Phylogeny of the tree swallow genus, Tachycineta (Aves: Hirundinidae), by Bayesian analysis of mitochondrial DNA sequences

To set the stage for historical analyses of the ecology and behavior of tree swallows and their allies (genus Tachycineta), we reconstructed the phylogeny of the nine Tachycineta species by comparing DNA sequences of six mitochondrial genes: Cytochrome b (990 base pairs), the second subunit of nicotinamide adenine dinucleotide dehydrogenase (839 base pairs), cytochrome oxidase II (85 base pairs), ATPase 8 (158 base pairs), tRNA-lysine (73 base pairs), and tRNA-methionine (25 base pairs). The phylogeny consisted of two main clades: South and Central American species ((T. stolzmanni, T. albilinea, T. albiventris), (T. leucorrhoa, T. meyeni)), and North American and Caribbean species (T. bicolor, (T. thalassina, T. euchrysea, T. cyaneoviridis)). The genetic distances among the species suggested that Tachycineta is a relatively old group compared to other New World swallow genera. One interesting biogeographic discovery was the close relationship between Caribbean and western North American taxa. This historical connection occurs in other groups of swallows and swifts as well. To reconstruct the phylogeny, we employed Bayesian as well as traditional maximum-likelihood methods. The Bayesian approach provided probability values for trees produced from the different genes and gene combinations, as well as probabilities of branches within those trees. We compared Bayesian and maximum-likelihood bootstrap branch support and found that all branches with Bayesian probabilities > or = 95% received bootstrap support >70%.     

Phylogeny of ground beetles subgenus Nialoe (s. lat.) Tanaka (Coleoptera: Carabidae; genus Pterostichus): A molecular phylogenetic approach

We constructed a phylogeny of the ground beetle subgenus Nialoe ( s. lat. ), genus Pterostichus (Coleoptera: Carabidae) based on two mitochondrial (cytochrome oxidase I and 16S ribosomal DNA) and one nuclear (28S ribosomal DNA) gene sequences. Thirty-three representative species of the group and three outgroup species were analyzed. The resultant trees (maximum parsimonious, maximum likelihood and Bayesian trees of the combined data of the three gene sequences) indicated that there are two large and three small lineages in the group, some of which were supported by a previous morphology-based phylogeny. In all the analyses, the small lineage composed of two Korean species is sister to the rest of the subgenus, but relationships of other four lineages differed among the analyses and remained unresolved. The implications of the present results are discussed in terms of taxonomy and biogeography of the group.     

Genetic diversity of trout (genus Salmo) from its most eastern native range based on mitochondrial DNA and nuclear gene variation

Russia and western Asia harbour trout populations that have been classified as distinct species and subspecies, most often on the basis of morphological and ecological variation. In order to assess their origins and to verify whether traditional taxonomy reflects their evolutionary distinctiveness, we documented their genetic relationships on the basis of mitochondrial DNA (mtDNA) RFLP, mtDNA sequence analysis, and allozyme variation. Both mtDNA and nuclear gene variation defined two ancient phylogenetic assemblages of populations distributed among northern (Baltic, White, Barents), and southern (Black, Caspian, Aral) sea basins, between which gene flow has been possible but limited in postglacial times. These results supported the traditional taxonomic differentiation between populations of these two regions. They provided weak support for the taxonomic distinction of southern brown trout (Salmo trutta) populations based on their basin of origin. They also refuted the hypothesis that L. Sevan trout (Salmo ischchan) diverged from a primitive brown trout ancestor. Nevertheless, all trout populations from southern sea basins possessed private alleles or mtDNA genotypes and were genetically distinct Therefore, they represent unique gene pools that warrant individual recognition for conservation and management.     

