Spread dynamics of invasive species

Species invasions are a principal component of global change, causing large losses in biodiversity as well as economic damage. Invasion theory attempts to understand and predict invasion success and patterns of spread. However, there is no consensus regarding which species or community attributes enhance invader success or explain spread dynamics. Experimental and theoretical studies suggest that regulation of spread dynamics is possible; however, the conditions for its existence have not yet been empirically demonstrated. If invasion spread is a regulated process, the structure that accounts for this regulation will be a main determinant of invasion dynamics. Here we explore the existence of regulation underlying changes in the rate of new site colonization. We employ concepts and analytical tools from the study of abundance dynamics and show that spread dynamics are, in fact, regulated processes and that the regulation structure is notably consistent among invasions occurring in widely different contexts. We base our conclusions on the analysis of the spread dynamics of 30 species invasions, including birds, amphibians, fish, invertebrates, plants, and a virus, all of which exhibited similar regulation structures. In contrast to current beliefs that species invasions are idiosyncratic phenomena, here we provide evidence that general patterns do indeed exist.     

The impact of minimally invasive surgery and frailty on post-hepatectomy outcomes

BackgroundThe impact of patient frailty on post-hepatectomy outcomes is not well studied. We hypothesized that patient frailty is a strong predictor of 30-day post-hepatectomy complications.MethodsThe liver-targeted National Surgical Quality Improvement Program (NSQIP) database for 2014–2019 was reviewed. A validated modified frailty index (mFI) was used.ResultsA total of 24,150 hepatectomies were reviewed. Worsening frailty was associated with increased incidence of Clavien-Dindo grade IV complications (mFI 0, 1, 2, 3, 4 was 3.9%, 6.3%, 10%, 8.1%, 50% respectively; p < 0.001). Minimally invasive hepatectomies had a lower rate of Clavien-Dindo grade IV complications for non-frail (Laparoscopic: 1%, Robotic: 2.6%, Open: 4.6%; p < 0.001) and frail patients (Laparoscopic: 3%, Robotic: 2.3%, Open: 7.7%; p < 0.001). Frail patients experienced higher incidence of post-hepatectomy liver failure (5.4% vs 4.1% for non-frail; p < 0.001) and grade C liver failure (28% vs 21.1% for non-frail; p = 0.03). Incorporating mFI to Albumin-Bilirubin score (ALBI) improved its ability to predict Clavien-Dindo grade IV complications (AUC improved from 0.609 to 0.647; p < 0.001) and 30-day mortality (AUC improved from 0.663 to 0.72; p < 0.001).ConclusionWorsening frailty correlates with increased incidence of Clavien-Dindo grade IV complications post-hepatectomy, whereas minimally invasive approaches decrease this risk. Incorporating frailty assessment to ALBI improves its ability to predict major postoperative complications and 30-day mortality.     

Community disassembly by an invasive species

Invasive species pose serious threats to community structure and ecosystem function worldwide. The impacts of invasive species can be more pervasive than simple reduction of species numbers. By using 7 years of data in a biological preserve in northern California, we documented the disassembly of native ant communities during an invasion by the Argentine ant. In sites without the Argentine ant, native ant communities exhibit significant species segregation, consistent with competitive dynamics. In sites with the Argentine ant, native ant communities appear random or weakly aggregated in species co-occurrence. Comparisons of the same sites before and after invasion indicate that the shift from a structured to a random community is rapid and occurs within a year of invasion. Our results show that invasive species not only reduce biodiversity but rapidly disassemble communities and, as a result, alter community organization among the species that persist.     

