Partial Clonality Expands the Opportunity for Spatial Adaptation.

AbstractReproductive mode may strongly impact adaptation in spatially varying populations linked by dispersal, especially when sexual and clonal offspring differ in dispersal. We determined how spatial structure affects adaptation in populations with mixed clonal and sexual reproduction. In a source-sink quantitative genetic deterministic model (with stabilizing selection around different optima), greater clonal reproduction or parent-offspring association (a measure of the part of the parent's phenotype other than the additive genetic component inherited by clonal offspring) increased the selective difference (difference between phenotypic optima) allowing sink populations to adapt. Given dispersal differences between clonally and sexually produced juveniles, adaptation increased with an increasing fraction of clonal dispersers. When considering migrational meltdown, partially clonal reproduction reduced cases where dispersal caused habitat loss. Stochastic individual-based simulations support these results, although the effect of differential dispersal was reversed, with decreased clonal dispersal allowing greater adaptation. These results parallel earlier findings that for an instantaneous shift in phenotypic optimum, increasing clonality allowed population persistence for a greater shift; here, selective change is spatial rather than temporal. These results may help explain the success of many partially clonal organisms in invading new habitats, complementing traditional explanations based on avoiding Allee effects.

Direct oral anticoagulant agents might be safe for patients undergoing endovenous radiofrequency and laser ablation.

OBJECTIVE: Studies assessing the effect of the use of anticoagulant agents on endovenous thermal ablation (ETA) have been limited to patients taking warfarin. Thus, the aim of the present study was to assess the efficacy and safety of ETA for patients taking direct oral anticoagulants (DOACs). We hypothesized that the outcome of ETA for patients taking DOACs would not be superior to the outcomes for patients taking DOACs. METHODS: We performed a retrospective review to identify patients who had undergone radiofrequency ablation or endovenous laser ablation with 1470-nm diode laser fibers for symptomatic great or small saphenous venous reflux from 2018 to 2020. The patients were dichotomized into those who had received a therapeutic dose of DOACs periprocedurally and those who had not (control group). The outcomes of interest included the rates of treated vein closure at 7 days and 9 months and the incidence of deep vein thrombosis (DVT), endothermal heat-induced thrombosis (EHIT), and bleeding periprocedurally. RESULTS: Of the 301 patients (382 procedures), 69 patients (87 procedures) had received DOACs and 232 control patients (295 procedures) had not received DOACs. The patients receiving DOACs were more often older (mean age, 65 years vs 55 years; P < .001) and male (70% vs 37%; P < .001), with a higher prevalence of venous thromboembolism and more severe CEAP (clinical, etiologic, anatomic, pathophysiologic) classification (5 or 6), than were the control patients. Those receiving DOACs were more likely to have had a history of DVT (44% vs 6%; P < .001), pulmonary embolism (13% vs 0%; P < .001), and phlebitis (32% vs 15%; P < .001). Procedurally, radiofrequency ablation had been used more frequently in the control group (92% vs 84%; P = .029), with longer segments of treated veins (mean, 38 mm vs 35 mm, respectively; P = .028). No major or minor bleeding events nor any EHIT had occurred in either group. Two patients in the control group (0.7%) developed DVT; however, no DVT was observed in those in the DOAC group (P = .441). At 9 months, the treated vein had remained ablated after 94.4% of procedures for patients receiving DOACs and 98.4% of the control group (P = .163). On multivariable analysis, DOAC usage was not associated with an increased risk of vein recanalization (hazard ratio, 5.76; 95% confidence interval, 0.57-58.64; P = .139). An increased preprocedural vein diameter and the use of endovenous laser ablation were associated with an increased risk of recanalization. CONCLUSIONS: In our study of patients who had undergone ETA for symptomatic saphenous venous reflux, the periprocedural use of DOACs did not adversely affect the efficacy of endovenous ablation to ≥9 months. Furthermore, DOAC use did not confer an additional risk of bleeding, DVT, or EHIT periprocedurally. DOACs may be safely continued without affecting the efficacy and durability of ETA.

Superficial venous procedures can be performed safely and effectively in patients with deep venous reflux.

