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AbstractEnvironmental stress is one of the important causes of biological dispersal. At the same time, the process of dispersal itself can incur and/or increase susceptibility to stress for the dispersing individuals. Therefore, in principle, stress can serve as both a cause and a cost of dispersal. We studied these potentially contrasting roles of a key environmental stress (desiccation) using Drosophila melanogaster. By modulating water and rest availability, we asked whether (a) dispersers are individuals that are more susceptible to desiccation stress, (b) dispersers pay a cost in terms of reduced resistance to desiccation stress, (c) dispersal evolution alters the desiccation cost of dispersal, and (d) females pay a reproductive cost of dispersal. We found that desiccation was a clear cause of dispersal in both sexes, as both male and female dispersal propensity increased with increasing duration of desiccation. However, the desiccation cost of dispersal was male biased, a trend unaffected by dispersal evolution. Instead, females paid a fecundity cost of dispersal. We discuss the complex relationship between desiccation and dispersal, which can lead to both positive and negative associations. Furthermore, the sex differences highlighted here may translate into differences in movement patterns, thereby giving rise to sex-biased dispersal patterns.AbstractThe distributions of marine ectotherms are governed by physiological sensitivities to long-term trends in seawater temperature and dissolved oxygen. Short-term variability in these parameters has the potential to facilitate rapid range expansions, and the resulting ecological and socioeconomic consequences may portend those of future marine communities. Here, we combine physiological experiments with ecological and demographic surveys to assess the causes and consequences of sudden but temporary poleward range expansions of a marine ectotherm with considerable life history plasticity (California market squid, Doryteuthis opalescens). We show that sequential factors related to resource accessibility in the core range-the buildup of large populations as a result of competitive release and climate-associated temperature increase and oxygen loss that constrain aerobic activity-may drive these expansions. We also reveal that poleward range expansion alters the body size-and therefore trophic role-of invading populations, with potential negative implications for socioeconomically valuable resident species. To help forecast rapid range expansions of marine ectotherms, we advocate that research efforts focus on factors impacting resource accessibility in core ranges. Determining how environmental conditions in receiving ecosystems affect body size and how body size is related to trophic role will help refine estimates of the impacts of future marine communities.AbstractIndividual metabolism generally scales with body mass with an exponent around 3/4. From dimensional arguments it follows that maximum population growth rate (rmax) scales with a -1/4 exponent. However, the dimensional argument implicitly assumes that offspring size is proportional to adult size. Here, we calculate rmax from metabolic scaling at the level of individuals within size-structured populations while explicitly accounting for offspring size. We identify four general patterns of how rmax scales with adult mass based on four empirical life history patterns employed by groups of species. These life history patterns are determined by how traits of somatic growth rate and/or offspring mass relate to adult mass. One life history pattern-constant adult-to-offspring mass ratio and somatic growth rate independent of adult mass-leads to the classic -1/4 scaling of rmax. The other three life history patterns either lead to nonmetabolic population growth scaling with adult mass or do not follow a power-law relationship at all. Using life history data on five marine taxa and terrestrial mammals, we identify species groups that belong to one of each case. We predict that elasmobranchs, copepods, and mammals follow standard -1/4 power-law scaling, whereas teleost fish and bivalves do not have a pure power-law scaling. Our work highlights how taxa may deviate from the classic -1/4 metabolic scaling pattern of maximum population growth. The approach is generic and can be applied to any taxa.AbstractFunctionally variable symbionts commonly co-occur including within the roots of individual plants, in spite of arguments from simple models of the stability of mutualism that predict competitive exclusion among symbionts. We explore this paradox by evaluating the dynamics generated by symbiont competition for plant resources and the plant's preferential allocation to the most beneficial symbiont using a system of differential equations representing the densities of mutualistic and nonmutualistic symbionts and the level of preferentially allocated and nonpreferentially allocated resources for which the symbionts compete. We find that host preferential allocation and costs of mutualism generate resource specialization that makes the coexistence of beneficial and nonbeneficial symbionts possible. Furthermore, coexistence becomes likely because of negative physiological feedbacks in host preferential allocation. We find that biologically realistic models of plant physiology and symbiont competition predict that the coexistence of beneficial and nonbeneficial symbionts should be common in root symbioses and that the density and relative abundance of mutualists should increase in proportion to the needs of the host.AbstractUnderstanding within-population variation in aging rates across different phenotypic traits is a central focus of biogerontological studies. Early evolutionary models predict that natural selection