New pasture plants intensify invasive species risk

Agricultural intensification is critical to meet global food demand, but intensification threatens native species and degrades ecosystems. Sustainable intensification (SI) is heralded as a new approach for enabling growth in agriculture while minimizing environmental impacts. However, the SI literature has overlooked a major environmental risk. Using data from eight countries on six continents, we show that few governments regulate conventionally bred pasture taxa to limit threats to natural areas, even though most agribusinesses promote taxa with substantial weed risk. New pasture taxa (including species, subspecies, varieties, cultivars, and plant-endophyte combinations) are bred with characteristics typical of invasive species and environmental weeds. By introducing novel genetic and endophyte variation, pasture taxa are imbued with additional capacity for invasion and environmental impact. New strategies to prevent future problems are urgently needed. We highlight opportunities for researchers, agribusiness, and consumers to reduce environmental risks associated with new pasture taxa. We also emphasize four main approaches that governments could consider as they build new policies to limit weed risks, including (i) national lists of taxa that are prohibited based on environmental risk; (ii) a weed risk assessment for all new taxa; (iii) a program to rapidly detect and control new taxa that invade natural areas; and (iv) the polluter-pays principle, so that if a taxon becomes an environmental weed, industry pays for its management. There is mounting pressure to increase livestock production. With foresight and planning, growth in agriculture can be achieved sustainably provided that the scope of SI expands to encompass environmental weed risks.Livestock production is already the largest land use on earth, accounting for 30% of global land area (1). Nevertheless, growing demand means that production must rise more than 50% by 2050 (2) as global population size and per capita consumption increase (2–5). Responding to this demand, agribusiness^* is developing and marketing new taxa^† of forage plants designed to increase pasture productivity. Through artificial selection and hybridization, public and private organizations are developing plant taxa that are more productive and more tolerant of disease and environmental extremes. At the same time, there is a strong campaign for sustainable intensification (SI) of agriculture. One approach to SI is to increase production on some lands while sparing others for conservation (5, 6). Agricultural intensification using new pasture taxa may thus be an efficient way to help meet rising demand and reduce some of the social and environmental costs of traditional agriculture (5). However, perversely, it may drive another environmental problem because pasture plants can invade the native ecosystems that “land sparing” is designed to protect (7).Environmental weeds are invasive alien plants that establish in natural areas (e.g., remnant native vegetation and conservation reserves), usually to the detriment of native species (8). Environmental weeds threaten biodiversity, compromise ecosystem function, and cost billions of dollars to manage each year (9–15). Many have been introduced as pasture forages (7). For example, in Australia, the introduced pasture species Andropogon gayanus (gamba grass) increases wildfire intensity fivefold, reducing carbon stores and transforming species-rich native savannah to exotic-dominated grassland. Predicted to invade up to 380,000 km² of northern Australia (16), gamba grass invasion has increased the cost of fire management by an order of magnitude, from less than AUD$2000 for each fire to as much as AUD$43,000 per fire (16). The possibility that SI may worsen problems like these warrants serious consideration, yet the topic remains controversial and the risks are not fully acknowledged (Fig. 1) (5, 17).Open in a separate windowFig. 1.The Undoolya Wattle Acacia undoolyana, nationally listed as vulnerable, standing dead in a sea of invasive pasture grasses (largely buffelgrass Pennisetum ciliare). This species occurs in several small populations in a 165-km² area of the East McDonnell Ranges in central Australia. Fires in 2013 killed many of the trees in the N''Dahla Gorge population (pictured). Although the wattle is threatened by hot fires, the dominant role that buffelgrass plays in altering the fire regime is not mentioned on the information board. Introduced pasture grasses are contentious in the Australian rangelands because they are used by the cattle industry, but also are highly invasive, fueling intense fires that kill woody plants and transform ecosystems. Photograph by D.A.D.Here, we take a global perspective to consider whether new pasture taxa are likely to become environmental weeds (hereafter “environmental weed risk”) and whether there are mechanisms in place to limit potential risks. Although we focus specifically on the risk of new pasture taxa becoming environmental weeds, we acknowledge that very similar risks, and likely solutions, apply to other systems of production including bioenergy (18, 19), carbon sequestration (20), forestry (21), and horticulture (21, 22). We find that increased environmental weed risk from new pasture taxa presents a major challenge to increasing livestock production in a way that is consistent with SI (5). Nevertheless, there are practical solutions to reduce these risks that can be informed by new research and extend from government regulation to responsible product development and consumer choice (Fig. 2).Open in a separate windowFig. 2.Pathways influencing the risk that pasture taxa will invade natural areas and become environmental weeds. Currently, (A) economic models inadequately accommodate long-term social and environmental costs. Governments impose few or no regulations on new pasture taxa despite having to provide public funds to manage environmental weeds that were initially introduced as pasture. Most research into new taxa does not consider environmental weed risk. With little self-regulation, agribusiness may therefore inadvertently increase the environmental weed risk. Solutions to these problems (B) include closer interaction and feedback among researchers, government, and industry, government initiatives to promote low-risk pasture development, and industry-led certification enabling consumers to reward environmentally responsible pasture development. ^*See Fig. 3 regarding protocols for weed risk assessment.     

