similar ways to those observed for the collective effect with other grazers. Overall, our result suggests that E. niger can be considered an important modifier of the spatial structure of the large brown algae-dominated community. Effects of E. niger on resource variability seem to be directly related to its foraging patterns, large body size, and population densities, which are all relevant factors for management and conservation of the large brown algae community. Our study thus highlights the importance of considering functional roles and identity of generalist consumers on spatial structure of the entire landscape.     

Abstract biological systems as sequential machines: Behavioral reversibility

Rosen’s identification of abstract biological systems, called (M,R)-systems, with sequential machines is formally characterized. It is then shown that the determination of environmental alterations of (M,R)-systems from a knowledge of the response sequence and the structure of the system, which we call behavioral reversibility, can be interpreted as information-losslessness of sequential machines. Applying this relationship, necessary conditions for behavioral reversibility are derived. It is further shown that, similar to Rosen’s work on structural reversibility, (M,R)-systems are behaviorally reversible only if the number of physically realizable mappings are restricted.     

A New Auditory Multi-Class Brain-Computer Interface Paradigm: Spatial Hearing as an Informative Cue

Most P300-based brain-computer interface (BCI) approaches use the visual modality for stimulation. For use with patients suffering from amyotrophic lateral sclerosis (ALS) this might not be the preferable choice because of sight deterioration. Moreover, using a modality different from the visual one minimizes interference with possible visual feedback. Therefore, a multi-class BCI paradigm is proposed that uses spatially distributed, auditory cues. Ten healthy subjects participated in an offline oddball task with the spatial location of the stimuli being a discriminating cue. Experiments were done in free field, with an individual speaker for each location. Different inter-stimulus intervals of 1000 ms, 300 ms and 175 ms were tested. With averaging over multiple repetitions, selection scores went over 90% for most conditions, i.e., in over 90% of the trials the correct location was selected. One subject reached a 100% correct score. Corresponding information transfer rates were high, up to an average score of 17.39 bits/minute for the 175 ms condition (best subject 25.20 bits/minute). When presenting the stimuli through a single speaker, thus effectively canceling the spatial properties of the cue, selection scores went down below 70% for most subjects. We conclude that the proposed spatial auditory paradigm is successful for healthy subjects and shows promising results that may lead to a fast BCI that solely relies on the auditory sense.     

Spatial modelling of agrarian subsidy payments as an input for evaluating changes of ecosystem services

The only constant in landscapes is change. Among other influences, such as climate change, these changes are driven by political decisions affecting ecosystem services. The overall research objective is to define how the European Union's political strategies implemented through Rural Development Programmes and the Common Agricultural Policy might influence or change ecosystem goods and services in the future. This paper aims at outlining the research framework and especially focuses on spatially explicit modelling the distribution of subsidy cash flows on farm and parcel level. Experiments with changing political strategies and incentive payments were carried out in the Mondsee catchment (Austria) using Geographic Information Systems (GIS). The results were visualised and show the dominant (inter-)national and regional funding programmes of this area. They further display the likely effects of changing political strategies on the monetary value of certain parcels and the overall farm–parcel balance. The validation of an aggregated set of funding measures reveals 15% deviation between the model framework and real subsidy payments. This approach is suitable for both (a) estimating the impact of changed funding strategies at EU level and (b) supporting farmers in identifying the best economic income sources on parcel and farm level. Embedded in the overall research objective the results constitute the basis for opening a discussion on how ecosystem services might change with political intervention strategies in rural areas and resulting landscape changes in the future.     

Strength of winter leaf redness as an indicator of stress vulnerable individuals in Pistacia lentiscus

Leaf anthocyanins are believed to afford protection against photoinhibition, yet the dependence of protection on actual anthocyanin concentrations has not been investigated. To that aim, non-invasive optical methods (spectral reflectance and chlorophyll fluorescence) were used to assess the levels of anthocyanins and chlorophylls as well as photosystem II photochemical efficiency in hundreds of leaves from the mastic tree (Pistacia lentiscus), which displays in the field a continuum of leaf tints during winter from fully green to fully red. Contrary to expectations based on the photoprotective hypothesis, the strength of leaf redness was positively correlated to the extent of mid-winter chronic photoinhibition and negatively correlated to leaf chlorophyll contents. Hence, a photoprotective role for anthocyanins is not substantiated. Instead, we argue that winter leaf redness may be used reliably, quickly and non-invasively to locate vulnerable individuals in the field.     

