Riparian defoliation by the invasive green alder sawfly influences terrestrial prey subsidies to salmon streams

Invasive species in riparian forests are unique as their effects can transcend ecosystem boundaries via stream‐riparian linkages. The green alder sawfly (Monsoma pulveratum) is an invasive wasp whose larvae are defoliating riparian thin‐leaf alder (Alnus tenuifolia) stands across southcentral Alaska. To test the hypothesis that riparian defoliation by this invasive sawfly negatively affects the flow of terrestrial prey resources to stream fishes, we sampled terrestrial invertebrates on riparian alder foliage, their subsidies to streams and their consumption by juvenile coho salmon (Oncorhynchus kisutch). Invasive sawflies altered the composition of terrestrial invertebrates on riparian alder foliage and as terrestrial prey subsidies to streams. Community analyses supported these findings revealing that invasive sawflies shifted the community structure of terrestrial invertebrates between seasons and levels of energy flow (riparian foliage, streams and fish). Invasive sawfly biomass peaked mid‐summer, altering the timing and magnitude of terrestrial prey subsidies to streams. Contrary to our hypothesis, invasive sawflies had no effect on the biomass of native taxa on riparian alder foliage, as terrestrial prey subsidies, or in juvenile coho salmon diets. Juvenile coho salmon consumed invasive sawflies when most abundant, but relied more on other prey types selecting against sawflies relative to their availability. Although we did not find effects of invasive sawflies extending to juvenile coho salmon in this study, these results could change as the distribution of invasive sawflies expands or as defoliation intensifies. Nevertheless, riparian defoliation by these invasive sawflies is likely having other ecological effects that merits further investigation.     

Inactivation of Piscine orthoreovirus

Piscine orthoreovirus infects various salmonid fish species, and the infection is associated with diseases such as heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon (Salmo salar). There are no vaccines available or genetically selected resistant hosts that can efficiently control piscine orthoreovirus (PRV) infection. Currently, the only prophylactic measure against PRV is general biosecurity measures aiming to break the transmission cycle. Methods to eradicate infectious virus from contaminated facilities are desirable, but the knowledge on how to inactivate PRV is lacking. A major bottleneck for inactivation studies is the lack of ability to propagate PRV in cell culture. Therefore, in this study we developed an in vivo model for detection of infectious PRV particles after treatment of the virus with inactivation tools such as heat, pH, iodine, UV and commercially available disinfectants. The results show that standard iodine treatment is efficient in inactivation of the virus, and similarly are high and low pH extremes and treatment with Virocid, a commercially available disinfectant. A UV dose of at least 50 mJ/cm² is required for inactivation, and the virus has high resistance against heat treatment.     

Drought responses of above‐ground and below‐ground characteristics in warm‐season turfgrass

Water shortages have become more chronic as periodic droughts prolong and water demand for urban and agricultural use increases. Plant drought responses involve coordinated mechanisms in both above‐ and below‐ground systems, yet most studies lack comparisons of root and canopy responses under water scarcity and recovery. This is particularly true of research focused on warm‐season turfgrasses in sandy soils with extremely low water holding capacity. To address the lack of examination of coordinated stress and recovery responses, this study compared the above‐ and below‐ground plant responses during a dry‐down period of 21 days and recovery among four warm‐season turfgrass species in the field. Canopy drought responses and recovery were quantified using digital image analysis. In situ root images were captured using a minirhizotron camera system. Common bermudagrass [Cynodon dactylon (L.) Pers.] endured the entire drought period without losing 50% green cover while other species lost 50% green cover in 11–34 days predicted from the regression. The interspecific differences in drought resistance were mainly due to root characteristics. Other drought mechanisms appear to be responsible for differences identified in drought resistance between “Zeon” and “Taccoa Green” manilagrass [Zoysia matrella (L.) Merr.]. Recovery was delayed for up to 2 weeks in the second year, warranting further evaluation for turfgrass persistence under long‐term drought. Three‐week drought posed no threat to the survival of zoysiagrass. Species and genotypic variations were found in achieving full post‐recovery, which can be used to develop water conservation strategies and to adjust consumer expectations.     

