Western Subspecies Research Articles

Spread of yellow-bill-color alleles favored by selection in the long-tailed finch hybrid system

Carotenoid pigments produce the yellow and red colors of birds and other vertebrates. Despite their importance in social signaling and sexual selection, our understanding of how carotenoid ornamentation evolves in nature remains limited. Here, we examine the long-tailed finch Poephila acuticauda, an Australian songbird with a yellow-billed western subspecies acuticauda and a red-billed eastern subspecies hecki, which hybridize where their ranges overlap. We found that yellow bills can be explained by the loss of C(4)-oxidation, thus preventing yellow dietary carotenoids from being converted to red. Combining linked-read genomic sequencing and reflectance spectrophotometry measurements of bill color collected from wild-sampled finches and laboratory crosses, we identify four loci that together explain 53% of variance in this trait. The two loci of largest effect contain the genes CYP2J19, an essential enzyme for producing red carotenoids, and TTC39B, an enhancer of carotenoid metabolism. A paucity of protein-coding changes and an enrichment of associated upstream variants suggest that the loss of C(4)-oxidation results from cis-regulatory evolution. Evolutionary genealogy reconstruction indicates that the red-billed phenotype is ancestral and that yellow alleles at CYP2J19 and TTC39B first arose and fixed in acuticauda approximately 100 kya. Yellow alleles subsequently introgressed into hecki less than 5 kya. Across all color loci, acuticauda-derived variants show evidence of selective sweeps, implying that yellow bill coloration has been favored by natural selection. Our study illustrates how evolutionary transitions between yellow and red coloration can be achieved by successive selective events acting on regulatory changes at a few interacting genes.

Phylogeography of the Sinica Group of Macaques in the Himalayas: Taxonomic and Evolutionary Implications.

Owing to the taxonomic incongruence between the morphological features and genetic relationships of the sinica group of macaques (genus Macaca), the taxonomy of this macaque group has remained inconclusive. We aimed to resolve the taxonomic quandary and improve our understanding of the historical biogeography of the group by including macaque DNA samples from previously unsampled areas in the Himalayas. We sequenced and analyzed three mitochondrial DNA loci [cytochrome b (CYTB), cytochrome oxidase subunit 1 (COI) and D-loop; 2898 bp] for sequence polymorphism, phylogenetics, species delimitation, and ancestral area reconstruction. We confirmed the occurrence of Arunachal macaque (Macaca munzala) on the southern slopes of the Eastern Himalayas in the Xizang Zizhiqu (Tibet Autonomous Region) of China. The results revealed that the sinica group of macaques is a parapatric species group composed of seven distinct species. Phylogenetic and species delimitation analyses revealed that the two previously considered subspecies of Assamese macaques (the eastern subspecies M. assamensis assamensis and the western subspecies M. a. pelops) are two distinct species. The eastern Assamese macaque is a sister species to the Tibetan macaque, whereas the western Assamese macaque and Arunachal macaque are the closest genetic sister species. The sinica group of macaques underwent five vicariance and seven dispersal radiations in the past, which mainly coincided with the Quaternary climatic oscillations between the late Pliocene and the late Pleistocene. By integrating our phylogenetic and ancestral area reconstruction results with findings from previous paleontological and molecular studies, we propose a robust hypothesis about the phylogeography of the sinica group of macaques.

Taxonomic revision of the Pirate Perches, Aphredoderus, (Percopsiformes: Aphredoderidae) with descriptions of two new species.

Pirate Perches, Aphredoderus, are a widespread lowland freshwater fish native to the Eastern half of the United States. Aphredoderus was thought to contain a single species divided into an Eastern and Western subspecies on either side of the Appalachian Mountains with a widespread intergrade zone through much of the Eastern Gulf of Mexico and Southern Atlantic drainages. We use morphology and genetic data from specimens spanning the entire range of the genus to determine species limits within Aphredoderus. We find evidence of five species, four of which exhibit widespread sympatry in the Southeastern United States. We elevate A. sayanus sayanus and A. sayanus gibbosus to species, redescribe A. mesotrema, supplement previous descriptions, and describe two new species, A. retrodorsalis, and A. ornatus.

Weak Population Genetic Structure of the Eurasian Crane <i>Grus grus</i> L.

