Late-Quaternary biogeographic scenarios for the brown bear (Ursus arctos), a wild mammal model species

This review provides an up-to-date synthesis of the matrilineal phylogeography of a uniquely well-studied Holarctic mammal, the brown bear. We extend current knowledge by presenting a DNA sequence derived from one of the earliest known fossils of a polar bear (dated to 115 000 years before present), a species that shares a paraphyletic mitochondrial association with brown bears. A molecular clock analysis of 140 mitochondrial DNA sequences, including our new polar bear sequence, provides novel insights into the times of origin for different brown bear clades. We propose a number of regional biogeographic scenarios based on genetic data, divergence time estimates and paleontological records. The case of the brown bear provides an example for researchers working with less well-studied taxa: it shows clearly that phylogeographic models based on patterns of modern genetic variation alone can be substantially improved by including data on historical patterns of genetic diversity in the form of ancient DNA sequences derived from accurately dated samples and by using an approach to divergence-time estimation that suits the data under analysis. Using such approaches it has been possible to (i) establish that the processes shaping modern genetic diversity in brown bears acted recently, within the last three glacial cycles; (ii) distinguish among hypotheses concerning species’ responses to climatic oscillations in accordance with the lack of phylogeographic structure that existed in brown bears prior to the last glacial maximum (LGM); (iii) reassess theories linking monophyletic brown bear populations to particular LGM refuge areas; and (iv) identify vicariance events and track analogous patterns of migration by brown bears out of Eurasia to North America and Japan.     

Strong size evolution of the most massive galaxies since z∼ 2

Using the combined capabilities of the large near-infrared Palomar/DEEP-2 survey, and the superb resolution of the Advanced Camera for Surveys HST camera, we explore the size evolution of 831 very massive galaxies  ( M _⋆≥ 10¹¹ h ⁻²₇₀ M_⊙)  since   z ∼ 2  . We split our sample according to their light concentration using the Sérsic index n . At a given stellar mass, both low  ( n < 2.5)  and high  ( n > 2.5)  concentrated objects were much smaller in the past than their local massive counterparts. This evolution is particularly strong for the highly concentrated (spheroid like) objects. At   z ∼ 1.5  , massive spheroid-like objects were a factor of 4 (±0.4) smaller (i.e. almost two orders of magnitudes denser) than those we see today. These small sized, high-mass galaxies do not exist in the nearby Universe, suggesting that this population merged with other galaxies over several billion years to form the largest galaxies we see today.     

A laboratory investigation of bed-load transport of gravel sediments under dam break flow

Dam break flows and resulting river bed erosion can have disastrous impacts on human safety,infrastructure,and environmental quality.However,there is a lack of research on the mobility of non-uniform sediment mixtures resulting from dam break flows and how these differ from uniform sized sediment.In this paper,laboratory flume experiments revealed that coarse and fine fractions in non-uniform sediment had a higher and a lower bed-load parameter,respectively,than uniform sediments of the same size.Thus,the finer fractions were more stable and the coarser fractions were more erodible in a nonuniform bed compared to a uniform-grained bed.These differences can be explained by the hiding and protrusion of these fractions,respectively.By investigating changes in mobility of the mixed-size fractions with reservoir water levels,the results revealed that at low water levels,when the coarser fractions were only just mobile,the bed-load parameter of the finer fractions was higher than the coarser fractions.The opposite was observed at a higher water level,when a significant proportion of the coarsest fractions was mobilized.The higher protrusion of these grains had an important effect on their mobility relative to the finer grains.The transported sediment on these mixed-sized beds was coarser than the initial bed sediment,and became coarser with an increase in reservoir water level.     

