Low Intraspecific Variation Research Articles

Comparison of Similar Arctic and Antarctic Morphotypes of Heterotrophic Protists Regarding their Genotypes and Ecotypes

The polar regions offer the opportunity to study possible diversification processes of spatially and temporally separated populations. We focused our study on similar morphotypes/species (e. g. species with the same morphology) of heterotrophic flagellates and ciliates originating from both, Antarctic and Arctic waters: 38 populations of six choanoflagellate morphospecies (Acanthocorbis unguiculata, Helgoeca nana, Diaphanoeca grandis, Savillea micropora, Stephanoeca apheles, Salpingoeca tuba), four other flagellate morphospecies (Cafeteria roenbergensis, Podomonas magma, Procryptobia sorokini, Protaspis sp.) and three ciliate morphospecies (Holosticha sp., Uronema marinum, Pseudocohnilembus persalinus). We analysed similarities and differences regarding their genotypes (SSU rDNA) and for several species regarding morphotypes and autecology (temperature and salinity tolerance). Most of the investigated polar protists were psychrophilic and showed a high salinity tolerance. Morphologically well defined acanthoecid choanoflagellates isolated from both poles showed the lowest intraspecific diversity (< 0.5% p-distance). No intragenomic polymorphism of SSU rDNA within one individual and among clones from one population occurred. The way of dispersal for acanthoecid choanoflagellates still remains unclear. Even under extreme stress none of the examined cultures formed cysts. Single cell PCR appeared to be an appropriate method to investigate species not available as monoclonal cultures. As a prerequisite for barcoding, acanthoecid choanoflagellate species have a very low intraspecific variability regarding SSU rDNA. There was a clear correlation between autecological, morphological and molecular data sets, which may help interpreting molecular data from clone libraries or next generation sequencing.

Hisonotusacuen, a new and phenotypically variable cascudinho (Siluriformes, Loricariidae, Hypoptopomatinae) from the upper rio Xingu basin, Brazil.

A new species of Hisonotus is described from the headwaters of the rio Xingu. The new species is distinguished from its congeners by having a functional V-shaped spinelet, odontodes not forming longitudinal aligned rows on the head and trunk, lower counts of the lateral and median series of abdominal figs, presence of a single rostral fig at the tip of the snout, absence of the unpaired figlets at typical adipose fin position, yellowish-tipped teeth, absence of conspicuous dark saddles and stripe on the body and higher number of teeth on the premaxillary and dentary. The new species, Hisonotus acuen, is restricted to headwaters of the rio Xingu basin, and is the first species of the genus Hisonotus described from the rio Xingu basin. Hisonotus acuen is highly variable in aspects of external body proportions, including body depth, snout length, and abdomen length. This variation is partly distributed within and among populations, and is not strongly correlated with body size. PCA of 83 adult specimens from six allopatric populations indicates the presence of continuous variation. Therefore, the available morphological data suggest that the individuals inhabiting the six localities of rio Xingu represent different populations of a single species. Low intraspecific variation in mitochondrial Cytochrome oxidase subunit I (COI) provides corroborative evidence.

Cytogenetic, cross-mating and molecular evidence of four cytological races of Anopheles crawfordi (Diptera: Culicidae) in Thailand and Cambodia

Twenty-nine isolines of Anopheles crawfordi were established from wild-caught females collected from cow-baited traps in Thailand and Cambodia. Three types of X (X1, X2, X3) and four types of Y (Y1, Y2, Y3, and Y4) chromosomes were identified, according to differing amounts of extra heterochromatin. These sex chromosomes represent four metaphase karyotypes, i.e., Forms A (X1, X2, X3, Y1), B (X1, X2, X3, Y2), C (X2, Y3) and D (X2, Y4). Forms C and D are novel metaphase karyotypes confined to Thailand, whereas forms A and B appear to be common in both Thailand and Cambodia. Cross-mating experiments between the four karyotypic forms indicated genetic compatibility in yielding viable progenies and synaptic salivary gland polytene chromosomes. The results suggest that the forms are conspecific and A. crawfordi comprises four cytological races, which is further supported by very low intraspecific variation (mean genetic distance=0.000–0.018) of the nucleotide sequences in ribosomal DNA (ITS2) and mitochondrial DNA sequences (COI, COII).

