Recent advances in understanding the molecular bases of insect polyphenisms the expression of a polyphenism begins when one or more signals are transduced into physiological or cellular responses that result in a developmental switch. Polyphenism a window into geneenvironment interactions. Proximate mechanisms and evolution of caste polyphenism in. Ultimately, the evolution of caste polyphenism thus required concerted evolution of environmental input signals and corresponding developmental responses. Insects represent over half of the planets biological diversity.
Evidence has accumulated over several decades to prove the kin selection theory of evolution of social insects, however, proximate mechanisms of social behavior, andor caste differentiation remain obscure. When polyphenic forms exist at the same time in the same panmictic interbreeding population they can be compared to genetic polymorphism. Indian agricultural research institute, division of entomology pp 487498. The recent development of genomic and metabolomic tools and resources has furthered our understanding of the molecular basis of phase change in locusts. For example, crocodiles possess a temperaturedependent sex determining polyphenism, where sex is the trait influenced by variations in nest temperature. Gene expression and the evolution of insect polyphenisms. Both male and female soapberry bugs can be long or short winged and the phenotype isnt determined until adulthood. Frontiers polyphenism a window into geneenvironment. Polyphenism in insects and the juvenile hormone springerlink. Densitydependent phase polyphenism in nonmodel locusts. Proximate mechanisms and evolution of caste polyphenism in social insects. A common feature of both shortterm and longterm effects is that they are graded, dependent not only on density but also on the duration and on phase history of the maternal generation.
Here we provide a brief overview of some key aspects of caste determination and differentiation in honey bees and termites figure 5, two phylogenetically divergent eusocial taxa. Evolution of social insect polyphenism facilitated by the. Stinging or venomous insects and related pests 5 hornets, yellow jackets, and paper wasps are social insects, and their colonies develop in a similar way. Polyphenism simple english wikipedia, the free encyclopedia. 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. In this new fourth edition, the authors introduce the key features of insect structure, function, behavior, ecology and classification, placed within the latest ideas on insect evolution. Many cases have been reported in insects, for example, metamorphosis, seasonal polyphenism, the caste of eusocial insects and so on. Polyphenisms are adaptations in which a genome is associated with discrete alternative phenotypes in different environments. Department of biology, graduate school of arts and sciences, university of tokyo, 3. The redshouldered soapberry bug is unique in that it exhibits two distinct wing morphs. Control mechanisms of polyphenic development in insects. Polyphenism has been key to the evolution of the hymenoptera, and particularly the social hymenoptera where the genome of a single species regulates distinct larval stages, sexual dimorphism and.
The caste system of social insects is the division of labor between genetically identical individuals. Polyphenism determines whether larvae develop into queens, workers, and in some cases soldiers. The naked mole rat eusocial phenotypic plasticity, whose phenotypes are still malleable after adulthood, is reminiscent of seasonal phenotypic plasticities in coat colors of arctic animals and in antler growth. Their numbers are nothing short of remarkable both in terms of how many individual insects there are, as well as how many species of insects there are. Frederik nijhout department of biology, duke university, durham, nc 27708, usa correspondence email. Development and evolution of adaptive polyphenisms h. Molecular mechanisms of phase change in locusts annual. Insects have even recruited polyphenism to partition labour within social groups, leading to some of the most successful animals on the planet, the eusocial insects. Insect polyphenisms center around four major themes.
Pdf polyphenism in insects 2011 current biology nathan. We show that the expression of several genes within the network is conserved in the winged castes of four ant species. We show that the expression of several genes within the network is conserved in the winged castes of four ant. Evolution of a polyphenism by genetic accommodation science. Request pdf polyphenism in insects polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Genes that regulate these mechanisms are apparently selected through kin selection, and organisms have consequently acquired sociality. Insects respond to crowding in a variety of ways that are usually exemplified by rapid changes in behavior and culminate in enduring longterm morphological andor chromatic responses. The solid lines represent idealized juvenile hormone jh titers during larval development, leading to either. Examples of polyphenism provide some of the most compelling systems for the study of epigenetics. Polyphenic insects phenotype university of arizona. Nijhout, 1989, juvenile hormone controls the onset of pupal commitment in the imaginal disks and epidermis of precis coenia lepidoptera. A reversible color polyphenism in american peppered moth. Evolution of the gene network underlying wing polyphenism in ants.
Muraleedharan d 2003 strategies and prospects of endocrinebased biotechnological approaches in insect pest management. Harmful insects molting is the process by which insects grow. As for all organisms responding to day length, aphids require a photoreceptor system that can distinguish light from dark, a clock mechanism that can measure the duration of the light or in most cases the dark period, a counter or photoperiodic memory that accumulates the number of long or. Couzin1, abstract during outbreaks, locust swarms can contain millions of insects travelling thousands of kilometers while devastating vegetation and crops. In fact, there are so many insects that no one knows quite how to count them all the. The adaptive importance of polyphenisms has been demonstrated in many cases, and many studies have shown that the threshold for the switch between alternative phenotypes can evolve. Social insects provide some of the most fam i l i a r a n d s p e c t a c u l a r e x a m p l e s o f polyphenism, where two or more distinct phenotypes are produced by the same genotype nijhout. Go to the tab that best exemplifies the damage observed on. Polyphenism may be continuous, as in the cyclomorphosis of freshwater organisms and some other seasonal. Insects are one of the most successful classes on earth, reflected in an enormous species richness and diversity. Sword2, and nathan lo1 polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. A polyphenism is a biological mechanism that causes a trait to be polyphenic.
