Spatial and temporal dynamics of Batesian mimicry between Adelpha californica and Limenitis lorquini

Conspicuous coloration is one of the main ways that animals communicate. The use of eye-catching color patterns to warn predators of an unprofitable trait is referred to as aposematism. Once predators learn to recognize the color pattern, a new signaling niche becomes available where other species can share the same signal. This mimicry niche can involve a “hide in plain sight” strategy by mimicking or parasitizing this signal, with mimics lacking the defense and associated costs that make them unprofitable. This is termed Batesian mimicry, and it decreases predation by taking advantage of the memory and learning of the predator community. Thus, a primary prediction in Batesian mimicry systems is that the model and mimic are found in sympatry. Another, fundamental prediction of Batesian mimicry is that the model outnumbers the mimic and that models emerge before the mimics to educate the predator guild. Some of these patterns were not significant in the California Coast Ranges as seen in Long et al., (2015), and no study has estimated population sizes for this temperate Batesian mimicry system. Furthermore, compared with community studies of mutualistic Müllerian mimicry in the tropics, no studies have tested predictions of parasitic Batesian mimicry on small scale patterns of habitat use and movement patterns. If mimicry is as an important part of the biology of these temperate species, as it is for their tropical counterparts, we predict that in addition to emerging first and being more abundant, the model and mimic will overlap strongly in habitat but the model will be more abundant in each habitat, and will move more and be more widespread among available habitats. Our results confirm these predictions and indicate that A. californica is effectively educating habitat specialist and generalist predators providing an umbrella of protection for the mimic L. lorquini

Spatial and temporal dynamics of Batesian mimicry between Adelpha californica and Limenitis lorquini

Conspicuous coloration is one of the main ways that animals communicate. The use of eye-catching color patterns to warn predators of an unprofitable trait is referred to as aposematism. Once predators learn to recognize the color pattern, a new signaling niche becomes available where other species can share the same signal. This mimicry niche can involve a “hide in plain sight” strategy by mimicking or parasitizing this signal, with mimics lacking the defense and associated costs that make them unprofitable. This is termed Batesian mimicry, and it decreases predation by taking advantage of the memory and learning of the predator community. Thus, a primary prediction in Batesian mimicry systems is that the model and mimic are found in sympatry. Another, fundamental prediction of Batesian mimicry is that the model outnumbers the mimic and that models emerge before the mimics to educate the predator guild. Some of these patterns were not significant in the California Coast Ranges as seen in Long et al., (2015), and no study has estimated population sizes for this temperate Batesian mimicry system. Furthermore, compared with community studies of mutualistic Müllerian mimicry in the tropics, no studies have tested predictions of parasitic Batesian mimicry on small scale patterns of habitat use and movement patterns. If mimicry is as an important part of the biology of these temperate species, as it is for their tropical counterparts, we predict that in addition to emerging first and being more abundant, the model and mimic will overlap strongly in habitat but the model will be more abundant in each habitat, and will move more and be more widespread among available habitats. Our results confirm these predictions and indicate that A. californica is effectively educating habitat specialist and generalist predators providing an umbrella of protection for the mimic L. lorquini

Relative Importance of Host Abundance in Population Declines of S. adiaste

Populations of Speyeria species across North America are in decline. Possible reasons for these declines include human disturbance, loss of habitat, declines in violet host populations, drought and fire. S. adiaste is an imperiled species, being restricted to the southern California coast range, and having lost its southern-most subspecies to extinction. The purpose of this project was to study the link between violet hosts and abundance of the butterfly Speyeria adiaste clemencei to better understand its decline and aid in restoration of this and other Speyeria species. In order to assess the importance of the host plant, Viola purpurea quercetorum, in regulating adult abundance of S. a. clemecei, we compared adult population counts to projected population size given available host. We did this by combining field collected data for number of plants, number of leaves per plant, and leaf area per plant, with lab estimates of consumed leaf area to reach pupal stage. This results in an estimated average of 30,871 pupae for the 2013 Viola population on Chew’s Ridge, with 1.3% of the estimated distribution being less than 1000 pupae. In contrast the actual 2013 adult population estimate is less than 400 individuals. These results indicate that host abundance is not a strong predictor of adult abundance, although other aspects of host biology such as host density and spacing may be important. However factors totally unrelated to hosts, such as mortality from drought, predators, parasites, or disease may ultimately be driving population declines

Quantifying host plant requirements in Speyeria butterflies

Over the past century, human disturbance has led to decreases in populations of Speyeria butterflies and their native Viola hosts (Hammond, 1983). Sensitivity of Viola to human disturbance has been shown to be a large contributor to the decline in Speyeria, which play vital roles in their complex ecosystems. While Speyeria larvae are known to feed on Viola, other aspects of their larval ecology are not well understood. In order for Speyeria habitats to be sufficiently restored, an understanding of the Viola requirements necessary to sustain a butterfly population is imperative. In order to elucidate how many butterflies a specific habitat could support, the amount of host plant required to obtain a viable adult was quantified. Wild S. callippe and S. hydaspe females were obtained, and oviposition was induced in a bag containing dried host Viola. Viola papilionacea was used as a lab host because it is a readily available surrogate for wild California Viola, and its morphology is conducive to image analysis and measurement. Total leaf area consumed by all individuals was averaged to obtain an estimate of leaf area necessary for Speyeria larvae to reach adulthood. Our results indicate that larvae consume from 160 - 226 cm^2 of leaf area. Estimates of Speyeria population size and Viola leaf area available in the habitat are not currently known. Once these data are obtained, they will be used in conjunction with the amount of leaf area consumed to identify target levels of population size in populations where restoration is needed

