Phylogeny of Sabellidae (Annelida) and relationships with other taxa inferred from morphology and multiple genes

The monophyly of Sabellidae, the phylogenetic relationships of its lineages, and the composition of Sabellida have been debated for many decades. Most studies on sabellid phylogeny have focused on morphological features but little DNA work has been published to date. We performed analyses using maximum‐parsimony methods that included 36 sabellids and members of previously related taxa. We integrated morphological and DNA sequence data to resolve relationships at different hierarchical levels (135 morphological features, fragments of the nuclear ribosomal RNA genes 18S and 28S, and the mitochondrial gene 16S). The results indicate the monophyly of Sabellida, including Sabellidae and Serpulidae. Monophyly of Fabriciinae and Serpulidae is assessed and the two groups are recovered as sister taxa, but with weak support. There is no significant support for the monophyly of Sabellinae. Relationships between members of the Sabellidae are still partially unresolved due to incongruence between partitions and low support for most clades. The evolution and transformation of certain characters within Sabellidae is explored.
© The Willi Hennig Society 2010.     

Craniometric variation of some Mediterranean and Atlantic populations of Stenella coeruleoalba (Mammalia,Delphinidae): A three‐dimensional geometric morphometric analysis

The variability of cranial features of Atlantic and Mediterranean samples of Stenella coeruleoalba was examined using a three‐dimensional geometric morphometric approach. Data were collected on 79 skulls from the upper and middle Mediterranean Sea, the Atlantic French coasts, and Scotland. Three‐dimensional x, y, and z coordinates of 27 landmarks were recorded on each left half skull using a Microscribe 3‐D digitizer. All configurations were rotated, centered, and scaled, and residuals from the mean configuration were analyzed through multivariate analyses of variance. Mahalanobis distances among populations were used to evaluate phenetic relationships. Consensus configurations were compared to visualize shape differences among samples. Analyses revealed significant differences among populations, a clear distinction of the Scottish coasts dolphins from the other samples, and a closer relationship of the dolphins from the French coasts to the Mediterranean populations than to the Scottish one. Shape differences are mainly concentrated in the rostral and in the occipital regions of the skull. Phylogenetic and adaptive factors were invoked as possible causes of the variation patterns.     

Climate,Livestock, and Vegetation: What Drives Fire Increase in the Arid Ecosystems of Southern Russia?

Fire is an important natural disturbance process in arid grasslands but current fire regimes are largely the result of both human and natural processes and their interactions. The collapse of the Soviet Union in 1991 spurred substantial socioeconomic changes and was ultimately followed by a rapid increase in burned area in southern Russia. What is unclear is whether this increase in burned area was caused by decreasing livestock numbers, vegetation changes, climate change, or interactions of these factors. Our research goal was to identify the driving forces behind the increase in burned area in the arid grasslands of southern Russia. Our study area encompassed 19,000 km² in the Republic of Kalmykia in southern Russia. We analyzed annual burned area from 1986 to 2006 as a function of livestock population, NDVI, precipitation, temperature, and broad-scale oscillation indices using best subset regressions and structural equation modeling. Our results supported the hypothesis that vegetation recovered within 5–6 years after the livestock declined in the beginning of the 1990s, to a point at which large fires could be sustained. Climate was an important explanatory factor for burning, but mainly after 1996 when lower livestock numbers allowed fuels to accumulate. Ultimately, our results highlight the complexity of coupled human-natural systems, and provide an example of how abrupt socioeconomic change may affect fire regimes.     

Nerve Growth Factor Effect on Adenosine Transport in Cultured Chromaffin Cells

Chromaffin cells both recently isolated or in culture present a high-affinity adenosine transporter with a Km value of 1 microM. When cells were exposed to nerve growth factor (NGF; 10 ng/ml), the adenosine transporter affinity decreased to 3 microM. This value was maintained from 3 days after plating to the end of the culture period. A change in the transport capacity was observed, with a significant increase (approximately 200-260%) in NGF-cultured cells throughout the period studied.     

Effects of disturbance intensity and frequency on bacterial community composition and function

Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and 'disturbed' incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.     