Closely related and sympatric but not all the same: genetic variation of Indo-West Pacific Rhizophora mangroves across the Malay Peninsula

Members of the mangrove genus Rhizophora represent the most commonly occurring and highly valued species in the Indo-West Pacific region. However, to date, few studies have been directed towards the understanding of their genetic variation. The levels and patterns of genetic variation at chloroplast and nuclear gene regions were studied in R. apiculata, R. mucronata, and R. stylosa sampled from Southeast Asia and Japan. All three species were characterized by low intraspecific genetic variation and a deficiency of heterozygotes in populations within the region, consistent with findings in studies on other mangrove species. Rhizophora mucronata and R. stylosa were also found to be more closely related than any of them with R. apiculata. During the Last Glacial Maximum, sea levels dropped to 120 m below the current levels, exposing part of the Sunda Shelf that became a barrier that limited gene flow between marine species living in the Pacific and Indian Oceans. Today, the Malay Peninsula is thought to still serve as a barrier to gene flow between populations occurring on its coasts. The pattern of genetic differentiation of R. apiculata supports the hypothesis of the land barrier effect of the Malay Peninsula, but such patterns were not found in R. mucronata and R. stylosa. Our findings suggest that R. apiculata, R. mucronata, and R. stylosa have different demographic histories despite being closely related and having sympatric distributions today. Furthermore, all three species appear to have high levels of inbreeding due to limited pollen and propagule dispersal, and that both these factors contributed to population differentiation.

The evolution of rbcL: A methodology to follow the evolution patterns of Medicago and Sulla (Fabaceae) genera

The chloroplast rbcL gene is selected to be a standard barcode for the phylogenetic analyses of several land plants. Using universal primers pair, the 3’ frame was used to assess the phylogeny of the two Legume genera Medicago and Sulla and the evolution of the translated protein. The multiple alignment exhibited high conservation rates (97.56% and 96.43% for Medicago and Sulla respectively), which might be a brake for the phylogenetic assessment. Nevertheless, the topologies of the cladograms drawn using Maximum Likelihood method, showed a low intraspecific divergence and a slightly high interspecific variation, which confirms the efficiency of rbcL for such characterization’ analyses. Besides, the composition and the patterns of the Amino-Acid sequence and the deduced Codon Usage, highlighted a non-aleatoire distribution of the codons. Thus, the non-synonymous substitutions rates traduced a positive selection occurring in the rbcL of the Medicago and Sulla species.

Taxonomic Validity and Phylogeography of the East Eurasian Natricine Snake,Rhabdophis lateralis(Berthold, 1859) (Serpentes: Colubridae), as Inferred from Mitochondrial DNA Sequence Data

We investigated the phylogenetic status and pattern of geographic variation in Rhabdophis lateralis on the basis of samples from across continental China, southeastern Russia, and the Korean Peninsula. The results confirmed the monophyly of the species and also revealed its extremely low genetic divergence. The population genetic analyses suggested that such low intraspecific divergence may reflect recent rapid population growth from a small ancestral population, extensive gene flow, or both. We conclude that R. lateralis is a good species, as suggested by our previous study, which analyzed fewer continental samples from a more limited range.

Species delimitation of three species within the Russula subgenus Compacta in Korea: R. eccentrica, R. nigricans, and R. subnigricans.

