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Analysis of Transect Counts to Monitor Population Size in Endangered Insects The Case of the El Segundo Blue Butterfly, Euphilotes Bernardino Allyni
Abstract and Figures
Before, during and after habitat restoration from 1984 to 1994, we monitored population size of the federally listed endangered El Segundo blue butterfly, Euphilotes bernardino allyni (Shields). In the subsequent formalization of a recovery plan for the species, the U.S. Fish and Wildlife Service established several recovery criteria, including a requirement of a scientifically credible monitoring plan to track population size annually. To avoid detrimental effects of the extensively used mark-release-recapture method on the delicate El Segundo blue butterfly, which would conflict with protection afforded by the Endangered Species Act, we chose instead to perform transect counts to estimate relative population size. Herein, we analyze the results of our transect counts by three different methods, developed by or modified from Pollard, Watt et al. and Zonneveld. Qualitatively, the three methods, which have different assumptions, produced similar results when applied to the same data. Zonneveld's model estimates death rate in addition to an index of population size, thus providing more information than the other two methods. The El Segundo blue butterfly's sedentary nature and the close relationship of its adult and early stages to one foodplant permits extrapolation of the index of population size based on transect counts, to an estimate of actual population size. Our data document butterfly numbers increasing from 1984 to 1989, but then declining until the end of our observations in 1994. Based on analysis of our El Segundo blue butterfly data, we propose an implementation of a scientifically credible monitoring plan.
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... Such surveys, if they are exhaustive across the target habitat, can document spatial distribution of females after release (Mattoni et al. 2002). Adult surveys should be continued each year following the release following USFWS protocols for at least five years and estimates of abundance made from these data (Mattoni et al. 2001;Watt et al. 1977;Zonneveld et al. 2003). These data can also be used to track the geographic variation in site use by adult butterflies if converted to a grid across the site (see Longcore et al. 2010). ...
... Regular transect surveys can be used to develop estimates of population size in the event that releases result in successful colonization and reproduction. Notwithstanding the problems with population estimates that lack detectability estimators (Haddad et al. 2008;Nowicki et al. 2008), population estimates based on transect counts, and even peak transect count numbers have been shown to provide reliable information (Collier et al. 2008;Haddad et al. 2008;Isaac et al. 2011;Mattoni et al. 2001). Despite the suggestion that distance sampling be incorporated into butterfly transect counts, this has not proven feasible for endangered species because of the low number of butterflies observed is usually inadequate to parameterize the detectability estimates. ...
... In Britain, indices for multiple-brooded butterflies usually vary more than for single-brooded ones, with the Karner blue's variability at the upper range found in Pollard and Yates (1993). In ten years of transect counts of a single-brooded blue, annual indices varied by an average 2.35 factor in consecutive years at individual sites and by 1.48 for the five sites combined (Mattoni et al. 2001): 20-30% less variability than we found for the spring brood and 50-60% less than/ the summer brood, but following our pattern of reduction with increasing geographic scale. ...
... We recorded 13778 Karner blues in 430 km of peak surveys. Relative abundance indices derived from transect counts (single or multiple counts per site per generation) covary strongly with estimates of absolute numbers (line-transect or mark-release-recapture), both in studies of Karner blues ( Boyce 1998, King 2000) and other butterflies (Pollard 1977, Thomas 1984, Mattoni et al. 2001 ). Relative abundance indices have the advantage of allowing more sites to be sampled in the same amount of time compared to methods for estimating absolute numbers (King 2000). ...
We analyzed geographic patterns of Karner blue (Lycaeides melissa samuelis
Nabokov, Lepidoptera: Lycaenidae) population fluctuations in summer broods in
central and northwestern Wisconsin and spring+summer broods in central Wisconsin.