The article presents an extended (as compared with our previous studies) analysis of the population genetic structure of a migratory wide-range bird species with a high abundance, the Eurasian Crane Grus grus L. Using seven highly polymorphic microsatellite loci, high and very similar values of genetic diversity parameters were obtained in the samples of both the western (G. g. grus) and eastern (G. g. lilfordi) subspecies. Coefficients of genetic differentiation between these subspecies (FST = 0.008, GST = 0.002) were also found to be low. According to AMOVA, 99% of genetic variation of G. grus is attributed to individual levels. Using the Bayesian clustering algorithm implemented in STRUCTURE software, no clear population-genetic structuring of the species was revealed. However, visualization of spatial patterns of genetic variability in Geneland showed the presence of a cluster of “pure” subspecies G. g. grus and G. g. lilfordi surrounding a cluster of individuals from the zone of intergradation of these subspecies. This result, along with the observed very low FST values, may indicate subtle genetic differences between cranes from the studied area, possibly having a mutational nature. The lower allelic richness and lack of private alleles in the eastern subspecies suggest that G. g. lilfordi is relatively evolutionary young and suggest its recent origin from some eastern marginal populations of the nominative western subspecies.

Collected to extinction? History and records of the Western Rufous Bristlebird

The Rufous Bristlebird Dasyornis broadbenti is a species endemic to Australia and now found only in Victoria and South Australia. The enigmatic western subspecies, Western Rufous Bristlebird D. b. litoralis, was described in 1901 and is now considered extinct. Because of the paucity of information on this subspecies, I aimed to locate all known museum specimens, document its known range and ecology, and ascertain the key drivers of its decline. In total, 16 specimens were collected between 1901 and 1907, with no definitive evidence of its survival subsequently. The Western Rufous Bristlebird occupied a very small range between Cape Naturaliste and Cape Mentelle, Western Australia, and was seemingly extirpated within a 7-year period, potentially by over-collecting, because of its small area of occupancy and likely strong territoriality. Habitat change wrought by fire and clearing, as well as feral predators, were additive stressors. Putative sightings in 1945 and the 1970s, 1980s and to present times, have continued but all are unsubstantiated.

An Evaluation of Western Chicken Turtle (Deirochelys reticularia miaria) Survey and Capture Protocols

The behaviors and activity season of Deirochelys reticularia miaria (Western Chicken Turtle) are poorly understood in Texas. Though distribution of D. r. miaria in the eastern portion of the state is widespread, turtle assemblage studies conducted within the range of the species in Texas have seldom documented its presence. There is a lack of formal protection for this subspecies and their habitat, and past research suggests that remaining habitat within the state is under threat from increasing urbanization. Therefore, the US Fish and Wildlife Service issued a 90-day finding that states listing the subspecies as threatened or endangered may be warranted. To provide survey recommendations for the western subspecies, we review species-wide capture techniques from the literature, recommend a survey season for D. r. miaria in Texas, and evaluate the efficacy and potential demographic biases of capture protocols implemented during field studies in the state in 2018 and 2019. We compared road surveys, dipnet surveys, seine surveys, night wading surveys, and two types of unbaited fyke net trap. Fyke nets were effective in every study that deployed them and captured D. r. miaria in this study at a rate of 0.25 captures per trap night. Dipnet surveys had the highest capture rate among active survey methods, but body size biases between methods were apparent. In Texas, road surveys yielded significantly lower capture rates than all other survey types. The best survey method selection will vary depending on research questions, budget, and time constraints. Utilizing proper survey protocols and understanding the activity season are crucial for performing effective studies on this species.

Geographical variation in Black Redstart Phoenicurus ochruros (S. G. Gmelin, 1774) calls

Black Redstart Phoenicurus ochruros occurs over a broad range from Western Europe and north-west Africa to Central Asia. Seven subspecies are usually recognised, which can be divided morphologically into a grey-and-white-bellied western group (‘Western Black Redstart’; two subspecies) and an orange-bellied eastern group (‘Eastern Black Redstart’; five subspecies). Because vocalisations might help to understand relationships between these taxa, we analysed the calls of six of the seven subspecies. We demonstrate that calls can be grouped into one of three geographical variants. One is formed by the western subspecies breeding in Europe, the morphologically intermediate subspecies ochruros and Eastern Black Redstarts from the Altai and Mongolia. Further south-east, birds call at lower frequencies on average and within a smaller frequency range (group 2). The third group is formed by the eastern subspecies rufiventris which differs from all other taxa, with a descending instead of a rising call, given at much lower frequencies.

