Chromosome numbers in Brazilian species of Crotalaria (Leguminosae, Papilionoideae) and their taxonomic significance

Chromosome numbers were counted for 23 species of Crotalaria native to Brazil. Among these data there were new counts for 15 taxa, and some confirmed previous reports or represented numbers that were different from those cited previously. The chromosome numbers most frequently found were 2 n  = 16 and 2 n  = 32. Only C. incana L. had 2 n  = 14 and C. tweediana Benth. had 2 n  = 54. The counts 2 n  = 32 and 54 were found in species of section Calycinae and 2 n  = 16 and 14 in species of section Chrysocalycinae . The data revealed the importance of chromosomal parameters in the characterization of sections Calycinae and Chrysocalycinae in Brazil. We discuss the systematic significance and evolutionary aspects for the genus, comparing the results with the two sections that are native in Brazil.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 271–277.     

Ontogenetic variation in density‐dependent growth of brown trout through habitat competition

1. Density‐dependent growth has been widely reported in freshwater fishes, but the ontogenetic evolution of competition and its subsequent effects on growth through a life span remains unclear. 2. Patterns of competition can be described by integrating population abundance data with habitat‐modelling results. Weighted usable area (WUA; m² WUA ha^?1) curves are obtained for each flow value and are then coupled with demographic data to obtain the occupancy rates (trout m^?2 WUA, the density of a given age class related to its suitable habitat) of the WUA for every age class, year and site. 3. We examined a long‐term data series searching for temporal variation in the influence of habitat occupancy rate on the growth of brown trout Salmo trutta. We tested whether (i) mean cohort mass (mean mass of the cohort during the first 3 years of life) is affected by the occupancy rate experienced across a life span; and (ii) the occupancy rate experienced at different ages influenced mean body size. 4. We observed a consistent negative power relationship between average cohort mass and mean occupancy rate through a life span, indicating that stronger cohorts were related to a reduced growth, with likely consequences for individual fitness. 5. The effects of occupancy rate on size‐at‐age were mainly detected in the size attained at the second year of life, but they were because of the competition at different times. Thus, the level of competition varied through ontogeny, in some of the rivers affecting growth since the first year of life, whereas in most of the rivers the main effects on body size resulted from the competition during the second year of life. 6. Occupancy rate appears more appropriate than density for assessing the occurrence of habitat competition in freshwater fishes, since it encompasses the differences in quantity and quality of suitable habitat for each age class. 7. Our study highlights the importance of density‐dependent growth as a key process in the dynamics of brown trout populations, its temporal variation depending on the temporal changes of density and the variation of competition associated with the habitat capacity for each life stage.     

Brood parasitism is associated with increased bacterial contamination of host eggs: bacterial loads of host and parasitic eggs

Factors related to bacterial environment of nests are of primary interest for understanding the causes of embryo infection and the evolution of antimicrobial defensive traits in birds. Nest visitors such as parasites could act as vectors for bacteria and/or affect the hygienic conditions of nests and hence influence the nest bacterial environment. In the present study, we explored some predictions of this hypothetical scenario in the great spotted cuckoo (Clamator glandarius)–magpie (Pica pica) system of brood parasitism. Great spotted cuckoos visit the nests of their magpie hosts and frequently damage some of the host eggs when laying eggs or on subsequent visits. Therefore, it represents a good system for testing the effect of nest visitors on the bacterial environment of nests. In accordance with this hypothesis, we found that the bacterial load of magpie eggshells was greater in parasitized nests, which may suggest that brood parasitism increases the probability of bacterial infection of magpie eggs. Moreover, comparisons of bacterial loads of cuckoo and magpie eggs revealed that: (1) cuckoo eggshells harboured lower bacterial densities than those of their magpie hosts in the same nests and (2) the prevalence of bacteria inside unhatched eggs was higher for magpies than for great spotted cuckoos. These interspecific differences were predicted because brood parasitic eggs (but not host eggs) always experience the bacterial environments of parasitized nests. Therefore, the results obtained in the present study suggest that parasitic eggs are better adapted to environments with a high risk of bacterial contamination than those of their magpie hosts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 836–848.     

Differential proteomics of dehydration and rehydration in bryophytes: evidence towards a common desiccation tolerance mechanism

All bryophytes evolved desiccation tolerance (DT) mechanisms during the invasion of terrestrial habitats by early land plants. Are these DT mechanisms still present in bryophytes that colonize aquatic habitats? The aquatic bryophyte Fontinalis antipyretica Hedw. was subjected to two drying regimes and alterations in protein profiles and sucrose accumulation during dehydration and rehydration were investigated. Results show that during fast dehydration, there is very little variation in protein profiles, and upon rehydration proteins are leaked. On the other hand, slow dehydration induces changes in both dehydration and rehydration protein profiles, being similar to the protein profiles displayed by the terrestrial bryophytes Physcomitrella patens (Hedw.) Bruch and Schimp. and, to what is comparable with Syntrichia ruralis (Hedw.) F. Weber and D. Mohr. During dehydration there was a reduction in proteins associated with photosynthesis and the cytoskeleton, and an associated accumulation of proteins involved in sugar metabolism and plant defence mechanisms. Upon rehydration, protein accumulation patterns return to control values for both photosynthesis and cytoskeleton whereas proteins associated with sugar metabolism and defence proteins remain high. The current results suggest that bryophytes from different ecological adaptations may share common DT mechanisms.     

