One of the most astounding migrations on the planet begins right in our back There is a symbiotic relationship between the native milkweed plants and the monarch. The monarch butterflies enjoy the nectar from the flowers and help and other native milkweeds such as butterfly milkweed and swamp. Among these flowers are the plants monarchs live for: the milkweeds! The entire lifecycle of the monarch butterfly is dependent on the milkweed. Together, the two species have formed a beautiful relationship that has lasted for generations. One strategy to help save the butterflies has been to plant more milkweeds. That's because, each spring in North America, as monarch.
ApocynaceaeAsclepias tuberosa butterfly milkweed Gentianales: ApocynaceaeAsclepias verticillata whorled milkweed Gentianales: Apocynaceaeand Cynanchum laeve honey vine milkweed Gentianales: In greenhouse experiments, fewer larvae that fed on Asclepias hirtella and Asclepias sullivantii reached adulthood compared with larvae that fed on the other milkweed species.
Monarch pupal width and adult dry mass differed among milkweeds, but larval duration dayspupal duration dayspupal mass, pupal length, and adult wet mass were not significantly different.Milkweed & the Monarch Butterfly Life Cycle
Both the absolute and relative adult lipids were different among milkweed treatments; these differences are not fully explained by differences in adult dry mass. Although this decline may not be representative of the monarch population size during other times of the year DavisDavis and Dyerthis decline has been attributed to multiple factors including the loss of milkweed Oberhauser et al.
Recent modeling work has implicated the loss of habitat, including milkweeds, within the breeding range as the largest threat to the monarch population Zalucki and LammersFlockhart et al.
A large proportion of the monarchs that overwintered in Mexico originated from the Midwest Wassenaar and HobsonFlockhart et al. Restoration of monarch habitat in this region is essential to increase population numbers Oberhauser et al.
These projects have focused on adding milkweed plants, the only host plants of monarch larvae, to the landscape. Traditionally, row crop agriculture in the Midwest was a significant source of common milkweed A.
Virtually all habitat restoration recommendations are based on A. These other milkweed species could potentially provide a broader base of resources adapted to a wider range of sites and weather for a more sustainable approach to habitat restorations.
More information is needed about monarch larval survival and performance on these milkweeds to understand how they contribute to population growth. Several prior studies have addressed various aspects of monarch survival from larvae to adults, but few include comparative work on multiple milkweed species.
Other studies have examined growth differences of larvae that fed on A. Additional work has focused on the survival of early-instar larvae on a range of North American species native to Florida Zalucki and Browerthe Midwest Pocius et al.
Monarchs and Milkweed – The Precarious Cycle | My Altona Forest
Furthermore, Robertson et al. Because most milkweeds native to the Midwest, especially those with narrow ranges, have not been tested, we examined larval survival on nine milkweed species native to Iowa, which is a high priority area for Midwestern conservation efforts The Center for Biological Diversity The species we examined were: These species have overlapping ranges Woodsonvarying concentrations of cardenolides WoodsonRoeske et al.
We examined larval performance and survival on young plants of the nine species listed earlier to determine any differences in the resulting adults including mass, forewing length, and hindwing length, or development time days in the larval and pupal stages relative to the milkweed species on which the larvae fed.
Our prior work suggested that there were differences in both mass and lipid content in young larvae, second and third instars, that fed on both leaves and young plants of different milkweed species Pocius et al.
We suspected that these differences could change as the monarch larvae develop to adulthood because there were no significant differences in pupal weight and development time among larvae that fed on A.
Understanding how milkweed species influence monarch development and survival will be critical in choosing milkweed species for monarch habitat restoration, and given the large number of acres that are being planted, this knowledge could also have significant economic implications.
Larvae were reared on A. Upon eclosion, adults were tested for Ophryocystis elektroscirrha OE. Adults that tested negative for OE were allowed to mate and eggs were collected for propagation of the colony on a weekly basis. Twelve generations of colony breeding preceded the beginning of this experiment; inbreeding should not affect monarch preferences as colony breeding for multiple generations did not influence monarch growth or performance on different milkweeds Ladner and Altizer Milkweed Feeding Assay Milkweeds of all nine species were grown from seed without the use of chemical pesticides in a greenhouse Growing conditions represent a middle ground among the nine species tested.
Seeds were sown into cell plug trays Landmark Plastics, Akron, OH and then at approximately 6 wk following germination were transplanted into 8. Plants ranged from 10 to 30 cm in height depending on milkweed species. Milkweeds were 8 wk old when used in each trial; all plants were healthy with undamaged leaves at the start of each trial. Each plant was watered and placed into a water-filled, waxed paper cup.
One neonate was added to each plant.
The experiment was arranged in a randomized complete block design with the block including one plant of each of the nine milkweed species growing in each pop up cage. Each trial six blocks was replicated six times for a total of 36 blocks. Unfortunately, there are no substitutes for where monarchs can lay their eggs.
Swamp milkweed in Altona Forest damp growing conditions Monarch on common milkweed dry growing conditions Milkweed is a broad-leafed native plant that is used by monarchs as their only nursery.
Monarchs lay eggs on the undersides of the leaves and their larvae become striped caterpillars and feed on the leaves as they develop. Without the milkweed, the caterpillars would die — but Ontario put milkweed on the noxious weeds list which forced its eradication.
The monarch caterpillars are not affected by the mildly toxic nature of this plant and become toxic themselves which makes them less attractive prey creating their defense mechanism. Monarchs feed and breed in Ontario summers. Come colder weather, they make that astounding migration south. The south-traveling generation are by far the longest-lived of the 4 generations. It mimics the native milkweed in many ways — but cannot sustain monarchs.
It fools the monarch adults into laying eggs on it but the larvae starve since there is no nutritional value to its leaves. Nor does it provide nectar to the adults. Countless thousands butterflies die before they can ever become caterpillars or take flight. In Mexico there has been damage and logging of the only forests and trees where they overwinter, in the US there are huge tracts of industrial farms, pesticides and herbicides and neonics use where there is little wildflower food and ample danger, and in Ontario their milkweed nurseries are in dramatic decline with pesticide use, the eradication of native milkweed, and proliferation of dog-strangling vine.
Locally, we can only help the third and fourth generations — those who arrive in our yards to drink nectar and lay their eggs on milkweed, and their late-summer progeny who make the wondrous but arduous flight to Mexico.
It will take a continental perspective and effort to save them because each annual cycle of monarchs use flight corridors though Mexico, USA, and Canada.