BACKGROUND: The finding of concurrent deep venous reflux (DVR) when interrogating superficial venous reflux is common and might be a marker of more severe chronic venous insufficiency. However, the safety and clinical and patient-reported outcomes for patients undergoing superficial venous treatment in the presence of DVR remains underreported. Moreover, the factors associated with the persistence and disappearance of DVR after superficial vein treatment have not been evaluated. In the present study, we sought to address these questions. METHODS: We performed a review of the institutional vascular quality initiative database from June 2016 to June 2021. Consecutive patient limbs were identified that had undergone a superficial venous intervention and had duplex ultrasound evaluations available. These patients were divided into those with and without DVR. Those with DVR were further reviewed for anatomic details and the persistence or resolution of DVR after the procedure. The primary outcome was the venous clinical severity score (VCSS) at a follow-up >3 months. The secondary outcomes included the incidence of any postoperative deep vein thrombosis or endovenous heat-induced thrombosis, differences in patient-reported outcomes, rate of resolution of DVR, and factors associated with DVR persistence. Both univariate analysis and multivariate logistic regression were applied. RESULTS: Of the patients who had undergone superficial venous treatment, 644 patient limbs had had DVR and 7812 had not, for a prevalence of 7.6%. The DVR group was associated with a higher burden of chronic venous insufficiency. On univariate analysis, patient limbs, both with and without DVR, had improved significantly in the VCSS at <3 months of follow-up and were not significantly different. At >3 months of follow-up, the VCSS had again improved significantly compared with the VCSS at <3 months of follow-up. However, the difference between the two groups was statistically significant at the longer interval. The magnitude of improvement in the VCSS between the two groups at the longer follow-up were similar statistically (VCSS, 3.17 ± 3.11 vs 3.03 ± 2.93; P = .739). The HASTI (heaviness, achiness, swelling, throbbing, itching) score had similarly improved significantly in both groups but remained significantly higher in the DVR group during follow-up. On multivariate logistic regression, DVR was not associated with an increased VCSS at >3 months of follow-up. No intergroup difference was found in the incidence of postoperative deep vein thrombosis or endovenous heat-induced thrombosis. Of limbs with DVR, 40.8% no longer had evidence of detectable DVR at the latest follow-up venous duplex ultrasound, and DVR limited to a single segment was more likely than DVR in multiple segments to be no longer detectable. CONCLUSIONS: Our results have shown that superficial venous procedures are safe and effective in patients with DVR, leading to improvements in clinical and patient-reported outcomes similar to those for patients without DVR. In a large proportion of the treated limbs, especially those with DVR in a single segment, no evidence of DVR was found after superficial venous intervention. Although patients with DVR will have a higher burden of chronic venous insufficiency, they still appear to derive significant benefit from superficial venous treatment.

Periprocedural P2Y12 inhibitors improve perioperative outcomes after carotid stenting by primarily decreasing strokes.

OBJECTIVE: The continuation of antiplatelet agents in the periprocedural period around carotid stenting (CAS) procedures is felt to be mandatory to minimize the risk of periprocedural stroke. However, the optimal antiplatelet regimen is unclear, with some advocating dual antiplatelet therapy, and others supporting the use of P2Y12 inhibitors alone. The objective of this study was to evaluate the periprocedural effect of P2Y12 inhibitors for CAS. METHODS: The Vascular Quality Initiative was used from years 2007 to 2020. All transcarotid artery revascularization (TCAR) and transfemoral carotid artery stenting (TF-CAS) procedures were included. Patients were stratified based on perioperative use of P2Y12 inhibitors as well as symptomatic status. Primary end points were perioperative neurological events (strokes and transient ischemic attacks). Secondary end points were mortality and myocardial infarction. RESULTS: A total of 31,036 CAS procedures were included for analysis, with 49.8% TCAR and 50.2% TF-CAS cases; 63.8% of patients were male and 82.3% of patients were on a P2Y12 inhibitor. P2Y12 inhibitor use was more common in males, asymptomatic patients, those older than 70 years, and concurrent statin use. P2Y12 inhibitors were more likely to be used in TCAR cases than in TF-CAS cases (87.3% vs 76.8%; P < .001). The rate of periprocedural neurological events in the whole cohort was 2.6%. Patients on P2Y12 inhibitors were significantly less likely to experience a periprocedural neurological event (2.3% vs 3.9%; P < .001) and mortality (0.6% vs 2.1%; P < .001) than those who were not on a P2Y12 inhibitor. There was no effect on the rates of myocardial infarction. On multivariate analysis, both symptomatic and asymptomatic patients on P2Y12 inhibitors were significantly less likely to develop perioperative neurological events. Additionally, the use of P2Y12 inhibitors demonstrated an independent significant effect in reducing of the rate of perioperative stroke (odds ratio, 0.29; 95% confidence interval, 0.25-0.33). Finally, additional analysis of the types of P2Y12 inhibitors used revealed that all seemed to be equally effective in decreasing the periprocedural neurological event rate. CONCLUSIONS: The use of perioperative P2Y12 inhibitors seems to markedly decrease the perioperative neurological event rate with TCAR and TF-CAS in both symptomatic and asymptomatic patients and should be strongly considered. Patients with contraindications to P2Y12 inhibitors may not be appropriate candidates for any CAS procedure. Additionally, alternative types of P2Y12 inhibitors seem to be equally effective as clopidogrel. Finally, an analysis of the Vascular Quality Initiative demonstrates that, even for TCAR cases, only 87.3% of patients seem to be on P2Y12 inhibitors in the periprocedural period, leaving room for significant improvement.

