Duthieeae,a new tribe of grasses (Poaceae) identified among the early diverging lineages of subfamily Pooideae: molecular phylogenetics,morphological delineation,cytogenetics and biogeography

The phylogeny of Pooideae, one of the largest subfamilies of grasses, has been intensively studied during the past years. To investigate the early evolutionary splits in Pooideae we used a broad sample of genera with uncertain placement, some of which have not been studied in molecular phylogenetics before, complemented by representatives from other lineages of this subfamily. Morphological, cytogenetic and biogeographical analyses were added to the molecular sequence work on chloroplast matK–3’trnK and nuclear ITS. According to chloroplast DNA data, a new and well-supported lineage was identified among the early branches. It consisted of Phaenosperma and a larger group of genera encompassing Anisopogon, Danthoniastrum, Duthiea, Metcalfia, Pseudodanthonia (inclusion resting on ITS and morphology), Sinochasea and Stephanachne. Based on structural characters we suggest to keep Phaenosperma under the monotypic tribe Phaenospermateae and to accommodate the other genera under a new tribe Duthieeae, which is morphologically well-defined by synapomorphic spikelet features. Megalachne and Podophorus were not part of the early diverging Pooideae lineages but belong to the Aveneae/Poeae complex. Morphological characteristics of Duthieeae are discussed with respect especially to Stipeae and reveal consistent differences between both tribes. The genera of Duthieeae and the major lineages of Stipeae are keyed. A cytogenetic survey of exemplary taxa corroborates high chromosome base numbers as prevailing within the early diverging lineages of Pooideae, but chromosome sizes are more highly varied than previously reported. Ecogeographical analyses point to warm and humid conditions as the ancestral bioclimatic niche of Phaenosperma and Duthieeae, whereas adaptation to cold and drought occurred only in a part of Duthieeae but was obviously less successful than in the widespread and much more species-rich tribe Stipeae. The distribution of Duthieeae with species-poor or monotypic genera in mountains of the northern hemisphere and Anisopogon as an outlier in Australia suggests relict character.     

Dermal armour histology of aetosaurs (Archosauria: Pseudosuchia), from the Upper Triassic of Argentina and Brazil

Cerda, I.A. & Desojo, J.B. 2010: Dermal armour histology of aetosaurs (Archosauria: Pseudosuchia), from the Upper Triassic of Argentina and Brazil. Lethaia, Vol. 44, pp. 417–428. One of the most striking features documented in aetosaurs is the presence of an extensive bony armour composed of several osteoderms. Here, we analyse the bone microstructure of these elements in some South American Aetosaurinae aetosaurs, including Aetosauroides scagliai. In general terms, Aetosaurinae osteoderms are compact structures characterized by the presence of three tissue types: a basal cortex of poorly vascularized parallel‐fibred bone tissue, a core of highly vascularized fibro‐lamellar bone, and an external cortex of rather avascular lamellar bone tissue. Sharpey’s fibres are more visible at the internal core, toward the lateral margins and aligned parallel to the major axis of the dermal plate. No evidence of metaplastic origin is reported in the osteoderms, and we hypothesize an intramembranous ossification for these elements. The bone tissue distribution reveals that the development of the osteoderm in Aetosaurinae starts in a position located medial to the plate midpoint, and the main sites of active osteogenesis occur towards the lateral and medial edges of the plate. The osteoderm ornamentation is originated and maintained by a process of resorption and redeposition of the external cortex, which also includes preferential bone deposition in some particular sites. Given that no secondary reconstruction occurs in the osteoderms, growth marks are well preserved and they provide very important information regarding the relative age and growth pattern of Aetosaurinae aetosaurs. □Aetosauria, Aetosauroides, Archosauria, bone microstructure, integumentary skeleton, osteoderm.     

