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5 Cards in this Set

  • Front
  • Back
Endemism
- condition of being restricted in
distribution to a particular region. When a species is referred to as being “endemic,”
a geographic region must be specified (e.g., Lewisia tweedyi is endemic to
Washington, or Campanula piperi is endemic to the Olympic mountains).
Descrie four types of ranges of species
Narrow endemic - very restricted distribution
Scarce - widely distributed, but never very abundant
Common - Regional distribution; abundant somewhere
Cosmopolitan - found everywhere (e.g., Bracken fern); this is unusual - <10% of spp.
Two types of narrow endemics
Paleoendemics - ancient origin, left over from wider distribution, and typically have no
closely related species
Examples: Sequoia sempervirens (Coast Redwood) in California
Kalmiopsis leachiana in Siskiyous (Oregon) – named for Lila Leach
Microcycas in Cuba – every plant is known and counted
Metasequoia glyptostroboides – first described as a fossil, but then discovered
in 1940’s in Hupei province in China
59
Neoendemics - recent in origin (typically post-Tertiary in origin) and typically have
closely related species nearby
eg, allopolyploids (species derived from hybridization and chromosome doubling,
so the parent species are still around) and peripherally isolated species from more
widespread species
Examples: Erigeron piperianus endemic to eastern Washington is a recently derived
offshoot of the widespread Erigeron linearis, found throughout the
intermountain region.
Stephanomeria malheurensis known from one very small locality in eastern
Oregon, where it is distinguishable from its progenitor species by
smaller flowers and self-fertilizing mating system.
Describe kinds of rarity in terms of geographic range and habitat specificity
see chart
Discuss three environmental determinants of rarity
1) Habitat Specificity - geo-edaphic factors; discontinuous distribution of sites favorable
to particular plant; isolation can lead to speciation. Serpentine endemics in California
and Oregon (and elsewhere around the world) are good examples of this.
2) Local Climate/Regional Climate - some paleoendemics may occupy “relictual
climates” (eg, similar to climates in the Tertiary, before the Ice ages). An example is
the Dawn Redwood (Metasequoia glyptostroboides), found only in a small valley in
China, but once very widespread. The “Arcto-Tertiary flora” is based on this
concept. Related plants in eastern North America, Europe, and Eastern Asia
represent the remnants of a once widespread flora that covered all of the northern
latitudes when the climate was milder.
3) Biotic factors - the interaction between species, including plant dependence on
pollinators that may be rare or extinct. Example is Kincaid’s lupine in the Willamette
Valley in Oregon, which is pollinated by a rare butterfly. This is believed to be
responsible for some of the rare plants in Hawaii, which no longer have native
pollinating birds.