Further Investigations of Liposoluble Fluorescent Compounds in Senescing Plant Cells

The accumulation of liposoluble fluorescent compounds with excitationand emission fluorescent maxima in the bands of 350–370nm and 410–440 nm respectively has been observed in thedegrading (the late stationary phase) blue-green algae Anabaenavariabilis K?tz and Anabaena cylindrica Lemm. cells, in thedark-senescing cotyledons from Phaseolus vulgaris L., and inmore than 1-year-old leaves of evergreen plants (Ligustrum japonicumThunb. and Osmanthus fortunei Carr.)- Spectral and chromatographicproperties of the compounds are rather similar to those previouslydescribed in the cells of other senescing plant species. Therole of lipid peroxidation in the formation of fluorescent pigmentsand in the ageing of plant cells is discussed. Key words: Fluorescent pigment, Anabaena sp, Senescence     

Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet bauxite mine,Romania

Abstract: We revisit a small but extremely significant collection of bird and pterosaur bones from the Lower Cretaceous (Berriasian) of western Romania. These fossils were collected in the late 1970s and early 1980s from a Lower Cretaceous (Berriasian) conglomerate lens deep in a bauxite mine at Cornet, close to the city of Oradea, Romania, and they caused a sensation when first described. Some fossils were initially ascribed to the early bird genus Archaeopteryx as well as to the modern clade Neornithes, an astonishing avian assemblage if correct. Described pterosaurs include dsungaripterids and a cervical vertebra that is likely the oldest azhdarchid pterosaur known from Europe and perhaps the world. Not only does the Cornet azhdarchid support an Eurasian origin for this clade, it is also significant because of its size: it is one of the smallest representatives of this pterosaur clade yet reported. Aside from their phylogenetic affinities, these unique Romanian fossils are also important because of their age; in particular, very few birds are known globally from the earliest Cretaceous. Re‐examination of collections in Oradea confirms the presence of both birds and pterosaurs in the Cornet bauxite: although the fragmentary bird remains are mostly indeterminate, one record of a hesperornithiform is confirmed. There is no evidence for Archaeopteryx at the Cornet site while the two supposed neornithines (Palaeocursornis biharicus Kessler and Jurcsák and Eurolimnornis corneti Kessler and Jurcsák) are based on undiagnostic remains and are here regarded as nomina dubia.     

Evidence for the transfer of a soil‐borne contaminant from plants to ants via an aphid mediator

1. Uptake of environmental contaminants by lower trophic groups can have negative effects on higher trophic groups. This study tested the ability of selenium, an environmental contaminant found in high concentrations throughout the tissues of certain accumulating plants, to be transferred to ants via aphid tissue and honeydew. 2. Plants of the selenium accumulator, Raphanus sativus (wild radish), were watered with three different selenium treatments (0, 0.25 or 0.5 µg Se ml^?1). Aphids, Myzus persicae, and Argentine ant colonies, Linepithema humile, were added to each caged plant and allowed to interact freely. Ant colonies were supplemented with one of three different food options to encourage the consumption of aphids, aphid honeydew, or aphids and honeydew. 3. The accumulation of selenium by each trophic group and a trophic transfer factor (TTF) was calculated. The TTF for plants to aphids was > 1, indicating biomagnification, whereas the TTF for aphids to worker ants was < 1, indicating only biotransfer. Accumulated levels by worker ants did not statistically differ as a result of diet. 4. The amounts of selenium acquired by ants as a factor of diet and caste were compared. Plants, aphids and worker ants accumulated selenium in a dose‐dependent manner. Ant queens did not contain detectable amounts of selenium. Honeydew contained comparable amounts of selenium to plant selenium levels. 5. Access to toxic compounds via honeydew and insect protein may have negative effects on the range expansion of invasive species, such as the Argentine ant.     

Effective population size and evolutionary dynamics in outbred laboratory populations of Drosophila

Census population size, sex-ratio and female reproductive success were monitored in 10 laboratory populations of Drosophila melanogaster selected for different ages of reproduction. With this demographic information, we estimated eigenvalue, variance and probability of allele loss effective population sizes. We conclude that estimates of effective size based on gene-frequency change at a few loci are biased downwards. We analysed the relative roles of selection and genetic drift in maintaining genetic variation in laboratory populations of Drosophila. We suggest that rare, favourable genetic variants in our laboratory populations have a high chance of being lost if their fitness effect is weak, e.g. 1% or less. However, if the fitness effect of this variation is 10% or greater, these rare variants are likely to increase to high frequency. The demographic information developed in this study suggests that some of our laboratory populations harbour more genetic variation than expected. One explanation for this finding is that part of the genetic variation in these outbred laboratory Drosophila populations may be maintained by some form of balancing selection. We suggest that, unlike bacteria, medium-term adaptation of laboratory populations of fruit flies is not primarily driven by new mutations, but rather by changes in the frequency of preexisting alleles.     

Trypanosoma cruzi from the Paraguayan Chaco: Isoenzyme Profiles of Strains Isolated at Makthlawaiya1

At Makthlawaiya, in the Paraguayan Chaco, the prevalence of Trypanosoma (Schizotrypanum) cruzi infection among both domestic Triatoma infestans and domestic dogs was 38%, and IgG anti-T. cruzi antibody was detected by the quantitative enzyme-linked immunosorbent assay (ELISA) in 80% (105/133) of human sera. Ninety percent (25/28) of T. cruzi strains isolated from both T. infestans and dogs showed heterozygous isoenzyme profiles for glucose phosphate isomerase, phosphoglucomutase and 6-phosphogluconate dehydrogenase. These strains appeared to be closely related to Bolivian zymodeme 2. Three Paraguayan T. cruzi strains showed homozygous isoenzyme profiles, similar to those of major Brazilian zymodemes. It was concluded that T. cruzi strains with heterozygous isoenzyme profiles predominate in domestic transmission cycles in this highly endemic area of the Paraguayan Chaco.     

Biological disjunction along the West Caledonian fault,New Caledonia: a synthesis of molecular phylogenetics and panbiogeography

This paper documents a newly discovered pattern of biological disjunction between NW and SE New Caledonia. The disjunction occurs in 87 (mapped) taxa, including plants, moths and lizards, and correlates spatially with the West Caledonian fault. This fault is controversial; some geologists interpret it as a major structure, others deny that it exists. It may have undergone 150–200 km of lateral movement and it is suggested that this has caused the biological disjunction by pulling populations apart. The disjunction matches similar dextral disjunctions of taxa along transform faults in New Zealand, New Guinea, California and Indonesia. Major biogeographic patterns – whether centres of diversity, boundaries of allopatric taxa or disjunctions – all include taxa with many different degrees of differentiation. Studies using a clock model of evolution will therefore interpret a biogeographic pattern as the result of many disparate events. However, this line of reasoning reaches the untenable conclusion that biogeographic patterns, including normal allopatry, are always caused by chance dispersal, never by vicariance. A more productive approach, avoiding the pitfalls of a fossil‐based molecular clock, involves a close examination of molecular clades, comparative biogeography and tectonics. The New Caledonia example documented here shows that this can lead to novel, testable predictions. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 470–488.