Ontogenetic niche shift (abbreviated ONS) is an

ecological Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

phenomenon where an organism (usually an animal) changes its

diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

during its

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...

(development). During the ontogenetic niche shifting an

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

of an individual changes its breadth and position. The best known representatives of taxa that exhibit some kind of the ontogenetic niche shift are

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

(e.g.

migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...

of so-called

diadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

fish between

saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

and freshwater for purpose of breeding),

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

(e.g. metamorphosis between different life stages; such as

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

and

imago In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the imaginal stage, the stage in which the insect attains maturity. It follows the f ...

) and amphibians (e.g. metamorphosis from

tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found ...

to adult frog). A niche shift is thought to be determined

genetically Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar working i ...

, while also being irreversible. Important aspect of the ONS is the fact, that individuals of different stages of a

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...

(e.g. of various age or size) utilize different kind of resources and habitats. The term was introduced in a 1984 paper by biologists Earl E. Werner and James F. Gilliam.

Characteristics

The ontogenetic niche shift is thought to be determined

, while also being irreversible. In complex natural systems the ONS happens multiple times in lifetime of an individual (in some examples the ontogenetic niche shifting can occur continuously). The ontogenetic niche shift varies across species; in some it is hardly visible and gradual (for example a change in diet or in size in

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

and reptiles), while in others it is obvious and abrupt (the metamorphosis of insects, which often results in changing habitat, diet and other ecological conditions). One of the studies suggests that differences in the ONS across species could be (at least to some degree) explained by diversity of traits and functional roles of a species. As a consequence differences in ontogenetic niche shifting are thought to follow some general patterns.

Importance

For communities

It is thought that almost every organism shows some kind of ontogenetic niche shift. The ONS, which is responsible for causing a noticeable

phenotypic variation In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

among individuals of the same species, plays important role in structuring communities and influencing their inside dynamics. In some cases individuals undergoing the ONS, in which they change their habitat, become a (mobile) link between two different communities (for example via flow of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...

and

nutrients A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...

). A stage structure of a

can result in various stages interacting with different representatives of a community or even with individuals of other communities, thus having a distinct ecological role from other life-history stages of the same population. Theoretical models, where communities are stage-structured, propose the ontogenetic niche shifting of studied organisms is influencing the whole community (especially its resilience and disturbance responses).

For population

The most apparent consequence of the ontogenetic niche shifting is a reduction of

competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indiv ...

between different stages of the same population. Because of the ONS individuals of different age or size do not compete for food, materials and other habitat resources. Different stages of the same population also have different

trophic Trophic, from Ancient Greek τροφικός (''trophikos'') "pertaining to food or nourishment", may refer to: * Trophic cascade * Trophic coherence * Trophic egg * Trophic function * Trophic hormone * Trophic level index * Trophic level ...

effects on

food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one o ...

of a community. A division of a population on distinct life-history stages is useful and evident, when there is a lack of resources for one stage (for example when juveniles do not get enough resources for themselves). In that case a lacking stage will have higher

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...

. The ONS is of great importance for survival of populations. Researchers noticed that many species exhibit the ontogenetic niche shifting at different times and in a lot of examples the ONS occurred as a response to various

abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...

and biotic environmental factors. It is thought that the ontogenetic niche shift could be an adaptive response to changing conditions in individual's habitat. Authors of the

life history theory Life history theory is an analytical frameworkVitzthum, V. (2008). Evolutionary models of women's reproductive functioning. ''Annual Review of Anthropology'', ''37'', 53-73 designed to study the diversity of life history strategies used by differen ...

predicted that organisms can affect the time of their ontogenetic niche shifting. While individuals living in favorable conditions would usually delay their ONS to successive ecological niche, organisms living in a niche with poor conditions typically advance to a further niche. Understanding the ontogenetic niche shifting in different species and its impact on the whole community is important when studying a

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

and

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

functioning. It is thought to be useful when dealing with populations threatened by anthropogenic disturbances and environmental changes.

Representative taxa

Even though the occurrence of ontogenetic niche shifting is thought to be widely distributed, the best known representative taxa with extensively studied ONS are insects and a few groups of

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

, especially fish and amphibians, where individuals often change their

as well as a lot of other aspects of their niche during the development. The less pronounced ontogenetic niche shifting can be seen in many other taxa, where their habitat stays the same. Usually the ONS in those species is evident, when looking at resources being used by organisms of the same species but various ages or size classes (for example a change in their diet).

