Biochemical and physiological mechanisms underlying effects of Cucumber mosaic virus on host‐plant traits that mediate transmission by aphid vectors

The transmission of insect‐vectored diseases entails complex interactions among pathogens, hosts and vectors. Chemistry plays a key role in these interactions; yet, little work has addressed the chemical ecology of insect‐vectored diseases, especially in plant pathosystems. Recently, we documented effects of Cucumber mosaic virus (CMV) on the phenotype of its host (Cucurbita pepo) that influence plant‐aphid interactions and appear conducive to the non‐persistent transmission of this virus. CMV reduces host‐plant quality for aphids, causing rapid vector dispersal. Nevertheless, aphids are attracted to the elevated volatile emissions of CMV‐infected plants. Here, we show that CMV infection (1) disrupts levels of carbohydrates and amino acids in leaf tissue (where aphids initially probe plants and acquire virions) and in the phloem (where long‐term feeding occurs) in ways that reduce plant quality for aphids; (2) causes constitutive up‐regulation of salicylic acid; (3) alters herbivore‐induced jasmonic acid biosynthesis as well as the sensitivity of downstream defences to jasmonic acid; and (4) elevates ethylene emissions and free fatty acid precursors of volatiles. These findings are consistent with previously documented patterns of aphid performance and behaviour and provide a foundation for further exploration of the genetic mechanisms responsible for these effects and the evolutionary processes that shape them.     

Exploring myrmecophily based on the phylogenetic interrelationships of Falagonia Sharp, 1883 (Coleoptera: Staphylinidae: Aleocharinae) and allied genera

The taxonomy of Lomechusini Fleming has a complex history. Recent studies have shown that this group is polyphyletic; however, little is known about the evolutionary interrelationships among its constituent genera. The goals of the present study are to infer the phylogenetic relationships of Falagonia Sharp and closely related genera; to define the boundaries of those genera based on synapomorphic characters; and to explore the evolution of myrmecophily within the lineage. The phylogenetic analyses are based exclusively on morphological characters of adults. A total of 36 operational taxonomic units were used for the analysis. The best trees were selected based on maximum parsimony and Bayesian inference. During the parsimony reconstruction, different weighting strategies were used to recover the most robust phylogenetic hypothesis. Although minor differences were observed in the results of the different analyses, the topologies were consistent throughout. Several groups of genera proposed by Seevers (1965), such as the ‘Tetradonia’ and ‘Ecitopora’ groups, were not recovered. Thus, these may represent nonmonophyletic groups that were based on nonsynapomorphic diagnostic characters. Our analyses consistently recovered the genera Asheidium Santiago‐Jiménez, Delgadoidium Santiago‐Jiménez, Falagonia, Newtonidium Santiago‐Jiménez, Pseudofalagonia Santiago‐Jiménez, Sharpidium Santiago‐Jiménez, Tetradonia Wasmann and Thayeridium Santiago‐Jiménez, forming a monophyletic group that we have called the ‘Asheidium complex’. Falagonia mexicana Sharp shows seven autapomorphies, none of which were used to establish the genus. Based on the phylogenetic results, myrmecophily has evolved independently at least three times within the lineage. This study, based on morphological characters, is one of the first approaches towards gaining an understanding of the phylogenetic relationships within the polyphyletic tribe Lomechusini.     

Comparative cytogenetic analysis of four species of <Emphasis Type="Italic">Dendropsophus</Emphasis> (Hylinae) from the Brazilian Atlantic forest

We conducted a cytogenetic study of four hyline frog species (Dendropsophus elegans, D. microps, D. minutus and D. werneri) from southern Brazil. All species had 2n = 30 chromosomes, with interspecific and intraspecific variation in the numbers of metacentric, submetacentric, subtelocentric and telocentric chromosomes. C-banding and fluorochrome staining revealed conservative GC-rich heterochromatin localized in the pericentromeric regions of all species. The location of the nucleolus organizer regions, as confirmed by fluorescent in situ hybridization, differed between species. Telomeric probes detected sites that were restricted to the terminal regions of all chromosomes and no interstitial or centromeric signals were observed. Our study corroborates the generic synapomorphy of 2n = 30 chromosomes for Dendropsophus and adds data that may become useful for future taxonomic revisions and a broader understanding of chromosomal evolution among hylids.     

Microsatellite loci in the eastern form of the giant freshwater prawn (Macrobrachium rosenbergii)

Six microsatellite loci were identified and characterized in the eastern form of the widespread and commercially important giant freshwater prawn (Macrobrachium rosenbergii). The loci were detected by randomly screening for dinucleotide and trinucleotide repeat units within a partial genomic library developed for the species. In a sample of 29 prawns, number of alleles and heterozygosity per locus ranged from 12 to 18 and from 0.66 to 0.90, respectively. These markers provide powerful tools for the conservation and management of wild stocks, the improvement of cultured stocks of M. rosenbergii, and for investigating evolutionary processes underlying genetic divergence among populations.     

The invasive grass,Melinis minutiflora,inhibits tree regeneration in a Neotropical savanna

Abstract Exotic grasses are becoming increasingly abundant in Neotropical savannas, with Melinis minutiflora Beauv. being particularly invasive. To better understand the consequences for the native flora, we performed a field study to test the effect of this species on the establishment, survival and growth of seedlings of seven tree species native to the savannas and forests of the Cerrado region of Brazil. Seeds of the tree species were sown in 40 study plots, of which 20 were sites dominated by M. minutiflora, and 20 were dominated by native grasses. The exotic grass had no discernable effect on initial seedling emergence, as defined by the number of seedlings present at the end of the first growing season. Subsequent seedling survival in plots dominated by M. minutiflora was less than half that of plots dominated by native species. Consequently, at the end of the third growing season, invaded plots had only 44% as many seedlings as plots with native grasses. Above‐ground grass biomass of invaded plots was more than twice that of uninvaded plots, while seedling survival was negatively correlated with grass biomass, suggesting that competition for light may explain the low seedling survival where M. minutiflora is dominant. Soils of invaded plots had higher mean Ca, Mg and Zn, but these variables did not account for the higher grass biomass or the lower seedling survival in invaded plots. The results indicate that this exotic grass is having substantial effects on the dynamics of the tree community, with likely consequences for ecosystem structure and function.     

Isolation and characterization of microsatellite markers for the ornamental discus fish Symphysodon discus and cross-species amplification in other Heroini cichlid species

The discus fishes (Symphysodon spp.) are economically important ornamental species. Thirteen microsatellite markers were developed from a CT(12) - and CA(12) -enriched whole genomic DNA library of Symphysodon discus. Allelic variability was tested on 44 individuals of two species (S. discus and S. aequifasciatus). Allelic richness ranged from two to 11 alleles per locus and observed heterozygosities from 0.083 to 0.998. All loci were at Hardy-Weinberg equilibrium, and no pair of loci showed linkage disequilibrium within a species. Cross-species amplification was also successfully performed in the Neotropical cichlids Uaru amphiacanthoides, Hoplarchus psittacus, Hypselecara coryphaenoides, Pterophyllum sp., Mesonauta sp. and Heros sp.