Croton alabamensis
| Alabama croton | |
|---|---|
| |
Scientific classification 
| |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Malpighiales |
| Family: | Euphorbiaceae |
| Genus: | Croton |
| Species: | C. alabamensis
|
| Binomial name | |
| Croton alabamensis | |
| Varieties | |
|
C. a. var. alabamensis | |
Croton alabamensis, known as Alabama croton, is a rare species of flowering plant in the spurge family, Euphorbiaceae, that is endemic to Texas and Alabama in the Southeastern United States.[2]
Description[edit]
The Alabama croton is a semi-evergreen monoecious shrub that reaches a height of 5–35 dm[3] The loose, multi-stemmed thickets[4] it forms are colloquially known as "privet brakes".[5] C. alabamensis is the northernmost shrubby species of the genus Croton in North America[6] and the largest species of Euphorbiaceae native to North America.[7]
Leaves[edit]
Leaves are clustered at branch tips and lack stipules. The petiole is 0.6–2 cm. Glands are absent at its apex. Leaf blades are elliptic, ovate, or oblong and measure 3–10 × 1.5–5 cm. Blade margins are typically entire, sometimes undulate. The base is rounded to obtuse, while the apex is acute, rounded, or emarginate. Abaxial surfaces are silvery or coppery and densely lepidote, while adaxial surfaces are green and sparsely lepidote.[3]
Flowers[edit]
The inflorescence is a bisexual or unisexual raceme 2–4.5 cm in length. Racemes have 0–15 staminate flowers and 0–10 pistillate flowers.[3] Flowers are pollinated by bees.[5]
Staminate (male) flowers[edit]
The pedicels of staminate flowers are 2.2–4 mm long. The 5 sepals are 1.1–2.9 mm in length and have a lepidote abaxial surface. The 5 petals are oblong-ovate and 2–3.1 mm in length with an abaxial surface that is glabrous except at margins, where it is stellate-ciliate. Staminate flowers have 10–22 stamens.[3]
Pistillate (female) flowers[edit]
Pedicels of pistillate flowers are 2.2–7.5 mm in length, increasing to 7–11 mm when in fruit. The 5 sepals measure 2–4.5 mm in length, have entire margins, an incurved apex, and a lepidote abaxial surface. The 5 petals are pale green, ovate, and 2–3.5 mm in length. The ovary is 3-locular. There are 3 styles 2–5 mm long, usually unbranched, rarely 2-fid, with 3 terminal segments (sometimes 6).[3]
Fruit[edit]
The fruit is a smooth capsule measuring 1.6–2.5 × 2–3 mm. The columella is 3-angled. Seeds are shiny and measure 6.7–8 × 5.2–6 mm.[3]
Cultivation[edit]
The Alabama croton is grown as an ornamental for its form and foliage.[8] Although normally forming loose clonal colonies, it can be trained as a single-trunked, dense shrub.[9]
Varieties[edit]
There are two varieties that are separated by more than 1000 km:[10]
- Croton alabamensis var. alabamensis, or Alabama croton, is the nominate subspecies and is only found in two central Alabama counties (Warrior River, Tuscaloosa County and Cahaba River, Bibb County). A herbarium specimen was supposedly collected in Coffee County in Tennessee, but the veracity of this collection location is dubious.[7] It is considered Vulnerable by NatureServe.[11]
- Croton alabamensis var. texensis, or Texabama croton, is found in three counties (Bell, Coryell and Travis Counties) in Texas. It is considered Imperiled by NatureServe.[4][12]
Habitat and Range[edit]
Alabama[edit]
The nominate variety is found on dry slopes, bluffs, and outcroppings with thin, alkaline soil in Tuscaloosa and Bibb County, Alabama.[5][13] In Bibb County, it is found in Ketona dolomite glades near the Calaba River, where associated woody vegetation includes Juniperus virginiana, Quercus muehlenbergii, Pinus palustris, Sabal minor, and Phyllanthopsis phyllanthoides.[14]
Texas[edit]
Texabama croton is restricted to the eastern Edwards Plateau[10] and southern Cross Timbers[15] within Travis, Bell and Coryell counties. Within this limited range, it has a very patchy distribution and is abundant in the few niches where it occurs and is absent elsewhere. C. alabamensis var. texensis inhabits pockets of deep soils within forested, mesic canyons and upland oak mottes[16] at elevations of 200 to 400 m.[17]
Phylogeny and Evolutionary History[edit]
Croton alabamensis belongs to the monotypic section Alabamenses within the subgenus Quadrilobi.[18] Its closest relatives inhabit primarily mesic regions in the Neotropics, such as members of the former genus Moacroton, which are restricted to serpentine soils in Cuba.[19] Molecular clock analysis suggests it split from its closest relative in the middle Eocene, approximately 41 million years ago. The Alabama and Texas varieties diverged much more recently in the Quaternary, possibly due to allopatric speciation.[6]
History[edit]
Croton alabamensis was discovered in July 1877 by geologist Eugene Allen Smith on limestone bluffs at Pratt's Ferry near Centreville, Alabama. Specimens of the plant were sent to botanist and pharmacist Charles T. Mohr, who then passed them to botanist Alvan Wentworth Chapman. Chapman formally described C. alabamensis as a new species in the second edition of his Flora of the Southern United States.[13] C. alabamensis var. texensis was discovered in April 1989 at Fort Cavazos in Coryell County by Carol Beardmore and Rex Wahl.[20] Two months later, plants were independently discovered by Chuck Sexton approximately 70 km to the south on the Post Oak Ridge[21] of the future Balcones Canyonlands National Wildlife Refuge in northwestern Travis County.[20][22] Steve Ginzbarg, a botanist at the University of Texas at Austin, formally described it as a distinct variety of C. alabamensis in 1992.[21]
References[edit]
- ^ "Croton alabamensis. NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 6 May 2023.
