Hybrid speciation driven by multilocus introgression of ecological traits.

Hybridization allows adaptations to be shared among lineages and may trigger the evolution of new species1,2. However, convincing examples of homoploid hybrid speciation remain rare because it is challenging to demonstrate that hybridization was crucial in generating reproductive isolation3. Here we combine population genomic analysis with quantitative trait locus mapping of species-specific traits to examine a case of hybrid speciation in Heliconius butterflies. We show that Heliconius elevatus is a hybrid species that is sympatric with both parents and has persisted as an independently evolving lineage for at least 180,000 years. This is despite pervasive and ongoing gene flow with one parent, Heliconius pardalinus, which homogenizes 99% of their genomes. The remaining 1% introgressed from the other parent, Heliconius melpomene, and is scattered widely across the H. elevatus genome in islands of divergence from H. pardalinus. These islands contain multiple traits that are under disruptive selection, including colour pattern, wing shape, host plant preference, sex pheromones and mate choice. Collectively, these traits place H. elevatus on its own adaptive peak and permit coexistence with both parents. Our results show that speciation was driven by introgression of ecological traits, and that speciation with gene flow is possible with a multilocus genetic architecture.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview.

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Pervasive mimicry in flight behavior among aposematic butterflies.

Flight was a key innovation in the adaptive radiation of insects. However, it is a complex trait influenced by a large number of interacting biotic and abiotic factors, making it difficult to unravel the evolutionary drivers. We investigate flight patterns in neotropical heliconiine butterflies, well known for mimicry of their aposematic wing color patterns. We quantify the flight patterns (wing beat frequency and wing angles) of 351 individuals representing 29 heliconiine and 9 ithomiine species belonging to ten color pattern mimicry groupings. For wing beat frequency and up wing angles, we show that heliconiine species group by color pattern mimicry affiliation. Convergence of down wing angles to mimicry groupings is less pronounced, indicating that distinct components of flight are under different selection pressures and constraints. The flight characteristics of the Tiger mimicry group are particularly divergent due to convergence with distantly related ithomiine species. Predator-driven selection for mimicry also explained variation in flight among subspecies, indicating that this convergence can occur over relatively short evolutionary timescales. Our results suggest that the flight convergence is driven by aposematic signaling rather than shared habitat between comimics. We demonstrate that behavioral mimicry can occur between lineages that have separated over evolutionary timescales ranging from <0.5 to 70 My.

Latinx Individuals Who Smoke Daily with and without a Probable Anxiety Disorder: Differences in Smoking Behavior and Beliefs about Abstinence.

There is a well-established relation between anxiety psychopathology and smoking in the general population. However, little work focuses on Latinx/Hispanic (hereafter Latinx) persons who smoke from this comorbidity perspective. The present investigation aimed to explore differences among English-speaking Latinx adults who live in the United States (US) and smoke cigarettes with and without a probable anxiety disorder in terms of cigarette dependence, perceived barriers for quitting, severity of problems when quitting, and smoking abstinence expectancies. The sample included 338 adult Latinx daily cigarette smokers (Mage = 35.53 years; SD = 8.65; age range 18-61; 37.3% female) who identified as Latinx and were recruited nationally throughout the US. Results indicated that among Latinx persons who smoke, those with a probable anxiety disorder (compared to those without) were more likely to demonstrate higher levels of cigarette dependence, severity of problems when trying to quit, perceived barriers for quitting, and negative abstinence expectancies after adjusting for key variables linked to smoking and anxiety (e.g., hazardous drinking, education). The current findings are the first to document probable anxiety disorder status as a clinically relevant factor for a wide range of smoking variables and beliefs about abstinence among Latinx persons who smoke.

Anxiety-related constructs and smoking outcome expectancies among Latinx smokers.

