Biology Letters最新文献

For many wildlife impacted by invasive pathogens, demand for management that curbs impacts can exist long after emergence, yet there are few examples where management is demonstrated as both efficacious and sustainable. We investigated disease dynamics in a bare-nosed wombat (Vombatus ursinus) population where there is demand for disease management and undertook an intervention to test the capacity to curb the severity of sarcoptic mange (caused by Sarcoptes scabiei) using relatively simple therapeutic delivery methods. Using transect surveys, we observed large numbers of bare-nosed wombats (average 50 per survey) in our survey area (ca 20 hectares), finding wombats were healthy (median body condition 4/5) and had a low and stable apparent prevalence of mange (average 3.3%) over 20 months. We undertook a monthly disease management programme for six months, focused on targeted therapeutic (fluralaner) interventions delivered to free-ranging individuals with signs of sarcoptic mange. Our programme, applicable to other wildlife and wombat-mange situations, successfully reduced disease severity among all wombats surveyed, as well as for individuals who could be followed repeatedly. This empirical study establishes an efficacious, feasible and sustainable method of wildlife disease management in an endemic epidemiological setting, something that is rare in the literature on wildlife disease control.

Altruistic behaviour is evolutionarily favoured through the action of kin selection. A simple mechanism for kin selection is population viscosity, whereby individuals do not move very far over the course of their lives, such that even indiscriminate helping of neighbours is liable to benefit one's genetic relatives. However, population viscosity is also associated with intensified resource competition among kin, which acts to inhibit the evolution of altruism. In standard models of population structure, these opposing effects of viscosity exactly cancel so that the evolutionary potential for altruism is completely invariant with respect to the rate of dispersal. Here, we investigate the consequences of load-balancing dispersal-whereby dispersers exhibit a preference for settling in less-crowded areas-for the evolution of altruism. Using mathematical modelling and individual-based computer simulations, we find that load-balancing dispersal dramatically reduces the kin-competition consequences of altruism, and thereby strongly promotes the evolution of altruism in viscous populations. We discuss other implications of such load-balancing dispersal for social evolution.

Invasion by non-native species threatens biodiversity, disrupts population dynamics and alters community composition. Roads are major contributors to the infiltration of non-native plants into adjacent native habitats. Less is known about whether these effects are magnified by the composite effects of other adjacent or overlapping disturbances. Here, we assessed how the spatial co-occurrence of wildfires and seismic lines associated with oil exploration influences the abundance of non-native plants along roads in Alberta, Canada's boreal forest. Specifically, we tested differences in the ratio of non-native to native plant cover between burned and unburned mesic upland boreal forests and on/off seismic lines, at increasing distances from roads. For unburned forest sites, non-native plant cover was highest adjacent to the road, decreasing threefold at the farthest distances. Wildfire and seismic line disturbances facilitated the infiltration of non-native species from roadsides into forests, but when combined, they produced an antagonistic effect that mitigated these effects, depending on the distance from roadsides. We found an equal ratio of non-native to native plant cover 7 m from road verges and declining thereafter. As natural and anthropogenic disturbances increase, understanding their combined influence on non-native plant invasion is essential for understanding threats and guiding effective conservation and management.

Food availability determines where and how animals use space across a landscape and, therefore, affects the risk of encounters leading to zoonotic spillover. This relationship is evident in Australian flying foxes (Pteropus spp.; fruit bats), where acute food shortages precede clusters of Hendra virus spillovers. Using machine learning, we predicted months of food shortages from climatological and ecological covariates (1996-2022) in subtropical Australia. Overall accuracy in predicting months of low food availability on a test set from 2018 up to 2022 reached 93.33 and 92.59% based on climatological and bat-level features, respectively. Seasonality and the Oceanic El Niño Index were the most important environmental features, while the number of bats in rescue centres and their body weights were the most important bat-level features. These models support predictive signals up to nine months in advance, facilitating action to mitigate spillover risk.

While many verte brates breed annually, there are a few that do not. Female sea turtles are a classic example of a generally non-annual nester, with often intervals between breeding seasons (termed the remigration interval) of 2-4 years. Non-annual nesting in sea turtles is believed to be due to long migration distances. While this hypothesis holds for populations where females migrate large distances (e.g. sometimes several 1000 km), it is harder to reconcile with cases where migration distances are short (e.g. sometimes <50 km). We show that even with very short breeding migrations, there are invariant time and energy costs to breeding. The time involved in the breeding process (migration, mating, nesting, internesting and returning to the foraging grounds) also comes with the opportunity cost of an individual being away from its foraging grounds and so lost foraging time. We show that this strategy of non-annual nesting is linked to high survival rates for adult sea turtles, a feature that is common across other non-annual breeders such as albatrosses and southern right whales.

