Density-dependent within-patch movement behavior of two competing species.

Movement behavior is central to understanding species distributions, population dynamics and coexistence with other species. Although the relationship between conspecific density and emigration has been well studied, little attention has been paid to how interspecific competitor density affects another species' movement behavior. We conducted releases of two species of competing Tribolium flour beetles at different densities, alone and together in homogeneous microcosms, and tested whether their recaptures-with-distance were well described by a random-diffusion model. We also determined whether mean displacement distances varied with the release density of conspecific and heterospecific beetles. A diffusion model provided a good fit to the redistribution of T. castaneum and T. confusum at all release densities, explaining an average of >60% of the variation in recaptures. For both species, mean displacement (directly proportional to the diffusion rate) exhibited a humped-shaped relationship with conspecific density. Finally, we found that both species of beetle impacted the within-patch movement rates of the other species, but the effect depended on density. For T. castaneum in the highest density treatment, the addition of equal numbers of T. castaneum or T. confusum had the same effect, with mean displacements reduced by approximately one half. The same result occurred for T. confusum released at an intermediate density. In both cases, it was total beetle abundance, not species identity that mattered to mean displacement. We suggest that displacement or diffusion rates that exhibit a nonlinear relationship with density or depend on the presence or abundance of interacting species should be considered when attempting to predict the spatial spread of populations or scaling up to heterogeneous landscapes.

Anomalous phenology of Ixodes scapularis (Ixodida: Ixodidae) in Mississippi.

The blacklegged tick, Ixodes scapularis Say, is one of the most important vectors of tick-borne disease agents in North America. Accordingly, it is crucial to know this species local composition, abundance, and seasonality (phenology) to help prevent tick-borne illnesses. The phenology of adult I. scapularis is reported in the scientific literature from October through May. Data from previous research in Mississippi have all supported this time frame for adult blacklegged tick activity. However, in this study, we report a collection of 13 I. scapularis from 9 widely separated areas in Mississippi during the summer and early fall of 2022 (June, July, and September). These findings are remarkable, even enigmatic, and should prompt further investigation.

Envenomation From Flood-Related Fire Ant Rafting: A Cautionary Note.

BACKGROUND: Imported fire ants aggressively sting humans, leading to a variety of local and systemic effects. Fire ants display a behavioral adaptation to survive flooding, called "rafting," bringing humans into even more contact with fire ants. METHODS: To assess frequency of encounters with fire ant rafts, duck hunters on the website "Duck Hunter's Forum" were asked about their experiences with the ants while wading or boating in flooded areas. All members of the group received a brief explanation and asked to respond directly if they had had such an encounter. They were then asked to fill out a short 6-question survey. RESULTS: There were 2021 views of the thread about fire ant raft encounters, with 35 (1.7%) responses. Twenty-four (68.6%) said they had experienced encounters with fire ant rafts. Six responders described purposely or inadvertently physically touching the rafts with their body parts, boat, or a paddle, causing the ants to enter their boat or to climb directly onto the hunter(s). Five respondents were stung (number of stings from "a few" to 50), describing reactions to stings as "small pustules," "whelps," and "pimple-like, puss-filled whelps." CONCLUSIONS: These results confirm that fire ant rafts formed during flooding present a potential hazard to persons walking, wading, or boating in those areas. We suggest that these rafts are an under-appreciated health hazard. It is reasonable to assume that people in flooded areas occasionally contact these floating rafts and are stung multiple times. We provide preliminary prevention/protection recommendations for health professionals, to be shared with their patients and the general public.

Ecological release and patch geometry can cause nonlinear density-area relationships.

A primary driver of species extinctions and declining biodiversity is loss and fragmentation of habitats owing to human activities. Many studies spanning a wide diversity of taxa have described the relationship between population density and habitat patch area, i.e., the density-area relationship (DAR), as positive, neutral, negative or some combination of the three. However, the mechanisms responsible for these relationships remain elusive. We employ a theoretical spatially explicit population model built upon the reaction-diffusion framework with absorbing boundary conditions to model a habitat specialist dwelling in islands of habitat surrounded by a hostile matrix. We consider patches with a convex or non-convex geometry. Our results show that a single species following logistic-type population growth exhibits a strictly positive and continuous DAR. However, when multiple asymptotically stable steady states are preset in the system, a discontinuous DAR arises. In the case of two species governed by diffusive Lotka-Volterra growth and competitive interactions, we observe that overall DAR structure can be either (1) positive, (2) positive for small areas and neutral for large, or (3) hump-shaped, i.e., positive for area below a threshold and negative for area above. Patch complexity such as non-convex geometry can cause discontinuities in DAR slope for a single species and create qualitatively different patterns in a competitive system as compared to a convex patch. We also compared our theoretical results with two empirical studies (Anolis lizards on islands and crossbills and pine squirrels in forest fragments) where the pragmatic view of DAR fails to give a mechanistic understanding of what was observed. Close qualitative agreement between theoretical and observed DAR indicates that our model gives a reasonable explanation of the mechanisms underpinning DAR found in those studies. From a conservation perspective, the DAR is crucial to the identification of valuable habitat fragments that favor high abundance and the design of a reserve for a target species. When it comes to protecting a single species, these results suggest that there is unlikely to be a simple solution and that conservation decisions should always be made on a case-by-case basis.

