Palearctic Populations Research Articles

New insights on the chromosomal inversion thermal adaptation in insects: American populations of Drosophila subobscura

AbstractDrosophila subobscura is an excellent model species for testing genetic variation in thermal adaptation due to its rich inversion chromosomal polymorphism. In Palearctic populations, the inversions of this species can be classified as “cold”, “warm” or “nonthermal” adapted. Based on this classification the Chromosomal Thermal Index (CTI) was developed, which allows measuring the thermal adaptation of populations and monitoring changes over time. Here, we aim to use this index in American colonizing populations of D. subobscura for the first time to obtain new information on the species thermal adaptation. Thus, thermal adapted inversions (“cold” and “warm”) were defined for the American continent and CTI was computed in South American (1981 and 1999 samples) and North American (1985 and 2004 samples) populations of D. subobscura. In general, both American populations showed an inverse relationship between CTI values and latitude, with CTI values decreasing when latitude increases. When comparing populations sampled in different years, an increase in CTI values was detected in four out of six temporal comparisons (only one was significant) of South America (1981 and 1999) and in six out of seven populations of North America (1985 and 2004). A global analysis using a one‐way repeated measures anova of CTI values in both American hemispheres showed a trend of increase for “warm” adapted inversions in Chile and North America, but this increase was only significant for the latter. Overall, these results are in agreement with global warming expectations, although natural selection acted differently in the colonized hemispheres.

Morphological Ontogeny, Ecology, and Biogeography of Fuscozetes fuscipes (Acari, Oribatida, Ceratozetidae).

The systematic status of Fuscozetes Sellnick, 1928, is not clear in the literature. Therefore, the morphological ontogeny of F. fuscipes (C.L. Koch, 1844), the type species of this genus, was investigated and compared with its congeners in this study, and a new diagnosis of Fuscozetes is given. The juveniles of F. fuscipes are light brown, with a brown prodorsum, sclerites, epimeres, and legs. In all juveniles, a humeral organ and a humeral macrosclerite are present. The gastronotum of the larva has 12 pairs of setae (h3 is present), whereas the nymphs have 15 pairs. In the larva, the gastronotal shield is weakly developed, and most gastronotal setae are short except for a slightly longer h2. Most of the gastronotal setae are inserted on the microsclerites except for h3, and several other macrosclerites and many microsclerites are present on the hysterosoma. In the nymphs, the gastronotal shield is well developed, with 10 pairs of setae (d-, l-, and h-series, and p1), and setae p2 and p3 are located on a large posteroventral macrosclerite. In all the instars, femora I and II are oval in cross-section, without a large ventral carina. Mitochondrial COI sequence data revealed a deep split between the Nearctic and Palearctic populations of F. fuscipes, and a less, but significant, divergence within each continent. These strong geographical barriers were contrasted with multiple cases of shared haplotypes over long distances in the Palearctic, indicating high migration rates in modern times.

Karyotypes and COI Gene Sequences of Chironomus annularius Sensu Lato (Diptera, Chironomidae) from Russia, Mongolia, and Armenia

The larvae of the genus Chironomus are a common object for hydrobiological studies, as well as a model object for cytogenetics. Morphologically, the species are very similar. One of these species or species complex is Chironomus “annularius”, which has a Holarctic distribution. It has chromosomal banding sequences characteristic of Nearctic and Palearctic populations. Using an integrated method that included morphology, cytogenetics, and molecular genetics, we analyzed populations from Russia, Mongolia, and Armenia. We found through cytogenetics and larval morphology that the populations have high similarity. Molecular genetic studies have shown significant differences between the populations. The genetic distances between the populations, in some cases, exceed the interspecific threshold of 3%, and are 6.5%. In the South Caucasian population (Lake Sevan), a chromosomal banding sequence, h’annD3, that was previously observed only in North America, was found for the first time. The larvae from Lake Sevan have large genetic distances from others, and are morphologically similar to the species Chironomus markosjani Shilova 1983, described from this lake without comparison with Ch. annularius nor an exact description of the karyotype. The sequences of the COI genes from Montenegro (Lake Skadar) and West Siberia (Novosibirsk) found in GenBank may belong to a new undescribed species, or a species not represented in the database. Thus, the analyzed data on Chironomus “annularius” support the presence of the complex of homosequential species under this name.

