Factors affecting large-scale distribution of the Bonelli’s eagle <Emphasis Type="Italic">Aquila fasciata</Emphasis> in Spain

We analyzed the environmental determinants of the regional distribution of Bonelli’s eagle (Aquila fasciata) in Spain (ca. 500,000 km²), taking into account its frequency of occurrence on UTM blocks of 50 × 50 km. We found that the distribution pattern of Bonelli’s eagle was a highly predictable phenomenon based on climate, vegetation and interspecific relationships. The proportion of sunny, anticyclonic days, per year (i.e., high levels of solar radiation) was the main environmental predictor explaining the distribution and abundance pattern of the Bonelli’s eagle. Sparse plant formations (mainly shrublands) had also a positive effect, while altitude, agricultural land and deciduous forests had a negative influence. The relative abundance of one of its main preys, the Red Partridge (Alectoris rufa), favored the probability of occurrence of Bonelli’s eagle, but only in the less sunny areas located in the north of Spain. The relative abundance of its main competitor, the Golden eagle (Aquila chrysaetos), was slightly but positively correlated with both the distribution and the abundance of the Bonelli’s eagle in the Spanish portion of the Iberian Peninsula, probably due to similarities in their habitat preferences. Finally, we did not find further regional effects of the variables describing the degree of human pressure (density of roads, urban cover, and length of power lines).     

On the relationship between Pielou’s evenness and landscape dominance within the context of Hill’s diversity profiles

Entropy-related biodiversity indices deriving their conceptual basis from Shannon’s information theory have a long history of use in ecology for quantifying community structure and diversity. In addition, in the last two decades, numerous information–theoretical indices, such as the landscape dominance index, have been extensively applied to characterize landscape diversity in space and time. In this contribution, we offer a simple analytical relation between Pielou’s evenness J and landscape dominance D within the broader context of Hill’s parametric diversity family. Within this context, we recommend the use of Hill’s diversity number evenness E_1,0 to overcome the shortcomings both of Pielou’s evenness J and the landscape dominance index D.     

Postglacial history of a widespread conifer produces inverse clines in selective neutrality tests

Deviations of the site frequency spectrum of mutations (SFS) from neutral expectations may be caused by natural selection or by demographic processes such as population subdivision or temporal changes in population size. As most widespread temperate and boreal tree species have expanded from glacial refugia in the past 13 000 years, colonization bottlenecks associated with this migration may have left variable demographic signatures among geographic populations corresponding to distance from the refugia. To determine whether the signature of postglacial re‐colonization has skewed the SFS in the widely distributed conifer Sitka spruce (Picea sitchensis (Bong.) Carr.), we re‐sequenced 153 nuclear genes in six populations from across the species range. We found that while the SFS for the pooled sample produced negative values for Tajima’s D and Fay and Wu’s H, these statistics exhibited strong clinal variation when populations were analysed separately (R² = 0.84, P = 0.007 for Tajima’s D and R² = 0.65, P = 0.033 for Fay and Wu’s H). When historical bottlenecks of varying age were simulated using approximate Bayesian computation, distance of populations from the southern range limit explained most of the variation in bottleneck timing among populations (R² = 0.89, P = 0.003). These data suggest that sequential population bottlenecks during postglacial re‐colonization have resulted in diverse among‐population signatures within the contemporary SFS in Sitka spruce, with rare variants more common in the south, and medium‐frequency variants more common in the north. Our results also emphasize the need to consider sampling strategy and to explore population‐specific null demographic models in surveys of nucleotide variation in widely distributed species.     

Evaluation and implications of Andean potato weevil infestation sources for its management in the Andean region

The Andean potato weevil Premnotrypes suturicallus Kuschel (Coleoptera: Curculionidae) is one of the most damaging potato (Solanum spp.) pests in the Andes. The objective of this study was to get a better understanding of weevil infestation sources and its distribution in potato fields as well as on the effect of potato cropping intensity and farmers’ harvest practices on weevil infestation to provide better clues for its management. For this purpose, a methodology was developed to assess weevil field densities in potato. A Taylor’s power law indicated that 177 and 69 samples are necessary to assess low (0.5 weevils/m²) and high (5 weevils/m²) weevil densities for a moderate reliability or precision level (D = 0.5). In potato fields, overwintering weevil densities were highest at field borders with 3.5 weevils/m² at a distance of <2.5 m compared to 0.7 weevils/m² at distances >10 m from the field border. No effects of time of harvest could be detected on soil overwintering weevil densities. The quantification of the larval density per potato plant after harvest showed that fields after 2‐year potato rotations had eight times more overwintering weevils compared to 1‐year rotations. Weevil infestation sources were mainly potato fields with the highest infestation (89%) followed by olluco (Ullucus tuberosus) and oat (Avena sativa) fields having volunteer potato plants (35%). The results confirm and support previous assumptions about the importance of the cropping systems for Andean potato weevil infestation and management. The confirmation that weevils do not occur or only in neglected numbers on fallow fields supports the use of plastic barriers to effectively exclude migrating flightless adult weevils to potato fields cultivated after fallow. The distribution of overwintering weevils indicates that farmers could concentrate efforts to control adult weevils mainly to the first meters of potato fields.     