Litter, Plant Competition, and Ecosystem Dynamics: A Theoretical Perspective.

AbstractCommunity structure depends jointly on species' responses to, and effects on, environmental factors. Many such factors, including detritus, are studied in ecosystem ecology. Detritus in terrestrial ecosystems is dominated by plant litter (nonliving organic material), which, in addition to its role in material cycling, can act as a niche factor modulating interactions among plants. Litter thus links traditional community and ecosystem processes, which are often studied separately. We explore this connection using population dynamics models of two plant species and a litter pool. We first find conditions determining the outcome of interactions between these species, highlighting the role that litter plays and the role of broader ecosystem parameters, such as decomposition rate. Species trade-offs in tolerance to direct competition and litter-based interference competition allow for coexistence, provided the litter-tolerant species produces more litter at the population level; otherwise, priority effects may result. When species coexist, litter-mediated interactions between plants disrupt the traditional relationship between biomass accumulation and decomposition. Increasing decomposition rate may have no effect on standing litter density and, in some cases, may even increase litter load. These results illustrate how ecosystem variables can influence community outcomes that then feed back to influence the ecosystem.

Mannitol Use is Renal Protective in Patients with Chronic Kidney Disease Requiring Suprarenal Aortic Clamping.

BACKGROUND: Mannitol is often administered during open juxtarenal or suprarenal aortic surgery to prevent ischemic injury to the kidneys. Prior evidence evaluating the benefits of intraoperative mannitol in reducing ischemia/reperfusion injury is conflicting and largely based on small, retrospective series. The aim of this study was to evaluate the effect of mannitol in preventing postoperative hemodialysis in patients undergoing open abdominal aortic aneurysm (AAA) repair where proximal control involved temporary renal ischemia. METHODS: The Society for Vascular Surgery Quality Initiative database was queried for all patients undergoing elective open AAA repair between 2003 and 2020. Patients were included in the current analysis if the proximal aortic clamp was placed above at least one renal artery. Chronic kidney disease (CKD) was defined as Cr > 1.8 mg/dL. Primary end points were 30-day major morbidity (myocardial infarction, respiratory complications, lower extremity or intestinal ischemia, and the need for temporary or permanent hemodialysis) and mortality. Comparisons were made between the mannitol and nonmannitol cohorts and stratified by the presence of preexisting CKD. RESULTS: During the study period, 4,156 patients underwent elective open AAA repair requiring clamp placement more than one (32.7%) or both (67.3%) renal arteries; 182 patients (4.4%) had preexisting CKD. Overall, 69.8% of patients received mannitol during their surgery. Mannitol was more frequently used in cases involving clamp placement above both renal arteries (70.3%) than one renal artery (61.5%). While prolonged ischemia time (more than 40 min) was associated with a higher risk of postoperative dialysis in patients without CKD, it was not significant in patients with baseline CKD. On a univariate analysis, mannitol use in patients with CKD was associated with a lower risk of postoperative dialysis (P = 0.005). This remained significant on a multivariate analysis (P = 0.008). Mannitol use did not appear to confer renal protective effects in patients without baseline CKD. CONCLUSIONS: Mannitol use was associated with a decreased risk of need for postoperative hemodialysis in patients with CKD undergoing suprarenal aortic clamping for open aneurysm repair. In appropriately selected patients, particularly those with underlying renal insufficiency, mannitol may confer a renal protective effect in open repair of pararenal AAA requiring suprarenal clamping.

The factors that favor adaptive habitat construction versus non-adaptive environmental conditioning.

Adaptive habitat construction is a process by which individuals alter their environment so as to increase their (inclusive) fitness. Such alterations are a subset of the myriad ways that individuals condition their environment. We present an individual-based model of habitat construction to explore what factors might favor selection when the benefits of environmental alterations are shared by individuals of the same species. Our results confirm the predictions of inclusive fitness and group selection theory and expectations based on previous models that construction will be more favored when its benefits are more likely to be directed to self or near kin. We found that temporal variation had no effect on the evolution of construction. For spatial heterogeneity, construction was disfavored when the spatial pattern of movement did not match the spatial pattern of environmental heterogeneity, especially when there was spatial heterogeneity in the optimal amount of construction. Under those conditions, very strong selection was necessary to favor genetic differentiation of construction propensity among demes. We put forth a constitutive theory for the evolution of adaptive habitat construction that unifies our model with previous verbal and quantitative models into a formal conceptual framework.