The taxonomic status of Palearctic and Nearctic populations of northern goshawk Accipiter gentilis (Aves, Accipitridae): New evidence from vocalisations

The taxonomic status of the North American and Eurasian populations of northern goshawk A. gentilis has been called into question by recent molecular studies, indicating the need for additional taxonomic study. Vocalisations have long played an important role in diagnosing potentially reproductively isolated groups of birds. The chattering-type call of A. gentilis plays a role in advertisement and pair-contact, making this a suitable basis for taxonomic study of vocalisations. The data set consisted of recordings of the calls of 75 individuals of the Eurasian gentilis-group of A. gentilis, 37 of the North American atricapillus-group of A. gentilis and, for comparison, seven of Henst’s goshawk A. henstii. The three groups showed non-overlapping variation in the duration of call-notes and also showed several other highly significant differences. Discriminant Function Analysis resulted in 100% correct classification of recordings into the three groups. It is here argued that the new bioacoustic data, in combination with previous evidence of morphological, mitochondrial DNA and genomic DNA differences between Eurasian and North American A. gentilis, suggests that two species are best recognised: northern goshawk A. gentilis and American goshawk A. atricapillus. A. gentilis / A. atricapillus add to a growing list of Holarctic temperate zone taxa that have recently been recognised as separate species based on a deep phylogeographic split between Eurasian and North American populations in combination with differences in other characters. This is the first quantitative taxonomic study of vocalisations in Accipitridae.

Mitogenome Phylogeny Including Data from Additional Subspecies Provides New Insights into the Historical Biogeography of the Eurasian lynx Lynx lynx.

Previous molecular studies of the wide-ranging Eurasian lynx Lynx lynx focused mainly on its northern Palearctic populations, with the consequence that the reconstruction of this species’ evolutionary history did not include genetic variation present in its southern Palearctic distribution. We sampled a previously not considered Asian subspecies (L. l. dinniki), added published data from another Asian subspecies (L. l. isabellinus), and reassessed the Eurasian lynx mtDNA phylogeny along with previously published data from northern Palearctic populations. Our mitogenome-based analyses revealed the existence of three major clades (A: Central Asia, B: SE Europe/SW Asia, C: Europe and Northern Asia) and at least five lineages, with diversification in Lynx lynx commencing at least 28kyr earlier than hitherto estimated. The subspecies L. l. isabellinus harbors the most basal matriline, consistent with the origin of Lynx lynx in this subspecies’ current range. L. l. dinniki harbors the second most basal matriline, which is related to, and may be the source of, the mtDNA diversity of the critically endangered Balkan lynx L. l. balcanicus. Our results suggest that the Anatolian peninsula was a glacial refugium for Eurasian lynx, with previously unconsidered implications for the colonization of Europe by this species.

Поширення та мінливість мишаків групи Sylvaemus microps & uralensis у Східній Європі: фрагментація та клини

