Microelectronic detection of activity level and magnetic orientation of yellow European eel, <Emphasis Type="Italic">Anguilla anguilla</Emphasis> L., in a pond

Synopsis We studied the circadian and monthly activity, the distribution patterns, and orientation to the earths magnetic field, of yellow (non-migratory) female eels in a freshwater pond by means of microchips injected into their muscles. Detectors for microchips mounted in tubes were placed in the pond to detect if eels oriented themselves with respect to earths magnetic field. Based on the frequency of tube visits (search for shelter), the data indicated that the presence of eel in the tubes decreases gradually during the study period. We saw more activity during the night in the first months. There was a seasonal component in the orientation mechanism, with a significantly lower preference component in the summer compared to the fall. A preference for tubes oriented in a south-southwest direction (the direction of the Sargasso Sea) in fall suggests an orientation to the earths magnetic field.     

Neural connectivity and cortical substrates of cognition in hominoids

Cognitive functions and information processing recruit discrete neural systems in the cortex and white matter. We tested the idea that specific regions in the cerebrum are differentially enlarged in humans and that some of the neural reorganizational events that took place during hominoid evolution were species-specific and independent of changes in absolute brain size. We used magnetic resonance images of the living brains of 10 human and 17 ape subjects to obtain volumetric estimates of regions of interest. We parcellated the white matter in the frontal and temporal lobes into two sectors, including the white matter immediately underlying the cortex (gyral white matter) and the rest of white matter (core). We outlined the dorsal, mesial, and orbital subdivisions of the frontal lobe and analyzed the relationship between cortex and gyral white matter within each subdivision. For all regions analyzed, the observed human values are as large as expected, with the exception of the gyral white matter, which is larger than expected in humans. We found that orangutans had a relatively smaller orbital sector than any other great ape species, with no overlap in individual values. We found that the relative size of the dorsal subdivision is larger in chimpanzees than in bonobos, and that the ratio of gyral white matter to cortex stands out in Pan in comparison to Gorilla and Pongo. Individual variability, possible sex differences, and hemispheric asymmetries were present not only in humans, but in apes as well. Differences in the distribution of neural connectivity and cortical sectors were identified among great ape species that share similar absolute brain sizes. Given that these regions are part of neural systems with distinct functional attributes, we suggest that the observed differences may reflect different evolutionary pressures on regulatory mechanisms of complex cognitive functions, including social cognition.     

Paternity and kinship patterns in polyandrous moustached tamarins (Saguinus mystax)

We studied patterns of genetic relatedness and paternity in moustached tamarins, small Neotropical primates living in groups of 1–4 adult males and 1–4 adult females. Generally only one female per group breeds, mating with more than one male. Twin birth are the norm. In order to examine the genetic consequences of this mating pattern, DNA was extracted from fecal samples collected from two principal and six neighboring groups. DNA was characterized at twelve microsatellite loci (average: seven alleles/locus). We addressed the following questions: Do all adult males have mating access to the reproductive female of the group? How is paternity distributed across males in a group? Can polyandrous mating lead to multiple paternity? Are nonparental animals more closely related to the breeders than to the population mean? And, are mating partners unrelated? Breeding females mated with all nonrelated males. In at least one group the father of the older offspring did not sire the youngest infant although he was still resident in the group. We also found evidence for multiple paternity in a supposed twin pair. Yet, within each group the majority (67–100%) of infants had the same father, suggesting reproductive skew. Relatedness within groups was generally high (average R = 0.31), although both nonrelated males and females occurred, i.e., immigrations of both sexes are possible. Mating partners were never found to be related, hence inbreeding seems to be uncommon. The results suggest that while the social mating system is polyandry, paternity is often monopolized by a single male per group. Am J Phys Anthropol, 2005. © 2004 Wiley-Liss, Inc.     