Temporal variation may have diverse impacts on range limits.

Environmental fluctuations are pervasive in nature, but the influence of non-directional temporal variation on range limits has received scant attention. We synthesize insights from the literature and use simple models to make conceptual points about the potentially wide range of ecological and evolutionary effects of temporal variation on range limits. Because organisms respond nonlinearly to environmental conditions, temporal variation can directionally alter long-term growth rates, either to shrink or to expand ranges. We illustrate this diversity of outcomes with a model of competition along a mortality gradient. Temporal variation can permit transitions between alternative states, potentially facilitating range expansion. We show this for variation in dispersal, using simple source-sink population models (with strong Allee effects, or with gene flow hampering local adaptation). Temporal variation enhances extinction risk owing to demographic stochasticity, rare events, and loss of genetic variation, all tending to shrink ranges. However, specific adaptations to exploit variation (including dispersal) may permit larger ranges than in similar but constant environments. Grappling with temporal variation is essential both to understand eco-evolutionary dynamics at range limits and to guide conservation and management strategies. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.

A single-center experience of anterior accessory saphenous vein endothermal ablation demonstrates safety and efficacy.

OBJECTIVE: Endothermal ablation is well-established for the treatment of the great and small saphenous veins. Data are lacking for treatment of the anterior accessory saphenous vein (AASV). The purpose of this study was to evaluate the safety and efficacy of AASV treatment using endothermal ablation. METHODS: This retrospective review included 314 limbs at a single academic institution from 2016 to 2018 using the institutional Vascular Quality Initiative database. All limbs had documented AASV reflux. Baseline characteristics were evaluated including age; sex; ethnicity; clinical, etiology, anatomy, pathophysiology classification; Venous Clinical Severity Score (VCSS); and vein diameter. Outcomes relating to procedure safety and efficacy included treatment modality and length, successful ablation on postoperative imaging, postprocedural clinical outcomes, incidence of endothermal heat-induced thrombosis (EHIT), and any postprocedural complication. RESULTS: A total of 314 consecutive limbs were identified from 2016 to 2018. The preprocedure VCSS scores were available for 312 limbs and averaged 6.13 ± 3.33. A history of varicose veins were reported in all limbs with 49.4% (n = 155) having previously undergone a procedure. The most common presenting symptom was mild edema in 52.5% (n = 165). Vein diameter and assessment of reflux were obtained by venous duplex ultrasound (DUS) examination. The largest AASV diameter was available for 304 limbs, averaging 7.93 ± 2.69 mm. Treatment modalities included radiofrequency ablation (RFA) in 59.2% (n = 186), endovenous laser ablation (EVLA) in 37.9% (n = 119), and isolated microphlebectomy in 2.9% (n = 9). In all, 38.5% (n = 121) of limbs underwent concomitant microphlebectomy at the time of EVLA. The total treatment length was obtained in 297 limbs, averaging 23.0 cm ± 12.0. Postoperatively, 94.6% of limbs (n = 297) were prescribed compression stockings. Postoperative DUS examination was performed in 312 limbs, revealing successful ablation in 96.5% (n = 303) with 2 limbs (0.6%) developing an EHIT, both treated with therapeutic enoxaparin for 1 week. Repeat DUS examination revealed thrombus resolution in one limb; the other patient was lost to follow-up. VCSS scores after the procedure were available for 145 limbs and averaged 4.45 ± 2.31. This was a statistically significant decrease from preprocedure VCSS scores (P < .01). Average duration of follow-up was 2.2 years, with two limbs lost to follow-up. Of the nine limbs (3.5%) whose initial procedure failed, five (56%) were treated using RFA and four (44%) were treated using EVLA. There were no other postoperative complications. CONCLUSIONS: Our experience over a 3-year period for treating the AASV shows it to be safe and effective in a broad range of disease severity with an improvement in VCSS and a low incidence of EHIT. Additionally, RFA and EVLA exhibit similar treatment efficacy. Long-term follow-up data are needed.

The Effect of Predator Population Dynamics on Batesian Mimicry Complexes.

