Biology subjects

Mahoney, S. M.

Publications and source records attributed to Mahoney, S. M..

3 recordsLinked to original sources

bioRxiv2021

A mammalian herbivore prefers locally adapted populations in a common garden: implications for climate change mitigation

O_LIClimate change is expected to alter habitat more rapidly than the pace of evolution, leading to tree populations that are maladapted to new local conditions. Assisted migration is a mitigation strategy that proposes preemptively identifying and planting genotypes that are robust to the expected climate change-induced alterations of an area. Assisted migration however, may impact the broader community, including herbivores which often coevolved with local plant genotypes and their defenses. Although this question has been examined in arthropod herbivores, few studies have assessed this question in mammalian herbivores, and fewer still have leveraged experimental design to disentangle the genetic contribution to herbivore preference. C_LIO_LIWe examined the hypothesis that North American porcupine (Erethizon dorsatum) browsing on Fremont cottonwood (Populus fremontii) is under genetic control in a common garden, which allowed us to uncouple genetic and environmental contributions to browse preference. C_LIO_LIGenerally, porcupines selected local trees and trees from climatically similar areas, where trees from local and cooler climate populations suffered over 2x more extensive herbivory than trees from warmer areas. Plant genotype was a significant factor for selection, with the most heavily browsed genotype having on average >10x more herbivory than the least heavily browsed. Because genotypes within and among populations were replicated, we calculated broad-sense heritability in which tree palatability by porcupines was H2B = 0.28 (95% CI: 0.13-0.48) among genotypes. C_LIO_LISynthesis and applications. Our results indicate a genetic component to tree defenses against porcupine herbivory that can be predicted by the climate of the source population. This result has important implications for mammalian herbivores if climate change renders local tree genotypes maladaptive to new conditions. We recommend assisted migration efforts consider this implication and plant stock from both warmer and climatically similar areas to maintain genetic diversity in a changing environment, productivity and forage for mammalian herbivores. C_LI

ecology↗

bioRxiv2021

GLOBAL PATTERNS OF PLUMAGE COLOUR EVOLUTION IN ISLAND-LIVING PASSERIFORM BIRDS

Plumage coloration is an important trait involved communication and is shaped by a variety of ecological pressures. Island residency has the potential to change the evolutionary trajectory of plumage colour by differences in habitat and resources, or by altering predation pressure and social selection intensity. Latitude, island size, and isolation may further influence colour evolution by biasing colonization. Therefore, general patterns of plumage evolution are difficult to disentangle. We used phylogenetically controlled analyses to assess the influence of island residency on plumage colouration, by calculating chromaticity values from red, blue, green scores extracted from photos of Order Passeriformes birds. Importantly, we controlled for ecological factors hypothesized to influence colour evolution and assessed family-level effects. We found 1) colour varied between islands and mainlands in females, but not males, and both sexes were affected by several ecological factors; 2) patterns of colour evolution varied among families; 3) island size and distance to the mainland and other islands significantly influenced colour; and 4) interactions between ecological factors and latitude were consistently influenced colour, supporting a latitudinal gradient hypothesis. Our results indicate although island residency influences female colour evolution, a myriad of ecological factors drive plumage colour and the patterns vary among families.

ecology↗

bioRxiv2021

A tail of plumage colouration: disentangling geographic, seasonal, and dietary effects on plumage colour in a migratory songbird

Plumage ornamentation in birds serves critical inter- and intra-sexual signaling functions. While carotenoid-based plumage colouration is often viewed as a classic condition-dependent sexually selected trait, plumage colouration can be influenced by a wide array of both intrinsic and extrinsic factors. Understanding the mechanisms underlying variation in colouration is especially important for species where the signaling function of ornamental traits is complex or the literature conflicting. Here, we examined variation in the yellow/orange tail feathers of American redstarts (Setophaga ruticilla) passing through two migratory stopover sites in eastern North America during both spring and fall migration to assess the role of geographic variation and seasonality in influencing feather colouration. In addition, we investigated whether diet during moult (inferred via stable isotope analysis of feather {delta}15N and {delta}13C) influenced plumage colouration. Our findings indicate that geographic variation, season, and diet all influence individual differences in American redstart colouration, represented by both traditional and tetrahedral colour variables. The extent to which these factors influence colour expression however is largely dependent on the colour metric under study, likely because different colour metrics reflect different attributes of the feather (e.g., structural components vs. pigment deposition). The effects of diet ({delta}15N) and season were pronounced for brightness, suggesting a strong effect of diet and feather wear/degradation on feather structure. Though hue, a metric that should strongly reflect pigment deposition, also changed from spring to fall, that effect was dependent on age, with only adults experiencing a reduction in ornamentation. Taken together, our results highlight the numerous sources of variation behind plumage coloration and underscores the difficulty of unraveling complex visual signaling systems, such as those in American redstarts.

ecology↗