Prof. Myron Zalucki
Editor’s note: Populations of the migratory monarch butterfly have been decimated in the USA, partly due to the destruuckiction of it’s host plant, the milkweed, with herbicides. There is currently a campaign in the USA to attempt to bolster the waning populations of the monarchs. They migrate from overwintering habitats in Mexico to Canada in the spring and migrate back in the fall. The campaign involves the growing of milkweed plants along the flyway. I I have a personal interest in the saving of the beautiful monarchs which annually grace my garden so I have requested Prof. Myron Zalucki, an expert on the monarch, to summarize the latest information on the fate of the monarch.
I am also pleased to announce that Prof. Zalucki will be a Keynote speaker and will present a Plenary lecture at the XVIII IPPC, Berlin:
Wednesday, 26 August 2015: Raising and sustaining productivity of plant production systems
Plenary lecture: Landscapes, genetically modified crops and climate change: Whither IPM?
I hope to meet you in Berlin!
E. A. Heinrichs
IAPPS Secretary General
Recent” research activities related to Monarch butterflies.
Recent research has focused on the effects of climate on monarch spread (invasion of Europe) and abundance (in North America), as well as the possible mechanism behind monarch decline in North America related to herbicide tolerant crops.
Monarchs spread across the Atlantic in the middle and late 1800s. Although monarch sightings on the Azores, Madeira, Canary Islands, the British Islands, Gibraltar, and Portugal were first reported during these times, and milkweed (Gomphocarpus spp. and Asclepias curassavica) had been naturalized in many of these localities much earlier, breeding populations did not seem to establish until much later. With colleagues at the University of Cordoba (Juan Fernández Haeger and Diego Jordano) we have documented the introduction, establishment, distribution, and abundance of monarchs in Europe and North Africa based on an analysis of the historic literature, estimated climatic suitability, and our own surveys. Populations are now well established in the southern Iberian Peninsula and North Africa in areas that have been predicted to be climatically suitable. In southern Spain monarchs breed year round in a metapopulation of milkweed patches restricted to areas where the plants can survive the dry summer. We predict that monarchs may continue to spread throughout the Mediterranean, colonizing areas that are climatically suitable and have milkweed established. The greatest threat to the persistence of the species is campaigns to eradicate milkweeds. This work will appear as a chapter in an upcoming book “Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly” edited by Karen Oberhauser, Kelly Nail and Sonia Altizer.
Monarch butterflies in North America have been steadily declining for some time now. This decline has been variously attributed to the destruction of overwintering sites in Mexico, climate effects and changes in the agricultural landscape due to genetically modified crops. Using a CLIMEX model that estimates the seasonal distribution of the abundance of monarch butterflies anywhere in the world Lincoln Brower, Stephen Malcolm, Ben Slager and myself have estimated the effect of climate on long-term population dynamics in North America. We use daily maximum and minimum temperatures and rainfall from 1970 to 2010 for 25 locations that cover the breeding range across eastern North America to generate a series of abundance indices. Although there is considerable variation in the population indices over this period, no systematic trend due to climate on monarch breeding populations was detected. We conclude that the observed decline in overwintering populations is due to other factors; most likely forest degradation at overwintering locations and the loss of milkweed populations in breeding habitats from widespread agricultural use of herbicides and genetically engineered soybean and corn crops. However, climate impacts on mortality during spring and autumn migrations, and at overwintering sites cannot be ruled out with our model. This work will appear also as a chapter in “Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly”.
Soybean and corn crops genetically modified to be tolerant to glyphosate now dominate the Monarch butterflies summer breeding range in North America. As a consequence milkweed abundance has declined dramatically. We developed a spatially-implicit (Zalucki & Lammers 2010) and spatially-explicit individual-based model to describe host seeking behaviour over the lifetime of a monarch butterfly, which utilizes hosts both aggregated in patches and scattered across the wider landscape as a substrate for laying eggs (Zalucki et al. 2015). In the latter model we examine the simulated movement distances and spatial population distribution (eggs laid) as a result of different movement rules (directionality), perceptive distance (ability to find) and landscape configuration (how milkweed is distributed). Both modelling approaches indicate the potential consequences of cleaning up the matrix (i.e. the obliteration of non-crop vegetation with Roundup) and changing habitat configurations at a landscape scale on individual movement behaviours and the emergent number of eggs laid, essentially the birth term in any population model. Our models suggest milkweed removal has reduced egg laying by up to 30% and suggest possible amelioration strategies.
Haeger, J.F., Jordano, D. and Zalucki, M.P. 2015. Monarchs across the Atlantic Ocean: what’s happening on the other shore? In: Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly” edited by K. Oberhauser, K. Nail and S. Altizer. Cornell University Press.
Zalucki, M.P. and Lammers, J. H. 2010. Dispersal and egg shortfall in Monarch butterflies: what happens when the matrix is cleaned up? Ecological Entomology 35: 84-91.
Zalucki, M.P., Brower, L.P., Malcolm, S.B. and Slager, B.H. 2015. Estimating the climate signal in monarch population decline: no direct evidence for an impact of climate change? In: Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly” edited by K. Oberhauser, K. Nail and S. Altizer. Cornell University Press.
Zalucki, M.P., Parry, H. & Zalucki, J.M. 2015. Movement and egg laying in Monarchs: To move or not to move, that is the equation. Austral Ecology (in press)
Prof Myron (Meron) P. Zalucki
School of Biological Sciences
The University of Queensland