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Caste and sex differences in cold-hardiness in the social wasps,Polistes annularis andP. exclamans (Hymenoptera: Vespidae)
Abstract
Elevated fructose, glucose and trehalose levels were found inPolistes exclamans andP. annularis after exposure to cold. Glycerol was found only after extensive exposure to cold or in mid-winter. InP. exclamans mean supercooling points (SCP) decreased to a low of −12.9° C in February. InP. annularis SCP were never below −6.8° C in the field, but laboratory acclimation at +5° C resulted in SCP of −10.7° C. Freezing was lethal to adultPolistes under all circumstances.
Workers and future queens were separated on the basis of the appearance of their fat bodies. ForP. exclamans, only 17 % of the future queens died during 15 days at +5° C (N=29) while 76 % of the workers died during identical cold exposure (N=45). The surviving future queens had elevated cryoprotectant levels consisting mainly of fructose in their hemolymph, while the few workers that survived did not. These experiments indicate that there are physiological differences between workers and future queens inPolistes collected in autumn and that fat body appearance determined using non-invasive techniques is a reliable indicator of caste. Males were similar to future queens in their response to cold indicating that autumn mating activity may extend into winter.
... df = 1, 215 P = 0.002) with heavier, larger females with fat bodies evoking a higher antennation response ( By contrast, hornets like V. tropica and V. analis, show an overlap of caste sizes (Matsuura & 231 Yamane 1990). Also in V. velutina nigrithorax, female caste is hard to recognize (Pérez-de-Heredia 232 et al. 2017), however, as in other temperate social wasps (Spradberry 1973;Strassmann et al 1984; 233 O'Donnell 1998;Toth et al. 2009;Perrard et al. 2012) reproductive gynes, that are the only females 234 surviving winter, are usually bigger and show more abundant fat bodies, whereas smaller workers, 235 that do not overwinter, have very scarce or absent fat bodies. Female body size, weight and fat 236 storage appear therefore as reliable indicators of female caste ( Strassmann et al 1984; Hunt et al. 237 2007 Hunt et al. 237 , 2010 Cervo et al. 2008;Toth et al. 2009). ...
... Also in V. velutina nigrithorax, female caste is hard to recognize (Pérez-de-Heredia 232 et al. 2017), however, as in other temperate social wasps (Spradberry 1973;Strassmann et al 1984; 233 O'Donnell 1998;Toth et al. 2009;Perrard et al. 2012) reproductive gynes, that are the only females 234 surviving winter, are usually bigger and show more abundant fat bodies, whereas smaller workers, 235 that do not overwinter, have very scarce or absent fat bodies. Female body size, weight and fat 236 storage appear therefore as reliable indicators of female caste ( Strassmann et al 1984; Hunt et al. 237 2007 Hunt et al. 237 , 2010 Cervo et al. 2008;Toth et al. 2009). Thus, the observed male preference for bigger 238 heavier females, with more abundant fat storages, might due to the fact that such females are the 239 more likely to survive the winter diapause and found a new colony the following season, as in other 240 ...
... Also in V. velutina nigrithorax, female caste is hard to recognize (Pérez-de-HerediaO'Donnell 1998; Toth et al. 2009;Perrard et al. 2012) reproductive gynes, that are the only females 234 surviving winter, are usually bigger and show more abundant fat bodies, whereas smaller workers, 235 that do not overwinter, have very scarce or absent fat bodies. Female body size, weight and fat 236 storage appear therefore as reliable indicators of female caste ( Strassmann et al 1984;Hunt et al. 237 2007Hunt et al. 237 , 2010Cervo et al. 2008;Toth et al. 2009). Thus, the observed male preference for bigger 238 heavier females, with more abundant fat storages, might due to the fact that such females are the 239 more likely to survive the winter diapause and found a new colony the following season, as in other 240 ...
In the early stage of the invasion process, alien species may face costs linked to pioneer effect due to genetic bottleneck, drift and the consequential inbreeding depression. Thus, introduced species that show an immediate exponential growth in their invasive population should have some mechanisms to reduce such costs minimising the chance of inbreeding or allowing them to cope with them. The yellow-legged hornet Vespa velutina nigrithorax has been spotted in France in 2004; since then, the species has been invading Europe with a relentless pace. In their native range, males and reproductive females of a Chinese non-invasive sub-species of V. velutina seem to leave their nests to search for unrelated partners. However, previous studies showed a low genetic diversity and a high rate of diploid males in colonies of the invasive population, suggesting that mating could occur inside nests, where males should be able to discriminate between reproductive gynes and sterile workers. Here, we used laboratory behavioural assays to investigate the mating preferences of yellow-legged hornet males from the recent invasive population in Italy. We assessed the importance of nestmateship and female morpho-physiological traits, likely indicators of caste, in determining male attraction towards potential partners. Our results demonstrate that males are more attracted to bigger females with more abundant fat storage, good indicators of female reproductive caste in wasps, regardless of nestmateship. Our findings represent a first step in understanding the reproductive biology of V. velutina nigrithorax in its invasive range, providing a framework for future research in the field to prevent or reduce the species expansion.
... In Polistes wasps, workers are not distinguishable from the reproductives by any external morphological difference. However, foraging effort and abundance of fat bodies can be used as behavioural and physiological indicators of worker versus potential queen status Gamboa, 1983, 1987;Gamboa et al., 1990;O'Donnell, 1998b;Eickwort, 1969;Strassmann et al., 1984;Karsai and Hunt, 2002). Thus, we compared physiological and behavioural traits of the first female offspring from non-parasitised colonies to test the prediction that the first female offspring emerging in cold areas with high parasite prevalence had more developed, gyne-like fat bodies and exhibited lower foraging effort than the first female offspring produced in warm areas with low parasite prevalence. ...
... In the laboratory, for each field-collected female, we measured, using callipers, the maximum head width (the distance between the compound eyes) as an indicator of body size (Seppä et al., 2002). We inspected the condition of fat bodies, as an indicator of caste status (O'Donnell, 1998a;Eickwort 1969;Strassmann et al., 1984;Karsai and Hunt, 2002). To do so, we removed the digestive tracts, ovaries, spermathecae and venom glands of the females by grasping the terminal segment with forceps and pulling to extract the attached viscera. ...
... In contrast, the length of the nesting season is similar across populations and therefore it cannot be a cause of divergence in offspring physiology among populations. Our field findings confirm laboratory experiments on P. foederatus (Turillazzi and Conte, 1981) which indicated that cold temperatures favour better developed fat bodies, a gyne-like trait of the offspring physiology (Eickwort, 1969;Strassmann et al., 1984;Karsai and Hunt, 2002). In contrast, the higher temperature climate regime of the Apennine site favoured the accumulation of reduced amount of fat bodies and triggered the expression of worker-like physiological traits in the first female offspring. ...
In primitively eusocial insects, caste expression is flexible. Even though Polistes species are well known to show social trait variation (e.g., worker vs. gyne) depending on ecological context, loss of worker
caste in some populations of a eusocial, worker-containing species has never been documented. We report first data on geographic
variation in caste expression in Polistes biglumis. We compared physiological and behavioural traits of the first female offspring from four populations that experience different
climatic conditions and social parasite prevalence. We demonstrated that the first female offspring to emerge in cold areas
with high parasite prevalence had more abundant, gyne-like fat bodies and exhibited lower foraging effort, in comparison to
the first female offspring produced in warm areas with low parasite prevalence. Thus, the populations under severe environmental
conditions produced a totipotent female offspring and suppressed worker production, whereas the population living in less
extreme environmental conditions produced worker-like females as first female offspring and gyne-like females as offspring
that emerged later. The existence of mixed social strategies among populations of primitively eusocial species could have
important consequences for the study of social evolution, shedding light on the sequence of steps by which populations evolve
between the extremes of solitary state and eusocial state.
... Here we determined if natural differences in larval experience between workers and reproductives are sufficient to drive differences in nutrient intake and processing in Polistes. We collected individuals from field colonies after they had spun a cap to their cell, entering the prepupal stage, and reared them in an environment devoid of any cues experienced after eclosion, including photoperiod, temperature and social cues (other larvae and adults) that have been shown to affect adult physiology and behavior [14,18,20,37,38]. Thus, all individuals experienced all of the normal larval cues prior to collection but experienced the same minimal cues during pupation and upon eclosion. ...
... Other studies demonstrated stark differences in behavior [14] and nutrient levels when individuals were exposed to different environmental cues [14,29]. On the other hand, studies with reduced environmental differences noted that females became more similar over time [38,39]. The fact that all females in this study ended up with similar nutrient levels despite likely having different nutrient levels as larvae [28] adds additional support to the need for environmental cues upon eclosion to reinforce the caste physiological and behavioral trajectories. ...
There is growing evidence that paper wasps’ (Polistes’) fate as workers or reproductive females (gynes) is affected by cues that exist at the larval stage and during eclosion. The nutritional requirements for workers and gynes are different early in their adult lives. Males are short-lived and have different nutritional needs than females. To determine the relative importance of larval and adult cues, we reared Polistes metricus individuals from prepupae to adults isolated from known environmental cues shown to affect caste differentiation. Individuals were given access to two foods with different ratios of protein and carbohydrates. Levels of protein, amino acids, carbohydrates and lipids were measured after the feeding trials. If larval experience drove feeding behavior in adults, we expected to see differences in protein and carbohydrate intake as well as differences in nutrient levels. Females showed no differences in feeding or nutrient levels. Males had lower levels of protein and amino acids than females but had similar feeding results to females.
... Like glycerol, trehalose decreases the supercooling point and protects cells from freezing (Storey & Storey, 1997;Lee, Chang, & Kim, 2002). Similarly, in paper wasps (Polistes exclamans and P. annularis), workers synthesise high levels of trehalose in the haemolymph after prolonged exposure to cold stress (Strassmann et al., 1984). Temperature can also affect the fluidity of cell membranes: heat stress makes membranes more fluid, while cold stress stiffens them. ...
... Molecular and physiological adaptations for coping with extreme thermal conditions have been well conserved over the course of evolution and are seen in organisms ranging from bacteria to humans (Neven, 2000;Evgen'ev, Garbuz, & Zatsepina, 2014). Solitary and social insects employ the same molecular mechanisms to enhance cold tolerance: increased metabolic rates, synthesis of cryoprotectants, and changes in membrane composition (Strassmann et al., 1984;Zachariassen, 1985;Block, 1990;Roberts & Harrison, 1998;Sinclair et al., 2003;Lacey, Lenz, & Evans, 2010;Kadochová & Frouz, 2014). Furthermore, species occupying similar habitats have evolved the same gene expression dynamics in response to thermal stress. ...
