Evolutionary importance of intraspecific variation in sex pheromones

Sex pheromones in many insect species are important species-recognition signals that attract conspecifics and inhibit attraction between heterospecifics; therefore, sex pheromones have predominantly been considered to evolve due to interactions between species. Recent research, however, is uncovering roles for these signals in mate choice, and that variation within and between populations can be drivers of species evolution. Variation in pheromone communication channels arises from a combination of context-dependent, condition-dependent, or genetic mechanisms in both signalers and receivers. Variation can affect mate choice and thus gene flow between individuals and populations, affecting species' evolution. The complex interactions between intraspecific and interspecific selection forces calls for more integrative studies to understand the evolution of sex pheromone communication.Peer reviewe

Multimodal Aposematic Signals and Their Emerging Role in Mate Attraction

Chemically defended animals often display conspicuous color patterns that predators learn to associate with their unprofitability and subsequently avoid. Such animals (i.e., aposematic), deter predators by stimulating their visual and chemical sensory channels. Hence, aposematism is considered to be "multimodal." The evolution of warning signals (and to a lesser degree their accompanying chemical defenses) is fundamentally linked to natural selection by predators. Lately, however, increasing evidence also points to a role of sexual selection shaping warning signal evolution. One of the species in which this has been shown is the wood tiger moth, Arctia plantaginis, which we here put forward as a promising model to investigate multimodality in aposematic and sexual signaling. A. plantaginis is an aposematic diurnal moth which exhibits sexually dimorphic coloration as well as sex-limited polymorphism in part of its range. The anti-predator function of its coloration and, more recently, its chemical defenses (even when experimentally decoupled from the visual signals), has been well-demonstrated. Interestingly, recent studies have revealed differences between the two male morphs in mating success, suggesting a role of coloration in mate choice or attraction, and providing a possible explanation for its sexual dimorphism in coloration. Here, we: (1) review the lines of evidence showing the role of predation pressure and sexual selection in the evolution of multimodal aposematic signals in general, and in the wood tiger moth in particular; (2) establish gaps in current research linking sexual selection and predation as selective pressures on aposematic signals by reviewing a sample of the literature published in the last 30 years; (3) highlight the need of identifying suitable systems to address simultaneously the effect of natural and sexual selection on multimodal aposematic signals; and (4) propose directions for future research to test how aposematic signals can evolve under natural and sexual selection.Peer reviewe

On the maintenance of intrapopulation genetic variation: the interplay between sexual selection, chemical communication, and fitness in the wood tiger moth (Arctia plantaginis)

