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Comparing lifetime and annual fitness measures reveals differences in selection outcomes
(Canadian Science Publishing, 2025-02-11) Dobson, F. Stephen; Saraux, Claire; Coltman, D.; Raveh, Shirley; Viblanc, Vincent A.
Selection analyses of long-term field data frequently use annual comparisons from long-lived species with overlapping generations to measure fitness differences with respect to phenotypic characteristics, such as annual phenological timing. An alternative approach applies lifetime estimates of fitness that encompass several annual events. We studied selection on emergence date from hibernation in male and female Columbian ground squirrels, Urocitellus columbianus (Ord 1915). From 32 years of records, we estimated lifetime fitness using either lifetime reproductive success (LRS) or matrix methods, and estimated annual fitness from individual yearly survival and reproduction. We also modified estimates to statistically control for changes in mean population fitness over the lives of individuals. We regressed lifetime fitness metrics on dates of emergence from hibernation, to quantify the strength of selection on emergence date (a heritable trait). All fitness metrics were highly correlated, but differences became apparent when estimating selection coefficients for emergence dates. The annual fitness metric and LRS produced lower effect sizes of selection coefficients than matrix-based lifetime fitness and a lifespan approach based on average annual fitness. Further, only these last two metrics revealed stabilizing selection. These results suggest that the choice of a fitness metric may influence our conclusions about natural selection.
APPLICATION OF ELECTRIC RESISTANCE TOMOGRAPH (ERT): INNOVATIVE NON-DESTRUCTIVE METHOD IN ANALYSING INTERIORS OF STANDING TREES IN TROPICS
(Canadian Science Publishing, 2025-03-27) Divakara, Baragur Neelappa; Singh, Madan Prasad
The Electric Resistance Tomograph (ERT) is a customized tree specific novel technology which was developed to monitor and estimate the tree growth and development by looking into the inner structure of the standing tree to analyse the growth/heartwood and health/decay status. Electrical Resistivity Tomography (ERT) is a valuable tool in tropical forestry for assessing the heartwood-sapwood boundary and detecting wood decay. By measuring electrical resistivity at multiple points around a tree trunk, ERT creates detailed profiles of the tree's internal structure, identifying variations in moisture content, density, and decay. This non-invasive method provides accurate, real-time data that aids in sustainable forest management, conservation, and logging decisions. It allows for precise identification of heartwood, sapwood, and decayed areas without harming the tree, making it a cost-effective and eco-friendly approach for monitoring tree health. This technique is known to contribute to detect and study the internal assembly of a tree for the mapping decay, hollowness and also to distinguish the sapwood and heartwood demarcation. This paper is addressing the possibility of exploring the application of ERT on economically important tropical trees viz. sandalwood (Santalum album L.), red sanders (Pterocarpus santalinus L.f.) and agarwood (Aquilaria agalocha Roxb.) to know the presence/absence of heartwood/decay in standing trees. Also, to know presence/absence of decay and extent of decay in standing trees using ERT
Ethylene sensitivity assay in medicinal and fiber-type Cannabis seedlings reveals a triple-response-like phenotype
(Canadian Science Publishing, 2025-02-25) Monthony, Adrian S; Ledeuil, Marilou; Torkamaneh, Davoud
This study examines the conservation of ethylene response mechanisms in cannabis seedlings, expanding on evidence of ethylene’s influence in mature plants, particularly sexual plasticity. Using hemp and drug-type seedlings, we observed a unique triple-response-like phenotype under dark conditions with ethephon treatment, characterized by hypocotyl and radicle shortening alongside hypocotyl thickening. Employing a novel ethephon-based assay, this research circumvents the challenges of gaseous ethylene, enabling more accessible investigation of ethylene sensitivity in early development. Results showed high responsiveness to low ethephon concentrations (125–500 mg/L), unlike prior findings in mature plants, while silver thiosulfate (STS; 1–3 mM) consistently reversed ethylene effects, supporting the conservation of ethylene signaling pathways across genetic backgrounds. Interestingly, the absence of an exaggerated apical hook in treated seedlings suggests unique regulatory adjustments in achene-bearing plants. This study advances our understanding of ethylene signaling in early cannabis development and provides a foundation for future research on ethylene’s role in developmental processes, including sexual plasticity.
Variations in ring width density and tracheid morphology of tamarack wood (Larix laricina)
(Canadian Science Publishing, 2025-01-25) Lamara, Mebarek; Ben Halima, Melek; Bouslimi, Besma; Perron, Martin; Hammami Gassara, Dorra; Koubaa, Ahmed
The tree genetic improvement programs focus on tree growth with little attention to wood quality despite determining the potential of wood for various applications. This study investigated the intra-ring and intra-tree variations of wood growth, density, tracheid length and width of Larix laricina trees and estimated their quantitative genetic parameters of a 30-year-old progeny test using destructive and nondestructive samplings.
The average ring density was 491 kg/m³. The proportion of latewood remains uniform and constant within the tree at about 24%. The tracheids were fine and long, averaging 25 µm in diameter and 2.23 mm in length for earlywood and 25 µm in diameter and 2.55 mm in length for latewood. The cambial age has a significant effect on almost all wood properties. A positive and significant phenotypic and genotypic correlation between density components was found for juvenile and mature wood. Tracheid morphological properties were positively correlated with each other and negatively correlated with wood density and growth components, except for earlywood density. Heritability estimates indicate that wood density components were under moderate to strong genetic control. These results showed that wood quality traits are important selection criteria for breeding programs to improve wood quality while maintaining a high growth rate.
Long-term biodiversity erosion: Limited co-existence of the Eurasian zebra mussel and native mussels in a North American river after 25 years
(Canadian Science Publishing, 2025-01-10) Zwarych, Kennedy L.; Taranu, Zofia E.; Ricciardi, Anthony
North American unionid mussel populations have experienced significant mortality due to competition and fouling by the Eurasian zebra mussel Dreissena polymorpha (Pallas 1771). Habitats whose water chemistry is suboptimal for the zebra mussel could plausibly serve as refugia in which unionids and zebra mussels co-exist. The Richelieu River, invaded by the zebra mussel in the mid-1990s, has a mean calcium concentration (~18 mg L-1) believed insufficient for supporting a zebra mussel population capable of severely damaging unionids. Using a 25-year dataset, we tested how unionid diversity and abundance have changed along with zebra mussel fouling levels in the river over time. Local unionid populations suffered major declines across sites regardless of their distance from the river’s headwaters, Lake Champlain—a constant source of zebra mussel larvae. Over the past 25 years, unionid diversity and abundance have eroded to a similar extent and followed a similar timeline of initial rapid population decline as has been observed in invaded calcium-rich habitats. We hypothesize that sustained exposure to zebra mussel fouling and food competition has produced a limited co-existence in which long-term impacts of zebra mussels have accrued.