A Reciprocal Model of Face Recognition and Autistic Traits: Evidence from an Individual Differences Perspective

Although not a core symptom of the disorder, individuals with autism often exhibit selective impairments in their face processing abilities. Importantly, the reciprocal connection between autistic traits and face perception has rarely been examined within the typically developing population. In this study, university participants from the social sciences, physical sciences, and humanities completed a battery of measures that assessed face, object and emotion recognition abilities, general perceptual-cognitive style, and sub-clinical autistic traits (the Autism Quotient (AQ)). We employed separate hierarchical multiple regression analyses to evaluate which factors could predict face recognition scores and AQ scores. Gender, object recognition performance, and AQ scores predicted face recognition behaviour. Specifically, males, individuals with more autistic traits, and those with lower object recognition scores performed more poorly on the face recognition test. Conversely, university major, gender and face recognition performance reliably predicted AQ scores. Science majors, males, and individuals with poor face recognition skills showed more autistic-like traits. These results suggest that the broader autism phenotype is associated with lower face recognition abilities, even among typically developing individuals.     

Spatial segregation in the reproductive activity of Neotropical fish species as an indicator of the migratory trait

This study focused on the distribution of fish with high reproductive activity along a basin, using a 430 km stretch of the Cuiabá River in Brazil as a model. The main objective of this study was to identify those fish that migrate long distances for reproduction, among all the basin species. Thus, a set of working criteria are proposed to classify species according to their reproductive behaviour (i.e., reproductive activity and distribution). Samplings were performed in the Cuiabá River basin, encompassing several environments (river, channels and lakes) during the reproductive periods (between October and February), from 2000 to 2004. Species occurrence (presence and absence – proxy of distribution) across the basin and index of reproductive activity values were used as criteria to identify the species that perform long-distance longitudinal migrations for reproduction. The study confirmed the classification of long-distance longitudinal migration species; nonetheless, some species were not classified as described in the literature. The proposed sequential criteria have proven to be effective in the classification of long-distance longitudinal migrations species and certainly contribute to filling some existing knowledge gaps of reproductive traits. This classification is of fundamental importance in planning new dam projects, in decision making and in the development of management and conservation actions for the ichthyofauna.     

Spatial heterogeneity in genetic relatedness among house sparrows along an urban-rural gradient as revealed by individual-based analysis

Understanding factors that shape patterns of kinship in sedentary species is important for evolutionary ecologists as well as conservation biologists. Yet, how patterns of relatedness are hierarchically structured in space remains poorly known, even in common species. Here, we use information from 16 polymorphic microsatellite DNA markers to study how small-scale kinship structure varies among house sparrows (Passer domesticus) along an urban-rural gradient. Average levels of relatedness were higher among urban individuals than among individuals from rural areas, suggesting lower rates of dispersal in more built-up habitats. Comparison of observed levels of relatedness with simulated distributions of known kinship values showed that central urban individuals had the highest proportion of closely related conspecifics in their immediate neighbourhood. Spatial auto-correlograms supported this small-scale genetic structure and further indicated stronger effects of genetic drift and/or limited dispersal in urban populations. Results of this study underscore the importance of individual-level analyses as a complementary approach to traditional population-level analyses when studying genetic population structure over small spatial scales.     

Abstract biological systems as sequential machines II: Strong connectedness and reversibility

It was previously shown that the abstract biological systems called. (ℳ, ℛ)-systems could be regarded formally as sequential machines, and that when this was done, the reversibility of environmentally induced structural changes in these systems was closely related to the strong connectedness of the corresponding machines. In the present work it is shown that the sequential machines arising in this way are characterized by the property that the size of the input alphabet is very small compared with the size of the set of states of the machine. It is further shown that machines with this property almost always fail to be strongly connected. Therefore, it follows that one of the following alternatives holds: either most environmentally induced structural alterations are not environmentally reversible, or else many mappings in the category from which the (ℳ, ℛ)-systems are formed must not be physically realizable.