The emergence of non-albicans Candida species as causes of invasive candidiasis and candidemia

The last three decades have seen an expanding pool of high-risk patients susceptible to the opportunistic pathogen Candida. Accordingly, a dramatic increase in nosocomial blood stream infections (BSIs) due to Candida spp has been reported throughout the world, starting in tertiary care centers and spreading to community hospitals. This absolute increase in Candida BSIs was accompanied by both an absolute and then a proportional increase in invasive infection caused by reduced fluconazole-susceptible non-albicans Candida spp. Currently, the incidence trend of BSI has stabilized, and Candida albicans remains the most common species causing fungal BSI. Clinicians must be aware of the importance and implications of non-albicans Candida spp when selecting antifungal drugs, although most studies have not shown significant outcome differences with use of the various antifungal classes.     

Increased genetic variation and evolutionary potential drive the success of an invasive grass

Despite the increasing biological and economic impacts of invasive species, little is known about the evolutionary mechanisms that favor geographic range expansion and evolution of invasiveness in introduced species. Here, we focus on the invasive wetland grass Phalaris arundinacea L. and document the evolutionary consequences that resulted from multiple and uncontrolled introductions into North America of genetic material native to different European regions. Continental-scale genetic variation occurring in reed canarygrass' European range has been reshuffled and recombined within North American introduced populations, giving rise to a number of novel genotypes. This process alleviated genetic bottlenecks throughout reed canarygrass' introduced range, including in peripheral populations, where depletion of genetic diversity is expected and is observed in the native range. Moreover, reed canarygrass had higher genetic diversity and heritable phenotypic variation in its invasive range relative to its native range. The resulting high evolutionary potential of invasive populations allowed for rapid selection of genotypes with higher vegetative colonization ability and phenotypic plasticity. Our results show that repeated introductions of a single species may inadvertently create harmful invaders with high adaptive potential. Such invasive species may be able to evolve in response to changing climate, allowing them to have increasing impact on native communities and ecosystems in the future. More generally, multiple immigration events may thus trigger future adaptation and geographic spread of a species population by preventing genetic bottlenecks and generating genetic novelties through recombination.     

Self-organized similarity, the evolutionary emergence of groups of similar species

Ecologists have long been puzzled by the fact that there are so many similar species in nature. Here we show that self-organized clusters of look-a-likes may emerge spontaneously from coevolution of competitors. The explanation is that there are two alternative ways to survive together: being sufficiently different or being sufficiently similar. Using a model based on classical competition theory, we demonstrate a tendency for evolutionary emergence of regularly spaced lumps of similar species along a niche axis. Indeed, such lumpy patterns are commonly observed in size distributions of organisms ranging from algae, zooplankton, and beetles to birds and mammals, and could not be well explained by earlier theory. Our results suggest that these patterns may represent self-constructed niches emerging from competitive interactions. A corollary of our findings is that, whereas in species-poor communities sympatric speciation and invasion of open niches is possible, species-saturated communities may be characterized by convergent evolution and invasion by look-a-likes.     