Climate effects and bottom‐up controls on growth and size‐at‐age of Pacific halibut (Hippoglossus stenolepis) in Alaska (USA)

Pacific halibut (Hippoglossus stenolepis) are an ecologically, commercially, and culturally important Alaskan groundfish species. Commercial harvest of halibut dates back to the late 19th century and has been managed by the International Pacific Halibut Commission (IPHC) since 1921. IPHC surveys have revealed declining trends in survey biomass in multiple regions and region‐specific declines in mean size‐at‐age (size‐at‐age) over the past two decades (>50% in some areas). Changes in size‐at‐age can arise from a variety of physical, ecological, sampling, and fishery effects, including size‐dependent fishery or predation mortality, alteration in growth from variability in prey quality or quantity, and changes in temperature‐dependent metabolic demands. Here, we develop and apply a bioenergetics model for halibut using survey‐based diet and temperature data for Alaska to evaluate potential environmental drivers of size‐at‐age. In general, juvenile (<40 cm fork length) foraging rates were highest in the Gulf of Alaska concomitant with higher potential growth and elevated basal metabolic demands during warm summer conditions. In contrast, adult (40–120 cm FL) potential growth was highest in the Eastern Bering Sea, potentially reflecting lower metabolic costs and higher rates of prey consumption in that region. We additionally find evidence for interannual variation in potential growth, with a higher frequency of reduced growth potential in the last decade, particularly in the Eastern Bering Sea in 2015 and 2016 for both juvenile and adult halibut. These results suggest the potential for patterns in size‐at‐age to arise from trophic and environmental constraints that collectively limit growth in some regions and years.     

Taxonomy and evolution of cultivated plants: Literature review 1980/1981

Summary Important papers on taxonomy and evolution of cultivated plants published in 1980 and 1981 were compiled and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1980/1981

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1980 und 1981 wurden zusammengestellt und kurz kommentiert.

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: 1980–1981 .

, 1980 1981 . .

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Herrn Prof. Dr. Dr. h. c. mult. H.Stubbe aus Anlaß der 80. Wiederkehr seines Geburtstages gewidmet.     

Taxonomy and evolution of cultivated plants: Literature review 1988/1989

Summary Important papers on taxonomy and evolution of cultivated plants published in 1988 and 1989 were compiled and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1988/1989

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1988 und 1989 wurden zusammengestellt und kurz kommentiert.

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: 1988–1989

, 1988 1989 . .

     

Taxonomy and evolution of cultivated plants: Literature review 1985/1986

Summary Important papers on taxonomy and evolution of cultivated plants published in 1985 and 1986 were compiled and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1985/1986

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1985 und 1986 wurden zusammengestellt und kurz kommentiert.

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¶rt; : 1985–1986

¶rt; , 1985 1986 . .

     

Taxonomy and evolution of cultivated plants: Literature review 1983/1984

Summary Important papers on taxonomy and evolution of cultivated plants published in 1983 and 1984 were complied and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1983/1984

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1983 und 1984 wurden zusammengestellt und kurz kommentiert.

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: 1983–1984

, 1983 1984 . .

     

Beitrag zur Morphologie der Infloreszenzen vonSetaria italica (L.) Beauv.

Zusammenfassung Es werden verschiedene Infloreszenzformen vonSetaria italica (L.) Beauv. vergleichend morphologisch untersucht. Wie der Vergleich mit der Wildsippe,Setaria viridis (L.) Beauv. zeigt, ist die Entwicklung zur Kulturart mit verschiedenen progressiven Veränderungen im reproduktiven Bereich des Verzweigungssystems verbunden. Dabei führt die zunehmende Förderung der Infloreszenzhauptachse sowie der Partialinfloreszenzen zu einer Vergrößerung und verstärkten Gliederung der Gesamtinfloreszenz. Daneben werden auch regressive Entwicklungstendenzen sichtbar, die in einer zunchmenden Reduktion des Basis- und Spitzenbereichs der Infloreszenz zum Ausdruck kommen. Die stärkste morphologische Ableitung haben Formen mit einer dichotom verzweigten Infloreszenz erfahren. Die Ausprägung der Infloreszenzmerkmale zeigt eine starke Umweltabhängigkeit.

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Contribution to the morphology of the inflorescences ofSetaria italica (L.) Beauv.

Summary The morphology of different types of inflorescences were investigated in Setaria italica (L.) Beauv. The comparison with the wild species,Setaria viridis (L.) Beauv., shows that the evolution towards the cultivated species is combined with different progressive changes in the reproductive part of the ramification system. Thereby the increasing promotion of the main axis of the inflorescence as well as the partial inflorescences leads to an enlargement and increased articulation of the whole inflorescence. Besides regressive developmental tendencies are also observed, as expressed by increasing reduction of the basis and the top of inflorescence. The greatest deviation is seen in the form with dichotomous branched inflorescences. The characters of the inflorescences depend greatly on the environmental conditions.

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Setaria italica (L.) Beauv.

Setaria italica (L.) Beauv. . Setaria viridis (L.) Beauv., . , . , . . .