Natural Heritage Program List of Rare Plant Species - Rawlings ...

Watch Category 6 ( regionally rare) includes species which are rare in one region of North Carolina, while
being uncommon to abundant within another region. These regional rarities, generally within-state disjuncts,
are significant for protection of genetic variation and long-term viability of species.
A list of North Carolina's rare plants is, of course, determined by the arbitrary, political boundaries of the
state. Biological rarity, however, is determined by the natural boundaries of physiography, geology, soils,
and climate. These and other physical, biological, and historic factors have determined the evolutionary
history and phytogeography of plants currently occupying what is now called "North Carolina." Rarity in
one part of the state — especially when disjunct from the region of greater abundance — can have as much
biological significance as disjunctions from another state. Disjunct populations nearly always have some
level of genetic differentiation from populations in the main part of a species' range. If this genetic
differentiation is great enough — and obvious enough — the disjunct population may be recognized as a
separate species, subspecies, or variety. In many cases, however, the genetic differentiation is not great
enough (or is not obvious enough with the relatively crude taxonomic tools which have been applied to most
taxa) to have warranted the naming of a distinct taxon. Further study will likely show that many disjunct
populations do warrant taxonomic status. Preservation of biodiversity requires not only preventing the
extinction of species, but also maintaining genetic diversity within the species. The long-term viability of
a species is dependent on the genetic diversity represented within and between different populations of the
species. Disjunct and peripheral populations are especially likely to contain genetic material rare or absent
in the bulk of the species' populations. Moreover, within-state disjunctions are likely to serve as indicators
of regionally unique or unusual habitats. Attention to such species is especially important in county natural
area inventories and regional planning.
The following list of Watch Category 6 plants is not exhaustive, but represents some of the most important
and significant within-state disjunctions. An emphasis has been placed on species which are disjunct rather
than peripheral — that is, which have a demonstrable gap in their North Carolina ranges. Examples are
Rhododendron catawbiense, which is rather common at high to medium elevations in the mountains, but
occurs in small, disjunct populations in the lower Piedmont and upper Coastal Plain, and Pogonia
ophioglossoides, a primarily Coastal Plain species, occurring in rare bogs in the mountains.
SANDHILLS COASTAL PLAIN
Comptonia peregrina Anemone quinquefolia
Drosera rotundifolia Aster cordifolius
Leiophyllum buxifolium Castilleja coccinea
Pinguicula caerulea Clematis ochroleuca
Pleea tenuifolia Clematis virginiana
Rhododendron catawbiense Delphinium tricorne
Rhododendron minus Leiophyllum buxifolium
Magnolia tripetala
Pellaea atropurpurea
Platanthera lacera [= Habenaria lacera]
Stenanthium gramineum
Viola blanda
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