Phylogeny and divergence time estimation of the genus Didymodon (Pottiaceae) based on nuclear and chloroplast markers

Didymodon Hedw., with approximately 140 species in the family Pottiaceae, is distributed nearly throughout the world, with the greatest diversity and important ecological functions in drought lands and alpine ecosystems. Several studies involving morphology, molecular systematics, and macro-systematic analysis have addressed the infrageneric classification of Didymodon, but controversy over the position of the infrageneric and species classification remains due to its high degree of morphological variation in micro-habitats and strong sensitivity to climate change at regional and global scale. To date, only a few phylogenetic studies have been conducted with an incomplete number of Didymodon species; further, there is no study published regarding the divergence time of Didymodon. Consequently, we conducted a comprehensive phylogenetic analysis of Didymodon species, sampling a total of 107 species, based on one nuclear (ITS) and five chloroplast DNA. Moreover, divergence time analysis was conducted to infer the age of origin and divergence of Didymodon species. Our results presented the largest scale phylogenetic relationship of Didymodon to date and resolved the phylogenetic status of some controversial taxa and the new species. The divergence time estimation showed that Didymodon species originated around the early Cretaceous, and the diversification was concentrated in the Cretaceous and Eocene. Paleoclimate and environmental change have a direct impact on the origin and divergence of Didymodon species by shaping their morphology, resource availability and ecological niche. Our study will help understand species origin and speciation of Didymodon as well as reflecting species adaptability and experience to historical events.     

Molecular phylogeny of the large carpenter bees, genus Xylocopa (Hymenoptera: apidae), based on mitochondrial DNA sequences

Carpenter bees, genus Xylocopa Latreille, a group of bees found on all continents, are of particular interest to behavioral ecologists because of their utility for studies of the evolution of mating strategies and sociality. This paper presents phylogenetic analyses based on sequences of two mitochondrial genes cytochrome oxidase 1 and cytochrome b for 22 subgenera of Xylocopa. Maximum-parsimony and maximum-likelihood methods were used to infer phylogenetic relationships. The analyses resulted in three resolved clades of subgenera: a South American group (including the subgenera Stenoxylocopa, Megaxylocopa, and Neoxylocopa), a group including the subgenera Xylocopa s.s. and Ctenoxylocopa, and an Ethiopean group (including the subgenera Afroxylocopa, Mesotrichia, Alloxylocopa, Platynopoda, Hoploxylocopa, and Koptortosoma). The relationships between the 11 other subgenera and the resolved clades are unclear. Within the Ethiopian group we found a clear separation of the African and the Oriental taxa and apparent polyphyly of the subgenus Koptortosoma. Using an evolutionary rate for ants, we investigated whether Gondwana vicariance or more recent dispersal events could best explain the present-day distribution of subgenera. Although some taxa show divergences that approach Gondwanan breakup times, most divergences between geographic groups are too recent to support a vicariance hypothesis.     

Intraspecific or interspecific variation: delimitation of species boundaries within the genus Gammarus (Crustacea,Amphipoda, Gammaridae), with description of four new species

The delineation of Gammarus species is controversial because of extensive intraspecific morphological variation. The current study examined DNA sequences from the mitochondrial cytochrome c oxidase subunit I and the nuclear 28S genes as well as morphological and ecological data to determine the species boundaries of Gammarus species from China. The results of molecular analyses showed that Gammarus sp1, G. sp2, G. sp3, and G. sp4 are monophyletic and deeply divergent from sister groups. Detailed morphological and ecological comparisons with closely related species were consistent with molecular analyses. Gammarus sp1, G. sp2, G. sp3, and G. sp4 were described as four new species: Gammarus illustris sp. nov. , Gammarus clarus sp. nov. , Gammarus hypolithicus sp. nov. , and Gammarus parvioculus sp. nov. We recommend that molecular detected species should be formally named and described for future research. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 215–253.     

Phylogenetic relationships of five pika species (genus Ochotona) based on mitochondrial DNA restriction maps

Restriction site mapping of mitochondrial DNA (mtDNA) with 16 restriction endonucleases was used to examine the phylogenetic relationships of Ochotona cansus, O. huangensis, O. thibetana, O. curzoniae and O. erythrotis. A 1-kb length variation between 0. erythrotis of subgenus Pika and other four species of subgenus Ochotona was observed, which may be a useful genetic marker for identifying the two subgenera. The phylogenetic tree constructed using PAUP based on 61 phylogenetically informative sites suggests that O. aythrotis diverged first, followed by O. cansus, while O. atrzoniae and O. huangensis are sister taxa related to O. thibetana. The results indicate that both O. cansus and O. huangensis should be treated as independent species. If the base substitution rate of pikas mtDNA was 2% per million years, then the divergence time of the two subgenera, Pika and Ochotona, is about 8.8 Ma ago of late Miocence, middle Bao-dian of Chinese mammalian age, and the divergence of the four species in subgenus     