Distinguishing individual Russula species can be very difficult due to extensive phenotypic plasticity and obscure morphological and anatomical discontinuities. In this study, we use the internal transcribed spacer (ITS) and 28S nuclear ribosomal large subunit (LSU) markers to identify and study the genetic diversity of species in the Russula subgenus Compacta in Korea. We focus on two morphologically similar species that are often misidentified for each other: R. nigricans and R. subnigricans. Based on molecular phylogenetic analyses, we identify three subgroups of R. nigricans, with two from Asia and one from Europe/North America. Surprisingly, we find Korean R. subnigricans are more closely related to R. eccentrica from North America than the type specimen of R. subnigricans from Japan. These molecular data, along with habitat data, reveal that Korean R. subnigricans had previously been misclassified and should now be recognized as R. eccentrica. Both ITS and LSU exhibit high interspecific and low intraspecific variation for R. eccentrica, R. nigricans, and R. subnigricans. These markers provide enough resolutional power to differentiate these species and uncover phylogeographic structure, and will be powerful tools for future ecological studies of Russula.

DNA barcoding works in practice but not in (neutral) theory.

BackgroundDNA barcode differences within animal species are usually much less than differences among species, making it generally straightforward to match unknowns to a reference library. Here we aim to better understand the evolutionary mechanisms underlying this usual “barcode gap” pattern. We employ avian barcode libraries to test a central prediction of neutral theory, namely, intraspecific variation equals 2 Nµ, where N is population size and µ is mutations per site per generation. Birds are uniquely suited for this task: they have the best-known species limits, are well represented in barcode libraries, and, most critically, are the only large group with documented census population sizes. In addition, we ask if mitochondrial molecular clock measurements conform to neutral theory prediction of clock rate equals µ.ResultsIntraspecific COI barcode variation was uniformly low regardless of census population size (n = 142 species in 15 families). Apparent outliers reflected lumping of reproductively isolated populations or hybrid lineages. Re-analysis of a published survey of cytochrome b variation in diverse birds (n = 93 species in 39 families) further confirmed uniformly low intraspecific variation. Hybridization/gene flow among species/populations was the main limitation to DNA barcode identification.Conclusions/SignificanceTo our knowledge, this is the first large study of animal mitochondrial diversity using actual census population sizes and the first to test outliers for population structure. Our finding of universally low intraspecific variation contradicts a central prediction of neutral theory and is not readily accounted for by commonly proposed ad hoc modifications. We argue that the weight of evidence–low intraspecific variation and the molecular clock–indicates neutral evolution plays a minor role in mitochondrial sequence evolution. As an alternate paradigm consistent with empirical data, we propose extreme purifying selection, including at synonymous sites, limits variation within species and continuous adaptive selection drives the molecular clock.

Evolutionary and demographic history among Maghrebian Medicago species (Fabaceae) based on the nucleotide sequences of the chloroplast DNA barcode trnH-psbA

Data from trnH-psbA intergenic spacer (cpDNA) were analyzed to elucidate molecular evolution within and among Maghrebian species of Medicago. The spacer highlighted a high interspecific variation and a low intraspecific diversity among species. Haplotype and nucleotide diversities revealed high level of variation. Parsimony and median-joining Network methods revealed (1) the segregation into 17 haplotypes; (2) the ancestral behaviour of the annual Medicago minima and (3) the clusters are independent of the geographic origin. The neutral evolution of Wright and Fisher is rejected since the Tajima's D values deviated from 0. Besides, the statistical analyses are in agreement with an evolution into stable populations' size.

DNA barcoding as a screening tool for cryptic diversity: an example from Caryocolum, with description of a new species (Lepidoptera, Gelechiidae).

We explore the potential value of DNA barcode divergence for species delimitation in the genus Caryocolum Gregor & Povolný, 1954 (Lepidoptera, Gelechiidae), based on data from 44 European species (including 4 subspecies). Low intraspecific divergence of the DNA barcodes of the mtCOI (cytochrome c oxidase 1) gene and/or distinct barcode gaps to the nearest neighbor support species status for all examined nominal taxa. However, in 8 taxa we observed deep splits with a maximum intraspecific barcode divergence beyond a threshold of 3%, thus indicating possible cryptic diversity. The taxonomy of these taxa has to be re-assessed in the future. We investigated one such deep split in Caryocolum amaurella (Hering, 1924) and found it in congruence with yet unrecognized diagnostic morphological characters and specific host-plants. The integrative species delineation leads to the description of Caryocolum crypticum sp. n. from northern Italy, Switzerland and Greece. The new species and the hitherto intermixed closest relative C. amaurella are described in detail and adults and genitalia of both species are illustrated and a lectotype of C. amaurella is designated; a diagnostic comparison of the closely related C. iranicum Huemer, 1989, is added.