The species names Sylvaemus microps and Sylvaemus uralensis are markers of the two key stages in the recognition of the taxonomic heterogeneity of Sylvaemus sylvaticus (s. str.), to which they have long been included. The first was described in 1952 from Central Europe, while the second 140 years earlier (1818) from the Southern Urals. Both taxa have undergone a complicated taxonomic history and are now considered conspecific. However, there are some gaps between them, in particular geographic ones. They are considered here as two groups of populations: a western (microps) and an eastern (uralensis). The taxonomic history of wood mice of the group Apodemus microps & Sylvaemus uralensis and the history of increase in knowledge on their distribution are considered. An analysis of geographic variability of key diagnostic characters of the species was carried out, which revealed a quite well-expressed morphological homogeneity. Within the Western Palearctic populations, there is a clear clinal variation from relatively large southern and eastern to small northern and western forms. Geographic range analysis shows the presence of several relatively isolated fragments of the range, including a clear gap between the western forms of the microps group (Central Europe, the Balkans, and the Western Carpathians region) and the eastern forms of the uralensis group (from the Dnipro region and Baltic states to the Urals, including the Caucasus and Asia Minor). Proposals to recognise the specific level of differentiation between the northern and southern forms seem far too hypothetical, as well as the idea to assign the Caucasian form (ciscaucasicus) to the Central European microps and the Crimean form (baessleri) to the Upper Volga mosquensis. In general, the available data indicate differences between the western and eastern forms of Sylvaemus uralensis. Detailed information on marginal records of the two groups of populations is given, including the easternmost (essentially north-eastern) findings of the microps group and the westernmost findings of the uralensis group. There is a significant geographic gap between these two forms covering the entire area of Volyn, Podillia, Western and Central Polissia, but narrowing to the south, towards the Black Sea. Connection between the two range fragments may exist in the south, but the available and verified data essentially show a gap across the interfluve between the Dnister and Tyligul rivers.

Large‐scale longitudinal climate gradient across the Palearctic region affects passerine feather moult extent

Large‐scale spatial gradients of environmental conditions shape organisms, populations and ecosystems. Even though environmental gradients are a key research theme in macro‐ecology and biogeography, the effects of large‐scale, east–west, environmental gradients are largely overlooked compared with north–south gradients. Our study focused on feather moult, an important and energy demanding process in birds. By comparing Western and Eastern Palearctic populations of 21 species, we found that juvenile passerines in the Western and Eastern Palearctic differ in the number of feathers moulted as part of their post‐juvenile moult. This difference is most likely the result of a large‐scale climatic gradient in cold season duration and consequent differences in the time available for moulting. Eastern populations were characterized by a limited extent of feather moult that was additionally affected by migration distance and body mass. The longer migration distance in the Eastern Palearctic caused a generally less extensive moult while high body mass was correlated with a low difference in moult extent between the Western and Eastern Palearctic regions. These results highlight the importance of linking annual cycle processes at the organismal level to the specific environmental conditions within the distribution range of each species.

The puzzling mitochondrial phylogeography of the black soldier fly (Hermetia illucens), the commercially most important insect protein species

BackgroundThe black soldier fly (Diptera: Stratiomyidae, Hermetia illucens) is renowned for its bioconversion ability of organic matter, and is the worldwide most widely used source of insect protein. Despite varying extensively in morphology, it is widely assumed that all black soldier flies belong to the same species, Hermetia illucens. We here screened about 600 field-collected and cultured flies from 39 countries and six biogeographic regions to test this assumption based on data for three genes (mitochondrial COI, nuclear ITS2 & 28S rDNA) and in order to gain insights into the phylogeography of the species.ResultsOur study reveals a surprisingly high level of intraspecific genetic diversity for the mitochondrial barcoding gene COI (divergences up to 4.9%). This level of variability is often associated with the presence of multiple species, but tested nuclear markers (ITS2 and 28S rDNA) were invariant and fly strain hybridization experiments under laboratory conditions revealed reproductive compatibility. COI haplotype diversity is not only very high in all biogeographic regions (56 distinct haplotypes in total), but also in breeding facilities and research centers from six continents (10 haplotypes: divergences up to 4.3%). The high genetic diversity in fly-breeding facilities is mostly likely due to many independent acquisitions of cultures via sharing and/or establishing new colonies from field-collected flies. However, explaining some of the observed diversity in several biogeographic regions is difficult given that the origin of the species is considered to be New World (32 distinct haplotypes) and one would expect severely reduced genetic diversity in the putatively non-native populations in the remaining biogeographic regions. However, distinct, private haplotypes are known from the Australasian (N = 1), Oriental (N = 4), and the Eastern Palearctic (N = 4) populations. We reviewed museum specimen records and conclude that the evidence for introductions is strong for the Western Palearctic and Afrotropical regions which lack distinct, private haplotypes.ConclusionsBased on the results of this paper, we urge the black soldier fly community to apply molecular characterization (genotyping) of the fly strains used in artificial fly-breeding and share these data in research publications as well as when sharing cultures. In addition, fast-evolving nuclear markers should be used to reconstruct the recent invasion history of the species.