The impact of penicillin resistance on the outcome of invasive Streptococcus pneumoniae infection in children

Background: Invasive infections caused by Streptococcus pneumoniae with reduced susceptibility to penicillin are increasing in prevalence in Australia. Aims: To determine the impact of reduced susceptibility of S. pneumoniae to penicillin on morbidity, mortality and treatment of invasive infection. Methods: Retrospective case note review of children with invasive S. pneumoniae infection over a 26 month period. Penicillin minimum inhibitory concentrations (MIC) were determined by E test. Primary clinical outcome measures included days to defervescence, duration of hospital stay, complication rates and mortality. The secondary outcome of financial cost was examined. Comparisons between outcomes of patients with infections caused by susceptible and non‐susceptible strains were performed with Student's t test. Pearson χ², Mann‐Whitney U tests and multiple logistic regression. Results: Sixty‐eight episodes of invasive pneumococcal disease were reviewed: 14 isolates (21.1%) had reduced susceptibility or resistance to penicillin (PNSSP, MIC 0.125 mg/L‐1.5 mg/L). Ten patients had meningitis, 21 had pneumonia, 22 had bacteraemia with another focus and 15 had bacteraemia without an obvious focus. PNSSP were more common in patients with meningitis and pneumonia. No patients died. Overall, patients with infections caused by PNSSP had significandy longer hospitalisation and longer time to defervescence. Complication rates were not significantly different between groups. Outcome differences were no longer significant when meningitis patients were excluded from the analysis. The PNSSP group received more expensive intravenous antibiotics and their infections were significandy more costly to treat. Conclusions: Infections widi penicillin non‐susceptible S. pneumoniae are associated with higher morbidity than infections with penicillin susceptible strains, and treatment of diese infections is more expensive, due to higher drug costs and longer hospital stay.     

From the Cover: Wildfire,climate, and invasive grass interactions negatively impact an indicator species by reshaping sagebrush ecosystems

