Lawrence W. Sheppard's research while affiliated with University of Kansas and other places

Publications (34)

Preprint
Understanding intraspecific variation in habitat use, particularly of long-lived fishes across multiple life history stages, is core to improved conservation management. Here, we present results from a synthesis of acoustic telemetry data for sub-adult and adult white sturgeon (Acipenser transmontanus) from 2010 to 2017 in the San Francisco Estuary...
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Spatial synchrony is a ubiquitous and important feature of population dynamics, but many aspects of this phenomenon are not well understood. In particular, it is largely unknown how multiple environmental drivers interact to determine synchrony via Moran effects, and how these impacts vary across spatial and temporal scales. Using new wavelet stati...
Article
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Understanding movement patterns of anadromous fishes is critical to conservation and management of declining wild populations and preservation of habitats. Yet, the duration of observations for individual animals can constrain accurate descriptions of movements. In this study, we synthesized over a decade (2006–2018) of acoustic telemetry tracking...
Article
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Spatial synchrony may be tail‐dependent, that is, stronger when populations are abundant than scarce, or vice‐versa. Here, ‘tail‐dependent’ follows from distributions having a lower tail consisting of relatively low values and an upper tail of relatively high values. We present a general theory of how the distribution and correlation structure of a...
Article
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The spatial distribution of dengue and its vectors (spp. Aedes ) may be the widest it has ever been, and projections suggest that climate change may allow the expansion to continue. However, less work has been done to understand how climate variability and change affects dengue in regions where the pathogen is already endemic. In these areas, the w...
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Synchronous dynamics (fluctuations that occur in unison) are universal phenomena with widespread implications for ecological stability. Synchronous dynamics can amplify the destabilizing effect of environmental variability on ecosystem functions such as productivity, whereas the inverse, compensatory dynamics, can stabilize function. Here we combin...
Preprint
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Background Understanding movement patterns of anadromous fishes is critical to conservation management of declining wild populations and preservation of habitats. Yet, infrequent observations of individual animals fundamentally constrain accurate descriptions of movement dynamics. Methods In this study, we synthesized over a decade (2006–2018) of...
Article
Understanding the processes that stabilize species populations is a fundamental question in ecology and central to conservation biology. In metapopulations, dispersal can act as a ‘double edged' sword for species stability by simultaneously decreasing local population variability (thereby decreasing local extinction risk) while increasing spatial s...
Preprint
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The spatial distribution of dengue and its vectors (spp. Aedes) may be the widest it has ever been, and projections suggest that climate change may allow the expansion to continue. However, the largest impacts of climate change on dengue might be in regions where the pathogen is already endemic. In these areas, the waxing and waning of immunity has...
Article
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Population cycles are fundamentally linked with spatial synchrony, the prevailing paradigm being that populations with cyclic dynamics are easily synchronised. That is, population cycles help give rise to spatial synchrony. Here we demonstrate this process can work in reverse, with synchrony causing population cycles. We show that timescale‐specifi...
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Standard methods for studying the association between two ecologically important variables provide only a small slice of the information content of the association, but statistical approaches are available that provide comprehensive information. In particular, available approaches can reveal tail associations, that is, accentuated or reduced associ...
Article
Fluctuations in population abundances are often correlated through time across multiple locations, a phenomenon known as spatial synchrony. Spatial synchrony can exhibit complex spatial structures, termed ‘geographies of synchrony’, that can reveal mechanisms underlying population fluctuations. However, most studies have focused on spatial extents...
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Extreme climatic events (ECEs) are becoming more frequent and more intense due to climate change. Furthermore, there is reason to believe ECEs may modify "tail associations" between distinct population vital rates, or between values of an environmental variable measured in different locations. "Tail associations" between two variables are associati...
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Understanding the mechanisms governing ecological stability—why a property such as primary productivity is stable in some communities and variable in others—has long been a focus of ecology. Compensatory dynamics, in which anti‐synchronous fluctuations between populations buffer against fluctuations at the community level, are a key theoretical mec...
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• Periodical cicadas exhibit an extraordinary capacity for self‐organizing spatially synchronous breeding behavior. The regular emergence of periodical cicada broods across the United States is a phenomenon of longstanding public and scientific interest, as the cicadas of each brood emerge in huge numbers and briefly dominate their ecosystem. Durin...
