Emery's rule is the trend of social parasites to be parasites to species or genera they are closely related to.

History

In 1909, the Italian entomologist

Carlo Emery Carlo Emery (25 October 1848, Naples – 11 May 1925) was an Italian entomologist. He is remembered for Emery's rule, which states that insect social parasitism (biology), social parasites are often closely related to their hosts. Early in hi ...

noted that social parasites among insects (e.g.,

kleptoparasite Kleptoparasitism (originally spelt clepto-parasitism, meaning "parasitism by theft") is a form of feeding in which one animal deliberately takes food from another. The strategy is Evolutionarily stable strategy, evolutionarily stable when stealin ...

s) tend to be parasites of species or genera to which they are closely related.Emery, C. "Über den Ursprung der dulotischen, parasitischen und myrmekophilen Ameisen". ''Biologisches Centralblatt'' 29, 352–362 (1909) Over time, this pattern has been recognized in many additional cases, and generalized to what is now known as Emery's rule.

In nature

The pattern is best known for various

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

Hymenoptera Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typi ...

. For example, the social wasp '' Dolichovespula adulterina ''parasitizes other members of its genus such as ''

Dolichovespula norwegica The Norwegian wasp (''Dolichovespula norwegica'') is a species of eusocial wasp. It is common in Scandinavia and can also be found in Scotland and other areas in Britain and Ireland. Often known for being a tree wasp, it nests in low branches a ...

'' and '' Dolichovespula arenaria''. Emery's rule is also applicable to members of other kingdoms such as

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

red algae Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...

, and

mistletoe Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they ...

. The significance and general relevance of this pattern are still a matter of some debate, as a great many exceptions exist, though a common explanation for the phenomenon when it occurs is that the parasites may have started as facultative parasites within the host species itself (such forms of intraspecific parasitism are well-known, even in some species of bees), but later became reproductively isolated and split off from the ancestral species, a form of

sympatric speciation Sympatric speciation is the evolution of a new species from a surviving Common descent, ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, ''sympatric'' and ''sympatry'' are ter ...

. When a parasitic species is a

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to its host in a

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

sense, the relationship is considered to be in "strict" adherence to Emery's rule. When the parasite is a close relative of the host but not its sister species, the relationship is in "loose" adherence to the rule.Hines, H. M., & Cameron, S. A. (2010)
The phylogenetic position of the bumble bee inquiline ''Bombus inexspectatus'' and implications for the evolution of social parasitism.
''Insectes Sociaux'', 57(4), 379–383.

References

{{Biological rules Parasitology 1909 introductions Biological rules 1909 in biology