Habitats of North Carolina
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Members of Rock Outcrops, Glades, and Barrens:
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Rock Outcrops, Glades, and Barrens
General Dry-Xeric Glades and Barrens
General Description This habitat consists of open areas associated with either sandy soils or thin soils weathered from rock layers located close to the surface. Soil chemistry is not a critical factor, with examples found on both circumneutral to acidic substrates. The well-drained soils of sandhills are typically dry throughout the year. Soils weathered from subsurface rocks can be wet during the winter, holding water in small depressions, particularly when clays are present, but can conversely dry out completely during the summer.

Determining Species of plants include xerophytic herbs, graminoids, or shrubs. All are both drought and fire-resistant. Determining animal species are primarily herbivores that are specialized on the plant species characteristic of these habitats. The one lizard included in this habitat is predator that needs open areas to spot its prey and/or its enemies, allowing it to use its great running speed for both pursuit and escape. All of these species are found widely across the state, occurring in two or more of the state's physiographic provinces.

Abiotic Factors Geographic Regions: Lower Coastal Plain to the Low Mountains. USDA Hardiness Zones: 6-8. Landform: ridges, slopes, and flats. Slope Aspect: occurs primarily on south- and west-facing slopes aspects as well as on ridges and dry flats. Soil Moisture: Dry to xeric. Soil texture: rocky, loamy, or sandy. Soil pH: acidic to circumneutral. Soil Nutrient Content: poor to rich.Microclimate: Warm to hot; dry to xeric. Hydrological Features: water is only temporarily available in small depressions. Fire Frequency: frequent in the sandhills, occasional in the Piedmont and Mountains. Drought Frequency: regular to occasional. Insolation: open and well-insolated

Biotic Structure Vegetation Type: open barrens and sunny glades in woodlands. Strata: forest canopy is open or absent; shrub and herb layers are present but often sparse; bare ground is frequently extensive. Organic Shelter, Foraging, and Nesting Structures: woody debris and thick litter layers are typically lacking in these habitats; thick herbaceous growth provides some shelter but extensive areas of bare ground may also be present; some of the animal species actually nest, forage, or bask preferentially in these open to semi-open areas


Co-evolved Species Groups Phagic and Competitory Symbioses:
Tephrosia virginiana // Digrammia eremiata
Yucca species // Megathymus cofaqui-Megathymus yuccae-Prodoxus decipiens


Obligate Phagic/Pollinator Mutualism:
Yucca filammentosa // Tegeticula yuccasella The relationship between Yucca species -- particularly Y. filamentosa in North Carolina -- and the Yucca Moth (Tegeticula yuccasella) involves a particularly strong degree of mutualism, with the moths completely dependent on their host plants for food and the plants pollinated almost entirely by the moths (described by Engleman, 1872, with details given by Riley, 1892; see Marr et al., 2000. Pellmyr and Krenn, 2002, and Troeger et al., 2021 for recent studies).

Determining Species
sciNamecomNameg_ranks_rankmod_s_rankprob_of_extirpation
BIRDS
Chordeiles minorCommon NighthawkG5S3S30.00407
BUTTERFLIES
Erynnis zaruccoZarucco Duskywing
Polites vibexWhirlabout
Thorybes lyciadesHoary Edge
Megathymus cofaquiCofaqui Giant-skipperG3G4S1S10.33330
Megathymus yuccaeYucca Giant-skipperG5S3S4S3S40.00132
FORBS
Yucca flaccidaWeakleaf YuccaG5S1S10.33330
Duravia species 2Pleatleaf Knotweed G5S2S20.03699
Agave virginicaEastern False-aloeG5S3S30.00407
Croton willdenowiiElliptical RushfoilG5S3S30.00407
Houstonia longifoliaLongleaf BluetG5S3S30.00407
Liatris squarrosaScaly Blazing-starG5S4S40.00041
Phlox nivalisTrailing PhloxG4G5S4S40.00041
Viola pedataBird's-foot VioletG5S4S40.00041
Yucca filamentosaCommon YuccaG5S4S5S4S50.00010
Asclepias verticillataWhorled MilkweedG5S5S50.00000
Commelina erectaa Dayflower var. unknownG5S5S50.00000
Cunila origanoidesCommon Dittany, Wild OreganoG5S5S50.00000
Ionactis linariifoliaStiff-leaved AsterG5S5S50.00000
Solidago odoraSweet GoldenrodG5S5S50.00000
Stylosanthes bifloraPencilflowerG5S5S50.00000
Tephrosia virginianaGoat's-rueG5S5S50.00000
GRAMINOIDS
Sporobolus vaginiflorusSheathed DropseedG5S3S30.00407
Gymnopogon ambiguusBroadleaf BeardgrassG5S5S50.00000
LIZARDS
Aspidoscelis sexlineataEastern Six-lined RacerunnerG5S5S50.00000
MOTHS
Chytonix sensilisPine Barrens Fungus Moth
Bleptina sangamoniaGUS1S2S1S20.11107
Lobocleta peralbataan inchworm mothGNRS2S3S2S30.01230
Tegeticula yuccasellaYucca MothG4S2S3S2S30.01230
Chaetaglaea rhondaTrembling Sallow, Barrens ChaetaglaeaS2S40.00407
Digrammia eremiataThree-lined Angle MothG4S3S4S3S40.00132
Hemeroplanis scopulepesVariable TropicG5S3S4S3S40.00132
Prodoxus decipiensBogus Yucca MothG4S3S4S3S40.00132
Ptichodis bistrigataSouthern PtichodisG3S3S4S3S40.00132
Xystopeplus rufagoRed-winged SallowS3S40.00132
Bleptina inferiorInferior Owlet MothGNRS4S5S4S50.00010
Ponometia semiflavaHalf-yellowG4S4S5S4S50.00010
ORTHOPTERANS
Campylacantha olivaceaFuzzy Olive-green GrasshopperG5S1S2S1S20.11107
Conocephalus saltansPrairie Meadow KatydidG5S2S3S2S30.01230
SHRUBS
Comptonia peregrinaSweet FernG5S3S30.00407
Hypericum virgatumSharpleaf St. John's-wort +G4S4S40.00041
Nr = Number of Ranked Species = 37
Ner = Number of Extant, Ranked Species = 37
Nv = Number of Historic and Extirpated Species = 0
Nar = Number of Species at Risk of Extirpation (State rank > S5) = 28
Nss = Number of Secure Species (State Rank = S5) = 9
Pss = Proportion of Secure Species (Nss/Ner) = 0.24324
ENE = Expected Number of Extirpations (Sum of PE) = 1.00098
Average PE (ENE/Ner) = 0.02705
Habitat Risk Index = (Nar+Nv) x Average PE = 28 x 0.02705 = 0.7574