The Evolution of a Tick Bite Lesion.

Hard ticks (Acari: Ixodidae) use their mouthparts to cut through the epidermis and insert a barbed hypostome, leading to deep inflammation of local tissues. Herein, we describe cutaneous lesion development resulting from a tick bite at seven time points over a 30-day period. This case highlights the fact that ticks may produce lasting cutaneous lesions, which may persist for at least 30 days, even without any obvious pathology or complications.

Salt as a Trigger for Atrial Tachycardia/Fibrillation.

A variety of potential triggers of atrial fibrillation (AF) have been reported, including alcohol consumption, caffeine, exercise, and stress. Vagal AF triggers include gastrointestinal factors such as the amount of food consumed, types of foods, and gas and bloating. In this case report, detailed data of seven dietary and behavioral factors (many vagal) believed to be possible atrial tachycardia (AT) or AF triggers in a single patient with paroxysmal AT/AF were recorded. Episodes of AT and AF were recorded in the patient using a Medtronic loop recorder and analyzed by a cardiac electrophysiologist. To evaluate these potential triggers of AT/AF events, a general linear model with binomial family error distribution was used to fit the data. Then, a stepAIC function from the MASS package in R was used to perform a stepwise model selection using AIC (Akaike information criterion). The analysis only identified the amount of salt intake and the use of polyethylene glycol 3350 as predictors of AT/AF, and high salt intake was the only factor significantly associated with the onset of AT/AF (P < 0.05). Thus, salt intake may trigger AT/AF in ways other than via hypertension.

Survey and Phylogenetic Analysis of Leucocytozoon (Apicomplexa: Haemosporida) Parasites in Mississippi Black Flies (Diptera: Simuliidae).

For several years, there have been continuous reports of black flies in Mississippi with evidence of transmission of Leucocytozoon spp. This study was conducted to determine the presence and diversity of Leucocytozoon spp. in black flies captured throughout Mississippi. Thirty-three collections, consisting of 346 specimens, were made during the 2-yr period (2015-2016) at 10 locations around the state. In addition to these systematic biweekly collections, 46 specimens were taken in 10 collections at four additional sites from 2009 to 2014, as well as 388 specimens taken in 14 collections during a severe black fly outbreak during March and April of 2018. Out of 186 pooled samples, 21 samples were positive for haemosporidian DNA. Eighteen of those samples were identified as Leucocytozoon spp. A phylogenetic tree was constructed using the novel sequences along with existing sequences from the MalAvi database. Results showed several of the sequences constructed in this study had high divergence from the existing sequences from the database.

Modeling effects of matrix heterogeneity on population persistence at the patch-level.

Habitat loss and fragmentation is the largest contributing factor to species extinction and declining biodiversity. Landscapes are becoming highly spatially heterogeneous with varying degrees of human modification. Much theoretical study of habitat fragmentation has historically focused on a simple theoretical landscape with patches of habitat surrounded by a spatially homogeneous hostile matrix. However, terrestrial habitat patches are often surrounded by complex mosaics of many different land cover types, which are rarely ecologically neutral or completely inhospitable environments. We employ an extension of a reaction diffusion model to explore effects of heterogeneity in the matrix immediately surrounding a patch in a one-dimensional theoretical landscape. Exact dynamics of a population exhibiting logistic growth, an unbiased random walk in the patch and matrix, habitat preference at the patch/matrix interface, and two functionally different matrix types for the one-dimensional landscape is obtained. These results show existence of a minimum patch size (MPS), below which population persistence is not possible. This MPS can be estimated via empirically derived estimates of patch intrinsic growth rate and diffusion rate, habitat preference, and matrix death and diffusion rates. We conclude that local matrix heterogeneity can greatly change model predictions, and argue that conservation strategies should not only consider patch size, configuration, and quality, but also quality and spatial structure of the surrounding matrix.

Survey of Mississippi Mosquito Blood Meals for Vertebrate Host Identification.

