Climate impacts on Mediterranean blue tit survival: an investigation across seasons and spatial scales

In some hole nesting passerine species, long‐term monitoring data are available for several geographically independent populations. Climate forcing can then be documented and predictions made on the scale of distribution ranges. Several demographic studies of Paridae report dramatic impacts of wintertime climatic factors. However, these studies were undertaken in populations located in the northern parts of the species' ranges. Studies on the survival of Paridae in their southern ranges are necessary in order to assess potential latitudinal variation in climate forcing on survival. Based on monitoring of individual adult blue tits (Parus caeruleus), the effects of climatic factors on annual survival were assessed in three distinct Mediterranean populations. In these regions, climatic conditions in early summer might be expected to have a strong impact because they can be extremely hot and dry and because at this time of year Paridae are subjected to intrinsic constraints that stem from energetically costly postbreeding moult, recovery from reproductive costs, and from population densities inflated by the new cohort of fledglings. The impact of climatic conditions in early summer was, thus, addressed in addition to that prevailing in winter. In order to consider a large number of local climatic variables while limiting statistical power loss, integrative indices of local climate were built using multivariate techniques. In addition, the NAO and three large‐scale factors that are closely linked with atmospheric and oceanic circulation in the intertropical zone were considered as potentially influential factors in winter and early summer. Relationships between blue tit survival and indices of local temperature and precipitation in winter and in early summer were detected. Adult survival also correlated with a large‐scale tropical index in early summer: rainfall in the Sahel. This is one of the first quantitative indications that fluctuations in summer climatic conditions explain a significant part of the temporal variation in adult survival in unconnected populations of a sedentary European vertebrate. Furthermore, the results support the hypothesis that summertime local climates in Western Europe are closely linked with atmospheric and oceanic circulation in the intertropical zone.     

Density‐mediated indirect interactions alter host foraging behaviour of parasitoids without altering foraging efficiency

1. Foraging decisions of parasitoids are influenced by host density via density‐mediated indirect interactions. However, in the parasitoid's environment, non‐suitable herbivores are also present. These non‐hosts also occur in different densities, which can affect a parasitoid's foraging behaviour. 2. The influence of non‐host densities can be expressed during the first phase of the foraging process, when parasitoids use plant volatiles to locate plants infested by their host. They may also play a role during the second phase, when parasitoids use infochemicals from the host and plant to locate, recognise and accept the host. 3. By using laboratory and field setups, it was studied whether the density of non‐host herbivores influences these two phases of the foraging behaviour of the parasitoid Cotesia glomerata as well as the parasitoid's efficiency to find its host, Pieris brassicae caterpillars. 4. The findings show that a high non‐host density, regardless of the species used, negatively affected parasitoid preference for host‐infested plants, but that the behaviour on the plant and the total host‐finding efficiency of the parasitoids were not influenced by non‐host density. 5. These results are discussed in the context of density‐mediated indirect interactions.     

Using fractal dimensions for characterizing tortuosity of animal trails

ABSTRACT. The tortuosity of mite trails was characterized by their fractal dimension, which is the non-Euclidean dimension varying between 1 (completely straight) and 2 (so tortuous that the complete two-dimensional space is used). This index was shown to be a good, discriminative index for mite trails, which is a completely new use of the fractal dimension. The value of this index is compared with other tortuosity indices.     

Differences in the onset of laying between island and mainland Mediterranean Blue Tits Parus caeruleus: phenotypic plasticity or genetic differences?

Blue tits Parus caeruleus breeding in deciduous or in evergreen woodlands on the mainland of Europe start to lay 3–4 weeks earlier than Blue Tits on the island of Corsica breeding in evergreen woodlands. A similar difference in average laying date between the two Blue Tit populations has been found in a relatively small sample of captive birds held in outdoor aviaries on the mainland. To provide data on the habitat contrast in Corsica for comparison with that on the mainland, a new study area was started in one of the few deciduous woodlands on Corsica. In addition, new data on laying dates of captive Blue Tits were gathered to increase the sample size of independent pairs in aviaries. This study shows that the habitat effect (deciduous ν evergreen woodland) on the average laying date of Blue Tits is relatively small in comparison with the geography effect (European mainland ν Corsica). The laying date differences between mainland and insular Blue Tits persisted whatever the type of habitat (deciduous, evergreen or outdoor aviaries on the mainland). The data support the hypothesis that the observed differences in the onset of laying between the mainland and insular Blue Tits were mainly influenced by genetic effects and relatively little by non-genetic maternal effects of by genotype—environment interactions.     

