Myrmecochory

Myrmecochory (mɜːrmᵻˈkɒkɔːri (sometimes myrmechory); from mýrmēks ("ant") and χορεία khoreíā ("circular dance") is seed dispersal by ants, an ecologically significant ant–plant interaction with worldwide distribution. Most myrmecochorous plants produce seeds with elaiosomes, a term encompassing various external appendages or "food bodies" rich in lipids, amino acids, or other nutrients that are attractive to ants. The seed with its attached elaiosome is collectively known as a diaspore. Seed dispersal by ants is typically accomplished when foraging workers carry diaspores back to the ant colony, after which the elaiosome is removed or fed directly to ant larvae. Once the elaiosome is consumed, the seed is usually discarded in underground middens or ejected from the nest. Although diaspores are seldom distributed far from the parent plant, myrmecochores also benefit from this predominantly mutualistic interaction through dispersal to favourable locations for germination, as well as escape from seed predation. Myrmecochory is exhibited by more than 3,000 plant species worldwide and is present in every major biome on all continents except Antarctica. Seed dispersal by ants is particularly common in the dry heath and sclerophyll woodlands of Australia (1,500 species) and the South African fynbos (1,000 species). Both regions have a Mediterranean climate and largely infertile soils (characterized by low phosphorus availability), two factors that are often cited to explain the distribution of myrmecochory. Myrmecochory is also present in mesic forests in temperate regions of the Northern Hemisphere (i.e. in Europe and in eastern North America), as well as in tropical forests and dry deserts, though to a lesser degree. Estimates for the true biodiversity of myrmecochorous plants range from 11,000 to as high as 23,000 species worldwide, or about 5% of all flowering plant species. Myrmecochory has evolved independently many times in a large number of plant families.