COI Haplotypes Research Articles

Islands in ice: isolated populations of Cryptopygus sverdrupi (Collembola) among nunataks in the Sør Rondane Mountains, Dronning Maud Land, Antarctica

Molecular variation among Antarctic Collembola has been well appreciated over the last decade. The majority of studies have focussed on the Transantarctic Mountains and Antarctic Peninsula, and more recently Dronning Maud Land, which now accounts for all known continental species. Within most species, mean mitochondrial DNA (mtDNA) sequence divergence has not been more than around 2%, but in 2010 far greater levels of infraspecific sequence divergence (9.2–10.9%) were discovered in three species: Friesea grisea (10.2%), Gressittacantha terranova (10.4%) and Cryptopygus antarcticus (9.2%). Here, we present the first phylogeographic study on Cryptopygus sverdrupi from Dronning Maud Land. We found that mtDNA COI and 16S haplotypes clustered into two lineages with a mean COI sequence divergence of around 7.1%. The mixing of haplotypes between nearby nunataks separated by up to 15 km revealed support for ongoing (but rare) dispersal, although a single site, the most geographically isolated (by 40–58 km) was also the most genetically divergent. These levels of sequence divergence indicate persistence of biota throughout the Miocene and Pliocene isolated in glacial refugia. Expanding sampling of C. sverdrupi from additional ice-free refugia throughout Dronning Maud Land will be important to further our understanding of the evolutionary processes that have influenced the Antarctic continent, its landscape and biota.

Two kinorhynch species (Cyclorhagida, Echinoderidae, Echinoderes) show different distribution patterns across Tsugaru Strait, Northern Japan.

We investigated the geographic population structures of two intertidal kinorhynch species, Echinoderes sensibilis and Echinoderes sp. A, in the vicinity of Tsugaru Strait between Honshu and Hokkaido Islands, Japan, to examine whether the distribution or connectivity of populations of either species has been constrained by the strait. For each species, we examined the geographic distribution of COI haplotypes, constructed a median-joining haplotype network, and calculated statistics of genetic variation and connectivity. Tsugaru Strait is the northern range limit for E. sensibilis, which comprises a large, evolutionarily stable metapopulation that appears to have undergone a reduction in size followed by expansion; connectivity is low among most local populations, including across Tsugaru Strait. A divergent haplotype lineage showing no variation occurred only at Horozuki, suggesting recent immigration there from outside the study area. Echinoderes sp. A underwent a severe population bottleneck followed by rapid expansion. It occurred at all sampling sites on both sides of the strait, with high connectivity between populations across the strait. There is a zone of secondary contact between moderately divergent, presumably previously allopatric lineages in eastern Hokkaido. Present-day conditions in the strait have existed only for the past 8000 years, and differences in these species' distributions and apparent connectivity across the strait may relate to conditions existing in the strait when the species underwent population expansions or shifts in range; these historical events were not necessarily concurrent between the species, and occurred more than 8000 years ago. We discuss dispersal mechanisms for kinorhynchs, which could include suspension transport or rafting.

New genetic markers to identify European resistant abalone to vibriosis revealed by high-resolution melting analysis, a sensitive and fast approach

Increasing temperature of seawater is often associated with increased exposure incidence of disease in field and in aquaculture populations. Numerous episodic mass mortalities of the abalone Haliotis tuberculata have been observed along the northern Brittany coast of France caused by a complex interaction between the host, pathogen and environmental factors. Here, we evaluated the potential of high-resolution melting (HRM) analysis for mutation genotyping and development of genetic markers for resistance to vibriosis in the gastropod species H. tuberculata. Small amplicon assays were developed and revealed genetic polymorphism between surviving and susceptible abalone obtained after two successive infections of aquaculture families in controlled conditions. Together with specific COI haplotypes, we identified particular genotypes in nascent polypeptide-associated complex subunit alpha and ferritin genes linked to the susceptibility or resistance of abalone to vibriosis. Selection of genitors based on these genes may increase the proportion in offspring of resistant individuals of more than 76 %. Finally, HRM assays constitute a very efficient genotyping tool to validate the genetic markers on a representative number of individuals of wild populations and thus identify future resistant genitors for aquaculture or conservation purposes