Physical contests are critical in most animals in determining access to limited resources such as territories, food and sexual partners. Individuals should base their decision to engage and escalate a contest on the potential returns and the probability of winning against a specific opponent. Although variation in competitive ability should maintain variation in contest behaviour within populations, empirical evidence linking contest behaviour to competitive ability at the among- and within-individual levels remains limited. Here, we used an inbred line of the highly territorial and aggressive fly Drosophila prolongata to test how pre-existing variation in competitive ability drives phenotypic variation in contest behaviour. Specifically, we quantified the degree to which individual differences (i.e. individuality) in two key traits determining competitive ability, body size and weapon size, contribute to variation in territoriality and aggressiveness. Although territoriality and aggressiveness were repeatable, we found that behavioural plasticity in response to both focal and opponent morphological traits largely explains variation in both behaviours. Thus, even in the absence of genetic differences and under identical laboratory conditions, individuals consistently differ in contest behaviour while still adjusting their responses to the social context. We suggest that variation in the micro-environment, by shaping competitive ability through body size and weapon size, plays a crucial role in driving both between- and within-individual variation in social behaviour.

Infectious disease plays a key role in shaping marine communities, including in seagrass meadows, which form biodiverse coastal habitats. Eelgrass (Zostera marina) is the most widespread seagrass species and is susceptible to seagrass wasting disease, caused by the protist Labyrinthula zosterae. As a foundation species, eelgrass strongly influences ecosystem structure, function and services; recent work has begun to explore the links between critical community interactions and seagrass wasting disease. Here, we highlight recent advances about how the eelgrass community regulates and responds to seagrass wasting disease, from the microbiome to herbivores and filter feeders. We further show how efforts to model seagrass wasting disease progression can build on prior efforts to predict eelgrass growth and productivity and can inform our understanding of ecosystem health, resilience and vulnerability. As climate change alters environmental conditions, potentially favouring the wasting disease pathogen, efforts to integrate community interactions with disease ecology will be critical to forecast ecosystem dynamics and to develop effective coastal management strategies. We offer guidance on addressing major knowledge gaps in the study of eelgrass wasting disease in order to deepen both ecological theory and applied practices and identify how an integrated marine-disease-community ecology can inform a broader, cross-cutting understanding of disease.

Based on an interspecific comparison, Fernández-Martinez et al. (Fernández-Martinez et al. 2019 Nat. Plants5, 1222-1228 (doi:10.1038/s41477-019-0549-y)) found that masting is stronger in populations growing under conditions of nutrient scarcity, a relationship potentially providing a mechanistic link to resource-budget models of mast fruiting. Using comparisons among individual Quercus lobata, a common California masting oak species, we tested whether access to groundwater, foliar nitrogen (N) and foliar phosphorus (P) correlate with greater interannual acorn crop variability, increased synchrony of acorn production with other trees in the population and more negative lag-1 autocorrelations with acorn production the prior year-metrics indicative of masting-like behaviour. Our analyses failed to support the nutrient scarcity hypothesis. Three of the significant correlations between masting metrics and resources were in the opposite direction predicted by the hypothesis-trees with greater foliar N showed greater variability and synchrony in acorn production-while the other two (more water-stressed trees exhibited larger coefficient of variation (CV) in interannual acorn production) were apparently due to the inverse relationship between CV and mean overall productivity. More studies at different geographic and taxonomic scales and of other potentially important nutrients are needed to understand the relationship between masting and resources.

Exceptional preservation within the Mazon Creek Konservat-Lagerstätte has yielded unprecedented insights into Late Carboniferous flora and fauna including a wealth of information on extinct horseshoe crabs (Xiphosurida). Here, we document a unique specimen of the xiphosurid species Euproops danae that exhibits numerous dimple-like structures across the prosomal region. Comparison with modern horseshoe crabs suggests that these dimples may represent an algal or parasitic infestation that impacted the organism during life. This is the only known example of this infestation within the xiphosurid fossil record and provides evidence of life-stage-specific vulnerability, with dimpling indicating a terminal moult individual. These observations highlight the palaeobiological significance of pathological features within the fossil record and reinforce the value of Konservat-Lagerstätten in documenting ancient host-parasite interactions.

Copulation duration is a variable behaviour that is often extended by males beyond the time needed for sperm transfer. In many insect species, these prolonged matings have been linked to higher male reproductive success with virgin females. However, most matings in multiply mating species involve non-virgin females, whose role in shaping the evolution of this behaviour remains underexplored. Using hemiclonal analysis in Drosophila melanogaster, we tested whether males benefit from extended matings with non-virgin females by comparing competitive fertilization success (P2) between males from three long-mating and three short-mating hemiclone lines. We confirmed that differences among hemiclone lines in male mating duration with virgin females persisted with non-virgin females and that these longer matings were associated with higher P2, demonstrating a clear fitness benefit to males. These findings build on past work showing that longer matings increase male defensive reproductive success, highlighting the adaptive value of prolonged matings for males in multiply mating species and underscoring the importance of including non-virgin females in studies of sexual selection and reproductive behaviour.