Invertebrates

The ontogenetic niche shifting, which is connected with extreme habitat changes, can be seen among

. Individuals of taxon Insecta are known to exhibit one of the various types of metamorphosis, the best studied being

hemimetabolism Hemimetabolism or hemimetaboly, also called incomplete metamorphosis and paurometabolism,McGavin, George C. ''Essential Entomology: An Order-by-Order Introduction''. Oxford: Oxford University Press, 2001. pp. 20. is the mode of development of certa ...

(where an insect passes three life stages;

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label= Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

and

) and holometabolism (characterized with four life stages of an insect; egg,

and imago). Nutritional niches and their shifting during a ontogeny can be accurately measured by using a stable

isotopic signature An isotopic signature (also isotopic fingerprint) is a ratio of non-radiogenic ' stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample ...

of animals. Such method has been used in studying the ONS in

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. The ...

, such as field

slugs Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a sma ...

Vertebrates

The ONS similar to that among insects happens in amphibian taxa, the best known being

frogs A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...

, which start as an egg and then hatch into a

larval stage A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

called the

. Tadpoles exhibit many differences that distinguish them from an adult stage of a frog; most species' tadpoles are aquatic, they usually possess

external gills External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes. Instead, the respiratory organs are set on a fril ...

and primarily feed with

plant material Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There ...

(even though there are some exceptions that consume dead animal flesh or mixed diet). Another well studied example of the ONS occurs in fish, that exhibit

behaviour. Diadromous fish species drastically change their habitat, when they set out on a journey from

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

(saltwater) to rivers (freshwater) and vice versa. A lot of freshwater fish species show the ONS in their diet, when they switch from preying on

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

to performing benthivory. The ONS may not be so visible in reptiles, even though these vertebrates do utilize it. The ontogenetic niche shifting was studied in American alligator (''

Alligator mississippiensis The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the gen ...

''), which is ideal for studying ecological aspects of ONS because of many distinct size stages in a population. Alligators were switching their habitat niche between hydrologically isolated, seasonal wetlands and riverine systems. The study has shown that riverine systems were populated primarily with adults and subadults of both

sexes Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones ( ova, of ...

, that used the area as a non-nesting habitat. On the other hand, juveniles and adult females were found on seasonal wetlands, which served as a nursery and nesting sites respectively. Good example of the ONS in birds are big

seabirds Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envi ...

, such as albatrosses, which spend some of their time as fully oceanic birds and when

sexually mature Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definiti ...

begin to visit breeding grounds. Immature juveniles usually stay in subtropical water, where they occupy high

trophic levels The trophic level of an organism is the position it occupies in a food web. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it i ...

. Researchers noticed that young birds progressively direct towards lower trophic positions when they are coming closer to sexual maturity. After time they take on an isotopic niche of an adult bird. The ontogenetic niche shifting is a concept widely studied in

paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

and

paleozoology Palaeozoology, also spelled as Paleozoology (Greek: παλαιόν, ''palaeon'' "old" and ζῷον, ''zoon'' "animal"), is the branch of paleontology, paleobiology, or zoology dealing with the recovery and identification of multicellular anima ...

. Large non-avian dinosaurs are known to have had exhibited one of the most intensive ontogenetic niche shifting, as they were hatched from an egg and had to experience big size shifts during their ontogeny. One of the problems, connected with understanding

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

dinosaur

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''Biota (ecology ...

was lack of so-called mesocarnivores. It is predicted the ontogenetic niche shift is an answer, because carnivorous dinosaurs started out as small

hatchlings In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar to ...

and progressed towards adult size, while occupying different successive niches and limiting trophic species diversity. Juvenile individuals of megatheropods are thought to occupy mesocarnivore niche.

Plants

The ontogenetic niche shifting is primarily studied in animals, but there are some studies that deal with the ONS in

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...

. One of the ONSs studied in plants is changing of a regeneration niche. Authors of the paper noticed that during the ontogeny the regeneration niche of ''

Acer opalus ''Acer opalus'', the Italian maple, is a species of maple native to the hills and mountains of southern and western Europe, from Italy to Spain and north to southern Germany, and also in northwest Africa in Morocco and Algeria.Flora Europaea''Ac ...

'', the Italian maple, had shrinked. It is thought such ontogenetic niche shift was mainly a consequence of

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

, the depth of the litter layer and presence of other plants (especially adult trees and shrubs).

References

{{Modelling ecosystems, expanded=other Developmental biology Ecological niche Evolutionary biology concepts