The orientation inducer pheromone of the fire ant Solenopsis invicta

Abstract Foraging ants recruit nestmate workers to food sources by a variety of mechanisms. We report that one behavioural subcategory of the recruitment pheromone complex of Solenopsis invicta Buren involves orientation induction. The orientation inducer pheromone exerts its effects by changing the physiological state of the recipient rather than by releasing a measurable behaviour. Some ant species use a physical 'waggle' behaviour to motivate (change physiological state) nestmate workers to follow their chemical trail. The orientation inducer pheromone can be interpreted as a chemical analogue of the physical 'waggle' inducing effects. This behaviour is not elicited by the recruitment pheromone components responsible for orientation and/or attraction. Each of these behavioural categories is mediated by a different blend of chemicals from the Dufour's gland. Activity-concentration thresholds indicate that the attraction and inducer part of the recruitment pheromone require about 250 times more worker equivalents for a response than the orientation pheromone. Therefore, the recruitment sub-categories are differentially activated by the amount of Dufour's gland material released.     

Phylogenetic distribution of a male pheromone that may exploit a nonsexual preference in lampreys

Pheromones are among the most important sexual signals used by organisms throughout the animal kingdom. However, few are identified in vertebrates, leaving the evolutionary mechanisms underlying vertebrate pheromones poorly understood. Pre‐existing biases in receivers' perceptual systems shape visual and auditory signalling systems, but studies on how receiver biases influence the evolution of pheromone communication remain sparse. The lamprey Petromyzon marinus uses a relatively well‐understood suite of pheromones and offers a unique opportunity to study the evolution of vertebrate pheromone communication. Previous studies indicate that male signalling with the mating pheromone 3‐keto petromyzonol sulphate (3kPZS) may exploit a nonsexual attraction to juvenile‐released 3kPZS that guides migration into productive rearing habitat. Here, we infer the distribution of male signalling with 3kPZS using a phylogenetic comparison comprising six of 10 genera and two of three families. Our results indicate that only P. marinus and Ichthyomyzon castaneus release 3kPZS at high rates. Olfactory and behavioural assays with P. marinus, I. castaneus and a subset of three other species that do not use 3kPZS as a sexual signal indicate that male signalling might have driven the evolution of female adaptations to detect 3kPZS with specific olfactory mechanisms and respond to 3kPZS with targeted attraction relevant during mate search. We postulate that 3kPZS communication evolved independently in I. castaneus and P. marinus, but cannot eliminate the alternative that other species lost 3kPZS communication. Regardless, our results represent a rare macroevolutionary investigation of a vertebrate pheromone and provide insight into the evolutionary mechanisms underlying pheromone communication.     

Whole genome-based phylogenetic analysis of bacterial two-component systems

To adapt to their environment, bacterial strains have developed various environmental signal sensing systems or twocomponent systems. To evaluate the evolutionary relationship of two-component systems, 246 two-component system genes from KEGG were analyzed. Phylogenetic tree structure indicated that most two-component systems are strain specific. Most of two-component system genes have co-evolved, and some two-component system pairs have evolved via recruitment model. By two-component system gene content analysis, new aspect of cellular metabolism evolution was provided.     

Visual and chemical cues provide redundant information in the multimodal recruitment system of the stingless bee <Emphasis Type="Italic">Scaptotrigona mexicana</Emphasis> (Apidae,Meliponini)

Multimodal communication plays an important role in pollination biology. Bees have evolved multimodal communication to recruit nestmates to rewarding food sources. Highly social bees can use visual and chemical information to recruit nestmates to rich food sources. However, no studies have determined if this information is redundant or has an additive effect such that multimodal information is more attractive than either modality presented by itself to free-flying bees. We tested the effect of two modalities, forager-deposited odor marks and the visual presence of foragers, on the orientation of stingless bee (Scaptotrigona mexicana) recruits. Our results show that odor marks alone were significantly more attractive than multimodal information, and that multimodal information was significantly more attractive than visual forager presence alone. Given the high olfactory sensitivity and limited visual acuity of insects, odor marks likely attracted recruits over a greater distance than the visual presence of nestmates. Thus, multimodal information in S. mexicana is redundant, not additive, in terms of orientation to food sources.     

