Acromyrmex ameliae
Encyclopedia
Acromyrmex ameliae is a species
of New World ants of the subfamily Myrmicinae
of the genus
Acromyrmex. This species is from one of the two genera of advanced attines
(fungus-growing ants) within the tribe Attini. It is found in the wild naturally in South America
in Minas Gerais
, Brasil.
within the tribe Attini.
Acromyrmex can be identified from the closely related Atta genus
of leafcutter ants since they have 4 pairs of spines and a rough exoskeleton on the upper surface of the thorax
.
Like Atta, Acromyrmex subsists mostly on a particular species of fungus (genus Leucocoprinus
) which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen
and other colony members that remain in the nest. The media workers also gain subsistence from plant sap they ingest whilst physically cutting out sections of leaf from a variety of plants.
Acromyrmex exhibit a high degree of biological polymorphism
, four castes being present in established colonies - minims (or "garden ants"), minors, mediae and majors. Majors are also known as soldiers or dinergates. Each caste has a specific function within the colony. Acromyrmex ants are less polymorphic than the other genera of leafcutter ants Atta, meaning that there is comparatively less differential in size from the smallest to largest types of Acromymex. The high degree of polymorphism in this genus is also suggestive of its high degree of advancement.
Acromyrmex ameliae is a social parasite with much smaller reproductives (females and males) than those of its hosts Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus brunneus . Morphometrically, the Acromyrmex ameliae queen is not a simple miniature of its hosts' queens, like Myrmica microrubra and its host Myrmica rubra
. The species can be distinguish from the host using its propodeal
spines
: they are straight and laterally compressed unlike subterraneus subspecies where they are slight to strongly curved and conical. Acromyrmex ameliae differs from Acromyrmex insinuator
(another social parasite) not only by its size and color (brown dark against yellowish-orange) but as well it does not present a single strong median ruga extending from the central ocellus to the level of the posterior borders of lateral ocelli, like A. insinuator. On the contrary, around its central ocellus, the cuticle is wholly rugous without a distinct median ruga. In A. insinuator the anteroventral edge of the postpetiole is broadly and evenly concave, without a broad median anteroventral extension. The anteroventral portion of the post-petiole in A. ameliae has irregular extensions, without the concavity present in the first species.
As in Acromyrmex insinuator, reproductives (females and males) of A. ameliae very much resemble the host species, although there has been a pronounced reduction in body size. From observations of nuptial flights that occurred in the laboratory it is suspected that a mating flight occurs in the wild but are yest to observed. Alate
parasites are found in two different seasons (April and October), unlike the host species, which has only a single synchronized nuptial flight per year in November and December. More than one nuptial flight each year could increase the likelihood of successful invasion of new colonies by A. ameliae. The well defined nuptial flight of the hosts is normally observed in November and December so that newly fertilized parasite A. ameliae queens (produced in April) can colonize established colonies of A. subterraneus subterraneus and A. subterraneus brunneus well before they reproduce themselves.
Like A. insinuator, A. ameliae is one of the rare inquiline parasites that produces workers and resembles its host in morphology, but unlike A. insinuator, A. ameliae queens differ dramatically from their host queen in size. In all colonies of A. subterraneus sampled in A. ameliae range it was found that all of them where parasitized by A. ameliae. Thus, A. ameliae appears to be very common, yet until recently has been overlooked, suggesting the possibility that many other species of social parasitic exist that have yet to be identified.
As in A. insinuator, Acromyrmex ameliae produce a workforce that is essential for the production of the parasite alates, but this trait is being selected against over evolutionary time, although it has not yet been lost.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of New World ants of the subfamily Myrmicinae
Myrmicinae
Myrmicinae is a subfamily of ants. There are about 140 genera within the group, with the family being cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Acromyrmex. This species is from one of the two genera of advanced attines
Fungus-growing ants
The fungus-growing ants comprises all the known fungus-growing ant species in the world participating in ant-fungus mutualism. Leafcutter ants, including Atta and Acromyrmex, make up 2 of the genera.-See also:...
(fungus-growing ants) within the tribe Attini. It is found in the wild naturally in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
in Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
, Brasil.
Overview
Commonly known as "leaf-cutter ants" they are a species of ant from one of the two genera of advanced attinesFungus-growing ants
The fungus-growing ants comprises all the known fungus-growing ant species in the world participating in ant-fungus mutualism. Leafcutter ants, including Atta and Acromyrmex, make up 2 of the genera.-See also:...
within the tribe Attini.
