Spatial patterns in the distribution of European springtails (Hexapoda: Collembola)

Using a large database on the spatial distribution of European springtails (Collembola) we investigated how range sizes and range distribution across European countries and major islands vary. Irrespective of ecological guild, islands tended to contain more endemic species than mainland countries. Nestedness and species co‐occurrence analysis based on country species lists revealed latitudinal and longitudinal gradients of species occurrences across Europe. Species range sizes were much more coherent and had fewer isolated occurrences than expected from a null model based on random colonization. We did not detect clear postglacial colonization trajectories that shaped the faunal composition across Europe. Our results are consistent with a multiregional postglacial colonization. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 498–506.     

The controlling factors limiting maximum body size of insects

The purpose of this study is to consider the controlling factors limiting maximum body size of insects. For this analysis, we set up and quantitatively verify the following working hypothesis: insect body sizes can be explained only by the historical changes in the oxygen supply. The present study focuses on the body size of the Protodonata and Odonata. The amount of oxygen needed and that of oxygen entering the insect body was calculated using allometric equations. The theoretical maximum sizes at each geologic time were estimated from palaeo‐atmospheric oxygen partial pressure and compared with the maximum size of known fossilized insects. The historical change in fossilized insect sizes was much larger than that in theoretical sizes. Additionally, from the Jurassic, despite an increase in the partial pressure of oxygen, which would theoretically increase maximum size, the maximum size of fossilized insects became smaller. These findings are inconsistent with the expectations of the working hypothesis. Oxygen supply is likely to partially limit the maximum size of insects with additional factors.     

Meta-analysis in applied ecology

This overview examines research synthesis in applied ecology and conservation. Vote counting and pooling unweighted averages are widespread despite the superiority of syntheses based on weighted combination of effects. Such analyses allow exploration of methodological uncertainty in addition to consistency of effects across species, space and time, but exploring heterogeneity remains controversial. Meta-analyses are required to generalize in ecology, and to inform evidence-based decision-making, but the more sophisticated statistical techniques and registers of research used in other disciplines must be employed in ecology to fully realize their benefits.     

Geographical range size and host specificity in ectoparasites: a case study with Amphipsylla fleas and rodent hosts

Aim  To identify the factors that determine the geographical range sizes of ectoparasites with different degrees of host specificity.
Location  The study used data on the distributions of fleas of the genus Amphipsylla and their rodent hosts across the Holarctic.
Methods  All known points of occurrence of 32 flea species and 51 species of their rodent hosts were mapped. The shape and size of the geographical range of each species were estimated using a combination of the minimal convex polygon technique and modelling with the garp algorithm. Factors determining the geographical range sizes of the fleas were identified using stepwise multiple regression analysis.
Results  The geographical range size of fleas that are strongly host-specific across their entire ranges correlated positively with the geographical range size of the fleas' principal hosts, and negatively with the geographical range size of the fleas' potential competitors. The geographical range sizes of both (1) fleas that are locally host-specific but that shift their host preferences geographically, and (2) host-opportunistic fleas were positively correlated only with the area of the geographical ranges of their principal hosts. Strongly host-specific fleas occupied 0.2–80.0% of the geographical range of their principal hosts, whereas this figure was 0.9–83.7% in locally host-specific fleas and 16.6–63.7% in host-opportunistic fleas.
Main conclusions  The main determinant of the geographical range size of a flea species is the size of the geographical range of its hosts. The role of potential competitors in determining the geographical range size is stronger in host-specific than in host-opportunistic fleas. Cases in which the geographical range of a parasite is smaller than the geographical range(s) of its host(s) owing to narrower parasite environmental tolerances are much more frequent in host-opportunistic than in host-specific fleas.     

Flexible responses of insects to changing environmental temperature – early season development of Craspedolepta species on fireweed

Developmental response to temperature during the critical early season growing period was investigated in two congeneric species of Craspedolepta feeding on Epilobium angustifolium at three sites at different altitudes in Norway and the UK. The larval development reaction norm to temperature, measured as accumulated day degrees, was not significantly different between Craspedolepta nebulosa and Craspedolepta subpunctata at sites where they co‐occurred but C. nebulosa development was consistently more advanced at any site. For individual species the reaction norms at the lowest site (Ainsdale, UK) were similar to the intermediate site (Geilo, Norway): and there were no differences between years. Insect size remained relatively constant. However, at the highest site (Haugastøl, Norway), where C. subpunctata is unable to complete its development, the reaction norm for C. nebulosa was significantly higher than at Geilo and the individual insects produced were smaller. These adaptations allow life‐history completion under limiting temperature conditions. An experiment at Ainsdale, to raise the mean temperature by around 2.5°C during the early growing season, resulted in accelerated development in both C. nebulosa and C. subpunctata but development in C. nebulosa was accelerated proportionately more. C. nebulosa thus displays the greater plasticity in developmental response to environmental temperature that allows it to occupy a greater altitudinal and latitudinal range than C. subpunctata, in which the response is less plastic and more canalized. The likely individualistic responses of the two species to climate warming are considered.     