Thermal stress is a major driver of population declines and extinctions. Shifts in thermal regimes create new environmental conditions, leading to trait adaptation, population migration, and/or species extinction. Extensive research has examined thermal adaptations in terrestrial arthropods. However, little is known about social insects, despite their major role in ecosystems. It is only within the last few years that the adaptations of social insects to thermal stress have received attention. Herein, we discuss what is currently known about thermal tolerance and thermal adaptation in social insects – namely ants, termites, social bees, and social wasps. We describe the behavioural, morphological, physiological, and molecular adaptations that social insects have evolved to cope with thermal stress. We examine individual and collective responses to both temporary and persistent changes in thermal conditions and explore the extent to which individuals can exploit genetic variability to acclimatise. Finally, we consider the costs and benefits of sociality in the face of thermal stress, and we propose some future research directions that should advance our knowledge of individual and collective thermal adaptations in social insects.
... By contrast, hornets like V. tropica and V. analis show an overlap of caste sizes (Matsuura & Yamane 1990). Also in V. velutina nigrithorax, female caste is hard to recognise (Pérez-de-Heredia et al. 2017), however, as in other temperate social wasps (Spradberry 1973;Strassmann et al. 1984;O'Donnell 1998;Toth et al. 2009;Perrard et al. 2012) reproductive gynes, that are the only females surviving winter, are usually bigger and show more abundant fat bodies, whereas smaller workers, that do not overwinter, have very scarce or absent fat bodies. Female body size, weight and fat storage appear therefore as reliable indicators of female caste (Strassmann et al. 1984;Hunt et al. 2007Hunt et al. , 2010Cervo et al. 2008;Toth et al. 2009). ...
... Also in V. velutina nigrithorax, female caste is hard to recognise (Pérez-de-Heredia et al. 2017), however, as in other temperate social wasps (Spradberry 1973;Strassmann et al. 1984;O'Donnell 1998;Toth et al. 2009;Perrard et al. 2012) reproductive gynes, that are the only females surviving winter, are usually bigger and show more abundant fat bodies, whereas smaller workers, that do not overwinter, have very scarce or absent fat bodies. Female body size, weight and fat storage appear therefore as reliable indicators of female caste (Strassmann et al. 1984;Hunt et al. 2007Hunt et al. , 2010Cervo et al. 2008;Toth et al. 2009). Thus, the observed male preference for bigger heavier females, with more abundant fat storages, might due to the fact that such females are the more likely to survive the winter diapause and found a new colony the following season, as in other Vespidae species (Hunt et al. 2007(Hunt et al. , 2010; Cervo et al. 2008), and we may expect males to have evolved accurate systems to detect the most suitable partners. ...
Due to its huge invasion potential and specialization in honeybee predation, the invasive hornet Vespa velutina nigrithorax represents a high-concern species under both an ecological and economical perspective. In light of the development of specific odorant attractants to be used in sustainable control strategies, we carried out both behavioural assays and chemical analyses to investigate the possibility that, in the invasive population of V. velutina nigrithorax, reproductive females emit volatile pheromones to attract males, as demonstrated in a Chinese non-invasive population. We focused on the secretions produced by sternal and venom glands; because of the volatility and complexity of their composition, both of them could potentially allow an attraction and a species-specific response, decreasing therefore non-target species by-catches. Results of chemical analyses and behavioural assays showed that venom volatiles, although population-specific, are unlikely candidates as male attractants since they do not differ in composition or in quantity between reproductive females and workers and do not attract males. Conversely, sternal gland secretion differs between female castes for the presence of some ketoacids exclusive of gynes already reported as sex pheromones for the non-invasive subspecies V. velutina auraria. Despite such a difference, males are attracted by the sternal gland secretion of both workers and gynes. These results provide a first step to understand the reproductive biology of V. velutina nigrithorax in its invasive range and to develop effective and sustainable management strategies for the species.
... The potential queens of the next generation (often called gynes) are characterized by diapausing in temperate paper wasps; therefore, the above question on caste-fate determination can be addressed based on when the female decides to enter diapause. The gynes store lipids for diapausing and refrain from developing ovaries, whereas nondiapausing individuals develop ovaries and refrain from storing lipids, that is, they have more and larger oocytes and smaller lipid stores than those of the gynes (Eickwort 1969;Haggard and Gamboa 1980;Strassmann et al. 1984;Toth et al. 2009). These differences are assumed to be more distinct when sufficient food is available and social interactions are not present. ...
... After the 2-week rearing period, each female was dissected to determine whether she had mature eggs, and then, the dry weight of lipids in the abdomen (strictly speaking, the gaster) was measured using the method described by Tibbetts et al. (2011). An increase in lipid stores indicates that a wasp is preparing for diapause, whereas egg maturation indicates that the wasp will refrain from diapausing (Eickwort 1969;Haggard and Gamboa 1980;Strassmann et al. 1984;Toth et al. 2009). Furthermore, female adults collected in mid-November and late December had no mature eggs, but they had many immature eggs of which some were longer than half the length of mature eggs (H. ...
Independent-founding paper wasps constitute a major group of primitively eusocial insects, and when caste-fate determination occurs in temperate species of these wasps, particularly regarding whether it occurs before or after emergence, remains unclear. No critical morphological differences occur between potential queens of the next generation (often called gynes) and workers in primitively eusocial insects. The gynes of temperate species are characterized by diapausing, and the nutrients available during the larval stage have often been believed to determine caste fate. Short days usually induce diapause in temperate nonsocial insects, although few investigations of the effects of day length on caste-fate determination in paper wasps have been conducted. By exposing individuals to different combinations of short and long days during the immature and adult stages, we show for the first time that short days during the adult stage (but not during the immature stage) facilitated caste-fate determination toward gynes in a paper wasp. Moreover, the decision to diapause partly depended on changes in the photoperiod during the pupal and adult stages. The size of the adult also affected caste-fate determination, with diapause more likely to occur in large adults, but this size effect did not occur when individuals were exposed to many short days during the pupal stage. In addition, all adults except for a small proportion of smaller individuals prepared for diapause under short days. These findings suggest that the photoperiod is a higher priority cue than adult size.
... These results suggest that overwintering bees have a large shut down in the production of proteins related to cellular and muscular structural maintenance, in favor of a large, concomitant shift to the production of proteins related to lipid storage and metabolism. Greatly increased lipid stores have been proposed to be an essential adaptation for overwintering, especially in adult Hymenoptera (Strassmann et al. 1984;Toth et al. 2009); thus, our transcriptional data agree well with physiological studies on increased fat body size in overwintering adult bees and wasps (Wasielewski et al. 2014). However, our transcriptome data are from brains, not fat bodies, and therefore suggest that metabolic shifts for overwintering are not only occurring in fat bodies but are also evident in neural tissues. ...
... In this study, we found GO enrichment for lipid metabolism (Table S3; Figure 3). Many ecological and physiological studies have identified lipid storage and metabolism as a necessity for insect survival during overwintering periods and exposure to cold temperatures (Toth et al. 2009;Strassmann et al. 1984;Wasielewski et al. 2014). However, to our knowledge, there are few studies that have found significant overwintering-related differential expression associated with lipid metabolic processes. ...
Genome-wide overwintering gene expression studies in bees are of critical importance to understand their survival, life cycles, and fitness. In this study, we use RNA sequencing to characterize the genes and gene functions associated with overwintering adult females compared with active season females for the small carpenter bee, Ceratina calcarata. We found extensive changes in gene expression associated with overwintering, including an underrepresentation of genes related to muscle fibers and an overrepresentation of genes related to lipid metabolic processes. These data suggest inactive, overwintering bees invest heavily in the production of proteins related to fat storage and divest transcriptional activity away from cellular and muscular structural processes. This study provides the first characterization of overwintering gene expression as important baseline data of a major life history event relevant to survival and health for a wild bee pollinator.
... These are the workers. Gynes emerge following the workers and they do not lay eggs in the year in which they eclose from pupation but instead enter a phase of physiological diapause [13,15,16] and behavioral quiescence that is marked by cold hardiness [17][18][19] during the unfavorable season of the annual cycle. Gynes become foundresses of the following year. ...
... Contrasts of only workers and gynes show analogous differences. Gynes differ from workers in that they have abundant white abdominal fat, whereas workers have scant yellow abdominal fat [19,24]. Gyne-destined larvae accumulate larger lipid stores than workerdestined larvae [25]. ...
The distinction between worker and reproductive castes of social insects is receiving increased attention from a developmental rather than adaptive perspective. In the wasp genus Polistes, colonies are founded by one or more females, and the female offspring that emerge in that colony are either non-reproducing workers or future reproductives of the following generation (gynes). A growing number of studies now indicate that workers emerge
with activated reproductive physiology, whereas the future reproductive gynes do not. Low nourishment levels for larvae during the worker-rearing phase of the colony cycle and higher nourishment levels for larvae when gynes are reared are now strongly suspected of playing a major role in this difference.
Here, we present the results of a laboratory rearing experiment in which Polistes metricus single foundresses were held in environmental conditions with a higher level of control than in any previously published study, and the amount of protein nourishment made available to feed larvae was the only input variable. Three experimental feeding treatments were tested: restricted, unrestricted, and hand-supplemented. Analysis ofmultiple response variables shows that wasps reared on restricted protein nourishment, which would be the case for
wasps reared in field conditions that subsequently become workers, tend toward trait values that characterize active reproductive physiology. Wasps reared on unrestricted and hand supplemented protein, which replicates higher feeding levels for larvae in field conditions that subsequently become gynes, tend toward trait values that characterize inactive reproductive physiology. Although the experiment was not designed to test for worker behavior per se, our results further implicate activated reproductive physiology as a developmental response to
low larval nourishment as a fundamental aspect of worker behavior in Polistes.
... Here we examine the caste system of such a species: Polistes exclamans Viereck, in Houston, Texas. It is a species of social wasps with no morphological castes (Eickwort, 1969;Strassmann et al., 1984). Colonies experience frequent queen turnover and a high degree of failure due to parasitisation, predation and high worker mortality (Strassman, 1981;Strassman & Meyer, 1983;Strassmann, 1985a), making it difficult to predict when the end of the nesting cycle will arrive. ...
... As in other species of the genus, P. exclamans queens, workers and the non-working females (henceforth called gynes) that will mate and overwinter to start new nests in the spring, are distinguished by their behaviour - (West Eberhard, 1969;Strassmann & Meyer, 1983), by the relative development of the fat body and ovaries (Eickwort, 1969;Haggard & Gamboa, 1980;Turillazzi et al., 1982;Strassmann et al., 1984), by the ability of gynes to survive longer than workers when exposed to cold temperatures (Strassman et al., 1984;Gervet et al., 1986; C. R. Solis, unpublished observation). Strassmann et a]. ...