The effect of habitat quality on foraging patterns, provisioning rate and nestling growth in Corsican Blue Tits Parus caeruleus

Many bird species face seasonal and spatial variation in the availability of the specific food required to rear chicks. Caterpillar availability is often identified as the most important factor determining chick quality and breeding success in forest birds, such as tits Parus spp. It is assumed that parents play an important role in mediating the effect of environment on chick development. A reduction in prey availability should therefore result in increased foraging effort to maintain the amount of food required for optimal chick development. To investigate the capacity of adults to compensate for a reduction in food supply, we compared the foraging behaviour of Blue Tits Parus caeruleus breeding in rich and poor habitats in Corsica. We monitored the foraging effort of adults using radiotelemetry. We also identified and quantified prey items provided to nestlings by using a video camera mounted on the nest. We found that the mean travelling distance of adults was twice as great in the poor habitat as it was in the rich. Despite the marked difference in foraging distance, the proportion of optimal prey (caterpillars) in the diet of the chicks and the total biomass per hour per chick did not differ between the two habitats. We argue that relationships between habitat richness, offspring quality and breeding success cannot be understood adequately without quantifying parental effort.     

A study of genetic distances and variability in several species pf the gemis Ctenomys (Rodentia: Octodontidae) with special references to a probable causal role of chromosomes in speciation

Genetic variability measured by allozymic electrophoresis has been studied in several species of the subterranean rodent genus Ctenomys (Octodontidae). The study was carried out with the main purpose of analysing a special group known as the 'Corrientes group' which inhabits the province of Corrientes in Argentina. The members of the group are, with high probability, isolated reproductively due to their karyotypic differences diploid numbers are between 42 and 70). To evaluate whether the chromosomal differences were the causes of speciation or if they arose a posteriori, we compared the level of the genetic distance among taxa within the orrientes group with all those measured between intraspecific populations in Ctenomys . The results indicate that the distances among the populations of the Corrientes group are at or below the level of those measured among traspecific populations in Ctenomys . Thus, it is unlikely that genetic differentiation triggered speciation. It is shown that this low level of genetic differentiation is not in contradiction with the high levels expected for species originating from one of the possible mechanisms of chromosomal speciation named, chromosomal transilience. Although for geographical reasons it seems obviousthat gene flow is precluded among the members of the Corrientes group, the Slatkin method for estimating Nm values was also used. Because high values of Nm exist but no isolation by distance could be detected, it is suggested that reproductive and geographical isolation are very ecent. Finally, analysis of population variability suggests that the high levels of heterozygosity observed (a) can be explained by the population structure, and (b) are within the range of expected values if bottlenecks have occurred in the recent history of the Corrientes group. As a general conclusion, the results indicate that in the Corrientes group the genetic data support a putative causal role for chromosomes in speciation.     

Revision and cladistic analysis of the eumenine wasp genus Pseudodynerus de Saussure (Hymenoptera, Vespidae, Eumeninae)

Abstract.  The eumenine genus Pseudodynerus is revised, and the phylogenetic relationships among its species are reconstructed based on adult morphology. The cladistic analyses of the 21 terminal species (15 ingroup and six outgroup species) and 48 characters, from external morphology and male genitalia, produced one cladogram under equal weights and two under implied weights. The monophyly of Pseudodynerus was corroborated in all three hypotheses, although the internal relationships varied depending on the weighting scheme. Two major clades were recovered under both equal and implied weights, one containing mostly Central and North American species and the other only South American species. The main difference between the hypotheses involves the placement of P. luctuosus , which comes out either as sister to a clade formed by P. hallinani  + ( P. maxillaris  +  P. quadrisectus  +  P. crypticus ) or as sister to a clade comprising the remaining species. Fifteen species of Pseudodynerus are recognized, of which four are described as new: P. crypticus from Costa Rica, P. carpenteri from French Guiana and Suriname, P. obesus from Rondônia, Brazil, and P. singularis from Espírito Santo, Brazil. One new synonymy is proposed: Odynerus ( Odynerus ) aztecus de Saussure, 1857  =  Pseudodynerus quadrisectus ( Say, 1837 ) syn.n. Names treated as varieties by Bequaert (1941) are not recognized at any level herein, as follows: Monobia mina-palumboi Gribodo, 1891 , stat.rev. ; Odynerus ( Leionotus ) beelzebub Zavattari, 1912 , stat.rev. ; Stenodynerus anisitsii garleppi Schrottky, 1911 , stat.rev. ; and Stenodynerus mondaiensis Bertoni, 1918, stat.rev. Lectotypes are designated for Odynerus bellone Lepeletier, 1841 , Odynerus ( Odynerus ) aztecus de Saussure, 1857 and Odynerus ( Stenodynerus ) migonei Bertoni, 1926 .