Iconic sagebrush ecosystems of the American West are threatened by larger and more frequent wildfires that can kill sagebrush and facilitate invasion by annual grasses, creating a cycle that alters sagebrush ecosystem recovery post disturbance. Thwarting this accelerated grass–fire cycle is at the forefront of current national conservation efforts, yet its impacts on wildlife populations inhabiting these ecosystems have not been quantified rigorously. Within a Bayesian framework, we modeled 30 y of wildfire and climatic effects on population rates of change of a sagebrush-obligate species, the greater sage-grouse, across the Great Basin of western North America. Importantly, our modeling also accounted for variation in sagebrush recovery time post fire as determined by underlying soil properties that influence ecosystem resilience to disturbance and resistance to invasion. Our results demonstrate that the cumulative loss of sagebrush to direct and indirect effects of wildfire has contributed strongly to declining sage-grouse populations over the past 30 y at large spatial scales. Moreover, long-lasting effects from wildfire nullified pulses of sage-grouse population growth that typically follow years of higher precipitation. If wildfire trends continue unabated, model projections indicate sage-grouse populations will be reduced to 43% of their current numbers over the next three decades. Our results provide a timely example of how altered fire regimes are disrupting recovery of sagebrush ecosystems and leading to substantial declines of a widespread indicator species. Accordingly, we present scenario-based stochastic projections to inform conservation actions that may help offset the adverse effects of wildfire on sage-grouse and other wildlife populations.Wildfire is a common disturbance whose effects on ecosystem processes vary spatiotemporally and are mediated by climate, soil, and resulting vegetation (1, 2). These effects influence thresholds that govern shifts to alternative ecological states post disturbance that have new functional and possibly hysteretic properties compared with the predisturbed state (3, 4). Invasion by nonnative species following disturbance can then promote additional strong feedbacks that drive an ecosystem further from its original state (5), and may ultimately yield a novel ecosystem that has no historical analog (6, 7).In conservation planning, fragile ecosystems have a defining characteristic of high species turnover following disturbance (8), and altered fire regimes in these ecosystems can act as a disturbance driving state transitions across multiple spatiotemporal scales (2). The Great Basin of North America is a 541,727-km² cold desert dominated by sagebrush (Artemisia spp.) shrubland in the American West that provides a timely example of how altered wildfire regimes fueled by invasive species can drive rapid changes within fragile ecosystems at enormous spatial scales (9). The Great Basin intersects six states and is larger than 75% of countries worldwide; hence, perturbations to this ecoregion have significant ecological and sociopolitical ramifications that are at the forefront of national conservation and fire management policy (10). Wildfire frequency and size have increased significantly in the majority of this ecoregion since the 1980s (11) due, in large part, to synergistic interactions with invading cheatgrass (Bromus tectorum), an annual grass native to Eurasia (9, 12). Incipient risks of degradation of sagebrush by transition to cheatgrass-dominated grasslands that readily burn were recognized by Aldo Leopold over half a century ago (13), and the positive feedback loop between wildfire and cheatgrass invasion is now recognized as the primary mechanism altering contemporary sagebrush ecosystems of the Great Basin (14). Wildfire kills individuals of nearly all subspecies of big sagebrush (Artemisia tridentata), which have inherently slow growth rates and do not resprout (15); thus, cheatgrass can dominate burned landscapes and spread wildfire to sagebrush that would otherwise be less prone to burning (9, 12, 16).Evaluating population or community response to state transitions, especially within ecologically meaningful time frames, is an important component for monitoring the effectiveness of conservation actions aimed at mitigating or thwarting these changes (17). In the case of the cheatgrass–fire cycle, rangeland ecologists increasingly emphasize management practices that understand factors driving resilience to wildfire and resistance to cheatgrass (hereinafter, R&R), which are influenced strongly by soil moisture and temperature regimes in semiarid ecosystems such as the Great Basin (14, 18). However, responses of vertebrate populations inhabiting sagebrush ecosystems have not been linked empirically to altered disturbance regimes (e.g., the cheatgrass–fire cycle) or underlying factors influencing sagebrush ecosystem R&R across large spatiotemporal scales despite their obvious importance from a conservation perspective (10, 19).The greater sage-grouse (Centrocercus urophasianus; hereinafter, sage-grouse) is a large gallinaceous bird that can be an indicator for ecological health in sagebrush ecosystems because it requires distinct ecological states to fulfill its diverse life-history requirements (20). Hence, population dynamics of the species are an ideal metric for assessing linkages to specific sagebrush disturbances. Populations of this sagebrush obligate have declined concomitantly with the overall loss and fragmentation of sagebrush following settlement of the American West, and the species now occupies approximately one-half of its historic distribution (21). Accordingly, the species has undergone multiple evaluations for protection under the Endangered Species Act, the most recent of which stimulated unprecedented amendments to land management policy (with an emphasis on R&R) across millions of acres of federally managed land (10, 19). Critical to these large-scale efforts is a sound understanding of how sage-grouse populations respond to spatiotemporal variation in wildfire, while accounting for modeled postwildfire recovery times and R&R-dependent probability of state transition to cheatgrass, as well as complex relationships with climatic and demographic processes (22, 23). Direct and indirect effects of wildfire have been identified qualitatively as a threat to sage-grouse persistence in the western portion of their range (11). However, we lack rigorous and long-term evaluations that quantify mechanisms (e.g., wildfire) driving prevailing trends in sage-grouse population size and can identify populations most at risk. Long-term evaluations are needed because sage-grouse populations can cycle over periods of less than ∼10 y (24), thus studies with durations shorter than the typical cyclical period may reveal population growth patterns running counter to actual long-term trajectories.Species using central-placed breeding strategies, such as lek breeding sage-grouse (25), are especially well-suited for spatially explicit and large-scale analyses of the effects of environmental and demographic stochasticity on population rate of change (26). In this study, we used a Bayesian analytical framework (Fig. S1) to link sage-grouse annual population rate of change (λ, as measured from yearly counts of male sage-grouse attending leks; Materials and Methods) to different measures of wildfire and seasonal precipitation while accounting for R&R-related recovery processes and density-dependent effects over a 30-y period (1985–2013) across the Great Basin (Fig. 1 and Fig. S2). Spatially explicit estimates of wildfire deemed severe enough to drive a change in vegetation were generated from the Monitoring Trends of Burn Severity Database (27) (MTBS; Materials and Methods). Spatially explicit estimates of sagebrush recovery, defined as 20% of prefire sagebrush cover that can fulfill partial life-history requirements for sage-grouse (28), were modeled by calculating cumulative burned area (CBA) within 5–10 km of leks on an annual basis (26, 29). Recovery times were based on three index classes for R&R (high, moderate, and low) extracted from a recently published map of spatially explicit soil moisture and temperature regimes (18) that strongly influence R&R in sagebrush ecosystems (14) (SI Materials and Methods, Fig. S3, and Table S1). Burned areas within high and moderate R&R index classes (cool and moist soils) were assigned to respective fast-track and slow-track recovery rates, based on a meta-analysis of sagebrush postfire recovery (30), whereas burned areas within the low R&R index class (warm and dry soils) were assumed to reflect a permanent state transition to invasive grassland (31) (Table S2). We also considered interactions with precipitation because water availability is integral to ecosystem productivity in cold deserts like the Great Basin (32), and can drive sage-grouse population dynamics independent of wildfire (22, 33). Using model-derived parameters of fire effects on λ, we then projected sage-grouse populations 30 y into the future and identified a fire suppression strategy that may slow or halt projected declines.Fig. 1.Map of CBA by R&R (high, moderate, and low) index class across the Great Basin of western North America over three decades as of 2013. High and moderate areas were predicted as undergoing recovery to sagebrush, whereas low areas were predicted ...     