Chapter
All branches of ecology study relationships among and between environmental and biological variables. However, standard approaches to studying such relationships, based on correlation and regression, provide only some of the complex information contained in the relationships. Other statistical approaches exist that provide a complete description of...
Article
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1. Spatial synchrony, the tendency for temporal population fluctuations to be correlated across multiple locations at regional scales, is common and contributes to the severity of outbreaks and epidemics, but is little studied in agricultural pests. 2. This study analysed spatial synchrony from 1974 to 2008 in 16 lepidopteran agricultural pests in...
Preprint
Full-text available
Understanding the mechanisms governing ecological stability - why a property such as primary productivity is stable in some communities and variable in others - has long been a focus of ecology. Compensatory dynamics, in which anti-synchronous fluctuations between populations buffer against fluctuations at the community level, is a key theoretical...
Preprint
Full-text available
All branches of ecology study relationships among environmental and biological variables. However, ubiquitously used approaches to studying such relationships, based on correlation and regression, provide only a small slice of the complex information contained in the relationships. Other statistical approaches exist that provide a complete descript...
Article
Full-text available
Large-scale spatial synchrony is ubiquitous in ecology. We examined 56 years of data representing chlorophyll density in 26 areas in British seas monitored by the Continuous Plankton Recorder survey. We used wavelet methods to disaggregate synchronous fluctuations by timescale and determine that drivers of synchrony include both biotic and abiotic...
Article
1.Taylor's law (TL), a commonly observed and applied pattern in ecology, describes variances of population densities as related to mean densities via log(variance)=log(a)+b*log(mean). Variations among datasets in the slope, b, have been associated with multiple factors of central importance in ecology, including strength of competitive interactions...
Article
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Spatial synchrony is defined by related fluctuations through time in population abundances measured at different locations. The degree of relatedness typically declines with increasing distance between sampling locations. Standard approaches for assessing synchrony assume isotropy in space and uniformity across timescales of analysis, but it is now...
Article
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Taylor's law (TL) is a widely observed empirical pattern that relates the variances to the means of groups of nonnegative measurements via an approximate power law: variance g ≈ a [Formula: see text] mean g b , where g indexes the group of measurements. When each group of measurements is distributed in space, the exponent b of this power law is...
Article
Full-text available
Spatial synchrony, defined as correlated temporal fluctuations among populations, is a fundamental feature of population dynamics, but many aspects of synchrony remain poorly understood. Few studies have examined detailed geographical patterns of synchrony; instead most focus on how synchrony declines with increasing linear distance between locatio...
Article
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Background. The use of wavelet coherence methods enables the identification of frequency-dependent relationships between the phases of the fluctuations found in complex systems such as medical and other biological timeseries. These relationships may illuminate the causal mechanisms that relate the variables under investigation. However, computation...
Article
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During the 1980s the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer-water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and h...
Article
Full-text available
Spatial synchrony, the tendency of distant populations to fluctuate similarly, is a major concern in ecology(1-8). Except in special circumstances(3,9), researchers historically had difficulty identifying drivers of synchrony in field systems(5,6,10). Perhaps for this reason, the possibility(9,11,12) that changes in large-scale climatic drivers may...
Conference Paper
Background/Question/Methods It is well known that in theory spatially synchronous fluctuations in abundance can result from spatially synchronous fluctuations in the environment: this is known as the Moran effect. The challenge is to identify environmental drivers in real systems and demonstrate the Moran effect in action. Phytoplankton abundance...

Citations

... The relationship between regional kelp dynamics and decadal marine climate oscillations [6,55,56] produce multiyear periods of high (or low) kelp canopy that make the identification of long-term trends difficult [18]. Additionally, a recent analysis has shown that the synchrony of giant kelp canopy is highly coherent with the North Pacific Gyre Oscillation on long time scales (4 to 10 years; [57]), meaning that sites within regions tend to increase and decrease similarly according to the fluctuations of the large-scale ocean climate. Since regular oscillatory patterns make the detection of long-term trends difficult [18,58], perhaps the most beneficial use for these . ...
... The A. aegypti fatty acid synthase 1 (AaFAS1) may play a role in the transmission of dengue (Chotiwan et al. 2022). During the high temperatures of climate, the immune dynamics of dengue are highly predominant and may become asynchronous (García-Carreras et al. 2022). There are different mechanisms for the dengue hemorrhagic fever (DHF) and shock syndrome of dengue (DSS), which are often fatal (Medin et al. 2005;Carr et al. 2003;Bosch et al. 2002). ...