Genotypic and phenotypic characterization of foodborne Geobacillus stearothermophilus

Geobacillus stearothermophilus is the main thermophilic spore former involved in flat sour spoilage of canned foods. Three typing methods were tested and applied to differentiate strains at intra-species level: panC sequence analysis, REP-PCR and M13-PCR. panC gene was highly conserved within the studied strains, suggesting a low intra-specific diversity. This was supported by REP-PCR primary assays and M13-PCR results. M13-PCR profile analysis succeeded in differentiating six closely related groups (at 79% threshold similarity) among 127 strains from a range of spoiled canned food products and from different canneries. Phenotypic traits were investigated among 20 selected strains representing groups and origins. Ranges of growth under different temperatures (from 40 °C to 70 °C), pH (from 5.0 to 6.5), NaCl concentrations (from 1 to 5%) and sporulation conditions poorly differed between strains, but wet heat resistance of spores showed a 20-fold variation between strains. Furthermore, in this study, strains that belonged to the same M13-PCR genetic group did not share phenotypic characteristics or common origin. The work emphasizes a low diversity within the G. stearothermophilus species but data from this study may contribute to a better control of G. stearothermophilus spoilage in canned food.

Evidence to support a conspecific nature of allopatric cytological races of Anopheles nitidus (Diptera: Culicidae) in Thailand.

Metaphase karyotype investigation on two allopatric strains of Anopheles nitidus Harrison, Scanlon, and Reid (Diptera: Culicidae) was conducted in Thailand during 2011–2012. Five karyotypic forms, i.e., Form A (X 1 , Y 1 ), Form B (X 1 , Y 2 ), Form C (X 2 , Y 3 ), Form D (X 1 , X 3 , Y 4 ), and Form E (X 1 , X 2 , X 3 , Y 5 ) were obtained from a total of 21 isofemale lines. Forms A, B, and C were confined to Phang Nga Province, southern Thailand, whereas Forms D and E were restricted to Ubon Ratchathani Province, northeastern Thailand. Cross-mating experiments among the five isofemale lines, which were representative of five karyotypic forms of An. nitidus , revealed genetic compatibility by providing viable progenies and synaptic salivary gland polytene chromosomes through F 2 generations. The results suggest that the forms are conspecific, and An . nitidus comprises five cytological races. The very low intraspecific sequence variations (average genetic distances = 0.002–0.008) of the nucleotide sequences in ribosomal DNA (internal transcribed spacer 2) and mitochondrial DNA (cytochrome c oxidase subunits I and II) among the five karyotypic forms were very good supportive evidence.

Coevolution of male and female genitalia in stalk-eyed flies (Diptera: Diopsidae)

The present study investigates the coevolution of a particular male genital process and the female spermathecal ducts in a clade of stalk-eyed flies (Diptera, Diopsidae) and debates the underlying evolutionary mechanisms. The fine morphology and interaction of the male and female genitalic structures are reconstructed from serial sections of mating pairs in one of the species. It is found that the male genital process traverses the common spermathecal duct to enter the base of one of the separate spermathecal ducts during the mating. Spermatozoa and accessory secretions are not transferred through the male genital process but can be discharged only from the male gonopore near its base. A detailed morphometric study reveals low intraspecific variation and hypoallometry of the male genital process. Across 17 species studied comparatively, the lengths of the male genital process and the female common and separate spermathecal ducts are highly variable. The length of the male genital process is correlated significantly with that of the female common spermathecal duct, but not with that of the separate spermathecal ducts. Based on the combined evidence it is concluded that the male genital process and the female common spermathecal duct have coevolved, and that sexual selection by cryptic female choice constitutes a possible and parsimonious explanation for their coevolution. Alternative or additional explanations in terms of sexually antagonistic coevolution cannot be ruled out conclusively, but are not supported by the available evidence.

Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population

Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.

Cytogenetic, hybridization and molecular evidence of four cytological forms ofAnopheles nigerrimus(Hyrcanus Group) in Thailand and Cambodia

Thirteen isoline colonies of Anopheles nigerrimus were established from individual wild-caught females collected from cow-baited traps at locations in Thailand and Cambodia. Three types of X (X1 , X2 , X3 ) and 4 types of Y (Y1 , Y2 , Y3 , Y4 ) chromosomes were recovered, according to differing amounts of extra heterochromatin. Four karyotypic forms were designed depending upon apparently distinct figures of X and Y chromosomes, i.e., Form A (X1 , X2 , X3 , Y1 ), B (X2 , X3 , Y2 ), C (X1 , Y3 ), and D (X3 , Y4 ). Forms C and D were new metaphase karyotypes discovered in this study. Form A appeared to be common in both Thailand and Cambodia. Forms B and D were found to be rather specific to southern and northeastern Thailand, respectively, whereas Form C was confined to Cambodia. Hybridization experiments among the eight isoline colonies, which were representative of four karyotypic forms of An. nigerrimus, demonstrated genetic compatibility in giving viable progenies and synaptic salivary gland polytene chromosomes through F2 -generations. These results elucidated the conspecific relationship, comprising four cytological forms within this taxon. Supportive evidence was confirmed further by very low intraspecific sequence variations (average genetic distance = 0.002-0.007) of the nucleotide sequences in ribosomal DNA [second internal transcribed spacer (ITS2)] and mitochondrial DNA [cytochrome c oxidase subunit I (COI) and subunit II (COII)].

Comparison of molecular species identification for North Sea calanoid copepods (Crustacea) using proteome fingerprints and DNA sequences

Calanoid copepods play an important role in the pelagic ecosystem making them subject to various taxonomic and ecological studies, as well as indicators for detecting changes in the marine habitat. For all these investigations, valid identification, mainly of sibling and cryptic species as well as early life history stages, represents a central issue. In this study, we compare species identification methods for pelagic calanoid copepod species from the North Sea and adjacent regions in a total of 333 specimens. Morphologically identified specimens were analysed on the basis of nucleotide sequences (i.e. partial mitochondrial cytochrome c oxidase subunit I (COI) and complete 18S rDNA) and on proteome fingerprints using the technology of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). On all three molecular approaches, all specimens were classified to species level indicated by low intraspecific and high interspecific variability. Sequence divergences in both markers revealed a second Pseudocalanus species for the southern North Sea identified as Pseudocalanus moultoni by COI sequence comparisons to GenBank. Proteome fingerprints were valid for species clusters irrespective of high intraspecific variability, including significant differences between early developmental stages and adults. There was no effect of sampling region or time; thus, trophic effect, when analysing the whole organisms, was observed in species-specific protein mass spectra, underlining the power of this tool in the application on metazoan species identification. Because of less sample preparation steps, we recommend proteomic fingerprinting using the MALDI-TOF MS as an alternative or supplementary approach for rapid, cost-effective species identification.

