Seasonal Morphs Research Articles

Review of seasonal polyphenism in the Symphyta (Hymenoptera), exemplified by Pristiphora leucopus (Hellén, 1948) (Tenthredinidae)

Morphological differences between the adults of overwintering and non-overwintering generations of the sawfly Pristiphora leucopus (Nematinae) are described and illustrated, as well as characters that distinguish P. leucopus from the closely similar P. armata. In the basal hymenopteran lineages (‘Symphyta’), seasonal polyphenism is so far only definitely recorded in the Sterictiphorinae (Argidae) and Nematinae (Tenthredinidae) of the Tenthredinoidea. Within the Nematinae, seasonal polyphenism had previously only been described in Nematus bergmanni. Seasonal polyphenism in the basal hymenopteran lineages is reviewed, and the potential pitfall that the existence of seasonal morphs represents for taxonomists working on ‘Symphyta’ is highlighted. Voltinism patterns in the basal hymenopteran lineages are also reviewed, to indicate the likelihood of further undetected examples of seasonal polyphenism in the families and subfamilies. With rare exceptions, multivoltinism occurs mainly in the Tenthredinoidea and is most frequent in the Argidae and Tenthredinidae (particularly Allantinae, Blennocampinae and Nematinae).

Polyphenism in Insects

(Current Biology 21, R738–R749; September 27, 2011) The authors wish to make an important clarification regarding the above review article on insect polyphenism. In the text we used a passage from Ernst Mayr's classic 1963 book [1Mayr E. Animal Species and Evolution. Belknap Press of Harvard University Press, Cambridge, MA1963Crossref Google Scholar] to help provide a historical context, noting that the study of phenotypic plasticity had fallen out of respectability and that with this statement Mayr helped return the subject to respectability. It has since come to our attention that our use of this passage could also be interpreted as a claim that Mayr coined the term “polyphenism.” This was certainly not our intention. As a point of fact, it was Charles Michener [2Michener C.D. Social polymorphism in Hymenoptera.Symp. R. Entomol. Soc. Lond. 1961; 1: 43-56Google Scholar], who first suggested the term “polyphenic” 2 years before Mayr's publication and should be credited with its origin. We greatly thank our colleague Meir Paul Pener for his keen attention to this matter. Polyphenism in InsectsSimpson et al.Current BiologySeptember 27, 2011In BriefPolyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Examples of polyphenism provide some of the most compelling systems for the study of epigenetics. Polyphenisms are a major reason for the success of the insects, allowing them to partition life history stages (with larvae dedicated to feeding and growth, and adults dedicated to reproduction and dispersal), to adopt different phenotypes that best suit predictable environmental changes (seasonal morphs), to cope with temporally heterogeneous environments (dispersal morphs), and to partition labour within social groups (the castes of eusocial insects). Full-Text PDF Open Archive

Polyphenism in Insects

Polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Examples of polyphenism provide some of the most compelling systems for the study of epigenetics. Polyphenisms are a major reason for the success of the insects, allowing them to partition life history stages (with larvae dedicated to feeding and growth, and adults dedicated to reproduction and dispersal), to adopt different phenotypes that best suit predictable environmental changes (seasonal morphs), to cope with temporally heterogeneous environments (dispersal morphs), and to partition labour within social groups (the castes of eusocial insects). We survey the status of research onsome of the best known examples of insect polyphenism, in each case considering the environmental cues that trigger shifts in phenotype, the neurochemical and hormonal pathways that mediate the transformation, the molecular genetic and epigenetic mechanisms involved in initiating and maintaining the polyphenism, and the adaptive and life-history significance of the phenomenon. We conclude by highlighting some of the common featuresof these examples and consider future avenues for research on polyphenism.

