Quantitative historical change in bumblebee (Bombus spp.) assemblages of red clover fields

Background

Flower visiting insects provide a vitally important pollination service for many crops and wild plants. Recent decline of pollinating insects due to anthropogenic modification of habitats and climate, in particular from 1950''s onwards, is a major and widespread concern. However, few studies document the extent of declines in species diversity, and no studies have previously quantified local abundance declines. We here make a quantitative assessment of recent historical changes in bumblebee assemblages by comparing contemporary and historical survey data.

Methodology/Principal Findings

We take advantage of detailed, quantitative historical survey data from the 1930''s on bumblebee (Bombus spp.) abundances and species composition in red clover (Trifolium pratense) fields, an important floral resource and an attractant of all bumblebee species. We used the historical survey data as a pre-industrialization baseline, and repeated the same sampling protocol at nearly the same localities at present, hence setting up a historical experiment. We detected historical changes in abundances (bees/m²) of both workers (the “pollinatory units”) and queens (effective population size), in addition to species composition. In particular, long-tongued bumblebee species showed consistent and dramatic declines in species richness and abundances throughout the flowering season of red clover, while short-tongued species were largely unaffected. Of 12 Bombus species observed in the 1930''s, five species were not observed at present. The latter were all long-tongued, late-emerging species.

Conclusions/Significance

Because bumblebees are important pollinators, historical changes in local bumblebee assemblages are expected to severely affect plant reproduction, in particular long-tubed species, which are pollinated by long-tongued bumblebees.     

Quantification of the intra-plot correlation in plant abundance data: A possible test of the neutral theory

A method for summarising the degree of spatial covariance (intra-plot correlation) among different plant species using plant abundance data is presented. The method will provide an alternative test of the hypothesis of neutrality in uniform environments, and we apply it in this study to data derived from two different grasslands. There is a significant positive intra-plot correlation in both grasslands that may be due to either sampling effects or deterministic ecological effects. For the calcareous grassland, we also applied the method to a subset of plant species that are expected to be less influenced by sampling effects, and they also has a significant positive intra-plot correlation, which suggests that sampling effects are playing a minor role in the calcareous grassland as an explanation for the spatial aggregated of species. Overall, the results suggest that the deterministic ecological processes that do not contradict the neutral theory are more important than any possible deterministic ecological processes that contradict the neutral theory. Consequently, the hypothesis of neutrality could neither be rejected nor corroborated in the investigated grasslands. We suggest that the spatial aggregation in the sampled calcareous grassland is mainly caused by small local differences in abiotic factors or in the timing of gaps for recolonisation. This in turn may lead to different local niches (ecological adaptation or phenology of establishment from seeds) and possibly local exclusion of plant species by interspecific competition.     

Metabolism of palmitate in perfused rat liver. Effect of low and high ethanol concentrations at various concentrations of palmitate in the perfusion medium

1. The effect of ethanol on the metabolism of [1-(14)C]palmitate in rat liver was investigated in a single-pass perfusion system at concentrations of 10mm- or 80mm-ethanol and 0.2mm- or 1mm-palmitate. 2. After the perfusion the hepatic lipid was isolated in subcellular fractions. The two major fractions contained triacylglycerol from cytoplasmic lipid droplets and from endoplasmic reticulum plus Golgi apparatus respectively. 3. In experiments with 0.2mm-palmitate perfusion with 10mm- or 80mm-ethanol did not measurably increase the esterification, and the oxidation was markedly decreased and the fatty acid uptake was not affected. 4. Perfusion with ethanol, at 1mm-palmitate, increased the fatty acid uptake, increased esterification and decreased oxidation. The effects of 10mm- and 80mm-ethanol were similar. The incorporation of [1-(14)C]palmitate into triacylglycerol in cytoplasmic lipid droplets was not affected statistically significantly by ethanol. Ethanol increased the incorporation of [1-(14)C]palmitate into di- and tri-acylglycerol in the membranous fraction. Estimated chemically, the contents of di- and tri-acylglycerol were only slightly affected by ethanol. These results suggest that the effect of ethanol was to increase the turnover of fatty acids in triacylglycerol rather than to increase its accumulation. 5. The results indicate that an increased concentration of fatty acids is more important for the formation of acute fatty liver in fed rats than are the direct effects of ethanol on hepatic fatty acid metabolism.     

Phylogeny of Mysis (Crustacea, Mysida): history of continental invasions inferred from molecular and morphological data

We studied the phylogenetic history of opossum shrimps of the genus Mysis Latreille, 1802 (Crustacea: Mysida) using parsimony analyses of morphological characters, DNA sequence data from mitochondrial (16S, COI and CytB) and nuclear genes (ITS2, 18S), and eight allozyme loci. With these data we aimed to resolve a long‐debated question of the origin of the non‐marine (continental) taxa in the genus, i.e., “glacial relicts” in circumpolar postglacial lakes and “arctic immigrants” in the Caspian Sea. A simultaneous analysis of the data sets gave a single tree supporting monophyly of all continental species, as well as monophyly of the taxa from circumpolar lakes and from the Caspian Sea. A clade of three circumarctic marine species was sister group to the continental taxa, whereas Atlantic species had more distant relationships to the others. Small molecular differentiation among the morphologically diverse endemic species from the Caspian Sea suggested their recent speciation, while the phenotypically more uniform “glacial relict” species from circumpolar lakes (Mysis relicta group) showed deep molecular divergences. For the length‐variable ITS2 region both direct optimization and a priori alignment procedures gave similar topologies, although the former approach provided a better overall resolution. In terms of partitioned Bremer support (PBS), mitochondrial protein coding genes provided the largest contribution (83%) to the total tree resolution. This estimate however, appears to be partly spurious, due to the concerted inheritance of mitochondrial characters and probable cases of introgression or ancestral polymorphism. © The Willi Hennig Society 2005.     