Evolutionary limits ameliorate the negative impact of an invasive plant

Invasive species can quickly transform biological communities due to their high abundance and strong impacts on native species, in part because they can be released from the ecological forces that limit native populations. However, little is known about the long-term dynamics of invasions; do invaders maintain their dominant status over long time spans, or do new ecological and evolutionary forces eventually develop to limit their populations? Alliaria petiolata is a Eurasian species that aggressively invades North American forest understories, in part due to the production of toxic phytochemicals. Here we document a marked decline in its phytotoxin production and a consequent decline in their impact on three native species, across a 50+ year chronosequence of Alliaria petiolata invasion. Genetic evidence suggests that these patterns result from natural selection for decreased phytotoxin production rather than founder effects during introduction and spread. These patterns are consistent with the finding of slowing A. petiolata population growth and rebounding native species abundance across a separate chronosequence in Illinois, U.S. These results suggest that this invader is developing evolutionary limits in its introduced range and highlight the importance of understanding the long-term processes that shape species invasions and their impacts.     

The impact of human-made ecological changes on the genetic architecture of Daphnia species

The overenrichment (eutrophication) of aquatic ecosystems with nutrients leading to algal blooms and anoxic conditions has been a persistent and widespread environmental problem. Although there are many studies on the ecological impact of elevated phosphorus (P) levels (e.g., decrease in biodiversity and water quality), little is known about the evolutionary consequences for animal species. We reconstructed the genetic architecture of a Daphnia species complex in 2 European lakes using diapausing eggs that were isolated from sediment layers covering the past 100 years. Changes in total P were clearly associated with a shift in species composition and the population structure of evolutionary lineages. Although environmental conditions were largely re-established after peak eutrophication during the 1970s and 1980s, original species composition and the genetic architecture of species were not restored but evolved along new evolutionary trajectories. Our data demonstrate that anthropogenically induced temporal alterations of habitats are associated with long-lasting changes in communities and species via interspecific hybridization and introgression.     