Towards a better understanding of echiniscid intraspecific variability: A redescription of Nebularmis reticulatus (Murray, 1905) (Heterotardigrada: Echiniscoidea)

The interplay between tardigrade genetic and ontogenetic diversity, resulting in morphological variation within a species, remains a poorly studied field. In this work, by combining qualitative (light and scanning electron microscopy), quantitative (morphometrics) and genetic analyses (DNA sequencing of five molecular markers) on five Palearctic populations of Nebularmis reticulatus (Murray, 1905) and a Tanzanian population of Nebularmis cirinoi (Binda and Pilato, 1993), all rare members of the Echiniscidae, we discuss intra- and interspecific variability in limno-terrestrial Heterotardigrada. We show that in these parthenogenetic (thelytokous) echiniscid species: (a) morphology strongly varies among life stages and between populations; (b) between populations of a single species there are statistically significant differences in the lengths of sclerotised structures commonly used in species delineation; (c) populations are dominated by one or two haplotypes of quickly evolving DNA fragments (ITS-1, ITS-2, COI), which suggests that such populations are characterised by low genetic diversity. Additionally, here we establish Loch Ness (Scotland) as the neotype locality for N. reticulatus. Finally, challenges of the taxonomy of the genus Nebularmis Gąsiorek & Michalczyk, 2019 are highlighted.

Out of Transcaucasia: Origin of Western and Central Palearctic populations of Microthlaspi perfoliatum

Quaternary climatic oscillations had strong effects on Palearctic biodiversity. Although Transcaucasia is hypothesised to be a centre of diversity for many taxa, relatively few studies have investigated its potential role as such, or as a Pleistocene refugium. Using AFLP and sequence data (ITS, matK, trnL-F) from samples collected across the entire range of Microthlaspi perfoliatum, from the Iberian peninsula to Kazakhstan, and including the Mediterranean Basin and Central Europe, in this study it is examined how the interplay of Pleistocene climatic oscillations and historical demography may have shaped the current genetic structure of the species. The results of this study provide evidence that M. perfoliatum survived Pleistocene glaciation in five major refugia, Iberia, southwestern France, Italy, the Balkans and Anatolia/Transcaucasia and a sixth, unknown refugium in the disjunct distribution area in Central Asia. Our analyses support an ancient colonisation of M. perfoliatum towards the western and central Palearctic, perhaps, during the early Pleistocene or late Pliocene, likely starting from Transcaucasia. However, postglacial recolonisation of western and Central Europe has taken place from two distinct refugia, namely southwestern France/northern Italy, and Anatolia/Southern Balkans, respectively. The Iberian populations apparently did not contribute to postglacial recolonisation of Europe, perhaps because the Pyrenees acted as a significant barrier to dispersal. It is also conceivable that a rapidly expanding population from southwestern France and the southeastern part of the range effectively blocked the establishment of latecomers. The present study thus reveals a complex pattern of colonisation of Europe from Transcaucasia, with an interplay of climate and physical geography as main factors shaping the present-day genetic structure of M. perfoliatum.