Spatial dispersion and sampling of citrus whitefly,Dialeurodes citri,for control decisions in a citrus orchard

1 Monitoring the citrus whitefly Dialeurodes citri (Ashmead) in citrus orchards in Israel is necessary for control decisions in IPM in the period before the establishment of natural enemies. The main damage caused by D. citri is due to sooty mould, which colonizes the sweet secretions of this pest. 2 Using Taylor’s Power Law to describe the variance–mean relationship, the dispersion of the citrus whitefly was found to be aggregated at all developmental stages. The action threshold was estimated using regression of sooty mould level on egg or larval counts. 3 Two-stage sampling plans were constructed in different pest generations, for eggs and larval stages, on the basis of the variance between leaves on a tree and the variance between trees in a plot. 4 Fixed sample size plans were prepared, with possible numbers of trees and the numbers of leaves per tree to be sampled, in order to attain a given precision level. 5 Sequential sampling plans were also drawn up, on the basis of four leaves per tree, where trees are sampled until a decision can be reached. The maximum number of trees to be sampled was set according to the corresponding fixed sample size plan. 6 Simulation of the sequential sampling plans showed them to be highly reliable in terms of the decision reached with economy in sample size for high and low infestation levels.     

Sexual size and shape evolution in European newts (Amphibia: Caudata: Salamandridae) on the Balkan Peninsula

We used a phylogenetic perspective in an examination of the direction and extent of sexual dimorphism in body size and body shape in European newts from the Balkan Peninsula (alpine newts, Mesotriton alpestris; crested newts, Triturus cristatus superspecies; smooth newts, Lissotriton vulgaris). We found a strong, female‐biased sexual size dimorphism (SSD) in the analysed clades of alpine newt, whereas within crested newts we found a less stringent female‐biased SSD in Triturus carnifex, Triturus macedonicus and Triturus karelinii, and no significant SSD in T. cristatus or Triturus dobrogicus. Among the smooth newts, we found male‐biased SSD in Lissotriton vulgaris vularis and Lissotriton vulgaris greacus and no SSD in Lissotriton vulgaris meridionalis. Most of these newts also exhibit a significant sexual dimorphism in body shape, which varied more randomly than body size, regardless of SSD level. Female and male body size as well as the degree of SSD displayed statistically significant phylogenetic signal, while sexual dimorphism in body shape was phylogenetically independent. The relationship between independent contrast data for female size and male size indicated that SSD in European newts could be driven by a disproportionate increase in female size as increase in female size was not accompanied by a proportional increase in male size.     

Colorimetry and prime colours – a theorem

Human colour vision is the result of a complex process involving topics ranging from physics of light to perception. Whereas the diversity of light entering the eye in principle span an infinite-dimensional vector space in terms of the spectral power distributions, the space of human colour perceptions is three dimensional. One important consequence of this is that a variety of colours can be visually matched by a mixture of only three adequately chosen reference lights. It has been observed that there exists one particular set of monochromatic reference lights that, according to a certain definition, is optimal for producing colour matches. These reference lights are commonly denoted prime colours. In the present paper, we intend to rigorously show that the existence of prime colours is not particular to the human visual system as sometimes stated, but rather an algebraic consequence of the manner in which a kind of colorimetric functions called colour-matching functions are defined and transformed. The solution is based on maximisation of a determinant determining the gamut size of the colour space spanned by the prime colours. Cramer’s rule for solving a set of linear equations is an essential part of the proof. By means of examples, it is shown that mathematically the optimal set of reference lights is not unique in general, and that the existence of a maximum determinant is not a necessary condition for the existence of prime colours.     

The role of ventral premotor cortex in action execution and action understanding

The human ventral premotor cortex overlaps, at least in part, with Broca's region in the dominant cerebral hemisphere, that is known to mediate the production of language and contributes to language comprehension. This region is constituted of Brodmann's areas 44 and 45 in the inferior frontal gyrus. We summarize the evidence that the motor related part of Broca's region is localized in the opercular portion of the inferior frontal cortex, mainly in area 44 of Brodmann. According to our own data, there seems to be a homology between Brodmann area 44 in humans and the monkey area F5. The non-language related motor functions of Broca's region comprise complex hand movements, associative sensorimotor learning and sensorimotor integration. Brodmann's area 44 is also a part of a specialized parieto-premotor network and interacts significantly with the neighbouring premotor areas. In the ventral premotor area F5 of monkeys, the so called mirror neurons have been found which discharge both when the animal performs a goal-directed hand action and when it observes another individual performing the same or a similar action. More recently, in the same area mirror neurons responding not only to the observation of mouth actions, but also to sounds characteristic to actions have been found. In humans, through an fMRI study, it has been shown that the observation of actions performed with the hand, the mouth and the foot leads to the activation of different sectors of Broca's area and premotor cortex, according to the effector involved in the observed action, following a somatotopic pattern which resembles the classical motor cortex homunculus. On the other hand the evidence is growing that human ventral premotor cortex, especially Brodmann's area 44, is involved in polymodal action processing. These results strongly support the existence of an execution-observation matching system (mirror neuron system). It has been proposed that this system is involved in polymodal action recognition and might represent a precursor of language processing. Experimental evidence in favour of this hypothesis both in the monkey and humans is shortly reviewed.     

Faà di Bruno's formula and the distributions of random partitions in population genetics and physics

We show that the formula of Faà di Bruno for the derivative of a composite function gives, in special cases, the sampling distributions in population genetics that are due to Ewens and to Pitman. The composite function is the same in each case. Other sampling distributions also arise in this way, such as those arising from Dirichlet, multivariate hypergeometric, and multinomial models, special cases of which correspond to Bose–Einstein, Fermi–Dirac, and Maxwell–Boltzmann distributions in physics. Connections are made to compound sampling models.