“Asclepias meadii”的意思、由来-开放百科全书

The plant is a federally listed threatened species due to this destruction of its habitat.^[1] Factors contributing to its rarity include mowing and plowing, erosion, loss of a natural prairie fire regime, pesticides directly applied or drifting from nearby agricultural operations, invasive plant species, trampling by hikers, loss of native insect pollinators, and predation by a number of insect species.^[1]

Distribution

The only naturally occurring populations of the plant are located in Missouri and Illinois, and populations have been reintroduced to Indiana and Wisconsin, where the plant had been extirpated.^[2] There are also some populations in Kansas and Iowa, but few of these may last, especially in Kansas, where they occur on private hay fields that are mowed frequently.^[2]

Description

This is a rhizomatous perennial herb with a waxy erect stem growing up to about 40 centimeters tall. Blue-green, herringbone-patterned leaves occur in opposite pairs about the stem. The lance-shaped blades are smooth and sometimes wavy along the edges, and measure up to 8 centimeters long. The inflorescence is a nodding umbel of 6 to 23 fragrant flowers. Each flower has five petals up to a centimeter long which are green or purple-tinged when new and grow paler as they age. Behind them are five reflexed sepals. The flowers are nectar-rich^[2] and are pollinated by digger bees (Anthophora spp.), bumblebees (Bombus spp.),^[3] and other bees. The fruit is a follicle up to 8 centimeters long containing hairy seeds. The species is long-lived, taking at least four years to reach sexual maturity and living for several decades,^[3] possibly over a century.^[1]

Reproduction

The species often reproduces vegetatively by sprouting more stems from its rhizome. It also sometimes reproduces sexually by producing seed. A reduction in genetic diversity is a threat to the species, because human activity and other processes have favored vegetative reproduction, a cloning of the plants that does not remix genes.^[2]^[4] Mowing chops off the flowers or immature fruits, preventing seed production.^[2] Fragmentation of the habitat reduces the number of nearby plants that can trade pollen and the likelihood of visits from common pollinating insects.^[1]

Fire ecology

The plant is adapted to occasional prairie fire, and the suppression of such fires is detrimental.^[5] Fire may have a number of beneficial fire ecology effects on the plant, including increases in leaf and flower production and in genetic diversity.^[6]

Insect ecology

Insects that eat the plant include the milkweed beetles Tetraopes femoratus and Tetraopes tetrophthalmus and the milkweed weevils Rhyssomatus annectans and Rhyssomatus lineaticollis.^[3] This plant, like many other milkweeds, hosts the monarch butterfly (Danaus plexippus).^[3]

References

1. ^¹²³⁴⁵The Nature Conservancy
2. ^¹²³⁴Center for Plant Conservation {{webarchive |url=https://web.archive.org/web/20101215120414/http://www.centerforplantconservation.org/collection/cpc_viewprofile.asp?CPCNum=308 |date=December 15, 2010 }}
3. ^¹²³Betz, R. F. (1989). Ecology of Mead's milkweed (Asclepias meadii) Torrey. in Proceedings of the 11th North American Prairie Conference; 1989; University of Nebraska, Lincoln. p 187-191.
4. ^Grman, E. L. and H. M. Alexander. (2005). Factors limiting fruit production in Asclepias meadii in northeastern Kansas. American Midland Naturalist 153:2 245.
5. ^USFWS. Determination of threatened status for Asclepias meadii (Mead's milkweed). Federal Register September 1, 1988.
6. ^Assessment of the reintroduction potential of five federally threatened and endangered plant species at Midewin National Tallgrass Prairie, Table 3-2. USFS 1998.

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