DNA sequence information resolves taxonomic ambiguity of the common mud crab species (Genus Scylla) in Indian waters

For several years, mud crabs of genus Scylla have been misidentified owing to their high morphological plasticity and the absence of distinct morphological diagnostic characters. The taxonomic confusion of genus Scylla de Haan is considered to be a primary constraint to the development of aquaculture. Although genus Scylla was revised using morphological and genetic characteristics, taxonomy of Scylla species occurring in India is still not clear. In this study, partial sequences of two mitochondrial genes, 16S rRNA and CO1 (Cytochrome C oxidase subunit I) in populations of Scylla spp. obtained from eleven locations along the Indian coast were used to differentiate and resolve taxonomical ambiguity of the mud crab species in India. The sequences were compared with previously published sequences of Scylla spp. Both trees generated based on 16S rRNA and CO1 indicated that all S. tranquebarica morphotypes obtained during this study and S. tranquebarica sequences submitted previously from Indian waters reciprocally monophyletic with reference sequence of S. serrata. Both sequence data and morphological characters revealed that the species S. serrata (Forskal) is the most abundant followed by S. olivacea. Further, the 16S rRNA and COI haplotypes of Indian S. tranquebarica obtained in the study significantly differed with the known S. tranquebarica by 6.7% and 10.6% respectively whereas it differed with known S. serrata by 0.0–0.7% only, a difference that was not statistically significant. From these studies it is clear that “S. tranquebarica” commonly reported from India should be S. serrata (Forskal).

Morphological vs. molecular delineation of taxa across montane regions in Europe: the case study ofGammarus balcanicusSchäferna, (Crustacea: Amphipoda)

Mountainous areas are characterized by substantial biodiversity and endemicity due to their complex geological history and habitat fragmentation. Hence, it can be assumed that particularly high species richness can be found in organisms with limited dispersal capabilities that inhabit mountain streams. A number of scientific papers focus on molecular phylogeography or traditional taxonomy of species or species groups inhabiting such habitats. However, there is a lack of studies that integrate morphological and molecular data to identify and delineate cryptic species. For practical reasons, uncovering cryptic diversity is crucial in taxa used in biomonitoring. Distinct species, hard to separate based on morphology only, may have different tolerance ranges towards a variety of factors. Thus, our goal is to combine the two approaches to reveal potential patterns of diversification within a species widely distributed across European mountains: the amphipod crustacean Gammarus balcanicus. The data were obtained from 13 populations spread across the range of the species. Individuals were initially ascribed to G. balcanicus based on conventional fauna key morpho-anatomical diagnostic features and were further analysed for 23 additional features to explore any putative diversification. Morphometric data were analysed with use of the multiple correspondence analysis and anova. Molecular distances were calculated for 551-bp-long COI sequences. Test for isolation by distance was performed for both morphological and molecular data. The morphometric studies showed that some of the analysed features differed significantly between populations, although there was only a weak correlation between the morphological divergence and the between-population geographical distances. Moreover, high morphological diversity was present within sites. A set of 42 COI haplotypes was identified among the 135 individuals sequenced. No haplotype was shared among populations. The molecular p-distances within the nine localities presenting more than one haplotype were either almost null (ca. <0.003 for 7 localities) or relatively low (ca. 0.01–0.02 for 2 localities). In opposite, the molecular p-distances between localities were mostly at a high level (94% of pairwise comparisons being >0.14), similar as between other well-defined species of the genus Gammarus. Surprisingly, G. balcanicus appears to be polyphyletic based on topology of the neighbour-joining tree. The level of genetic distance between localities was not correlated with their geographical proximity. Globally, combining spatial patterns of morphological versus molecular divergence indicates a high level of cryptic diversity within a species conventionally defined based upon fauna key morphological features. In this context, the name G. balcanicus should be applied only to the population from locus typicus, while the other populations represent a number of putative distinct species. We may expect that such phenomenon would apply also to other animal taxa with conserved morphology, which are widespread over different mountain ranges in Europe.

Demographic history, marker variability and genetic differentiation in sandy beach fauna: What is the meaning of low FST's?