Prevalence and genetic diversity of Wolbachia endosymbiont and mtDNA in Palearctic populations of Drosophila melanogaster

BackgroundMaternally inherited Wolbachia symbionts infect D. melanogaster populations worldwide. Infection rates vary greatly. Genetic diversity of Wolbachia in D. melanogaster can be subdivided into several closely related genotypes coinherited with certain mtDNA lineages. mtDNA haplotypes have the following global distribution pattern: mtDNA clade I is mostly found in North America, II and IV in Africa, III in Europe and Africa, V in Eurasia, VI is global but very rare, and VIII is found in Asia. The wMel Wolbachia genotype is predominant in D. melanogaster populations. However, according to the hypothesis of global Wolbachia replacement, the wMelCS genotype was predominant before the XX century when it was replaced by the wMel genotype. Here we analyse over 1500 fly isolates from the Palearctic region to evaluate the prevalence, genetic diversity and distribution pattrern of the Wolbachia symbiont, occurrence of mtDNA variants, and finally to discuss the Wolbachia genotype global replacement hypothesis.ResultsAll studied Palearctic populations of D. melanogaster were infected with Wolbachia at a rate of 33–100%. We did not observe any significant correlation between infection rate and longitude or latitude. Five previously reported Wolbachia genotypes were found in Palearctic populations with a predominance of the wMel variant. The mtDNA haplotypes of the I_II_III clade and V clade were prevalent in Palearctic populations. To test the recent Wolbachia genotype replacement hypothesis, we examined three genomic regions of CS-like genotypes. Low genetic diversity was observed, only two haplotypes of the CS genotypes with a ‘CCG’ variant predominance were found.ConclusionThe results of our survey of Wolbachia infection prevalence and genotype diversity in Palearctic D. melanogaster populations confirm previous studies. Wolbachia is ubiquitous in the Palearctic region. The wMel genotype is dominant with local occurrence of rare genotypes. Together with variants of the V mtDNA clade, the variants of the ‘III+’ clade are dominant in both infected and uninfected flies of Palearctic populations. Based on our data on Wolbachia and mtDNA in different years in some Palearctic localities, we can conclude that flies that survive the winter make the predominant symbiont contribution to the subsequent generation. A comprehensive overview of mtDNA and Wolbachia infection of D. melanogaster populations worldwide does not support the recent global Wolbachia genotype replacement hypothesis. However, we cannot exclude wMelCS genotype rate fluctuations in the past.

Migratory routes of red‐necked phalaropes Phalaropus lobatus breeding in southern Chukotka revealed by geolocators

The migration routes of red‐necked phalaropes breeding around the Bering Sea are poorly known, despite the fact that the Bering Sea could mark the boundary between the East Palearctic populations that winter in the Pacific Ocean around the East Indies and the West Nearctic populations that winter in the Pacific Ocean off the coast of South America. Geolocator data retrieved from two male phalaropes tagged in southern Chukotka, Far Eastern Russia, confirm that birds breeding in this region belong to the East Palearctic population and winter in the East Indies, suggesting that the division line with the West Nearctic population is farther to the east. The routes taken by the two phalaropes were almost entirely pelagic, totaling around 18 000–20 000 km round‐trip, with the birds continuously on the move during migration, rather than resident in any particular stopover site, contrary to most other migratory shorebirds.

Grass greenness flush can influence breeding phenology and fertility in equatorial thoroughbred mares in the absence of photoperiod variation.

Reproductive phenology is an important trait subjected to natural selection. Current horses in America belong to the Palearctic original populations after being introduced by European colonizers. Photoperiod variation is the main environmental factor for the adjustment of reproductive timing in horses, but is absent in equatorial areas. Here we hypothesize that seasonality of green-grass availability may influence breeding phenology in equatorial regions. We used data of 929 services to mares from 2006 to 2011 in a thoroughbred equine exploitation in Ecuador that experienced strong grass seasonality. Actual births could not be used to infer natural phenology because they were influenced by management decisions. Instead, we used variations in the probability of pregnancy after a service as a measure of the natural tendency of mares to show breeding phenology. We found that although managers tended to schedule pregnancies in two periods within the year, mares were more prone to become pregnant after the increase in grass greenness that takes place at the beginning of the year (February). Our finding has potential applications to improve the success of services and the welfare of animals, by providing green-grass stimuli in the appropriate season.

