Extensive intraspecific variation in a Triassic ammonoid from Siberia

The ammonoid species Czekanowskites rieberin.sp . from the Lower Anisian of Arctic Siberia (River Olenek) shows an enormous range of intraspecific variability. The 700 investigated specimens are packed in one single concretion. They are all adult with preserved living chambers and apertural structures. Morphologically they range from keeled smooth suboxycones with narrow umbilicus, through feebly ribbed platycones with a little wider umbilicus, to subcadicones with relatively wide umbilicus and straight ribs with bullae. The morphological variation is continuous; all specimmh belong to a single genetically linked population, variants of one biospecies. This phenomenon, which is quite common in boreal Triassic ammonoid faunas, has in the past led to serious taxonomic oversplitting. It presents a serious challenge to current ideas about a close correlation between modeof life and shell morphology in arnmonoids.□ Amntonoidea, boreal Triassic, ecology. Siberia, variability .     

Projected changes in elevational distribution and flight performance of montane Neotropical hummingbirds in response to climate change

The hovering flight of hummingbirds is one of the most energetically demanding forms of animal locomotion and is influenced by both atmospheric oxygen availability and air density. Montane Neotropical hummingbirds are expected to shift altitudinally upwards in response to climate change to track their ancestral climatic regime, which is predicted to influence their flight performance. In this study, we use the climate envelope approach to estimate upward elevational shifts for five Andean hummingbird species under two climate change scenarios. We then use field‐based data on hummingbird flight mechanics to estimate the resulting impact of climate change on aerodynamic performance in hovering flight. Our results show that in addition to significant habitat loss and fragmentation, projected upwards elevational shifts vary between 300 and 700 m, depending on climate change scenario and original mean elevation of the target species. Biomechanical analysis indicates that such upwards elevational shifts would yield a～2–5° increase in wing stroke amplitude with no substantial effect on wingbeat frequency. Overall, the physiological impact of elevational shifts of <1000 m in response to climate change is likely to be small relative to other factors such as habitat loss, changes in floristic composition, and increased interspecific competition.     

Hidden Wolbachia diversity in field populations of the European cherry fruit fly, Rhagoletis cerasi (Diptera, Tephritidae)

The European cherry fruit fly Rhagoletis cerasi has been a field model for cytoplasmic incompatibility since the mid 1970s. Two Wolbachia strains were detected in this tephritid species and w Cer2 was described as the CI inducing agent dividing European populations into two unidirectional incompatible groups, i.e. southern females produce viable offspring with northern males, whereas the reciprocal cross results in incompatibility. We detected three new Wolbachia strains by sequencing a multitude of plasmids derived from Wolbachia surface protein gene ( wsp ) polymerase chain reaction (PCR) products. Strain-specific primers were developed allowing individual diagnosis without need for cloning. Hybridization of specific PCR products with a wsp oligonucleotide enhanced the detection limit significantly and revealed the presence of low-titre infections in some strains, in different ontogenetic stages and in adults of different age. We then performed a survey of strain prevalence and infection frequency in eight European regions. w Cer1 was fixed in all populations, whereas w Cer2 was detected only in the South. w Cer3 frequency was the lowest without a clear distribution pattern. The abundance of w Cer4 was homogenous across Europe. Like w Cer2, w Cer5 showed significant differences in spatial distribution. Our new findings of previously undetected and recombinant Wolbachia strains in R. cerasi reveal a major caveat to the research community not to overlook hidden Wolbachia diversity in field populations. Low-titres and geographical variability in Wolbachia diversity are expected to influence the outcome of Wolbachia population dynamics and Wolbachia- based insect population control and may create invasion barriers for expanding and artificially introduced Wolbachia strains.     

Identification of calcified coccoid cyanobacteria forming stromatoporoid stromatolites

A simple technique is described enabling the identification in scanning electron micrographs (SEM) of combined Iractured and etched stromatoporoid sections, the cyanobacteria-hkc coccoid aggregates building the entire stromatoporoid structure. The coccoid aggregates from stromatoporoids are closely related to extant calcified coccoid cyanobacteria (Plcurocapsales) forming stromalolitic mats in Laguna Mormona (Baja California) and Sabkha Gavish (Sinai). Stromatoporoids, stromatolites, cyanobacteria.     

