Variability of the hard dorsal idiosomal tegument pattern and other phenotypic characters as a manifestation of microevolution in Dermacentor marginatus (Acari: Ixodidae)

The pattern of male conscutum and female scutum in Dermacentor marginatus has been examined in 6 points of the East-European and Asian parts of its range (Fig. 1). A high rate of modification variability of the pattern has been recovered in each geographical sample. It is shown that populations differ reliably from each other by the length of the dark patches on the marginal flank of the conscutum (nkappabeta, npkappabeta, 3kappabeta); some samples also differ by the number of these patches, complexes of other patches of the scutum and conscutum, and as well (visually) by the color density of light fields and contrast between them and the dark background on the conscutum and scutum (Table 1, 2). Besides, the samples differ reliably at each stage by the complexes of morphometric characters (Table 3, 4). The sample from the Peter the First Ridge is most deviate from others by the color contrast and complex of patches both in males and females. However, by the patches of marginal flank and morphometric characters of both sexes and perimaginal stages this sample differ less from others. The sample from the Stavropol plateau having most variable pattern (Fig. 3, 1-9, 4, 1-3) is characterized by the greater number of statistically reliable differences by the patches (nkappabeta, npkappabeta, 3kappabeta) and morphometric characters of all stages of the ontogenesis from all other samples. Other geographical samples have intermedial position in regard to degree of differences from each other. The samples examined are considered as morphotypes; degree of differences between morphotypes is unequal. The phenotypic differences have mosaic dispersion among ontogenetic stages and do not show a coherent direction in comparing the morphotypes. Differential characters of the morphotypes and related tick species belong to different structures or their different parameters. Possible ways of morphotype's origin and geochronological characteristics of morphotypes are discussed.     

Sexual dimorphism of the nymphal phase of ixodid tick species in the genus Dermacentor

In four studied Dermacentor species at preimaginal phases sexual dimorphism hardly reveals itself in body size and mass of individuals. The formation of sexual distinctions at the nymphal phase concerns different characters as in different species so in populations of one species. In D. niveus male and female nymphs differ in the length of II-III palpal joints and width of gnathosoma, in D. ushakovae in the length of scutum and its proportions, in the width of gnathosoma and hypostome and in the diameter of peritreme. The sex of D. silvarum nymphs can be identified by the width of gnathosoma, length of hypostome and diameter of peritreme. Female and male nymphs of D. marginatus from the Stavropol Territory and Armenia differ in the scutum proportions and populations from the western Pamirs in the length of scutum and gnathosoma.     

Variability of mitochondrial cytochrome oxidase first subunit gene (<Emphasis Type="Italic">COI</Emphasis>) fragments in several tick species of the marginatus group (Ixodidae,Amblyomminae, <Emphasis Type="Italic">Dermacentor</Emphasis>)

This paper analyses variability of the nucleotide sequence of the mitochondrial cytochrome oxidase first subunit gene fragments in four tick species of the marginatus group—Dermacentor marginatus, D. silvarum, D. niveus, and D. nuttalli. It is noted that, with the exception of D. niveus, the clustering of mitotypes in the marginatus group does not show a clear correspondence of the species identity of ticks, which had preliminarily been established based on morphological characters.     

The correlation variability of the morphometric traits in 4 species of ixodid tick species (Ixodidae)]

Correlation analysis of 10 characters was run in three species of Dermacentor, D. nuttalli, D. ushakovae, D. niveus, and in Ixodes persulcatus, separately for each phase and sex. Correlation coefficients are very low in larvae of all species. In male nymphs correlation coefficients are on the same level in all species while the correlation coefficient level in female nymphs reflects the degree of independence of the development of characters. This defines the degree of manifestation of sexual dimorphism at the nymphal phase: the more rigid the connections between the characters the less number of characters shows sexual differences. At the phase of imago the lowest correlation coefficients are in I. persulcatus. This species displays most distinct differences in the morphology of females and males. On the basis of comparison of correlation and variability coefficients the functional role of the characters is discussed.     