Polyphenism, which is the ability of a single genome to produce two or more alternative morphologies in response to an environmental cue, is an ecologically important and phylogenetically widespread feature of plants and animals 1. Evolution of social insect polyphenism facilitated by the sex. Thousands of phaserelated genes and metabolites have been highlighted using. Eusociality has evolved at least twice within the hymenoptera 14, but we presently lack a wellevidenced theory of the genetic mechanisms that allowed castespecific gene expression to. Densitydependent polyphenism in locusts 1001 words 5 pages. Seasonal polyphenism insect physiology at illinois. Jul 12, 2002 wing polyphenism in ants evolved once, 125 million years ago, and has been a key to their amazing evolutionary success. Little is known about the mechanism by which polyphenisms originate. Seasonal polyphenism in insects results in a variation in phenotype of an insect based on a predictable environmental change. Wing polyphenism in ants evolved once, 125 million years ago, and has been a key to their amazing evolutionary success. The wing length polyphenism of the water strider aquarius paludum and the pupal color polyphenism of p.
Interplay between insulin signaling, juvenile hormone, and. An extreme case is found in social insects, in which reproductive queens and sterile workers that greatly differ in morphology and behavior can arise from a single genotype. Polyphenism has been key to the evolution of the hymenoptera, and particularly the social hymenoptera where the genome of a single species regulates distinct larval stages, sexual. Polyphenism is conserved in species from insects to nematodes, and evidence is mounting that it extends into many mammalian species. There are more species of insects than there are species of all other animals combined. Insects insecta are the most diverse of all animal groups. Insect body color polyphenisms enhance survival by producing crypsis in diverse backgrounds. Predictability of the change is important insects cannot readily modify phenotype in response to climate change, but can react to seasonal changes in temperature or photoperiod and adapt to better suit the season. In social insects, for instance, larval diet influences the development into distinct castes. Fully revised, this fifth edition opens with a chapter concerning the popular side of insect studies, including insects in citizen science. We show that a mutation in the juvenile hormoneregulatory pathway in manduca sexta enables heat stress to reveal a hidden reaction norm of larval coloration.
Densitydependent physiological phase in insects annual. Arguably, this success is partly due to the high degree to which polyphenism, where one genotype gives rise to more than one phenotype, is exploited by many of its species. Not all insects cause damage and many benefit your garden. Polyphenism is discontinuous when definite castes are present certain social insects or definite stages in the life cycle larvae vs. There are several types of polyphenism in animals, from having sex determined by the environment to the castes of honey bees and other social insects. We characterized the expression of several genes within the network underlying the wing primordia of reproductive winged and sterile wingless ant castes. Sometimes a magnifying glass or a microscope is needed. Caste polyphenism is at the heart of the extraordinary ecological success of eusocial insects, and has attracted great interest since the 19 th century. View the article pdf and any associated supplements and figures for a.
Pdf control mechanisms of polyphenic development in insects. Polyphenism denotes that one genome produces two or more distinct phenotypes due to environmental inductions. Epigenetics and locust life phase transitions journal of. Polyphenism in insects can occur within a single individual over its life time sequential in successive generations such as seasonally in individuals in the same generation as in social insects, parasitic wasp larvae a spectacular case of polyphenism within individuals larva pupa adult. Here we will leave aside insect developmental stages, and instead focus upon some of the archetypal examples of environmentally induced polyphenisms. Adult insects do not grow, and adult body size is determined by the processes that cause a larva to stop growing and initiate metamorphosis. The type of damage caused can provide evidence of the culprit. Although the specific mechanisms of locust phase transformation are wellunderstood for model locust species such as the desert locust schistocerca gregaria and the migratory locust locusta migratoria, the expressions of densitydependent phase polyphenism in other nonmodel locust species are not wellknown.
Understanding polyphenism, the ability of a single genome to express multiple morphologically and behaviourally distinct phenotypes, is an important goal for evolutionary and developmental biology. Polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Evolution of the gene network underlying wing polyphenism. View enhanced pdf access article on wiley online library html view. Structure and function of insects insects and wildlife. Model for the control of workersoldier polyphenism in the ant pheidole bicarinata. Examples of polyphenism abound in nature, from socially induced sex changes in thalassoma fish to seasonal changes in butterflies, but among the most astonishing forms of polyphenism are those that distinguish reproductive queens from nonreproductive workers individuals in ants. This established, popular textbook provides a stimulating and comprehensive introduction to the insects, the animals that represent over half of the planets biological diversity. Polyphenism is the phenomenon in which alternative phenotypes are producedby a singlegenotypeinresponse toenvironmentalcues. Polyphenism a window into geneenvironment interactions and. Phase change in locusts is an ideal model for studying the genetic architectures and regulatory mechanisms associated with phenotypic plasticity. Examples of polyphenism abound in nature, from socially induced sex changes in thalassoma fish to seasonal changes in butterflies, but among the most astonishing forms of polyphenism are those that distinguish reproductive queens from. This chapter discusses the complicated role of photoperiod in regulating life history traits in aphids.
Insofar as developmental and physiological processes obey the laws of chemistry and. Polyphenisms, such as the castes of social insects, the solitary and gregarious phases of migratory locusts, and the winged and wingless forms of aphids, are evolved adaptations to a varying environment. Polyphenism in insects polyphenism occurs in insects such as lepidoptera e. While color polyphenisms are often indirectly induced by temperature, rearing density, or diet, insects can benefit from immediate crypsis if they evolve polyphenisms directly induced by exposure to the background color, hence immediately deriving protection from predation.
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