Daily ocean monitoring since the 1860s shows record warming of northern European seas

Ocean temperatures in most parts of the world are increasing and are expected to continue to rise during the 21st century. A major challenge to ecologists and marine resource managers is to understand and predict how these global changes will affect species and ecosystems at local scales where temperature more directly affects biological responses and species interactions. Here, we investigate historical variability in regional sea surface temperature in two large heavily exploited marine ecosystems and compare these variations with expected rates of temperature change for the 21st century. We use four of the world's longest calibrated daily time series to show that trends in surface temperatures in the North and Baltic Seas now exceed those at any time since instrumented measurements began in 1861 and 1880. Temperatures in summer since 1985 have increased at nearly triple the global warming rate, which is expected to occur during the 21st century and summer temperatures have risen two to five times faster than those in other seasons. These warm temperatures and rates of change are due partly to an increase in the frequency of extremely warm years. The recent warming event is exceeding the ability of local species to adapt and is consequently leading to major changes in the structure, function and services of these ecosystems.     

Multidecadal to millennial-scale shifts in drought conditions on the Canadian prairies over the past six millennia: implications for future drought assessment

Three high-resolution climatic reconstructions, based on diatom analyses from lake sediment cores from the Canadian prairies, show that shifts in drought conditions have prevailed on centennial to millennial time scales for at least the past six millennia. These shifts in mean aridity exhibit broad regional synchrony, with particularly pronounced shifts at all sites between ∼1700–2000 cal. yr bp and ∼3600–3900 cal. yr bp , as well as at ∼5400–5500 cal. yr bp for the two sites which extend back to at least 6000 cal. yr bp . The two Saskatchewan lakes exhibited significant coherence in both the timing and direction of these shifts, whereas inferred changes at the westernmost site in Alberta were significantly correlated to the Saskatchewan sites, but opposite in sign, and exhibited more high-frequency variation on the scale of centuries. The mechanisms behind these abrupt shifts in aridity are poorly understood, but may be linked to changes in oceanic–atmospheric interactions that influence the mean position of the jetstream and the associated storm tracks. Natural shifts in mean climatic conditions may accelerate with increasing carbon dioxide levels intensifying the likelihood of extreme droughts in North American prairies.     

THE EFFECT OF MALEIC HYDRAZIDE ON THE GROWTH RESPONSE OF PLANTS TO GIBBERELLIC ACID

Maleic hydrazide (MH) and gibberellic acid (GA) were applied alone and in combination at various doses to dwarf and tall varieties of garden pea, and their effect on stem extension measured. Combinations of MH and 3-indolylacetic acid (IAA) were also studied. Stern extension of dwarf peas was accelerated by GA and inhibited by MH. Their effects were not additive, since MH reduced the response to GA at all concentrations of each tested. IAA did not affect stem extension, whether applied alone or in combination with MH. Stem extensions of tall peas was not affected by GA or IAA alone. MH severely inhibited growth and this inhibition was not reduced either by GA or by IAA. At low doses MH broke apical dominance and side branches developed; extension of these was stimulated by GA and IAA and extension of the main axis correspondingly still further reduced. The results show that MH prevents the response to GA of GA-sensitive plants. It is suggested that the rapid growth of tall peas, as compared with that of dwarfs, and their lack of response to GA, are due to a greater capacity to synthesize a 'GA-like hormone'. Growth of tall peas is much more drastically inhibited by MH than that of dwarf peas and the suggestion is made that the inhibition of shoot growth induced by MH is due primarily to blocking the activity of the postulated 'GA-like hormone'.     

The phylogeny of stiletto flies (Diptera: Therevidae)

The therevoid clade represents a group of four families (Apsilocephalidae, Evocoidae, Scenopinidae and Therevidae) of lower brachyceran Diptera in the superfamily Asiloidea. The largest of these families is that of the stiletto flies (Therevidae). A large‐scale (i.e. supermatrix) phylogeny of Therevidae is presented based on DNA sequence data from seven genetic loci (16S, 18S and 28S ribosomal DNA and four protein‐encoding genes: elongation factor 1‐alpha, triose phosphate isomerase, short‐wavelength rhodopsin and the CPSase region of carbamoyl‐phosphate synthase‐aspartate transcarbamoylase‐dihydroorotase). Results are presented from Bayesian phylogenetic analyses of approximately 8.7 kb of sequence data for 204 taxa representing all subfamilies and genus groups of Therevidae. Our results strongly support the sister‐group relationship between Therevidae and Scenopinidae, with Apsilocephalidae as sister to Evocoidae. Previous estimates of stiletto fly phylogeny based on morphology or DNA sequence data, or supertree analysis, have failed to find significant support for relationships among subfamilies. We report for the first time strong support for the placement of the subfamily Phycinae as sister to the remaining Therevidae, originating during the Mid Cretaceous. As in previous studies, the sister‐group relationship between the species‐rich subfamilies Agapophytinae and Therevinae is strongly supported. Agapophytinae are recovered as monophyletic, inclusive of the Taenogera group. Therevinae comprise the bulk of the species richness in the family and appear to be a relatively recent and rapid radiation originating in the southern hemisphere (Australia + Antarctica + South America) during the Late Cretaceous. Genus groups are defined for all subfamilies based on these results.     

How Spaniards Became Chumash and other Tales of Ethnogenesis

In the 1970s, a network of families from Santa Barbara, California, asserted local indigenous identities as "Chumash." However, we demonstrate that these families have quite different social histories than either they or supportive scholars claim. Rather than dismissing these neo-Chumash as anomalous "fakes," we place their claims to Chumash identity within their particular family social histories. We show that cultural identities in these family lines have changed a number of times over the past four centuries. These changes exhibit a range that is often not expected and render the emergence of neo-Chumash more comprehendible. The social history as a whole illustrates the ease and frequency with which cultural identities change and the contexts that foster change. In light of these data, scholars should question their ability to essentialize identity.     