Sublethal impact of short term exposure to the organophosphate pesticide azamethiphos in the marine mollusc Mytilus edulis

Concern has been raised that the increased use of pesticides in intensive aquaculture practices may cause adverse sublethal effects to non-target aquatic species. Azamethiphos is an organophosphate (OP) pesticide used to combat sea lice infestations in farmed salmonids. Here, the sublethal impact on the blue mussel, Mytilus edulis, of short term exposure to azamethiphos was determined. The testing regime included biomarkers of exposure (acetylcholinesterase activity), cytotoxicity (neutral red retention), immune function (phagocytic index) and physiological condition (feeding rate). The distribution and sensitivity of M. edulis acetylcholinesterase to inhibition by azamethiphos was first determined, yielding IC(50) values of 0.736 and 1.30 mg l(-1) for gill and haemolymph, respectively. Exposure of mussels to 0.1 mg l(-1) azamethiphos for periods of up to 24h caused a significant reduction in acetylcholinesterase activity in both the haemolymph (P<0.0002) and the gill (P<0.002), alteration in cell viability (P<0.02) and decrease in phagocytic index (P<0.03). The feeding rate remained unaffected. The results support the hypothesis that, in addition to its neurotoxic effects, azamethiphos can modulate haemocyte function and immune defence in M. edulis at environmentally relevant concentrations after only a few hours.     

Heavy ion formation in Titan's ionosphere: Magnetospheric introduction of free oxygen and a source of Titan's aerosols?

Discovery by Cassini's plasma instrument of heavy positive and negative ions within Titan's upper atmosphere and ionosphere has advanced our understanding of ion neutral chemistry within Titan's upper atmosphere, primarily composed of molecular nitrogen, with ~2.5% methane. The external energy flux transforms Titan's upper atmosphere and ionosphere into a medium rich in complex hydrocarbons, nitriles and haze particles extending from the surface to 1200 km altitudes. The energy sources are solar UV, solar X-rays, Saturn's magnetospheric ions and electrons, solar wind and shocked magnetosheath ions and electrons, galactic cosmic rays (GCR) and the ablation of incident meteoritic dust from Enceladus’ E-ring and interplanetary medium. Here it is proposed that the heavy atmospheric ions detected in situ by Cassini for heights >950 km, are the likely seed particles for aerosols detected by the Huygens probe for altitudes <100 km. These seed particles may be in the form of polycyclic aromatic hydrocarbons (PAH) containing both carbon and hydrogen atoms C_nH_x. There could also be hollow shells of carbon atoms, such as C₆₀, called fullerenes which contain no hydrogen. The fullerenes may compose a significant fraction of the seed particles with PAHs contributing the rest. As shown by Cassini, the upper atmosphere is bombarded by magnetospheric plasma composed of protons, H₂⁺ and water group ions. The latter provide keV oxygen, hydroxyl and water ions to Titan's upper atmosphere and can become trapped within the fullerene molecules and ions. Pickup keV N₂⁺, N⁺ and CH₄⁺ can also be implanted inside of fullerenes. Attachment of oxygen ions to PAH molecules is uncertain, but following thermalization O+ can interact with abundant CH₄ contributing to the CO and CO₂ observed in Titan's atmosphere. If an exogenic keV O+ ion is implanted into the haze particles, it could become free oxygen within those aerosols that eventually fall onto Titan's surface. The process of freeing oxygen within aerosols could be driven by cosmic ray interactions with aerosols at all heights. This process could drive pre-biotic chemistry within the descending aerosols. Cosmic ray interactions with grains at the surface, including water frost depositing on grains from cryovolcanism, would further add to abundance of trapped free oxygen. Pre-biotic chemistry could arise within surface microcosms of the composite organic-ice grains, in part driven by free oxygen in the presence of organics and any heat sources, thereby raising the astrobiological potential for microscopic equivalents of Darwin's “warm ponds” on Titan.     

The DEEP2 Galaxy Redshift Survey: the red sequence AGN fraction and its environment and redshift dependence

We measure the dependence of the active galactic nuclei (AGN) fraction on local environment at   z ∼ 1  , using spectroscopic data taken from the DEEP2 Galaxy Redshift Survey, and Chandra X-ray data from the All-Wavelength Extended Groth Strip International Survey (AEGIS). To provide a clean sample of AGN, we restrict our analysis to the red sequence population; this also reduces additional colour–environment correlations. We find evidence that high-redshift LINERs in DEEP2 tend to favour higher density environments relative to the red population from which they are drawn. In contrast, Seyferts and X-ray selected AGN at   z ∼ 1  show little (or no) environmental dependencies within the same underlying population. We compare these results with a sample of local AGN drawn from the Sloan Digital Sky Survey (SDSS). Contrary to the high-redshift behaviour, we find that both LINERs and Seyferts in the SDSS show a slowly declining red sequence AGN fraction towards high-density environments. Interestingly, at   z ∼ 1  red sequence Seyferts and LINERs are approximately equally abundant. By   z ∼ 0  , however, the red Seyfert population has declined relative to the LINER population by over a factor of ∼4.5. We speculate on possible interpretations of our results.     