The Painted Bunting: A Songbird Facing Multiple Threats

The Painted Bunting: A Songbird Facing Multiple Threats Charles E. Konrad The Painted Bunting is unquestionably the most colorful songbird in the southern United States (cover photo, Figure 1). The male exhibits dazzling splashes of blue, green, yellow, and red plumage, and the reserved female possesses a solid coat of bright green, which blends in with the brush and trees where the nest is located. Because of its limited geographical range and stealthy nature, relatively few birders have experienced the delight of seeing this bird, and its dramatically declining population (Dybas 2018) has further reduced the chances of spotting it. Click for larger view View full resolution Figure 1. Painted Bunting taken at Huntington Beach State Park in South Carolina on May 16, 2022. [End Page 293] The Painted Bunting is categorized into two subspecies that are nearly identical in appearance but display distinct geographical distributions separated by a distance on the order of 500 km (Yirka et al. 2021). The eastern subspecies, Passerina ciris, breeds in a region that stretches from coastal North Carolina to northern Florida and includes an inland area in southern South Carolina and southeastern Georgia. The western subspecies, Passerina pallidior, breeds in a region extending from coastal Louisiana and Texas northward to southeastern Kansas and southern Missouri (Yirka et al. 2021). During the fall, the eastern population migrates southward to southern Florida and portions of the Bahamas and Cuba, while the western population migrates to portions of coastal Mexico and Central America. Given their geographic separation, these two populations no longer interact or breed, suggesting that the Painted Bunting will eventually divide into two different bird species (Dybas 2018). Within its breeding region, the Painted Bunting is typically present in bushy areas and woodland edges, often staying hidden within the dense cover of the vegetation. The males may be spotted by looking in the direction of their warbling songs during the breeding season. They often appear on an exposed perch higher up in the brush or trees. While the male sings out to announce its territory, the female typically remains hidden in the brush near the nest. In suitable habitats, both the male and female may be seen frequenting bird feeders. There has been a concerning decline in the number of Painted Buntings over the last fifty-plus years. According to the Breeding Bird Survey, the bird’s combined eastern and western populations have declined about 55 percent over the last thirty years (Dybas 2018). Springborn and Meyers (2005) report that the estimated number of individuals in the eastern population, Passerina ciris, decreased by about 75 percent between 1966 and 1996. Since 1996, this population has become so sparse in places that it is difficult to get a handle on the population trends across the southeastern US (Meyers 2011). Concern for the decline in the eastern and western populations of the bird species prompted the U.S. Fish and Wildlife Service and Partners in Flight (Springborn and Meyers 2005) to identify the Painted Bunting as a “species of concern” and a “near threatened” species. Several factors have been tied to the decline in Painted Bunting populations. Habitat loss in the summer breeding areas is unquestionably a major factor in the rapid reduction of the eastern population (Meyers 2011, Springborn and Meyers 2005). Painted Buntings are most common in dense marine shrubs, particularly live oak, which occur along the coast, largely on the barrier and sea islands from the Carolinas southward to Georgia and northern Florida (Meyers 2011, Dybas 2018). Many of these islands have seen rapid residential and commercial development over the last several decades, and this has greatly diminished the acreage of the Painted Bunting’s breeding habitat. In addition, many of the individuals in this eastern population winter in South Florida, which has seen a similar pattern of development and consequent habitat loss. Also, the reduction in riparian habitats near the southern US and Mexican coastlines, which are used during migration by the western population, have further contributed to the population decline (Lowther et al. 1999, Sykes and Holzman 2005). Given its extraordinary colors and beauty, the Painted Bunting has unfortunately been trapped in portions of its wintering grounds and sold as a...

Reasons for the Reduction in the Population of the Western Subspecies of the Bean Goose (Anser fabalis fabalis and Anser fabalis rossicus): What Do the Ringing Data Say?

Reasons for the Reduction in the Population of the Western Subspecies of the Bean Goose (Anser fabalis fabalis and Anser fabalis rossicus): What Do the Ringing Data Say?

