relict

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Ecology A species that inhabits a much smaller geographic area than it did in the past, often because of environmental change.
• noun Something that has survived; a remnant.
• noun Law A widow or widower.
• adjective Of or relating to something that has survived, as structures or minerals after destructive processes.

from The Century Dictionary.

• noun One who is left or who remains: a survivor.
• noun Specifically, a widower or widow, especially a widow.
• noun A thing left behind; a relic.
• Left; remaining; surviving.
• In phytogeography, persisting in a limited area only: said of an endemic plant which at an earlier period had a much wider range.
• In physical geography, left as a result of erosion; residual: said of mountains the form of which is due to the erosion of neigh boring valleys, as mountains of circumdenudation, and especially isolated residual mountains or monadnocks.
• To leave.

from the GNU version of the Collaborative International Dictionary of English.

• noun A woman whose husband is dead; a widow.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun formal Something which, or someone who, survives or remains or is left over after the loss of others; a relic.
• adjective Surviving, remaining.
• adjective That is a relict; pertaining to a relict.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an organism or species surviving as a remnant of an otherwise extinct flora or fauna in an environment much changed from that in which it originated
• noun geological feature that is a remnant of a pre-existing formation after other parts have disappeared