Analysis of mitochondrial COI sequences of the Diachasmimorpha longicaudata (Hymenoptera: Braconidae) species complex in Thailand

Diachasmimorpha longicaudata is an Opiinae parasitoid used to control tephritid fruit flies, which cause tremendous economic losses of fruits worldwide. In Thailand, D. longicaudata is classified as three sibling species, DLA, DLB and DLBB, based on the morphological and biological species concepts but their genetic variation has not been studied. Therefore, we investigated the genetic differentiation of the mitochondrial COI gene to clarify the ambiguous taxonomy of this species complex. The 603‐bp COI region was sequenced from laboratory‐bred colonies and field‐collected specimens from seven locations representing five geographical regions in Thailand. DLA was associated with the host Bactrocera correcta while DLB and DLBB were associated with Bactrocera dorsalis. The interspecific nucleotide differences of COI sequences among the three groups ranged from 6.70% to 7.62% (Kimura 2‐parameter distance), which adequately separates species complexes within the order Hymenoptera and supports the current sibling species classification. The neighbor joining, maximum likelihood and consensus Bayesian phylogenetic trees constructed from COI sequences revealed that the three sibling species of laboratory and field‐collected D. longicaudata are monophyletic with 100% support. The high genetic variation and molecular phylogeny of the COI sequences were shown to discriminate between the D. longicaudata species examined in this study.     

A distinct group of north European Aedes vexans as determined by mitochondrial and nuclear markers

The floodwater mosquito Aedes (Aedimorphus) vexans (Meigen, 1830) (Diptera: Culicidae) is common in several areas of Sweden and is predicted to become more abundant in the wake of expected changes in precipitation and temperature caused by climate change. As well as being a nuisance, Ae. vexans can act as a vector of over 30 viruses. In the event of an outbreak of disease caused by a vector‐borne virus, knowledge of the distribution, population structure and intermixing of populations from different locations will help direct resources to target locations to prevent spread of the pathogen. The present study analysed individual Ae. vexans from eight locations throughout Sweden. Based on the mitochondrial cytochrome oxidase I (COI) marker, a subset of the analysed mosquitoes cluster apart from the other samples. Similarly, two nuclear loci were sequenced and the same phylogenetic structure observed. These results indicate that this group represents a reproductively isolated population among Ae. vexans. Comparisons with COI sequences held in the Barcode of Life Database (BoLD) for Ae. vexans from around the world show that specimens collected in Belgium and Estonia group together with the Swedish group, suggesting that this genotype is present throughout northern Europe. These results suggest there is a cryptic taxonomic unit related to Ae. vexans in northern Europe.     

Molecular identification and phylogenetic relationships of Coleoidea (Mollusca: Cephalopoda) from the Persian Gulf and Oman Sea reveals a case of cryptic diversity

The Persian Gulf and Oman Sea constitute one of the most important marine ecosystems and have many economically important aquatic species, including several coleoid cephalopods. Some coleoids are difficult to identify using traditional morphological characteristics. In this study, two mitochondrial fragments, cytochrome oxidase I (COI) and the large ribosomal subunit (16S rRNA), were used for identification of coleoid species in four regions in the northern Persian Gulf and Oman Sea. The study led to the identification of potential cryptic species of Sepia, Amphioctopus and Uroteuthis. Furthermore, Euprymna hyllebergi was reported for the first time from the Persian Gulf. A high diversity of Coeloidea was found in the study area. Mean intraspecific and interspecific nucleotide distances for COI were 0%–2% and 2%–7%, respectively, while these values for 16S rRNA sequences were 0%–1% and 1%–4%. Given the uncertainty about species identity and the high levels of intraspecific genetic diversity reported for some species in GenBank, a comprehensive global study will be needed to resolve the taxonomic status of several coleoid species.     

Molecular identification of schistosome intermediate hosts: case studies of Bulinus forskalii group species (Gastropoda: Planorbidae) from Central and East Africa

African freshwater snails of the genus Bulinus act as intermediate hosts for schistosomes, trematode parasites responsible for medical and veterinary forms of schistosomiasis. The relationship between these snails and their parasites is an intricate one, with particular species of snail susceptible to infection only by certain species of schistosome. In common with other self-fertile hermaphrodite gastropods, Bulinus consists of a number of closely related species complexes with restricted gene flow between populations of each taxon. Consequently, despite their medical and veterinary importance as intermediate hosts, unambiguous identification and differentiation of planorbid snails such as these remains problematic, often confounding attempts to define the distribution and evolutionary relationships of conchologically similar taxa. Here we consider how morphological methods of discrimination can be used in conjunction with molecular based approaches to improve snail identification, thereby achieving a better understanding of the epidemiology of schistosomiasis. Data are presented from Central and East African taxa which illustrate how PCR-based methods have begun to be used in combination with traditional analyses in an integrated approach to characterize the genus Bulinus , specifically the B. forskalii species group. Particular emphasis is given to the analyses of Random Amplified Polymorphic DNA (RAPDs) and the mitochondrial gene cytochrome oxidase I (COI).     

Population genetic structure of two water strider species in the Ecuadorian Amazon

1. We used mtDNA sequence variation to estimate population genetic structure between and among water strider populations of Potamobates williamsi and P . sumaco in the Ecuadorian Amazon.
2. Sequencing of the COI mitochondrial gene revealed 16 haplotypes, which were summarised into four haplotype groups. P . williamsi and P . sumaco shared two common and widespread haplotypes.
3. Population structure was moderate and gene flow was low. Both air and river distances were significantly correlated with gene flow and, thus, indicative of isolation by distance.
4. The genetic structure within and among populations of P. williamsi and P. sumaco was probably not influenced by the dynamic tropical lotic system.     