Hispanic/Latinx (hereafter Latinx) smokers in the United States (US) experience unique smoking cessation-related challenges. Smoking outcome expectancies (i.e., positive and negative beliefs about the consequences of smoking behavior) have been linked to the maintenance of smoking and comorbidity with negative emotional states such as anxiety among Latinx smokers. However, past work has not characterized rates of probable anxiety disorder and elevated levels of anxiety sensitivity among English-speaking daily Latinx smokers from the United States or concurrently evaluated the explanatory relevance of anxiety symptoms and anxiety sensitivity for negative and positive smoking outcome expectancies. The present investigation sought to (a) determine the base rate of probable anxiety disorder and elevated anxiety sensitivity and (b) explore the unique roles of anxiety symptoms and anxiety sensitivity in relation to negative and positive smoking outcome expectancies. Participants included 338 English-speaking Latinx adult daily cigarette smokers from the United States (Mage = 35.53 years; SD = 8.65; age range 18-61; 37.3% female). Findings revealed high rates of probable anxiety disorder (50.9%) and elevated anxiety sensitivity (73.4%) among English-speaking Latinx smokers from the United States. Anxiety sensitivity, but not anxiety symptoms or disorders, was significantly related to negative consequences, negative reinforcement, positive reinforcement, and appetite/weight control smoking outcome expectancies. Overall, anxiety experiences were common among Latinx smokers, and anxiety sensitivity was a relatively more consistent and robust predictor of negative and positive outcome expectancies relative to anxiety symptoms and probable anxiety disorder. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The genetic basis of structural colour variation in mimetic Heliconius butterflies.

Structural colours, produced by the reflection of light from ultrastructures, have evolved multiple times in butterflies. Unlike pigmentary colours and patterns, little is known about the genetic basis of these colours. Reflective structures on wing-scale ridges are responsible for iridescent structural colour in many butterflies, including the Müllerian mimics Heliconius erato and Heliconius melpomene. Here, we quantify aspects of scale ultrastructure variation and colour in crosses between iridescent and non-iridescent subspecies of both of these species and perform quantitative trait locus (QTL) mapping. We show that iridescent structural colour has a complex genetic basis in both species, with offspring from crosses having a wide variation in blue colour (both hue and brightness) and scale structure measurements. We detect two different genomic regions in each species that explain modest amounts of this variation, with a sex-linked QTL in H. erato but not H. melpomene. We also find differences between species in the relationships between structure and colour, overall suggesting that these species have followed different evolutionary trajectories in their evolution of structural colour. We then identify genes within the QTL intervals that are differentially expressed between subspecies and/or wing regions, revealing likely candidates for genes controlling structural colour formation. This article is part of the theme issue 'Genetic basis of adaptation and speciation: from loci to causative mutations'.

Complex gastroschisis with apple peel jejunoileal atresia, primary closure, and Santulli procedure as a surgical alternative. Case report.

BACKGROUND: Gastroschisis is a closure defect of the abdominal wall classified as complex when it presents with necrosis, volvulus, or atresia of the gastrointestinal tract. Jejunoileal atresia is caused by abnormal closure, discontinuity, or narrowing of the intestine. Apple Peel or type IIIb is the rarest presentation, with an incidence of 1.3 per 10,000 live births. In addition to presenting a high mortality rate. PRESENTATION OF CASE: We present a preterm newborn patient of 30 weeks with a diagnosis of gastroschisis and jejunoileal atresia type IIIB. The congenital wall defect was closed in the first surgical stage, and he was then taken at four weeks to correct the atresia. In the second surgery, we found a difference in intestinal calibers of 8:1, and the surgical team decides to perform remodeling of the proximal sac with a mechanical stapler and perform anastomosis using the Santulli technique. On day 6 of life, enteral feeding began through a nutrition tube localized under intestinal anastomosis with progressive nutritional increase. Subsequently, intermittent and progressive occlusion of the stoma was performed, leading the patient to a definitive surgical closure one month later. CONCLUSIONS: The mortality rate for gastroschisis and complex intestinal atresia is high. Advances in prenatal diagnosis, neonatal intensive care, and proper surgical correction are crucial to improving survival rates. The Santulli procedure is a surgical alternative for intestinal atresias with a caliber discrepancy greater than 4 to 1 or when the characteristics of the distal part do not allow a primary anastomosis to be performed.