Evolution of phenotypic plasticity: patterns of plasticity and the emergence of ecotypes

Phenotypic plasticity itself evolves, as does any other quantitative trait. A very different question is whether phenotypic plasticity causes evolution or is a major evolutionary mechanism. Existing models of the evolution of phenotypic plasticity cover many of the proposals in the literature about the role of phenotypic plasticity in evolution. I will extend existing models to cover adaptation to a novel environment, the appearance of ecotypes and possible covariation between phenotypic plasticity and mean trait value of ecotypes. Genetic assimilation does not sufficiently explain details of observed patterns. Phenotypic plasticity as a major mechanism for evolution--such as, invading new niches, speciation or macroevolution--has, at present, neither empirical nor model support.     

Trends in genetic diversity among European maize cultivars and their parental components during the past 50 years

It has been claimed that the system that delivers the products of plant breeding reduces the diversity of cultivated varieties leading to an increased genetic vulnerability. The main goal of our study was to monitor the temporal trends in genetic diversity over the past five decades among maize cultivars with the largest acreage in Central Europe. Our objectives were to (1) investigate how much of the genetic diversity present in important adapted open-pollinated varieties (OPVs) has been captured in the elite flint germplasm pool, (2) examine changes in the genetic diversity among the most important commercial hybrids as well as in their dent and flint parents, (3) analyze temporal changes in allele frequencies between the dent and flint parental inbreds, and (4) investigate linkage disequilibrium (LD) trends between pairs of loci within the set of parental dent and flint lines. We examined 30 individuals of five prominent OPVs from Central Europe, 85 maize hybrids of economic importance, and their dent and flint parental components with 55 SSRs. LD was significant at probability level P=0.01 for 20.2% of the SSR marker pairs in the 82 dent lines and for 17.2% in the 66 flint lines. The dent and flint heterotic groups were clearly separated already at the beginning of hybrid breeding in Central Europe. Furthermore, the genetic variation within and among varieties decreased significantly during the five decades. The five OPVs contain numerous unique alleles that were absent in the elite flint pool. Consequently, OPVs could present useful sources for broadening the genetic base of elite maize breeding germplasm.     

Sturdy cycles in the chaotic Tribolium castaneum data series

Because of the inherent discreteness of individuals, population dynamical models must be discrete variable systems. In case of strong nonlinearity, such systems interacting with noise can generate a great variety of patterns from nearly periodic behavior through complex combination of nearly periodic and chaotic patterns to noisy chaotic time series. The interaction of a population consisting of discrete individuals and demographic noise has been analyzed in laboratory population data Henson et al. (Science 294 (2001) 602; Proc. Roy. Soc. Ser. B 270 (2003) 1549). In this paper we point out that some of the cycles are fragile, i.e. they are sensitive to the discretization algorithm and to small variation of the model parameters, while others remain "sturdy" against the perturbations. We introduce a statistical algorithm to detect disjoint, nearly-periodic patterns in data series. We show that only the sturdy cycles of the discrete variable models appear in the data series significantly. Our analysis identified the quasiperiodic 11-cycle (emerging in the continuous model) to be present significantly only in one of the three experimental data series. Numerical simulations confirm that cycles can be detected only if noise is smaller than a certain critical level and population dynamics display the largest variety of nearly-periodic patterns if they are on the border of "grey" and "noisy" regions, defined in Domokos and Scheuring (J. Theor. Biol. 227 (2004) 535).     

Short human occupations in the Middle Palaeolithic level I of the Abric Romani rock-shelter (Capellades, Barcelona, Spain)