... To address the potential effects of timescale on our analyses, we considered stability and its underlying mechanisms at three timescales of 5-, 10-, and 15-year moving windows. In particular, synchronous dynamics are timescale dependent phenomena and our results show that synchrony dominated at shorter timescales (Supplementary Figures S2B, S7), consistent with evidence in grasslands that synchrony is stronger at short timescales, while asynchronous dynamics often dominate at longer timescales (Zhao et al., 2020;Shoemaker et al., 2022). Despite this, stability declined when calculated over longer timescales, likely reflecting the intuitive outcome that including more years in the calculation leads to a higher chance of including more variation. ...
... Second, the NEON dataset covers a relatively short observational period, which also differs among sites (4-8 yr) 44 . Previous studies suggested that the length of time series might influence the estimate of temporal stability [46][47][48] . However, our additional analyses suggest that time-series length had no effect on diversity, stability and their relationships in our study (Fig. 2, Extended Data Figs. 5 and 6 and Supplementary Tables 1, 2 and 14). ...
... Tail-dependent spatial synchrony represents a new extension of spatial synchrony's general negative implications for the stability of population ensembles (Anderson et al., 2021;Heino et al., 1998;Schindler et al., 2015). Because of the implications of taildependent spatial synchrony for the tendency towards synchronised booms versus synchronised crashes, understanding the nature of tail associations and how they vary spatially can help explain patterns of temporal stability. ...
... Here, 'tails' refers to the upper or lower portions of a variable's distribution. Tail-dependent associations between ecological and environmental variables are common (Ghosh et al., 2020a), including in the context of synchrony among interacting species in a community (Ghosh et al., 2020b(Ghosh et al., , 2021. However, tail dependence in spatial synchrony has been little studied, so its prevalence, mechanisms, and consequences in empirical populations are not yet well understood. ...
... Despite the importance of synchrony, three major aspects remain poorly understood: (1) Populations may be synchronised to different extents on different timescales (i.e. periods of fluctuations, such as annual or decadal) or during specific, transient periods (Keitt, 2008;Vasseur et al., 2014;Walter et al., 2020;Walter, Hallett, et al., 2021), but traditional approaches often ignore or misidentify such temporal complexity (Anderson et al., 2019Defriez et al., 2016;Desharnais et al., 2018;Sheppard et al., 2016Sheppard et al., , 2019. (2) Synchrony can differ regionally, but most investigations overlook geographical patterns in synchrony and their underlying drivers (Anderson et al., 2019;Koenig et al., 2017;Walter et al., 2017Walter et al., , 2022. ...
... However, tail dependence in spatial synchrony has been little studied, so its prevalence, mechanisms, and consequences in empirical populations are not yet well understood. In principle, tail-dependent spatial synchrony should have substantial implications for extinction risk (Ghosh et al., 2020c). An ensemble of populations exhibiting stronger interpopulation associations in the upper tails of population distributions will have spatially synchronised population booms, leading to widespread periods of high abundance, but populations exhibiting stronger associations in their lower tails will experience synchronised crashes. ...
... lachnantha, P. stramineum, L. nutans, T. triandra, and P. mezianum) were identified from Porensky et al. (2013) as the species composing 85% of herbaceous cover. To investigate the effects of timescale on asynchrony, we used the timescale specific variance ratio which decomposes the classic variance ratio into timescales of distinct contributions (Zhao et al., 2020). Dominant species population stability: We calculated population temporal stability (S p ) as S p = µ σ , where µ is the temporal mean of a species' cover divided by the standard deviation, σ, for each of the five dominant species individually. ...
... In addition to such multi-year synchrony, males in one species, Magicicada cassini, align their songs, 1 s 'buzzes' with a repetition rate ≈0.2 s −1 , with high precision. Simultaneous recordings at multiple locations in a chorus extending over many hectares showed that synchronous alignment, termed 'phase coherence', of the male songs was highest for pairs of locations separated by short distances and fell off as inter-location distance increased [52]. The fall-off with distance was much greater than what would be expected from delays simply reflecting the time for sound transmission, ≈1 s over a 343 m distance. ...