When a colony of plants or animals breeds in isolation, they may develop characteristics different from the parent stock. Over time, these differences can become so great that the isolated colony cannot breed with the parent stock. A new species has evolved.

When a colony of plants or animals breeds in isolation, they may develop characteristics different from the parent stock. Over time, these differences can become so great that the isolated colony cannot breed with the parent stock. A new species has evolved.

© Nova Scotia Museum of Natural History 2001. All Rights Reserved

Orcid

Isolated from mainland populations by 160 km of water, these species have developed unique characteristics. The leaves of Sable's variety of the grass-pink orchid are more oblong than leaves of its parent stock on the mainland.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. All Rights Reserved


Rush

This variety of rush is found only on Sable Island.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. All Rights Reserved


Sable Island moth, egg mass (wingless female), mainland moth

Sable Island moth, egg mass (wingless female), mainland moth Females of this moth have no wings, which helps isolate the Tussock moth from mainland populations. Over time, Sable's moths have become darker, more orange and less distinctly marked than the parent stock.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. All Rights Reserved


An animal’s reproductive behaviour can isolate it just as effectively as physical barriers. Animal populations that develop different courtship patterns, breeding times or breeding places may also become cut off from others of their kind.
An animal’s reproductive behaviour can isolate it just as effectively as physical barriers. Animal populations that develop different courtship patterns, breeding times or breeding places may also become cut off from others of their kind.

© Nova Scotia Museum of Natural History 2001. All Rights Reserved

Ipswich Sparrow, Savannah Sparrow

Water is no barrier to the Ipswich sparrow, which spends summers on Sable and winters in New England. But Ipswich Sparrows breed only on Sable Island, and have become different from their parent stock, the Savannah sparrow. What differences can you see? Compare the size, tail length, overall colour, and the yellow patch in front of the eye.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. All Rights Reserved


Harbour Seal

Many small populations of harbour seals live along the North Atlantic coast. Sable's Harbour Seals have a strong tendency to return to the island to breed, instead of mixing with other harbour seals.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. Tous droits réservés


Harbour Seal Skull and teeth

Some features that are not common among Harbour Seals are becoming unusually frequent in Sable's population. For example, count the molar teeth on the seal skulls; most Harbour seals have 5.

Nova Scotia Museum of Natural History
Sable Island Preservation Trust

© Nova Scotia Museum of Natural History 2001. All Rights Reserved


Learning Objectives

The learner will:

  • Describe some adaptations of plants and animals that enable them to thrive on Sable Island.

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