Evolución del cáncer papilar de tiroides en acromegalia: serie de casos / Evolution of papillary thyroid cancer in acromegaly: case series / Evolução do câncer papilar de tireoide na acromegalia: série de casos

Introducción: La acromegalia se produce por un adenoma hipofisario somatotropo, que secreta una excesiva producción de GH e IGF1, se relaciona con mayor riesgo de tumores malignos, no guardando asociación con un patrón especifico de presentación y el objetivo de este estudio es analizar la evolución del cáncer papilar de tiroides en acromegalia. Casos: Se trata de tres pacientes diagnosticados de carcinoma papilar de tiroides (CPT) con diferente pronóstico, con características faciales, y sintomatología como cefalea, alteraciones del campo visual, alteraciones menstruales, que condujeron a la realización de estudios bioquímicos, de imagen y al diagnóstico de acromegalia. Evolución: La aparición de cáncer de tiroides varía en el tiempo de evolución de la acromegalia, en dos de los casos lo antecedió y en el tercero se presentó a la par con esta patología. La respuesta al tratamiento en el CPT es indeterminada en la primera paciente y \excelente en los otros casos; en una paciente se alcanzó remisión. Conclusiones: la coexistencia de acromegalia con cáncer tiroides es posible, que los cambios acrales, faciales y la sintomatología expansiva del tumor conducen al diagnóstico de acromegalia y que la identificación de malignidades no guarda relación con la evolución de la enfermedad.

Introduction: Acromegaly is produced by a somatotropic pituitary adenoma, which secretes an excessive production of GH and IGF1, it is related to a higher risk of malignant tumors, not being associated with a specific pattern of presentation and the objective of this study is to analyze the evolution of papillary thyroid cancer in acromegaly. Cases report: These were three patients diagnosed with CPT with different prognosis, with facial characteristics, and symptoms such as headache, visual field alterations, menstrual alterations, which led to biochemical and imaging studies and the diagnosis of acromegaly. Evolution: The appearance of thyroid cancer in the time of evolution of acromegaly is different, in two of the cases it preceded it and in the third it was presented alongside this pathology. The re-sponse to treatment in CPT is indeterminate in the first patient and excellent in the other cases; re-mission was achieved in one patient. Conclusions: It is concluded that the coexistence of acromegaly with thyroid cancer is possible, that the acral and facial changes and the expansive symptomatology of the tumor lead to the diag-nosis of acromegaly and that the identification of malignancies is not related to the evolution of the disease.

Introdução: A acromegalia é produzida por um adenoma hipofisário somatotrópico, que secreta uma produção excessiva de GH e IGF1, está relacionada a um maior risco de tumores malignos, não estando associada a um padrão específico de apresentação e o objetivo deste estudo é analisar a evolução de câncer papilar de tireoide na acromegalia. Casos: São três pacientes com diagnóstico de carcinoma papilífero de tireoide (CPT) de prognóstico diferente, com características faciais e sintomas como cefaleia, alterações do campo visual, alterações menstruais, que levaram à realização de estudos bioquímicos, de imagem e diagnóstico de acromegalia. Evolução: O aparecimento do câncer de tireoide varia com o tempo de evolução da acromegalia, em dois dos casos ela o precedeu e no terceiro foi apresentado concomitantemente a esta patologia. A resposta ao tratamento no CPT é indeterminada no primeiro paciente e excelente nos demais casos; a remissão foi alcançada em um paciente. Conclusões: a coexistência de acromegalia com câncer de tireoide é possível, que as alterações acrais e faciais e a sintomatologia expansiva do tumor levam ao diagnóstico de acromegalia e que a identificação de neoplasias não está relacionada à evolução da doença.

Genomics of altitude-associated wing shape in two tropical butterflies.

Understanding how organisms adapt to their local environment is central to evolution. With new whole-genome sequencing technologies and the explosion of data, deciphering the genomic basis of complex traits that are ecologically relevant is becoming increasingly feasible. Here, we studied the genomic basis of wing shape in two Neotropical butterflies that inhabit large geographical ranges. Heliconius butterflies at high elevations have been shown to generally have rounder wings than those in the lowlands. We reared over 1,100 butterflies from 71 broods of H. erato and H. melpomene in common-garden conditions and showed that wing aspect ratio, that is, elongatedness, is highly heritable in both species and that elevation-associated wing aspect ratio differences are maintained. Genome-wide associations with a published data set of 666 whole genomes from across a hybrid zone, uncovered a highly polygenic basis to wing aspect ratio variation in the wild. We identified several genes that have roles in wing morphogenesis or wing aspect ratio variation in Drosophila flies, making them promising candidates for future studies. There was little evidence for molecular parallelism in the two species, with only one shared candidate gene, nor for a role of the four known colour pattern loci, except for optix in H. erato. Thus, we present the first insights into the heritability and genomic basis of within-species wing aspect ratio in two Heliconius species, adding to a growing body of evidence that polygenic adaptation may underlie many ecologically relevant traits.