Phylogeny of the Heelwalkers (Insecta: Mantophasmatodea) based on mtDNA sequences, with evidence for additional taxa in South Africa

We examined the phylogeny of Mantophasmatodea from southern Africa (South Africa, Namibia) using approx. 1300 bp of mitochondrial DNA sequence data from the genes encoding COI and 16S. The taxon sample comprised multiple specimens from eight described species (Namaquaphasma ookiepense, Austrophasma rawsonvillense, A. caledonense, A. gansbaaiense, Lobatophasma redelinghuysense, Hemilobophasma montaguense, Karoophasma botterkloofense, K. biedouwense) and four undescribed species of Austrophasmatidae; three specimens of Sclerophasma paresisense (Mantophasmatidae); and two specimens of Praedatophasma maraisi and one of Tyrannophasma gladiator (not yet convincingly assigned to any family). For outgroup comparison a broad selection from hemimetabolous insect orders was included. Equally weighted parsimony analyses of the combined COI+16S data sets with gaps in 16S scored as a fifth character state supported Austrophasmatidae and all species and genera of Mantophasmatodea as being monophyletic. Most species were highly supported with 98-100% bootstrap/7-39 Bremer support (BS), but K. biedouwense had moderate support (87/4) and A. caledonense low support (70/1). Mantophasmatodea, Austrophasmatidae, and a clade Tyrannophasma gladiator+Praedatophasma maraisi were all strongly supported (99-100/12-25), while relationships among the two latter clades and Mantophasmatidae remain ambiguous. Concerning the relationships among genera of Austrophasmatidae, support values are moderately high for some nodes, but not significant for others. We additionally calculated the partitioned BS values of COI and 16S for all nodes in the strict consensus of the combined tree. COI and 16S are highly congruent at the species level as well as at the base of Mantophasmatodea, but congruence is poor for most intergeneric relationships. In forthcoming studies, deeper relationships in the order should be additionally explored by nuclear genes, such as 18S and 28S, for a reduced sample of specimens.     

Phylogeny of the water strider genus Gerris Fabricius (Heteroptera: Gerridae) based on COI mtDNA, EF-1α nuclear DNA and morphology

Phylogenetic relationships between water striders (Heteroptera: Gerridae) of genus Gerris Fabricius were examined using molecular and morphological characters. The molecular dataset was 820 bp DNA from the 3′ half of the mitochondrial gene encoding cytochrome oxidase subunit I and 515 bp DNA from the nuclear gene encoding elongation factor 1 alpha. The morphological dataset was a slightly modified version of a previously published dataset. Representatives from all eight recognized species groups of Gerris, as well as six species from three related genera, including Gigantometra gigas, Limnoporus esakii, L. rufoscutellatus, Aquarius najas, A. conformis and A. paludum, were included. Unweighted parsimony analyses of the COI sequences gave a topology with strong support for only those nodes that were already recognized as closely related based on morphological characters. Similar analyses of EF‐1α gave a cladogram with a topology quite different from that based on morphology and COI. Unweighted parsimony analyses of the ‘total evidence’ dataset largely supports the traditional view of Gerris phylogeny. Finally, the implications of the reconstructed phylogeny in relation to biogeography and ecological phylogenetics of Gerris is discussed.     

Frequency-dependent fitness of hybrids between oilseed rape (Brassica napus) and weedy B. rapa (Brassicaceae)

Fitness of interspecific hybrids is sometimes high relative to their parents, despite the conventional belief that they are mostly unfit. F(1) hybrids between oilseed rape (Brassica napus) and weedy B. rapa can be significantly more fit than their weedy parents under some conditions; however, under other conditions they are less fit. To understand the reasons, we measured the seed production of B. napus, B. rapa, and different generations of hybrid plants at three different densities and in mixtures of different frequencies (including pure stands). Brassica napus, B. rapa, and backcross plants (F(1) ♀ × B. rapa) produced many more seeds per plant in pure plots than in mixtures and more seeds in plots when each was present at high frequency. The opposite was true for F(1) plants that produced many more seeds than B. rapa in mixtures, but fewer in pure stands. Both vegetative and reproductive interactions may be responsible for these effects. Our results show that the fitness of both parents and hybrids is strongly frequency-dependent and that the likelihood of introgression of genes between the species thus may depend on the numbers and densities of parents and their various hybrid offspring in the population.     

Possible Involvement of GABAA and GABAB Receptors in the Inhibitory Action of Lindane on Transmitter Release from Cerebellar Granule Neurons

Cerebellar granule cells in culture express receptors for GABA belonging to the GABA_A and GABA_B classes. In order to characterize the ability of the insecticide lindane to interact with these receptors cells were grown in either plain culture media or media containing 150 M THIP as this is known to influence the properties of both GABA_A and GABA_B receptors. It was found that lindane regardless of the culture condition inhibited evoked (40 mM K⁺) release of neurotransmitter ([³H]D-aspartate as label for glutamate). In naive cells both GABA_A and GABA_B receptor active drugs prevented the inhibitory action of lindane but in THIP treated cultures none of the GABA_A and GABA_B receptor active drugs had any effect on the inhibitory action of lindane. This lack of effect was not due to inability of baclofen itself to inhibit transmitter release. It is concluded that lindane dependent on the state of the GABA_A and GABA_B receptors is able to indirectly interfere with both GABA_A and GABA_B receptors. In case of the latter receptors it was shown using [³H]baclofen to label the receptors that lindane could not displace the ligand confirming that lindane is likely to exert its action at a site different from the agonist binding site.