Stable oxygen and carbon isotope systematics of exquisitely preserved Turonian foraminifera from Tanzania — Understanding isotopic signatures in fossils

The interpretation of δ18O and δ13C analyses of extinct foraminifera is hampered by insufficient knowledge on the contribution of environmental versus biological factors on the measured values. We present single-species stable isotope data for 18 benthic and 11 planktic foraminiferal species and one calcareous dinoflagellate cyst species from a Turonian equatorial record measured on samples collected in SE Tanzania. All microfossils analyzed were excellently preserved and results are compared to isotopic measurements from bulk sediment of the same material. Remarkably low intra-specific variability (standard deviations < 0.2‰) across the studied interval and consistently large benthic/planktic offsets in δ18O (~ 2.8‰) and δ13C (~ 1.5‰) indicate absence of major long-term environmental fluctuations and presence of a well stratified water column. Stratigraphic isotopic trends show small shifts that are parallel in all studied benthic species (with the exception of the δ13C record of Lenticulina species), but within-sample inter-specific offsets reflect a combination of habitat differences and species-specific isotopic disequilibrium fractionation. Among planktic taxa closely related taxa tend to have similar isotopic values. Biserial taxa have the lowest δ18O values (~− 4.7‰) but also have relatively low δ13C values (~ 1.6‰) indicating that, for the assumption of a surface water habitat, additional metabolic effects need to be involved, which supports the concept of their opportunistic lifestyle. Among trochospiral planktics the keeled taxa with compressed chambers have slightly higher δ18O (~− 4.2‰) and lower δ13C (~ 2.3‰) values than taxa with globular chambers (~− 4.4‰ and ~ 2.4‰, respectively), suggesting differences in habitat or in peak seasonal abundance. Benthic taxa are subdivided into three isotopically distinct groups with differences reflecting mineralogy, life strategy and habitat; Group I: aragonitic taxa (Epistomina, Colomia africana), Group II: calcitic trochospiral taxa with isotopic values seemingly close to equilibrium (Berthelina berthelini, Oridorsalis umbonatus, Lingulogavelinella globosa, Lingulogavelinella convexa) and Group III: calcitic taxa with low δ18O values and large scatter in δ13C values (Lenticulina). Four other benthic species show values between Groups II and III. The wealth and consistency of data, especially for benthic taxa, permit refined conclusions. The five studied species of Epistomina have a similar isotopic signature and are inferred to form their aragonitic shells with close to equilibrium values. Small isotopic offsets are seen among species that differ in orientation of the septal foramen, but no offsets are seen that seem to co-vary with test shape or ornamentation. The conical species C. africana has δ18O values ~ 0.2‰ lower and δ13C values ~ 0.7‰ lower than species of Epistomina. The latter offset probably reflects an infaunal habitat for C. africana. Epistomina and Group II species are recommended for paleoenviromental studies. Mono-specific Lenticulina δ18O values may be used if increased by correction factors of 0.4‰ to 0.9‰, but this taxon's low and variable δ13C values are interpreted to reflect incorporation of respiratory CO2, possibly combined with fast growth rates related to opportunism, rather than equilibrium with benthic dissolved inorganic carbon. The observed stability of inter-specific isotopic offsets suggests disequilibrium isotopic effects are relatively consistent for many taxa in this section, and correction factors are proposed that may help to generate more robust Upper Cretaceous foraminiferal isotopic records. However, δ18O/δ13C covariance in some benthic inter-specific comparisons suggests offsets might vary with changes in temperature, food supply or other factors so the appropriateness of the correction factors should be confirmed before being applied at different sites. Similarities between the observed single-species isotopic patterns from this and other studies are used to present a summarizing scheme of influences on the stable isotopic composition in foraminiferal tests. By applying the new insights from our study to data from other Cretaceous studies we demonstrate that the selection of species for isotopic analysis and understanding these signals are critical to the outcome of paleoceanographic interpretations.