Lumping lumpsuckers: molecular and morphological insights into the taxonomic status of Eumicrotremus spinosus (Fabricius, 1776) and Eumicrotremus eggvinii Koefoed, 1956 (Teleostei: Cyclopteridae)

The genus Eumicrotremus comprises 16 lumpsucker species distributed in the Arctic and northern Atlantic and Pacific Oceans. The most common species in the North Atlantic is Eumicrotremus spinosus , described in 1776, and characterized partly by numerous bony tubercles on the head and body. Another Atlantic species, Eumicrotremus eggvinii , described in 1956, remained known only from a single specimen until additional specimens were recently recovered. To reassess the status of E. eggvinii , 21 meristic and 32 morphometric characters were analysed for a total of 83 specimens of E. spinosus and E. eggvinii . Mitochondrial (COI, COII and cyt- b ) and nuclear ( Tmo-4C4 ) genes were also sequenced for both species, along with Eumicrotremus derjugini . The results indicate that although E. spinosus and E. eggvinii are clearly separated by a considerable number of morphological characters, they in fact constitute a single, sexually dimorphic species. Thirteen specimens of E. eggvinii (including the holotype) and 59 E. spinosus could be sexed; all individuals of E. eggvinii turned out to be males and all E. spinosus were females. Identical DNA sequences were found in all E. eggvinii and E. spinosus for COI, COII and Tmo-4C4 , and a single shared synonymous substitution found in cyt- b . In contrast, E. spinosus , E. eggvinii and E. derjugini differed by 5·9% for COI and COII, 1·2% for Tmo-4C4 and 8·3% for cyt- b .     

New tools (DNA barcoding), old hypothesis: the case of the taxonomic identity of the Argentine hakes (Actinopterygii: Merluccius)

The present study evaluated the possible occurrence of cryptic species among Merluccidae from Argentina by examining sequences of cytochrome c oxidase subunit I (coI) mtDNA. This approach can discriminate Merluccius hubbsi and Merluccius australis; specimens with morphological diagnostic characters of Merluccius patagonicus formed a cohesive cluster with M. hubbsi specimens. BIN analysis confirmed the effectiveness of barcoding within a global context.     

Phylogeny, diversity, and species delimitation of the North American Round-Nosed Minnows (Teleostei: Dionda), as inferred from mitochondrial and nuclear DNA sequences

Accurate delimitation of species is a critical first step in protecting biodiversity. Detection of distinct species is especially important for groups of organisms that inhabit sensitive environments subject to recent degradation, such as creeks, springs, and rivers in arid or semi-desert regions. The genus Dionda currently includes six recognized and described species of minnows that live in clear springs and spring-fed creeks of Texas, New Mexico (USA), and northern Mexico, but the boundaries, delimitation, and characterization of species in this genus have not been examined rigorously. The habitats of some of the species in this genus are rapidly deteriorating, and many local populations of Dionda have been extirpated. Considering the increasing concerns over degradation of their habitat, and pending a more detailed morphological revision of the genus, we undertook a molecular survey based on four DNA regions to examine variation over the range of the genus, test species boundaries, and infer phylogenetic relationships within Dionda. Based on analyses of two mitochondrial (cytb and D-loop) and two nuclear (Rag1 and S7) DNA regions from specimens collected throughout the range of Dionda, we identified 12 distinct species in the genus. Formerly synonymized names are available for two of these species, and four other species remain undescribed. We also redefine the known range of six species. The limited distribution of several of the species, coupled with widespread habitat degradation, suggests that many of the species in this genus should be targets for conservation and recovery efforts.     

Phylogeny of the Bovidae (Artiodactyla, Mammalia), based on mitochondrial ribosomal DNA sequences.

Portions of the 12S and 16S mitochondrial ribosomal genes for 16 species representing nine tribes in the mammal family Bovidae were compared with six previously published orthologous sequences. Phylogenetic analysis of variable nucleotide positions under different constraints and weighting schemes revealed no robust groupings among tribes. Consensus trees support previous hypotheses of monophyly for four clades, including the traditional subfamily Bovinae. However, the basal diversification of bovid tribes, which was largely unresolved by morphological, immunodiffusion, allozyme, and protein sequence data, remains unresolved with the addition of DNA sequence data. The intractability of this systematic problem is consistent with a rapid radiation of the major bovid groups. Several analyses of our data show that monophyly of the Bovidae, which was weakly supported by previous morphological and molecular work, is questionable.     