This paper presents a multidisciplinary study on the size of the occupied surfaces, provisioning strategies and behaviour planning at the Romani rock-shelter, using the Middle Palaeolithic record of the level i. This level is dated around 46.000 BP through U/Th ages. A behavioural interpretation is proposed, which emphasises the activities and the systemic value of the archaeological artefacts and structures. Occupation patterns are identified on the basis of the accumulations formed by human activities. These archaeological accumulations, consisting of artefacts and hearths, are easily defined visually as spatial units. The relationships between these accumulations, established by means of refitted remains, indicate that differences can be established between: 1) small and medium-sized occupation surfaces; 2) restricted and diversified provisioning strategies. This variability suggests that different modes of occupation are represented in the same archaeological level. The human activities reveal the generalization of fire technology. In almost all sizes of the occupation surfaces, the exploitation of vegetal resources near the Abric Romani marks the threshold of the restricted provisioning strategy. Limited use and fragmented knapping activities are recorded in the lithic assemblage. Faunal remains show differential transport. The exploitation of lithic, faunal and vegetal resources characterizes the diversified provisioning strategy. The small occupation surfaces and restricted provisioning strategies suggest short settlements in the Abric Romani. This shorter occupation model complements the longer diversified provisioning strategy recorded in both small and medium-sized occupied surfaces. The selection of precise elements for transport and the possible deferred consumption in the diversified provision strategy suggest an individual supply. In this respect, Neanderthal occupations in the Romani rock-shelter show a direct relation to: 1) hunting strategic resources; 2) high, linear mobility.     

Local coexistence of tree species and the dynamics of global distribution pattern along an environmental gradient: a simulation study

A spatially explicit tree-based model was used to demonstrate the effects of a mechanism promoting multiple-species coexistence on the development of vegetation zonation and its response to climate change. Temporal fluctuation in reproduction was incorporated as the mechanism, which facilitates the persistence of less competitive species. Four hypothetical tree species with different temperature dependencies of seed production were randomly located over a landscape represented by 2,000×40 cells. Each cell can sustain a single tree at most. A zonal distribution pattern emerged corresponding to the temperature gradient along the long axis of the landscape. When there was a temporal variation in seed production, species became distributed over a wider range than that when seed production was constant. When the whole landscape was warmed, the distribution range of each species shifted towards the cool end of the landscape. However, the migration was retarded due to competition for vacant spaces with the remnant species which had dominated the location before the warming. Temporal fluctuation in reproduction facilitated the migration because it enhanced the persistence of minority species and, thus, the invasion and establishment of new species in the area dominated by other species.     

Spatial and Temporal Distribution of Dissolved Inorganic Nutrients and Phytoplankton in Mida Creek,Kenya

The spatial and temporal distributions of dissolved inorganic nutrients were investigated between May 1996 and April 1997 in Mida Creek, a mangrove area along the north coast region of Kenya. The nutrient levels of pore water from boreholes/wells within the surrounding area of the creek were also investigated for comparison. In addition, phytoplankton distribution in Mida Creek was assessed in three stations within the creek in order to determine the structure and succession stages of the phytoplankton community and to provide an indication of the status of primary productivity of the creek. Measurements carried out within the creek revealed that the mean concentration ranges for NH₄⁺ –N, (NO ₂⁻ + NO₃⁻)−N, PO₄³⁻ −P and SiO₃²⁻ −Si were: 0.002–5.45; 0.12–5.63; 0.10–0.58 and 1.31–81.36 μM, respectively. For the case of boreholes/wells found in the surrounding area, their respective nutrient levels were found to lie in the ranges 0.4–907.0; 16.7–4897.0; 1.09–22.39 and 83.9–596.0 μM. A total of 295 species of phytoplankton belonging to 78 genera were identified with great temporal variability in abundance in all the stations sampled. The most dominant algal members in the Creek included Chaetoceros spp., Chroococcus limneticus and Oscillatoria spp. The diversity values recorded were indicative of mesotrophic conditions. The highest nutrient concentration levels within the creek were measured during the wet season as compared to dry season and this trend closely corresponded with that of the phytoplankton productivity. However, no significant variation ( p > 0.05) was found in all cases with respect to the tidal cycles. On the contrary, diurnal nutrient concentrations especially in areas with high flooding duration (>12 h) were found to be highest during the dry season as opposed to wet season for all nutrients except for SiO₃²⁻. The relatively high nutrient laden groundwater outflow into the creek water, coupled with surface runoff events during wet season, are the two main factors responsible for the elevated nutrients in the creek waters in the absence of river inflow into the creek.