A trans‐national monarch butterfly population model and implications for regional conservation priorities

Oberhauser, Karen S.; Wiederholt, Ruscena; Diffendorfer, James E.; Semmens, Darius J.; Ries, Leslie; Thogmartin, Wayne E.; López‐Hoffman, Laura; Semmens, Brice X.

doi:10.1111/een.12351

Cited by 126 publications

(136 citation statements)

References 29 publications

Supporting

Mentioning

133

Contrasting

Order By: Relevance

“…We do not dispute the need to engage in conservation efforts during all phases of the migratory cycle of monarchs (see also [24]), but our analysis shows that milkweed limitation during summer breeding is the major driver of monarch decline and there is no evidence that there has been increasing mortality during migration. Thus, at a time when federal and state agencies and local groups and individuals are making major efforts to plant milkweeds, it is imperative that the science behind these efforts be clear.…”

Section: Discussionmentioning

confidence: 80%

Interpreting surveys to estimate the size of the monarch butterfly population: Pitfalls and prospects

et al. 2017

Self Cite

View full text Add to dashboard Cite

To assess the change in the size of the eastern North American monarch butterfly summer population, studies have used long-term data sets of counts of adult butterflies or eggs per milkweed stem. Despite the observed decline in the monarch population as measured at overwintering sites in Mexico, these studies found no decline in summer counts in the Midwest, the core of the summer breeding range, leading to a suggestion that the cause of the monarch population decline is not the loss of Midwest agricultural milkweeds but increased mortality during the fall migration. Using these counts to estimate population size, however, does not account for the shift of monarch activity from agricultural fields to non-agricultural sites over the past 20 years, as a result of the loss of agricultural milkweeds due to the near-ubiquitous use of glyphosate herbicides. We present the counter-hypotheses that the proportion of the monarch population present in non-agricultural habitats, where counts are made, has increased and that counts reflect both population size and the proportion of the population observed. We use data on the historical change in the proportion of milkweeds, and thus monarch activity, in agricultural fields and non-agricultural habitats to show why using counts can produce misleading conclusions about population size. We then separate out the shifting proportion effect from the counts to estimate the population size and show that these corrected summer monarch counts show a decline over time and are correlated with the size of the overwintering population. In addition, we present evidence against the hypothesis of increased mortality during migration. The milkweed limitation hypothesis for monarch decline remains supported and conservation efforts focusing on adding milkweeds to the landscape in the summer breeding region have a sound scientific basis.

show abstract

Section: Discussionmentioning

confidence: 80%

Interpreting surveys to estimate the size of the monarch butterfly population: Pitfalls and prospects

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…Summer breeding success does not appear to be affected by changing climate (Stenoien et al 2016), but monarch populations could be impacted by climate change via increases in extreme weather events during overwintering or reduced rainfall and concomitant decrease in milkweed abundance in the southern spring breeding grounds (Oberhauser et al 2017). Conservation efforts must focus on the life history stages that affect population dynamics to be effective; for a long-ranging migratory species like the monarch, these can occur thousands of kilometres apart across major biomes and jurisdictions, greatly increasing the challenges of conservation.…”

Section: Monarch Butterflymentioning

confidence: 99%

Effects of phenological synchronization on caterpillar early-instar survival under a changing climate

Despland

2018

Can. J. For. Res.