We removed possible effects of population trends by analyzing residuals
from a regression of each site’s population index vs. year. We then calculated
correlation coefficients (r) of these residuals for all site-pairs separately for 1992-
2005 (26 sites, N = 325 site-pairs), 1995-2005 (21 sites, N = 210), and 1998-2005
(14 sites, N = 91). We analyzed patterns in these r values relative to distance
between sites using correlations vs. distance and using pairwise comparisons of
different distance categories (0-3 km up to 223-264 km apart). Karner blues
showed significant (P < 0.05) population synchrony over all distances. Spatial
autocorrelation was strongest among sites <3 km apart, then gradually leveled off
at greater distances. Statistical power increased when we added three years but
the number of sites did not decrease greatly (1995-2005 vs. 1998-2005 analyses)
and when using an annual index combining spring+summer indices instead of
just summer. The spatial autocorrelation extending over the entire study region
suggests that environmental factors like weather provide some synchronization
of Karner blue populations. Their much higher local synchrony is consistent with
the species’ short dispersal distance. Their local and regional spatial
autocorrelation increases the likelihood of correlated local extinctions during low
fluctuation broods, especially when these coincide with unfavorable weather or
adverse habitat events.
... While declines in butterfly diversity and abundances are well documented in southern California (Arnold 1987;Mattoni et al. 2001;Bonebrake and Cooper 2014;Forister et al. 2016;Crone et al. 2019), the effects of common habitat modifications on butterfly assemblages are poorly understood. In low elevation areas of southern California, the two primary landscape modifications are: ...
Insects are in decline globally with Lepidoptera identified as one of the most impacted taxa. While declines in butterfly diversity in southern California are well documented, the effects of common habitat and climate modifications on butterfly assemblages are poorly understood. To better understand how to best monitor changes in butterfly richness and assemblage structure in southern California and examine how common habitat and climate (drought) modifications influence butterfly assemblages, we assessed data from our first six years of monthly butterfly biomonitoring efforts at the Robert J. Bernard Field Station (BFS) in eastern Los Angeles County. Monthly surveys span five habitats: (1) native sage scrub, (2) non-native grassland, (3) burned area, recovering vegetation after a 2013 fire, (4) lake, vegetation next to an artificial lake, and (5) edge habitat, which includes both sage scrub and adjacent suburban areas. Our results highlight that long-term (> 5 years) butterfly monitoring is required to inventory butterfly richness in habitat fragments in southern California and to assess differences in assemblages among habitats. At the BFS, butterfly assemblages differed markedly among the five habitat types with butterfly richness highest in native sage scrub and lowest in the non-native grassland, suggesting type-conversion has deleterious effects on regional butterfly assemblages. In contrast, drought, defined as years with < 75% of average annual rainfall, was a poor predictor of butterfly richness and assemblage structure. While drought seems to have little direct impact on butterfly assemblages, type-conversion represents a significant contemporary threat to regional butterfly assemblages and likely pollinator diversity. Our results highlight that long-term (> 5 year) butterfly monitoring is required to inventory butterfly richness and assess differences in assemblages among habitats. Further, we demonstrate that type-conversion from native sage scrub to non-native grasslands represents a significant threat to regional butterfly assemblages, and likely pollinator diversity.
... Before de-extinction efforts are considered for this species, it will be important to consider the ecological and evolutionary costs and benefits [12]. The Xerces blue butterfly is an icon for insect extinction and conservation, and the question remains whether the financial and time investment in potentially resurrecting this species outweigh the investment in protecting other butterfly species and habitats that are currently in sharp decline, such as those of the El Segundo Blue, Euphilotes battoides allyni [13,14], or the Karner Blue, Lycaeides melissa samuelis [15,16]. Competing interests. ...
The last Xerces blue butterfly was seen in the early 1940s, and its extinction is credited to human urban development. This butterfly has become a North American icon for insect conservation, but some have questioned whether it was truly a distinct species, or simply an isolated population of another living species. To address this question, we leveraged next-generation sequencing using a 93-year-old museum specimen. We applied a genome skimming strategy that aimed for the organellar genome and high-copy fractions of the nuclear genome by a shallow sequencing approach. From these data, we were able to recover over 200 million nucleotides, which assembled into several phylogenetically informative markers and the near-complete mitochondrial genome. From our phylogenetic analyses and haplotype network analysis we conclude that the Xerces blue butterfly was a distinct species driven to extinction.