Colonization and diversification of the species Brachyderes rugatus (Coleoptera) on the Canary Islands: evidence from mitochondrial DNA COII gene sequences

Abstract.— The genus Brachyderes Schönherr (Coleoptera: Curculionidae) is represented by the species B. rugatus Wollaston on the Canary Islands, with one subspecies on each of the islands of Gran Canaria, Tenerife, La Palma, and El Hierro. These four subspecies are associated with the endemic pine tree Pinus canariensis , and their distributions are broadly coincident. Eighty-eight individual Canarian Brachyderes , sampled from across the distributions of each subspecies, have been sequenced for 570 bp of the mitochondrial DNA (mtDNA) cytochrome oxidase II gene (COII). No mitotypes are shared among islands. Both maximum-likelihood and distance-based phylogenetic analyses have shown that: Tenerife is composed of a single monophyletic clade of mitotypes, El Hierro is composed of a single monophyletic clade occurring within a larger clade comprising all the La Palma mitotypes, and the mitotypes of these three islands form a monophyletic group distinct from Gran Canaria. New methods for estimating divergence times without the assumption of rate constancy have been used to reconstruct the direction and approximate timing of colonizations among the islands. Colonization has occurred from older to progressionally younger islands, and these colonizations are estimated to have occurred less than 2.6 million years ago, although the timing of the initial colonization of the archipelago is not discernable. New methods for the estimation of diversification rates that use branching times as the analyzed variable have been applied to each island fauna. Hypothesized effects of different levels of recent volcanism among islands were not apparent. All islands exhibit a gradually decreasing rate of genetic diversification that is marked by periodic sudden changes in rate.     

Phylogeny of Polygonia, Nymphalis and related butterflies (Lepidoptera: Nymphalidae): a total-evidence analysis

We investigated the phylogeny of butterflies in the tribe Nymphalini sensu Harvey 1991, comprising the genera Vanessa, Cynthia, Bassaris, Aglais, Inachis, Nymphalis, Polygonia, Kaniska, Antanartia, Hypanartia, Symbrenthia, Mynes and Araschnia . Evidence from the mitochondrial gene ndl, the nuclear gene 'wingless' and from morphology/ ecology/behaviour were used separately and combined to analyse relationships. Phylogenies based on the different types of data agreed in many aspects of basic topology. We show that an analysis of only wing pattern characters (based on Nijhout's homology system) results in a topology broadly similar to the one resulting from analysis of the complete matrix. We found support for a monophyletic Nymphalini, where Hypanartia may be the sister clade to all other genera. Mynes, Symbrenthia and Araschnia together seem to form another basal clade. Evidence presented gives only moderate support for a monophyletic Vanessa in the wide sense, including also Cynthia and Bassaris , but strong support for the monophyly of the largely holarctic clade Aglais + Inachis + Nymphalis + Polygonia + Kaniska + Roddia . Within the latter group there is strong support for a clade consisting of Aglais + Inachis and for a second clade which includes Nymphalis, Polygonia (and its sister clade, the monotypic Kaniska) as well as Roddia l-album (= Nymphalis vaualbum ). As a consequence of this topology, Aglais is recognized as a taxon separate from Nymphalis . We present a hypothesis of species relationships within the focal group of genera. We also analyse and discuss the implications of excluding or including ecological data in phylogenetic tree construction, when the tree is to be used for studies in phylogenetic ecology.     

Replication of chloroplast, mitochondrial and nuclear DNA during growth of unirradiated and UVB-irradiated Arabidopsis leaves