蜱类染色体的分带研究和扫描电镜观察

在蜱螨亚纲（Ａｃａｒｉ）中,首先开展染色体分带研究及组型分析,发现了３种蜱的内多倍体,Ｃ分带证明,森林革蜱,草原革蜱,微小牛蜱的全套染色体国端丝粒,用扫描电镜观察了日本血蜱,微小牛蜱染色体的亚微结构,发现日本血蜱的染色体呈凹凸相同弹簧样螺旋结构,螺旋凹陷处相当于光镜下Ｇ带深带,螺旋隆起部相当于Ｇ带浅带,凹凸程度似乎不加入人类染色体的明显,还报告了草原革蜱,银盾革蜱,缺角血蜱及雌性森林革蜱,雌性日本     

A new morph of Telmatochromis temporalis (Cichlidae; Cichliformes) from Lake Tanganyika

Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. Two morphs of this species, normal and dwarf, form a good model for the study of ecological speciation through divergent natural selection on body size. This study reports a third morph of this species, slender morph, which was collected from deep waters off Kasenga, Zambia, whereas the normal morph inhabits shallow waters of the same locality. This study examined morphological characters and mitochondrial DNA sequences in 18 populations of the three T. temporalis morphs and two closely related species. The slender morph was morphologically similar to the normal and dwarf morphs of the same species, but clearly differed from closely related species. Genetic analyses showed that the slender morph was closest to but significantly different from the parapatric normal morph, suggesting reproductive isolation between them. Due to the lack of colour differences between morphs and of obvious geographical barriers between habitats, reproductive isolation between these morphs may be attributed to ecological factors, rather than sexual or geographical segregation. Further studies examining the evolution of the slender morph may deepen our knowledge of initial stages of speciation, like in the dwarf morph.

     

The geographical pattern of speciation and floral diversification in the neotropics: the tribe sinningieae (gesneriaceae) as a case study

The geographical pattern of speciation and the relationship between floral variation and species ranges were investigated in the tribe Sinningieae (Gesneriaceae), which is found mainly in the Atlantic forests of Brazil. Geographical distribution data recorded on a grid system of 0.5 x 0.5 degree intervals and a near-complete species-level phylogenetic tree of Sinningieae inferred from a simultaneous analysis of seven DNA regions were used to address the role of geographical isolation in speciation. Geographical range overlaps between sister lineages were measured across all nodes in the phylogenetic tree and analyzed in relation to relative ages estimated from branch lengths. Although there are several cases of species sympatry in Sinningieae, patterns of sympatry between sister taxa support the predominance of allopatric speciation. The pattern of sympatry between sister taxa is consistent with range shifts following allopatric speciation, except in one clade, in which the overlapping distribution of recent sister species indicates speciation within a restricted geographical area and involving changes in pollinators and habitats. The relationship between floral divergence and regional sympatry was also examined by analyzing floral contrasts, phenological overlap, and the degree of sympatry between sister clades. Morphological contrast between flowers is not increased in sympatry and phenological divergence is more apparent between allopatric clades than between sympatric clades. Therefore, our results failed to indicate a tendency for sympatric taxa to minimize morphological and phenological overlap (geographic exclusion and/or character displacement hypotheses). Instead, they point toward adaptation in phenology to local conditions and buildup of sympatries at random with respect to flower morphology. Additional studies at a lower geographical scale are needed to identify truely coexisting species and the components of their reproductive isolation.     

Comparative analysis of genetic structure of 2 species of marine fish Dicentrarchus labrax and Dicentrarchus punctatus

We present here the genetic structure existing among five samples of the spotted sea bass Dicentrarchus punctatus, and we compare it to what prevails in the common sea bass D. labrax, a congeneric species sampled on almost the same geographical range. A genetic distance tree inferred from the polymorphism at six microsatellite loci shows a distinct pattern for the two species. D. labrax samples appears to be genetically more homogeneous with a global Fst of 3% as compared to the 10% observed at D. punctatus, indicating a lesser level of gene flow in the latter species. While appearing more differentiated, D. punctatus presents no clear geographical organisation of its genetic variability in opposition to D. labrax samples. This allows us to propose this pair of closely relative species as a good candidate for the study by comparative analysis of the biological and/or historical factors affecting genetic differentiation in marine environment.     