‘Strange changes’: Indigenous perspectives of climate change and adaptation in NE Arnhem Land (Australia)

Despite growing global attention to the development of strategies and policy for climate change adaptation, there has been little allowance for input from Indigenous people. In this study we aimed to improve understanding of factors important in integration of Yolngu perspectives in planning adaptation policy in North East Arnhem Land (Australia). We conducted workshops and in-depth interviews in two ‘communities’ to develop insight into Yolngu peoples’ observations and perspectives on climate change, and their ideas and preferences for adaptation. All participants reported observing changes in their ecological landscape, which they attributed to mining, tourism ‘development’, and climate change. ‘Strange changes’ noticed particularly in the last five years, had caused concern and anxiety among many participants. Despite their concern about ecological changes, participants were primarily worried about other issues affecting their community's general welfare. The results suggest that strategies and policies are needed to strengthen adaptive capacity of communities to mitigate over-arching poverty and well-being issues, as well as respond to changes in climate. Participants believed that major constraints to strengthening adaptive capacity had external origins, at regional, state and federal levels. Examples are poor communication and engagement, top-down institutional processes that allow little Indigenous voice, and lack of recognition of Indigenous culture and practices. Participants’ preferences for strategies to strengthen community adaptive capacity tended to be those that lead towards greater self-sufficiency, independence, empowerment, resilience and close contact with the natural environment. Based on the results, we developed a simple model to highlight main determinants of community vulnerability. A second model highlights components important in facilitating discourse on enhancing community capacity to adapt to climatic and other stressors.     

Shoreline management in a policy vacuum: A local authority perspective

In Ireland there is no national shoreline management policy. Instead, management involves a series of actions at the local authority (County) level that respond to local demands, politics and economics within only a broad legal framework. Through the COREPOINT project, University of Ulster scientists have been working with local authority officials in Donegal to bring a scientific understanding of coastal processes to bear on practical management. Experience at several sites has shown significant changes in practice as a result of this interaction, compared to the previous situation when rock armouring was the favoured response to coastal erosion. We argue that achieving sustainable approaches to coastal management in a policy vacuum relies on a combination of (i) commitment to these approaches by local officials, (ii) low levels of public pressure for action, and (iii) limited financial resources. A change in any one of these is likely to lead to unsustainable actions. While close co-operation with scientists can help management in the absence of a coherent policy, only a formal regulatory instrument can deliver sustainable shoreline management.     

Palaeokarst in the Ordovician of the southern Great Basin, USA: implications for sea-level history

Abundant and regionally unique dolostone lithoclast breccias occur throughout the shallow-marine, Lower to Middle Ordovician Pogonip Group in the Nopah Range and adjacent ranges in eastern California and southern Nevada. Breccia bodies display sharply cross-cutting relationships with host dolostone bedrock stratigraphy. They also show stratigraphic variability in size, shape and dolostone clast composition, but similarity in breccia matrix composition and framework texture and fabric. These characteristics are consistent with a palaeokarst origin. Upsection changes in breccia clast lithology as well as multiple occurrences of associated quartz sand-filled grikes (solution-widened fissures) indicate multiple episodes of carbonate platform exposure and karstification. Repeated karstification is also indicated by stratiform bodies of quartz sand and thin terra rossa palaeosols that locally truncate breccias and grike systems, thus bracketing karstified exposure surfaces. Facies successions and stacking patterns between recognized exposure surfaces are developed as transgressive–regressive cycles and thus show depositional sequence architecture. Hence, these breccias and other associated palaeokarst features are related to a succession of disconformities that provide a sequence-stratigraphic framework for assessing Ordovician relative sea-level history of the south-western Cordilleran margin of Laurentia.