This note demonstrates the effect of locus variability and demographic history on the estimation of genetic differentiation and its interpretation in terms of ecological connectivity. Cytochrome c oxidase subunit I (COI, mtDNA) sequences of the beach clam Donax serra from four sites along the South African coast were analysed. D. serra showed low COI haplotype diversity (h = 0.30 ± 0.069, 7 haplotypes), suggesting expansion from a small source population into extant habitats. As a consequence, statistical power to measure genetic connectivity was low. The lack of genetic population structure therefore does not necessarily demonstrate high connectivity. Although COI has been used successfully to identify species and populations isolated for prolonged periods of time, lack of differentiation has to be interpreted with caution, especially in terms of extant patterns of connectivity.

Mitochondrial COI and morphological evidence for host specificity of the black cherry aphids Myzus cerasi (Fabricius, 1775) collected from different cherry tree species in Europe (Hemiptera, Aphididae)

Partial sequences of the mitochondrial COI gene of forty eight European and two Turkish population samples of Myzus cerasi from different winter hosts (Prunus spp.) were subjected to phylogenetic analyses. The analysed M. cerasi samples emerged as paraphyletic relative to a Myzus borealis sample used as an out-group, and formed two major clades in neighbor joining, maximum parsimony, maximum likelihood and Bayesian inference trees, corresponding to subspecies living specifically on Prunus avium and P. cerasus. Multivariate discriminant analysis (method of canonical variates) was applied to find out if morphological variation of samples correlated with mitochondrial COI and host plant information. Mean scores on the first two canonical variables clustered samples fully in accordance with their COI haplotypes and host plants confirming the existence of two morphologically similar winter host - specific subspecies of M. cerasi in Europe. No single morphological character enabled satisfactory discrimination between apterous viviparous females of the two subspecies. A three-character linear discriminant function enabled 92.37% correct identification of apterous viviparous females of M. cerasi cerasi (n = 118) and 93.64% of M. cerasi pruniavium (n = 110). A key for the morphological identification of the two subspecies is presented and their taxonomic status is discussed.

Molecular contribution to stock identification in the small-spotted catshark, Scyliorhinus canicula (Chondrichthyes, Scyliorhinidae)

The small-spotted catshark Scyliorhinus canicula is a small demersal chondrichthyan distributed on continental shelf and uppermost slope waters of the Mediterranean Sea and north eastern Atlantic Ocean. It has commercial value in some European regions, whereas in other it is considered a bycatch species. Species’ genetic structure was analysed by means of 578bp mitochondrial COI sequences. A total of 192 individuals (122 obtained in the present work and 70 retrieved from GenBank) from 11 Mediterranean and 1 Atlantic locations were considered. Overall, we detected 27 COI haplotypes, seven of which were newly found. Moreover, a high number of haplotypes were location- and/or region-private. Low values of nucleotide diversity (total π=0.0027) and moderate to high haplotype diversity (h=0.500–0.920, total h=0.827) were found. Significant genetic structuring in the study area was highlighted by AMOVA, Φ-statistics and Bayesian assignment analyses. The Atlantic sample was genetically divergent from Western Mediterranean counterparts and the Adriatic samples diverged from Eastern Mediterranean ones. Instead, Western and Eastern Mediterranean were not significantly divergent, suggesting that the Strait of Sicily is not effective in restricting past or current gene flow. No pattern of isolation by distance was detected. From a fisheries perspective, our results represent the first evidence of genetic structuring in S. canicula and are consistent with the presence of multiple genetic stocks in the study area. Further genetic analyses coupled with a fine grained sampling design are needed to precisely identify the borders of genetic stocks. These data provide a significant contribution for the planning of a long-term effective management policy, which could ensure sustainability of resource exploitation and stock viability.