Phenotypic plasticity in butterfly morphology in response to weather conditions during development

In seasonal environments, phenotypic plasticity in response to gradual changes in environmental variables may result in the production of discrete seasonal morphs. Production of the appropriate seasonal morph at the correct time relies on individuals interpreting environmental cues during their development. The speckled wood butterfly Pararge aegeria (L.) has previously been shown to have developmental and phenotypic plasticity across seasons and space (habitats). Here, we examine the developmental sensitivity of different seasonal cohorts of female P. aegeria to changes in local weather conditions over time (1989–1999) and determine how such temporal climatic variation affects adult phenotype development. We observed trait- and cohort-specific changes of adult phenotype development in response to local temporal changes in temperature and rainfall levels. We discuss our findings using current life-history theory and consider the potential for changes in local weather conditions to influence population variability in butterfly morphology and performance.

An essay on seasonal morph research of butterflies

An essay on seasonal morph research of butterflies

Role of temperature and photoperiod in seasonal morph determination in the nymphalid butterfly Hestina assimilis assimilis inhabiting Kanagawa Prefecture, central Japan

Role of temperature and photoperiod in seasonal morph determination in the nymphalid butterfly Hestina assimilis assimilis inhabiting Kanagawa Prefecture, central Japan

Photophase influence on the reproductive diapause, seasonal morphs, and feeding activity of Euschistus heros (Fabr., 1798) (Hemiptera: Pentatomidae).

Laboratory studies were conducted to verify the influence of photophase on diapause incidence in the Neotropical brown stink bug, Euschistus heros (Fabr., 1798), fed with soybean [Glycine max (L.)] Merrill pods. Nymphs were maintained at three different photophases: 10 h, 12 h, and 14 h, with constant temperature of 25 +/- 1 degree C and relative humidity of 65 +/- 5%. With 14 h, approximately 100% of the adults showed mature reproductive organs; the shoulder (spine) length was significantly greater (2.96 and 2.79 mm for females and males, respectively) than those of bugs maintained at the photophase of 12 h (2.60 mm for females and males) and 10 h (2.59 and 2.53 mm for females and males). At the longer photophase (14 h), E. heros showed better reproductive performance and greater feeding activity than insects reared at 10 h and 12 h; in all photophases bugs tended to reduce feeding from the 1st to the 6th week of life. Body color was considered an unreliable parameter to indicate diapause incidence. However, at 14 h, 60% of the insects were dark brown and 40% were reddish brown. These results indicate that E. heros enters reproductive diapause with photophase of 12 hours or less, showing immature reproductive organs or with intermediate development, with shoulder (spine) less developed and reduced feeding activity.

Evidence for the Presence of the Summer-Morph-Producing Hormone in the Swallowtail Butterfly, Papilio xuthus L. (Lepidoptera: Papilionidae)

The swallowtail butterfly, Papilio xuthus L., exhibits seasonal diphenism, i.e., spring and summer morphs, the development of which is determined by photoperiod and temperature imposed during the larval stage. Larvae reared under long day conditions at 25°C develop into summer morphs without pupal diapause, while larvae reared under short day conditions at 20°C develop into spring morphs after diapause development at 4°C for more than three months. To investigate the neuroendocrine mechanism regulating seasonal morph development, the activity of the summer-morph-producing hormone (SMPH) was tried to assayed by using male short day pupae of P. xuthus that accomplished diapause development at 4°C. The wing patterns of male butterflies shifted toward summer morphs when short day pupae were treated with the SMPH at an adequate stage. SMPH activity was detected in 2% NaCl extracts of the brain-subesophageal ganglion (Br-SG) complexes of P. xuthus long day pupae. Chilled male short day pupae responded to P.xuthus SMPH in a dose-dependent manner and lost the responsiveness within 2 days of transfer to room temperature (about 25°C). This is a report to show the existence of SMPH in butterfly species having pupal diapause.

Sexual Isolation Between Two Sympatric Types of the Butterfly Eurema hecabe (L.)