In social insect colonies the sterile individuals that assume the worker role realize their reproductive potential through working and rearing the queen's brood. We have examined the role of the presence of brood in the nest as a determinant of caste in the social wasp Polistes exclamans Viereck. We predicted that wasps in colonies where there was no brood would behave like future queens, while wasps in colonies in which brood care was an option would behave like workers. Brood presence was manipulated by removing eggs and larvae or the whole nest from experimental colonies and leaving brood in control colonies. Ability to tolerate cold temperatures was used as an indicator of caste when comparing females emerging in experimental colonies to females emerging in control colonies. Females emerging in experimental colonies survived longer at cold temperatures than those emerging in control colonies. This indicates that females developed characteristics more typical of future queens in response to deprivation of brood. P. exclamans is characterized by small colonies whose nests are destroyed frequently. Therefore caste plasticity in adult females of P. exclamans is advantageous.
... argued that P. metricus colonies were likely to invest equally in males and females, but he did not consider physiology. Gynes are likely to be more expensive to produce than males or workers, because gynes require more body fat (Eickwort, 1969; Strassmann et al., 1984), more protein (Hunt et al., 2003) and anti-freeze compounds (Gibo, 1976; Strassmann et al., 1984 ) during their dormant period and subsequent nest founding. Protection against freezing involves the conversion of the insect's entire glycogen supply into polyols that lower the super-cooling point of water and the synthesis of large molecular weight ice nucleating proteins (Duman and Patterson, 1978; Storey, 1990). ...
... argued that P. metricus colonies were likely to invest equally in males and females, but he did not consider physiology. Gynes are likely to be more expensive to produce than males or workers, because gynes require more body fat (Eickwort, 1969; Strassmann et al., 1984), more protein (Hunt et al., 2003) and anti-freeze compounds (Gibo, 1976; Strassmann et al., 1984 ) during their dormant period and subsequent nest founding. Protection against freezing involves the conversion of the insect's entire glycogen supply into polyols that lower the super-cooling point of water and the synthesis of large molecular weight ice nucleating proteins (Duman and Patterson, 1978; Storey, 1990). ...
A field population of Polistes metricus Say near St. Louis, Missouri was
supplemented with dilute Apis mellifera honey and Trichoplusia
ni caterpillars during the entire colony development period. Offspring were collected at two times to
coincide with emergence of worker and reproductive broods. Food supplementation had no effect on nest size, the number
of worker offspring, or the size of workers. Supplemented colonies did produce more females in August but female size
was unaffected by supplementation. Supplementation had no effect on the number of males produced, but males were
slightly larger on supplemented nests. We interpret these findings in the context of social insect life history theory.
... The evidence includes apparent morphological caste dimorphism in Polistes olivaceous [22,23] and Belonogaster petiolata [24], unequivocal morphological caste dimorphism in Ropalidia galimatia [25], and two phenotypes of reproductive development in newly-emerged Ropalidia marginata [26,27,28]. Abdominal fat in adult female Polistes reared early in the colony cycle is scant and yellow, whereas abdominal fat in females reared late in the colony cycle is abundant and white [29,30,31,32]. Although ovarian development is slight in both workers and gynes, it is significantly greater in workers [32]. ...
... Lipid transport utilizes specialized lipoprotein complexes, the apolipoproteins, that stabilize the lipid components and mediate metabolism [76], thus further supporting the idea that nutrient allocation affects caste-biased larval development in Polistes. Enhanced lipid metabolism might lead to enhanced lipid depositories in gynes, helping them survive the temperate winter or tropical dry season [30,77,78]. Apolipoprotein was down-regulated in adult queens vs. workers of the tropical paper wasp P. canadensis [73]. ...
Polistes paper wasps are models for understanding conditions that may have characterized the origin of worker and queen castes and, therefore, the origin of paper wasp sociality. Polistes is "primitively eusocial" by virtue of having context-dependent caste determination and no morphological differences between castes. Even so, Polistes colonies have a temporal pattern in which most female larvae reared by the foundress become workers, and most reared by workers become future-reproductive gynes. This pattern is hypothesized to reflect development onto two pathways, which may utilize mechanisms that regulate diapause in other insects. Using expressed sequence tags (ESTs) for Polistes metricus we selected candidate genes differentially expressed in other insects in three categories: 1) diapause vs. non-diapause phenotypes and/or worker vs. queen differentiation, 2) behavioral subcastes of worker honey bees, and 3) no a priori expectation of a role in worker/gyne development. We also used a non-targeted proteomics screen to test for peptide/protein abundance differences that could reflect larval developmental divergence. We found that foundress-reared larvae (putative worker-destined) and worker-reared larvae (putative gyne-destined) differed in quantitative expression of sixteen genes, twelve of which were associated with caste and/or diapause in other insects, and they also differed in abundance of nine peptides/proteins. Some differentially-expressed genes are involved in diapause regulation in other insects, and other differentially-expressed genes and proteins are involved in the insulin signaling pathway, nutrient metabolism, and caste determination in highly social bees. Differential expression of a gene and a peptide encoding hexameric storage proteins is especially noteworthy. Although not conclusive, our results support hypotheses of 1) larval developmental pathway divergence that can lead to caste bias in adults and 2) nutritional differences as the foundation of the pathway divergence. Finally, the differential expression in Polistes larvae of genes and proteins also differentially expressed during queen vs. worker caste development in honey bees may indicate that regulatory mechanisms of caste outcomes share similarities between primitively eusocial and advanced eusocial Hymenoptera.
... FAT BODY Eickwort (25) reported qualitative differences in the amount and morphology of the fat body in female Polistes exclamans emerging in late summer. Fat body differences corresponded to behavioral differences and have since been used as an indirect indicator of caste status of temperate-zone independentfounding wasps (38,60,108). ...
... Ability to survive the winter was used as an indicator of caste; temperate Polistes spp. workers differ physiologically from gynes such that gynes are more likely to survive cold temperatures (25,102,108). P. dominulus females eclosing from nests attended by queens alone had low probability of winter survival, whereas those eclosing from nests with workers were more likely to survive (66). Lorenzi & Turillazzi (63) noted that females belonging to discrete categories with respect to fat deposition and behavior, which they classified as workers and gynes, emerged simultaneously as the first offspring produced by Polistes biglumus colonies in the alpine zone. ...
Wasps (Vespidae) exhibit a range of social complexity, from solitary living to eusocial colonies, and thus are exemplary for studies of the evolutionary origin and maintenance of social behavior in animals. Integral to the definition of eusociality is the presence of reproductive castes, group members that differ qualitatively in their ability to reproduce in a social setting. Behavioral and morphological evidence suggests that caste determination, the developmental process by which differences in fecundity are established, occurs to a large extent before adult emergence (pre-imaginally) in many species of Vespidae, in both basal and advanced taxa within the clade (Vespinae+Polistinae), which includes most eusocial species. Pre-imaginal determination has been documented in many taxa (e.g. independent-founding Polistinae) where it was not thought to occur. Correlative and experimental studies indicate that differences in nutrition during larval development are often the basis of pre-imaginal caste determination. Pre-imaginal caste determination has important implications for the roles of subfertility and manipulation by nest mates in the evolution of eusocial behavior.
... For example, the wasp Polistes exclamans, the frog Lithobates sylvaticus, and the turtle Chrysemys picta all utilize sugars (e.g. D-glucose and D-fructose) as cryoprotectants [5][6][7]. Features of metabolism are also regularly co-opted; that is, they evolve novel functions other than that which they initially evolved for. An excellent example of this involves the folate cycle of one-carbon (C1) metabolism. ...
Background
The folate cycle of one-carbon (C1) metabolism, which plays a central role in the biosynthesis of nucleotides and amino acids, demonstrates the significance of metabolic adaptation. We investigated the evolutionary history of the methylenetetrahydrofolate dehydrogenase (mTHF) gene family, one of the main drivers of the folate cycle, across life.
Results
Through comparative genomic and phylogenetic analyses, we found that several lineages of Archaea lacked domains vital for folate cycle function such as the mTHF catalytic and NAD(P)-binding domains of FolD. Within eukaryotes, the mTHF gene family diversified rapidly. For example, several duplications have been observed in lineages including the Amoebozoa, Opisthokonta, and Viridiplantae. In a common ancestor of Opisthokonta, FolD and FTHFS underwent fusion giving rise to the gene MTHFD1, possessing the domains of both genes.
Conclusions
Our evolutionary reconstruction of the mTHF gene family associated with a primary metabolic pathway reveals dynamic evolution, including gene birth-and-death, gene fusion, and potential horizontal gene transfer events and/or amino acid convergence.
... The cleptoparasites have no worker offspring Individuals emerging onto nests without larvae, therefore without stimuli that elicit allomaternal care, showed signs of active reproduction and nest construction (Judd 2018). In the laboratory, augmented nourishment increased gyne-like characteristics (Karsai and Hunt 2002;Judd et al. 2015); restricted nourishment increased larval cannibalism by foundresses (Kudô and Shirai 2012); and exposure to cold revealed physiological and survival differences between workers and gynes (Strassmann et al. 1984;Karsai and Hunt 2002). Facial patterns of Polistes dominulus from colonies reared with supplemental nourishment signaled higher aspects of quality related to dominance (Tibbetts and Curtis 2007). ...
Complex problems in evolutionary biology can be approached in two ways, top down using theoretical constructs and bottom up using empirical studies . Theoretical concepts predominate evolutionary interpretations of eusociality in a literature that is small relative to an enormous literature of natural history and basic research that is not synthesized into a conceptual whole. Here, I draw insights from this literature to show how paper wasps’ allomaternal non-reproductive worker phenotype originates in every colony cycle via confluence of multiple factors of paper wasp biology. These include behavior, development, nutrient dynamics, indirect genetic effects, sex ratio, and demography. A novel perspective on the colony cycle, based on individuals’ reproductive physiology, serves as context to examine of each of these. It will be shown that the allomaternal non-reproductive worker phenotype does not require relatedness among colony members to originate. Allomaternal care of non-relatives is frequent and can occur in at least twelve contexts. Life histories of living species as they will be presented here show that relatedness among colony members is not the target of selection in simple eusociality. However, the novel allomaternal non-reproductive worker phenotype had to be present at the ancestral origins of complex eusociality in which relatedness among colony members is essential.
... Laboratory experimental evidence suggests that in this species, males discriminate female caste and strongly prefer gynes over workers, although castrated by a parasite (Cappa et al., 2013). Because of differences in cold protective substances (e.g., fructose), most paper wasp workers do not survive the harsh winter that comes after the mating season, while gynes do (Strassmann et al., 1984;Toth et al., 2009). As a result, by discriminating female caste, males are able to direct reproductive investment in more profitable sexual partners. ...
