Adjustment of growth, starch turnover, protein content and central metabolism to a decrease of the carbon supply when Arabidopsis is grown in very short photoperiods

Arabidopsis was grown in a 12, 8, 4 or 3 h photoperiod to investigate how metabolism and growth adjust to a decreased carbon supply. There was a progressive increase in the rate of starch synthesis, decrease in the rate of starch degradation, decrease of malate and fumarate, decrease of the protein content and decrease of the relative growth rate. Carbohydrate and amino acids levels at the end of the night did not change. Activities of enzymes involved in photosynthesis, starch and sucrose synthesis and inorganic nitrogen assimilation remained high, whereas five of eight enzymes from glycolysis and organic acid metabolism showed a significant decrease of activity on a protein basis. Glutamate dehydrogenase activity increased. In a 2 h photoperiod, the total protein content and most enzyme activities decreased strongly, starch synthesis was inhibited, and sugars and amino acids levels rose at the end of the night and growth was completely inhibited. The rate of starch degradation correlated with the protein content and the relative growth rate across all the photoperiod treatments. It is discussed how a close coordination of starch turnover, the protein content and growth allows Arabidopsis to avoid carbon starvation, even in very short photoperiods.     

Long-term survival despite low genetic diversity in the critically endangered Madagascar fish-eagle

The critically endangered Madagascar fish-eagle ( Haliaeetus vociferoides ) is considered to be one of the rarest birds of prey globally and at significant risk of extinction. In the most recent census, only 222 adult individuals were recorded with an estimated total breeding population of no more than 100–120 pairs. Here, levels of Madagascar fish-eagle population genetic diversity based on 47 microsatellite loci were compared with its sister species, the African fish-eagle ( Haliaeetus vocifer ), and 16 of these loci were also characterized in the white-tailed eagle ( Haliaeetus albicilla ) and the bald eagle ( Haliaeetus leucocephalus ). Overall, extremely low genetic diversity was observed in the Madagascar fish-eagle compared to other surveyed Haliaeetus species. Determining whether this low diversity is the result of a recent bottleneck or a more historic event has important implications for their conservation. Using a Bayesian coalescent-based method, we show that Madagascar fish-eagles have maintained a small effective population size for hundreds to thousands of years and that its low level of neutral genetic diversity is not the result of a recent bottleneck. Therefore, efforts made to prevent Madagascar fish-eagle extinction should place high priority on maintenance of habitat requirements and reducing direct and indirect human persecution. Given the current rate of deforestation in Madagascar, we further recommend that the population be expanded to occupy a larger geographical distribution. This will help the population persist when exposed to stochastic factors (e.g. climate and disease) that may threaten a species consisting of only 200 adult individuals while inhabiting a rapidly changing landscape.     

Sixteen new simple sequence repeat markers from Brassica juncea expressed sequences and their cross‐species amplification

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 16 expressed sequence tags (EST)‐SSR markers from Brassica juncea and their cross‐amplification across Brassica species. Sixteen primer pairs were assessed for polymorphism in all genomes of the diploid and amphidiploid Brassica species. The markers show reliable amplification, considerable polymorphism and high transferability across species, demonstrating the utility of EST‐SSRs for genetic analysis of brassicas.     

Identification and characterization of simple sequence repeat markers from Brassica napus expressed sequences

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 24 expressed sequence tags (EST)‐SSR markers from Brassica napus and their cross‐amplification across Brassica species. The markers show reliable amplification, genome specificity and considerable polymorphism, demonstrating the utility of EST‐SSRs for genetic analysis of wild Brassica populations and commercial Brassica germplasm.     

The effect of short-term weather fluctuations on temperatures inside lizard nests, and on the phenotypic traits of hatchling lizards

Can short‐term stochastic variation in local weather conditions modify the thermal conditions inside lizard nests, and thus (potentially) the developmental rates, hatching success, and phenotypic traits of hatchlings from these nests? This hypothesis requires that (i) natural nests are poorly buffered thermally, such that ambient regimes affect temperatures inside the nest, and (ii) short‐term thermal variations modify attributes of the offspring. Field data on natural nests of the sub‐alpine skink Bassiana duperreyi confirm the existence of this first effect, and laboratory experiments substantiate the latter. Exposure to warmer‐than‐usual temperatures for 2 wéeks during the 9‐ to 16‐wéek incubation period doubled hatching success, and significantly modified hatchling phenotypes (hatching dates, offspring size and locomotor performance). The proportion of development completed prior to this exposure influenced the degrée of response. Exposure to a brief ‘window’ of higher‐than‐usual temperatures soon after oviposition had more effect on hatching time, egg survival and hatchling phenotypes than if the exposure occurred later in development. Thus, minor variations in weather conditions during incubation may have substantial effects on reptile populations.     

Genetic variation and reproductive mode in populations of Simocephalus vetulus (Branchiopoda: Cladocera) from the East Midlands of England

SUMMARY. 1. Five populations of the cladoceran Simocephalus vetulus (O. F. Muller) examined by enzyme electrophoresis at four to five loci revealed high levels of genetic variation.
2. The one intermittent population had genotype frequencies in Hardy Weinberg equilibrium, the three permanent populations showed deviations from equilibrium of varying magnitude. The fifth population was fixed for a single clone, and was possibly recently derived from a single ephippial hatchling.
3. Laboratory breeding experiments confirmed that this species is a cyclic parthenogen.     

A NEW SPECIES OF THE WOMBAT WARENDJA FROM LATE MIOCENE DEPOSITS AT RIVERSLEIGH, NORTH-WEST QUEENSLAND, AUSTRALIA

Abstract:  A new species of the plesiomorphic wombat Warendja is described. Warendja encorensis sp. nov., the second species to be attributed to this genus, is known from a single fossil locality (Encore Site) at Riversleigh, north-west Queensland. Specimens of W. encorensis are limited to isolated teeth, two mandibular fragments and a maxillary fragment. Two molars preserve the unworn crown morphology. Encore Site has been estimated to be late Miocene in age, making these the only known specimens of Warendja to be clearly older than Pleistocene. Warendja encorensis is also the first described species of wombat from Miocene deposits to which hypselodont teeth have been attributed. It differs from W. wakefieldi in its larger size, distribution of enamel, and in details of the incisor and premolar morphology.