AbstractUnderstanding Batesian mimicry is a classic problem in evolutionary biology. In Batesian mimicry, a defended species (the model) is mimicked by an undefended species (the mimic). Prior theories have emphasized the role of predator behavior and learning as well as evolution in model-mimic complexes but have not examined the role of population dynamics in potentially governing the relative abundances and even persistence of model-mimic systems. Here, we examined the effect of the population dynamics of predators and alternative prey on the prevalence of warning-signaling prey composed of models and mimics. Using optimal foraging theory and signal detection theory, we found that the inclusion of predator and alternative prey population dynamics could reverse traditional theoretical predictions: as alternative prey increase in numbers, mimics suffer because larger populations of predators are maintained, resulting in apparent competition. Under some circumstances, apparent competition affects model populations as well, although not as severely as it affects mimics. Our results bear on the intriguing puzzle that in nature warning signals are relatively scarce, yet experiments suggest that such signals can be highly advantageous. The availability of alternative prey and numerical responses by predators can overwhelm advantages observed in experiments to keep warning signals in model-mimic systems relatively scarce.

Histologic assessment of lower extremity deep vein thrombus from patients undergoing percutaneous mechanical thrombectomy.

BACKGROUND: Histologic analyses of deep vein thrombi (DVTs) have used autopsy samples and animal models. To the best of our knowledge, no previous study has reported on thrombus composition after percutaneous mechanical extraction. Because elements of chronicity and organization render thrombus resistant to anticoagulation and thrombolysis, a better understanding of clot evolution could inform therapy. METHODS: We performed a histologic evaluation of DVTs from consecutive patients who had undergone mechanical thrombectomy for extensive iliofemoral DVTs using the Clottriever/Flowtriever device (Inari Medical, Irvine, Calif). The DVTs were scored using a semiquantitative method according to the degree of fibrosis (collagen deposition on trichrome staining) and organization (endothelial growth with capillaries and fibroblastic penetration). RESULTS: Twenty-three specimens were available for analysis, with 20 presenting as acute DVT (≤14 days from symptom onset). Of the 23 patients, 11 (48%) had had >5% fibrosis (ie, collagen deposition) and 14 (61%) had had >5% organization (ie, endothelial growth, capillaries, fibroblasts). Four patients with acute DVT had had ≥25% organized thrombus and two had had ≥25% collagen deposition. Of the 20 patients with acute DVT, 40% had had >5% fibrosis and 55% had had >5% organization. The acuity of DVT did not correlate with the amount of fibrosis or organizing scores. CONCLUSIONS: A large proportion of patients with acute DVT will have histologic elements of chronicity and fibrosis. A better understanding of the relationship between such elements and the response to anticoagulant agents and fibrinolytic drugs could inform our approach to therapy.

Anticoagulation Therapy is Associated with Increased Access-related Wound Infections after Hemodialysis Access Creation.

BACKGROUND: The effect of anticoagulation therapy (AC) on hemodialysis access patency and related complications is not well defined. Patients on long-term or chronic AC due to their underlying comorbid conditions may be particularly susceptible to access-related bleeding and complications from repetitive cannulation. Our goal is to assess the effect of anticoagulation therapy on outcomes after access creation. METHODS: The Vascular Quality Initiative (VQI) database was queried for patients undergoing arteriovenous fistula (AVF) or graft (AVG) placement, from 2011 to 2019. Only patients with data on post-procedural AC status were included. Anticoagulation use was defined as patients on warfarin, dabigatran, or rivaroxaban after access creation at postoperative follow up. Demographic and procedural details were analyzed. Wound infection and patency rates at six months were assessed. Binomial logistic regression analysis was performed to assess the association of anticoagulation use with these outcomes. RESULTS: A total of 27,757 patients underwent access creation, with the majority undergoing AVF creation (78.8%). The average age was 61.4 years and 55.3% were male. 12.9% of patients were on postoperative AC. The wound infection rate was 2.3- 3.8% in the no AC and AC cohorts, respectively (P < 0.001). At six months follow-up, patency was 85.7- 84.3% in the no AC and AC cohorts, respectively (P = 0.044). Expectedly, grafts had lower patency rates compared to AVF; those within the no AC cohort had a patency of 83.0% compared to 81.2 % in those on AC (P = 0.106). On multivariable analysis, anticoagulation use was associated with a higher risk of wound infections (odds ratio [OR] 1.513, 95% confidence interval [CI] 1.160-1.973, P = 0.002). AC use did not significantly affect access patency. CONCLUSION: Anticoagulation therapy was associated with a higher rate of wound infections but did not affect short-term access patency within six-months. These patients warrant close surveillance of their access for signs of infection. Furthermore, long-term implications of anticoagulation needs further evaluation.

Risk Factors for and Intraoperative Management of Intolerance to Flow Reversal in TCAR.

