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Life history traits of marine Diptera in the Nearctic Pacific
(Canadian Science Publishing, 2024-09-28) Gibson, Joel; Choong, Henry
The generally accepted paradigm maintains that insects are either freshwater or terrestrial, but never marine. Recent research, however, has shown that there are insects adapted to a life within the marine intertidal zone. This study provides evidence of adaptations to specific morphodynamic marine shoreline habitats, including stranded marine algal wrack, surface-substrate cover, and geographical location, amongst 33 species of British Columbia Diptera reported from marine habitats. A total of 2,123 specimens were collected and identified from 96 survey events that also included surveys of algal wrack. Of the 33 marine species examined, 15 demonstrated a statistically significant association with a specific shoreline habitat element. In marine Diptera, variation in algal wrack type may play an important role in maintaining diversity by supporting species differences within and between wrack communities, thereby preventing competitive exclusion, even though overall insect diversity in marine environments remain lower than freshwater or strictly terrestrial habitats. In addition, nine species represent new range records for British Columbia or Canada: Fucellia apicalis Kertesz, 1908, Fucellia thinobia (Thomson, 1869), Tethina horripilans (Melander, 1952), Melanderia mandibulata Aldrich, 1922, Paraphrosylus wirthi (Harmston, 1951), Helcomyza mirabilis Melander, 1920, Heterocheila hannai (Cole, 1921), Chersodromia parallela (Melander, 1927), Scathophaga litorea (Fallén, 1819).
Robinia pseudoacacia, a nitrogen-fixing tree, facilitates the future growth of neighboring trees in Black Rock Forest
(Canadian Science Publishing, 2025-01-22) Helms, Alexa B; Huddell, Alexandra M; Liao, Wenying; Staccone, Anika P.; Buckley, Brendan M.; Schuster, William; Menge, Duncan N. L.
Trees that form symbioses with nitrogen (N)-fixing bacteria (N-fixers) have long been thought to facilitate neighbors’ growth by providing new N, but some data do not show facilitation. Two hypotheses to explain the lack of facilitation are that (1) N-fixers may decrease the amount of N they fix over time, reducing the N supply to their neighbors and (2) the effect of facilitation might take longer than the 1-5 y interval of most studies. In this study, we tested these hypotheses with the N-fixing tree Robinia pseudoacacia L. and its non-fixing neighbors, using tree ring N isotopes to estimate past N fixation and tree ring width to estimate past size and growth. Where the isotopes allowed a constrained estimate of N fixation, we did not find support for the first hypothesis: 51% of Robinia’s N came from fixation throughout its 60-y lifespan, with little variation across age. In support of the second hypothesis, we found that Robinia enhanced growth of neighboring trees in the future (up to 14 y) more than in the present. This delayed effect matches the expected timing of facilitation by N-fixers and indicates that single-census studies might underestimate the degree to which N-fixers facilitate forest growth.
The role of relatedness, age and origin in shaping social networks for two bison (Bison bison bison) herds in north-central Montana
(Canadian Science Publishing, 2024-10-29) Bresnan, Claire; Creel, Scott; Edwards, Cody W.; Gooley, Rebecca M.; Heidebrink, Scott; Koepfli, Klaus-Peter; McShea, William J.; Pukazhenthi, Budhan; Stutzman, Johnathon; Shamon, Hila
Species with fission-fusion social organization, where groups break apart and merge over time, show variable subgroup stability. Plains bison (Bison bison bison Linnaeus, 1758), a keystone species in North American grasslands, exhibit fission-fusion dynamics. However, it is unclear whether subgroups are stable over time nor whether they are composed of related individuals. We used fine-scale behavioral observations and movement data from GPS ear tags to construct social networks for two plains bison herds over multiple years at American Prairie in north-central Montana. These herds are semi-free roaming and graze year-round in 32.4 and 111.6 km2 fenced pastures. While the bison in our study did exhibit fission-fusion behavior, we did not observe stable subgroups in time-aggregated social networks constructed over single growing seasons (eigenvector modularity ranged from -0.008 to 0.027). We used Mantel tests to assess the relationships between association strength and relatedness, age, and place of origin. We found that only first-order relatives were more likely to associate, and shared age and place of origin had no significant impact. The observed lack of stable subgroups challenges prevailing assumptions and highlights the need for future research into the mechanisms of fission-fusion dynamics in plains bison and other managed social species.
Impacts of elevated water temperature on the behaviour and thermal tolerance of the Bluntnose Minnow (Pimephales notatus)
(Canadian Science Publishing, 2024-11-17) Moffat, Katelyn Tessa Tessa; Groves, Veronica; Chapman, Lauren J.
Fish often show behavioural responses to elevated water temperature before they reach their upper thermal limit. We measured the activity, aggression, and thermal tolerance (critical thermal maximum, CTmax; agitation temperature, Tag; thermal agitation window; and thermal safety margin) of the Bluntnose Minnow (Pimephales notatus Rafinesque, 1820). Thirty fish underwent a five-week acclimation period to two temperatures (ambient, 16 °C or hot, 25 °C). We took behavioural observations throughout the five weeks and conducted thermal tolerance trials at the end of the acclimation period. Aggression was marginally higher in fish acclimated to hot water, but there was no change over time (week 1 to 5). Activity was higher in the hot acclimation treatment, but again there was no change in activity over time. We found that CTmax, Tag, and the agitation window (the difference between CTmax and Tag) were significantly greater in fish acclimated to 25 °C, but the thermal safety margin (the difference between acclimation temperature and CTmax) was smaller. This study highlights the significance of behavioural responses to elevated water temperature that may occur well before the upper critical thermal limit, which may result in negative physiological (metabolic costs) or behavioural (avoidance/refuge seeking behaviour) impacts over time.
Effect of Lithospheric Thickness and Radial Mantle Viscosity Profile on Glacial Isostatic Adjustment Crustal Motions in North America
(Canadian Science Publishing, 2025-01-16) Brierley-Green, Connor; James, Thomas S.
North America is experiencing vertical and horizontal crustal motion due to glacial isostatic adjustment (GIA). To explore these motions across central and eastern North America, GIA modelling was carried out employing the ICE-6G_C surface loading model. The Earth model response was determined for 500 3-layered mantle viscosity profiles at nine different lithospheric thicknesses, assuming a constrained density and elastic structure. The predictions were compared to observed velocities downloaded from the Nevada Geodetic Laboratory for selected Global Navigation Satellite System (GNSS) sites and were corrected for hydrological loading and current global ice change. The fit is assessed through a Root Mean Square (RMS) calculation of the residual velocities. Scanning across lithospheric thicknesses and viscosity profiles, the preferred models were compiled to assess the overall best fit for vertical, horizontal, and combined crustal motions. The horizontal and combined responses exhibit two optimal viscosity profile ranges dependent on the lithospheric thickness. The viscosity profile for thinner lithospheres (