Estimated Risk to the Determining Species The Average Probability of Extirpation is equivalent to a state rank of S3 under our model. This indicates that this habitat has at least the minimum level of conservation concern. Apart from the Six-lined Racerunner, the animal members of this habitat have generally higher Probabilities of Extirpation than the plants. This discrepancy is particularly acute in the rank of S4S5 (recommended as S5 by LeGrand, Sorrie, and Howard, acc. 2022) for Yucca filamentosa and the rank of S1S3 given to Tegeticula yuccasella. If these species are truly obligate mutualists, their probabilities of extirpation should be identical. The most likely explanation is that the moth has been severely undersampled compared to the plant; the adult moths, in fact, are usually found only in the vicinity of the plants and found by direct inspection of the flowers. The alternative hypothesis is that the rarity of the moths is an accurate predictor of successfully reproducing populations, which are far fewer in number than those that are persisting in a fragmented landscape primarily by vegetative reproduction. Surveys need to be conducted to document the distribution and frequency of successful pollination of yuccas across the state.

Estimated Risk to the Co-evolved Species Groups Although only eight of the 35 species of this habitat are involved in co-evolved associations, the Average Probability of Extirpation of this group is quite high, 0.096, which is equivalent to a state rank of S2.

Estimated Security of the Habitat The presence of nine Secure Species and the Proportion of Secure Species of 24% indicates that in the past at least, this habitat was widely distributed and occurred either as large blocks or well-connected clusters of smaller blocks. This evaluation contrasts with the picture presented by the Species at Risk, which indicate a moderately high level of conservation concern. As discussed above with respect to Yuccas and Yucca Moths, this difference may reflect a current distribution that is highly fragmented, as indicated by the animal members of this habitat, and a previously more secure situation reflected by the relict distribution of long-persistent plant species.

Index of Habitat Imperilment The moderately large number of species at risk coupled with a moderately high Average PE, produces a moderately high value of ENE. That value, however, is substantially offset in the calculation of HRI by the moderately high value of PSS. The value of HRI falls within our Tier 2 (5 ≥ HRI > 0.5) Level of Conservation Concern, having a high priority for conservation efforts.

Identified Risks Habitat conversion to agriculture, silviculture, and development are major risk factors for all dry upland habitats. Fire suppression is a major threat to areas that otherwise remain in a natural state.
Observed Trends
Distribution Map
Distribution This habitat is widely but sparsely distributed across the state. The naturally patchy distribution coupled with massive habitat fragmentation associated with human activities is probably responsible for the generally low number of counties that show a concentration of the Determining Species. Under high levels of fragmentation, loss of species from any one site is unlikely to be recovered by dispersal from sites that are becoming increasingly widely separated.

Major Conservation Reserves
Priority Areas for Surveys and Conservation Protection
Stewardship and Management Recommendations
References Marr, D.L., Leebens‐Mack, J., Elms, L. and Pellmyr, O., 2000. Pollen dispersal in Yucca filamentosa (Agavaceae): the paradox of self‐pollination behavior by Tegeticula yuccasella (Prodoxidae). American Journal of Botany, 87(5), pp.670-677. Available online at: https://bsapubs.onlinelibrary.wiley.com/doi/pdf/10.2307/2656853

Pellmyr, O. and Krenn, H.W., 2002. Origin of a complex key innovation in an obligate insect–plant mutualism. Proceedings of the National Academy of Sciences, 99(8), pp.5498-5502. Available online at: https://www.pnas.org/content/pnas/99/8/5498.full.pdf

Riley, C.V., 1892. The yucca moth and yucca pollination. Missouri Botanical Garden.

Tröger, A., Svensson, G.P., Galbrecht, H.M., Twele, R., Patt, J.M., Bartram, S., Zarbin, P.H., Segraves, K.A., Althoff, D.M., von Reuss, S. and Raguso, R.A., 2021. Tetranorsesquiterpenoids as attractants of yucca moths to yucca flowers. Journal of chemical ecology, 47(12), pp.1025-1041.


Updated on 2022-06-27 23:20:14