Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient
The eastern migratory population of monarch butterflies has experienced a multi-decadal decline, but a recent increase in abundance (to 6.05 ha in winter 2018) has led some observers to question whether the population has reversed its long-standing decline and embarked on a trajectory of increasing...
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doaj-3d17ce4fbe0d4f13bf293e05d906b2132020-11-25T02:15:42ZengFrontiers Media S.A.Frontiers in Ecology and Evolution2296-701X2020-02-01810.3389/fevo.2020.00043462946Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently InsufficientWayne E. Thogmartin0Jennifer A. Szymanski1Emily L. Weiser2U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, United StatesU.S. Fish and Wildlife Service, Endangered Species Program, La Crosse, WI, United StatesU.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, United StatesThe eastern migratory population of monarch butterflies has experienced a multi-decadal decline, but a recent increase in abundance (to 6.05 ha in winter 2018) has led some observers to question whether the population has reversed its long-standing decline and embarked on a trajectory of increasing abundance. We examined this possibility through changepoint analyses, assessing whether a change in trajectory existed over a 25-year times series. We found evidence of a change in trajectory in 2014, but insufficient statistical support for a significantly increasing population since that time (β = 0.285, 95% CI = −0.127, 0.697). If the population estimate for winter 2019 is ≥4.0 ha, we will then be able to credibly assert the population has been increasing since 2014. However, given estimated levels of time series variability, presumed habitat capacity and no recent change in status or trend, there was a 13.5% probability of observing a population estimate as large or larger than was reported for winter 2018. Our analyses highlight the incredible difficulty in drawing robust conclusions from annual changes in abundance over a short time series, especially for an insect that commonly exhibits considerable year-to-year variation. Thus, we urge caution when drawing conclusions regarding species status and trends for any species for which limited data are available.https://www.frontiersin.org/article/10.3389/fevo.2020.00043/fullchangepointDanaus plexippusextinction risksmall datapopulation ecologytime series analyses |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Wayne E. Thogmartin Jennifer A. Szymanski Emily L. Weiser |
spellingShingle |
Wayne E. Thogmartin Jennifer A. Szymanski Emily L. Weiser Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient Frontiers in Ecology and Evolution changepoint Danaus plexippus extinction risk small data population ecology time series analyses |
author_facet |
Wayne E. Thogmartin Jennifer A. Szymanski Emily L. Weiser |
author_sort |
Wayne E. Thogmartin |
title |
Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient |
title_short |
Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient |
title_full |
Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient |
title_fullStr |
Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient |
title_full_unstemmed |
Evidence for a Growing Population of Eastern Migratory Monarch Butterflies Is Currently Insufficient |
title_sort |
evidence for a growing population of eastern migratory monarch butterflies is currently insufficient |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Ecology and Evolution |
issn |
2296-701X |
publishDate |
2020-02-01 |
description |
The eastern migratory population of monarch butterflies has experienced a multi-decadal decline, but a recent increase in abundance (to 6.05 ha in winter 2018) has led some observers to question whether the population has reversed its long-standing decline and embarked on a trajectory of increasing abundance. We examined this possibility through changepoint analyses, assessing whether a change in trajectory existed over a 25-year times series. We found evidence of a change in trajectory in 2014, but insufficient statistical support for a significantly increasing population since that time (β = 0.285, 95% CI = −0.127, 0.697). If the population estimate for winter 2019 is ≥4.0 ha, we will then be able to credibly assert the population has been increasing since 2014. However, given estimated levels of time series variability, presumed habitat capacity and no recent change in status or trend, there was a 13.5% probability of observing a population estimate as large or larger than was reported for winter 2018. Our analyses highlight the incredible difficulty in drawing robust conclusions from annual changes in abundance over a short time series, especially for an insect that commonly exhibits considerable year-to-year variation. Thus, we urge caution when drawing conclusions regarding species status and trends for any species for which limited data are available. |
topic |
changepoint Danaus plexippus extinction risk small data population ecology time series analyses |
url |
https://www.frontiersin.org/article/10.3389/fevo.2020.00043/full |
work_keys_str_mv |
AT wayneethogmartin evidenceforagrowingpopulationofeasternmigratorymonarchbutterfliesiscurrentlyinsufficient AT jenniferaszymanski evidenceforagrowingpopulationofeasternmigratorymonarchbutterfliesiscurrentlyinsufficient AT emilylweiser evidenceforagrowingpopulationofeasternmigratorymonarchbutterfliesiscurrentlyinsufficient |
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