Molecular-genetic diversification of lizard complex D. raddei (Sauria: Lacertidae): early stages of speciation

A number of populations of genus Darevskia lizards were studied using inter-SINE-PCR (IS-PCR). The number and size of PCR-amplified spacers of genomic DNA flanked by SINE-type repeats were compared in 17 populations of the D. raddei species complex along with several other species from the same genus. Nei and Li's (D(NL)) genetic distances between populations were unequivocal. Individual differences among D. r. nairensis sample specimens and between the samples fall into a range of less than 0.1. Individual variability intra each of the D. r. raddei samples--into a range of 0.1-0.2, but the inter samples differences in this subspecies depends on its geographic localizations. Thus the differences between 10 samples from Armenia and Karabach fall into a range of 0.2-0.3, but between all these and two samples from Talysh (Azerbajdzhan)--of 0.3-0.4. At the same time, the variability between both known subspecies (D. r. raddei and D. r. nairensis) reaches the same values. The differences between "good" species D. raddei and D. rudis were about 0.60-0.7. It may be supposed that D. r. raddei is currently undergoing the speciation process. The population of lizards from Turkey which is considered to be close to D. raddei by some researchers and to D. rudis by others is, according to our molecular data, more closely related to the latter species. The difference of homogeneity between other populations was revealed by comparison of the DNL values. Possible phylogeographic pathways of Darevskia species distribution based on the molecular data were proposed.     

Geographical versus ecological isolation of closely related black flies (Diptera: Simuliidae) inferred from phylogeny, geography, and ecology

To investigate patterns of geographical and ecological separation among morphologically similar, closely related species of black flies, we integrated ecological, geographical, and phylogenetic information, based on multiple gene sequences, for 12 species in the subgenus Gomphostilbia in Thailand. Molecular characters supported the monophyly of the Simulium ceylonicum species group, but not of the Simulium batoense species group, suggesting that revisionary work is needed for the latter. Both ecological and geographical isolation of similar taxa were revealed. Stream velocity and altitude were among the principal ecological factors differing between closely related species. Most closely related species in the subgenus Gomphostilbia overlap geographically, suggesting the possibility of sympatric speciation driven by ecological divergence. Geographical isolation via dispersal also might have contributed to species divergence, while Pleistocene climate changes possibly influenced population genetic structure, demographic history, and speciation of some members of the subgenus.     

Heterogeneity, speciation/extinction history and climate: explaining regional plant diversity patterns in the Cape Floristic Region

This paper investigates the role of heterogeneity and speciation/extinction history in explaining variation in regional scale (c. 0.1–3000 km²) plant diversity in the Cape Floristic Region of south‐western Africa, a species‐ and endemic‐rich biogeographical region. We used species‐area analysis and analysis of covariance to investigate geographical (east vs. west) and topographic (lowland vs. montane) patterns of diversity. We used community diversity as a surrogate for biological heterogeneity, and the diversity of naturally rare species in quarter degree squares as an indicator of differences in speciation/extinction histories across the study region. We then used standard statistical methods to analyse geographical and topographic patterns of these two measures. There was a clear geographical diversity pattern (richer in the west), while a topographic pattern (richer in mountains) was evident only in the west. The geographical boundary coincided with a transition from the reliable winter‐rainfall zone (west) to the less reliable non‐seasonal rainfall zone (east). Community diversity, or biological heterogeneity, showed no significant variation in relation to geography and topography. Diversity patterns of rare species mirrored the diversity pattern for all species. We hypothesize that regional diversity patterns are the product of different speciation and extinction histories, leading to different steady‐state diversities. Greater Pleistocene climatic stability in the west would have resulted in higher rates of speciation and lower rates of extinction than in the east, where for the most, Pleistocene climates would not have favoured Cape lineages. A more parsimonious hypothesis is that the more predictable seasonal rainfall of the west would have favoured non‐sprouting plants and that this, in turn, resulted in higher speciation and lower extinction rates. Both hypotheses are consistent with the higher incidence of rare species in the west, and higher levels of beta and gamma diversity there, associated with the turnover of species along environmental and geographical gradients, respectively. These rare species do not contribute to community patterns; hence, biological heterogeneity is uniform across the region. The weak topography pattern of diversity in the west arises from higher speciation rates and lower extinction rates in the topographically complex mountains, rather than from the influence of environmental heterogeneity on diversity.     

Ejaculate-female coevolution in Drosophila mojavensis

Interspecific studies indicate that sperm morphology and other ejaculatory traits diverge more rapidly than other types of character in Drosophila and other taxa. This pattern has largely been attributed to postcopulatory sexual selection involving interaction between the sexes. Such divergence has been suggested to lead rapidly to reproductive isolation among populations and thus to be an 'engine of speciation.' Here, we test two critical predictions of this hypothesis: (i) there is significant variation in reproductive traits among incipient species; and (ii) divergence in interacting sex-specific traits exhibits a coevolutionary pattern among populations within a species, by examining geographical variation in Drosophila mojavensis, a species in the early stages of speciation. Significant among-population variation was identified in sperm length and female sperm-storage organ length, and a strong pattern of correlated evolution between these interacting traits was observed. In addition, crosses among populations revealed coevolution of male and female contributions to egg size. Support for these two important predictions confirms that coevolving internal characters that mediate successful reproduction may play an important part in speciation. The next step is to determine exactly what that role is.     