Risk assessment for invasive species produces net bioeconomic benefits

International commerce in live organisms presents a policy challenge for trade globalization; sales of live organisms create wealth, but some nonindigenous species cause harm. To reduce damage, some countries have implemented species screening to limit the introduction of damaging species. Adoption of new risk assessment (RA) technologies has been slowed, however, by concerns that RA accuracy remains insufficient to produce positive net economic benefits. This concern arises because only a small proportion of all introduced species escape, spread, and cause harm (i.e., become invasive), so a RA will exclude many noninvasive species (which provide a net economic benefit) for every invasive species correctly identified. Here, we develop a simple cost:benefit bioeconomic framework to quantify the net benefits from applying species prescreening. Because invasive species are rarely eradicated, and their damages must therefore be borne for long periods, we have projected the value of RA over a suitable range of policy time horizons (10-500 years). We apply the model to the Australian plant quarantine program and show that this RA program produces positive net economic benefits over the range of reasonable assumptions. Because we use low estimates of the financial damage caused by invasive species and high estimates of the value of species in the ornamental trade, our results underestimate the net benefit of the Australian plant quarantine program. In addition, because plants have relatively low rates of invasion, applying screening protocols to animals would likely demonstrate even greater benefits.     

Reduced genetic variation and the success of an invasive species

Despite the severe ecological and economic damage caused by introduced species, factors that allow invaders to become successful often remain elusive. Of invasive taxa, ants are among the most widespread and harmful. Highly invasive ants are often unicolonial, forming supercolonies in which workers and queens mix freely among physically separate nests. By reducing costs associated with territoriality, unicolonial species can attain high worker densities, allowing them to achieve interspecific dominance. Here we examine the behavior and population genetics of the invasive Argentine ant (Linepithema humile) in its native and introduced ranges, and we provide a mechanism to explain its success as an invader. Using microsatellite markers, we show that a population bottleneck has reduced the genetic diversity of introduced populations. This loss is associated with reduced intraspecific aggression among spatially separate nests, and leads to the formation of interspecifically dominant supercolonies. In contrast, native populations are more genetically variable and exhibit pronounced intraspecific aggression. Although reductions in genetic diversity are generally considered detrimental, these findings provide an example of how a genetic bottleneck can lead to widespread ecological success. In addition, these results provide insights into the origin and evolution of unicoloniality, which is often considered a challenge to kin selection theory.     

The impact of marginal lung function on outcomes in the era of minimally invasive thoracic surgery

BackgroundThe effect of marginal lung function on outcomes after lung resection has traditionally been studied in the context of open thoracic surgery. Its impact on postoperative outcomes in the era of minimally invasive lung resection is unclear.MethodsIn this retrospective cohort study, we included adult patients who underwent minimally invasive lung resection at our institution between January 2017 and May 2020 for known malignancy or lung nodule. Marginal lung function was defined as pre-operative forced expiratory volume in 1 second (FEV1) and/or diffusion lung capacity of carbon monoxide <60% of predicted. Our outcomes included a composite outcome of pulmonary morbidity and/or 30- and 90-day mortality, and hospital length of stay. We used multivariable logistic and Poisson regression models to identify associations with outcomes, and Kaplan-Meier and Cox models to estimate survival.ResultsOf 300 patients, 88 (29%) had marginal lung function. Patients in the marginal group were more likely to be female (69% vs. 56%; P=0.028), and more likely to have: hypertension (HTN) (83% vs. 71%; P=0.028), chronic obstructive pulmonary disease (COPD) (38% vs. 12%; P<0.001), interstitial lung disease (ILD) (9% vs. 3%; P<0.019), and ischemic heart disease (28% vs. 18%; P=0.033). Patients were similar in terms of age (68±8 vs. 68±10 years; P=0.932), and other comorbidities. Anatomic lung resection comprised 56.8% of the marginal group vs. 74% in the non-marginal group (P=0.003). The most common complication was prolonged air leak (18.2% vs. 11.8%; P=0.479). Marginal lung function had a trend toward increased composite respiratory complications (22.7% vs. 15.1%; P=0.112) and 90-day mortality (5.7% vs. 4.2%; P=0.591), although they did not reach statistical significance. There was a statistically significant 1-day average increase in length of stay in the marginal lung function cohort (4.6 vs. 3.4 days; P<0.015) with a stronger association with diffusion lung capacity of carbon monoxide than FEV1. Survival was similar (marginal function HR =1.0; P=0.994).ConclusionsIn the era of minimally invasive thoracic surgery, lung resection in patients with marginal lung function may be considered in select patients. These findings aid in the selection consideration and counseling of this patient population.     

