Disproportional risk for habitat loss of high‐altitude endemic species under climate change

The expected upward shift of trees due to climate warming is supposed to be a major threat to range‐restricted high‐altitude species by shrinking the area of their suitable habitats. Our projections show that areas of endemism of five taxonomic groups (vascular plants, snails, spiders, butterflies, and beetles) in the Austrian Alps will, on average, experience a 77% habitat loss even under the weakest climate change scenario (+1.8 °C by 2100). The amount of habitat loss is positively related with the pooled endemic species richness (species from all five taxonomic groups) and with the richness of endemic vascular plants, snails, and beetles. Owing to limited postglacial migration, hotspots of high‐altitude endemics are situated in rather low peripheral mountain chains of the Alps, which have not been glaciated during the Pleistocene. There, tree line expansion disproportionally reduces habitats of high‐altitude species. Such legacies of climate history, which may aggravate extinction risks under future climate change have to be expected for many temperate mountain ranges.     

Larval food composition affects courtship song and sperm expenditure in a lekking moth

1. Variation in larval food composition can have far‐reaching effects on the adult phenotype of insects. To maximise reproductive output, it is therefore beneficial if insects are able to plastically adapt to nutritional cues in their larval diet. 2. The expression of sexual traits implicated in pre‐ and postcopulatory sexual selection of the lesser wax moth, Achroia grisella Fabricius, across different rearing environments of varying diet composition was investigated. 3. Moths reared on diet with relatively low amounts of carbohydrate, but more protein and fats, had lower survival rates, decreased body mass, and longer development times. Males reared on this diet produced songs with higher pulse pair rates (which are attractive to females) and transferred more sperm per copulation than males reared on the alternative diets. 4. There was no evidence for a trade‐off between pre‐ and postcopulatory traits. Interestingly, individuals with both higher pulse pair rates and more transferred sperm came from the treatment group with higher mortality rates and generally poorer development. The present results suggest that both of these sexual characteristics are developmentally plastic, but that only moths reared on the protein‐rich diet were able to benefit from this plasticity.     

Responses to features of the calling song by ascending auditory interneurones in the cricket Gryllus campestris

ABSTRACT. In female Gryllus campestris L., three functional types of ascending auditory intemeurones have been studied by recording from them extracellularly in the split cervical connectives using suction electrodes. Type 1 neurones are characterized by an optimal sensitivity to the carrier frequency of the species calling song (4–5 kHz). They copy the syllable and pause structure of the call at all intensities. The patterned spike discharge is observable at least 8 dB above absolute threshold. With suprathreshold stimulation, the neurones exhibit maximal responses (number of spikes/chirp) around the carrier frequency. The intensity response curves are approximately linear in the range of 40–90 dB SPL. The envelope of each syllable is reflected by a corresponding change in the firing rate, and syllable periods of 24ms and longer are resolved. This type can be considered as a neural correlate for phonotactic behaviour of the female where the syllable period has been found to be the most important temporal parameter. Type 2 neurones are most sensitive in the range of 4–6 and 11–13 kHz. They copy the syllable and pause structure of the species calling song at low and moderate intensities. However, the spikes invade the intersyllable pauses, when stimulated with the calling song at higher intensities (above 85 dB). This is particularly apparent at the onset of a chirp series. The slope of the intensity—response curve mimics that of type 1 units. The neurones cannot follow syllable periods shorter than 32 ms. Type 3 neurones differ from types 1 and 2 by a rather broad-band sensitivity in the range of 3–16 kHz, and in copying the chirp as a whole. Even at low stimulus intensities, the intersyllable pauses are filled with spikes, and information about the syllable—pause structure is lost. Stimulation with suprathreshold intensities gives rise to a rather uniform, broad-band response without distinctive peaks. The intensity—response curve is characterized by a higher absolute threshold, and by the reduction in the response magnitude starting above 70–80 dB. These units are not suitable for copying the calling song temporal structure in detail, but would indicate the chirping rhythm. Their strong response in the range of the species courtship song carrier frequency make them suitable to copy the courtship song.     

Cultivation of a perennial grass for bioenergy on a boreal organic soil – carbon sink or source?