Fecundity, Female Maturation, and Nesting Season of Western Chicken Turtles (Deirochelys reticularia miaria) in Texas

The reproductive lifespans of turtles are consistently long, but reproductive cycles are under environmental control and thus can vary within species, populations, and individuals over time and space. Knowledge of turtle species' reproductive traits and their associated variances over time and space are critical to understanding the dynamics of turtle populations, especially those requiring management or conservation. Deirochelys reticularia is a species being considered for protection by the US Fish and Wildlife Service and contains 3 subspecies with some differences in reproductive characteristics of nesting season, annual nesting frequency, and egg retention. We collected ultrasound and x-radiograph data in Texas to identify the maturation size, nesting season, annual nesting frequency, and clutch size of female D. r. miaria in Texas. We observed no reproductive activity in individuals from 101 to 146 mm in plastron length (PL) and detected either unshelled eggs, shelled eggs, or both in individuals from 150 to 197 mm PL. Maturation sizes were similar to those in other regions and for other subspecies. We observed shelled clutches or nesting events from April to July, confirming a spring–summer nesting season in Texas consistent with other D. r. miaria sites and supporting the paradigm that the western subspecies does not follow the autumn–winter nesting season of the other subspecies. We found no evidence that individuals retain shelled eggs while aestivating or overwintering. Individuals nested up to 3 times/yr in Texas. Individuals laid 7–11 eggs and the mean clutch size was 9.2 eggs, similar to other regions and other subspecies. Nesting phenology is regionally variable, so management plans and policies for the species will need to consider that variation and potentially recognize management differences among D. reticularia subspecies.

Erythrina stem borer moth in California - New taxonomic status and implications for control of this emerging pest.

During the last 10 years, the Erythrina stem borer moth, Terastia meticulosalis, emerged as a pest of cultivated coral trees (Erythrina spp.) in California. Erythrina trees are valued for their moderate drought resistance and beautiful flame-like flowers. They are beloved enough to be considered Los Angeles's official "City Tree." Thus, they are a valuable horticultural crop and are grown by many nurseries and occur throughout the landscape in coastal southern California. Coral trees have been heavily affected by T. meticulosalis recently. Using whole genome sequencing techniques, we analysed the origins of this and other infestations of Erythrina in coastal areas and found that they have likely originated from the repeated expansions of the native range of the species in Arizona, a process possibly driven by climatic factors and/or movement of plants by humans. We also found sufficient genetic differences between the western population of the moth and the rest of the New World populations to describe a new western subspecies, T. meticulosalis occidentalis Sourakov & Grishin ssp. n. (type locality USA: CA, San Diego Co., La Jolla). These findings are of economic importance for future attempts to control the moth's impact on activities surrounding the horticultural use of Erythrina spp. by the Californian landscape and nursery industries.

Molt Strategies by Age and Subspecies in the Willow Flycatcher

We clarify the molt strategies of the Willow Flycatcher (Empidonax traillii) by subspecies through the examination of 455 museum specimens. Most and typically all juvenile primary coverts are retained during the preformative molt in fall and winter, allowing yearlings to be distinguished from older birds from their first spring through their second fall. In addition to replacing the body feathers and some to (usually) all secondary coverts and tertials, the preformative molt can include no other remiges or rectrices (46% of specimens), all remiges and rectrices (33%), or some remiges in an “eccentric” sequence (21%). During the prealternate molt, replacement of upper wing coverts and tertials is much less extensive than in the preformative molt, varying from replacement of no feathers in 27% of specimens to replacing more than half of the median and greater coverts and all three tertials in other specimens. Both the preformative and the first prealternate molts are significantly more extensive in eastern E. t. traillii than in the three western subspecies (brewsteri, adastus, and extimus). The definitive prealternate molt is also significantly more extensive than the first prealternate molt in the western subspecies but not in traillii. These differences between traillii and the other subspecies may result from longer migration distances, hence more solar exposure on an annual basis, and different molt-strategy dynamics between eastern and western North American passerines, perhaps relating to preferences for moister habitats. Further investigation is needed on the timing of molts on the winter grounds and the extent of body-feather replacement during the prealternate molt.