Molecular and distribution data on the poorly known, elusive, cave mysid Harmelinella mariannae (Crustacea: Mysida)

AbstractMediterranean underwater marine caves harbour abundant populations of several species of mysids that are increasingly used as biological models in ecological and evolutionary studies. One exception is the species Harmelinella mariannae, described in 1989 and then hardly ever again reported in the literature. We here provide the first data on the distribution of this poorly known taxon that, contrary to expectations for a rare brooding cave dweller, we now report from Madeira Island in the nearby Atlantic, to the easternmost parts of the Mediterranean. Brief behavioural observations are added, particularly its atypical solitary habits and its feeding behaviour as a high trophic level carnivore. Molecular characterization of the different specimens captured provided three sorts of information. Mitochondrial COI and 16S haplotypes suggest different colonization waves in the Mediterranean, with one group in the Eastern Basin, two in the Marseille region in the NW part of this sea, and another group with a very wide extension from Madeira to Liguria and Malta. Mitochondrial data also support that one of the groups in Marseille might have diverged as a cryptic species of Harmelinella. 18S rRNA gene displays a single common sequence to all specimens from the four groups, and seems to confirm the original proposed placement of this taxon within the subfamily Heteromysinae, not Leptomysinae.

Colonisation and diversification of the Zenaida Dove (Zenaida aurita) in the Antilles: phylogeography, contemporary gene flow and morphological divergence.

Caribbean avifaunal biogeography has been mainly studied based on mitochondrial DNA. Here, we investigated both past and recent island differentiation and micro-evolutionary changes in the Zenaida Dove (Zenaida aurita) based on combined information from one mitochondrial (Cytochrome c Oxydase subunit I, COI) and 13 microsatellite markers and four morphological characters. This Caribbean endemic and abundant species has a large distribution, and two subspecies are supposed to occur: Z. a. zenaida in the Greater Antilles (GA) and Z. a. aurita in the Lesser Antilles (LA). Doves were sampled on two GA islands (Puerto Rico and the British Virgin Islands) and six LA islands (Saint Barthélemy, Guadeloupe, Les Saintes, Martinique, Saint Lucia and Barbados). Eleven COI haplotypes were observed that could be assembled in two distinct lineages, with six specific to GA, four to LA, the remaining one occurring in all islands. However, the level of divergence between those two lineages was too moderate to fully corroborate the existence of two subspecies. Colonisation of the studied islands appeared to be a recent process. However, both phenotypic and microsatellite data suggest that differentiation is already under way between all of them, partly associated with the existence of limited gene flow. No isolation by distance was observed. Differentiation for morphological traits was more pronounced than for neutral markers. These results suggest that despite recent colonisation, genetic drift and/or restricted gene flow are promoting differentiation for neutral markers. Variation in selective pressures between islands may explain the observed phenotypic differentiation.

Molecular Assessment of Commercial and Laboratory Stocks ofEiseniaSpp. (Oligochaeta: Lumbricidae) from South Africa

DNA barcoding was used to investigate laboratory and commercial stocks of Eisenia species from four provinces of South Africa. The COI gene was partially amplified and sequenced in selected earthworms from eight local populations (focal groups) and two European laboratory stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences generated. One of these haplotypes was found to belong to the megascolecid Perionyx excavatus. The remaining eight haplotypes belonged to the genus Eisenia, although only a single E. fetida haplotype, represented by six specimens, was found in one of the European populations. The other seven haplotypes, all occurring in South Africa, were E. andrei. One of the commercial stocks from South Africa and a laboratory culture from Europe were mixtures of E. andrei-P. excavatus and E. andrei-E. fetida, respectively. Previous allozyme studies have helped to suggest that some of the populations included in this study may be suffering from inbreeding depression, which could result in adverse consequences for both the vermiculture industry and ecotoxicological research in South Africa.

Cryptic species in the cosmopolitan Bugula neritina complex (Bryozoa, Cheilostomata)

Previous analyses of the mitochondrial gene cytochrome c oxidase subunit 1 (COI) and γ‐proteobacterial endosymbiont diversity have suggested that the marine bryozoan Bugula neritina is a complex of three cryptic species, namely Types S, D and N. Types D and N were previously reported to have restricted distributions along California (western USA) and Delaware and Connecticut (eastern USA), respectively, whereas Type S is considered widespread in tropical, subtropical and temperate regions due to anthropogenic transport. Here, Bayesian species delimitation analysis of a data set composed of two mitochondrial (COI and large ribosomal RNA subunit [16S]) and two nuclear genes (dynein light chain roadblock type‐2 protein [DYN] and voltage‐dependent anion‐selective channel protein [VDAC]) demonstrated that Types S, D and N correspond to three biological species. This finding was significantly supported, in spite of the combinations of priors applied for ancestral population size and root age. Furthermore, COI sequences were used to assess the introduction patterns of the cosmopolitan Type S species. Two COI haplotypes of Type S (S1a and S1d) were found occurring at a global scale. Mantel tests showed correlation between these haplotypes and local sea surface temperature tolerance. Accordingly, the distributions of Type S haplotypes may reflect intraspecific temperature tolerance variation, in addition to the role of introduction vectors. Finally, we show that the Type N may also have been introduced widely, as this species was found for the first time in Central California and north‐eastern Australia.