Impact of precocious male parr on the effective size of a wild population of Atlantic salmon

1. There is growing evidence that sexually mature but morphologically juvenile males of Atlantic salmon (precocious or mature male parr) actively participate in reproduction and, therefore, in the genetic composition of the populations of this species. The impact of mature male parr on the effective population size (N_e) of such populations has been previously studied under experimental settings, but no studies have been performed directly on natural populations. 2. Continuous monitoring and sampling of all sea returns is possible in the Lérez River (northwest of Spain). From demographic data on variances of reproductive success and genetic data from six microsatellite marker loci we carried out parentage assignment and assessed the impact of male parr on demographic and genetic estimates of N_e in two consecutive years. 3. Our results reveal that: (i) approximately 60% of the total sire paternity is attributable to mature parr; (ii) mature parr decrease the variance of reproductive success of males by a threefold factor and increase the effective population size of males by a 10‐fold factor; (iii) however, they do not substantially affect the variance of reproductive success and the effective size of females; (iv) mature parr increase two‐to threefold the overall effective size of the population but the ratio N_e/N, where N is the population size including or not mature parr in each case, is not affected.     

Determinants of local abundance in a major radiation of Australian passerines (Aves: Meliphagoidea)

Aim  To identify the factors that contribute to variation in abundance (population density), and to investigate whether habitat breadth and diet breadth predict macroecological patterns in a suborder of passerine birds (Meliphagoidea).
Location  Australia (including Tasmania).
Methods  Mean abundance data were collated from site surveys of bird abundance (the Australian Bird Count); range size and latitudinal position data from published distribution maps; and body mass and diet breadth information from published accounts. A diversity index of habitats used (habitat breadth) was calculated from the bird census data. We used bivariate correlation and multiple regression techniques, employing two phylogenetic comparative methods: phylogenetic generalized least squares and independent contrasts.
Results  Body mass and latitude were the only strong predictors of abundance, with larger-bodied and lower-latitude species existing at lower densities. Together, however, body mass and latitude explained only 11.1% of the variation in mean abundance. Range size and habitat breadth were positively correlated, as were diet breadth and body mass. However, neither range size, nor habitat breadth and diet breadth, explained patterns in abundance either directly or indirectly.
Main conclusions  Levels of abundance (population density) in meliphagoid birds are most closely linked to body mass and latitudinal position, but not range size. As with many other macroecological analyses, we find little evidence for aspects of niche breadth having an effect on patterns of abundance. We hypothesize that evolutionary age may also have a determining effect on why species tend to be rarer (less abundant) in the tropics.     

Analysis of the oviductal glycoprotein 1 polymorphisms and their effects on components of litter size in rabbits

The objective of this work was to study the effect of the oviductal glycoprotein 1 ( OVGP1 ) genotype and mRNA expression on litter size and other fertility measures, as OVGP1 has positive effects on fertilization and early embryo development. We have analysed an F₂ cross of two lines of rabbits divergently selected for uterine capacity. The OVGP1 mRNA expression was analysed in both lines, but no differences were observed between them. The promoter region and mRNA were sequenced in the F₀ generation, and 17 polymorphic sites were found to co-segregate in three haplotypes (A, B and C). An association study was performed between several reproductive traits and a triallelic microsatellite identified in the promoter region as well as a non-synonymous SNP located in exon 11 [g.12944C>G (p.Arg468Gly)]. The alleles g.12944G and g.325(GT)₁₄T(G)₅ of the B haplotype have a positive effect on the total number of kits born, number born alive, number of implanted embryos and foetal and prenatal embryo survival.     

A test of the mechanisms behind avian generalized individuals–area relationships

Aim Questions related to abundances of organisms are central to ecological research. A priori, a scale independent estimation of abundances would be expected. However, we find estimates of numbers of bird individuals from all over the world to increase less than proportionately with increasing plot size. At the whole assemblage level, the pattern holds across biogeographical regions and habitats. The slope of the interspecific and, for the majority of species, the intraspecific individuals–area relationship is also significantly shallower than 1. The question arises as to which mechanisms cause these patterns. Location Global. Methods At the assemblage, interspecific and intraspecific levels, we tested three mechanisms that could be responsible for these patterns by comparing the slope of the individuals–plot area relationship for subsets of a database compiled from the literature. Spatial autocorrelation was controlled for. Results There was no evidence for an influence of plot area choice in order to sample a constant number of individuals. Evidence for higher survey efficiency was available only with increasing number of visits at the intraspecific level. Evidence for influences of habitat heterogeneity was present at the assemblage, interspecific and intraspecific levels. This mechanism can work only if small plots are delimited non‐randomly in homogeneous habitat. Main conclusions Avian population size estimates without indication of the area over which they were obtained are of substantially less value than those coupled with that information. Ecologists planning to compare avian abundances between plots varying in some other factor of interest should minimize variations in their areas and/or account for them in data analyses. Population viability analyses, regional and global population size estimates, site prioritization and the scaling of ecosystem and species energy utilization need to address the plot area effect on assemblage and individual species abundances.