Potential mates often exhibit strong variation in reproductive quality, so the choice for the best sexual partner is generally adaptive. However, its adaptive value diminishes in cases where potential mates are similarly fit or when mate choice is too costly, leading mate choice to be unusual or absent. “Primitively eusocial” insects have flexible castes. Workers usually behave as “helpers,” but sometimes they mate and lay fertilized eggs. Despite worker totipotence, direct reproduction is, overall, higher in queens. Males of the temperate paper wasp Polistes dominula are able to discriminate castes, preferring gynes (= future queens) over workers, thus assuring more profitable mates. To our knowledge, no study has tested this ability in neotropical paper wasps. Here, we test the prediction that in the congeneric neotropical paper wasp Polistes versicolor, male sexual preference for gynes is unusual or absent. We perform laboratory paired mating trials in which a male was introduced to either a gyne or a worker. Caste assigned was confirmed by morphophysiological analysis. As predicted, male sexual interest was similar regardless of female caste. Conducting gas chromatography analysis, we demonstrated that queens and workers have distinct cuticular hydrocarbon profiles so caste‐related cues are available. We discuss the possibility that reduced differences in direct reproductive potential between castes and high costs of caste discrimination account for the absence of mate choice for gynes in P. versicolor males despite its occurrence in P. dominula. Thus, caste discrimination by males during sexual context is not so strict in species in which workers are able to mate and lay fertilized eggs. Laboratory sexual encounters in Polistes versicolor paper wasps. A focal male was randomly introduced separately to a gyne and a worker in a small arena. No caste discrimination by males.
... The females that prepare for overwintering, i.e. store lipids, are classified as diapausing females (i.e. gynes) (Eickwort 1969;Strassmann et al. 1984;Toth et al. 2009;Yoshimura and Yamada 2018a), while those that do not are classified as nondiapausing females, including workers, replacement queens, and mid-season foundresses (Strassmann 1981;Page et al. 1989). Moreover, gynes do not develop mature ovaries before overwintering, while nondiapausing females do so before overwintering to perform oviposition under certain conditions (Haggard and Gamboa 1980;Toth et al. 2009), such as when they are dominant or leave their natal nests. ...
Whether the caste fate of social insects is determined before or after emergence is a key question for understanding the evolution of eusociality. Paper wasps are a suitable model for answering this question because there are no critical morphological differences between queens and workers in paper wasps, and these animals appear to represent an early stage of eusociality. We explored the above question by determining the effects of photoperiod during the adult stage on caste-fate determination in the paper wasp Polistes jokahamae. We collected colonies at different stages in the field and exposed emerging adults individually to long or short days. Under these isolated conditions, gyne-destined (diapausing) females were expected to exhibit large lipid stores without mature eggs, while the reverse was expected to be true for worker-destined (nondiapausing) females. The proportion of wasps with mature eggs was higher under long days in the second and subsequent broods, but not in the first brood. Lipid stores were larger among large females and under short days, and smaller for the first brood. These findings together suggest that the first brood emerges with a strong preimaginal bias toward workers (nondiapausing form), whereas the other broods emerge with no bias or an easily reversible bias. However, it is difficult to conclude whether the bias came from body size or the season of emergence. We discuss the possibility that the ancestor of paper wasps had workers with and without preimaginal bias toward becoming workers at emergence.
... Less is known about caste and environmental differences across termite species (Hu and Appel 2004;Mitchell et al. 1993;Woon et al. 2018). However, in other eusocial insects, differences in thermal tolerances were correlated to worker size (Cerdá and Retana 1997;Clémencet et al. 2010), colony size (Oyen et al. 2016;Ribeiro et al. 2012;Wendt and Verble-Pearson 2016), nest location (Baudier et al. 2015), and role (Strassmann et al. 1984) and is often explained by differences in microhabitats experienced by individuals. ...
Extrema in temperature tolerances are a selective factor contributing to variation between populations and species. The climate variability hypothesis (CVH) posits that organisms exposed to a wider range of temperatures are expected to have a wider thermal range. This pattern is common across many taxa. In this study, we investigate how social insects vary in thermal tolerance. We test if social role in termites influences tolerance to temperature maxima, and given ties between social roles and body size, whether it is a primary correlate. Our methods examined upper lethal limit (ULL) and dry weights of five termite species representing two families across four sites in Texas and Costa Rica. With the addition of previously recorded upper heat tolerances in the literature, we conclude that termites follow the CVH and upper heat tolerance is positively correlated with absolute latitude. Our results show a differentiation in heat tolerance by task (collected from foraging site versus from nest) for Nasutitermes corniger soldiers but not workers. In the remaining species, there was no ULL partitioning by caste (soldier versus worker). Body size significantly correlated with ULL with the exception of Cornitermes walkeri, an outlier in both body size and ULL. A better understanding of how termites cope with temperature is important for this essential wood decomposer in a changing climate.
... In addition to the aforementioned behavioral differences, Polistes workers and gynes differ in nutrient storage and physiology. Adult gynes have been shown to have higher lipid stores, smaller ovaries, and have higher cold tolerance than workers (Bohm 1972;Strassmann et al. 1984;Toth et al. 2009). During development, gyne-destined larvae have higher levels of lipid and potassium and lower levels of protein than worker destined larvae (Judd et al. 2010). ...
Caste determination in social insects with morphologically distinct castes occurs during a critical period during the larval stage. In contrast, in social insects without morphologically distinct castes the time of eclosion can act as an additional critical period. A number of cues have been identified that influence caste differentiation in social insects but to date, most of the studies have used physiological correlates to determine the effects of these cues on caste determination. Few studies have measured behavioral differences in a natural setting. In this field study, the behavioral and nutritional profiles of individuals of the paper wasp Polistes metricus emerging on nests with and without larvae were determined and compared to emerging workers and gynes from unmanipulated colonies. Based on previous studies, it was predicted that individuals eclosing on nests with larvae would have similar profiles to workers and those eclosing on nests without larvae would have similar profiles to gynes. Individuals that emerged on colonies with larvae had similar behavioral and nutritional profiles to workers as expected. Individuals that emerged on nests without larvae had behavioral and nutritional profiles that were in between workers and gynes and showed signs of active reproduction and nest construction. The results of this study were combined with those of other studies into a model that proposes that there are three thresholds, one in response to photoperiod, one during the larval stage, and one during eclosion that determines if individuals will be workers, active reproducers, or overwintering gynes. This model provides a more complete picture of caste determination in Polistes.
... In contrast, in some other species it is hard to find morphological features to distinguish castes; for this reason, some authors have looked into other kinds of parameters. Strassmann et al. (1984) reported differences linked to the capability of gynes to overwinter. This explained why foundresses develop multistratified fat bodies whereas workers do not (Eickwort 1969, Toth et al. 2009). ...
In theVespinae, morphological differences of castes are generally well-marked, except for some Vespa species, where it is difficult to distinguish between future queens and workers in autumn-winter colonies. Individual weights have widely been used as a distinguishing factor but recently cuticular hydrocarbon profiles seems to be the definitive tool, although much more expensive and time-consuming. Parameters such as size (mesoscutum width), wet and dry weight were analysed, throughout several colonies, to differentiate female castes (workers and gynes) in the hornet Vespa velutina in Europe. These parameters were compared to cuticular hydrocarbon profiles. The results showed that in late autumn, but not earlier, populations are divided into two size groups, which, based on their CHC profiles, can be hypothesized to correspond to workers and gynes. This differentiation mirrored a good separation by size that proves to be more accurate than weight (wet and dry). The size limit between workers and gynes is established at a mesoscutum width of 4.5 mm.
... Maeta et al. (1992) experimentally tested cold tolerance in C. flavipes and determined a relatively weak influence of body size on offspring survival in cold exposure for both males and females. However, reduced fat stores have been linked to reduced overwinter survivorship in bees and wasps (Strassmann et al. 1984;Toth et al. 2009;Durant et al. 2016, but see Richards and Packer 1996;Weissel et al. 2012). Therefore, it seems that the reduced body size of foraging daughters may already have a negative influence on winter survivorship, which is likely only exacerbated by her increased foraging activity and reduced fat stores. ...
Provisioning for young offspring is an archetypical form of parental investment. Ceratina calcarata bees provide extended maternal care to their young and demonstrate an unusual strategy of dual-phase pollen provisioning. Most bees first gather provisions as they establish nests in spring. However, C. calcarata mothers will also feed their newly eclosed young a second time, perhaps ensuring their survival during a long winter diapause. Some mothers rear a small, worker-like daughter to assist them during this second provisioning phase. We studied provisioning behavior in C. calcarata to examine patterns of maternal investment and foraging dynamics throughout the breeding season. Mothers typically made a high number of short-duration foraging trips each day, whereas late-season females tended to make fewer and longer trips. This difference in foraging duration may indicate a lower risk of brood loss in those nests where mature offspring are present. Nest demographic data revealed that an offspring laid in the first brood cell position is typically female and usually smaller than her siblings. In 29% of the nests, this small daughter was observed to adopt a forager role at maturity and provisioned for her siblings. Dwarf daughters had a higher number of active days and foraging trips per day in orphaned nests than in nests where a mother was present. The foraging behaviors of worker-like daughters were similar in length of foraging trip and handling time to mothers during this second provisioning period. We hypothesize that incipiently social foraging by this smallest daughter may act as a form of insurance against brood loss during occasions when a mother is unable to sufficiently provision for her eclosed offspring during the second phase.
Significance statement
Parental investment in the size and sex of offspring is under strong selection for assured fitness returns. For example, many social insect mothers make an initial investment in small offspring to take on risky foraging behavior while they specialize on future reproduction. Solitary and facultatively social species provide an important baseline to understand the evolution of social complexity from natural variation in maternal care and foraging behavior. Here, we characterize the parental investment strategies of a subsocial small carpenter bee and reveal the potential adaptive significance of prolonged maternal care and worker production in this species. Mothers provide an initial investment that is extended by workers providing alloparental care to siblings. Maternal manipulation of dwarf eldest daughters may serve as an insurance mechanism in the event of maternal mortality to assure the survival of siblings.
... One under-represented protein domain of interest is the Perilipin gene family. Perilipin is also known as lipid droplet-associated protein or PLIN, a protein that, in (Strassmann et al. 1984;Toth et al. 2009;Wasielewski et al. 2014;Durant et al. 2016). ...
Understanding the evolution of animal societies, considered to be a major transition in evolution, is a key topic in evolutionary
biology. Recently, new gateways for understanding social evolution have opened up due to advances in genomics, allowing for
unprecedented opportunities in studying social behavior on a molecular level. In particular, highly eusocial insect species
(caste-containing societies with non-reproductives that care for siblings) have taken center stage in studies of the molecular
evolution of sociality. Despite advances in genomic studies of both solitary and eusocial insects, we still lack genomic resources
for early insect societies. To study the genetic basis of social traits requires comparison of genomes from a diversity of
organisms ranging from solitary to complex social forms. Here we present the genome of a subsocial bee, Ceratina calcarata. This study begins to address the types of genomic changes associated with the earliest origins of simple sociality using
the small carpenter bee. Genes associated with lipid transport and DNA recombination have undergone positive selection in
C. calcarata relative to other bee lineages. Further, we provide the first methylome of a non-eusocial bee. C. calcarata contains the complete enzymatic toolkit for DNA methylation. As in the honey bee and many other holometabolous insects, DNA
methylation is targeted to exons. The addition of this genome allows for new lines of research into the genetic and epigenetic
precursors to complex social behaviors.