View full text Add to dashboard Cite

Early-instar caterpillars experience very high and often very variable mortality; if it is density dependent, it can be a key factor in outbreak dynamics. Plant physical and chemical defenses can be extremely effective against young caterpillars, even of specialists. Phenological asynchrony with host plants can lead to dispersal and mortality in the early instars and increased predation or poor nutrition in later instars. Predation on early-instar larvae (including cannibalism) can be extremely high, parasitism appears generally low, and pathogens acquired early in larval development can lead to high mortality in later stadia. Four well-studied species reveal very different roles of early-instar mortality in population dynamics. In spruce budworm and gypsy moth, early-instar mortality rates can be very high; they do not drive outbreak cycles because density dependence is weak, but can modulate cycles and contribute to outbreak size and duration. For the autumnal moth, early-instar survival depends on host plant synchrony, but may or may not be density dependent. For monarch butterflies, the relative importance of larval mortality rates in population dynamics remains unclear. Tritrophic interactions between herbivores, host plants, natural enemies, and microbes play complex and species-specific roles in early-instar ecology, leading to emergent dynamics in population fluctuations. The phenology of these relationships is often poorly understood, making their responses to climate change unpredictable.Key words: Lepidoptera, hatchlings, synchronization, outbreaks.Résumé : Les chenilles des premiers stades larvaires connaissent des taux de mortalité très élevés et souvent très variables; si ces taux varient avec la densité, ils peuvent devenir un facteur clé dans la dynamique des épidémies. Les défenses physiques et chimiques des plantes sont souvent extrêmement efficaces contre les jeunes chenilles, même celles des espèces spécialisées. L'asynchronie phénologique avec les plantes hôtes peut entraîner la dispersion et la mortalité chez les premiers stades larvaires, et une augmentation de la prédation ou une mauvaise nutrition chez les derniers stades larvaires. La prédation lors des premiers stades larvaires (incluant le cannibalisme) peut être extrêmement élevée, le parasitisme semble généralement faible et les pathogènes qui infectent tôt dans le développement des larves peuvent entraîner un taux de mortalité élevé chez les stades ultérieurs. Quatre espèces bien étudiées révèlent différents rôles de la mortalité chez les premiers stades larvaires dans la dynamique des populations. Chez la tordeuse des bourgeons de l'épinette et la spongieuse, les taux de mortalité peuvent être très élevés chez les premiers stades larvaires; ils n'ont pas d'effet déterminant sur les cycles épidémiques parce que la dépendance à la densité est faible, mais ils peuvent moduler les cycles et contribuer à l'ampleur et à la durée des épidémies. Dans le cas de l'épirrite automnale, la survie des premiers stades larvaires dépend ...

show abstract

“…, Oberhauser et al. , Weeks ). This approach is suitable for species for which we have tracking data from a number of individuals, but it is otherwise difficult to parameterize individual‐based models.…”

Section: Introductionmentioning

confidence: 98%

Comparing abundance distributions and range maps in spatial conservation planning for migratory species

Johnston

Auer

Fink

et al. 2020

Ecological Applications

View full text Add to dashboard Cite

Most spatial conservation planning for wide‐ranging or migratory species is constrained by poor knowledge of species’ spatiotemporal dynamics and is only based on static species’ ranges. However, species have substantial variation in abundance across their range and migratory species have important spatiotemporal population dynamics. With growing ecological data and advancing analytics, both of these can be estimated and incorporated into spatial conservation planning. However, there is limited information on the degree to which including this information affects conservation planning. We compared the performance of systematic conservation prioritizations for different scenarios based on varying the input species’ distributions by ecological metric (abundance distributions versus range maps) and temporal sampling resolution (weekly, monthly, or quarterly). We used the example of a community of 41 species of migratory shorebirds that breed in North America, and we used eBird data to produce weekly estimates of species’ abundances and ranges. Abundance distributions at a monthly or weekly resolution led to prioritizations that most efficiently protected species throughout the full annual cycle. Conversely, spatial prioritizations based on species’ ranges required more sites and left most species insufficiently protected for at least part of their annual cycle. Prioritizations with only quarterly species ranges were very inefficient as they needed to target 40% of species’ ranges to include 10% of populations. We highlight the high value of abundance information for spatial conservation planning, which leads to more efficient and effective spatial prioritization for conservation. Overall, we provide evidence that spatial conservation planning for wide‐ranging migratory species is most robust and efficient when informed by species’ abundance information from the full annual cycle.

show abstract

A trans‐national monarch butterfly population model and implications for regional conservation priorities

Abstract: This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Cited by 126 publications

References 29 publications

Interpreting surveys to estimate the size of the monarch butterfly population: Pitfalls and prospects

Interpreting surveys to estimate the size of the monarch butterfly population: Pitfalls and prospects

Effects of phenological synchronization on caterpillar early-instar survival under a changing climate

Comparing abundance distributions and range maps in spatial conservation planning for migratory species

Contact Info

Product

Resources

About