A new subspecies of Short-toed Snake-eagle from Wallacea determined from morphological and DNA comparison.

The taxonomic status of the geographically isolated population of Short-toed Snake-eagle Circaetus gallicus on the Lesser Sundas (=Nusa Tenggara) has been controversial. In the past they have been regarded as either a migrant population or a recently arrived resident population. Here we obtained DNA sequences from the mitochondrial cytochrome-b gene and combined genetic data with assessments of published and novel morphological data to clarify the taxonomic status of the Lesser Sundas population of C. gallicus. The cytochrome-b distance between the Lesser Sundas and Palearctic populations of C. gallicus is consistent with subspecific differentiation, indicating a possible divergence during one of the most recent Pleistocene glaciations. Although some of the morphological distinctions show overlap, the new subspecies can generally be diagnosed from nominate C. gallicus gallicus by being smaller and paler, and exhibiting less spotting and barring. Unlike nominate populations from mainland Eurasia, the new subspecies seems to lack pronounced sexual dimorphism. We here describe this new subspecies to science and discuss its biology and conservation status.

Morphological differences between Nearctic and eastern Palearctic Gray-headed Chickadees (Poecile cinctus)

ABSTRACT The geographic distribution of the non-migratory Gray-headed Chickadee (Poecile cinctus) straddles the continents of North America and Eurasia. Morphological variation in this species has been poorly studied, particularly regarding differences between Nearctic and adjacent Palearctic populations (subspecies lathami and cinctus, respectively). To evaluate geographic patterns of morphological variation between lathami and cinctus, we measured 24 variables related to coloration and structure on 24 museum specimens. We found statistically significant average differences between specimens of lathami and cinctus in three plumage areas and three measures of bill size. Genetic analysis is needed to further quantify divergence in lathami.

Geographic variation in coal tit song across continents and reduced species recognition between Central European and Mediterranean populations

Intraspecific variation of passerine song may influence mate choice and consequently provides a potential mechanism for premating reproductive isolation in birds. Notable geographic variation of songs is particularly common in widespread bird species, such as the coal tit Periparus ater (Aves, Passeriformes, Paridae) having a large trans-Palearctic distribution range including allopatric populations. In this study, measurement and analysis of 16 song parameters from different Western Palearctic populations showed a relatively uniform song in all continental European and the island populations of Corsica and Sardinia. Song variation among and within these populations seems so variable that there is a broad geographical overlap of acoustic parameters between populations. However, songs from northwest African and Cypriot populations had lowest minimum frequencies and were thus significantly different from continental European, Corsican and Sardinian populations. To test for intraspecific species recognition and potential acoustic isolation of different Palearctic populations, we carried out field playback experiments on Central European coal tit males with songs from populations of the Eurasian (Germany, Latvia, Russian Far East, Japan) and the Mediterranean region (northwest Africa, Cyprus, Corsica, Sardinia). Eurasian song types elicited similar strong territorial reactions in Central European coal tits as local control songs. In contrast, none of the Mediterranean songs evoked any notable reaction. Thus, there is geographic variation in coal tit song across continents that coincides with reduced species recognition between Central European and Mediterranean populations.

Changing Names with Changed Address: Integrated Taxonomy and Species Delimitation in the Holarctic Colymbetes paykulli Group (Coleoptera: Dytiscidae).