Haplotype tagging reveals parallel formation of hybrid races in two butterfly species.

Genetic variation segregates as linked sets of variants or haplotypes. Haplotypes and linkage are central to genetics and underpin virtually all genetic and selection analysis. Yet, genomic data often omit haplotype information due to constraints in sequencing technologies. Here, we present "haplotagging," a simple, low-cost linked-read sequencing technique that allows sequencing of hundreds of individuals while retaining linkage information. We apply haplotagging to construct megabase-size haplotypes for over 600 individual butterflies (Heliconius erato and H. melpomene), which form overlapping hybrid zones across an elevational gradient in Ecuador. Haplotagging identifies loci controlling distinctive high- and lowland wing color patterns. Divergent haplotypes are found at the same major loci in both species, while chromosome rearrangements show no parallelism. Remarkably, in both species, the geographic clines for the major wing-pattern loci are displaced by 18 km, leading to the rise of a novel hybrid morph in the center of the hybrid zone. We propose that shared warning signaling (Müllerian mimicry) may couple the cline shifts seen in both species and facilitate the parallel coemergence of a novel hybrid morph in both comimetic species. Our results show the power of efficient haplotyping methods when combined with large-scale sequencing data from natural populations.

COVID-19 and Anxiety Sensitivity Across Two Studies in Argentina: Associations with COVID-19 Worry, Symptom Severity, Anxiety, and Functional Impairment.

BACKGROUND: The novel 2019 SARS2-Coronavirus (COVID-19) has had a devastating physical health, mental health, and economic impact, causing millions of infections and hundreds of thousands of deaths. While COVID-19 has impacted the entire world, COVID-19 has disproportionately impacted low-income countries, particularly in South America, causing not only increased mortality but also increased associated mental health complaints. Anxiety sensitivity (AS), reflecting fear of anxiety-related physical sensations, may be particularly important to understand COVID-19 mental health effects among Latinx individuals in South America (Argentina). Past work suggests that Latinx individuals report greater somatization of mental health symptoms, and AS has been specifically linked to greater mental health symptoms. Yet, to date, no work has examined AS as a vulnerability factor for the negative mental health effects of COVID-19. METHOD: Therefore, the current manuscript examined the association of AS with COVID-19 worry, functional impairment, anxiety, and symptom severity across two samples of adults in Argentina: a community sample (n = 105, M age = 38.58, SD = 14.07, 69.5% female) and a clinical sample comprised of individuals with an anxiety disorder (n = 99, M age = 34.99, SD = 10.83, 66.7% female). RESULTS: Results from the current study provide support for AS as a potential vulnerability factor for COVID-19-related mental health problems across both samples, and these effects were evident over and above the variance accounted for by age, sex, pre-existing medical conditions, and COVID-19 exposure. CONCLUSIONS: These data identify AS as a potential intervention target to reduce COVID-19 mental health burden among adults in Argentina.

Limited genetic parallels underlie convergent evolution of quantitative pattern variation in mimetic butterflies.

Mimetic systems allow us to address the question of whether the same genes control similar phenotypes in different species. Although widespread parallels have been found for major effect loci, much less is known about genes that control quantitative trait variation. In this study, we identify and compare the loci that control subtle changes in the size and shape of forewing pattern elements in two Heliconius butterfly co-mimics. We use quantitative trait locus (QTL) analysis with a multivariate phenotyping approach to map the variation in red pattern elements across the whole forewing surface of Heliconius erato and Heliconius melpomene. These results are compared with a QTL analysis of univariate trait changes, and show that our resolution for identifying small effect loci is somewhat improved with the multivariate approach, but also that different loci are detected with these different approaches. QTL likely corresponding to the known patterning gene optix were found in both species but otherwise, a remarkably low level of genetic parallelism was found. This lack of similarity indicates that the genetic basis of convergent traits may not be as predictable as assumed from studies that focus solely on Mendelian traits.