Biomass export of salamanders and anurans from ponds is affected differentially by changes in canopy cover

1. Previous research shows that canopy‐associated shifts from an algal to a detritus‐based food web can affect anuran tadpoles negatively. This may not be true of salamander larvae, however, because they are predators. 2. To investigate the influence of canopy cover on the survival and growth of salamanders, and on the subsequent export of biomass from ponds, we conducted a mesocosm experiment examining effects of shading (high or low) and litter (leaves or grass) on Ambystoma maculatum (a forest specialist) and A. texanum (a habitat generalist). Additionally, we reanalysed data from Williams, Rittenhouse & Semlitsch (2008) to examine the effects of shading and litter on biomass export of three anurans: Rana sphenocephala, Pseudacris crucifer and Hyla versicolor. 3. In contrast to previous studies, we found that salamanders performed better in mesocosms with the characteristics of closed canopy ponds (high shade and leaf litter), which resulted in a greater export of biomass. Salamanders grew larger under closed canopy conditions, probably because of differences in prey abundance among treatments. Anurans responded differently to canopy cover than caudates. The biomass export of R. sphenocephala and P. crucifer was reduced under closed canopy conditions (although differently affected by litter and shading), while the biomass of H. versicolor was not affected. 4. This and other studies suggest that changes in canopy cover may induce a shift in the amphibians emerging from ponds, from primarily anurans in open canopy ponds to primarily salamanders in closed canopy ponds. Additional multispecies studies will determine whether these trends hold true for more diverse amphibian assemblages. Further investigation into the effects of canopy cover on salamanders will be important for understanding aquatic–terrestrial linkages.     

Feeding response of a benthic copepod to ciliate prey type,prey concentration and habitat complexity

1. Protozoans are important consumers within microbial food webs and, in turn, they represent potential prey for small metazoans. However, feeding interactions within these food webs are rarely characterised and this is especially true for freshwater sediments. 2. We aimed to quantify the feeding links between a freshwater meiofaunal copepod and ciliates in two laboratory experiments. The first experiment addressed the response of Eucyclops serrulatus towards ciliate density and type (two ciliate species of the same genus differing in terms of body size). A second experiment assessed the effect of habitat structure on feeding rates by introducing different structural complexity into the feeding arena. In contrast to the first experiment, which was run only for one time period, this experiment also tested three different total feeding times (4, 7 and 9 h). 3. Eucyclops serrulatus exhibited high ingestion rates, with 3–69 ciliates copepod^?1 h^?1 consumed depending on food concentration, food type and habitat complexity. Copepods exhibited a preference for the smaller ciliate when total ciliate concentration was low, but selected both ciliates equally when food concentrations were medium or high. However, at very high food concentration, Eucyclops preferred the larger ciliate (which was 1/3 of its own body size), suggesting that the longer handling times of the larger prey are rewarding when the large prey is present in high numbers. In terms of total numbers consumed, copepods fed on more small ciliates, but in terms of carbon units both ciliates were selected equally when total prey concentration was low or medium. However, copepods derived more carbon from the larger prey at high and very high prey concentrations (up to 0.7 μgC out of a maximum of 1.1 μgC copepod^?1 h^?1). Habitat complexity influenced the feeding of copepods when it was observed over time. 4. The copepod–ciliate link is well known from the pelagic zone of both marine and freshwater habitats. We have shown its potential importance within the benthos, where it can be influenced by food identity, food quantity and possibly by habitat complexity.     

How do predator-induced changes affect prey vulnerability? Larvae of Chaoborus flavicans (Diptera: Chaoboridae) feeding on Daphnia pulex (Crustacea: Cladocera)

1. The relative food consumption and prey preferences of fourth-instar larvae of the phantom midge Chaoborus flavicans were investigated in laboratory experiments. Neonates and second instars of two clones of the cladoceran Daphnia pulex - an Arctic and an European clone - were offered to the predatory larvae. Each clone was divided into two groups: one group was exposed to the midge larvae during embryogenesis, whereas the other was not exposed to the predator. 2. While both exposed and unexposed neonates of the European clone had neck teeth, animals of the Arctic clone did not develop these spines. 3. A consistent rank order was observed in the vulnerability of the four prey types. Newborn daphnids from the Arctic clone were more vulnerable to predation than those from the European clone. Moreover, differences existed within each clone, regardless of neck teeth induction: Daphnia previously exposed to Chaoborus were less susceptible to the predators than unexposed prey. 4. The results show differences in the vulnerability of exposed and unexposed neonates that are not caused by the presence or absence of neck teeth. Perhaps the reduced vulnerability of exposed neonates was due to predator-avoidance behaviours.     