Species delimitation of geographically isolated forms is a long-standing problem in less studied insect groups. Often taxonomic decisions are based directly on morphologic variation, and lack a discussion regarding sample size and the efficiency of migration barriers or dispersal/migration capacity of the studied species. These problems are here exemplified in a water beetle complex from the Bering Sea region that separates North America from Eurasia. Only a few sampled specimens occur from this particular area and they are mostly found in museum and private collections. Here we utilize the theory of integrated taxonomy to discuss the speciation of the Holarctic Colymbetes paykulli water beetle complex, which historically has included up to five species of which today only two are recognized. Three delimitation methods are used; landmark based morphometry of body shape, variation in reticulation patterns of the pronotum exo-skeleton and sequence variation of the partial mitochondrial gene Cyt b. Our conclusion is that the Palearctic and Nearctic populations of C. paykulli are given the status of separate species, based on the fact that all methods showed significant separation between populations. As a consequence the name of the Palearctic species is C. paykulli Erichson and the Nearctic species should be known as C. longulus LeConte. There is no clear support for delineation between Palearctic and Nearctic populations of C. dahuricus based on mtDNA. However, significant difference in size and reticulation patterns from the two regions is shown. The combined conclusion is that the C. dahuricus complex needs a more thorough investigation to fully disentangle its taxonomic status. Therefore it is here still regarded as a Holarctic species. This study highlights the importance to study several diagnosable characters that has the potential to discriminate evolutionary lineage during speciation.

Species of the subgenus Chaetolabis, townes 1945 of the genus Chironomus, Meigen 1803 (Diptera: Chironomidae), from a cytogenetic perspective.

The polytene chromosomes of three North American species in the subgenus Chaetolabis of the genus Chironomus are described and compared to the published karyotypes of two Palearctic species. Chironomus (Chaetolabis) atroviridis has four polytene chromosomes, like the Palearctic C. globulus, while C. ochreatus and the North American populations of C. bitumineus each have three chromosomes due to tandem fusion of arm G to arm E, as in the Palearctic populations of C. bitumineus. The results support the existence of distinct species, particularly clarifying that the names C. atroviridis, C. bitumineus and C. ochreatus cannot be synonyms, as was suggested by some previous workers. The question of whether Lobochironomus "sp. Ya6" might be conspecific with C. macani is also discussed.

Vanishing Chromosomal Inversion Clines inDrosophila subobscurafrom Chile: Is Behavioral Thermoregulation to Blame?

Chromosomal inversion clines paralleling the long-standing ones in native Palearctic populations of Drosophila subobscura evolved swiftly after this species invaded the Americas in the late 1970s and early 1980s. However, the new clines did not consistently continue to converge on the Old World baseline. Our recent survey of Chilean populations of D. subobscura shows that inversion clines have faded or even changed sign with latitude. Here, we investigate the hypothesis that this fading of inversion clines might be due to the Bogert effect, namely, that flies' thermoregulatory behavior has eventually compensated for environmental variation in temperature, thus buffering selection on thermal-related traits. We show that latitudinal divergence in thermal preference (Tp) has evolved in Chile for females, with higher-latitude flies having a lower mean Tp. Plastic responses in Tp also lessen latitudinal thermal variation because flies developed at colder temperatures prefer warmer microclimates. Our results are consistent with the idea that active behavioral thermoregulation might buffer environmental variation and reduce the potential effect of thermal selection on other traits as chromosomal arrangements.

Genetic diversity and differentiation between Palearctic and Nearctic populations ofAedimorphus (=Aedes) vexans(Meigen, 1830) (Diptera, Culicidae)

Genetic diversity was studied at allozyme loci in two Palearctic and one Nearctic population of Aedimorphus (=Aedes) vexans, a species of public health and veterinary importance. The population from Serbia was the most polymorphic (P= 35%) with the highest observed heterozygosity (H(o) = 0.027). The lowest observed heterozygosity (H(o) = 0.010) was obtained for the Nearctic population. All analyses based on individual (STRUCTURE analysis) and population level (pairwise F(ST), Nm values, AMOVA, Nei's D value) revealed significant structuring between Nearctic and Palearctic populations, indicating a lack of gene flow and thus, the presence of independent gene pools. Taxon-specific alleles at the diagnostic Ao, Hk-2, Hk-3, Hk-4, Idh-1, and Idh-2 loci were used for identification and separation of Nearctic and Palearctic populations. Population genetics study provided valuable information on the correct distinction of Am. vexans populations and their adaptive potential that could find a future use in the studies of vector competence and development of vector-control strategies.