Tracking island colonization history and phenotypic shifts in Indian Ocean bulbuls (Hypsipetes: Pycnonotidae)

Molecular phylogenies of island organisms provide useful systems for testing hypotheses of convergent or parallel evolution, since selectively neutral molecular characters are likely to be independent of phenotype, and the existence of similar environments on multiple isolated islands provides numerous opportunities for populations to evolve independently under the same constraints. Here we construct a phylogenetic hypothesis for Hypsipetes bulbuls of the western Indian Ocean, and use this to test hypotheses of colonization pattern and phenotypic change among islands of the region. Mitochondrial sequence data were collected from all extant taxa of the region, combined with sequence data from relevant lineages in Asia. Data are consistent with a single Hypsipetes colonization of the western Indian Ocean from Asia within the last 2.6 Myr. The expansion of Hypsipetes appears to have occurred rapidly, with descendants found across the breadth of its western Indian Ocean range. The data suggest that a more recent expansion of Hypsipetes madagascariensis from Madagascar led to the colonization of Aldabra and a secondary colonization of the Comoros. Groupings of western Indian Ocean Hypsipetes according to phenotypic similarities do not correspond to mtDNA lineages, suggesting that these similarities have evolved by convergence or parallelism. The direction of phenotypic change cannot be inferred with confidence, since the primary expansion occurred rapidly relative to the rate of mtDNA substitution, and the colonization sequence remains uncertain. However, evidence from biogeography and comparison of independent colonization events are consistent with the persistence of a small grey continental bulbul in India and Madagascar, and multiple independent origins of large size and green plumage in insular island populations of the Comoros, Mascarenes and Seychelles. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 271–287.     

Auxin Induced Lateral Root Formation in Chicory

The supply of auxins [2,4-dichlorophenoxy acetic acid (2,4D),indole-3 acetic acid (1AA) and -naphthaleneacetic acid (NAA)]to excised chicory roots induced the formation of lateral rootmeristems mainly located close to the pre-existing apical rootmeristem. Lateral root growth induced in non-excised roots requiredhigher auxin concentrations. Inhibition of root elongation andconcomittant enlargement of the apices was also observed. SupplyingIAA induced the formation of lateral meristems earlier thanNAA, but subsequently favoured root elongation. Conversely,in the presence of 2,4D, reactivation of pericycle cells wasvery intense, but conversion of primordia to laterals was inhibited.Regardless of the auxin used, the responsive area in which lateralmeristems appeared was located a maximum of 4 mm away from theapical meristem. This region remained devoid of any lateralroot formation under control conditions. Pericycle cells oppositethe xylem poles in the diarch stele regained meristematic activityand divided transversally, giving rise to shorter cells. Thesecells subsequently divided periclinally, forming pairs of cellson the same transverse level. The root primordium extruded throughcortical cells and was surrounded by a lacuna formed to thedetriment of cortical cells.Copyright 1998 Annals of BotanyCompany Auxins,Cichorium intybus, chicory, lateral root, root elongation.     

Five polymorphic microsatellite markers for the study of Cardiocondyla elegans (Hymenoptera: Myrmicinae)

We describe primer sequences for five microsatellite markers in Cardiocondyla elegans, an ant species with ergatoid males. Polymorphism of these loci was investigated using 236 individuals from 22 colonies from four locations. The microsatellites are dinucleotide repeats with four to 16 alleles, and the observed heterozygosity ranges from 0.244 to 0.720. We characterized these markers for the study of the population as well as the social structure of colonies.     

Sound production in four damselfish (Dascyllus) species: phyletic relationships?

Most studies of fish sounds show that the sounds are species-specific, with unique spectral and timing characteristics. This raises the question as to whether these sounds can be used to understand phyletic relationships between species and which acoustic parameters are subject to variation between species. In the present study, 597 sounds (and 2540 pulses) related to signal jumps of four Dascyllus species ( Dascyllus aruanus , Dascyllus trimaculatus , Dascyllus albisella , and Dascyllus flavicaudus ) from different geographic regions (Madagascar, Moorea, Rangiroa, and Hawaii) were analysed. It was possible to discern species-specific sounds, but also variation in sounds between populations. Large variations in sound length were found between Dascyllus species, whereas differences in interpulse duration were found to be variable between populations. In the regions where species live in sympatry, it appears that they restrict the variability in their sounds. This could comprise evidence of adaptation with character displacement of sonic characteristics where different species co-occur. However, sonic characteristics still overlapped substantially between species, suggesting that females would need to sample more than one sound and potentially use other cues to discriminate between species.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 928–940.     