BACKGROUND: In patients deemed high risk for carotid endarterectomy (CEA) who are indicated for treatment of carotid artery stenosis (CAS), transcarotid artery revascularization (TCAR) has been demonstrated as a safe and effective alternative to trans-femoral carotid artery stenting (TF-CAS). Compared to CEA, where approx. 12% of patients undergoing awake intervention do not tolerate internal carotid artery (ICA) clamping, only 1-2% of patients were observed to have intolerance to flow reversal during TCAR based on data from the ROADSTER1/2 trials. This study reviewed awake interventions from those trials to assess factors associated with intolerance to flow reversal and review how those cases were managed. METHODS: This is a retrospective review of prospectively collected data from Reverse Flow Used During Carotid Artery Stenting Procedure (ROADSTER) multicenter trial along with the subsequent post-approval (ROADSTER-2) trial. The subset of patients from both trials undergoing awake TCAR was analyzed to compare demographics, procedural details, and anatomic factors between patients who did and did not experience intolerance to reversal of flow to assess for predisposing factors. Patients were deemed intolerant to flow reversal at the discretion of the operator, often related to changes in completion of neurologic tasks, hemodynamic stability, or patient reported symptoms. RESULTS: A total of 103 patients from ROADSTER and 194 patients from ROADSTER-2 underwent TCAR under local/regional anesthesia. Of these, 8 patients had intolerance to flow reversal, though all cases were successfully completed. While intraoperative hemodynamic data was only available for 5 of the 8 intolerant patients, none experienced hypotension. 4 cases were completed under low flow reversal, 3 cases were successfully weaned from low to high flow over several minutes, and 1 case required general anesthesia. No significant association was found between intolerance to flow reversal and comorbidities including diabetes mellitus (DM), hypertension (HTN), hyperlipidemia (HLD), congestive heart failure (CHF), prior MI or angina, pre-op CAS-related symptoms, prior stroke, prior CAS or CEA, prior neck radiation, tandem stenosis, high cervical stenosis, or hostile neck. A trend towards significance was seen with chronic obstructive pulmonary disease (COPD) and contralateral carotid artery occlusion (P = 0.086 and 0.139, respectively). CONCLUSIONS: Despite intolerance to flow reversal, TCAR cases were successfully completed by adjusting reversal-of-flow rate and do not typically require conversion to GETA. While factors contributing to intolerance of flow reversal during TCAR remain poorly understood, this study identified a trend towards significance with an association of preexisting COPD and contralateral carotid artery occlusion. Given the low number of patients who experienced this issue, a larger sample size is required to better elucidate these trends.

Do I build or do I move? Adaptation by habitat construction versus habitat choice.

Trait adaptation to a heterogeneous environment can occur through six modes: genetic differentiation of those traits, a jack-of-all-trades phenotypic uniformity, diversified bet-hedging, phenotypic plasticity, habitat choice, and habitat construction. A key question is what circumstances favor one mode over another, and how they might interact if a system can express more than one mode at a time. We examined the joint evolution of habitat choice and habitat construction using individual-based simulations. We manipulated when during the life cycle construction occurred and the fitness value of construction. We found that for our model habitat construction was nearly always favored over habitat choice, especially if construction happened after dispersal. Because of the ways that the various modes of adaptation interact with each other, there is no simple answer as to which will be favored; it depends on details of the biology and ecology of a given system.

Disturbance-induced emigration: an overlooked mechanism that reduces metapopulation extinction risk.

Emigration propensity (i.e., the tendency to leave undisturbed patches) is a key life-history trait of organisms in metapopulations with local extinctions and colonizations. Metapopulation models of dispersal evolution typically assume that patch disturbance kills all individuals within the patch, thus causing local extinction. However, individuals may instead be able to leave a patch when it is disturbed, either by fleeing before being killed or simply because the disturbance destroys the patch without causing mortality. This scenario may pertain to a wide range of organisms from horizontally transmitted symbionts, to aquatic insects inhabiting temporary ponds, to vertebrates living in fragmented forests. We generalized a Levins-type metapopulation model of dispersal evolution by adding a new parameter of disturbance escape probability, which incorporates a second source of dispersal into the model: disturbance-induced emigration. We show that disturbance escape expands the domain of metapopulation viability and selects for lower rates of emigration propensity when disturbance rates are high. The fitness gains from disturbance-induced emigration are generally moderate, suggesting that disturbance escape might act more as a complementary dispersal strategy rather than a replacement to emigration propensity, at least for metapopulations that meet the assumptions of the Levins-type model. Yet disturbance-induced emigration may in some circumstances rescue a metapopulation from long-term extinction when the combination of high disturbance rates and low local population growth rates compromises its viability. Further, a metapopulation could persist exclusively by disturbance escape if local carrying capacities are large enough to counterbalance two sources of mortality: mortality driven by disturbance and mortality during dispersal. This study opens two promising research lines: (1) the investigation of disturbance escape in metapopulations of ephemeral habitats with unsaturated populations and non-equilibrium dynamics and (2) the incorporation of information costs to investigate the joint evolution of disturbance escape and emigration propensity.