Inadequate taxonomy and highly divergent COI haplotypes in laboratory and field populations of earthworms used in ecotoxicology. A case study

DNA barcoding was used to investigate the phylogenetic delimitations of Eisenia sp. populations used in ecotoxicological research in South Africa. A total of three focal groups (used in published works) and two non-focal groups were assessed. These focal groups, including two laboratory cultures and one field population, have been referred to as Eisenia fetida in the literature. A previous molecular study had already helped to establish that one of the two laboratory groups was a population of E. fetida’s sister species E. andrei. In the present contribution, analyses of the COI gene revealed that the taxonomy of the remaining laboratory and field populations had also been incorrectly assigned since all the generated sequences grouped unequivocally with published sequences of E. andrei. Very high sequence divergence (>25% K2P) found within E. andrei could signal the occurrence of hitherto undescribed cryptic species. These findings are discussed with an emphasis on the possible consequences of using poorly identified earthworms or specimens with high molecular divergence in ecotoxicological bioassays. It is not clear whether unbeknownst to the researchers, the use of cryptic species in bioassays could jeopardise the quality of ecotoxicological investigations. Early evidence suggests that cryptic oligochaete species may respond differently to metal toxicity. The need for comparative ecotoxicological studies between E. andrei and E. fetidais also evidenced, especially in the light of recent numerous reports of cryptic oligochaete species. Ecotoxi-cologists are consequently encouraged, whenever possible, to make use of available genomic technologies to screen their laboratory stocks and available field populations for any molecular distinctiveness.

Systematics and Evolutionary History of Large Endemic Snails from the Caucasus (Helix buchiiandH. goderdziana) (Helicidae)

Two species of genus Helix Linnaeus, 1758 (Mollusca: Gastropoda: Helicidae) endemic to the Caucasus region are known from Georgia and northeastern Turkey: Helix buchii Dubois de Montpereux, 1839 and the recently-described but disputed Helix goderdziana Mumladze, Tarkhnishvili and Pokryszko, 2008. The latter species is the largest land snail throughout non-tropical Eurasia. We compared shell shapes and genital morphology of the two species. We analyzed mitochondrial COI and nuclear 18S ribosomal RNA and ITS1gene fragments in 39 specimens of H. buchii and H. goderdziana from ten locations from the entire distribution range of these species, together with 13 specimens of the widespread H. lucorum Linnaeus, 1758 and H. pomatia Linnaeus, 1758. Based on shell morphology alone, most of the individuals of the two species can be discriminated using multivariate approaches. The species have different flagellum/diverticulum ratios, and the foot coloration is a fully diagnostic morphological character. Molecular genetic analysis revealed little variation in 18S ITS1 fragment, and eleven COI haplotypes. Phylogenetic analyses support reciprocal monophyly of H. buchii and H. goderdziana. The genetic distances significantly correlate with the geographic and morphological distances; correlation of morphological distances with geography is insignificant. The basal lineages of both species are found within two distinct glacial refugia, a result which matches the separation of eastern and western evolutionary lineages of other relicts of the Western Caucasus. The present distribution of H. goderdziana coincides with the expected refugiai borders, whereas H. buchii is likely to have extended its geographical range since the last glaciation.