Sexual selection and trichromatic color vision in primates: statistical support for the preexisting-bias hypothesis

The evolution of trichromatic color vision in primates may improve foraging performance as well as intraspecific communication; however, the context in which color vision initially evolved is unknown. We statistically examined the hypothesis that trichromatic color vision in primates represents a preexisting bias for the evolution of red coloration (pelage and/or skin) through sexual selection. Our analyses show that trichromatic color vision evolved before red pelage and red skin, as well as before gregarious mating systems that would promote sexual selection for visual traits and other forms of intraspecific communication via red traits. We also determined that both red pelage and red skin were more likely to evolve in the presence of color vision and mating systems that promote sexual selection. These results provide statistical support for the hypothesis that trichromatic color vision in primates evolved in a context other than intraspecific communication with red traits, most likely foraging performance, but, once evolved, represented a preexisting bias that promoted the evolution of red traits through sexual selection.     

Heterogeneous tempo and mode of evolutionary diversification of compounds in lizard chemical signals

Important part of the multivariate selection shaping social and interspecific interactions among and within animal species emerges from communication. Therefore, understanding the diversification of signals for animal communication is a central endeavor in evolutionary biology. Over the last decade, the rapid development of phylogenetic approaches has promoted a stream of studies investigating evolution of communication signals. However, comparative research has primarily focused on visual and acoustic signals, while the evolution of chemical signals remains largely unstudied. An increasing interest in understanding the evolution of chemical communication has been inspired by the realization that chemical signals underlie some of the major interaction channels in a wide range of organisms. In lizards, in particular, chemosignals play paramount roles in female choice and male–male competition, and during community assembly and speciation. Here, using phylogenetic macro‐evolutionary modeling, we show for the very first time that multiple compounds of scents for communication in lizards have diversified following highly different evolutionary speeds and trajectories. Our results suggest that cholesterol, α‐tocopherol, and cholesta‐5,7‐dien‐3‐ol have been subject to stabilizing selection (Ornstein–Uhlenbeck model), whereas the remaining compounds are better described by Brownian motion modes of evolution. Additionally, the diversification of the individual compounds has accumulated substantial relative disparity over time. Thus, our study reveals that the chemical components of lizard chemosignals have proliferated across different species following compound‐specific directions.     

Distant non-chemical communication in various biological systems.

Communication is a natural ability of all living systems. It is very likely that various types of communication were evolved during evolution. While the communication by means of chemicals, direct contact or via organs of sense is under intensive study for a long time, alternative ways of interaction are still considered debatable, This review covers the topic of physically mediated communication in various biological systems.     

How phylogeny and foraging ecology drive the level of chemosensory exploration in lizards and snakes

The chemical senses are crucial for squamates (lizards and snakes). The extent to which squamates utilize their chemosensory system, however, varies greatly among taxa and species’ foraging strategies, and played an influential role in squamate evolution. In lizards, ‘Scleroglossa’ evolved a state where species use chemical cues to search for food (active foragers), whereas ‘Iguania’ retained the use of vision to hunt prey (ambush foragers). However, such strict dichotomy is flawed as shifts in foraging modes have occurred in all clades. Here, we attempted to disentangle effects of foraging ecology from phylogenetic trait conservatism as leading cause of the disparity in chemosensory investment among squamates. To do so, we used species’ tongue‐flick rate (TFR) in the absence of ecological relevant chemical stimuli as a proxy for its fundamental level of chemosensory investigation, that is baseline TFR. Based on literature data of nearly 100 species and using phylogenetic comparative methods, we tested whether and how foraging mode and diet affect baseline TFR. Our results show that baseline TFR is higher in active than ambush foragers. Although baseline TFRs appear phylogenetically stable in some lizard taxa, that is a consequence of concordant stability of foraging mode: when foraging mode shifts within taxa, so does baseline TFR. Also, baseline TFR is a good predictor of prey chemical discriminatory ability, as we established a strong positive relationship between baseline TFR and TFR in response to prey. Baseline TFR is unrelated to diet. Essentially, foraging mode, not phylogenetic relatedness, drives convergent evolution of similar levels of squamate chemosensory investigation.     

Molecular complexes of amino acids with porphyrins as possible precursors of pigment-protein systems

The present communication gives experimental results of the studies of catalytic and photochemical properties of peptide-like compounds containing metalloporphyrins (hemoproteinoids and molecular complexes obtained through adsorption of porphyrins and amino acids on volcanic ash). The data suggest that molecular complexes of amino acids with porphyrins could have evolved in the course of chemical evolution and were intermediated between abiogenically synthesized molecules of amino acids and porphyrins and pigment-protein systems of living organisms.     