The maintenance of intrapopulation phenotypic trait variation often is the result of the interplay between multiple selective forces. Genetic associations between color traits and life-history traits can create context-dependent advantages and affect intrapopulation dynamics. In the polymorphic wood tiger moth (Arctia plantaginis), the two male hindwing phenotypes (genotypes: WW/Wy = white, yy = yellow) show morph-linked advantages that are context-dependent across ecological contexts. Although female hindwing coloration spans continuously from yellow to red they genetically bear the same male color alleles. In this thesis, I investigated the potential contribution of sexual selection, chemical communication, and fitness of the different genetic color morphs (i.e., WW, Wy, yy) in maintaining the two male color morphs. Mate choice and mate recruitment were affected by context-dependent advantages. yy females were more attractive to males in high-density scenarios because of their early calling strategy that likely allowed them to outcompete WW and Wy females. WW females were, instead, more attractive when females were simultaneously calling, perhaps due to their longer calling duration. yy males were faster to reach females than white (WW, Wy) males in low-density scenarios, while white males and males with denser antennae (i.e., higher lamellae count) located females faster in high-density scenarios. At the reproductive level, males and females showed genotype-specific (dis)advantages. Wy females benefit from higher likelihood of reproductive output among female genotypes leading to strong heterozygote advantage. yy males had the lowest reproductive output among male genotypes while pairs with yellow females suffered the lowest mating success. The presence of one or two copies of the yellow allele affected several life-history traits, from pre- to post-copulatory stages. Thus, the color locus has pleiotropic effects on several life-history traits, offering a mechanism of balancing selection that enables the persistence of genetic and phenotypic variation in natural populations. Keywords: Balancing selection; heterozygote advantage; pleiotropy; receiver antenna variation; signaling strategy variation; wood tiger mothPopulaation geneettistä muuntelua ylläpitävät useiden valintapaineiden yhteisvaikutukset. Ominaisuuksien geneettinen kytkeytyminen elinkierto-piirteiden välillä ja niiden kelpoisuusvaikutukset voivat olla tilanteesta riippuen joko positiivisia tai negatiivisia. Nämä kytkeytymiset vaikuttavat siten geneetisen muuntelun dynamiikkaan. Polymorfisella täpläsiilikäs perhosella (Arctia plantaginis) koiraiden takasiipien kaksi värimuotoa (genotyypit: WW/Wy = valkoinen, yy = keltainen) ovat kytkeytyneet useisiin elinkierto-piirteisiin. Naaraat kantavat samoja alleeleja, mutta naaraiden takasiipien väritys vaihtelee tasaisesti keltaisesta punaiseen. Tässä tutkielmassa perehdyin näiden värimuotojen (WW, Wy, yy) välisiin eroihin seksuaalivalinnassa, kemiallisessa viestinnässä ja kelpoisuudessa sekä tutkin geenikytkentöjen roolia populaation polymorfisen muuntelun säilymisessä. Värimuotojen välillä oli eroja kumppaneiden houkuttelussa ja valinnassa: yy-naaraat houkuttelivat koiraita tehokkaammin korkeammissa koirastiheyksissä. Tämä johtui todennäköisesti erilaisista naaraiden strategioista: yy-naaraat aloittavat houkuttelun aiemmin kuin WW ja Wy genotyyppien naaraat ja saivat näin kilpailuedun. Toisaalta WW-naaraat pystyivät jatkamaan houkuttelua pidempään kuin yy-naaraat. Keltaiset (yy) koiraat löysivät naaraat valkoisia (WW, Wy) koiraita nopeammin matalammissa tiheyksissä, kun taas valkoiset koiraat sekä koiraat, joiden tuntosarvien aistinsolujen tiheys oli korkea, löysivät naaraat nopeammin korkeammissa tiheyksissä. Värigenotyyppien välillä oli myös lisääntymiseen liittyviä eroja, mikä viittaa voimakkaaseen heterotsygootin etuun: Wy-naaraiden lisääntymismenestys oli korkeampi kuin WW ja yy naaraiden. yy-naaraiden pariutumistodennäköisyys oli heikoin. Myös keltaisilla koirailla oli heikoin lisääntymismenestys. Keltaisen y-alleelin läsnäolo vaikutti siis negatiivisesti useisiin elinkierto-ominaisuuksiin. Värityksen määräävien alleelien pleiotrooppiset vaikutukset johtavat stabiloivaan valintaan, joka voi mahdollistaa genotyyppisen ja fenotyyppisen muuntelun säilymisen populaatiossa. Avainsanat: Heterotsygootin etu; pleiotropia; polymorfia; stabiloiva valint

Colour alone matters : no predator generalization among morphs of an aposematic moth

Local warning colour polymorphism, frequently observed in aposematic organisms, is evolutionarily puzzling. This is because variation in aposematic signals is expected to be selected against due to predators' difficulties associating several signals with a given unprofitable prey. One possible explanation for the existence of such variation is predator generalization, which occurs when predators learn to avoid one form and consequently avoid other sufficiently similar forms, relaxing selection for monomorphic signals. We tested this hypothesis by exposing the three different colour morphs of the aposematic wood tiger moth, Arctia plantaginis, existing in Finland to local wild-caught predators (blue tits, Cyanistes caeruleus). We designed artificial moths that varied only in their hindwing coloration (white, yellow and red) keeping other traits (e.g. wing pattern and size) constant. Thus, if the birds transferred their aversion of one morph to the other two we could infer that their visual appearances are sufficiently similar for predator generalization to take place. We found that, surprisingly, birds showed no preference or aversion for any of the three morphs presented. During the avoidance learning trials, birds learned to avoid the red morph considerably faster than the white or yellow morphs, confirming previous findings on the efficacy of red as a warning signal that facilitates predator learning. Birds did not generalize their learned avoidance of one colour morph to the other two morphs, suggesting that they pay more attention to conspicuous wing coloration than other traits. Our results are in accordance with previous findings that coloration plays a key role during avoidance learning and generalization, which has important implications for the evolution of mimicry. We conclude that, in the case of wood tiger moths, predator generalization is unlikely to explain the unexpected coexistence of different morphs.peerReviewe

Heterozygote advantage and pleiotropy contribute to intraspecific color trait variability