Quantifying host plant requirements in Speyeria butterflies

Over the past century, human disturbance has led to decreases in populations of Speyeria butterflies and their native Viola hosts (Hammond, 1983). Sensitivity of Viola to human disturbance has been shown to be a large contributor to the decline in Speyeria, which play vital roles in their complex ecosystems. While Speyeria larvae are known to feed on Viola, other aspects of their larval ecology are not well understood. In order for Speyeria habitats to be sufficiently restored, an understanding of the Viola requirements necessary to sustain a butterfly population is imperative. In order to elucidate how many butterflies a specific habitat could support, the amount of host plant required to obtain a viable adult was quantified. Wild S. callippe and S. hydaspe females were obtained, and oviposition was induced in a bag containing dried host Viola. Viola papilionacea was used as a lab host because it is a readily available surrogate for wild California Viola, and its morphology is conducive to image analysis and measurement. Total leaf area consumed by all individuals was averaged to obtain an estimate of leaf area necessary for Speyeria larvae to reach adulthood. Our results indicate that larvae consume from 160 - 226 cm^2 of leaf area. Estimates of Speyeria population size and Viola leaf area available in the habitat are not currently known. Once these data are obtained, they will be used in conjunction with the amount of leaf area consumed to identify target levels of population size in populations where restoration is needed

Implications of Larval Movements in Declining Butterflies: Investigating Methods of Tracking First Instar Larvae

Morphological studies of adult Speyeria callippe have revealed extensive wing pattern variation that has been classified into 19 described subspecies. Interestingly, other sympatric Speyeria species often resemble S. callippe across its range, which extends from British Columbia to Manitoba down to northern Baja Mexico. This color pattern similarity may be the result of color pattern mimicry or crypsis. Because adult wing patterns are so variable, and potentially involved in adaptive coloration, they may obscure relationships within S. callippe and among Speyeria species generally. Immature stages are subject to different ecological pressures than adults, and may offer an independent perspective to test systematic hypotheses. Previous work in our lab has detected differences between larval morphology of subspecies from the California coast ranges compared with subspecies from mountainous regions in southern Oregon and the Sierra Nevada foothills. However, sampling was limited in the previous analysis with only a couple mountain taxa represented. This project expands sampling to examine whether consistent morphological differences exist between geographic subspecies within California, as well as outside of California. Our additional sampling of subspecies from California, Nevada, Colorado, Oregon, and Alberta allows us to reexamine 1) the correlation of larval morphology with existing subspecies taxonomy, 2) whether larval characters provide information for elucidating subspecies relationships, and 3) whether strong morphological differences exist that suggest the presence of cryptic species

Data from: Testing the adaptive hypothesis of Batesian mimicry among hybridizing North American admiral butterflies

Batesian mimicry is characterized by phenotypic convergence between an unpalatable model and a palatable mimic. However, because convergent evolution may arise via alternative evolutionary mechanisms, putative examples of Batesian mimicry must be rigorously tested. Here we used artificial butterfly facsimiles (N=4000) to test the prediction that 1) palatable Limenitis lorquini butterflies should experience reduced predation when in sympatry with their putative model, Adelpha californica, 2) protection from predation on L. lorquini should erode outside of the geographical range of the model, and 3) mimetic color pattern traits are more variable in allopatry, consistent with relaxed selection for mimicry. We find support for these predictions, implying that this convergence is the result of selection for Batesian mimicry. Additionally, we conducted mark-recapture studies to examine the effect of mimicry and found that mimics survive significantly longer at sites where the model is abundant. Finally, in contrast to theoretical predictions, we found evidence that the Batesian model (A. californica) is protected from predation outside of its geographic range. We discuss these results considering the ongoing hybridization between L. lorquini and its sister species, L. weidemeyerii, and growing evidence that selection for mimicry predictably leads to a reduction in gene flow between nascent species

Testing the adaptive hypothesis of Batesian mimicry among hybridizing North American admiral butterflies: BATESIAN MIMICRY

Batesian mimicry is characterized by phenotypic convergence between an unpalatable model and a palatable mimic. However, because convergent evolution may arise via alternative evolutionary mechanisms, putative examples of Batesian mimicry must be rigorously tested. Here, we used artificial butterfly facsimiles (N = 4000) to test the prediction that (1) palatable Limenitis lorquini butterflies should experience reduced predation when in sympatry with their putative model, Adelpha californica, (2) protection from predation on L. lorquini should erode outside of the geographical range of the model, and (3) mimetic color pattern traits are more variable in allopatry, consistent with relaxed selection for mimicry. We find support for these predictions, implying that this convergence is the result of selection for Batesian mimicry. Additionally, we conducted mark–recapture studies to examine the effect of mimicry and found that mimics survive significantly longer at sites where the model is abundant. Finally, in contrast to theoretical predictions, we found evidence that the Batesian model (A. californica) is protected from predation outside of its geographic range. We discuss these results considering the ongoing hybridization between L. lorquini and its sister species, L. weidemeyerii, and growing evidence that selection for mimicry predictably leads to a reduction in gene flow between nascent species

idaho_attacks_norodent_dryad

All Model Attack information from Idaho 2016 model experiment, this dataset (used for the paper) has the ambiguous "rodent-like" attacks mentioned in the paper removed