Phenotypic variation in Heliconius erato crosses shows that iridescent structural colour is sex-linked and controlled by multiple genes.

Bright, highly reflective iridescent colours can be seen across nature and are produced by the scattering of light from nanostructures. Heliconius butterflies have been widely studied for their diversity and mimicry of wing colour patterns. Despite iridescence evolving multiple times in this genus, little is known about the genetic basis of the colour and the development of the structures which produce it. Heliconius erato can be found across Central and South America, but only races found in western Ecuador and Colombia have developed blue iridescent colour. Here, we use crosses between iridescent and non-iridescent races of H. erato to study phenotypic variation in the resulting F2 generation. Using measurements of blue colour from photographs, we find that iridescent structural colour is a quantitative trait controlled by multiple genes, with strong evidence for loci on the Z sex chromosome. Iridescence is not linked to the Mendelian colour pattern locus that also segregates in these crosses (controlled by the gene cortex). Small-angle X-ray scattering data show that spacing between longitudinal ridges on the scales, which affects the intensity of the blue reflectance, also varies quantitatively in F2 crosses.

Wilkie's syndrome, a missed opportunity.

Wilkie's syndrome is a rare cause of duodenal obstruction that can easily be missed at clinical practice. It is characterized by nausea, abdominal pain and vomit. It usually affects young adults, and it's caused by a low aortomesenteric angle resulting in vascular compression of the duodenum. Symptoms could resemble many of the symptoms presented in a patient with a suspected eating disorder. The non-specificity of the clinical signs and symptoms can confuse, delay the diagnosis and expose the patient to potentially hazardous therapies. We report a case of a 20-year-old patient who presented to the emergency room with a history of intermittent vomiting and abdominal pain. He had been previously misdiagnosed with an eating disorder and received physiological therapy. Nonetheless, his pain persisted. After further evaluation with the use of imaging techniques, a low aortomesenteric angle was discovered. He underwent surgery and completely recovered. On follow up controls patient is well and he no longer had episodes of vomiting.

Gallbladder duplication and cholecystitis.

Cholecystitis is a common gallbladder pathology characterized by abdominal pain, positive Murphy sign and elevated white blood count. Abdominal ultrasound usually gives a definite diagnosis. Duplication of the gallbladder is a rare congenital anomaly that can either be asymptomatic or and can present with symptoms associated with cholelithiasis, cholecystitis, cholangitis or pancreatitis. Clinically indistinguishable from regular gallbladder pathologies. The management of duplicated gallbladder is similar to that of other gallbladder diseases, if one or both gallbladders cause symptoms, cholecystectomy should be done for both gallbladders. We present a case of a 50-year-old female patient, she presented to the emergency room with abdominal pain and tenderness. Ultrasound detected a gallbladder duplication with cholecystitis in one of them and magnetic resonance cholangiopancreatography confirmed this diagnosis. Surgery was decided and the patient underwent full recovery. Y-shaped gallbladder duplication with cholecystitis due to cholelithiasis in one of them was the final diagnosis.

Frequency dependence shapes the adaptive landscape of imperfect Batesian mimicry.

Despite more than a century of biological research on the evolution and maintenance of mimetic signals, the relative frequencies of models and mimics necessary to establish and maintain Batesian mimicry in natural populations remain understudied. Here we investigate the frequency-dependent dynamics of imperfect Batesian mimicry, using predation experiments involving artificial butterfly models. We use two geographically distinct populations of Adelpha butterflies that vary in their relative frequencies of a putatively defended model (Adelpha iphiclus) and Batesian mimic (Adelpha serpa). We found that in Costa Rica, where both species share similar abundances, Batesian mimicry breaks down, and predators more readily attack artificial butterfly models of the presumed mimic, A. serpa By contrast, in Ecuador, where A. iphiclus (model) is significantly more abundant than A. serpa (mimic), both species are equally protected from predation. Our results provide compelling experimental evidence that imperfect Batesian mimicry is frequency-dependent on the relative abundance of models and mimics in natural populations, and contribute to the growing body of evidence that complex dynamics, such as seasonality or the availability of alternative prey, influence the evolution of mimetic traits.

Population genomics of parallel hybrid zones in the mimetic butterflies, H. melpomene and H. erato.