... At this early time in the colony cycle the adult-to-larva ratio is low [30,33], which leads to low feeding rates and more limited larval nourishment compared to offspring reared by workers and produced later in the colony cycle (future queens or "gynes"). Physiological evidence of nourishmentrelated differences between workers and gynes collected from naturally-founded colonies in the field include greater fat body stores in gynes [34,35], greater quantities of the storage protein hexamerin 1 in gynes [36,37], and greater quantities of four additional proteins in gynes [14]. Experimental studies show that nourishment inequalities that correspond to early-season and late-season larval development contexts are associated with development of offspring having characteristics of worker and gyne phenotypes, respectively [38,39]. ...
Social insects exhibit striking phenotypic plasticity in the form of distinct reproductive (queen) and non-reproductive (worker) castes, which are typically driven by differences in the environment during early development. Nutritional environment and nourishment during development has been shown to be broadly associated with caste determination across social insect taxa such as bees, wasps, and termites. In primitively social insects such as Polistes paper wasps, caste remains flexible throughout adulthood, but there is evidence that nourishment inequalities can bias caste development with workers receiving limited nourishment compared to queens. Dominance and vibrational signaling are behaviors that have also been linked to caste differences in paper wasps, suggesting that a combination of nourishment and social factors may drive caste determination. To better understand the molecular basis of nutritional effects on caste determination, we used RNA-sequencing to investigate the gene expression changes in response to proteinaceous nourishment deprivation in Polistes metricus larvae.
We identified 285 nourishment-responsive transcripts, many of which are related to lipid metabolism and oxidation-reduction activity. Via comparisons to previously identified caste-related genes, we found that nourishment restriction only partially biased wasp gene expression patterns toward worker caste-like traits, which supports the notion that nourishment, in conjunction with social environment, is a determinant of developmental caste bias. In addition, we conducted cross-species comparisons of nourishment-responsive genes, and uncovered largely lineage-specific gene expression changes, suggesting few shared nourishment-responsive genes across taxa.
Overall, the results from this study highlight the complex and multifactorial nature of environmental effects on the gene expression patterns underlying plastic phenotypes.
... Fat content, adult weight and water balance have been shown to affect the overwintering survival rates of many butterfly species (Pullin, 1987;Williams et al., 2012). In addition, ant castes may differ in their degree of resistance to cold (Strassmann et al., 1984;Tauber et al., 1986;Leather et al., 1993). A large body size might well predict an increase in overwintering survival rates, as it does for bumblebees, B. terrestris and B. lucorum (Beekman et al., 1998;, the eastern yellow-jacket, Vespula maculifrons (Kovacs and Goodisman, 2012) and the ant, Leptothorax acervorum (Heinze et al., 1998). ...
... Several studies have examined caste distinctions in Polistinae. For the tribe Polistini, studies have involved behavioral aspects, ovarian development, morphology and cuticular hydrocarbon profile of Polistes females (Strassmann et al 1984, Solis & Strassmann 1990, Dani 1994, Giannotti & Machado 1999, Gobbi et al 2006, Tannure-Nascimento et al 2008, Torres et al 2009. Studies analyzing the determination, differentiation, and characterization of castes in Mischocyttarini were also performed (Noda et al 2001, Torres et al 2012, Murakami et al 2009. ...
In the subfamily Polistinae, caste dimorphism is not pronounced and differences among females are primarily physiological and behavioral. We investigated factors that indicate the reproductive status in females of Polistes ferreri Saussure. We analyzed females from nine colonies and evaluated morphometric parameters, ovarian development, occurrence of insemination, relative age, and cuticular chemical profile. The colony females showed three kinds of ovarian development: type A, filamentous ovarioles; type B, ovarioles containing partially developed oocytes; and type C, long and well-developed ovarioles containing two or more mature oocytes. The stepwise discriminant analysis of the cuticular chemical profile showed that it was possible to distinguish the three groups of females: workers 1, workers 2, and queens. However, the stepwise discriminant analysis of the morphological differences did not show significant differences among these groups. The queens were among the older females in the colony and were always inseminated, while the age of the workers varied according to the stage of colony development.
... The key role of caste has probably been neglected in the genus Ropalidia because these wasps have a tropical distribution; as a consequence, in these species nest founding and male production occur throughout the year and all females are nearly reproductively totipotent and morphologically similar Bang & Gadagkar 2012). In temperate Polistes species, instead, the colony cycle is strictly regulated by the season and only gynes survive the winter owing to their higher levels of cryoprotectant, consisting mainly of fructose, in their haemolymph, and lipid storage, compared to workers that die at the end of summer (Strassmann et al. 1984;Toth et al. 2009). Thus, the most parsimonious hypothesis is that P. dominula males evolved their ability to discriminate between functional castes to avoid the waste of both energy and their limited sperm storage in mating with females that will most likely not provide a profitable return in terms of fitness. ...
Discrimination among potential partners is a critical step in sexual selection to avoid wasting reproductive
resources on an unsuitable mate. In the female-dominated hymenopteran societies males have
often been regarded as ‘flying sperm containers’ spending all their time and energy in trying to acquire a
mate.We investigated the male sexual preference for potential partners using as a model the primitively
eusocial wasp Polistes dominula in which female caste is rather flexible and difficult to determine. By
means of laboratory bioassays, we compared the males’ behaviour towards females of different reproductive
potential. Males were able to recognize female castes, strongly preferring reproductive females to
workers, regardless of female age or health. The results show that in this species caste plays a key role in
orienting male discrimination and preference, presumably through chemical cues, towards reproductive
females both healthy and parasite-castrated. Overall, our study shows that social Hymenoptera males are
not always ‘small mating machines’ eager to mate.
... De acordo com Giannotti & Machado (1999) e Zara & Balestieri (2000) estudando colônias de P. lanio e P. versicolor, respectivamente, as rainhas dessas espécies permanecem a maior parte do tempo no ninho, sobre as células enquanto que as operárias gastam um tempo maior forrageando. Rainhas permanecem mais tempo no ninho, uma vez que evitam atividades de alto custo energético e risco, tais como forrageamento, as quais são desempenhadas pelas operárias (Strassmann et al. 1984;O'Donnell 1998). ...
Using "scanning sample" methods for qualifying and quantifying behavioral acts of queens and workers belonging to fifteen colonies of Polistes canadensis canadensis, one hundred hours of observation were performed. A behavioral repertoire with twenty-eight acts was described, in which queens perform nineteen acts in the colony, while workers perform twenty-six, and seventeen common acts between the two castes occur. Among those acts, two were exclusive to queen's repertoire and nine to worker's. Chi-square test pointed significant differences between the repertoires of the two castes, where the queens remain longer in the nest and perform the intra-nidal tasks, related to the reproduction, while the workers perform more frequently tasks related to the maintenance of the colonies, such as the foraging, which demands higher risks and high energetic costs.
... In summer, both castes have undeveloped ovaries, but while a worker is the target of social ovariectomy and destined to die after a few weeks of work (West-Eberhard 1996), a gyne is constrained from ovary development (Toth et al. 2009) only until the following spring. Moreover, gynes are characterized by the capability to withstand cold temperatures (Eickwort 1969;Strassmann et al. 1984) and by high lipid levels (see Toth et al. 2009). ...
The macroparasite Xenos vesparum affects both the behaviour and the physical traits of its host, the social wasp Polistes dominulus. Female wasps, if parasitized, do not perform any social tasks and desert the colony to gather at specific sites, where the parasite mates; at the end of summer they form prehibernating clusters joined by healthy future queens to overwinter. Parasitized wasps become highly gregarious. In April, healthy wasps leave the aggregations to found new colonies, while parasitized wasps remain in overwintering groups and release parasites to infect wasp larvae only later in the season. We studied the prolonged gregarious behaviour of parasitized wasps and analysed the morphology of parasitized and healthy wasps in aggregations collected over a 7-year period to determine whether the parasite affects host size, wing symmetry, ovarian development and lipid stores. All parasitized wasps were smaller and had undeveloped ovaries and more wing fluctuating asymmetry than unparasitized wasps, irrespective of time of year, parasite load and parasite sex. If infected only by one or two X. vesparum females, the wasps had large fat bodies, which could facilitate their overwintering. In contrast, wasps infected by at least one male parasite had little lipid and died at the end of the summer. Thus, X. vesparum, may play a role in the fate of its host, by exploiting wasps' tendency to form aggregations outside the colony and by altering its caste system, nutrient allocation, diapause timing and life span to achieve its own reproduction and dispersal.
... This increase of mass in our case is also due to larger fat bodies (I.K. and J.H.H., unpublished data). Strassmann et al. (1984) showed that Polistes gynes are more tolerant of cold than are workers. Although the offspring wasps in the current study were those logically destined to be workers (i.e., the Þrst 10 emerged females), the hand-fed wasps were able to survive in the cold longer than control wasps. ...
The effects of food quantity on the morphology and development of the paper wasp Polistes metricus Say are studied, and experimental results are compared with predictions of the parental manipulation hypothesis. Food deprivation led to smaller female offspring. By hand feeding larvae we used a technique that counteracts the queen's hypothesized ability to restrict food provisioning. Hand feeding larvae did not result in larger offspring, but their abdomen was wider and heavier and the hand-fed wasps survived longer in a cold test. We infer that hand-fed colonies produced more gynes and fewer workers than did control colonies. Results of a restricted nourishment treatment do not support the differential feeding hypothesis, because in fasting colonies the emergence of all larvae was delayed by a month, and we did not detect discriminatory feeding of particular larvae for faster emergence. Although fasting colonies produced fewer offspring, the sex ratio did not show significant differences from the other groups. These data suggest that Polistes metricus colonies are partly able to respond to different nutritional conditions by allocating excess food to increase the number of gynes at the expense of workers.
... In queens, stored nutrients are likely to be directed to the ovaries, therefore it is probable that the overall lipid stores of queens if ovaries were included would be greater than what we report here. Even so, our finding of high lipid stores in gynes coincides with previous studies demonstrating high storage protein levels (Hunt et al., 2003) and the appearance of large fat bodies in gynes compared to other groups (Eickwort, 1969;Strassmann et al., 1984;Karsai and Hunt, 2002). Thus, our results support the idea that gynes invest in energy storage, as opposed to reproductive development, as an adaptation for overwintering . ...
