Asclepias welshii
Asclepias welshii
Asclepias welshii is a plant of the genus milkweed ( Asclepias ) from the subfamily of milkweed plants ( Asclepiadoideae ). The specific epithet honors Stanley Larson Welsh, former professor of botany and curator of the herbarium at Brigham Young University in Provo (Utah, USA). The species is a pioneer plant on shifting sand dunes.
- 5.1 Literature
- 5.2 Notes and references
Features
Vegetative characteristics
Asclepias welshii is a perennial, herbaceous, upright growing plant with a root system consisting of several taproots that are connected by horizontally extending side shoots. The upright or ascending, standing in clusters, vigorous shoots are 25 to 100 cm high (long ) and are unbranched. The stalked leaves are opposite, the stems 1-5 mm ( rarely up to 10 mm ) long. The leathery leaf blades are shaped differently along the drive. The upper leaves are broad oblong- elliptic, ovate or verkehrteiförmig with rounded or flattened, stachelspitzigen outer end, and a rounded to approximately heart-shaped bottom. They are (6) 7-9 (15) inches long, and (3 ) 3.5 to 6 (8) inches wide. The lower leaves are sessile, much smaller, elliptical sharpened outer end and basally cordate - amplexicaul. The leaves are initially densely covered with a white fluffy wool; they will later be bald, especially at the bottom.
It makes three different types of shoots with corresponding leaf forms, which are often formed from the same root system and can grow side by side. Palmer & Armstrong call these different types as
- Primary stage with narrow - linealischen leaves. Seedlings and shoots that arise from small rhizomes and which may be several years old, form of this type.
- " Secondary stage " intermediate forms between the primary stage and the mature stage
- " mature stage ": see above
Inflorescence and flowers
The few buds sit on the side of the uppermost nodes present. They are stalked, the woolly hairy stems are 2-4 cm, rarely up to 7 cm long. The spherical, zymosen inflorescences have a diameter of 7 cm and contain up to 30, densely packed flowers. The comparatively large, stalked flowers are hermaphrodite, radial symmetry and fünfzählig. The stems are 8 to 13 mm (rarely to 20 mm) long haired and woolly. The sepals are already bent back at the base, then they curve upwards and adhere to the curvature of the petals. They are linear, 5 to 7.5 mm long, green above, woolly hairs on the underside. The corolla is cup-shaped with recurved and ascending petals. The very dense arrangement of flowers in the inflorescence prevents the complete spreading of the petals, forcing them to rise. The corolla is ( 5) 6-7 ( 8) mm long, and cream-colored with pink tint. The tip are ovoid, 6-7 mm long and busy at the bottom with very fine hairs. The row staminale Nebenkrone is stalked very short. The pale green stem is 0.5 mm long and 1.5 to 2.5 mm thick. The cream-colored, sack -shaped, curled tip of the corona are 2.5 to 4 mm long, the ends are wide - flattened and about 2 mm wide. They are approximately 1 mm longer than the Gynostegium. The horn-shaped, flattened on the inside of the secondary extension sets each at about the middle of the inside of the tip and protrudes out of the bag-shaped lobes. He is incurved almost horizontal crescent- shaped and about the stylus head. The stylus head is 1.2 to 1.5 mm high and 1.5 to 3.4 mm in diameter.
Fruit and seeds
The follicles are splayed splayed or hanging on the stalk. They are broad - fusiform and 4-7 cm long. The smooth or woolly hairy surface carries soft, pfriemliche tubercle. The seeds are broadly elliptical and up to 20 mm long ( Roth ( 2001) ). The head of hair is rudimentary at best.
Geographical distribution and (syn ) Ecology
The species is only known from a small area on the border of the U.S. states of Arizona and Utah. It grows to between 1,700 and 1,900 m. The largest and richest individual- occurrence is located in the Coral Pink Sand Dunes State Park in southern Utah.
Asclepias welshii is a pioneer plant that inhabited active not vegetated sand dunes, together with Redfieldia flexuosa. The rhizome -like roots meter deep into the sand, possibly even into the bedrock. For this widely ramified root system several drives can be formed which can often corresponding to the root system far apart standing. It is therefore often difficult to determine how many (genetically ) different individuals actually colonize a dune, or if it is the same plant to the clones. Stabilize a dune and is populated by other plant species Asclepias may ultimately be displaced welshii. The reproduce vegetatively in the first place; but also by seeds. Thus, the seeds fall into a suitable habitat, the head of hair the seed is rudimentary at best. A shipment of seeds by wind thus takes place hardly. The seeds fall from the pop of the seed capsule in the immediate vicinity of the parent plant.
In the dunes Asclepias welshii is associated with Wyethia scabra, Artemisia campestris, Chrysothamnus nauseosus, Eriogonum alatum, Eriogonum leptocladon, Psoralidium lanceolatum, Calamovilfa gigantea and Muhlenbergia pungens. In another area also occur: Juniperus osteosperma, Pinus ponderosa and Quercus gambelii. The flowering period is from June to July, the seeds are produced from July to early September.
As pollinators of flowers the following insect species have been recorded:
- Ceratina nanula
- Xylocopa californica
- Western Honey Bee (Apis mellifera)
- Bombus bifarius
- Dialictus albohirtus
- Dialictus ruidosensis
- Anthidium rodecki
- Heriades timberlakei
- Polistes dorsalis
- Mimesa sp.
- Microbembex californica
- Bembex americana
- Oxybelus californicus
- Euphydryas Anicia
- Euxoa aurulenta
Taxonomy and systematics
The taxon was described in 1979 by Noel Herman Holmgren and Patricia Holmgren core for an occurrence in Kane County in the U.S. state of Utah for the first time. Since then, further resources are added in three counties in the state of Arizona. Synonyms are not known.
Endangering
The area is threatened by off-road vehicles. The species is classified as Critically Imperiled or " Endangerd ".