The loss of aquatic and riparian plant communities: Implications for their consumers in a riverine food web

Abstract Human induced alterations to rivers and steams have resulted in significant changes to the structure and diversity of riparian and aquatic plant communities. These changes will impact on the dynamics of riverine carbon cycles and food web structure and function. Here we investigate the principal sources of organic carbon supporting local shredder communities across a gradient in different levels of anthropogenic development along riverine reaches, in South Australia. In forested/wooded reaches with minimum to limited development, semi‐emergent macrophytes were the principal sources of organic carbon supporting the local shredder communities. However, in developed reaches, course particulate organic matter and filamentous algae were the principal food sources. The C:N ratios of the food sources in developed reaches were higher than those of their consumers indicating a stoichiometric mismatch. This imbalanced consumer‐resource nutrient ratio in those developed reaches is likely to impose constraints on the growth and reproduction of their aquatic shredder communities with probable knock‐on effects to higher trophic levels.     

Fire season effects on the recruitment of non‐sprouting serotinous Proteaceae in the eastern (bimodal rainfall) fynbos biome,South Africa

Abstract Research in Mediterranean‐climate shrublands in both South Africa and Australia shows that recruitment of proteoid shrubs (non‐sprouting, serotinous Proteaceae) is best after warm‐season (summer and autumn) fires and worst after cool‐season (winter and spring) ones. This pattern has been attributed to post‐dispersal seed attrition as well as size of pre‐dispersal seed reserves. Here we investigate patterns of post‐fire recruitment for four proteoid species in the eastern part of South Africa's fynbos biome, which has a bimodal (spring and autumn) rainfall regime. Despite the lack of significant differences in recruitment between cool‐ and warm‐season burns, we find some evidence for favourable recruitment periods following fires in spring and autumn, immediately before, and coinciding with, the bimodal rainfall peaks. This suggests that enhanced recruitment is associated with conditions of high soil moisture immediately after the fire, and that rapid germination may minimize post‐dispersal seed attrition. In two of the species, we also find a shift from peak flowering in winter and spring in the Mediterranean‐climate part of the fynbos biome, to summer and autumn flowering in the eastern part. Because these two species are only weakly serotinous, warm‐season flowering would result in maximal seed banks in spring, which could explain the spring recruitment peak, but not the autumn one. We conclude that eastern recruitment patterns differ significantly from those observed in the western and central parts of the biome, and that fire management protocols for the east, which are currently based on data and experience from the winter‐rainfall fynbos biome, need to be adjusted accordingly. Fire managers in the eastern fynbos biome should be less constrained by requirements to burn within a narrow seasonal range, and should therefore be in a better position to apply the required management burns.     

Nitrate and glutamate as environmental cues for behavioural responses in plant roots

As roots explore the soil, they encounter a complex and fluctuating environment in which the different edaphic resources (water and nutrients) are heterogeneously distributed in space and time. Many plant species are able to respond to this heterogeneity by modifying their root system development, such that they colonize the most resource-rich patches of soil. The complexities of these responses, and their dependence on the implied ability to perceive and integrate multiple external signals, would seem to amply justify the term 'behaviour'. This review will consider the types of behaviour that are elicited in roots of Arabidopsis thaliana by exposure to variations in the external concentrations and distribution of two different N compounds, nitrate and glutamate. Molecular genetic studies have revealed an intricate N regulatory network at the root tip that is responsible for orchestrating changes in root growth rate and root architecture to accommodate variations in the extrinsic and intrinsic supply of N. The review will discuss what is known of the genetic basis for these responses and speculate on their physiological and ecological significance.     

Stream ecosystem responses to the 2007 spring freeze in the southeastern United States: unexpected effects of climate change

Some expected changes in climate resulting from human greenhouse gas emissions are clear and well documented, but others may be harder to predict because they involve extreme weather events or heretofore unusual combinations of weather patterns. One recent example of unusual weather that may become more frequent with climate change occurred in early spring 2007 when a large Arctic air mass moved into the eastern United States following a very warm late winter. In this paper, we document effects of this freeze event on Walker Branch, a well‐studied stream ecosystem in eastern Tennessee. The 2007 spring freeze killed newly grown leaf tissues in the forest canopy, dramatically increasing the amount of light reaching the stream. Light levels at the stream surface were sustained at levels considerably above those normal for the late spring and summer months due to the incomplete recovery of canopy leaf area. Increased light levels caused a cascade of ecological effects in the stream beginning with considerably higher (two–three times) rates of gross primary production (GPP) during the late spring and summer months when normally low light levels severely limit stream GPP. Higher rates of stream GPP in turn resulted in higher rates of nitrate (NO₃^?) uptake by the autotrophic community and lower NO₃^? concentrations in stream water. Higher rates of stream GPP in summer also resulted in higher growth rates of a dominant herbivore, the snail Elimia clavaeformis. Typically, during summer months net NO₃^? uptake and snail growth rates are zero to negative; however, in 2007 uptake and growth were maintained at moderate levels. These results show how changes in forest vegetation phenology can have dramatic effects on stream productivity at multiple trophic levels and on nutrient cycling as a result of tight coupling of forest and stream ecosystems. Thus, climate change‐induced changes in canopy structure and phenology may lead to large effects on stream ecosystems in the future.