Transketolase from Cyanophora paradoxa: In Vitro Import into Cyanelles and Pea Chloroplasts and a Complex History of a Gene Often, But Not Always, Transferred in the Context of Secondary Endosymbiosis

ABSTRACT. The glaucocystophyte Cyanophora paradoxa is an obligatorily photoautotrophic biflagellated protist containing cyanelles, peculiar plastids surrounded by a peptidoglycan layer between their inner and outer envelope membranes. Although the 136-kb cyanelle genome surpasses higher plant chloroplast genomes in coding capacity by about 50 protein genes, these primitive plastids still have to import >2,000 polypeptides across their unique organelle wall. One such protein is transketolase, an essential enzyme of the Calvin cycle. We report the sequence of the pre-transketolase cDNA from C. paradoxa and in vitro import experiments of precursor polypeptides into cyanelles and into pea chloroplasts. The transit sequence clearly indicates the localization of the gene product to cyanelles and is more similar to the transit sequences of the plant homologues than to transit sequences of other cyanelle precursor polypeptides with the exception of a cyanelle consensus sequence at the N-terminus. The mature sequence reveals conservation of the thiamine pyrophosphate binding site. A neighbor-net planar graph suggests that Cyanophora , higher plants, and the photosynthetic protist Euglena gracilis acquired their nuclear-encoded transketolase genes via endosymbiotic gene transfer from the cyanobacterial ancestor of plastids; in the case of Euglena probably entailing two transfers, once from the plastid in the green algal lineage and once again in the secondary endosymbiosis underlying the origin of Euglena's plastids. By contrast, transketolase genes in some eukaryotes with secondary plastids of red algal origin, such as Thalassiosira pseudonana , have retained the pre-existing transketolase gene germane to their secondary host.     

Temporal environmental change, clonal physiology and the genetic structure of a Daphnia assemblage (D. galeata–hyalina hybrid species complex)

1. In a combined field and laboratory study, seasonal relationships between water temperature and oxygen content, genetic structure (composition of MultiLocus Genotypes, MLGs) of a Daphnia assemblage (D. galeata–hyalina hybrid species complex), and the physiological properties of clones of frequent MLGs were studied. In accordance with the oxygen‐limited thermal tolerance hypothesis, essential physiological variables of oxygen transport and supply were measured within the tolerable temperature range. 2. A few MLGs (types T1–T4) were frequent during early spring and late autumn at surface temperatures below 10 °C. Clones of T1–T4 showed a low tolerance towards higher temperatures (above 20 °C) and a high phenotypic plasticity under thermal acclimation in comparison to clones derived from frequent MLGs from later seasons, and stored high–medium quantities of carbohydrates at 12 and 18 °C. 3. Another MLG (T6) succeeded the MLGs T1–T4. T6 was frequent over most of the year at temperatures above 10 °C and below 20 °C. A clone derived from T6 exhibited a high tolerance towards warm temperatures and a more restricted phenotypic plasticity. It stored high–medium quantities of carbohydrates at 12, 18 and 24 °C and showed a high capacity for acclimatory adjustments based on haemoglobin expression. 4. During the summer period at temperatures ≥20 °C, the MLG T6 was found mainly near to the thermocline, where temperature and oxygen content were distinctly lower, and to a lesser extent in surface water. At the surface, another MLG (T19) was predominant during this period. A clone of this MLG showed a very high tolerance towards warm temperatures, minimal phenotypic plasticity, low carbohydrate stores and a high capacity for circulatory adjustments to improve oxygen transport at higher temperatures. 5. This study provides evidence for connections between the spatio‐temporal genetic heterogeneity of a Daphnia assemblage and the seasonal changes of water temperature and oxygen content. The data also suggest that not only the actual temperature but also the dynamics of temperature change may influence the genetic structure of Daphnia populations and assemblages.