The impact of redefined species limits in Palame (Coleoptera: Cerambycidae: Lamiinae: Acanthocinini) on assessments of host, seasonal, and stratum specificity

Assumptions about the host and stratum specificity of tropical insects are routinely incorporated into estimates of global species richness, but few empirical studies reliably assess tropical insect specificity. In French Guiana, cerambycid beetles in the genus Palame reproduce exclusively in trees belonging to the Brazil nut family (Lecythidaceae). During a year-long rearing project, Palame anceps (Bates) emerged exclusively from a single host species, but P. crassimana Bates and P. mimetica Monné appeared to make seasonal changes in host affiliation. In the case of P. crassimana , dry season specimens could be distinguished from rainy season specimens by subtle differences in pubescence, but it was difficult to find diagnostic morphological characters supporting their delimitation as separate species. In order to detect genetic differentiation in Palame , 1049 bp of mitochondrial DNA (COI gene) were sequenced. The three nominal species of Palame yielded six haplotype groups, with sequence divergences among groups ranging from 8.27 to 17.56%. Species with apparent seasonal changes in host use included multiple distinct haplotype groups that I interpret to represent multiple species-level taxa. Insects considered generalized owing to temporal or geographical changes in host association may, with improved resolution in species limits, prove to be assemblages including relatively specialized cryptic species. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 195–209.     

Polymorphism of axillary bud galls induced by Rhopalomyia longitubifex (Diptera: Cecidomyiidae) on Artemisia princeps and A. montana (Asteraceae) in Japan and Korea, with designation of new synonyms

In the past, Rhopalomyia longitubifex, Rhopalomyia shinjii, and Rhopalomyia sp. (Diptera: Cecidomyiidae) have been regarded as independent species based on differences in the sizes and shapes of axillary bud galls induced on Artemisia montana (Asteraceae) in Japan and A. princeps in Japan and Korea. However, comparison of morphological features and molecular sequencing data indicate that these Rhopalomyia gall midges are identical and that the differences in gall shape are polymorphisms, although the measurements of gall height and diameter overlap slightly. This finding suggests that although galls have frequently been regarded as extensions of the phenotype of a species, differences in gall shape may not always be reliable for identifying gall‐inducing cecidomyiids. The older name, R. longitubifex, is applied to these gall midges, and the names that were applied to this species on later occasions are revised or synonymized. The mature and immature stages of R. longitubifex are redescribed and information on the distribution, host range, and gall size of this species is provided. We also discuss the role of gall polymorphism in the early stages of speciation.     

Systematic position of the pelagic Thecosomata and Gymnosomata within Opisthobranchia (Mollusca, Gastropoda) – revival of the Pteropoda

The complete 18S (SSU) rRNA as well partial 28S (LSU) rRNA and partial mitochondrial COI sequences have been used to reconstruct the phylogenetic relationships within Opisthobranchia with special focus on the pelagic orders Thecosomata and Gymnosomata. Maximum parsimony, maximum likelihood, distance as well as Bayesian analysis of a combined dataset of the three genes reveals that Thecosomata and Gymnosomata are sister groups and together are closely related to Anaspidea. Possible sister taxon to Thecosomata, Gymnosomata and Anaspidea is Cephalaspidea s. str . Analysis of a taxon-extended dataset of partial 28S sequences supported a basal position of Limacina within Euthecosomata. Within Cavolinidae, Creseis is basal to the other taxa. Other phylogenetic implications from the present results are also discussed. Investigation of the morphology and histology of Thecosomata and Gymnosomata as well as several other opisthobranch taxa helped to identify autapomorphies for Thecosomata and Gymnosomata as well as apomorphies for the clades including these taxa.     

A mitochondrial phylogeography of Brachidontes variabilis (Bivalvia: Mytilidae) reveals three cryptic species

This study examined genetic variation across the range of Brachidontes variabilis to produce a molecular phylogeography. Neighbour joining (NJ), minimum evolution (ME) and maximum parsimony (MP) trees based on partial mitochondrial DNA sequences of 16S-rDNA and cytochrome oxidase (COI) genes revealed three monophyletic clades: (1) Brachidontes pharaonis s.l. from the Mediterranean Sea and the Red Sea; (2) B. variabilis from the Indian Ocean; (3) B. variabilis from the western Pacific Ocean. Although the three clades have never been differentiated by malacologists employing conventional morphological keys, they should be ascribed to the taxonomic rank of species. The nucleotide divergences between Brachidontes lineages (between 10.3% and 23.2%) were substantially higher than the divergence between congeneric Mytilus species (2.3–6.7%) and corresponded to interspecific divergences found in other bivalvia, indicating that they should be considered three different species. Analysis of the 16S-rDNA sequences revealed heteroplasmy, indicating dual uniparental inheritance (DUI) of mtDNA in the species of Brachidontes collected in the Indian Ocean, but not in the species in the Pacific nor in the species in the Red Sea and the Mediterranean Sea. When we employed the conventional estimate of the rate of mitochondrial sequence divergence (2% per million years), the divergence times for the three monophyletic lineages were 6–11 Myr for the Indian Ocean and Pacific Ocean Brachidontes sp. and 6.5–9 Myr for the Red Sea and Indian Ocean Brachidontes sp . Thus, these species diverged from one another during the Miocene (23.8–5.3 Myr). We infer that a common ancestor of the three Brachidontes species probably had an Indo-Pacific distribution and that vicariance events, linked to Pleistocene glaciations first and then to the opening of the Red Sea, produced three monophyletic lineages.