Tracking trends in monarch abundance over the 20th century is currently impossible using museum records
Tracking trends in monarch abundance over the 20th century is currently impossible using museum records
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目前无法利用博物馆记录追踪 20 世纪帝王蝶丰度的趋势
DOI：
10.1073/pnas.1904807116
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Guralnick, Robert P.
中科院分区：
文献类型：
--
作者：
Ries, Leslie;Zipkin, Elise F.;Guralnick, Robert P.
机会性数据提供了一个诱人的机会来检查大时空尺度上的生物多样性模式（1）。最近的方法学进步有望利用这些数据来估计趋势，同时也突出了准确评估偏倚的困难（2-5）。这样做的目的是确定在一个合理的可比时间和地点内收集的类似物种的总数，以纠正取样工作的变化。利用标本数据收集机会，波义耳等人。(6)表明帝王蝶的数量在本世纪中期增加，然后从20世纪60年代开始减少。然而，他们的分析使用了不适当的修正，涉及到3个维度的努力：分类，地点和时间。当这些数据被重新标准化以解释收集过程中的偏差时（图1），没有出现世纪中期的丰度峰值（图2）。在PNAS中，Wepprich（7）证明了波义耳等人提出的模式。(6)可以用20世纪50年代蛾类博物馆记录的激增来解释。蛾类记录一般不应用于校正蝴蝶物种分析，因为大多数蛾类的采集过程（夜间灯光诱捕）与蝴蝶的采集过程（白天的网捕）有很大不同。在这里，我们还解决了收集过程中的时空偏差的问题。减少这种偏差的一种方法是将分析限制在物种分布最均匀和持续丰富的核心范围和一年中的时间。超出核心范围的记录不会增加重要信息，但会增加收集偏差的风险，这可能导致虚假模式。迁徙帝王蝶的东部种群在夏季繁殖季节达到最高丰度和最一致的分布（图1A;所示数据来自标准化的北美蝴蝶协会夏季调查[可在Dryad获得; doi：10.5061/dryad。2548jb4]）。将丰度估计限制在其核心空间和时间范围内已被证明与越冬群体大小最相关（8-10）。(6)，我们排除了蛾（可在Dryad中获得; doi：10.5061/dryad。2548 jb 4），然后与所有其他蝴蝶相比，检查帝王蝶采集地点的模式（图1B）。即使在将分析限制在物种的核心范围（图1中的绿色边界）之后，我们也发现标本数据中存在压倒性的空间和时间偏差。所有夏季帝王蝶记录的一半（51%）集中在明尼苏达州和新英格兰的两个限制集群中，大多数标本是在非常有限的年份内采集的（图1B）。使用校正后的数据，我们没有发现20世纪中期的丰度峰值（图2）。请注意，经过适当的校正，每年的平均观测次数只有2.3次，中位数为1次（图2C）。在波义耳等人的研究中，(6)这是利用机会性数据跟踪人口趋势的一个警示故事。由于有限的数据可用性和压倒性的时空收集偏见（图。1B和2），使用数字化博物馆记录来追踪上个世纪的帝王蝶种群目前是不可能的。我们强烈支持继续努力收集蝴蝶标本，这最终可能为探索帝王蝶种群的长期趋势提供适当的基础。
Opportunistic data provide a tantalizing opportunity to examine patterns in biodiversity over large spatiotemporal scales (1). Recent methodological advancements hold promise for utilizing such data to estimate trends while also highlighting the difficulty in accurately assessing biases (2–5). The idea is to determine the total number of collections of similar species within a reasonably comparable time and place to correct for variations in sampling effort. Using specimen data collected opportunistically, Boyle et al.(6) show a midcentury increase in monarch abundance followed by a decrease starting in the 1960s. However, their analysis used an inappropriate correction with respect to 3 dimensions of effort: taxonomy, place, and time. When these data are restandardized to account for biases in the collection process (Fig. 1), there is no midcentury peak in abundance (Fig. 2). In PNAS, Wepprich (7) demonstrates that the pattern presented by Boyle et al.(6) could be explained by a spike in moth museum records in the 1950s. Moth records should generally not be used to correct for butterfly species analyses because the collection process for most moths (light trapping at night) is substantially different than for butterflies (net captures during the day). Here, we additionally address the issue of spatiotemporal bias in the collection process. One way to reduce this bias is to restrict analysis to the core range and time of year when the species is most evenly distributed and consistently abundant. Records falling outside core range do not add significant information but risk collection biases, which can lead to spurious patterns. The eastern population of the migratory monarch reaches their highest abundance and most consistent distribution during the summer breeding season (Fig. 1A; data shown are from standardized North American Butterfly Association summer surveys [available in Dryad; doi: 10.5061/dryad. 2548jb4]). Constraining abundance estimates to their core spatial and temporal extent has been shown to best correlate to overwinter colony sizes (8–10).Using the same dataset as Boyle et al.(6), we excluded moths (available in Dryad; doi: 10.5061/dryad. 2548jb4) and then examined patterns in monarch collection locations compared with all other butterflies (Fig. 1B). Even after confining the analysis to species’ core range (green boundary in Fig. 1), we found overwhelming spatial and temporal bias in the specimen data. Half of all summer monarch records (51%) were accumulated in 2 restricted clusters in Minnesota and New England, with most specimens collected during a very limited number of years (Fig. 1B). We find no mid-20th–century peak in abundance when using the corrected data (Fig. 2). Note that with appropriate correction, the average number of observations per year is only 2.3 monarchs, with a median of 1 (Fig. 2C). The spurious pattern presented in Boyle et al.(6) represents a cautionary tale in the use of opportunistic data to track population trends. Because of limited data availability and overwhelming spatiotemporal collection biases (Figs. 1B and 2), using digitized museum records to track monarch butterfly populations over the last century is currently not possible. We strongly support continued efforts to digitize butterfly specimens which may eventually provide the proper basis to explore long-term monarch population trends.
帝王蝶的趋势对博物馆藏品随时间的未经审查的变化很敏感
DOI：
10.1073/pnas.1903511116
发表时间：
2019
期刊：
Proceedings of the National Academy of Sciences
影响因子：
--
作者：
Tyson Wepprich
通讯作者：
Tyson Wepprich
东部迁徙人口夏季和冬季君主趋势之间的脱节：不同驱动因素的可能联系
DOI：
--
发表时间：
2015
期刊：
影响因子：
--
作者：
L. Ries;D. Taron;Eduardo Rendón
通讯作者：
Eduardo Rendón
DOI：
10.1073/pnas.1218503110
发表时间：
2013-03-19
影响因子：
11.1
作者：
Bartomeus, Ignasi;Ascher, John S.;Winfree, Rachael
通讯作者：
Winfree, Rachael