Foragers of the stingless bee Plebeia droryana inform nestmates about the direction,but not the distance to food sources

1. The tropical stingless bees have evolved intricate communication systems to recruit nestmates to food locations. Some species are able to accurately communicate the location of food, whereas others simply announce the presence of food in the environment.
2. Plebeia droryana is a tiny Neotropical stingless bee that, until recently, was thought to use a solitary foraging strategy, that is without the use of a recruitment communication system. However, recent research has indicated that P. droryana might be able to recruit nestmates to specific food source locations.
3. We tested this by studying whether foragers can guide nestmates in the direction and the distance of artificial feeders placed in the vicinity of the colony. We trained bees to a scented sucrose solution feeder at 10 m and placed different feeders either in different directions (experiment 1) or in different distances (experiment 2). We found that P. droryana directs newcomers in the right direction, but distance information does not seem to be communicated.
4. Moreover, we then tested whether newcomers use chemical and visual cues originating from nestmates foraging at the food source, but found no evidence for the use of these social cues provided by conspecifics.
5. The potential mechanism that P. droryana may use to orient recruits toward the food source, however, remains unknown and requires further study.

     

A sophisticated,modular communication contributes to ecological dominance in the invasive ant <Emphasis Type="Italic">Anoplolepis gracilipes</Emphasis>

The ecological success of ants is founded on cooperative behaviour and a well functioning communication. Particularly invasive ants are able to act highly cooperatively, out-compete other species, and become ecologically dominant. Since ant communication is to a large extent chemical, we investigated the pheromone functions involved in foraging and alarm behaviour of the invasive tropical formicine Anoplolepis gracilipes. Our results suggest that long-lasting orientation cues are located in hindguts, while Dufour glands contain short-term attractants that trigger an effective recruitment. Poison gland effects were intermediate between hindgut and Dufour gland in terms of orientation, attraction and longevity. In contrast to the other pheromone sources, mandibular glands have a repellent effect and are most likely involved in alarm behaviour. Taken together, the pheromone glands of A. gracilipes contain functionally distinct signals with considerable differences in persistence. In this respect, its communication is exceptional in formicine ants. A strikingly similar communication system was previously detected in Paratrechina longicornis, another opportunistic and invasive formicine ant. Based on these similarities and the differences compared to non-invasive formicine ants, we discuss the role of chemical signals for the coordination of efficient foraging. We conclude that a sophisticated communication system can contribute significantly to ecological dominance and invasive success, in concert with other well known traits.     

Memory and chemical communication in the orientation of two mass-recruiting ant species

Summary The relative contribution of visual and chemical components in the orientation ofLasius niger andIridomyrmex humilis (Argentine ant) workers during mass recruitment to newly discovered food sources is analyzed over short time intervals. While both species orient in response to the trail pheromone, a large number ofL. niger foragers rapidly switch to a more individual orientation, based on their memory of environmental cues.I. humilis workers, on the other hand, predominantly use collective chemical cues. The effect of the number of reinforcements on visual learning and its interference with chemical communication show that olfactory cues always prevail in the Argentine ant. InL. niger, the proportion of ants orienting to visual cues is independent of the trail concentration. Detailed observations of the trail-laying behavior of individually marked foragers show that nearly all theI. humilis workers initially lay a trail, whereas only half theL. niger foragers do so. This proportion decreases considerably with the number of trips performed byL. niger workers, while remaining constant for the Argentine ants. These results are interpreted with respect to the species' behavioral ecology.     

Evolutionary relationships among food habit, loss of flight, and reproductive traits: life-history evolution in the Silphinae (Coleoptera: Silphidae)

Flightlessness in insects is generally thought to have evolved due to changes in habitat environment or habitat isolation. Loss of flight may have changed reproductive traits in insects, but very few attempts have been made to assess evolutionary relationships between flight and reproductive traits in a group of related species. We elucidated the evolutionary history of flight loss and its relationship to evolution in food habit, relative reproductive investment, and egg size in the Silphinae (Coleoptera: Silphidae). Most flight-capable species in this group feed primarily on vertebrate carcasses, whereas flightless or flight-dimorphic species feed primarily on soil invertebrates. Ancestral state reconstruction based on our newly constructed molecular phylogenetic tree implied that flight muscle degeneration occurred twice in association with food habit changes from necrophagy to predatory, suggesting that flight loss could evolve independently from changes in the environmental circumstances per se. We found that total egg production increased with flight loss. We also found that egg size increased with decreased egg number following food habit changes in the lineage leading to predaceous species, suggesting that selection for larger larvae intensified with the food habit change. This correlated evolution has shaped diverse life-history patterns among extant species of Silphinae.     