The persistence of intrapopulation phenotypic variation typically requires some form of balancing selection since drift and directional selection eventually erode genetic variation. Heterozygote advantage remains a classic explanation for the maintenance of genetic variation in the face of selection. However, examples of heterozygote advantage, other than those associated with disease resistance are rather uncommon. Across most of its distribution, males of the aposematic moth Arctia plantaginis have two hindwing phenotypes determined by a heritable one locus-two allele polymorphism (genotypes: WW/Wy = white morph, yy = yellow morph). Using genotyped moths we show that the presence of one or two copies of the yellow allele affects several life-history traits. Reproductive output of both males and females, and female mating success are negatively affected by two copies of the yellow allele. Females carrying one yellow allele (i.e. Wy) have higher fertility, hatching success, and offspring survival than either homozygote, thus leading to strong heterozygote advantage. Our results indicate strong female contribution especially at the postcopulatory stage in maintaining the color polymorphism. The interplay between heterozygote advantage, yellow allele pleiotropic effect and morph-specific predation pressure may exert balancing selection on the color locus, suggesting that color polymorphism may be maintained through complex interactions between natural and sexual selection.peerReviewe

Stoma-free survival after anastomotic leak following rectal cancer resection: worldwide cohort of 2470 patients

Background: The optimal treatment of anastomotic leak after rectal cancer resection is unclear. This worldwide cohort study aimed to provide an overview of four treatment strategies applied. Methods: Patients from 216 centres and 45 countries with anastomotic leak after rectal cancer resection between 2014 and 2018 were included. Treatment was categorized as salvage surgery, faecal diversion with passive or active (vacuum) drainage, and no primary/secondary faecal diversion. The primary outcome was 1-year stoma-free survival. In addition, passive and active drainage were compared using propensity score matching (2: 1). Results: Of 2470 evaluable patients, 388 (16.0 per cent) underwent salvage surgery, 1524 (62.0 per cent) passive drainage, 278 (11.0 per cent) active drainage, and 280 (11.0 per cent) had no faecal diversion. One-year stoma-free survival rates were 13.7, 48.3, 48.2, and 65.4 per cent respectively. Propensity score matching resulted in 556 patients with passive and 278 with active drainage. There was no statistically significant difference between these groups in 1-year stoma-free survival (OR 0.95, 95 per cent c.i. 0.66 to 1.33), with a risk difference of -1.1 (95 per cent c.i. -9.0 to 7.0) per cent. After active drainage, more patients required secondary salvage surgery (OR 2.32, 1.49 to 3.59), prolonged hospital admission (an additional 6 (95 per cent c.i. 2 to 10) days), and ICU admission (OR 1.41, 1.02 to 1.94). Mean duration of leak healing did not differ significantly (an additional 12 (-28 to 52) days). Conclusion: Primary salvage surgery or omission of faecal diversion likely correspond to the most severe and least severe leaks respectively. In patients with diverted leaks, stoma-free survival did not differ statistically between passive and active drainage, although the increased risk of secondary salvage surgery and ICU admission suggests residual confounding

Stoma-free Survival After Rectal Cancer Resection With Anastomotic Leakage: Development and Validation of a Prediction Model in a Large International Cohort.

Objective:To develop and validate a prediction model (STOMA score) for 1-year stoma-free survival in patients with rectal cancer (RC) with anastomotic leakage (AL).Background:AL after RC resection often results in a permanent stoma.Methods:This international retrospective cohort study (TENTACLE-Rectum) encompassed 216 participating centres and included patients who developed AL after RC surgery between 2014 and 2018. Clinically relevant predictors for 1-year stoma-free survival were included in uni and multivariable logistic regression models. The STOMA score was developed and internally validated in a cohort of patients operated between 2014 and 2017, with subsequent temporal validation in a 2018 cohort. The discriminative power and calibration of the models' performance were evaluated.Results:This study included 2499 patients with AL, 1954 in the development cohort and 545 in the validation cohort. Baseline characteristics were comparable. One-year stoma-free survival was 45.0% in the development cohort and 43.7% in the validation cohort. The following predictors were included in the STOMA score: sex, age, American Society of Anestesiologist classification, body mass index, clinical M-disease, neoadjuvant therapy, abdominal and transanal approach, primary defunctioning stoma, multivisceral resection, clinical setting in which AL was diagnosed, postoperative day of AL diagnosis, abdominal contamination, anastomotic defect circumference, bowel wall ischemia, anastomotic fistula, retraction, and reactivation leakage. The STOMA score showed good discrimination and calibration (c-index: 0.71, 95% CI: 0.66-0.76).Conclusions:The STOMA score consists of 18 clinically relevant factors and estimates the individual risk for 1-year stoma-free survival in patients with AL after RC surgery, which may improve patient counseling and give guidance when analyzing the efficacy of different treatment strategies in future studies