... While some species in these groups are morphologically distinct, most are better delimited by a combination of genitalia characteristics, host plant associations, adult phenology, and geographic occurrences (Opler and Wright 1999). Within the E. battoides group, some species assignments are debated, including that of E. battoides allyni, which some treat as a subspecies of E. bernardino (Mattoni et al. 2001;Shields and Reveal 1988), and whether E. bernardino is a distinct species or a subspecies of E. battoides (Pratt and Emmel 1998;Scott 1986). Here, our sampling primarily targeted E. battoides allyni found on Er. parvifolium in coastal regions, and E. bernardino bernardino (E. ...
Phylogeographic patterns in phytophagous organisms are often contextualized in light of geographic isolation and ecological (host, habitat) specialization. However, assessing the relative impact of these phenomena is not straightforward, even in areas where phylogeography is well-studied, such as the California Floristic Province. Here, we use genome-wide markers to elucidate population genomic and phylgeographic patterns for a group of monophytophagous butterflies in southern California. This group is of high conservation interest because it includes the El Segundo blue, Euphilotes battoides allyni, one of the first insects listed under the U.S. Endangered Species Act, and a newly discovered population putatively assigned to E. b. allyni. Despite using the same unique host and coastal habitat, our results indicate that the newly discovered populations are not E. b. allyni and are more closely related to geographically proximate populations of the E. battoides group using a different habitat/host combination. Aside from E. b. allyni and the newly discovered populations, the rest of the group shows only fine-scale structure and apparently maintains genetic connectivity throughout southern California, across a vast range of habitats and climates, and on multiple hosts. Thus, habitat and host specialization did not elicit genetic isolation in neighboring populations suggesting that: (1) other phenomena are needed to explain the remarkable and idiosyncratic divergence of these highly restricted, proximate, taxa, and (2) fine-scale genomic markers suggest broader implications for understanding the mechanisms of speciation and reinvestigation of phylogeographic patterns in regions like the California Floristic Province.
... Relative abundance indices derived from transect counts (single or multiple counts per site per generation) covary strongly with estimates of absolute numbers (line-transect or mark-release-recapture), both in studies of Karner Blues [52,53] and other butterflies [48,50,54]. Relative abundance indices have the advantage of allowing more sites to be sampled in the same amount of time compared to methods for estimating absolute numbers [53]. ...
We monitored consecutive generations of three lupine-feeding specialist butterflies in pine-oak barrens in central Wisconsin, USA: Frosted Elfin (Callophrys irus), Karner Blue (Lycaeides melissa samuelis), and Persius Duskywing (Erynnis persius) during 1991–2014. We also monitored the summer generation of Karner Blues in northwestern Wisconsin. We present results on 24 sites for Frosted Elfin and Persius Duskywing, and 39 sites for Karner Blue. Land uses in sites occupied by the federally endangered Karner Blue are regulated. Economically utilized lands classified as “Shifting Mosaic” (SM) (forestry land) or “Permanency of Habitat” (PH) (rights-of-way) are afforded a lower standard of conservation results than the more favorable management expected of Reserves (R). For all three species, reserve sites had more favorable trends than permanency of habitat and shifting mosaic sites. Frosted Elfin and Persius Duskywing had more strongly negative trends in permanency of habitat than shifting mosaic, but vice versa for Karner Blue. Shifting mosaic sites added more recently to the study had negative trends, but not as strongly as longer-monitored shifting mosaic sites. Another large shifting mosaic complex (Hunter Haven), monitored in 17 years during 1995–2014 for Frosted Elfin and Persius Duskywing, had non-negative trends. Individual reserve sites also had more favorable trends than collectively for all reserve sites, including significant positive trends for Persius Duskywing and Karner Blue, and a stable trend for Frosted Elfin. Thus, land use is implicated not only for declines but also for effective conservation of these species.
... Some urban habitats, such as road verges, brownfield sites or recreational parks, may function as surrogates for habitats already absent from intensively managed lands (Valtonen et al. 2007;Lundholm and Richardson 2010). These habitat types may in fact represent a Blast stand^for some rangerestricted species, particularly in the tropics and subtropics, trapped within expanding urban areas (Mattoni et al. 2001). ...