Evolution of epiphytes in Davalliaceae and related ferns

The evolution of epiphytes in Davalliaceae was investigated by field observations and molecular phylogenetic analyses. Field studies revealed that in Davalliaceae and related ferns, epiphytes in a broad sense are classified into climber, secondary hemi-epiphyte, and obligate epiphyte, based on combinations of the places (ground vs. tree) of inferred spore germination and sporophyte growth. Some species of Davalliaceae have multiple life forms, i.e. secondary hemi-epiphyte and obligate epiphyte, whereas others are obligate epiphytes. Phylogenetic trees obtained from rbcL and accD gene sequences supported that secondary hemi-epiphytic Oleandra is sister to the epiphytic Davalliaceae and polygrammoid ferns. Analyses of life form evolution based on the phylogenetic relationships suggested that obligate epiphytes of the Davalliaceae and polygrammoid ferns evolved from secondary hemi-epiphytes, or less likely from climbers. We hypothesized a scenario for the evolution of life forms in Davalliaceae and related groups that involves successive changes in rhizome habit, root function, and germination place. Rhizome dorsiventrality and scale morphology, shared by climbers, secondary hemi-epiphytes, and obligate epiphytes examined, may be other innovations for the ferns to have evolved into epiphytes.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 495–510.     

Mathematical models for some types of chemical information systems

Ant species on a high evolutionary level have evolved chemical recruitment systems such as mass recruitment or quality recruitment. The recruitment process from the nest to a food source may be damped by crowding effects at the source. For four patterns of behavior (mass/quality recruitment; with/without damping) we study mathematical models for the time development of the quantity of food at the source. Each of the models can be reduced to a second order time-delayed differential equation which will be studied in the equivalent form of a first order (nonlinear) functional differential equation. We discuss the complete exploitation of a given source. In case of mass recruitment there possibly remains a threshold quantity of food not worth exploiting. However, every source will be exploited completely (in finite time) provided that the volatility of the trail pheromone is small compared with the exploitation activities of the colony and the distance from the nest to the source. In addition, for the damped models the capacity of the crowded source must be large compared with the initial quantity of food offered. The efficiency of the exploitation activities of some species allows conclusions on their evolutionary development.     

Odorant receptor phylogeny confirms conserved channels for sex pheromone and host plant signals in tortricid moths

The search for mates and food is mediated by volatile chemicals. Insects sense food odorants and sex pheromones through odorant receptors (ORs) and pheromone receptors (PRs), which are expressed in olfactory sensory neurons. Molecular phylogenetics of ORs, informed by behavioral and functional data, generates sound hypotheses for the identification of semiochemicals driving olfactory behavior. Studying orthologous receptors and their ligands across taxa affords insights into the role of chemical communication in reproductive isolation and phylogenetic divergence. The female sex pheromone of green budworm moth Hedya nubiferana (Lepidoptera, Totricidae) is a blend of two unsaturated acetates, only a blend of both elicits male attraction. Females produce in addition codlemone, which is the sex pheromone of another tortricid, codling moth Cydia pomonella. Codlemone also attracts green budworm moth males. Concomitantly, green budworm and codling moth males are attracted to the host plant volatile pear ester. A congruent behavioral response to the same pheromone and plant volatile in two tortricid species suggests co‐occurrence of dedicated olfactory channels. In codling moth, one PR is tuned to both compounds, the sex pheromone codlemone and the plant volatile pear ester. Our phylogenetic analysis finds that green budworm moth expresses an orthologous PR gene. Shared ancestry, and high levels of amino acid identity and sequence similarity, in codling and green budworm moth PRs offer an explanation for parallel attraction of both species to the same compounds. A conserved olfactory channel for a sex pheromone and a host plant volatile substantiates the alliance of social and habitat signals in insect chemical communication. Field attraction assays confirm that in silico investigations of ORs afford powerful predictions for an efficient identification of behavior‐modifying semiochemicals, for an improved understanding of the mechanisms of host plant attraction in insect herbivores and for the further development of sustainable insect control.     

Minimum conflict: a divide-and-conquer approach to phylogeny estimation.