In order to gain insights into the mechanistic basis of caste and behavioral differences in Polistes paper wasps, we examined abdominal lipid stores and ovary development in Polistes metricus females in four groups: foundresses, queens, workers, and gynes. Queens had the largest ovaries, followed by foundresses,
workers, and gynes. Gynes had 6x higher lipid stores than the other groups, and lipid stores were lower in foragers (foundresses,
workers) than non-foragers (queens, gynes). Lipid levels and ovary development were negatively correlated across the four
groups, but removing gynes from the analysis revealed a significant positive correlation for foundresses, workers, and queens,
suggesting different energy allocation strategies for gynes vs. other groups. Expression levels of 9 genes (including three
in the insulin pathway), examined in a previous study, correlated with either lipid stores or ovary development. These correlative
results suggest important relationships between nutrition, reproduction, and division of labor in primitively social insects.
We also show that it is possible to assign P. metricus females to one of the four female groups on the basis of wing wear (an indicator of foraging experience), lipid stores, and
ovary development, which can facilitate caste-specific collections for future studies.
... Above and beyond description and documentation, these can be experimentally manipulated. Experimental outcomes indicate that underlying differences in castelike phenotypes are affected by factors in real time at both individual (Dew & Michener, 1981; Strassmann et al., 1984; Rossi & Hunt, 1988; Solís & Strassman, 1990; Mead & Gabouriaut, 1993; Mead et al., 1995; Karsai & Hunt, 2002; Tibbetts et al., 2011) and colony levels (Hunt & Dove, 2002; Mead & Pratte, 2002; Seal & Hunt, 2004). It is noteworthy that all of the factors can be linked to differential nourishment either among larvae or among adults or both. ...
In a model based on the wasp family Vespidae, the origin of worker behaviour, which constitutes the eusociality threshold, is not based on relatedness, therefore the origin of eusociality does not depend on inclusive fitness, and workers at the eusociality threshold are not altruistic. Instead, incipient workers and queens behave selfishly and are subject to direct natural selection. Beyond the eusociality threshold, relatedness enables 'soft inheritance' as the framework for initial adaptations of eusociality. At the threshold of irreversibility, queen and worker castes become fixed in advanced eusociality. Transitions from solitary to facultative, facultative to primitive, and primitive to advanced eusociality occur via exaptation, phenotypic accommodation and genetic assimilation. Multilevel selection characterizes the solitary to highly eusocial transition, but components of multilevel selection vary across levels of eusociality. Roles of behavioural flexibility and developmental plasticity in the evolutionary process equal or exceed those of genotype.
... Ability to survive winter, together with the fat reserves upon which it probably depends, has been used to distinguish gynes from workers in temperate-zone social wasps (Eickwort, 1969;Strassmann et al., 1984;Solís and Strassman, 1990). In B. petiolata, both foundresses (queens and subordinates) and gynes had significantly more fat than workers, indicating that in this species too, fat content is an indicator of caste. ...
Until recently, morphological differences between castes in independent-founding polistine wasps were considered absent. This paper investigates the extent of morphological and physiological differences between reproductive (foundress and gyne) and worker castes of Belonogaster petiolata, and tests the hypothesis that caste differentiation in this species occurs pre-imaginally.Foundresses were significantly larger than workers, to the extent that foundress/worker ratios were comparable with those between queens and workers in some swarm-founding Polistinae. Early emerging workers were small, but body size increased over the colony cycle such that late-season workers were similar in size to gynes. In proportion to body size, workers possessed broader heads while foundresses and gynes had broader thoraces and gasters. All queens, 98% of subordinate foundresses, and 95% of over-wintering gynes were inseminated. Workers were never inseminated and lacked mature ovaries in colonies with active queens. However, in the absence of the queen (and other foundresses), 11% of workers developed mature ovaries. Ovarian size and fat content of foundresses and gynes was significantly greater than that of workers. The differences in external morphology and reproductive physiology between castes support the hypothesis that differentiation occurs pre-imaginally. However, imaginal factors, in particular social dominance of the queen, maintain the reproductive subordinance of workers.
... We present the first data on the molecular basis of behavioural queen/worker caste polyphenisms in a primitively eusocial society. Polistes canadensis is an ideal species in which to study castes because it is restricted to the relatively aseasonal tropics where, in contrast to temperate species of Polistes, both workers and queens are long-lived (Pickering 1980), caste is not influenced by the time of year that a female emerges (Mead & Gabouriaut 1993), and size/nutrition is unlikely to influence caste as queens do not hibernate (Strassmann et al. 1984;Sullivan & Strassmann 1984). We first identified genes that were differentially expressed between pairs of the three behavioural castes within P. canadensis (young females, Y; workers, W; and queens, Q). ...
Understanding how a single genome can produce a variety of different phenotypes is of fundamental importance in evolutionary and developmental biology. One of the most striking examples of phenotypic plasticity is the female caste system found in eusocial insects, where variation in reproductive (queens) and non-reproductive (workers) phenotypes results in a broad spectrum of caste types, ranging from behavioural through to morphological castes. Recent advances in genomic techniques allow novel comparisons on the nature of caste phenotypes to be made at the level of the genes in organisms for which there is little genome information, facilitating new approaches in studying social evolution and behaviour. Using the paper wasp Polistes canadensis as a model system, we investigated for the first time how behavioural castes in primitively eusocial insect societies are associated with differential expression of shared genes. We found that queens and newly emerged females express gene expression patterns that are distinct from each other whilst workers generally expressed intermediate patterns, as predicted by Polistes biology. We compared caste-associated genes in P. canadensis with those expressed in adult queens and workers of more advanced eusocial societies, which represent four independent origins of eusociality. Nine genes were conserved across the four taxa, although their patterns of expression and putative functions varied. Thus, we identify several genes that are putatively of evolutionary importance in the molecular biology that underlies a number of caste systems of independent evolutionary origin.
Species with widespread distributions frequently show clines in body size across broad geographic areas. These clines may be the result of “ecogeographical rules” that describe spatial patterns of phenotypic differences driven by environmental variation. Intraspecific variation in body size, and the mechanisms causing this variation, have been poorly described in social wasps. This study examined ecogeographical patterns of body size for 12 native species and one non-native species of North American paper wasps (genus: Polistes) using body size measurements from > 14,000 pinned museum specimens. Intraspecific body size was correlated with latitude, elevation, and broadscale climate variation. However, the direction of this relationship was idiosyncratic across species, with Bergmann’s clines and converse Bergmann’s clines equally represented. There was no evidence of a phylogenetic signal in the direction of the cline between body size and the environment. Within species, the worker caste and the reproductive caste showed the same direction of response between body size and latitude, although for most species the reproductive caste was larger than the worker caste. Intraspecific variation in body size appears to be driven by differences in the response among species to similar environmental variables but the mechanisms causing this variation remain unknown.
By manipulating resources or dispersal opportunities, mothers can force offspring to remain at the nest to help raise siblings creating a division of labor. In the subsocial bee, Ceratina calcarata mothers manipulate the quantity and quality of pollen provided to the first female offspring producing a dwarf eldest daughter, who is physically smaller and behaviorally subordinate. This daughter forages for her siblings and forgoes her own reproduction. To understand how the mother's manipulation of pollen affects the physiology and behavior of offspring, we manipulated the amount of pollen provide to offspring and measured the effects of pollen quantity on offspring development, adult body size and behavior. We found that by experimentally manipulating pollen provision quantities we could recreate the dwarf eldest daughter phenotype demonstrating how nutrient deficiency alone can lead to the development of a worker-like daughter. Specifically, by reducing the pollen and nutrition to offspring, we significantly reduced adult body size and lipid stores creating significantly less aggressive, subordinate individuals. Worker behavior in an otherwise solitary bee begins to explain how maternal manipulation of resources could lead to the development of social organization and reproductive hierarchies, a major step in the transition to highly social behaviors.
The study of wasp societies (family Vespidae) has played a central role in advancing our knowledge of why social life evolves and how it functions. This dissertation asks: How have scientists generated and evaluated new concepts and theories about social life and its evolution by investigating wasp societies? It addresses this question both from a narrative/historical and from a reflective/epistemological perspective. The historical narratives reconstruct the investigative pathways of the Italian entomologist Leo Pardi (1915-1990) and the British evolutionary biologist William D. Hamilton (1936-2000). The works of these two scientists represent respectively the beginning of our current understanding of immediate and evolutionary causes of social life. Chapter 1 shows how Pardi, in the 1940s, generated a conceptual framework to explain how wasp colonies function in terms of social and reproductive dominance. Chapter 2 shows how Hamilton, in the 1960s, attempted to evaluate his own theory of inclusive fitness by investigating social wasps. The epistemological reflections revolve around the idea of investigative framework for theory evaluation. Chapter 3 draws on the analysis of important studies on social wasps from the 1960s and 1970s and provides an account of theory evaluation in the form of an investigative framework. The framework shows how inferences from empirical data (bottom-up) and inferences from the theory (top-down) inform one another in the generation of hypotheses, predictions and statements about phenomena of social evolution. It provides an alternative to existing philosophical accounts of scientific inquiry and theory evaluation, which keep a strong, hierarchical distinction between inferences from the theory and inferences from the data. The historical narratives in this dissertation show that important scientists have advanced ii our knowledge of complex biological phenomena by constantly interweaving empirical, conceptual, and theoretical work. The epistemological reflections argue that we need holistic frameworks that account for how multiple scientific practices synergistically contribute to advance our knowledge of complex phenomena. Both narratives and reflections aim to inspire and inform future work in social evolution capitalizing on lessons learnt from the past. iii ACKNOWLEDGMENTS
Social insects attract special attention due to their complex social interaction among individuals and their capability of forming extremely well-organized societies. In this context, social wasps represent an important group in evolutionary studies of sociality in Hymenoptera, as every step of social organization is observed, permitting the development of evolutionary scenarios which may explain the social behavior in Hymenoptera. Perhaps the main feature of social insects is the division into castes, and the higher the dimorphism between castes, the higher the level of sociality. In fact, in some groups regarded as highly eusocial such as honeybees, termites, some ants and the vespines, caste differences are extremely pronounced and the control of sociality is exercised mostly by the queens. However, in the Polistinae, some groups are regarded as basal eusocial and caste differences are absent. Such a pattern is found in Polistini, Ropalidini (some Ropalidia, Parapolybia and Belonogaster) and Mischocyrarini; in these tribes, social organization is maintained through agonistic interactions based on a hierarchy rank. Perhaps the most enigmatic situation is found in the highly eusocial swarm-founding Epiponini, in which caste systems range from species with no detectable dimorphism to species with conspicuous morphological differences. Unlike honeybees and vespines, the society of the Epiponini is characterized by a "conspiracy of workers" and the queens do not play an important role in the control of sociality. Moreover, the Epiponini society is polygynic, while the other highly eusocial insects are monogynic, and the workers control the queen demography in a process known as cyclical oligogyny. The aim of this review is to discuss the main aspects related to the caste system in social wasps with special attention to the Neotropical swarm-founding Polistinae. We provide substantial data regarding the caste system in social wasps; however, the mechanisms which led to caste differences in wasps are not well known and represent an important subject for future studies.