Ability of Ixodes persulcatus, Haemaphysalis concinna and Dermacentor silvarum ticks to acquire and transstadially transmit Borrelia garinii

In China, the ability of Ixodes persulcatus, Haemaphysalis concinna and Dermacentor silvarum to transmit Borrelia spirochetes was determined under laboratory conditions. Results showed that all three tick species can acquire spirochetes by feeding on infected mice. However, the capability of the three species to maintain spirochetes was different. Only I. persulcatus is able to maintain spirochetes alive during molting, and subsequent tick stages transmitted the infection to naive mice. In H. concinna and D. silvarum ticks, spirochetes could not survive after the digestion period of blood and after the molting process was finished, spirochetes were no longer detected. Contrary to H. concinna and D. silvarum, I. persulcatus should be considered the principal vector of Lyme disease in north China.     

Male secondary sexual characteristics, sexual selection, and molecular divergence in fanged ranid frogs of Southeast Asia

A group of Southeast Asian frogs of the family Ranidae are characterized by a suite of unusual secondary sexual characteristics. Males are larger than females, possess bony odontoid processes (fangs) and have enlarged heads. While all members of this clade are sexually dimorphic in this suite of characters, the degree of development of the secondary sexual characteristics in males varies widely across species. One of the most common species, Rana blythii Boulenger, has an extremely broad geographical range. This frog lacks an advertisement call in Borneo but calling has been reported in populations from peninsular Malaysia and Vietnam. This study examines the relationship between the expression of male secondary sexual characteristics, molecular divergence and number of speciation events in widely separated populations of R. blythii , and between R. blythii and other species of closely related fanged frogs belonging to the grunniens species group. Results from morphometric and sequence data indicate that (1) there is no correlation between morphological and molecular distance in these frogs and (2) there is no correlation between morphological distance and the number of speciation events separating taxa. Systematic analysis demonstrates that R. blythii , as currently recognized, is not a single species nor is it monophyletic.     

Evolution of mating isolation between populations of Drosophila ananassae

Prezygotic mating isolation has been a major interest of evolutionary biologists during the past several decades because it is likely to represent one of the first stages in the transition from populations to species. Mate discrimination is one of the most commonly measured forms of prezygotic isolation and appears to be relatively common among closely related species. In some cases, it has been used as a measure to distinguish populations from subspecies, races, and sister species, yet the influences of various evolutionary mechanisms that may generate mate discrimination are largely unknown. In this study, we measured the level and pattern of mate discrimination among 18 populations of a cosmopolitan drosophilid species, Drosophila ananassae , from throughout its geographical range and its sister species, Drosophila pallidosa, which has a restricted geographical distribution in the South Pacific Islands. In addition, we measured genetic differentiation between all 18 populations using mitochondrial DNA polymorphism data. Mate discrimination varies considerably throughout the species range, being higher among populations outside the ancestral Indonesian range, and highest in the South Pacific. Our results suggest that colonization and genetic differentiation may have an influence on the evolutionary origin of mate discrimination. Our phylogeographical approach clarifies the ancestral relationships of several populations from the South Pacific that show particularly strong mate discrimination and suggests that they may be in the early stages of speciation. Furthermore, both the genetic and behavioral results cast doubt on the status of D. pallidosa as a good species.     

Historical biogeography of Asplenium adiantum-nigrum (Aspleniaceae) in North America and implications for speciation theory in homosporous pteridophytes

Theories of plant speciation have generally recognized the importance of allopatry as a potential precursor to the genetic divergence of populations. The relative importance of long-distance dispersal vs. vicariance events in leading to allopatry, however, has been debated. We examined isozymic variability in highly disjunct populations of allotetraploid Asplenium adiantum-nigrum to test alternative hypotheses on their mode of origin. In addition, we assessed the genetic distinctness of the population from Boulder County, Colorado, which had been proposed as a separate species, A. andrewsii. Our results revealed that samples from all continental U.S. populations were isozymically identical and, with the exception of two samples from Boulder, displayed no intrapopulational variability. Continental U.S. populations were most similar to those from Hawaii, whereas both of these sets of populations were considerably more divergent from samples from Mexico and the Caucasus. The distribution of alleles and genotypes support the hypothesis that populations from different geographical regions had unique origins, resulting from at least several independent hybridization and polyploidization events followed by long-distance dispersal. These results have implications for speciation theory of pteridophytes in documenting the effectiveness of long-distance dispersal in the establishment of disjunct populations which may set the stage for allopatric speciation. In addition, the data suggest that the Boulder population is not sufficiently distinct to be considered a separate species.     