Rapid economic development has accelerated urbanisation and biodiversity loss in Southeast Asia. Studies of urban ecology have suggested urban parks can be effective refuges for wildlife in temperate regions, but their effectiveness as refuges in rapidly urbanising tropical regions is understudied. We examined the species diversity of butterflies in urban parks in the Federal Territory of Kuala Lumpur and investigated the relationships between butterfly species richness and three park variables: i) park size, ii) distance from the central business district and iii) park age. Standardised butterfly sampling was conducted across different microhabitat types at each park: i) groves, ii) hedges, iii) flowerbeds and iv) unmanaged areas. We recorded 572 butterflies belonging to 60 species (97 % considered common) from five families. Although species richness was positively correlated with park size and age and negatively correlated with distance from the central business district; the correlations were weak and not statistically significant. However, species richness of host-specialist species was significantly positively correlated with park size and age. The highest species richness (65 % of observed species) was recorded in the unmanaged microhabitat. It is likely that both park planting scheme and the presence of early successional plants in unmanaged microhabitat led to highest butterfly species richness in parks that contained all four microhabitat types. Whether a diverse planting scheme and increased size and number of unmanaged areas in urban parks can improve the ability of parks to sustain populations of rare butterflies in the face of future urbanisation remains to be seen.
Monitoring programs constitute a suitable approach to evaluate habitat quality over time. Nonetheless, the success of such programs rests on data quality and adequacy of management practices. Long-term monitoring should be used to generate robust data that can be used as baseline information for effective implementation of mitigating actions. Although monitoring initiatives have produced successful results in temperate regions, their replication is Brazil is particularly challenging due to this country’s high diversity and land extension. The expansion of activities that promote economic growth is a real threat to environmental protection. As a result, habitat Conservation units in Brazil are under pressure, thus compromising their effectiveness as protected areas that conserve natural habitats. In this paper, we explain why butterflies are a reliable group as biological indicators for environmental monitoring programs. Additionally, we discuss how butterflies may be used in the management of Conservation Units and environmental monitoring in local scales, using the Program “Programa de Monitoramento in situ da Biodiversidade” as an example. We believe that butterflies can serve a flagship group for the maintenance of such programs in Brazil by providing a means of obtaining reliable data, and also being a link between conservation biologists and members of the society. This can be achieved through activities such as the direct contact with butterflies, and integration of laypeople in programs that involve collecting data for monitoring programs.
Two independent temporal cohorts of Euphilotes ancilla (Lepidoptera: Lycaenidae) with different larval host plants occur sympatrically in portions of the Spring Mountains of southern Nevada. Their diapause intensities (as determined in the laboratory) and flight seasons exhibit little or no overlap, but phenotypes of the cohorts appear identical. It is speculated that they arose from changes in the relative phenology of their larval host plants in response to climatic alterations subsequent to the Pleistocene. Although these Euphilotes seem to behave as separate biological entities, their taxonomic level remains equivocal. Until more information is forthcoming, they are recognized as separate subspecies: E. ancilla purpura and E. ancilla cryptica n. ssp.
Monitoring long-term population change is an integral part of effective conservation-oriented research and management, and is central to the current debate on the status of Neotropical migrant land birds. However, the analysis of count data such as the Breeding Bird Survey is complicated by the subjective nature of trend estimation, and by limitations inherent to extensive, volunteer-based surveys, such as measurement error and missing data. A number of analysis methods have been used that differ in their approach to dealing with these complications and produce different estimates of population change when applied to the same data. There is, however, no consensus as to which method is the most suitable. Many analytical issues remain unresolved, such as model of trend, observer effects, treatment of missing observations, distribution of counts, and data selection criteria. These issues make it difficult to evaluate the relative merits of the methods, although a number of new approaches (nonlinear regression, Poisson regression, estimating equations estimates) offer promising solutions to some problems. I suggest the use of Monte Carlo simulations to empirically test the performance of the methods under realistic, spatially explicit scenarios of population change, and provide an example of the approach.