Molecular characterisation and infection dynamics of Dentitruncus truttae from trout (Salmo trutta and Oncorhynchus mykiss) in Krka River, Croatia

Dentitruncus truttae (Acanthocephala, Palaeacanthocephala) is an intestinal parasite of fish that can cause extensive damage to the host digestive tract, yet little is known about its epidemiology and genetic variability. It is a member of the Illiosentidae family with a worldwide distribution restricted to parts of southeast Europe. Its usual host is brown trout (Salmo trutta), but we report here the first detection in the intestine of rainbow trout (Oncorhynchus mykiss). We examined the physiology of D. truttae-infected S. trutta and O. mykiss, seasonal and spatial variability of D. truttae infections, and genetic variability of the parasite population in Krka River, Croatia. D. truttae was more abundant in both trout populations in the autumn, with no seasonal variation in prevalence. The parasite was more abundant in male than female trout (n=75, p<0.01). Analysis of the spatial distribution of the parasite across various sampling sites along the river showed the lowest prevalence and abundance of parasitic infections at the most downstream sampling site, which may reflect the predominance of female fish there and/or the smaller population of intermediate hosts. To provide the first molecular insights into D. truttae, we analysed sequences at three marker loci: the 18S rRNA gene, the cytochrome c oxidase subunit 1 (COI) gene and the internal transcribed spacer region. Phylogenetic analysis based on 18S rRNA confirmed the taxonomic grouping of D. truttae in the Illiosentidae family, first made more than 50 years ago based on morphology. The COI haplotype network did not show discrete genetic clusters corresponding to the different sampling sites, suggesting a stable population. These insights into D. truttae haplotype frequency distribution and intrapopulation genetic variation revealed minimal genetic variability, compared to the other acanthocephalan species.

Geographic structure with no evidence for host-associated lineages in European populations of Lysiphlebus testaceipes, an introduced biological control agent

Lysiphlebus testaceipes (Cress.) is an aphidiine parasitoid originally introduced to Europe as a biological control agent of citrus aphids in the Mediterranean. It has rapidly become widespread in coastal areas continuing gradually to expand inland. L. testaceipes exploited a large number of aphids in Europe, including new hosts and significantly changed the relative abundance of the native parasitoids. This behavior may reflect a broad oligophagy of the introduced parasitoid or it may require the evolution of host specialization that results in genetically differentiated subpopulations on different hosts. To address this issue we used the mitochondrial cytochrome oxidase subunit I and seven microsatellite loci to analyze the structure of genetic variation for L. testaceipes samples collected from 12 different aphid hosts across seven European countries, as well as some samples from Benin, Costa Rica, USA, Algeria and Libya for comparison. Only five COI haplotypes with moderate divergence were identified overall. There was no evidence for the association of haplotypes with different aphid hosts in the European samples, but there was geographic structuring in this variation. Haplotype diversity was highest in France, where L. testaceipes was introduced, but only a single haplotype was detected in areas of south-eastern Europe that were invaded subsequently. The analysis of microsatellite variation confirmed the lack of host-associated genetic structure, as well as differentiation between populations from south-western and south-eastern Europe. The parasitoid L. testaceipes in Europe is thus an opportunistic oligophagous species with a population structure shaped by the processes of introduction and expansion rather than by host exploitation.

Diversification of Fijian halictine bees: Insights into a recent island radiation

Although bees form a key pollinator suite for flowering plants, very few studies have examined the evolutionary radiation of non-domesticated bees over human time-scales. This is surprising given the importance of bees for crop pollination and the effect of humans in transforming ecosystems via agriculture. In the Pacific, where the bee fauna appears depauperate, their importance as pollinators is not clear, particularly in Fiji where species diversity is even lower than neighbouring archipelagos. Here we explore the radiation of halictine bees in Fiji using phylogenetic analyses of mtDNA COI sequence data. Our analyses indicate the existence of several ‘deep’ clades whose divergences are close to the crown node, along with a highly derived ‘broom’ clade showing very high haplotype diversity, and mostly limited to low-lying agricultural regions. This derived clade is very abundant, whereas the more basal clades were relatively rare. Although nearly all haplotype diversity in Fijian Homalictus comprises synonymous substitutions, a small number of amino acid changes are associated with the major clades, including the hyper-diverse clade. Analyses of haplotype lineage accumulation show a steep increase in selectively neutral COI haplotypes corresponding to the emergence of this ‘broom’ clade. We explore three possible scenarios for this dramatic increase: (i) a key change in adaptedness to the environment, (ii) a large-scale extinction event, or (iii) a dramatic increase in suitable habitats leading to rapid population expansion. Using estimated mutation rates of mitochondrial DNA in other invertebrates, we argue that Homalictus first colonised the Fijian archipelago in the middle–late Pleistocene, and the rapid accumulation of haplotypes in the hyper-diverse clade occurred in the Holocene, but prior to recorded human presence in the Fijian region. Our results indicate that bees have not been important pollinators of Fijian ecosystems until very recent times. Post-Pleistocene climate change and anthropogenic effects on Fijian ecosystems are likely to have greatly transformed pollinator suites from the conditions when those ecosystems were first being assembled.