Why aren't warning signals everywhere? On the prevalence of aposematism and mimicry in communities.

Warning signals are a striking example of natural selection present in almost every ecological community - from Nordic meadows to tropical rainforests, defended prey species and their mimics ward off potential predators before they attack. Yet despite the wide distribution of warning signals, they are relatively scarce as a proportion of the total prey available, and more so in some biomes than others. Classically, warning signals are thought to be governed by positive density-dependent selection, i.e. they succeed better when they are more common. Therefore, after surmounting this initial barrier to their evolution, it is puzzling that they remain uncommon on the scale of the community. Here, we explore factors likely to determine the prevalence of warning signals in prey assemblages. These factors include the nature of prey defences and any constraints upon them, the behavioural interactions of predators with different prey defences, the numerical responses of predators governed by movement and reproduction, the diversity and abundance of undefended alternative prey and Batesian mimics in the community, and variability in other ecological circumstances. We also discuss the macroevolution of warning signals. Our review finds that we have a basic understanding of how many species in some taxonomic groups have warning signals, but very little information on the interrelationships among population abundances across prey communities, the diversity of signal phenotypes, and prey defences. We also have detailed knowledge of how a few generalist predator species forage in artificial laboratory environments, but we know much less about how predators forage in complex natural communities with variable prey defences. We describe how empirical work to address each of these knowledge gaps can test specific hypotheses for why warning signals exhibit their particular patterns of distribution. This will help us to understand how behavioural interactions shape ecological communities.

Endovascular treatment of popliteal artery aneurysms has comparable long-term outcomes to open repair with shorter lengths of stay.

OBJECTIVE: During the past two decades, the treatment of popliteal artery aneurysms (PAAs) has undergone a transformation. Although open surgical repair (OR) has remained the reference standard for treatment, endovascular repair (ER) has become an attractive alternative for select patient populations. The objective of the present study was to compare the outcomes of OR vs ER of PAAs at a single institution. METHODS: We performed a retrospective review of the medical records for all patients who had undergone repair for PAAs from 1998 to 2017. The baseline patient, anatomic, and operative characteristics and outcomes were compared between the OR and ER cohorts. Intervention and treatment were at the discretion of the surgeon. RESULTS: From 1998 to 2017, 64 patients had undergone repair of 73 PAAs at our tertiary care center. Of the 69 patients (73 PAAs), 29 (33 PAAs) had undergone OR and 35 (40 PAAs) had undergone ER. When comparing the two cohorts, no statistically significant differences were found in the demographic characteristics such as age, gender, or number of runoff vessels. Significantly more patients in the ER group (n = 21; 53%) than in the OR group (n = 7; 21%) had had hyperlipidemia (P = .008) and a previous carotid intervention (6% vs 0%; P = .029). Overall, the presence of symptoms was similar between the two groups. However, the OR group had a significantly higher number of patients who had presented with acute ischemia (P = .01). The length of stay was significantly shorter for the ER cohort (mean, 1.8 days; range, 1-11 days) than for the OR group (mean, 5.4 days; range, 2-13 days; P < .0001). No significant difference was found in the primary or secondary patency rates between the two groups. In the ER group, good runoff (two or more vessels) was a positive predictor for primary patency at 1 year (odds ratio, 3.36; 95% confidence interval, 1.0-11.25). However, it was not in the OR group. Postoperative single and/or dual antiplatelet therapy did not affect primary patency in either cohort. CONCLUSIONS: The results of our study have demonstrated that ER of PAAs is a safe and durable option with patency rates comparable to those with OR and a decreased length of stay, with good runoff a positive predictor for primary patency in the ER cohort.

Adjunctive false lumen intervention for chronic aortic dissections is safe but offers unclear benefit.