The shredding activity of gammarids facilitates the processing of organic matter by the subterranean amphipod Niphargus rhenorhodanensis

1. The functional feeding group approach has been widely used to describe the community structure of benthic invertebrates in relation to organic matter resources. Based on this functional framework, positive interactions between feeding groups (especially shredders and collector‐gatherers) were postulated in the River Continuum Concept. However, relationships with organic matter have been poorly documented for invertebrates living in the hyporheic zone. 2. We hypothesised that the common subterranean amphipod Niphargus rhenorhodanensis would feed on fine particulate organic matter (FPOM), which is more abundant than coarse particulate organic matter (CPOM) in hyporheic habitats, and should be favoured by the occurrence of shredders that produce FPOM from CPOM. 3. We used laboratory experiments to quantify leaf litter processing by N. rhenorhodanensis and a common shredder, the surface amphipod Gammarus roeselii. We estimated rates of feeding and assimilation (using nitrogen stable isotopes) of the two species separately and together to reveal any potential shredder–collector facilitation between them. 4. Measured leaf litter mass loss showed that N. rhenorhodanensis did not act as a shredder, unlike G. roeselii. Organic matter dynamics and ¹⁵N/¹⁴N ratios in tissues of niphargids indicated that N. rhenorhodanensis was a collector‐gatherer feeding preferentially on FPOM. We also found a positive influence of the gammarid shredders on the assimilation rate of N. rhenorhodanensis, which fed on FPOM produced by the shredders, supporting the hypothesis of a positive interaction between surface shredders and hyporheic collector‐gatherers.     

Bacterial rhamnolipids are novel MAMPs conferring resistance to Botrytis cinerea in grapevine

Rhamnolipids produced by the bacteria Pseudomonas aeruginosa are known as very efficient biosurfactant molecules. They are used for a wide range of industrial applications, especially in food, cosmetics and pharmaceutical formulations as well as in bioremediation of pollutants. In this paper, the role of rhamnolipids as novel molecules triggering defence responses and protection against the fungus Botrytis cinerea in grapevine is presented. The effect of rhamnolipids was assessed in grapevine using cell suspension cultures and vitro-plantlets. Ca²⁺ influx, mitogen-activated protein kinase activation and reactive oxygen species production form part of early signalling events leading from perception of rhamnolipids to the induction of plant defences that include expression of a wide range of defence genes and a hypersensitive response (HR)-like response. In addition, rhamnolipids potentiated defence responses induced by the chitosan elicitor and by the culture filtrate of B. cinerea . We also demonstrated that rhamnolipids have direct antifungal properties by inhibiting spore germination and mycelium growth of B. cinerea . Ultimately, rhamnolipids efficiently protected grapevine against the fungus. We propose that rhamnolipids are acting as microbe-associated molecular patterns (MAMPs) in grapevine and that the combination of rhamnolipid effects could participate in grapevine protection against grey mould disease.     

Elevated CO2 decreases seed germination in Arabidopsis thaliana

The impact of elevated [CO₂] on seed germination was studied in different genotypes of Arabidopsis thaliana from natural populations. Two generations of seeds were studied: the maternal generation was produced in the greenhouse (present-day conditions), the offspring generation was produced in two chambers where the CO₂ concentration was either the present atmospheric concentration (about 350 ppm) or elevated (700 ppm). The seeds were tested for proportion of germinated seeds and mean germination time in both chambers to study the impact of elevated [CO₂] during seed production and germination. Elevated [CO₂] during maturation of seeds on the mother-plants decreased the proportion of germinated seeds, while elevated [CO₂] during germination had no effect on the proportion of germinated seeds. However, when seeds were both produced and germinated under elevated [CO₂] (situation expected by the end of next century), germination was slow and low. Moreover, the effect of the [CO₂] treatment differs among genotypes of Arabidopsis: there is a strong treatment × genotype interaction. This means that there is ample genetic variance for a selective response modiying the effects of high levels of [CO₂] in natural populations of Arabidopsis thaliana. The outcome at the community level will depend on what seeds are available, when they germinate and the resulting competition following germination.     

Changes in RNA and Protein Metabolism Associated with Alterations in the Germination Efficiency of Sunflower Seeds

Precise knowledge of seed quality after harvest and during storageis of particular importance for seed producers. We analyseddifferent sunflower seed lots (Helianthus annuusL.) characterizedby extremes of germination ability. We used RNA analysis tostudy possible changes in gene expression in seeds unable togerminate. Total RNA content was very small in dry seeds showinga low germination ability. Capacity for total RNA synthesisat the onset of imbibition was also reduced in these seeds.In addition, correlations were found between these parametersand germination ability at 19 °C. We demonstrated a highcorrelation between the amount of total RNA in the dry seed,the capacity of RNA synthesis at the onset of imbibition andthe seed moisture content at the time of the harvest. The abilityof dry seed mRNAs to be translatedin vitrowas also reduced andseven polypeptides, from stored mRNAs, were characteristic ofthe cotyledons from high germinability seeds. Germination canthus be affected at several levels including membrane, enzymaticand nucleic acid deteriorations. Gene expression; germination ability; Helianthus annuusL.; marker; protein; RNA; seed; sunflower