Of all social insects, probably the least well known are social wasps. This is especially true of the mechanisms of caste induction and the regulation of reproductory functions in the wasp colony.
Cette étude montre que la durée de vie des femelles de poliste est influencée, dans les limites d'une probable prédisposition larvaire, par les conditions sociales rencontrées à l'émergence. La séparation précoce d'avec le guêpier d'origine diminue fortement la proportion des descendantes qui supportent l'hiver et fondent au printemps suivant. Par contre, la destruction, dans le couvain, des larves de grande taille provoque un accroissement de la proportion des descendantes à vie longue parmi les guêpes subissant cette situation à l'état imaginal.
On discute la signification fonctionnelle de ces résultats.
Social behavior occurs in some of the smallest animals as well as some the largest, and the transition from solitary life to sociality is an unsolved evolutionary mystery. The Evolution of Social Wasps examines social behavior in a single lineage of insects, wasps of the family Vespidae. It presents empirical knowledge of social wasps from two approaches: one that focuses on phylogeny and life history; and one that focuses on individual ontogeny, colony development, and population dynamics. It also provides an extensive summary of the existing literature while demonstrating how it can be clouded by theory. This approach to the conflicting literature on sociality highlights how often repeated models can become fixed in the thinking of the scientific community. Instead, it presents a mechanistic scenario for the evolution of sociality in wasps that changes our perspective on kin selection, the paradigm that has dominated thinking about social evolution since the 1970s.
Recent studies report that reproductive and non-reproductive roles of individuals can be associated with body size variation and/or physiological differences in many primitively eusocial wasps. This paper investigates the effects of the season on the body size and reproductive differences in Polistes satan. In pre-emergence colonies, inseminated females are significantly larger than subordinates for most of body measurements. Season has no effect on the differences related to the body size between inseminated females and uninseminated females from post-emergence colonies. However, most morphometric variables were significantly different between uninseminated females collected in distinct periods of the year. We suggest that seasonal variation may affect uninseminated females directly reflecting a flexible developmental programme in primitively eusocial wasps.
The behavior of workers on 2 nests of the Japanese paper wasp,Polistes jadwigae, was recorded on video tape. Young workers performed pulp collection more frequently than middle-aged and old workers, while
foraging of flesh (prey) was done mainly by middle-aged workers. Of the 26 behavioral categories, 7 showed negative, 2 concave,
and 1 convex relationship to the workers age. Using behavioral profiles, workers could be classified into 3 age groups: 1)
young workers (younger than 10 days old, active intranidal workers), 2) middle-aged workers (11–25 days old, extranidal workers)
and 3) old workers (older than 26 days old, ‘idlers’). Idlers engaged in foraging and larval feeding significantly less frequency
than the young and middle-aged workers, but they performed alerting toward many alien objects. Task specialization among workers
irrespective of age polyethism was also suggested.
Polistes dominulus females were subjected to the following changes of social environment as soon as they emerged: females which emerged in young colonies (presumably most workers) were transferred to more mature colonies, and conversely, females which emerged in mature colonies (presumably mostly gynes) were transferred to younger colonies. The behavioural and biological data obtained here show that when exposed to the new social environment, females from young colonies were able to lengthen their life span and become gynes. Only the very first females to emerge from colonies were less able to survive hibernation. Conversely, females from mature colonies were able to become workers and, as a result of their participation in social tasks, had a shorter life span. This great plasticity in the roles which young adult females can adopt constitutes an important characteristic of primitively eusocial species.
In a previous paper we described a study under laboratory conditions of the pattern of development of the various categories of descendants during the life of a colony; the present study is particularly concerned with the duration of life-span of these various categories.
The life-spans of females showed a bimodal distribution and short-lived and long-lived wasps were distinguished. Considerable overlap was observed between the periods during which these two categories of wasp emerged.
A relationship was found to exist between the date of orphanship, the percentage of “short-lived” females and the sex ratio of the offspring. Colonies which lost their queen as early as June showed an increase in the number of descendants produced, but these descendants were predominantly male and, among the females, the majority were “short-lived”.
Social insects are excellent invaders that have had negative impacts on native species and humans. Many invasive species move
from warmer to cooler climates. For these species, thermal adaptations may both be important for their ability to invade and
to limit their invasion range. The invasion of Polistes dominulus into North America provides an example of a primitively eusocial invader from a warmer climate. We studied the differences
in thermoregulation between P. dominulus and the native P. fuscatus. We found that, during flight, thorax temperature in P. fuscatus was less affected by ambient temperature than thorax temperature of P. dominulus. We also found that P. dominulus and P. fuscatus showed different patterns of warming after removal from a cold environment. Unlike P. dominulus, live P. fuscatus never fully cooled down in a cold environment. P. fuscatus also reached their relative minimum flight temperatures earlier than P. dominulus, but P. dominulus maintained higher elevated temperatures for longer. These differences in thermoregulatory ability suggest that the lower
winter survival of P. dominulus could be offset by a greater thermal tolerance during flight, while the lower thermal tolerance of P. fuscatus in flight is offset somewhat by better thermoregulatory ability.
KeywordsExotic species–Hymenoptera–Eusociality–Thermoregulation
1.1. Sugars, sugar-alcohols, glycogen, triacylglycerol contents in hibernating adult bees are compared in relation to the hibernating habits of the bees. Monosaccharide content is low in Andrena and Osmia which hibernate in natal blood cells, which very high in Lasioglossum spp. which feed before hibernation.2.2. Distribution of sugars within the body of hibernating Lasioglossum reveals that trehalose is the major sugar accumulated in hemolymph, and that the crop contains a large amount of monosaccharides.3.3. Seasonal changes of sugars and glycogen contents in L. duplex strongly suggest that trehalose accumulated is derived, not from the glycogen in the fat body, but from monosaccharides in the crop.
Genetic relatedness is expected to play a crucial role in the evolution of altruistic behaviors such as worker behavior in the social insects. If individuals sacrifice their own reproduction, then the genes for this sacrifice will be lost unless these individuals aid the reproduction of others who share the genes. This leads to the prediction that altruism should be most common in species with high relatedness among potential beneficiaries. Here we report an attempt to test for such an association. We estimated both the incidence of altruism and the relatedness to potential beneficiaries in foundresses of seven species of paper wasps. The predicted positive correlation was not found, and we conclude that factors other than relatedness are more important in determining interspecific differences in the incidence of altruism.
Wasps of family Vespidae contain three types of major proteins that have the size, amino acid composition, subunit composition, immunological reactivity, and pattern of occurrence characteristic of storage proteins. The three types of storage protein, which have been identified in other Hymenoptera, are very high density lipoprotein, high glutamine/glutamic acid protein, and hexamerin. The predominant pattern of occurrence for these proteins is as known from most or all Holometabola: synthesis during the last larval instar and utilization as an amino acid source during metamorphosis. Hexamerin also occurred in a large young adult female Monobia quadridens but not a small one, which suggests that carry-over into adult females is a reaction norm response to quantity of larval provisions, because these wasps could not have fed as adults. In two paper wasp species of the genus Polistes, hexamerin was present in large adult females which emerged during the colony cycle phase when reproductive females are typically produced, but not in adult female offspring that emerged earlier in the colony cycle or in adult females that were workers. It cannot be confirmed by these data that the hexamerin in the adult paper wasps represented carry-over from metamorphosis rather than post-emergence feeding, but the pattern of occurrence suggests that presence of storage protein may play a role in caste differentiation in paper wasps. No storage protein was found in any adult Vespula maculifrons, a yellowjacket wasp, suggesting that caste differentiation in vespine wasps does not incorporate storage protein as a component.
Colonies of social wasps, ants, and bees are characterized by the production of two phenotypes of female offspring, workers that remain at their natal nest and nonworkers that are potential colony reproductives of the next generation. The phenotype difference includes morphology and is fixed during larval development in ants, honey bees, and some social wasps, all of which represent an advanced state of sociality. Paper wasps (Polistes) lack morphological castes and are thought to more closely resemble an ancestral state of sociality wherein the phenotype difference between workers and nonworkers is established only during adult life. We address an alternative hypothesis: a bias toward the potential reproductive (gyne) phenotype among Polistes female offspring occurs during larval development and is based on a facultatively expressed ancestral life history trait: diapause. We show that two signatures of diapause (extended maturation time and enhanced synthesis and sequestration of a hexameric storage protein) characterize the development of gyne offspring in Polistes metricus. Hexameric storage proteins are implicated in silencing juvenile hormone signaling, which is a prerequisite for diapause. Diverging hexamerin protein dynamics driven by changes in larval provisioning levels thereby provide one possible mechanism that can cause an adaptive shift in phenotype bias during the Polistes colony cycle. This ontogenetic basis for alternative female phenotypes in Polistes challenges the view that workers and gynes represent behavior options equally available to every female offspring, and it exemplifies how social insect castes can evolve from casteless lineages.
• caste development
• hexameric storage proteins
• juvenile hormone
• life-history pleiotropy
• social behavior
Foundresses and workers of Polistes paper wasps show slight morphological and physiological differences. However, after the emergence of the workers, the castes can be readily discriminated by their behaviour: the dominant foundress is the principal egg-layer, whereas workers perform different tasks linked to colony development. Previous studies have demonstrated in this genus that defence of the colony by the workers is more effectively carried out by a collective response elicited by venom volatiles used as alarm pheromones. In the present study, gas chromatography-mass spectrometry analyses of the venom volatiles of foundresses and workers of Polistes dominulus (Christ) show predominantly quantitative differences. Spiroacetals, mainly (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, are significantly higher in the venom volatiles fraction of workers, whereas the amount of N-(3-methylbutyl)acetamide is almost double in foundresses. On the basis of the chemical results, behavioural assays were performed on fifteen field colonies to test the alarm response of the resident wasps to venom extracts from foundresses and workers. Our behavioural results suggest that worker venom has a stronger alarm effect on the colonies than that of the foundresses, which seems unable to elicit the complete alarm response ending with a final attack and sting. The venom volatiles of P. dominulus workers serve mainly to alarm the colony whilst those of foundresses may also be linked to additional functions related to conspecific interactions.
Sex-investment ratios were measured in a Polistes exclamans population and found to be female-biased (1976, 74% females; 1979, 63% females) in 2 years and close to even in 2 years (1977, 58% females; 1978, 53% females). Sex ratios are female-biased in years of high levels of bird predation on nests and low overall nest success. Males emerge later from the nest so anything that results in an early end to the colony cycle decreases the numbers of males. Sex ratios on nests whose original queens were replaced by a mated worker did not differ from sex ratios on nests with original queens. Sex ratios may be generally female-biased because a female can become either a worker or a gyne, so females are a more flexible asset to a nest than are males. Thus nests producing females before males may be able to produce greater total numbers of reproductives. This flexibility may be important for high reproductive success of nests given highly variable date of cool weather onset in central Texas. This hypothesis does not appear to apply to primitively eusocial Hymenoptera in general, where even sex ratios and simultaneous emergence of males and gynes are most common.