Gene flow in the green mirid, Creontiades dilutus (Hemiptera: Miridae), across arid and agricultural environments with different host plant species

Creontiades dilutus (Stål), the green mirid, is a polyphagous herbivorous insect endemic to Australia. Although common in the arid interior of Australia and found on several native host plants that are spatially and temporally ephemeral, green mirids also reach pest levels on several crops in eastern Australia. These host-associated dynamics, distributed across a large geographic area, raise questions as to whether (1) seasonal fluctuations in population size result in genetic bottlenecks and drift, (2) arid and agricultural populations are genetically isolated, and (3) the use of different host plants results in genetic differentiation. We sequenced a mitochondrial COI fragment from individuals collected over 24 years and screened microsatellite variation from 32 populations across two seasons. The predominance of a single COI haplotype and negative Tajima D in samples from 2006/2007 fit with a population expansion model. In the older collections (1983 and 1993), a different haplotype is most prevalent, consistent with successive population contractions and expansions. Microsatellite data indicates recent migration between inland sites and coastal crops and admixture in several populations. Altogether, the data suggest that long-distance dispersal occurs between arid and agricultural regions, and this, together with fluctuations in population size, leads to temporally dynamic patterns of genetic differentiation. Host-associated differentiation is evident between mirids sampled from plants in the genus Cullen (Fabaceae), the primary host, and alternative host plant species growing nearby in arid regions. Our results highlight the importance of jointly assessing natural and agricultural environments in understanding the ecology of pest insects.

DNA-barcoding contradicts morphology in quill mite species Torotrogla merulae and T. rubeculi (Prostigmata: Syringophilidae)

Torotrogla merulae Skoracki, Dabert et Ehrnsberger, 2000 and T. rubeculi Skoracki, 2004 have been considered as distinct steno- and monoxenous quill mite species (Acari: Prostigmata: Syringophilidae) parasitizing the thrushes of the genus Turdus Linnaeus and the European robin Erithacus rubecula (Linnaeus), respectively. Morphological and molecular studies on the taxonomical status of these two species provided contradictory results. Well defined differences in morphology were not supported by substantial genetic distance in nucleotide sequences of the DNA barcode (mitochondrial cytochrome c oxidase subunit I, COI, and D2 domain of the nuclear 28S rRNA gene), by the topology of the phylogenetic trees (neighbor-joining, maximum parsimony, maximum likelihood) and the network analyses of the COI haplotype genealogy (median-joining, statistical parsimony) that reveal rubeculi populations nested within merulae haplotypes. Since detected differences between T. merulae and T. rubeculi populations (1.6-2.4% for COI and 0.1% for D2) are comparable to the intraspecific level observed in majority of currently recognized European Torotrogla species and are much lower than the interspecific distances observed in the genus, we postulate their conspecificity. Because main morphological distinctions concern the structures used for feeding, we hypothesize that they are the result of phenotypic plasticity evoked by specific and different environmental conditions prevailing on the host bodies (thickness of the feather quill wall).

Correction: male-killing Wolbachia and mitochondrial selective sweep in a migratory African insect

Following publication of our work (Graham and Wilson, BMC Evol Biol, 2012, 12:204), it was brought to our attention that seven of the mitochondrial COI haplotypes described in this manuscript as Spodoptera exempta haplotypes were in fact other species. As a result, we cannot now support one of our original conclusions suggesting that the Spodoptera genus was not monophyletic. However, it should be clearly stated that the main findings of the article, namely that the presence of three Wolbachia species appear to be driving a mitochondrial selective sweep within S. exempta, still holds true. Indeed, the new analysis strengthens the extent of the host mitochondrial skew (94.3% prevalence of haplo1).