The Detection of Microbial Spoilage in Canned Foods Using Thin-layer Chromatography

Thin-layer chromatography was investigated as an inexpensive alternative to traditional microbiological techniques for the detection of microbial growth in canned vegetables. It was compared with culture methods, pH determination and direct microscopy in batches of canned vegetables with a known incidence of spoilage.     

The Boundary Layer over a Populus Leaf

Air flow over a Populus leaf was investigated using a hot-wireanemometer. When the air flow in the wind tunnel was laminar,the boundary layer was often turbulent at a wind speed of only1.5 m s^–1, particularly when encouraged by uneven topographyand roughness of the surface, as on the lower side of the leaf.The smoother upper surface behaved in a similar way to a flatplate when at low wind speeds, and the profiles of wind speedcould be shown to be equivalent to those expected from laminarboundary layer theory. Nevertheless, the boundary layer becameturbulent at Reynolds numbers much lower than those requiredto cause the transition to turbulence in a flat plate. Turbulentair flow in the wind tunnel greatly increased boundary layerturbulence but had only a small effect on evaporation from amodel of the leaf. The evaporation rates observed were 2.5 timeshigher than expected from theory, irrespective of the turbulenceregime.     

BIODIVERSITY AND CONSERVATION OF FRESHWATER FISH IN HONG KONG, CHINA

Hong Kong Special Administrative Region,China,has an area of1095km2and is located at the edge of thenorthern tropical zone.The landscape is dominated byhills and ravines withflat landrestrictedtothe lowflood-plains and coastal regions.Inthis hilly domain,the smallrocky streams are typically fast flowing at their uplandsources,and graduallyreduceinspeed asthey wind alonghill cuttings to reach the lowlands.While streams arecommonlyfound,rivers are very limited in number.Thefewlong and meanderi…     

The Effect of Glucose on the Biochemical and Ultrastructural Characteristics of Developing Euglena Chloroplasts*

SYNOPSIS. Chloroplast development is inhibited in Euglena gracilis strain Z, when greened in a medium containing glucose. This inhibition is reflected not only in the pattern of chlorophyll accumulation but also in the chloroplast ultrastructure and activities of the 2 light reactions of photosynthesis. Chloroplasts of cells greening in the presence of glucose are delayed in déveloping certain structures. Photosystem I activity develops at about the same rate as that of the controls during the first 48 h of greening, after which it develops at a slower rate. The rate of development of photosystem II activity in cells greening in a glucose medium lags considerably behind that of the controls until the later hours of greening. There are similarities between glucose inhibition and chloramphenicol inhibition of chloroplast development. Glucose may inhibit a step in chloroplast development ultimately controlled by the chloroplast genome.     

Effects of the maternal and pre‐adult host plant on adult performance and preference in the pea aphid,Acyrthosiphon pisum

Abstract 1. The taxon known as the pea aphid, Acyrthosiphon pisum, is composed of a series of host plant associated populations and is widely used as a model system to explore ecological speciation and the evolution of specialisation. It is thus important to know how maternal and pre‐adult experience influences host plant utilisation in this species. 2. The relative importance of the maternal and pre‐adult host plant for adult fecundity and host preference was investigated using three aphid clones collected from Lathyrus pratensis and maintained on Lathyrus or Vicia faba. 3. No significant effects of the maternal host plant on offspring fecundity were detected. 4. The host plant on which the aphid grew up influenced adult fecundity, although in a complex way that depended on both the adult host plant species and when after transfer to the test plant fecundity was assessed. 5. All three clones preferred to colonise Lathyrus over Vicia, and this preference was stronger for aphids raised on Lathyrus. 6. The significance of the results for studies of the evolution of specialisation and speciation that employ A. pisum is discussed.