MOTIVATION: Fast and reliable phylogeny estimation is rapidly gaining importance as more and more genomic sequence information is becoming available, and the study of the evolution of genes and genomes accelerates our understanding in biology and medicine alike. Branch attraction phenomena due to unequal amounts of evolutionary change in different parts of the phylogeny are one major problem for current methods, placing the species that evolved fast in one part of the phylogenetic tree, and the species that evolved slowly in the other. RESULTS: We describe a way to avoid the artifactual attraction of species that evolved slowly, by detecting shared old character states using a calibrated comparison with an outgroup. The corresponding focus on shared novel character states yields a fast and transparent phylogeny estimation algorithm, by application of the divide-and-conquer principle, and heuristic search: shared novelties give evidence of the exclusive common heritage (monophyly) of a subset of the species. They indicate conflict in a split of all species considered, if the split tears them apart. Only the split at the root of the phylogenetic tree cannot have such conflict. Therefore, we can work top-down, from the root to the leaves, by heuristically searching for a minimum-conflict split, and tackling the resulting two subsets in the same way. The algorithm, called "minimum conflict phylogeny estimation" (MCOPE), has been validated successfully using both natural and artificial data. In particular, we reanalyze published trees, yielding more plausible phylogenies, and we analyze small "undisputed" trees on the basis of alignments considering structural homology. AVAILABILITY: MCOPEis available via http://bibiserv.techfak.uni-bielefeld.de/mcope/. CONTACT: fuellen@alum.mit.edu     

E value cutoff and eukaryotic genome content phylogenetics

Genome content analysis has been used as a source of phylogenetic information in large prokaryotic tree of life studies. Recently the sequencing of many eukaryotic genomes has allowed for the similar use of genome content analysis for these organisms too. In this communication we examine the utility of genome content analysis for recovering phylogenetic patterns in several eukaryotic groups. By constructing multiple matrices using different e value cutoffs we examine the dynamics of altering the e value cutoff on five eukaryotic genome data sets. Our analysis indicates that the e value cutoff that is used as a criterion in the construction of the genome content matrix is a critical factor in both the accuracy and information content of the analysis. Strikingly, genome content by itself is not a reliable or accurate source of characters for phylogenetic analysis of the taxa in the five data sets we analyzed. We discuss two problems--small genome attraction and genome duplications as being involved in the rather poor performance of genome content data in recovering eukaryotic phylogeny.     

Reasons to be fussy about cultural evolution

This discussion paper responds to two recent articles in Biology and Philosophy that raise similar objections to cultural attraction theory, a research trend in cultural evolution putting special emphasis on the fact that human minds create and transform their culture. Both papers are sympathetic to this idea, yet both also regret a lack of consilience with Boyd, Richerson and Henrich’s models of cultural evolution. I explain why cultural attraction theorists propose a different view on three points of concern for our critics. I start by detailing the claim that cultural transmission relies not chiefly on imitation or teaching, but on cognitive mechanisms like argumentation, ostensive communication, or selective trust, whose evolved or habitual function may not be the faithful reproduction of ideas or behaviours. Second, I explain why the distinction between context biases and content biases might not always be the best way to capture the interactions between culture and cognition. Lastly, I show that cultural attraction models cannot be reduced to a model of guided variation, which posits a clear separation between individual and social learning processes. With cultural attraction, the same cognitive mechanisms underlie both innovation and the preservation of traditions.     

Genomic insights into mediator lipidomics

G protein-coupled receptors (GPCR) are used ubiquitously and widely for signal transduction across the plasma membrane. The ligands for GPCRs are structurally diverse and include peptides, odorants, photon, ions and lipids. It is thought that GPCRs evolved by gene duplication and mutational events that diversified the ligand binding and signaling properties, thereby resulting in paralogues in various organisms. Genomic sequencing efforts of various organisms indicate that GPCRs evolved very early in evolution; for example, unicellular eukaryotes use GPCRs for mating, differentiation and sporulation responses and prokarotes utilize these receptors for phototransduction, as exemplified by the bacteriorhodopsin, a photon sensor. Many GPCRs fall into subfamilies, usually determined by structural similarity to their ligands. Bioactive lipids such as lysophospholipids, eicosanoids, ether lipids and endocannabinoids, which are produced widely in evolution, also signal through GPCRs. Thus, distinct subfamilies of bioactive lipid GPCRs, such as prostanoid receptors, lysophosphatidic, sphingosine 1-phosphate, leukotrienes, hydroxy fatty acids, endocannabinoids and ether lipids exist in the mammalian genome. With the increasing availability of genomic information throughout the phylogenetic tree, orthologues of bioactive lipid receptors are found in the genomes of vertebrates and chordates but not in worms, flies or other lower organisms. This is in contrast to GPCRs for biogenic amines and polypeptide growth factors, which are conserved in invertebrates as well. Thus, it appears that with the evolution of chordates, lipids may have acquired novel roles in cell-cell communication events via GPCRs. This hypothesis will be discussed using the prostanoid and lysophospholipid signaling systems. Since such bioactive lipids play critical roles in immune, vascular and nervous systems, this suggests that lipid metabolite signaling via the GPCRs co-evolved with the development of sophisticated vascular, immune and nervous systems in chordates and vertebrates.