Water balance in the Argentine ant (Linepithema humile) compared with five common native ant species from southern California

Abstract.  Little attention has been given to the effect of physiological limitations on the ability of introduced species to invade ecological communities. In the present study, the water balance of the invasive Argentine ant ( Linepithema humile ) is compared with five common ant species native to southern California. Total and critical water contents are measured, as well as rates of water loss and survival times. The results show that the body size of ant species has a strong effect on water balance, explaining between 99% of total and 90% of critical water content (i.e. the amount of water remaining when the ant becomes moribund). The measured survival times at 40 °C and approximately 0% relative humidity are shorter for L. humile than for the other five native ant species. The area-independent water-loss rate is higher for L. humile than for the other native ant species studied. This finding is corroborated by independent data using two different methods (i.e. gravimetric measurement and open-flow respirometry). Somewhat surprisingly, significant differences in the water-loss rates of different sizes of Solenopsis xyloni workers are found, even after adjusting for surface area. The area-independent water-loss rate is significantly lower for larger than for smaller workers. Consistent with circumstantial evidence from the field, the results suggest that the physiological constraints of invasive species, such as water-loss rates and critical water content, can limit their distribution and abundance not only at regional scales, but also at fine scales.     

Relationship between song characters and morphology in New World pigeons

We studied the pattern of variation in song characters among 16 New World pigeon species belonging to different taxonomic groups defined by morphological characters. Structural, temporal and frequency characters of the song were analysed. Principal components analyses showed that species belonging to the same taxonomic group were also grouped together by their song characters. In addition, individuals were correctly assigned into taxonomic groups by discriminant function analyses in more than 87.8% of cases. These analyses also showed that more than 87.5% of the individuals could be correctly classified by species when all song characters were included. Correct classification of individuals by species and taxonomic groups dropped when character types were analysed separately, thus showing that structural, as well as temporal and frequency characters are fundamental to define species- and group-specific identities of New World pigeon's songs. Correspondence between patterns of vocal and morphological variation found in this study can be a consequence of evolutionary changes in morphology affecting song production, as for example body size changes that constrain the syrinx to produce certain acoustic frequencies.     

Female-biased sexual size dimorphism in tinamous: a comparative test fails to support Rensch's rule

Rensch's rule states that degree of sexual dimorphism increases with body size in species with larger males, and decreases with body size in those with larger females. To test this rule, we assessed the pattern of sexual size dimorphism in tinamous using a comparative analysis of independent contrasts. Tinamous are a monophyletic group of primitive birds comprising at least 47 ground dwelling species with prominent or exclusive paternal care of eggs and offspring. Although the size of females exceeded that of males in most considered species, we found an isometric relationship between males and females, instead of the negative allometric one predicted by Rensch's rule. Previous studies in Strigiformes and Falconiformes found positive allometric and isometric relationships respectively, and, considering these findings with our results, we conclude that Rensch's rule is not supported by birds with exclusively female-biased sexual dimorphism in size.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 519–527     

Seed micromorphology in the genus Neotinea Rchb.f. (Orchidaceae, Orchidinae)

The ultrastructure of testa seed in the genus Neotinea (Orchidaceae, Orchidinae) was examined for the first time. The morphology of the seed and of the anticlinal and periclinal walls was analysed by scanning electron microscopy. Quantitative data concerning the length and width of the seed and embryo, seed and embryo volume, free air space, and number of cells along the longitudinal axis are presented. In all species, the seeds are fusiform in shape with transverse ridges on the inner periclinal walls. This ornamentation pattern is characteristic for the genus Neotinea . It is a good diagnostic value supporting the monophyly of this genus, which has recently been proposed by several authors.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 133–140.     

The Politics of the Past in an Argentine Working-Class Neighbourhood

The Politics of the Past in an Argentine Working-Class Neighbourhood. Lindsay DuBois. Toronto: Toronto Press, 2005. 283 pp.     

European rabbit population trends and associated factors: a review of the situation in the Iberian Peninsula

• 1 European rabbits are considered a keystone species in the Iberian Peninsula. Their populations have sharply declined over the past century, mainly due to habitat loss and the arrival of two viral diseases: myxomatosis in the 1950s and rabbit haemorrhagic disease (RHD) at the end of the 1980s. For the conservation of the Iberian Mediterranean ecosystem, it is important to determine whether rabbit populations are recovering two decades after the RHD outbreak, and to identify the factors associated with population recovery.
• 2 Here, we review the current knowledge on recent rabbit population trends in the Iberian Peninsula and the factors associated with these trends.
• 3 Although most rabbit populations are still declining in the Iberian Peninsula, a few seem to have recovered. In general, positive trends have been recorded in species‐friendly habitats characterized by non‐fragmented landscapes, interspersed patches of Mediterranean scrubland, good pastures and/or crops, soft soils that are suitable for warren construction and a Mediterranean climate with relatively high rainfall. Additionally, rabbits seem to be recovering better in areas where management practices (e.g. low hunting pressure, habitat management and predator control) are applied to increase their numbers.
• 4 From these findings, it is possible to identify five broad objectives for rabbit conservation in the Iberian Peninsula. First, it is clearly necessary to establish a long‐term programme for monitoring rabbit abundance and trends on a large scale. Second, the conservation and restoration of open Mediterranean scrubland should be a priority for stabilizing and maintaining existing healthy rabbit populations. Third, despite the lack of experimental evidence, management activities aimed at increasing the quantity and quality of both refuge and food should continue to be implemented. Fourth, legislation on the timing of the hunting season should be revisited following recommendations made by scientists. Finally, experimental approaches are required to investigate whether the control of generalist predators is a successful strategy to allow rabbit populations to recover.