Divergence and species discrimination in freshwater bryozoans (Bryozoa: Phylactolaemata)

We explored the suitability of nuclear and mitochondrial ribosomal markers [small subunit nuclear ribosomal RNA gene, large subunit nuclear ribosomal RNA gene, and a region spanning partial small mitochondrial ribosomal RNA subunit, four transfer RNA genes, and partial large mitochondrial ribosomal RNA subunit (referred to as rrnS-rrnL)] for resolving patterns of diversification of 27 freshwater bryozoan species (class: Phylactolaemata) and evaluated the utility of statoblast ultrastructural features and molecular phylogenies for species discrimination in the Fredericellidae and Plumatellidae. Molecular data identified Plumatella fruticosa as distinct from the rest of the plumatellids, rendering the latter polyphyletic. rrnS-rrnL was the most suitable marker for species discrimination and identified two undescribed species of Plumatella and at least two undescribed species of Fredericella. Lack of wide dispersal by fredericellid statoblasts may underlie the observed propensity for cryptic speciation and phylogeographical structure in Fredericella. Conversely, the strong dispersal potential of plumatellid statoblasts may mediate efficient gene flow between distant populations and explain the relatively low intraspecific divergence and lack of evidence for cryptic speciation. We show that species identification based on external features of statoblasts can be problematic in both genera, including for a putatively highly invasive, biofouling species, Plumatella vaihiriae, thereby highlighting the utility of rrnS-rrnL sequences for species barcoding. © 2013 The Linnean Society of London

Sympatric Polymorphism in Lake Trout: The Coexistence of Multiple Shallow‐Water Morphotypes in Great Bear Lake

AbstractPolymorphism in northern fishes is common, but the extent to which polymorphism occurs in Lake Trout Salvelinus namaycush, a species generally associated with low intraspecific variation, is not well known. This study examined the polymorphism of Lake Trout inhabiting the shallow‐water zones (≤30 m) of Great Bear Lake, Northwest Territories. We combined an analysis of classical morphometric and traditional linear measures with shape analysis (geometric morphometrics) to quantify morphological differences in body shape, head shape, and fin and body length measurements among 558 adult and 55 juvenile shallow‐water Lake Trout from Great Bear Lake. A UPGMA cluster analysis on adult Lake Trout distinguished three different morphs that coexist in the shallow‐water habitat. The most important differences among adult morphotypes were associated with head and fin measurements, whereas body shape variation was less distinct. A fourth, albeit rarer, morph was supported by a multivariate ANOVA that indicated significant differences in head and fin characteristics among the four groups. The divergent morphologies among the shallow‐water Lake Trout of Great Bear Lake are consistent with traits generally associated with feeding and swimming. In contrast to adult trout, no consistent patterns were found for juveniles, suggesting that phenotypic differences develop at a later stage. This unusual level of endemic diversity in the shallow‐water habitat expands our knowledge of Lake Trout diversity beyond the predominant focus on shallow‐ versus deepwater forms.

Phylogeographic evidence for a link of species divergence of Ephedra in the Qinghai-Tibetan Plateau and adjacent regions to the Miocene Asian aridification.

The Qinghai-Tibetan Plateau (QTP) has become one of the hotspots for phylogeographical studies due to its high species diversity. However, most previous studies have focused on the effects of the Quaternary glaciations on phylogeographical structures and the locations of glacial refugia, and little is known about the effects of the aridization of interior Asia on plant population structure and speciation. Here the chloroplast DNA (cpDNA) trnT-trnF and trnS-trnfM sequences were used to investigate the differentiation and phylogeographical history of 14 Ephedra species from the QTP and northern China, based on a sampling of 107 populations. The phylogeographical analysis, together with phylogenetic reconstruction based on combined four cpDNA fragments (rbcL, rpl16, rps4, and trnS-trnfM), supports three main lineages (eastern QTP, southern QTP, and northern China) of these Ephedra species. Divergence of each lineage could be dated to the Middle or Late Miocene, and was very likely linked to the uplift of the QTP and the Asian aridification, given the high drought and/or cold tolerance of Ephedra. Most of the Ephedra species had low intraspecific variation and lacked a strong phylogeographical structure, which could be partially attributed to clonal reproduction and a relatively recent origin. In addition, ten of the detected 25 cpDNA haplotypes are shared among species, suggesting that a wide sampling of species is helpful to investigate the origin of observed haplotypes and make reliable phylogeographical inference. Moreover, the systematic positions of some Ephedra species are discussed.