The differential clinical impact of human coronavirus species in children with cystic fibrosis

We investigated the clinical impact of human coronaviruses (HCoV) OC43, 229E, HKU1 and NL63 in pediatric patients with cystic fibrosis (CF) during routine and exacerbation visits. A total of 408 nasopharyngeal aspirate samples were obtained from 103 patients over a 1-year period. Samples positive for HCoV were submitted for nucleotide sequencing to determine the species. Nineteen samples (4.65%) were positive for HCoV, of which 8 were positive for NL63, 6 for OC43, 4 for HKU1, and 1 for 229E. Identification of HCoV was not associated with an increased rate of respiratory exacerbations, but NL63-positive patients had higher exacerbation rates than patients who were positive for other HCoV species.     

Whole-genome analysis reveals molecular innovations and evolutionary transitions in chromalveolate species

The chromalveolates form a highly diverse and fascinating assemblage of organisms, ranging from obligatory parasites such as Plasmodium to free-living ciliates and algae such as kelps, diatoms, and dinoflagellates. Many of the species in this monophyletic grouping are of major medical, ecological, and economical importance. Nevertheless, their genome evolution is much less well studied than that of higher plants, animals, or fungi. In the current study, we have analyzed and compared 12 chromalveolate species for which whole-sequence information is available and provide a detailed picture on gene loss and gene gain in the different lineages. As expected, many gene loss and gain events can be directly correlated with the lifestyle and specific adaptations of the organisms studied. For instance, in the obligate intracellular Apicomplexa we observed massive loss of genes that play a role in general basic processes such as amino acid, carbohydrate, and lipid metabolism, reflecting the transition of a free-living to an obligate intracellular lifestyle. In contrast, many gene families show species-specific expansions, such as those in the plant pathogen oomycete Phytophthora that are involved in degrading the plant cell wall polysaccharides to facilitate the pathogen invasion process. In general, chromalveolates show a tremendous difference in genome structure and evolution and in the number of genes they have lost or gained either through duplication or horizontal gene transfer.     

Scaling of atrioventricular transmission in mammalian species: an evolutionary riddle!

"Scaling deals with the structural and functional consequences of changes in size or scale among otherwise similar organisms." It plays a key role in all studies on comparative mammalian physiology and morphology. Heart weight is proportionally related to body weight and can be described by a straightforward, so-called allometric equation. We studied scaling of AV transmission times (PR intervals on the ECG) in 375 mammals of different dimensions and species. Scaling of AV transmission times versus heart length (third root of weight) is statistically best described by a S-shaped curve. This implies that AV transmission time in mammals is not linearly related to heart length and does not depend solely on the length of the AV transmission system. The AV node fine-tunes AV transmission times at rest and during exercise in individuals; it protects the ventricles against high-rate atrial arrhythmias such as atrial fibrillation; and it regulates basal AV transmission times in mammalian species of varying sizes. We call the "how" and "why" of the scaling of AV transmission time in mammals an evolutionary riddle that deserves further study.