Thursday, October 9, 2014

Maryland Naturalist's Notes: Understanding Breeds, Species, and Domestication

How is a breed different from a species?  What makes an animal domesticated instead of tame? What makes an introduced plant invasive?

If you have trouble answering these questions, you are not alone!  As humans have bred, altered, and transported plants and animals around the globe, the relationship between their new and natural forms has been muddled and blurred.  Below is a little chart and glossary of terms to help you better define and understand how humans have changed the creatures who share our lives. 

A handy chart!  Click to view larger.

Species: Broadly speaking, a species is a population of organisms that shares a great deal of genetic similarity. Modern determinations of species typically use genetic material, occupation of specific niches, and evolutionary history as the primarily factors defining a species.

Examples of species: tiger, Grevy's zebra, African gray parrot, gray wolf, white oak, lowbush blueberry, scarlet beebalm
The Canada goose is a species of goose. 

Subspecies:  Subspecies are subgroups within species.  Typically, subspecies are capable of interbreeding with other members of their species to produce healthy, fertile offspring, but are prevented from doing so by factors such as geographic isolation or resource specialization. A similar designation often used with plants is a variety.

Examples of subspecies: Siberian tiger, grizzly bear, eastern milk snake, Hers maple, Rolfs milkweed

The eastern milk snake is a subspecies of milk snake.

Domesticated: Domesticated animals or plants have been artificially selected (bred) by humans over many generations to be physically and genetically different from their ancestral species.  For instance, domestic dogs are domesticated wolves, domestic horses are domesticated tarpans, and broccoli is a domesticated form of wild mustard.

More examples of domesticated organisms: domestic rat, housecat, dairy cow, chicken, American budgerigar, domestic honey bee, mustard, tomato, zucchini 

Moonbeam is a domesticated African pygmy goat.
Her wild ancestors were Eurasian wild goats.

Tamed: Tamed animals are behaviorally different from their naturally occurring forms in that they are well-acclimated human interaction or presence and are generally non-threatening to humans. The term "tamed" is considered archaic by many animal professionals, who often prefer to refer to these animals as socialized or habituated to humans.  Tamed animals are not significantly physically or genetically different from their wild ancestors - their tame behavior is the result of behavioral conditioning, not artificial selection. Therefore, "tame" wild animals are not domesticated.

Examples of tamed animals: a circus lion, a falconer's hawk, a pet macaw, a wolf used in educational programs, dolphins at a marine park
This box turtle used in educational programs is so well-socialized to humans,
it does not pull into its shell when picked up.  

Feral: Feral animals are domesticated animals who are not socialized or habituated to humans (in other words, they are not "tame"). The domesticated ancestors of feral animals were once used by humans, but due to escape, release, or simply a lack of conditioning, these animals do not willingly interact with humans.  Common examples of feral animals include the mustangs of North America, stray dogs and cats who are stressed by human presence, and your typical city pigeons.

More examples of feral animals: feral cats roaming neighborhoods, goats on Galapagos, Assateague Island ponies, Australian water buffalo, city pigeons, North American wild boar

A common sight in cities, pigeons are feral animals who originally descended from domestic homing pigeons.

Breed:  Breeds are a subgroup of a domesticated animal. Breeds have been artificially selected by humans to create distinctive forms of a domesticated animal that can by recognized by their physical appearance, behavior tendencies, and pedigree. Not all domesticated animals have breeds, but many of the earliest domesticated animals do, including dogs, cats, rabbits, horses, cows, chickens, sheep, goats, pigs, and even pigeons.

Examples of breeds: German shepherd, Persian cat, thoroughbred, Rhode Island red, Hereford cow

A pair of Indian runner ducks, one of many domestic duck breeds. 
Cultivar: Cultivar is short for "cultivated variety" and is essentially the plant version of an animal breed. As with breeds, cultivars are subgroups of plant species or varieties that are distinctive in appearance or habit, and reproduce true when propagated.

Examples of cultivars: Kwanzan cherry tree, Celebrity tomato, John Cline scarlet beebalm, Little Lanterns eastern red columbine

The 'Emerald Blue' cultivar of creeping phlox
Landrace: A landrace is a subgroup of a domesticated animal or plant that has not developed due to formal and directed selection by humans (as in a breed or cultivar) but due to isolation within a regional area.  Landraces develop due to the unique climatic and ecological factors within their region, and due to genetic isolation from other members of their species.  A landrace may develop entirely without any human selection, or with very low, informal selection by the humans in their locality.  Eventually, humans may establish standardized, formally managed breeds from their original landraces - these are sometimes called natural breeds.