acts to cause all traits to deteriorate simultaneously. However, observations of aging rates provide evidence for widespread patterns of asynchronous aging in laboratory and natural populations. Recent verbal models put forth to explain such observations argue that because senescence is costly to fitness, selection should cause phenotypic traits that are most important to fitness to senesce slower than traits that are less related to fitness. Here, we show that formal evolutionary theory supports neither prediction. Instead, we find that selection will favor the evolution of the most rapid rates of aging in those traits that are under the strongest selection at early ages because selection for these traits erodes the fastest. This reinforces the expectation that natural selection should play a role in the evolution of among-trait variation in aging, but in a contradictory way to that suggested previously. We demonstrate how to quantify age-specific sources of selection for age-specific traits and how these estimates can be used to understand how well patterns of age-related changes in selection can explain observed patterns of among-trait variation in aging rates.AbstractSupply and demand affect the values of goods exchanged in cooperative trades. Studies of humans and other species typically describe the standard scenario that an increase in demand leads to a higher price. Here, we challenge the generality of that logic with empirical data and a theoretical model. In our study system, "client" fishes visit cleaner wrasse (Labroides dimidiatus) to have ectoparasites removed, but cleaners prefer client mucus, which constitutes "cheating." We removed 31 of 65 preselected cleaners from a large isolated reef patch. We compared cleaner-client interactions at the reef and a control reef before removal and 4 weeks after removal. Cleaner fish from the experimental treatment site interacted more frequently with large clients (typically visitors with access to alternative cleaning stations), but we did not observe any changes in service quality measures. A game-theoretic analysis revealed that interaction duration and service quality might increase, decrease, or remain unchanged depending on the precise relationships between key parameters, such as the marginal benefits of cheating as a function of satiation or the likelihood of clients responding to cheating as a function of market conditions. The analyses show that the principle of diminishing return may affect exchanges in ways not predicted by supply-to-demand ratios.Objective COVID-19 and lockdown measures impacted mental health globally and had a particular impact on patients with substance use disorders (SUD). However, the impact of gender, age, and dual diagnosis on consumption patterns and mental health during COVID-19 lockdown among patients with SUD has not been analyzed in depth. Therefore, this study aimed to examine substance use and mental health status during COVID-19 lockdown considering gender, age, and previous dual diagnosis in patients with SUD treated in different outpatient addiction clinics in Catalonia. Methods Thirteen clinics participated and 588 patients were enrolled in the study, of whom 70.7% were men and 29.3% were women. The mean age was 48 ± 11.3 years, and 63.2% had dual diagnoses. Results Men reported significantly more frequent alcohol and cocaine consumption during lockdown, while women experienced more anxiety and depressive symptoms. [https://www.selleckchem.com/products/ml390.html ML390 nmr] Younger patients more frequently reported consuming cocaine and cannabis, breaking the lockdown rule, worsened family relationships, and reduced incomes. Older patients more frequently reported maintaining abstinence. Previous dual diagnosis was more often associated with benzodiazepine use disorder, less active working during lockdown, and more anxiety and depressive symptoms than not having previous dual diagnosis. Conclusions Both new psychiatric symptoms and general worsening of existing symptoms were frequent during the lockdown. Differences based on the gender, age, and dual diagnosis of outpatients treated for substance use disorders should be considered in the planning of protection measures such as home confinement.Mucormycosis is an opportunistic fungal disease that targets individuals having an impaired immune system due to a wide array of risk factors including HIV-AIDS, immunosuppressive therapy, diabetes mellitus, etc. The current explosive outbreak of coronavirus disease 2019 (COVID-19) has become the latest threat to such patients who are already susceptible to secondary infections. Physiological outcomes of COVID-19 end up in a cascade of grave alterations to the immunological profile and irreparable harm to their respiratory passage, heart and kidneys. Corticosteroidal treatment facilitates faster recovery and alleviates the adverse pathological effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). But clinical reports lend this approach a darker perspective especially if these patients have pre-existing diabetes mellitus. The mucormycotic fungal genera belonging to the order Mucorales not only survive but thrive under the comorbidity of COVID-19 and diabetes, often staying undetected until they have inflicted irreversible damage. Steroidal usage has been noted to be a common thread in the sudden spurt in secondary fungal infections among COVID-19 cases. Once considered a rare occurrence, mucormycosis has now acquired a notoriously lethal status in mainstream medical hierarchy. We set out to investigate whether corticosteroidal therapy against COVID-19 emboldens the development of mucormycosis. We also assess the conditions brought forth by steroidal usage and uncontrolled progression of diabetes in COVID-19 cases and their effect on the susceptibility towards mucormycosis.