With the listing of the quino checkerspot butterfly, Euphydryas editha quino, as a federally endangered species, research into its ecology and conservation is necessary to allow for recovery planning and manage- ment. We review systematics, distribution, natural history, and conserva- tion prospects, with reference to pertinent literature about other E. editha subspecies. Additional information is presented from museum specimens and ongoing research on the species.
In many butterfly species, females mate only once, whereas males are capable of multiple matings. As a result, males compete intensely for access to females. To maximize their expected mating success, males emerge some time before the females. This phenomenon, known as protandry, is widespread but not ubiquitous. Protandry is negatively correlated with polyandry (i.e., repeated female mating) and male size. Since male size and development time are interdependent, several hypotheses can be advanced to explain the observed correlations. Either large size is especially important in polyandrous species, or early emergence is of lesser importance. So far, models of protandry have neglected the trade-off between large size and early emergence. In this article, I present models that account for this trade-off and the interaction with polyandry. In polyandrous species, females use male-derived nutrients to enhance realized fecundity. Since large males produce large ejaculates, there will be a selection pressure for large male size, counterbalancing the selection for early emergence. Given this hypothesis, the correlations among protandry, polyandry, and relative male size can be explained, Finally, the conditions under which polyandry is likely to evolve are discussed.
The Palos Verdes blue butterfly (PVB) was believed extinct for eleven years when a small colony was rediscovered by accident on March 10,1994 at a site from which it had not been recorded earlier. The systematics and natural history of the species (=subspecies for conservation purposes), its historic and present habitat, and plans necessary for its recovery are discussed.
A method based on transect count has been developed to assess changes in abundance of butterflies from year to year. The method involves weekly walks around atransect route making counts of butterflies seen within defined limits. The transects are divided into sections related to habitat or management units. Walks are made only when weather conditions satisfy specified minimum requirements. The method has been tested for three years at Monks Wood and for two years at a number of other sites.The basis for annual comparisons is an index of abundance which is produced for each brood of each species, except when separation of broods is not possible. This index is correlated with abundance, although the precise nature of the relationship will vary from species to species. Evidence on this presented for two species.The method makes it possible to monitor the abundance of butterflies at selected sites, using recorders, such as nature reserve wardens, who can fit in one or two hours recording each week when the weather is suitable. Such a scheme, based on the methods described in this paper, began in 1976. In addition to the monitoring of fluctuations of abundance, the method provides considerable information on the phenology and ecology of butterflies. The division of the transects into sections makes some assessment of the effects of habitat change, due to management or other factors, possible.
1. Monitoring schemes for butterflies in the United Kingdom and the Netherlands are aimed at the detection of long-term trends. It is useful to examine the power of these schemes to detect trends in a given period of time. 2. The approach was based on an ANOVA-model, and the trends were compared with the random population changes from one year to another. Several assumptions were made for simplicity's sake: autocorrelation in the data was ignored and only linear trends in log 10 (N + 1) transformed data were examined. 3. The relevant variance components to examine were the year-to-year variances and year-by-site variances. These were estimated from the time series of the British Butterfly Monitoring Scheme. Year-to-year variances appeared to be higher in northern Britain than in other regions. In addition, variance components were related to the voltinism of species. 4. Power assessment was based on the estimates of variance components and on tile number of sampling sites. In the British scheme, for 37 out of 51 species studied a decrease of 50% or less is detectable with a power of 80% within a 20-year period. In the Dutch scheme such a decrease is delectable for 29 out of 47 species. 5. Because the schemes lack power for a number of species, several strategies are discussed to enhance power. For species present at less than 25 sites, it is most effective to increase the number of sampling sites where they are present, if that is possible in practice. But for species that are present at more than 50 sites, a further increase hardly improves the power. For these species, it is more efficient to adjust the data for weather conditions than to increase the number of sites. 6. The assumptions we made hardly affect the results for common species. But for rare species the results are more or less questionable. To get better estimates of the power, methods to assess power for monitoring schemes need to be developed that treat count data as discrete random variables.