Capturing Spatiotemporal Patterns in Presence-Absence Data to Inform Monitoring and Sampling Designs for the Threatened Dakota Skipper (Lepidoptera: Hesperiidae) in the Great Plains of the United States

Abstract

Declines among species of insect pollinators, especially butterflies, has garnered attention from scientists and managers. Often these declines have spurred governments to declare some species as threatened or endangered. We used existing presence–absence data from surveys for the threatened Dakota skipper Hesperia dacotae (Skinner) to build statistical maps of species presence that could be used to inform future monitoring designs. We developed a hierarchical Bayesian modeling approach to estimate the spatial distribution and temporal trend in Dakota skipper probability of presence. Our model included a spatial random effect and fixed effects for the proportion of two grassland habitat types: those on well-drained soils and those on poorly drained soils; as well as the topographic slope. The results from this model were then used to assess sampling strategies with two different monitoring objectives: locating new Dakota skipper colonies or monitoring the proportion of historically (pre-2000) extant colonies. Our modeling results suggested that the distribution of Dakota skippers followed the distribution of remnant grasslands and that probabilities of presence tended to be higher in topographically diverse grasslands with well-drained soils. Our analysis also showed that the probability of presence declined throughout the northern Great Plains range. Our simulations of the different sampling designs suggested that new detections were expected when sampling where Dakota skippers likely occurred historically, but this may lead to a tradeoff with monitoring existing sites. Prior information about the extant sites may help to ameliorate this tradeoff.

Point‐scale habitat and weather patterns influence the distribution of regal fritillaries in the central United States

“…Our analysis of 4JC data indicated that regal use of count circles appeared to be influenced by a combination of land cover, weather, and other spatial variables across the central United States. Generally speaking, our model findings are consistent with other studies investigating land cover as an indicator of butterfly habitat quality, and thus abundance (Early et al, 2008; Perović et al, 2015; Pogue et al, 2016; Post van der Burg et al, 2020; Slancarova et al, 2014). Specifically, the effects of both grassland and forest cover appear consistent with other studies of regal occurrence and indicate that regals prefer to use locations surrounded by grassland with little to no tree cover (Caven et al, 2017; McCullough et al, 2019; Powell et al, 2007; Ries & Debinski, 2001; Selby, 2007).…”

“…In reality, it is highly unlikely that regals would use any grassland other than a pristine native prairie. Our spatial spline terms could be representing other sources of spatial autocorrelation not attributable to habitat surrogates (Post van der Burg et al, 2020;Royle & Wikle, 2005). For example, it is possible that the smoothing spline terms are capturing some, currently unidentified, habitat factor that appears to These estimates included a model for abundance (β) and detection probability (α).…”

Comparing Two Species Distribution Models Using Satellite Only and Ready-Made Environmental Variables for the Dakota Skipper (Hesperia dacotae), Interlake Region of Manitoba, Canada

“…Four recent SDMs have been created for the Dakota skipper, however, all four used a mixture of common and satellite imagery derived environmental variables (Table 1). Three of the studies were situated in regions outside of the Manitoba Interlake area (Post van der Burg et al 2020;Seidle et al 2020;Barnes et al 2024). The study by Seidle et al (2020) was created for a region in south-western Saskatchewan and the study by Barnes et al (2024) Post van der Burg et al (2020) was applied to three and four US states, respectively.…”

“…Past Dakota skipper research in Manitoba, Saskatchewan and the northern U.S. has generally focused on describing local biotic and abiotic site characteristics (Dana 1991;Rigney 2013;Seidle et al 2018) as well as some preliminary SDM studies to determine potential habitat range of Dakota skipper and Poweshiek skipperling, Oarisma poweshiek (Westwood et al 2019;Post van der Burg et al 2020;Seidle et al 2020;Dearborn et al 2022) including additional modelling response to climate change (Barnes et al 2024).…”