Examples of landraces: Van cat, Florida cracker cattle, Assateague Island pony, Spanish goat, Gerdeh rice
Examples of natural breeds: Turkish Van cat, Egyptian Mau, Carolina dog, Shetland pony, many heirloom tomato cultivars
An Assateague Island pony
Ecovar: Among plants, an ecovar is created through the original selection of a wide variety of wild specimens.  Ecovars, while less genetically diverse than a wild population, are more diverse than most cultivars.  Ecovars can come from stock selected only within certain regions, allowing each ecovar to reflect the genetic traits found in certain ecological areas.  Ecovars are sometimes seen as intermediates between cultivars and wild species. Ecovars are typically named for the areas their original stock was harvested.

Examples of ecovars: Bad River blue grama, Itasca little bluestem

Little bluestem is a grass species often collected to develop ecovars.
Image public domain by Paul Fusco via

Native species: A native species is naturally found within a certain region, or has shifted or expanded its range due to natural influences or factors. Another term used to describe a species native to a region is indigenous. A species found naturally in one location and nowhere else is known as endemic.

Examples of native species: American bison in Montana, cheetahs in Namibia, redwoods in California, black cherry trees in Maryland, false monkey puzzle tree in Queensland

The New Zealand pigeon is endemic to New Zealand.

Introduced, or non-native, species: Introduced species have been relocated by humans to a region outside of their natural range, either intentionally or accidentally. They are also known as exotic, alien, or non-indigenous species. Once a species has spread outside of the confines of human care, it is known as an adventive non-native species.  If that adventive species then establishes self-sustainable populations, it can be said to be naturalized. Non-native species may or may not have adverse effects on the ecosystem in which they are introduced.

Examples of introduced species: dandelions in North America, camels in Australia, muskrat in Europe, monk parakeets in New York City

Chinese mantises have been introduced in North America to control garden pests. 
Invasive species: Invasive species are introduced species that have adverse effects on the ecosystem to which they have been introduced. Often, the designation of "invasive" is made by governing agencies, based on many factors, such as the species' ability to outcompete native species, disrupt natural food webs or population cycles, and affect the physical features of the geographical area.

Examples of invasive species: kudzu in North America, cane toads in Australia, black rats in New Zealand, domestic cats over much of the world

Free-roaming domestic cats can have devastating effects on native wildlife. 
Pests and noxious weeds: Pests and noxious weeds are animals and plants which adversely affect agriculture, horticulture, livestock, or humans.  Pests and noxious weeds are often introduced and invasive species, but native plants and animals can also be classified as pests or noxious weeds.  Sometimes, the classification of native animals or plants as pests drives them to endangerment or extinction.

Examples of pests and noxious weeds: poison ivy, gypsy moth, black rats, mosquitoes, common ragwort

Japanese beetles are common garden pests. 

INCORRECT: "The Siberian tiger is the largest breed of big cat."
CORRECT: Only domestic animals have breeds.  Siberian tigers are a subspecies of tiger, and tigers are a species of big cat. 

INCORRECT: "Poison ivy has become invasive in the backyards of many Marylanders"
CORRECT: Only exotic species can be designated as invasive.  Vigorous spreading is simply part of the natural history of some native plants.  Poison ivy, however, could be considered a pest or noxious weed, even though it is native, because it impacts human activity. 

INCORRECT: "We went to the circus and saw domesticated bears!"
CORRECT: Bears have not been altered significantly from their wild ancestors by human breeding and selection.  Even though some bears may be well-socialized to humans under captive care, they cannot be considered domesticated, but rather, could be called "tame" or habituated/socialized to humans. 

INCORRECT: "After being widely planted, English ivy has become native over much of Maryland."
CORRECT: Because English ivy was introduced to North America by humans, it is not a native plant. It has escaped human care and can live in a variety of conditions without human intervention, so it could be considered naturalized.  However, naturalized species can also be invasive if they negatively impact the natural ecosystem. 

INCORRECT: "I let my cat outdoors to roam because it is more natural."
CORRECT:  There is nothing natural about allowing domestic cats to roam around Maryland habitats and communities. Domestic cats are a domesticated from of the African wild cat, which is not native to Maryland.  Further, the activities of domestic cats negatively impact wildlife and natural communities, making them an invasive, introduced species. 

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