In Japan, the butterfly Eurema hecabe (L.) consists of two separate types. These types differ in wing fringe color (brown or yellow), which is linked with expression of seasonal wing morphs and with ability for host-plant use. It was recently found that these two types occur together on the subtropical Okinawa-jima Island (one of the Ryukyu Islands). In the present work we studied whether sexual isolation may exist between these sympatric types of E. hecabe on Okinawa-jima, using caged conditions. When living females (days 0, 1, and 7) were presented to males of the same or different type, females of the brown type received males of the same type and responded with a refusal posture to those of the yellow type. Females of the yellow type received males of the same type at all ages tested. However, when they were exposed to males of the brown type, the proportion of females showing a refusal posture changed with female age. The proportion was high at day 7 but relatively low at day 0 or day 1. When model females of the brown and yellow types were simultaneously presented to males of each type, males courted not only the model females of the same type, but also those of the different type. The results suggest that (1) sexual isolation exists between these types of E. hecabe on Okinawa-jima, although it is not perfect; (2) this isolation is mediated by female recognition but not male recognition; and (3) the sexual isolation system between two types is asymmetrical, depending on the female age after adult eclosion.

Diapause and different seasonal morphs of Euschistus heros (Fabr.) (Hemiptera: Pentatomidae) in Northern Paraná State

The Neotropical brown stink bug, Euschistus heros (Fabr.), was collected on sunflower [Helianthus annuus (L.)], soybean [Glycine max (L.) Merrill], star bristle [Acanthospermum hispidum (DC.)], and under fallen leaves of mango tree [Mangifera indica (L.)] and privet (Ligustrum lucidum Ait.), during one year, to evaluate the diapause incidence and the occurrence of different seasonal morphs. The majority of the insects (ca. 90%) with mature reproductive organs was observed during the summer (December-March), when E. heros was found on soybean or on sunflower; in the beginning of autumn, most insects (87%) showed immature reproductive organs, and they were found on star bristle and under fallen leaves. Bugs with mature reproductive organs had more developed shoulders (3.23 and 3.27 mm, for males and females, respectively) than bugs with immature organs (2.91 and 2.89 mm, for males and females, respectively). Two distinct body colors, dark brown and reddish brown, were observed. Nevertheless, the reddish brown was the predominant color of both mature and immature adults during all year. Adults were parasitized by Hexacladia smithii (Ashmead) (Hymenoptera: Encyrtidae) and Tachinidae mainly Trichopoda giacomellii (Blanchard) (Diptera: Tachinidae) (80% and 40% of parasitism in male and female, respectively) during summer (December), when the bugs colonized sunflower. In soybean, 12% of males and 10% of females were parasitized, whereas in fallen leaves, the parasitism rate was 5% in both sexes.These results showed that in autumn/winter (shorter photoperiod) the majority of the insects were inactive under fallen leaves, showing immature reproductive organs and less developed shoulders, indicating that, at this time, these bugs were in diapause.

Overlapping Distribution of Two Groups of the Butterfly Eurema hecabe Differing in the Expression of Seasonal Morphs on Okinawa-jima Island

In Japan, Eurema hecabe (L.) has two geographically separated groups (subtropical and temperate) differing not only in the color pattern expression of the wings associated with ovarian arrest, but also in the fringe color of the wings and host-plant utilization. In a field survey (Kato, 1999), it was found that individuals with different fringe color of the forewing (brown or yellow type) inhabit Okinawa-jima Island located in north of the subtropical region, and that fringe-color is linked with seasonal morph expression. In the present study, rearing experiments were done to investigate whether these sympatric individuals are different forms within one species or belong to different species. The results show that each population of brown- and yellow-types maintained its own seasonal morph response to photoperiod and temperature through three generations. Host-plant utilization by the larvae and the fringe-color also differed between them and was maintained. These findings strongly suggest that E. hecabe of Okinawa-jima Island is divided into two distinct populations, and that one belongs to the temperate and the other to the subtropical group.

Neuroendocrine regulation of seasonal morph development in a bivoltine race (Daizo) of the silkmoth, Bombyx mori L.