The area under the cultivation of perennial bioenergy crops on organic soils in the northern countries is fast increasing. To understand the impact of reed canary grass (RCG, Phalaris arundinaceae L.) cultivation on the carbon dioxide (CO₂) balance of an organic soil, net ecosystem CO₂ exchange (NEE) was measured for four years in a RCG cultivated cutover peatland in eastern Finland using the eddy covariance technique. There were striking differences among the years in the annual precipitation. The annual precipitation was higher during 2004 and 2007 and lower during 2005 and 2006 than the 1971–2000 regional mean. During wet growing seasons, moderate temperatures, high surface soil moisture and low evaporative demand favoured high CO₂ uptake. During dry seasons, owing to soil moisture and atmospheric stress, photosynthetic activity was severely restricted. The CO₂ uptake [gross primary productivity (GPP)] was positively correlated with soil moisture, air temperature and inversely with vapour pressure deficit. Total ecosystem respiration (TER) increased with increasing soil temperature but decreased with increasing soil moisture. The relative responses of GPP and TER to moisture stress were different. While changes in TER for a given change in soil moisture were moderate, variations in GPP were drastic. Also, the seasonal variations in TER were not as conspicuous as those in GPP implying that GPP is the primary regulator of the interannual variability in NEE in this ecosystem. The ecosystem accumulated a total of 398 g C m^?2 from the beginning of 2004 until the end of 2007. It retained some carbon during a wet year such as 2004 even after accounting for the loss of carbon in the form of harvested biomass. Based on this CO₂ balance analysis, RCG cultivation is found to be a promising after‐use option on an organic soil.     

Half-Life of sRNA from Primary Roots of Zea mays. A Contribution to the Cytokinin Production

Roots produce cytokinins, which could be generated from the catabolism of transfer RNA. To prove such a hypothesis, the half-life of sRNA from primary roots of corn was measured. The shortest half-life was estimated to be 3 days. Depending on growth, cells at the root tips are “moving” out of the growing region and become differentiated cells. Therefore the highest label at the root tip during the pulse incubation is moving backwards during the chase incubation. Prolonged chase increases the half-life of sRNA successively, possibly due to decreasing metabolic activities of the originally labeled cells.     

Shaking the Diptera tree of life: performance analysis of nuclear and mitochondrial sequence data partitions

The value of mitochondrial versus nuclear gene sequence data in phylogenetic analysis has received much attention without yielding definitive conclusions. Theoretical arguments and empirical data suggest a lower phylogenetic utility than equivalent nuclear gene sequences, but there are many examples of important progress made using mitochondrial sequences. We undertook a systematic performance analysis of mitochondrial and nuclear sequence partitions taken from a representative sample of dipteran species. When analysed alone, mitochondrial genes generally performed less well than nuclear genes; however, these genes resolved some branches for which nuclear genes failed. Moreover, the combined use of mitochondrial and nuclear sequences produced superior results without artifacts for nodes where mitochondrial and nuclear gene data generated conflicting topologies. These findings strongly advocate the inclusion of mitochondrial sequences, even in deep phylogeny reconstruction. Comparison of tree support between our and previous analyses identified robustly supported high‐confidence clades in the Diptera, but also revealed problematic groupings in need of further analysis.     

Seasonal acclimation of leaf respiration in Eucalyptus saligna trees: impacts of elevated atmospheric CO2 and summer drought

Understanding the impacts of atmospheric [CO₂] and drought on leaf respiration (R) and its response to changes in temperature is critical to improve predictions of plant carbon‐exchange with the atmosphere, especially at higher temperatures. We quantified the effects of [CO₂]‐enrichment (+240 ppm) on seasonal shifts in the diel temperature response of R during a moderate summer drought in Eucalyptus saligna growing in whole‐tree chambers in SE Australia. Seasonal temperature acclimation of R was marked, as illustrated by: (1) a downward shift in daily temperature response curves of R in summer (relative to spring); (2)≈60% lower R measured at 20^oC (R₂₀) in summer compared with spring; and (3) homeostasis over 12 months of R measured at prevailing nighttime temperatures. R₂₀, measured during the day, was on average 30–40% higher under elevated [CO₂] compared with ambient [CO₂] across both watered and droughted trees. Drought reduced R₂₀ by≈30% in both [CO₂] treatments resulting in additive treatment effects. Although [CO₂] had no effect on seasonal acclimation, summer drought exacerbated the seasonal downward shift in temperature response curves of R. Overall, these results highlight the importance of seasonal acclimation of leaf R in trees grown under ambient‐ and elevated [CO₂] as well as under moderate drought. Hence, respiration rates may be overestimated if seasonal changes in temperature and drought are not considered when predicting future rates of forest net CO₂ exchange.