Exploring particular mosquito and vertebrate relationships provide insight to potential transmission of several agents of disease. In the current study, the relationship between white-tailed deer (Odocoileus virginianus) and mosquitoes was explored by identifying blood meals within mosquitoes captured throughout Mississippi between June and September of 2013 and 2017. We captured 72 bloodfed mosquitoes between 2 collection years, with a majority of specimens identified as Culex erraticus or Psorophora mathesoni. Seventy-nine percent (26/33) of blood meals in Cx. erraticus originated from the white-tailed deer. These findings implicate mosquitoes may primarily be feeding on white-tailed deer in rural areas of Mississippi.

Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains.

The tick-borne pathogen Rickettsia parkeri causes a mild rickettsiosis, with cases reported from several countries to its known distribution in the Americas. Molecular analyses have identified a clear distinction between strains of R. parkeri sensu stricto (s. s.) and R. parkeri sensu lato (s. l.) as well as separation between North American and South American R. parkeri s. s. strains. To expand on this previous work, we developed a multilocus sequence typing analysis with two aims: first, to investigate the genetic diversity within strains of North American R. parkeri s. s., and second, to further the understanding of the genetic relationships between R. parkeri s. s. and R. parkeri s. l. Sixty-four R. parkeri isolates and 12 R. parkeri-positive tick lysates were analyzed using a novel typing scheme consisting of four coding regions and two intergenic regions. A concatenated Bayesian phylogeny that identified eight clades was constructed: three represent the R. parkeri s. l. strains, and five represent the R. parkeri s. s. strains. The clades appear to be generally phylogeographically organized and associated with specific tick vectors. However, while one of the four R. parkeri s. s. North American clades appears to be limited to the southwestern United States, the other North American clades exhibit broad dispersal, most notably seen in the largest group, which includes representative samples extending from northern Mexico to Delaware. This work highlights the increasingly recognized geographic range of R. parkeri in the Americas and suggests a potential public health risk for these areas. IMPORTANCE Since 1937, when Rickettsia parkeri was originally identified in Amblyomma maculatum group ticks, the recognized range and associated vectors for this pathogen have expanded significantly. In recent years, R. parkeri has been identified in 12 tick species from seven countries in the Americas. Herein, we provide evidence that the greatest genetic diversity within R. parkeri exists in North America, where one R. parkeri sensu lato and four R. parkeri sensu stricto genotypes are present. While one distinct R. parkeri sensu stricto genotype exists only in the southwestern United States, three genotypes are broadly distributed in the eastern United States, with the largest of these found across the known range of R. parkeri in North America. In contrast, the South American R. parkeri sensu stricto samples represent a single genotype and are completely clonal at the loci analyzed, irrespective of their country of origin.

Seasonality of Aedes albopictus in North and Central Mississippi.

Container-breeding mosquitoes are increasingly important in public health due to recent outbreaks of Zika virus, chikungunya, and dengue. This paper documents seasonality of the most prevalent container-breeding mosquito species in Mississippi-Aedes albopictus. Ten sites in 5 counties in both northern and central Mississippi (20 sites, 10 counties total) were sampled by larval dipping and oviposition traps biweekly from September 2016 to June 2019, totaling 22 months and potentially yielding 440 egg or larval collections. However, 22 collections were missed due to inclement weather and personnel issues during the study period, so actually only 418 site visits were performed. Sites were chosen to maximize chances of finding Ae. albopictus. Of the total 1,310 mosquito larvae collected during the study period, 717 larvae and 50 positive egg papers belonged to Ae. albopictus. Aedes albopictus was found in all 10 northern and central counties. No eggs were collected at any of the sites from December through February, although larvae were occasionally collected during that time frame. This study demonstrates that Ae. albopictus is active in central and northern Mississippi beginning in March each year and continuing through November or December. There is little activity during the coldest months of the year (January and February). These data represent the first extensive analysis of Ae. albopictus seasonality in Mississippi, and as such, allow for better public health awareness of diseases transmitted by this species and design of more effective vector control programs.

Relative Roles of Blow Flies (Diptera: Calliphoridae) and Invasive Fire Ants (Hymenoptera: Formicidae: Solenopsis spp.) in Carrion Decomposition.