Sexual dimorphism of the body size of a multicolored lizard in the south-eastern Lower Volga

The investigation in the population structure of the western subspecies of the multicolored lizard ( Eremias arguta deserti Gmelin, 1789) was carried out in semi-deserts of the Lower Volga region. The purpose of the study was to find out the features of the population morphometric data. The main research methods: measuring the length of the trunk and tail with an accuracy of up to a millimeter, statistical data processing using the Kolmogorov - Smirnov test in the STATISTICA 12 program. Statistical analysis showed the presence of sexual dimorphism in the population in terms of body parameters: the length of the tail of males is significantly greater than that of females. The calculation of the statistical significance of the differences between the average length of the trunk and the length of the tail confirmed that males and females have longer tails than the trunk. Yet sexually mature males and females do not differ significantly from each other in terms of body size. At the same time, females have a certain variability of morphometric data, which serves as one of the main indicators of intra-population variability.

Genetic, bioacoustic and morphological analyses reveal cryptic speciation in the warbling vireo complex (Vireo gilvus: Vireonidae: Passeriformes)

Abstract Cryptic species are closely related taxa that are difficult to separate morphologically, but are reproductively isolated. Here we examine the warbling vireo complex (Vireo gilvus), a widespread songbird speculated to be comprised of more than one cryptic species. We included three taxa within the complex: two of the western (Vireo gilvus swainsonii and Vireo gilvus brewsteri) subspecies and the single eastern (Vireo gilvus gilvus) subspecies. We used mtDNA and microsatellite loci to assess the congruence of genetic data to the current subspecies boundaries. We then incorporated bioacoustic, morphometric and ecological niche modelling analyses to further examine differences. We found two genetic groups with mtDNA analysis, splitting eastern and western warbling vireos. Microsatellite analyses revealed four genetic groups: an eastern group, a Black Hills group and two western groups that do not agree with current western subspecies boundaries based on phenotypic data. Our results suggest that eastern and western warbling vireos have been reproductively isolated for a long period of time and therefore may be best treated as separate species. However, more research into areas of contact to examine the presence of hybridization is advised before making a taxonomic revision. Differences between the two western genetic groups appear less clear, requiring additional research.

Comment (Case 3709) – Additional comments on the proposed conservation of names for western North American Hesperia comma-group subspecies through designation of neotypes

Comment (Case 3709) – Additional comments on the proposed conservation of names for western North American Hesperia comma-group subspecies through designation of neotypes

Intercommunity interactions and killings in central chimpanzees (Pan troglodytes troglodytes) from Loango National Park, Gabon

Intercommunity competition in chimpanzees (Pan troglodytes) has been widely studied in eastern (P. t. schweinfurthii) and western (P. t. verus) communities. Both subspecies show hostility towards neighboring communities but differ in rates of lethal attacks and female involvement. However, relatively little is known about the territorial behavior of the two other subspecies, central (P. t. troglodytes) and Nigeria-Cameroon chimpanzees (P. t. ellioti). Here, we present the first insights into intercommunity interactions of individuals of a community of central chimpanzees living in the Loango National Park in Gabon. The presence of individuals of neighboring communities in the Rekambo home range was assessed using 27 camera traps. Information was compiled on intergroup interactions recorded before (2005–2016) and after (January 2017–June 2019) the habituation of the community. Individuals from neighboring communities entered the core area, where nine out of 16 recorded intercommunity encounters occurred. Males were the main participants in territorial patrols and intercommunity aggressions. Females were part of all six territorial patrols recorded and dependent offspring participated in five patrols. Females were involved in intercommunity aggression in five out of twelve recorded encounters in which there was visual contact between communities. While the intercommunity encounter rate was lower than that reported across most other long-term chimpanzee sites, the annual intercommunity killing rate was among the highest. These results suggest that the frequency of lethal attacks at Loango is comparable to that reported for the eastern subspecies. In contrast, female involvement in intercommunity interactions mirrors that of the western subspecies.

Genetic divergence, admixture and subspecific boundaries in a peripheral population of the great tit, Parus major (Aves: Paridae)

Abstract Secondary contact zones have been formed between several pairs of avian species and subspecies in northern and north-eastern Iran during the post-Pleistocene and Holocene periods. Three subspecies groups out of the four in the great tit (Parus major), major, bokharensis and cinereus, are believed to have come into local or regional secondary contact in north-eastern Iran. Parus major intermedius is also known from this region and has long been suggested to have a hybrid origin from hybridization between the yellow western (major) subspecies group and the grey-coloured eastern (bokharensis or cinereus) subspecies group based on its intermediate plumage coloration. Here, we investigated the evidence of intergradation between subspecies groups and the evolutionary origin of P. m. intermedius using mitochondrial DNA sequences and microsatellites, and approximate Bayesian computation to test competing scenarios for the demographic history of the populations. Our analyses indicate a divergence origin for intermedius that resulted from expansion of the major subspecies group. Low mitochondrial diversity and high genetic differentiation in comparison with central populations suggest that intermedius is a peripheral population. Microsatellite data show no signs of nuclear admixture between the bokharensis and major subspecies groups. However, one phenotypically intermedius specimen had bokharensis mtDNA and major nuclear DNA in the assumed hybrid zone (Lotf Abad), supporting past introgression.