OBJECTIVE: Adjunctive false lumen embolization (FLE) with thoracic endovascular aortic repair (TEVAR) in patients with chronic aortic dissection is thought to induce FL thrombosis and favorable aortic remodeling. However, these data are derived from small single-institution experiences and the potential benefit of FLE remains unproven. In this study, we examined perioperative and midterm outcomes of patients with aortic dissection undergoing concomitant TEVAR and FLE.* METHODS: : Patients 18 or older who underwent TEVAR for chronic aortic dissection with known FLE status in the Society for Vascular Surgery Vascular Quality Initiative database between January 2010 and February 2020 were included. Ruptured patients and emergent procedures were excluded. Patient characteristics, operative details and outcomes were analyzed by group: TEVAR with or without FLE. Primary outcomes were in-hospital post-operative complications and all-cause mortality. Secondary outcomes included follow-up mean maximum aortic diameter change, rates of false lumen thrombosis, re-intervention rates, and mortality. RESULTS: 884 patients were included: 46 had TEVAR/FLE and 838 had TEVAR alone. There was no significant difference between groups in terms of age, gender, comorbidities, prior aortic interventions, mean maximum pre-operative aortic diameter (5.1cm vs. 5.0cm, P=0.43), presentation symptomatology, or intervention indication. FLE was associated with significantly longer procedural times (178min vs. 146min, P=0.0002), increased contrast use (134mL vs. 113mL, P=0.02), and prolonged fluoroscopy time (34min vs. 21min, P<0.0001). However, FLE was not associated with a significant difference in post-operative complications (17.4% vs. 13.8%, P=0.51), length of stay (6.5 vs. 5.7 days, P=0.18), or in-hospital all-cause mortality (0% vs. 1.3%, P=1). In mid-term follow-up (median 15.5months, IQR 2.2-36.2 months), all-cause mortality trended lower, but was not significant (2.2% vs. 7.8%); and Kaplan-Meier analysis demonstrated no difference in overall survival between groups (P=0.23). By Cox regression analysis, post-operative complications had the strongest independent association with all-cause mortality (HR 2.65, 95% CI 1.56-4.5, P<0.001). In patients with available follow-up imaging and re-intervention status, mean aortic diameter change (n=337, -0.71cm vs. -0.69cm, P=0.64) and re-intervention rates (n=487, 10% vs. 11.4%, P=1) were similar. CONCLUSIONS: Adjunctive FLE, despite increased procedural times, can be performed safely for patients with chronic dissection without significantly higher overall perioperative morbidity or mortality. TEVAR/FLE demonstrates trends for improved survival and increased rates of FL thrombosis in the treated thoracic segment; however, given the lack of evidence to suggest a significant reduction in re-intervention rates or induction of more favorable aortic remodeling compared to TEVAR alone, the overall utility of this technique in practice remains unclear. Further investigation is needed to determine the most appropriate role for FLE in managing chronic aortic dissections.

The evolution of habitat construction with and without phenotypic plasticity.

Habitat construction and phenotypic plasticity are alternative responses to variable environments. We explored evolution along an environmental gradient of habitat construction alone and in combination with phenotypic plasticity using individual-based simulations that manipulated the fitness benefit of construction and whether construction maintained or eliminated that gradient. Construction was favored when its benefits were more likely to flow to the immediate offspring of the constructing individuals. Habitat construction and phenotypic plasticity traded off against each other or plasticity was selected against, depending on how the optimum environment varied and with the fitness value of construction. When selection favored differences in the amount of construction along the environmental gradient, genetic differentiation for habitat construction increased as the fitness value of construction increased. The degree to which each adaptive response was likely to evolve also depended on the precise ordering of life history events. Adaptive habitat construction does not always occur and may be selected against.

Environmental fluctuations dampen the effects of clonal reproduction on evolutionary rescue.

Evolutionary rescue occurs when genetic change allows a population to persist in response to an environmental change that would otherwise have led to extinction. Most studies of evolutionary rescue assume that species have either fully clonal or fully sexual reproduction; however, many species have partially clonal reproductive strategies in which they reproduce both clonally and sexually. Furthermore, the few evolutionary rescue studies that have evaluated partially clonal reproduction did not consider fluctuations in the environment, which are nearly ubiquitous in nature. Here, we use individual-based simulations to investigate how environmental fluctuations (either uncorrelated or positively autocorrelated) influence the effect of clonality on evolutionary rescue. We show that, for moderate magnitudes of environmental fluctuations, as was found in the absence of fluctuations, increasing the degree of clonality increases the probability of population persistence in response to an abrupt environmental change, but decreases persistence in response to a continuous, directional environmental change. However, with large magnitudes of fluctuations, both the benefits of clonality following a step change and the detrimental effects of clonality following a continuous, directional change are generally reduced; in fact, in the latter scenario, increasing clonality can even become beneficial if environmental fluctuations are autocorrelated. We also show that increased generational overlap dampens the effects of environmental fluctuations. Overall, we demonstrate that understanding the evolutionary rescue of partially clonal organisms requires not only knowledge of the species life history and the type of environmental change, but also an understanding of the magnitude and autocorrelation of environmental fluctuations.