We investigated the neuroendocrine regulation of the development of seasonal morphs in a bivoltine race (Daizo) of the silkmoth, Bombyx mori, by decerebration, the transplantation of brain–suboesophageal ganglion (Br-SG) complexes and the injection of active neuropeptides. When brains were removed from fresh pupae destined to develop into summer morphs (SD pupae) by embryonic and larval exposures to short days at low temperature, the pupae developed into autumn or intermediate morphs. However, in pupae destined to develop into autumn morphs (LD pupae), the operation did not show an effect on seasonal morph development. Br-SG complexes were excised from fifth-instar LD and fifth-instar SD larvae 2 days after larval ecdysis and were transplanted into the abdomen of SD larvae of the same age. The Br-SG complexes of LD larvae, but not the Br-SG complexes of SD larvae, shifted the host's seasonal morph development toward the autumn morph. Furthermore, when treated with crude pupal SGs extract and diapause hormone (DH), fresh SD pupae developed into autumn or intermediate morphs, respectively. Possibly the development of seasonal morphs in the silkmoth, B. mori, is regulated by a novel function of DH. Alternatively, DH may act on the imaginal wing disks at an earlier stage than on the ovaries.

Overlapping Distribution of Two Groups of the Butterfly Eurema hecabe Differing in the Expression of Seasonal Morphs on Okinawa-jima Island.

Overlapping Distribution of Two Groups of the Butterfly Eurema hecabe Differing in the Expression of Seasonal Morphs on Okinawa-jima Island.

Effects of photoperiod and temperature on seasonal morph development and diapause egg oviposition in a bivoltine race (Daizo) of the silkmoth, Bombyx mori L.

A bivoltine race (Daizo) of the silkmoth, Bombyx mori, has two types of adults which are classified on the basis of the number of dark-brown and brown scales distributed along the outer lines of the anterior wings. Development of these two types of adults is determined by photoperiod and temperature experienced during the embryonic and larval stages. The two types of adults are thought to be seasonal (summer and autumn) morphs. All adults developed under short days at low temperature (15°C and 23°) were classified as summer morphs and oviposited only nondiapause eggs (ND-eggs), and those that developed under long days at high temperature (28°C and 25°C) were autumn morphs ovipositing only diapause eggs (D-eggs), only ND-eggs or a mixture of D- and ND-eggs. Larval exposure to long days at 25°C shifted the wing pattern towards the autumn morphs and decreased the incidence of female adults ovipositing only D-eggs. Larval exposure to long days elicits an opposite effect on D-egg oviposition to that observed when long days are received only during the embryonic stage.

Genetic control of a seasonal morph in Precis coenia (Lepidoptera: Nymphalidae)

The seasonal color polyphenism of the buckeye butterfly, Precis coenia, is controlled by environmental and genetic factors. Environmental stimuli, such as photoperiod and tempertaure, alter the pattern of ecdysteroid secretion. If ecdysteroids are present during a critical period early in the pupal stage the pale beige linea form develops, while in the absence of ecdysteroids the dark reddish-brown sa form develops. In this paper we report on the isolation of a genetic strain that constitutively expresses the rosa phenotype. Breeding experiments show that this effect is due to a single recessive gene. The ecdysteroid titer profile of the rosa strain is identical to that of the environmentally induced linea form, and not to that of the environmentally-induced rosa form. Ecdysteroid injections and reciprocal wing imaginai disk transplant studies between genetic rosa and wild-type strains, show that the rosa gene does not affect the endocrine system, but alters the physiological response mechanism that follows the ecdysteroid-sensitive period for linea induction and culminates in the wing-specific synthesis of ommochrome pigments.