Fire ants (Solenopsis spp.) have increasingly been reported from carrion in the southeastern United States and are now a part of the normal succession community. There have been previous observations of these ants altering carrion and preying on other carrion-attendant fauna; however, the overall effects of these activities on carrion decomposition rates, community composition, and blow fly larval development are poorly understood. Alteration of these ecological processes by fire ants could affect the forensic interpretation of entomological data. We conducted a study in Mississippi and Florida whereby portions of the succession fauna were excluded from access to pig carrion to study the relative effects of fire ants and blow flies on carrion decomposition and succession: a control with all fauna having access, a second treatment where fire ants and other geophilic taxa were excluded, and a third treatment in which blow flies and other large organisms were excluded. Fire ants inflicted lesions in the carrion, buried portions that touched the ground, and preyed on some members of the succession fauna. Their exclusion did not affect carrion decomposition rates that were measured but slightly affected the overall carrion community, and strongly affected the oviposition and development of blow flies. Despite the presence of fire ants early in the control, blow flies were eventually able to overcome predation of eggs and larvae, continue colonization, and complete development; however, the delay in the colonization of blow flies on carrion could affect the determination of postmortem intervals when development rates of blow flies are considered in the calculation.

How does comorbidity affect colon cancer patients' care trajectory? Results from the French EvaCCoR cohort study.

OBJECTIVE: Due to their advanced age in average, colon cancer patients are likely to be exposed to comorbidity. However, the influence of comorbidity on patients' care trajectory and survival is largely under-explored. Hence, we investigate the effect of comorbidity on patients care trajectory and survival based on an observational study in "real-life" setting. METHODS: This prospective observational study in two French regions includes patients aged over 18 and firstly treated for a colon cancer, stage II and III, diagnosed between 1st January and 31st December 2010. We assessed the influence of comorbidity (severe vs moderate or none), using the Charlson Comorbidity Index, on overall survival and patients' management steps. RESULTS: We analyzed 762 patients. We found comorbidity to be associated with adjuvant treatment delivery with a longer delay between surgery and chemotherapy initiation among patients with severe comorbidity. Severe comorbidity had an independent detrimental effect on overall survival that is slightly downsized after adjustment for adjuvant treatment delivery. CONCLUSION: Using observational "real-life" data, we showed that comorbidity impacts the colon cancer patients' care trajectory directly but also through indirect pathways involving adjuvant chemotherapy delivery. However, further studies are needed to better understand this mechanism.

Reproductive incompatibility between Amblyomma maculatum (Acari: Ixodidae) group ticks from two disjunct geographical regions within the USA.

The Amblyomma maculatum Koch group of ixodid ticks consists of three species: A. maculatum, A. triste, and A. tigrinum. However, since Koch described this group in 1844, the systematics of its members has been the subject of ongoing debate. This is especially true of A. maculatum and A. triste; recent molecular analyses reveal insufficient genetic divergence to separate these as distinct species. Further confounding this issue is the discovery in 2014 of A. maculatum group ticks in southern Arizona (AZ), USA, that share morphological characteristics with both A. triste and A. maculatum. To biologically evaluate the identity of A. maculatum group ticks from southern Arizona, we analyzed the reproductive compatibility between specimens of A. maculatum group ticks collected from Georgia (GA), USA, and southern Arizona. Female ticks from both Arizona and Georgia were mated with males from both the Georgia and Arizona Amblyomma populations, creating two homologous and two heterologous F1 cohorts of ticks: GA ♀/GA ♂, AZ ♀/AZ ♂, GA ♀/AZ ♂, and AZ ♀/GA ♂. Each cohort was maintained separately into the F2 generation with F1 females mating only with F1 males from their same cohort. Survival and fecundity parameters were measured for all developmental stages. The observed survival parameters for heterologous cohorts were comparable to those of the homologous cohorts through the F1 generation. However, the F1 heterologous females produced F2 egg clutches that did not hatch, thus indicating that the Arizona and Georgia populations of A. maculatum group ticks tested here represent different biological species.

The readily transformable Impatiens walleriana efficiently attracts nectar feeding with Aedes and Culex mosquitoes in simulated outdoor garden settings in Mississippi and Florida.

Mosquitoes rely upon plant nectars for their energy needs, a trait that has the potential to allow nectar to serve as a platform for producing and delivering toxins to nuisance and/or vector mosquito species. Impatiens walleriana (Order: Ericales, Family: Balsaminaceae) is a readily transformable and widely planted nectar plant that has been previously shown to attract mosquito nectar-feeding. However, those feeding studies were only conducted indoors and did not test if variable environmental conditions will affect nectar feeding. In this study, we tested incidence of nectar feeding from the extrafloral nectaries of I. walleriana with the mosquitoes Aedes aegypti, Ae. albopictus and Culex quinquefasciatus (Order: Diptera, Family: Culicidae) in simulated, outdoor garden settings in Mississippi and Florida. I. walleriana and other common garden plants (in a 1:4 ratio) were placed into a mesh-lined 4'x7' mesocosm along with 50 mosquitoes. To track nectar feeding, the nectar of I. walleriana was tagged with red dye and mosquitoes were analyzed for red dye fluorescence after feeding. Fluorescence analysis demonstrated that 81.9% of male and 86.6% of female mosquitoes fed on the nectar of I. walleriana within 24 h. This suggests that mosquitoes may readily feed on impatiens nectar in outdoor garden settings at temperate and semi-tropical sites, even when alternate common garden plants are available. This attraction capacity is essential for the further consideration of I. walleriana for development as a transgenic, mosquitocidal nectar plant.