Acromyrmex can be identified from the closely related Atta genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of leafcutter ants since they have 4 pairs of spines and a rough exoskeleton on the upper surface of the thorax
Thorax (insect anatomy)
The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....
.
Like Atta, Acromyrmex subsists mostly on a particular species of fungus (genus Leucocoprinus
Leucocoprinus
Leucocoprinus is a genus of fungi in the family Agaricaceae. Its best known member is the yellow pot-plant mushroom , found worldwide. The type species is Leucocoprinus cepistipes...
) which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen
Eusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
and other colony members that remain in the nest. The media workers also gain subsistence from plant sap they ingest whilst physically cutting out sections of leaf from a variety of plants.
Acromyrmex exhibit a high degree of biological polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
, four castes being present in established colonies - minims (or "garden ants"), minors, mediae and majors. Majors are also known as soldiers or dinergates. Each caste has a specific function within the colony. Acromyrmex ants are less polymorphic than the other genera of leafcutter ants Atta, meaning that there is comparatively less differential in size from the smallest to largest types of Acromymex. The high degree of polymorphism in this genus is also suggestive of its high degree of advancement.
Acromyrmex ameliae is a social parasite with much smaller reproductives (females and males) than those of its hosts Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus brunneus . Morphometrically, the Acromyrmex ameliae queen is not a simple miniature of its hosts' queens, like Myrmica microrubra and its host Myrmica rubra
Myrmica rubra
Myrmica rubra, also known as the European fire ant or common red ant, is a species of ant of the genus Myrmica, found all over Europe and in some parts of North America and Asia. They are mainly red in colour, with slightly darker pigmentation on the head. The ants live under stones, fallen trees,...
. The species can be distinguish from the host using its propodeal
Propodeum
The propodeum is the first abdominal segment in Apocrita Hymenoptera . It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is strongly constricted posteriorly to form the articulation of the petiole, and gives apocritans...
spines
Spine (zoology)
A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin...
: they are straight and laterally compressed unlike subterraneus subspecies where they are slight to strongly curved and conical. Acromyrmex ameliae differs from Acromyrmex insinuator
Acromyrmex insinuator
Acromyrmex insinuator is a species of leaf-cutter ant, a New World ant of the subfamily Myrmicinae of the genus Acromyrmex. This species is from one of the two genera of advanced attines within the tribe Attini....
(another social parasite) not only by its size and color (brown dark against yellowish-orange) but as well it does not present a single strong median ruga extending from the central ocellus to the level of the posterior borders of lateral ocelli, like A. insinuator. On the contrary, around its central ocellus, the cuticle is wholly rugous without a distinct median ruga. In A. insinuator the anteroventral edge of the postpetiole is broadly and evenly concave, without a broad median anteroventral extension. The anteroventral portion of the post-petiole in A. ameliae has irregular extensions, without the concavity present in the first species.
As in Acromyrmex insinuator, reproductives (females and males) of A. ameliae very much resemble the host species, although there has been a pronounced reduction in body size. From observations of nuptial flights that occurred in the laboratory it is suspected that a mating flight occurs in the wild but are yest to observed. Alate
Alate
An alate is a winged reproductive of a social insect . Alate females are typically those destined to become queens , whereas alate males are occasionally referred to as "drones"...
parasites are found in two different seasons (April and October), unlike the host species, which has only a single synchronized nuptial flight per year in November and December. More than one nuptial flight each year could increase the likelihood of successful invasion of new colonies by A. ameliae. The well defined nuptial flight of the hosts is normally observed in November and December so that newly fertilized parasite A. ameliae queens (produced in April) can colonize established colonies of A. subterraneus subterraneus and A. subterraneus brunneus well before they reproduce themselves.
Like A. insinuator, A. ameliae is one of the rare inquiline parasites that produces workers and resembles its host in morphology, but unlike A. insinuator, A. ameliae queens differ dramatically from their host queen in size. In all colonies of A. subterraneus sampled in A. ameliae range it was found that all of them where parasitized by A. ameliae. Thus, A. ameliae appears to be very common, yet until recently has been overlooked, suggesting the possibility that many other species of social parasitic exist that have yet to be identified.
As in A. insinuator, Acromyrmex ameliae produce a workforce that is essential for the production of the parasite alates, but this trait is being selected against over evolutionary time, although it has not yet been lost.