Morphological and Genetic Variability in Plantago cordata (Plantaginaceae), a Threatened Aquatic Plant

Morphological and genetic variation were studied in Plantago cordata Lam., an imperiled aquatic plant. The existence of distinct seasonal morphs was confirmed by numerical morphological analyses of specimens from 53 populations. Plants from two North Carolina populations possessed leaves that were significantly shorter, narrower, and fewer-veined than populations in other portions of the species range. Genetic variation within and among ten populations in seven states/provinces (Illinois, Missouri, New York, North Carolina, Ohio, Ontario, and Wisconsin) was examined electrophoretically. The species is an apparent allopolyploid with fixed heterozygosity observed at 67% of the loci surveyed. Electrophoretic variation was mostly partitioned among populations. The genetic identity among populations was high except for North Carolina populations which differed at 27% of the loci surveyed.

MORPHOLOGICAL AND GENETIC VARIABILITY IN PLANTAGO CORDATA (PLANTAGINACEAE), A THREATENED AQUATIC PLANT

Morphological and genetic variation were studied in Plantago cordata Lam., an imperiled aquatic plant. The existence of distinct seasonal morphs was confirmed by numerical morphological analyses of specimens from 53 populations. Plants from two North Carolina populations possessed leaves that were significantly shorter, narrower, and fewer‐veined than populations in other portions of the species range. Genetic variation within and among ten populations in seven states/provinces (Illinois, Missouri, New York, North Carolina, Ohio, Ontario, and Wisconsin) was examined electrophoretically. The species is an apparent allopolyploid with fixed heterozygosity observed at 67% of the loci surveyed. Electrophoretic variation was mostly partitioned among populations. The genetic identity among populations was high except for North Carolina populations which differed at 27% of the loci surveyed.

Seasonal plasticity in life history traits: growth and development in Polygonia c-album (Lepidoptera: Nymphalidae)

The potentially multivoltine comma butterfly, Polygonia c-album L., hibernates in the adult stage. The adult seasonal morph is demonstrated to be a good indicator of whether an individual has entered reproductive diapause or is developing directly to sexual maturation. This fact, and the assumption that a short development time is not equally important to all categories of individuals, was used to test predictions on variation in life-history traits among categories (morphs and sexes) and environments (temperature and photoperiod) at the level of individuals and to some extent families and populations (the univoltine Stockholm population and the partially bivoltine Oxford population). Individuals developing to adults in a short time were expected to be smaller and lighter as a result of a basic trade-off between the two traits. Development times varied in accordance with predictions, but in most cases this was due to plastic growth and development in both the larval and pupal stages rather than through variation in size or weight, i.e. size was a highly canalized trait. This suggests a relationship between plasticity and canalization and a strong potential for plasticity to shield life-history traits from selection. Individuals regulated development times also within developmental pathways, in response to photoperiods indicating the progression of the season. These and other results suggest that development times are not normally minimized in temperate butterflies unless this is enforced by direct development and protandry. There is thus scope for a high degree of adaptive plasticity in growth- and developmental rates which may devalue the basic trade-offs assumed by life-history theory and account for inconsistencies with its predictions.

Typification of Melissa calamintha L., M. nepeta L., and Thymus glandulosus Req. (Lamiaceae), with some systematic observations

SummaryGarbari, F., Jarvis, C. E. & Pagni, A. M.: Typification of Melissa calamintha L., M. nepeta L., and Thymus glandulosus Req. (Lamiaceae), with some systematic observations. ‐ Taxon 40: 499–504. 1991. ‐ ISSN 0040‐0262.Lectotypes are proposed for the basionyms of two taxa widely known under the designation of, e.g., Calamintha nepeta (L.) Savi subsp. nepeta and subsp. glandulosa (L.) P. Ball, and also for Calamintha officinalis Moench (≡ Melissa calamintha L.) usually treated as synonymous to the latter. New morpho‐anatomical and phytochemical studies suggest, however, that these are seasonal morphs rather than discrete taxa and that they do not deserve recognition, not at any rate at a supra‐varietal level.

Differences in reproductive behavior among seasonal wing morphs of the butterfly Eurema hecabe

Les comportements sexuels, de ponte et d'alimentation des adultes de E. h. varient selon la cohorte (automne ou ete) dont les individus possedent des morphismes differents.