Abstract-Northern,and southern,populations,of the gall fly Eurosta soliduginis utilize quantitatively distinct adaptive strategies when exposed to a laboratory simulation of winter temperatures, Both populations,are freezing tolerant and rely in part on,the temperature-dependent,accumulation,of gly- cerol and sorbitol, and static but elevated levels of trehalose for protection. The accumulation triggers are time-temperature dependent. For northern and southern populations, exposure to 5-C for periods exceeding,24 hr. but less than,5 days,or 5’C with,a gradual,reduction,(l’C/day) results in the accumu- lation of sorbitol,at 1.5 pg/mg/day. Glycerol,levels remain,essentially,constant,between,10’ and,- 25’ C in each population. However, the concentration of glycerol in the Minnesota population is 334 times greater that that of the Texas specimens. Haemolymph,melting points varied quantitatively with chang- ing cryoprotectant,levels. No significant difference was noted between,the supercooling,points of each population. This suggests that ice-nucleator levels were comparable,throughout,the exposure,period. Ke!, Worrl Intlr.~: Insect cold-hardiness, cryoprotectant, supercooling. Eurostcr solidoginis
Cold-hardiness was investigated in fall and winter populations of the social wasp Polistes fuscatus (Fabricius), Individuals collected in the fall were able to survive 48 h at −10 °C. Both sexes were equally capable of surviving −5 °C. However, at −7.5 °C and −10.0 °C, females were more cold-hardy than males. About 50% of the overwintering female population were able to survive temperatures as low as −20 °C and monthly temperature fluctuations as great as 30 °C. None of the overwintering females was able to survive 48 h of −25 °C. Adult females of P. fuscatus are able to survive a winter temperature regime that, because of a combination of large fluctuations and low temperatures, is among the most severe reported for any adult insect.
Kin-selection theory (Hamilton's "genetical theory") explains how aid that is self-sacrificing (in terms of classical individual fitness), or "altruism," can evolve if sufficiently beneficial to relatives. It is discussed here in order to clarify the meaning of kin selection and inclusive fitness (the total reproductive valve of an individual, both its production of offspring and effects on the reproduction of relatives). Hamilton's condition K > 1/r, the relationship of benefit/cost and relatedness necessary for advantageous altruism, is reformulated so as to be applicable to altruism by descendents, and from the point of view of any member of a population (e.g., affected parties other than the altruist). A General expression is derived which defines inclusive fitness in terms of a classical and a kinship component. A unit of inclusive fitness-"offspring equivalents"-is defined. An index of the liklihood that altruism will occur in different social and ecological situations. K1, is employed to evaluate c...
1.1. Overwintering queens of the bald faced hornet, Vespula maculata, are tolerant of ice formation in their body fluids down to temperatures of approximately — 14°C.2.2. Contributing to this frost tolerance is a high concentration of the cryoprotectant glycerol in the overwintering queens. An additional factor is the presence in the hemolymph of macromolecular ice nucleating agents which function to induce harmless extracellular ice formation at comparatively high temperatures (−4.6°C), and thereby prevent lethal intracellular ice formation.3.3. These ice nucleating agents have molecular weights greater than 3500 and are probably proteinaceous.
SUMMARY Optimization of separation of carbohydrates and polyhydric alcohols on a silica column modified with tetraethylenepentamine is described. Eluent tetraethyl- enepentamine concentration, pH, solvent concentration and flow-rate were optimized with respect to compound separation and baseline stability. This method offers ad- vantages over existing techniques, including room temperature operation, low oper- ating pressure, low cost, simplicity, high resolution, relatively lengthy column life. and high linear sample capacity.
The thermal fluctuations respective of heat gain and loss within decayed stump habitats were analyzed under controlled conditions. Overwintering arctic and near-arctic invertebrates resident to the taiga biome require prolonged periods of thermostable exposures to insure complete development. One habitat type, decayed wood, offers a suitable winter hibernaculum.
Decayed stumps act to dampen variations in ambient temperatures due to insulative properties. The porous wood is water saturated and those temperature changes occurring above and below 0°C permit the hibernaculum to be viewed as an aqueous system. Stumps warm to thawing at a rate twice that of cooling to freezing over the same temperature range due to the specific heats and thermal conductivities of the water-ice phases.
These factors allow for the extension of developmental processes into autumn by low temperature buffering, but also provide the hibernaculum with rapid thawing (warming) characteristics for spring emergence.
1.
Polistes exclamans populations in central Texas have a unique colony cycle. Of all P. exclamans nests 20%–38% produce males with the first brood of workers. Nests producing early males have significantly more females, cells, pupae, and emergences at the time of early male production than nests not producing early males.
2.
Early male production may have originated as an adaptation caused by the large number of queens that die before autumn reproductive males and females are produced. It allows egg laying by workers with whom early males mate.
3.
Queens or workers sometimes leave their original nest and start new nests nearby that must be joined by workers from the original nest if they are to succeed. Such satellite nests were initiated from May to July by 16%–39% of all nests, depending on the population. Although nests initiating satellites have significantly more females and pupae than nests not initiating satellites, satellite nest production by a given nest is not dependent on prior early male production, and is independent of the number of foundresses.
4.
More P. exclamans nests 1976–1979 were lost to birds than to any other cause. In the period 1976–1979, 66.7% of the 12 nests with satellites succeeded in producing reproductives after being knocked down while only 5.7% of the 87 nests without satellites that were knocked down were subsequently successful. Concealed nests are less vulnerable to bird predation.
5.
The brood parasitoid, C. iphitalis, a pyralid moth, avoids previously infested nests, therefore satellite nesting does not reduce the impact of this parasitoid. However, the brood parasitoid E. polistis, a chalcid wasp, lays eggs in the nest it emerges from, hence a satellite nest provides an escape when this parasitoid is already in the main nest.
1.
Autumnal nest populations ofPolistes exclamans include externally indistinguishable workers and future queens. Qualitative as well as quantitative caste differences were found in the parietal fat body.
2.
An interesting correlation exists between the type of fat body and amount of eye pigmentation in females of this species.
3.
The frequency of transfer of marked males between nests was found to be very low.
4.
Polistes exclamans is unusual among North American members of its genus in that it appears to be almost completely haplometrotic in parts of its range. This may be evolutionarily connected with the species' comparatively greater vagility and tendency to disperse. Nest dispersal may reduce the rate of parasitism.
Two populations of the gall fly Eurosta solidaginsis utilize different strategies to endure seasonal exposure to temperatures below freezing. Both populations are freezing tolerant. In north temperate populations, supercooling points rise from −10.2°C to −6.2°C following exposures to temperatures below freezing. This level is maintained throughout winter and ensures frequent and prolonged periods of tissue freezing. South temperate populations depress the supercooling point to −14.2°C during autumn and early winter, and this depression precludes extracellular ice formation during periods of supra-optimal temperature fluctuations. During mid-winter, supercooling points rise to the same level as in northern groups.Both populations accumulate three principal cryoprotective agents following first frost exposures (glycerol, sorbitol and trehalose). Cryoprotectants levels do not peak in northern populations until 4–6 weeks after first frost. In southern populations the accumulation profile is characterized by a high initial rate of synthesis, a protective overshoot and pronounced seasonal fluctuations. The relative survival advantages of each strategy are discussed.
We observed three naturally occurring Polistes exclamans nests in Austin, Texas for 139 h through a succession of 13 queens. Nine of the 13 replacement queens were the oldest individuals on the nest, forming a system of queen replacement that may be described as a gerontocracy. Before becoming queen, replacement queens foraged more and were more aggressive than females who never became queen. This system of old forager supersedure was similar to that found in other temperate species but contrasted with that reported for tropical species of wasps in which younger females who are not workers occupy the higher ranks just beneath the queen.
1.1. Seasonal changes in cold-hardiness of three terrestrial Antarctic arthropods were investigated.2.2. Field microhabitat temperatures decreased from means of 11.2 in early February to 0.8°C by the end of March; this period represents a transition from austral mid-summer to autumn.3.3. Concurrent with microhabitat cooling, two freezing susceptible species, a mite, Alaskozetes antarcticus, and a collembolan, Cryptopyyus antarcticus, increased hardiness by depressing supercooling points (SCP) and accumulating cryoprotectants.4.4. The freezing tolerant chironomid, Belgica antarctica, increased SCPs from −10.2 to -5.0°C while attaining final cryoprotectant concentrations of 11.4/jg/mg (trehalose) and 7.0μg/mg (glucose).
DISSERTATION (PH.D.)--THE UNIVERSITY OF MICHIGAN Dissertation Abstracts International,
Thesis (Ph. D.)--University of Michigan, 1979. Bibliography: leaves 221-231. Microfiche.
http://deepblue.lib.umich.edu/bitstream/2027.42/56384/1/MP140.pdf
Polistes annularis females store honey in their nests in autumn. They return to their nests on warmn winter days, eat honey, and defend itfrom non-sisters. Honey deprivation decreases numbers surviving the winter; females that do survive without honey build smaller spring nests.
Notes on some feeding and hibernation habits of California Polistes (Hymenoptera: Vespidae). Pan-Pac. Ent., 43, 30The role of ice nucleators in the frost tolerance of overwintering queens of the bald-faced hornet
- J G Dvrg~y
- J L Pntrerson
Insect Physiol., 28, 431-436. BOUART G.E., 1942. --Notes on some feeding and hibernation habits of California Polistes (Hymenoptera: Vespidae). Pan-Pac. Ent., 43, 30. Dvrg~y J.G., PnTrERSON J.L., 1978. --The role of ice nucleators in the frost tolerance of overwintering queens of the bald-faced hornet. Comp. Biochem. Physiol., 59 A, 69-72.
The cohibernation and mating activity of five polistine wasp speciesJ
- H R Hermann
- D Gerling
- T F Dirks
- H. R. Hermann
At the end of the season withPolistes rubiginosus (Hym.: Vespidæ)
- P Rau
- P. Rau
— Notes on nesting and hibernation ofPolistes (Hymenoptera: Vespidæ)
- R C Snelling
Autumn and spring in the life of the queenPolistes annularis andP. pallipes
- P Rau
- P. Rau
Overwintering ofPolistes fuscatus in Canada: use of abandoned nests ofDolichovespula arenaria
- D L Gibo
- D. L. Gibo
Separation of carbohydrates and polyols by a radially compressed HPLC silica column modified with TEPA
- D L Hendrix
- R E Lee
- James H Jr
- J G Baust
- D. L. Hendrix
Hibernation sites and temperature tolerance of two species ofVespula and one species ofPolistes (Hymenoptera: Vespidæ)
- D L Gibo
- D. L. Gibo