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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #355921
Research Project: Managing Insects in the Corn Agro-Ecosystem

Location: Corn Insects and Crop Genetics Research

Title: Estimating arthropod survival probability from field counts: a case study with monarch butterflies

Author
item GRANT, TYLER - Iowa State University
item FLOCKHART, TYLER - University Of Maryland
item BLADER, TERESA - Iowa State University
item Hellmich Ii, Richard
item PITTMAN, GRACE - University Of Guelph
item TYNER, SAM - Iowa State University
item NORRIS, D. RYAN - University Of Guelph
item BRADBURY, STEVEN - Iowa State University

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2020
Publication Date: 4/21/2020
Citation: Grant, T.J., Flockhart, T., Blader, T.R., Hellmich, R.L., Pittman, G.M., Tyner, S., Norris, D.R., Bradbury, S.P. 2020. Estimating arthropod survival probability from field counts: a case study with monarch butterflies. Ecosphere. 11(4). https://doi.org/10.1002/ecs2.3082.
DOI: https://doi.org/10.1002/ecs2.3082

Interpretive Summary: Estimating survival probability of animals requires marking individuals. Marking methods, however, are not practical for insects and other arthropods because a marking is lost when an individual molts and replaces the exoskeleton. We developed a novel way to estimate survival probability of arthropods based on Bayesian statistics. A model was developed that estimates larval survival probability from stage-structured count data for which stage duration is predicted with supplementary data. The model was applied to the monarch butterfly (Danaus plexippus), a declining species in North America for which conservation programs are being implemented. The model was used to estimate survival from larval monarch counts collected at four field sites in Iowa, USA, and Ontario, Canada. Cumulative survival probability estimates are approximately three to twenty-five-fold lower than previous published estimates. This model can readily be adapted to other arthropod species with similar life histories. A population dynamics model based on survival probabilities will be useful for making decisions related to arthropod conservation.

Technical Abstract: Methods for estimating survival probability of organisms from field data typically require marking individuals. Marking methods are not practical for arthropod species, however, which molt their exoskeleton between life history stages. We developed a novel Bayesian state-space model to estimate larval survival probability from stage-structured count data for arthropod species for which stage duration can be predicted with ancillary data. The model was applied to the monarch butterfly (Danaus plexippus), a declining species in North America for which conservation programs are being implemented. We performed simulation studies to evaluate estimation bias due to detection probability, individual variation in stage duration, and study design (sampling frequency and sample size). Estimation of cumulative survival probability from oviposition to pupation was most robust to potential sources of bias. Our simulation studies provide guidance for designing studies with minimal bias. We used the model to estimate survival from larval monarch counts collected at four field sites in Iowa, USA, and Ontario, Canada. Cumulative survival probability estimates are approximately three to twenty-five-fold lower than previous published estimates. This model can readily be adapted to other arthropod species with stage-structured life histories.