Production and morphology of fruit and seeds in Genisteae (Fabaceae) of south-west Spain

The productivity and morphology of fruit and seeds were studied in 30 species (and subspecies) of the tribe Genisteae (Fabaceae) in south-west Spain. The morphological characters of greatest taxonomic value both for the segregation of the two subtribes (Genistinae and Lupininae) recognized in Genisteae and for the delimitation of the lower taxonomic levels (genus and species) are the size of the pod and characters of the pericarp, the colour and weight of the seeds, whether or not an ad exists, and the shape, size, and position of the hilum. In contrast, characters of little taxonomic interest are pod colour, shape and number of seeds, and characters of the lens. There were also found to be major relationships between fruit and seed, and between these and other floral (e.g. corolla size) or reproductive (e.g. polledovule [P/O] and seed/ovule [S/O] ratios) attributes. Thus in this tribe, pod size was positively correlated with corolla size, seed size, the number of viable seeddfruit, and the S/O and P/O ratios. Corolla size was positively correlated with the number of viable seeds/ fruit and with the seed weight. Similarly, the number of seeddfruit was positively correlated with the fruit's weight and with the number of ovules/ovary. Also, the weight of the seeds was positively correlated with the pollen/ovule ratio. There was also positive correlation between the S/O and P/O ratios.     

Explant Orientation and Polarity Determine the Morphogenic Response of Epicotyl Segments of Troyer Citrange

The morphogenic pathway of adventitious bud and shoot regenerationat the ends of Troyer citrange epicotyl cuttings is determinedby polarity and explant orientation. In explants planted verticallywith the basal end inserted in the medium, bud formation atthe apical end occurs by direct organogenesis. Bud growth andsubsequent shoot formation is markedly increased by the additionof 6-benzyladenine (BA) to the medium. This growth regulatoralso increases the number of buds formed. When they come intocontact with the culture medium, both the apical end and thebasal end of the cuttings form a vigorous callus with many xyllaryelements, more numerous in the calli from the basal end. Inthese calli, buds differentiate by a process of indirect organogenesis.This indirect regeneration pathway requires the addition of6-benzyladenine to the medium, and the number of buds formedis higher at the apical end than at the basal end of the cuttings.This pathway of regeneration is reduced as the position of thecuttings during incubation deviates from the normal uprightvertical position. Thus, for the basal end of the cuttings,the number of buds and shoots formed is higher when the explantsare placed vertically than when they lie on the surface of themedium. For the apical end, this number is higher in explantsplaced horizontally than when inserted vertically in the mediumin an inverted position. Copyright 1999 Annals of Botany Company Troyer citrange, Citrus sinensis x Poncirus trifoliata, explant orientation, histology, hormone dependence, morphogenesis, organogenesis, polarity, xylogenesis.     

A RAPID BIOASSAY TO DETECT MYCOTOXINS USING A MELANIN PRECURSOR OVERPRODUCER MUTANT OF THE CILIATETETRAHYMENA THERMOPHILA

Four different mycotoxins (patulin, T-2 toxin, diacetoxyscirpenol and roquefortine) were used to study growth inhibitory effects on a melanin precursor overproducer mutant of the ciliateTetrahymena thermophilaThis strain is especially sensitive to diacetoxyscirpenol and T-2 toxin. The secretion capacity of melanin precursors into the culture medium by this mutant and its biosensor capacity are very useful characteristics to elaborate a rapid bioassay to detect some specific mycotoxins.     

Isolation of polymorphic microsatellite loci from the flea beetle Phyllotreta nemorum L. (Coleoptera: Chrysomelidae)

Ten microsatellite markers for the flea beetle Phyllotreta nemorum were developed using di‐ and trinucleotide repeat‐enriched libraries. Each of these primer pairs were characterized on 96 individuals. Expected heterozygosities ranged between 0.11 and 0.84 and the number of alleles ranged between two and 14 per locus. These microsatellite markers are the first published for any Phyllotreta species.     

Floral and reproductive biology of Drosophyllum lusitanicum (L.) Link (Droseraceae)

We studied the floral and reproductive biology of Drosophyllym lusitanicum (Droseraceae), a species endemic to the western Iberian Peninsula and northwest Morocco. Flowering lasted from March to August, peaking in April. The species is clearly homogamous, with pollen germination and stigma receptivity occurring even in preanthesis. This was reflected in the high rates of fruit set and seed set in bagged inflorescences. Fructification did not differ significantly between different pollination treatments, although we did find differences between some treatments in the numbers of viable seeds per flower and fruit. However, seed weight did not differ significantly. The importance of self-pollination over cross-pollination was also supported by the low percentages of fructification (24.67%) after emasculation and open pollination. Metameric deviations were seen in flowers, although this abnormality was not translated as any reproductive benefit or disadvantage (fructification, number or weight of seeds) in comparison with normal flowers.