Chemosensory stimulation of luteinizing hormone secretion in male Siberian hamsters (Phodopus sungorus)

Male Siberian hamsters (Phodopus sungorus) housed in long days (LD), but not short days (SD) release luteinizing hormone (LH) when exposed to females. This study examined whether this response is specific to a female and identifies the source of a stimulus that induces LH release. Serum concentrations of LH, testosterone (T), follicle stimulating hormone (FSH), and cortisol were examined in all experiments. T concentrations mirrored the LH response; FSH and cortisol were unchanged in response to all stimuli. Exposure to an LD female, irrespective of her reproductive status, but not an SD female, elicited LH release. Exposure to another male did not trigger LH release. Males released LH when allowed physical contact with an anesthetized female, but not when separated from a normally active female, suggesting that tactile or nonvolatile chemosensory stimuli elicit LH release. Urine and secretions collected from the vagina as well as oral, midventral, perineal, and rectal glands, elicited marked behavioral responses in male P. sungorus. Despite these behavioral responses, only feces from females elicited LH release in males. Males released LH in response to feces extracted from the rectum and to cotton swabs that had been rubbed against the rectal mucosa, suggesting that a component of rectal secretions may trigger LH release in male Siberian hamsters. Taken together, these data and previous data from our laboratory indicate that both the production of and the response to a pheromone that triggers the selective release of LH is regulated by day length.     

Liquid medium and liquid overlays improve embryogenic tissue initiation in conifers

Somatic embryogenesis (SE) is expected to play an important role in increasing productivity, sustainability, and uniformity of future US forests. For commercial use, SE technology must work with a variety of genetically diverse trees. Initiation in loblolly pine (Pinus taeda L.), the main commercial US forest species, is often recalcitrant for desirable genotypes. Liquid initiation medium with no or low gelling agent or placement of the explant on gelled medium followed later by a liquid medium overlay during the initiation process increased initiation for loblolly pine and Norway spruce (Picea abies). Loblolly pine liquid medium required reduction of NAA from 2 mg/l in gelled medium to 0.3 mg/l in liquid medium. Once the NAA concentration was adjusted, loblolly pine initiation occurred in liquid medium with fully immersed megagametophytes, explants supported at the liquid medium surface, or on gelled medium overlaid with liquid medium. Liquid overlays (0.25 ml) consisting of medium with NAA reduced to 0.3 mg/l, 9 mg/l ABA and no gelling agent applied to explants on 2 ml of gelled medium provided excellent initiation results. Greatest initiation percentages occurred when the liquid overlay was applied 14 days after placement of the megagametophyte on gelled medium. Initiation increases ranged from +8.5% with high-value cross-pollinated seed sources to +6.5 to +9.9% with open-pollinated and often recalcitrant seed sources. Liquid medium addition allows rapid replenishment of nutrients and adjustment or change of pH, hormones, or other parameters without disturbing the tissue.     

Lake Baikal climatic record between 310 and 50 ky BP: Interplay between diatoms, watershed weathering and orbital forcing

The environmental record from Lake Baikal, Russia, from 310 to 50 ky BP (MIS 9a to MIS 3) was interpreted using rock magnetic, UV–Vis spectral, mineralogical, and diatom analyses. The age model was based on a correlation of the diatom and chemical weathering records and the summer insolation curve at 55°N and checked against an age model based on the proxy of relative palaeointensity of the Earth's magnetic field. Peaks in chemical weathering within the watershed, inferred from maximum concentration of magnetic and coloured minerals and mica, the lowest mean Fe oxidation state in silicates and highs in expandable clay minerals correlated with the Northern Hemisphere summer insolation minima at 55°N. Reconstructed changes in weathering intensity are better correlated to insolation patterns than to global ice volume records. We propose a scheme of yet missing palaeoenvironmental interpretation of the diatom assemblage, including also some extinct species. Aulacoseira baicalensis and Aulacoseira skvortzowii were abundant in the early stages of lake flora recovery immediately after deglaciation and during MIS 7e and MIS 5e; periods of more pronounced continental climate and peak chemical weathering. Stephanodiscus formosus var. minor, Cyclotella minuta and Cyclotella ornata dominated in intervals of decreased seasonality and decreased humidity at the end of most interglacial/interstadial diatom zones. Stephanodiscus grandis, Stephanodiscus carconeiformis and Stephanodiscus formosus were ubiquitous between MIS 8 and MIS 5, an interval marked by high seasonality, i.e., large differences between winter and summer insolation, and low humidity revealed by a low hydrolysis of expandable clay minerals in the watershed. Diatom concentrations peaked in the climatic optima of MIS 7e and MIS 5e and in the short periods marked by shifts to warmer conditions in the upper sections of MIS 5: MIS 5c (103–99 ky BP), MIS 5b (90–88 ky BP), and MIS 5a (84–79 ky BP) in which increased humidity resulted in enhanced hydrolysis of clay minerals. No such short similar climatic optimums were found from MIS 9a to MIS 6. Sharp climate deteriorations recorded in the diatom and clay mineral records at 107, 94, and 87 ky BP, however, occurred within 1–2 ky of cold extremes in North Atlantic sea surface temperature emphasizing the strong teleconnections between the two localities.