Hybrid zones can be valuable tools for studying evolution and identifying genomic regions responsible for adaptive divergence and underlying phenotypic variation. Hybrid zones between subspecies of Heliconius butterflies can be very narrow and are maintained by strong selection acting on color pattern. The comimetic species, H. erato and H. melpomene, have parallel hybrid zones in which both species undergo a change from one color pattern form to another. We use restriction-associated DNA sequencing to obtain several thousand genome-wide sequence markers and use these to analyze patterns of population divergence across two pairs of parallel hybrid zones in Peru and Ecuador. We compare two approaches for analysis of this type of data-alignment to a reference genome and de novo assembly-and find that alignment gives the best results for species both closely (H. melpomene) and distantly (H. erato, ∼15% divergent) related to the reference sequence. Our results confirm that the color pattern controlling loci account for the majority of divergent regions across the genome, but we also detect other divergent regions apparently unlinked to color pattern differences. We also use association mapping to identify previously unmapped color pattern loci, in particular the Ro locus. Finally, we identify a new cryptic population of H. timareta in Ecuador, which occurs at relatively low altitude and is mimetic with H. melpomene malleti.

Disruptive ecological selection on a mating cue.

Adaptation to divergent ecological niches can result in speciation. Traits subject to disruptive selection that also contribute to non-random mating will facilitate speciation with gene flow. Such 'magic' or 'multiple-effect' traits may be widespread and important for generating biodiversity, but strong empirical evidence is still lacking. Although there is evidence that putative ecological traits are indeed involved in assortative mating, evidence that these same traits are under divergent selection is considerably weaker. Heliconius butterfly wing patterns are subject to positive frequency-dependent selection by predators, owing to aposematism and Müllerian mimicry, and divergent colour patterns are used by closely related species to recognize potential mates. The amenability of colour patterns to experimental manipulation, independent of other traits, presents an excellent opportunity to test their role during speciation. We conducted field experiments with artificial butterflies, designed to match natural butterflies with respect to avian vision. These were complemented with enclosure trials with live birds and real butterflies. Our experiments showed that hybrid colour-pattern phenotypes are attacked more frequently than parental forms. For the first time, we demonstrate disruptive ecological selection on a trait that also acts as a mating cue.

Evolution of a mimicry supergene from a multilocus architecture.

The origin and evolution of supergenes have long fascinated evolutionary biologists. In the polymorphic butterfly Heliconius numata, a supergene controls the switch between multiple different forms, and results in near-perfect mimicry of model species. Here, we use a morphometric analysis to quantify the variation in wing pattern observed in two broods of H. numata with different alleles at the supergene locus, 'P'. Further, we genotype the broods to associate the variation we capture with genetic differences. This allows us to begin mapping the quantitative trait loci that have minor effects on wing pattern. In addition to finding loci on novel chromosomes, our data, to our knowledge, suggest for the first time that ancestral colour-pattern loci, known to have major effects in closely related species, may contribute to the wing patterns displayed by H. numata, despite the large transfer of effects to the supergene.

Altitudinal patterns of spider sociality and the biology of a new midelevation social Anelosimus species in Ecuador.

To the extent that geography correlates with particular environmental parameters, the geographical distribution of phylogenetically related social and nonsocial organisms should shed light on the conditions that lead to sociality versus nonsociality. Social spiders are notorious for being concentrated in tropical regions of the world, occupying a set of habitats more restricted than those available to the phylogenetic lineages in which they occur. Here we document a parallel pattern involving elevation in the spider genus Anelosimus in America and describe the biology of a newly discovered social species found at what appears to be the altitudinal edge of sociality in the genus. We show that this is a cooperative permanent-social species with highly female-biased sex ratios but colonies that are one to two orders of magnitude smaller than those of a low-elevation congener of similar body size. We suggest that the absence of subsocial Anelosimus species in the lowland rain forest may be due to an increased probability of maternal death in this habitat due to greater predation and/or precipitation, while absence of a sufficient supply of large insects at high elevations or latitudes may restrict social species to low- to midelevation tropical moist forests. We refer to these as the "maternal survival" and "prey size" hypotheses, respectively, and suggest that both in combination may explain the geographical distribution of sociality in the genus.