- ^ "Alabama croton". USDA Plants.
- ^ a b c d e f van Ee, Benjamin W.; Berry, Paul E. (2016). "Croton alabamensis". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 12. New York and Oxford: Oxford University Press. Retrieved 27 May 2024 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- ^ a b "Croton alabamensis". Missouri Botanical Garden.
- ^ a b c Davenport, Lawrence J. (14 September 2023). "Alabama Croton". Encyclopedia of Alabama. Retrieved 27 May 2024.
- ^ a b Van Ee, Benjamin W.; Jelinski, Nicolas; Berry, Paul E.; Hipp, Andrew L. (2006). "Phylogeny and biogeography of Croton alabamensis (Euphorbiaceae), a rare shrub from Texas and Alabama, using DNA sequence and AFLP data" (PDF). Molecular Ecology. 15 (10): 2735–2751. Bibcode:2006MolEc..15.2735V. CiteSeerX 10.1.1.502.7848. doi:10.1111/j.1365-294X.2006.02970.x. hdl:2027.42/72311. PMID 16911197. S2CID 1157970.
- ^ a b Wurdack, K.J. (2006). "The lectotypification and 19th century history of Croton alabamensis (Euphorbiaceae S.S.)". Sida. 22 (1): 469–483.
- ^ "Texabama Croton, Alabama Croton". Aggie Horticulture.
- ^ Cullina, William (2020). Native Trees, Shrubs, and Vines: A Guide to Using, Growing, and Propagating North American Woody Plants. Echo Point Books and Media. ISBN 9781648370014.
- ^ a b Halward, Tracy; Lowrey, Timothy; Schulz, Keith; Schulz, Keith; Shaw, Robert (1996). "Germination Requirements and Genetic Diversity in Croton alabamensis var. texensis". Southwestern Rare and Endangered Plants Proceedings of the Second Conference September 11–14, 1995, Flagstaff, Arizona. USDA Forest Service.
- ^ "Croton alabamensis var. alabamensis. NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 6 May 2023.
- ^ "Croton alabamensis var. texensis. NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 6 May 2023.
- ^ a b Davenport, Larry (1994). "The Alabama Croton". Alabama Heritage (33).
- ^ "Alabama Ketona Glade and Woodland". NatureServe Explorer. NatureServe. Retrieved 27 May 2024.
- ^ Hayden, Timothy J.; Cornelius, John D.; Weinberg, Howard J.; Jette, Leslie L.; Melton, Robert H. (2001). "Endangered Species Management Plan for Fort Hood, Texas; FY01-05" (PDF). United States Army Corps of Engineers.
- ^ Poole, Jackie M.; Carr, William R.; Price, Dana M. (2007). Rare Plants of Texas: A Field Guide. Texas A&M University Press. p. 163. ISBN 9781585445578.
- ^ van Ee, Benjamin W.; Berry, Paul E. (2016). "Croton alabamensis var. texensis". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 12. New York and Oxford: Oxford University Press. Retrieved 27 May 2024 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- ^ Van Ee, Benjamin W.; Riina, Ricarda; Berry, Paul E. (2011). "A revised infrageneric classification and molecular phylogeny of New World Croton (Euphorbiaceae)" (PDF). Taxon. 60 (3): 791–823. doi:10.1002/tax.603013. hdl:2027.42/146834. PMID 16911197.
- ^ Van Ee, Benjamin W.; Berry, Paul E.; Riina, Ricarda; Gutiérrez Amaro, Jorge E. (2008). "Molecular Phylogenetics and Biogeography of the Caribbean-Centered Croton Subgenus Moacroton (Euphorbiaceae s.s.)". Botanical Review. 74 (1): 132–165. Bibcode:2008BotRv..74..132V. doi:10.1007/s12229-008-9003-y. hdl:10261/168375.
- ^ a b Powell, Christine; Rye, Dale (2011). "We're Texabama Bound" (PDF). CAMN Field Notes. Capitol Area Master Naturalists: 9–11.
- ^ a b Ginzbarg, Steve (1992). "A New Disjunct Variety of Croton alabamensis (Euphorbiaceae) from Texas". Sida. 15 (1): 41–52. JSTOR 41967533.
- ^ "Balcones Canyonlands National Wildlife Refuge" (PDF). United States Fish and Wildlife Service. 2003. Retrieved 2023-09-16.
External links[edit]