     

Combined impacts of longline fisheries and climate on the persistence of the Amsterdam Albatross Diomedia amsterdamensis

Incidental capture of seabirds in longline fishing gear is a central issue in the conservation of many long-lived marine species. Despite growing evidence of climate-induced effects on population trends of long-lived species, climate change remains generally overlooked in most risk assessments of seabirds. Because variation in climate may interact with the detrimental effects of bycatch, considering climate is of great importance, especially in the context of ongoing global warming. This paper examines the combined effects of bycatch and climate change on the persistence of one of the world's rarest birds, the Amsterdam Albatross Diomedea amsterdamensis , which has a single population in the upland plateau of Amsterdam Island (Southeast Indian Ocean). Using continuous monitoring from 1983 onwards, we first estimated the relationship between climate and the species' demographic parameters. We then built a stochastic matrix population model to estimate the population growth rate and the probability that the population declines below the level recorded in 1983 of nine breeding pairs under different scenarios involving the joint effects of additional mortality caused by longline fisheries and climate change. The results suggest that the demography of the Amsterdam Albatross is influenced by climate in both breeding and wintering grounds and that these relationships may to some extent compensate for the impact of additive bycatch mortality. However, these compensatory effects would be negligible if the annual additional mortality exceeds around six individuals per year, suggesting that the resumption of longline fishery in the foraging range of the Amsterdam Albatross would rapidly put this species at risk of extinction.     

Genome redundancy and plasticity within ancient and recent Brassica crop species

The crop species within the genus Brassica have highly replicated genomes. Three base 'diploid' species, Brassica oleracea , B. nigra and B. rapa , are likely ancient polyploids, and three derived allopolyploid species, B. carinata , B. juncea and B. napus , are created from the interspecific hybridization of these base genomes. The base Brassica genome is thought to have hexaploid ancestry, and both recent and ancient polyploidization events have been proposed to generate a large number of genome rearrangements and novel genetic variation for important traits. Here, we revisit and refine these hypotheses. We have examined the B. oleracea linkage map using the Arabidopsis thaliana genome sequence as a template and suggest that there is strong evidence for genome replication and rearrangement within the base Brassicas, but less evidence for genome triplication. We show that novel phenotypic variation within the base Brassicas can be achieved by replication of a single gene, BrFLC , that acts additively to influence flowering time. Within the derived allopolyploids, intergenomic heterozygosity is associated with higher seed yields. Some studies have reported that de novo genomic variation occurs within derived polyploid genomes, whereas other studies have not detected these changes. We discuss reasons for these different findings. Large translocations and tetrasomic inheritance can explain some but not all genomic changes within the polyploids. Transpositions and other small-scale sequence changes probably also have contributed to genomic novelty. Our results have shown that the Brassica genomes are remarkably plastic, and that polyploidy generates novel genetic variation through gene duplication, intergenomic heterozygosity and perhaps epigenetic change.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 665–674.     

A preliminary molecular phylogenetic assessment of the lichen moths (Lepidoptera: Erebidae: Arctiinae: Lithosiini) with comments on palatability and chemical sequestration

The lichen moth tribe Lithosiini is best known for its hypothesized larval feeding behaviour, lichenivory. The larvae of some species have been found to be capable of sequestering polyphenolics, and the adults of some species are unpalatable to vertebrate predators. However, the chemical basis for the defence is unknown. Here we reconstruct a phylogenetic hypothesis using likelihood methods (maximum likelihood, Bayesian inference) for 65 species of Lithosiini representing 37 genera and seven outgroup species using 2806 bp of sequence data obtained from two mitochondrial gene fragments (COI barcoding region, CytB), and two nuclear gene fragments (RpS5 and ribosomal gene region 28S). Lithosiine species representing four of the seven subtribes and unplaced taxa are included in the analysis. The deeper relationships within the tribe are not strongly supported, and the monophyly of three of the four subtribes is not supported. The placement of the fourth subtribe, Acsalina, is weakly supported. We also conduct a survey of the secondary metabolites present within adults of five species. The species are examined for the presence of lichen polyphenolics and plant secondary metabolites sequestered by arctiines. Seven lichen polyphenolics are identified in the taxa examined, but no plant secondary metabolites are found using either analytical method. The results of this study and prior reports in the literature of chemical sequestration and unpalatability are plotted onto the resulting Bayesian inference phylogeny to examine the evolution of chemical defence within Lithosiini. Species that sequester lichen polyphenolics and unpalatable species occur in each of the major clades recovered in the analysis.