Replication of Arabidopsis nuclear, mitochondrial and chloroplast DNA (ncDNA, mtDNA, cpDNA) was assayed by measuring respective changes in copies per leaf, employing quantitative PCR (QPCR) analysis with genome-specific primer pairs. All three genomes showed parallel increases during growth of cotyledons and 5th leaves in planta, maintaining approximately 13 mtDNA copies and 280 cpDNA copies per haploid nuclear genome. Detached 5th leaves, which showed good growth and DNA replication on agar plates, were irradiated at (DNA-effective) UV-B fluences of 1.3-5.0 kJ m-2 and incubated under blue (photorepair-active) plus gold light or gold light only. Under blue light, replication of all genomes after all UV fluences was approximately as efficient as replication in unirradiated leaves. UV-irradiated leaves showed little growth under gold light only; 5 kJ m-2 stopped replication of all three genomes, 2.5 kJ m-2 stopped only cpDNA replication, and 1.3 kJ m-2 only delayed cpDNA replication. Immunoassays showed that 5 kJ m-2 induced about 1.2 cyclobutane pyrimidine dimers and 0.1 [6-4]photoproducts per kbp of bulk DNA, and that both photoproducts were completely removed during 2-3 days under blue light, suggesting efficient photorepair of at least ncDNA and cpDNA. The evidence for efficient photorepair of organellar DNA contrasts with previous studies of irradiated 5-day-old seedlings, and with the apparent absence of Arabidopsis photolyases bearing transit peptides.     

Discus fishes: mitochondrial DNA evidence for a phylogeographic barrier in the Amazonian genus Symphysodon (Teleostei: Cichlidae)

Genetic relationships and variation in meristic counts, body shape and colour were examined in a large sample of Symphysodon collected from several locations in floodplain habitats along the length of the Amazon River. Surprisingly, mitochondrial DNA indicates no difference between the two historically described species, Symphysodon discus and Symphysodon aequifasciatus , but shows that non-clinal variation exists with a distinct lineage found in the western Amazon. This lineage is consistent with a colour form that is distinct from other Symphysodon lineages. This form has a parapatric distribution and is recognized as a distinct species, Symphysodon tarzoo . Adaptation to floodwater habitats supports genetic cohesion across a large range preventing fine scale regional diversification of the genus. Possible explanations for the unusual set of distributions for genetic and colour characters relate to the history of the Amazon basin and the probable division of lowland species when submerged geologic arches influence surface topology.     

Phylogeny of Anophelinae (Diptera: Culicidae) based on nuclear ribosomal and mitochondrial DNA sequences

Abstract Phylogenetic relationships among thirty-two species of mosquitoes in subfamily Anophelinae are inferred from portions of the mitochondrial genes COI and COII, the nuclear 18S small subunit rRNA gene and the expansion D2 region of the nuclear large subunit 28S rRNA gene. Sequences were obtained from the genera Anopheles , Bironella and Chagasia . Representatives of all six subgenera of Anopheles were included: Anopheles , Cellia , Kerteszia , Lophopodomyia , Nyssorhynchus and Stethomyia. Using parsimony and maximum likelihood methods, various combinations of these DNA sequence data were analysed separately: 18S, 28S, combined 18S and 28S, combined COI and COII, and combined 18S, 28S, COI and COII ('total evidence'). The combined rDNA data contain strong phylogenetic signal, moderately to strongly supporting most clades in MP and ML analyses; however, the mtDNA data (analysed as either nucleotide or amino acid sequences) contain little phylogenetic signal, except for relationships of very recently derived groups of species and, at the deepest level, for the monophyly of Anophelinae. The paraphyly of Anopheles relative to Bironella is confirmed by most analyses and statistical tests. Support for the monophyly of subgenera Anopheles , Cellia , Kerteszia and Nyssorhynchus is indicated by most analyses. Subgenus Lophopodomyia is reconstructed as the sister to Bironella , nested within a clade also containing Nyssorhynchus and Kerteszia . The most basal relationships within genus Anopheles are not well resolved by any of the data partitions, although the results of statistical analyses of the rDNA data (S-H-tests, likelihood ratio tests for monophyly and Bayesian MCMC analyses) suggest that the clade consisting of Bironella , Lophopodomyia , Nyssorhynchus and Kerteszia is the sister to the clade containing Cellia and Anopheles .     

Phylogeny of leafcutter ants in the genus Atta Fabricius (Formicidae: Attini) based on mitochondrial and nuclear DNA sequences

