Habitats of North Carolina
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General Shrublands
General Holly Thickets
No image for this habitat.
General Description The presence of Hollies (Ilex species) is the defining factor for this habitat. Except for American Holly, which can reach tree size, this habitat mostly consists of shrub thickets. The type of vegetation included range from wet-hydric peatlands to dry-xeric maritime thickets to mesic forests with an understory of Ilex americana.

Both American Holly and Possumhaw Holly are widely distributed and found in both upland and lowland situation; consequently they are considered Determining Species of this habitat. Also included is Carolina Holly, although it is more of a dry-mesic upland species than the other two. Other species are more regionally restricted or more specialized in terms of the habitat conditions they require and are consequently included in other habitats.

Also included here as Determining Species are the herbivores that are either stenophagous on Ilex species in general or feed on either American or Possumhaw Hollies.

Abiotic Factors Geographic Regions: Lower Coastal Plain to High Mountains. USDA Hardiness Zones: 6-8. Landform: ridges, slopes, bottomlands, and wet flats. Slope Aspect: occurs on all slopes aspects as well as on ridges and flats. Soil Moisture: Dry to wet. Soil texture: sandy to loamy to peaty. Soil pH: primarily acidic; many species are associated with peatlands or blackwater wetlands. Soil Nutrient Content: typically poor; only one a few species, e.g., Ilex longipes and Ilex myrtifolia prefer mineral rich, circumnetural soils. Salt tolerance tidewater examples are all exposed to salt spray. Microclimate: Warm to cool; humid to dry. Hydrological Features: surface waters are common to scarce. Flood Frequency: transiently to never flooded. Flood Duration: nonexistent to transient. Fire Frequency: common to rare. Drought Frequency: frequent to rare. Insolation: full sun to full shade.

Biotic Structure Key Species the presence of Ilex species is a requirement Vegetation Type: shrublands to closed-canopy forests; all stages of natural succession are included. Organic Shelter, Foraging, and Nesting Structures: Holly thickets provide important shelter for wintering species of birds, as well as breeding species; woody debris and leaf litter are plentiful in forested examples but sparse in shrubland examples.

Co-evolved Species Groups Phagic and Competitory Symbioses:
Ilex species // Episemasia solitaria-Ilexia intractata-Metaxaglaea violacea-Rhopobota dietziana-Rhopobota finitimana
Ilex decidua-Ilex verticillata // Phytomyza ditmani
Ilex opaca // Phytomyza ilicicola
Ilex opaca-Ilex cassine // Phytomyza opacae


Determining Species
sciNamecomNameg_ranks_rankmod_s_rankprob_of_extirpation
BUTTERFLIES
Callophrys henriciHenry's ElfinG5S4S40.00041
HARDWOODS
Ilex opacaAmerican HollyG5S5S50.00000
HEMIPTERAN HOPPERS
Erythroneura integraS3S40.00132
LEAF-MINING FLIES
Phytomyza ditmaniSNR
Phytomyza ilicicolaNative Holly LeafminerSNR
Phytomyza opacaeSNR
MOTHS
Rhopobota finitimanaGNRSUS3S40.00132
Rhopobota dietzianaa tortricid mothGNRS3S5S3S50.00041
Episemasia solitariaSolitary Episemasia MothGNRS4S5S4S50.00010
Ilexia intractataHolly Looper, Black-dotted RuddyGNRS5S50.00000
Metaxaglaea violaceaViolaceous Sallow MothG5S5S50.00000
SHRUBS
Ilex ambiguaCarolina HollyG5S3S30.00407
Ilex deciduaPossumhaw , Deciduous HollyG5S5S50.00000
Nr = Number of Ranked Species = 10
Ner = Number of Extant, Ranked Species = 10
Nv = Number of Historic and Extirpated Species = 0
Nar = Number of Species at Risk of Extirpation (State rank > S5) = 6
Nss = Number of Secure Species (State Rank = S5) = 4
Pss = Proportion of Secure Species (Nss/Ner) = 0.40000
ENE = Expected Number of Extirpations (Sum of PE) = 0.00763
Average PE (ENE/Ner) = 0.00076
Habitat Risk Index = (Nar+Nv) x Average PE = 6 x 0.00076 = 0.00456

Estimated Risk to the Determining Species A single species ranked as S3 has the highest conservation value in this habitat. The Average PE is equivalent to a State Rank of S4.

Estimated Risk to the Co-evolved Species Groups
Estimated Security of the Habitat The presence of four species that are considered secure in North Carolina and the PSS value of 44% indicates a moderately high degree of security for this habitat. Holly-containing habitats are still common across the state and are quite extensive is some areas.

Index of Habitat Imperilment The combination of a low value of ENE, a moderately high value of PSS, and no identified Historic or Extirpated Species, makes the value of HRI quite low, falling within our Tier 5 Level of Conservation Concern (0.005 ≥ HRI > 0) and having a negligible priority for conservation actions.

Identified Risks
Observed Trends
Distribution Map
Distribution
Major Conservation Reserves
Priority Areas for Surveys and Conservation Protection
Stewardship and Management Recommendations
References Londale and Sheffer. 2011. Revision of Nearctic Holly Leafminers in the Genus Phytomyza (Diptera: Agromyzidae), Including Descriptions of Four New Species. Ann. Entomol. Soc. Am. 104(6): 1183-1206. Available online at: https://www.researchgate.net/profile/Sonja-Scheffer/publication /272209535_Revision_of_Nearctic_Holly_Leafminers_in_the_Genus_Phytomyza_Diptera_Agromyzidae_Including_Descriptions_of_Four_New_Species/links/5847261008aeda6968227b5c/Revision-of-Nearctic-Holly-Leafminers-in-the-Genus-Phytomyza-Diptera-Agromyzidae-Including-Descriptions-of-Four-New-Species.pdf


Updated on 2022-07-21 00:29:41