The phylogeny of the genus Lasioserica inferred from adult morphology – implications on the evolution of montane fauna of the south Asian orogenic belt (Coleoptera: Scarabaeidae: Sericini)

The species of Lasioserica are highly diversified within the south Asian orogenic belt, such as the Himalaya, south‐eastern Tibet and the mountains of northern Indochina. The study presents a preliminary phylogeny of Lasioserica based on adult morphology. Sixty‐one species were examined for the cladistic analysis based on parsimony using successive approximations weighting and including 84 characters. As a result of the phylogenetic hypothesis on Lasioserica elaborated here, the taxonomic definition of Lasioserica and the validity of Amiserica are questionable and need to be revised. Taxonomic conclusions are here limited so far to the genus assignment of Amiserica antennalis ( Nomura 1974 ) comb. n. The cladistic analysis revealed a large monophyletic clade of Lasioserica containing almost all species assigned to this group so far. Among this monophylum the following pattern have become evident: (1) a number of ancestral lineages from the eastern Himalaya and Indochina, (2) a large clade with almost exclusively Himalayan species and (3) one clade with only Chinese and Indochinese taxa. Based on this topology we may suggest that the more recent evolution of Lasioserica was more independent in these two major regions (Himalaya/Indochina). There is comparatively good evidence from range positions of closely related species for allopatric geographical speciation in Lasioserica with the majority of closely related central Himalayan species occurring allopatrically or parapatrically. The tree topology does not permit conclusions whether speciation progressed more often from east to west or vice versa. More easterly distributed lineages in the Himalaya seem to contrast this pattern with a greater part of closely related species occurring sympatrically. Since cumulative ranges of the major lineages of the Himalayan clade overlap in all respects, diversification of the almost strictly Himalayan clade of Lasioserica should be attributed to a rather long and persistent evolution within the Himalaya.     

A test of host-associated differentiation across the 'parasite continuum' in the tri-trophic interaction among yuccas, bogus yucca moths, and parasitoids

Parasitic taxa span an antagonistic continuum, with some parasites inflicting no fitness costs to some that kill the host after feeding. Host-associated differentiation is postulated as a major process facilitating speciation in many parasitic taxa. Here, I examined the importance of host-associated differentiation in a parasitoid wasp that develops on yucca moths in the genus Prodoxus. Prodoxus are specialists on Yucca , and moth speciation is closely tied to differences in microhabitat use within a plant and among host plant species. Parasitoids in the genus Eusandalum have been reared from Prodoxus species distributed across Yucca . Estimates of host-use patterns obtained through rearings of adult wasps were combined with surveys of mitochondrial DNA cytochrome oxidase I sequence data and amplified fragment length polymorphism markers to determine if populations of Eusandalum were genetically structured based on host use. Eusandalum populations were genetically structured based on geographical distance rather than moth host species, microhabitats within plants, or Yucca species. The results are contrary to the patterns observed in the host genus Prodoxus . Although parasitoids exhibit parasite-like characteristics, these results suggest that Eusandalum may be best viewed as a predator. Female wasps are able to utilize any moth species present at a given locality, and there is little likelihood that host specialization may facilitate population subdivision and speciation.     

The relationships among the species of the Drosophila virilis group inferred from the gene Ras1 sequences

Comparative analysis of a group of closely related Drosophila species (D. virilis, D. lummei, D. novamexicana, D. americana texana, D. flavomontana, D. montana, D. borealis, D. lacicola, D. littoralis, D. kanekoi, and D. ezoana) was conducted based on an incomplete sequence of gene Ras1. The pattern of the relationships among the species corresponded to that expected from analysis of morphological and cytogenetic characters. Statistical data favoring neutrality of the substitutions examined in the Ras1 gene are presented. This character of the gene Ras1 evolution confers more reliability to reconstruction of phylogenetic relationships among closely related species. The resultant tree for main phylads of the group is as follows: (D. virilis, D. lummei, D. montana, D. ezoana).