Genetic origins and diversity of bushpigs from Madagascar (Potamochoerus larvatus, family Suidae)

The island of Madagascar, situated off the southeast coast of Africa, shows the first evidence of human presence ~ 10,000 years ago; however, other archaeological data indicates a settlement of the modern peoples of the island distinctly more recent, perhaps > 1500 years ago. Bushpigs of the genus Potamochoerus (family Suidae), are today widely distributed in Madagascar and presumed to have been introduced from Africa at some stage by human immigrants to the island. However, disparities about their origins in Madagascar have been presented in the literature, including the possibility of endemic subspecies, and few empirical data are available. Furthermore, the separation of bushpigs in Madagascar from their mainland relatives may have favoured the evolution of a different repertoire of immune genes first due to a founder effect and then as a response to distinct pathogens compared to their ancestors. Molecular analysis confirmed the species status of the bushpig in Madagascar as P. larvatus, likely introduced from the central region of southern Africa, with no genetic evidence for the recognition of eastern and western subspecies as suggested from previous cranial morphology examination. Investigation of the immunologically important SLA-DQB1 peptide-binding region showed a different immune repertoire of bushpigs in Madagascar compared to those on the African mainland, with seventeen exon-2 haplotypes unique to bushpigs in Madagascar (2/28 haplotypes shared). This suggests that the MHC diversity of the Madagascar populations may have enabled Malagasy bushpigs to adapt to new environments.

The snag’s the limit: Habitat selection modeling for the western purple martin in a managed forest landscape

The western purple martin (Progne subis arboricola), an avian insectivore, is a species of conservation concern throughout the Pacific Northwest. Compared to the well-studied eastern subspecies (Progne subis subis), little is known of the life history and biology of the western subspecies. Availability of breeding habitat is believed to be a major limiting factor for western purple martins in forested habitat, but fundamental information on their current distribution and selection of nesting habitat is deficient. To fill this gap, we compared habitat characteristics at three spatial scales (snag-level, stand-level [48.6 ha], landscape-level [314 ha]) surrounding nest snags occupied by purple martins in western Oregon to unoccupied sites. We found habitat for nesting purple martins was defined by the presence of moderately decayed snags with nest cavities, located well away from closed-canopy forest in sufficiently large (>15 ha) open areas. Our modeling efforts suggested suitable habitat was rare within the study region because: 1) snags were scarce on private industrial forest lands and 2) large disturbed patches were uncommon on federal lands. We conclude that a disturbance regime characterized by infrequent but major stand-replacing events, such as fire or timber harvest, is likely the key to maintaining breeding habitat for purple martins in upland forests in western Oregon.

Additional Hybridization Studies of Genomic Compatibility and Phenotypic Expression in the Genus Speyeria (Nymphalidae: Argynnini)

The genetic compatibility of the most divergent species within the genus Speyeria was tested in 25 different hybrid crosses and back-crosses. In addition, the inheritance and expression of various phenotypic characters of wing pattern and coloration were studied including examples of extreme sexual dimorphism in certain species. These characters are important for the taxonomic diagnosis and identification of the various Speyeria taxa. Most of these characters or traits appear to have a complex polygenic inheritance with more continuous ranges of variation that have often become fixated at one end of the continuum for many taxa. However, other characters show a simpler Mendelian inheritance of dominant or recessive expressions. Some color pattern traits appear to be unique for one or two species, but most characters appear to be widely shared among many different Speyeria taxa. The results of these hybrid crosses suggest that extensive interspecies gene flow through natural hybridization may have been important in shaping the past evolutionary history of this genus. Also, the extensive clinal intergradation between highly divergent eastern and western subspecies of S. atlantis is documented in northwestern Minnesota.