Leafcutting ants of the genus Atta are the most conspicuous members of the tribe Attini, the fungus-growing ants. Atta species have long attracted the attention of naturalists, and have since become a common model system for the study of complex insect societies as well as for the study of coevolutionary dynamics due to their numerous interactions with fungi and other microbes. Nevertheless, systematics and taxonomy of the 15 species in the genus Atta have proven challenging, due in part to the extreme levels of worker polymorphism these species display, leading to disagreements about the validity of as many as five different subgenera and calling into question the monophyly of the genus. Here, we use DNA sequence information from fragments of three mitochondrial genes (COI, tRNA leucine and COII) and one nuclear gene (EF1-αF1), totaling 1070 base pairs, to reconstruct the phylogenetic relationships of Atta species using maximum parsimony, maximum likelihood and Bayesian inference techniques. Our results provide support for monophyly of the genus Atta, and suggest that the genus is divided into four monophyletic groups, which correspond to four of the five previously erected Atta subgenera: Atta sensu stricto and Archeatta, each with species composition identical to earlier proposals; Neoatta and Epiatta, with major differences in species composition from earlier proposals. The current geographic ranges of these species suggest that the historical separation of South America from Central and North America has played a role in speciation within this genus.     

Phylogeographic history of Patagonian lizards of the Liolaemus elongatus complex (Iguania: Liolaemini) based on mitochondrial and nuclear DNA sequences

In this study, we present a phylogeographic analysis of a group of lizards distributed in north‐western Patagonia, the Liolaemus elongatus complex. We sequenced 581 individuals for one mitochondrial gene (cytochrome‐b), and for a subset, we sequenced another mitochondrial gene (12S rRNA) and two nuclear genes: kinesin family member 24 (KIF24) and the anonymous nuclear locus LDAB1D. We estimated gene trees, mitochondrial and nuclear haploytpe networks, standard molecular diversity indices, genetic distances between lineages and Bayesian skyline plots. Our results provide evidence for recognition of seven species previously described within the L. elongatus complex: Liolaemus antumalguen, Liolaemus chillanensis, Liolaemus carlosgarini, Liolaemus burmeisteri, Liolaemus smaug, Liolaemus elongatus and Liolaemus crandalli, but we did not find sufficient evidence to support Liolaemus choique, Liolaemus shitan or Liolaemus sp. 6 as distinct species. We identified four candidate species (Liolaemus sp. 1, Liolaemus sp. 2, Liolaemus sp. 3 and Liolaemus sp. 7), and we discuss evolutionary processes that may have contributed to the origin of these lineages and their taxonomic and conservation implications.     

Chromosomal location and distribution of As51 satellite DNA in five species of the genus Astyanax (Teleostei, Characidae, Incertae sedis)

Constitutive heterochromatin makes up a substantial portion of the genome of eukaryotes and is composed mainly of satellite DNA repeating sequences in tandem. Some satellite DNAs may have been derived from transposable elements. These repetitive sequences represent a highly dynamic component of rapid evolution in genomes. Among the genus Astyanax , the As51 satellite DNA is found in species that have large distal heterochromatic blocks, which may be considered as derived from a transposable DNA element. In the present study, As51 satellite DNA was mapped through in situ fluorescent hybridization in the chromosomes of five species of the genus. The possible roles of this type of saltatory DNA type in the genome of the species are discussed, along with its use for the phylogenetic grouping of the genus Astyanax , together with other shared chromosomal characters. However, the number of As51 clusters is presented as a homoplastic characteristic, thereby indicating evident genomic diversification of species with this type of DNA.     

Phylogeny of the genus Aphis Linnaeus, 1758 (Homoptera: Aphididae) inferred from mitochondrial DNA sequences

Aphis is the largest aphid genus in the world and contains several of the most injurious aphid pests. It is also the most reluctant aphid genus to any comprehensive taxonomic treatment: while most species are easily classified into "species groups" that form well defined entities, numerous species within these groups are difficult to tell apart morphologically and identification keys remain ambiguous and mostly rely on host plant affiliation. In this paper, we used partial sequences of COI/COII and CytB genes to reconstruct the first phylogeny of Aphis and discuss the present systematics. The monophyly of the subgenus Bursaphis and of the tree major species groups, Black aphid, Black backed aphid and frangulae-like species was recovered by all phylogenetic analyses. However our data suggested that the nominal subgenus was not monophyletic. Relationships between major species groups were often ambiguous but "Black" and "Black backed" species groups appeared as sister clades. The most striking result of this study was that our molecular data met the same limits as the morphological characters used in classifications: mitochondrial DNA did not allow the differentiation of species that are difficult to identify. Further, interspecies relationships within groups of species for which taxonomic treatment is difficult stayed unresolved. This suggests that species delineation in the genus Aphis is often ambiguous and that diversification might have been a rapid process.