Human immunoglobulin G responses to Cimex lectularius L. saliva.

AIMS: To investigate the immunoglobulin (Ig) G response after being fed upon by Cimex lectularius L. METHODS AND RESULTS: Participants were fed upon by three male C lectularius insects weekly for a month. Blood was obtained before the feeding and at the last feeding, which was used for immunoblots against bed bug salivary gland extract, with antihuman Immunoglobulin G (IgG) secondary antibodies. No consistent IgG changes developed in 11 humans serially fed upon by C lectularius. Two participants had new IgG responses to proteins at molecular weights of approximately 12-13 kDa, and one had an IgG response to a protein at approximately 40 kDa. At the last study visit, more intense IgG bands to proteins at molecular weights of 12-13 kDa had developed in 55% of participants (6/11) and at molecular weights of ≈30, ≈40 and ≈70 kDa in 45% (5/11) compared with the first study visit. Nitrophorin and apyrase were the most common C lectularius proteins identified with liquid chromatography-tandem mass spectrometry in both crushed bed bug salivary gland extract and post-bed bug feeding extract. CONCLUSIONS: Human participants did not have consistent IgG responses to crushed C lectularius salivary gland extract.

Frequency of Occurrence and Population-Dynamic Consequences of Different Forms of Density-Dependent Emigration.

Emigration is a fundamental process affecting species' local, regional, and large-scale dynamics. The paradigmatic view in ecology is that emigration is density independent (DIE) or positive density dependent (+DDE). However, alternative forms are biologically plausible, including negative (-DDE), U-shaped (uDDE), and hump-shaped (hDDE) forms. We reviewed the empirical literature to assess the frequency of different forms of density-dependent emigration and whether the form depended on methodology. We also developed a reaction-diffusion model to illustrate how different forms of DDE can affect patch-level population persistence. We found 145 studies, the majority representing DIE (30%) and +DDE (36%). However, we also regularly found -DDE (25%) and evidence for nonlinear DDE (9%), including one case of uDDE and two cases of hDDE. Nonlinear DDE detection is likely hindered by the use of few density levels and small density ranges. Based on our models, DIE and +DDE promoted stable and persistent populations. uDDE and -DDE generated an Allee effect that decreases minimum patch size. Last, -DDE and hDDE models yielded bistability that allows the establishment of populations at lower densities. We conclude that the emigration process can be a diverse function of density in nature and that alternative DDE forms can have important consequences for population dynamics.

Laboratory Studies of Questing Behavior in Colonized Nymphal Amblyomma maculatum Ticks (Acari: Ixodidae).

Environmental factors affect host-seeking behavior in ticks. In this study, 80 nymphal Amblyomma maculatum Koch were released in an observation arena containing four different heights of broomsedge stems (Andropogon virginicus L.) anchored in sand. Observations were made over three days as to proportion of ticks questing, questing height, and stem height distribution This scenario was replicated three times with different cohorts of ticks (n = 80 per replicate) for each of three treatment combinations of temperature and humidity: High temperature/high humidity (HTHH), high temperature/low humidity (HTLH), and low temperature/high humidity (LTHH). A fourth treatment utilizing the same size cohort and number of replicates included Wind (HTHHW+/-) by alternating days of wind and no-wind conditions over four days. Mean questing height for ticks under HTHH, HTLH, and LTHH conditions ranged from 4.45 to 6.03 cm with ticks questing significantly higher in HTHH. A significantly lower proportion ticks quested in HTLH (8.64%) than HTHH (14.06%) and LTHH (15.33%). In HTHH and LTHH, a significantly higher proportion of ticks were observed questing on 5-cm stems. Wind significantly reduced average questing height, and when absent, ticks on 20- and 30-cm stems quested significantly higher. These data indicate that A. macuatum nymphs randomly select stems to quest upon and climb upward until environmental conditions are prohibitive/ideal. Conditions with reduced vapor pressure deficit (VPD) led to higher questing frequency and height. Relatively low questing heights observed correspond with size of preferred hosts and may explain infrequency of collection by dragcloth in the field.