Deep Interisland Genetic Divergence in the Macaronesian Endemic Mosquito Ochlerotatus eatoni (Diptera: Culicidae), Indication of Cryptic Species.

Ochlerotatus eatoni (Edwards, 1916) is a species endemic to Canary and Madeira Islands that, based on morphology, is considered to be single species. Mitochondrial 16S rRNA and cytochrome oxidase I (COI) sequence data demonstrate that the populations from Tenerife and Madeira Islands are highly differentiated (F(ST) = 0.93). The phylogenetic analysis also separates the two populations into two highly distinct groups. The sharp mitochondrial genetic differentiation between islands is congruent with the published nuclear (allozyme) data. However, mtDNA data did not reveal any significant genetic differentiation within islands. Extreme interisland genetic divergence, but lack of morphological variation, is indicative of the existence of cryptic species. I suggest the elevation of populations to at least incipient species status, designating the populations from Tenerife and Madeira Islands as Oc. eatoni. hewitti and Oc. eatoni. krimbasi, respectively.

Endohelminth parasites of the blacktail comber Serranus atricauda (Pisces: Serranidae), from Madeira Archipelago (Atlantic Ocean).

Four different endohelminth parasite taxa were found in the viscera of the blacktail comber Serranus atricauda Günther, 1874 caught in the Madeira Archipelago. Nematodes were the dominant group, represented by 2 different taxa, Hysterothylacium spp. Ward & Magath, 1917 and Procamallanus (Spirocamallanus) halitrophus Fusco & Overstreet, 1978 comb. n. Plerocerci of the trypanorhynch Pseudogrillotia epinepheli (synonym: Grillotia epinepheli) Scholz, Garippa & Scala, 1993, and cystacanths of the acanthocephalan Bolbosoma vasculosum Rudolphi, 1819 were found in the visceral cavity. New host records for P. (S.) halitrophus and P. epinepheli and the extension of the geographic distribution of these 2 parasite species provide evidence of parasite transference between the Madeira Archipelago, the Mediterranean and the Gulf of Mexico. The paucity of the parasite fauna of blacktail comber reflect a combination of fish host selective feeding on particular dietary items and its territorial behaviour.

Genetic exchange versus genetic differentiation in a medium-sized inversion of Drosophila: the A2/Ast arrangements of Drosophila subobscura.

Chromosomal inversion polymorphism affects nucleotide variation at loci associated with inversions. In Drosophila subobscura, a species with a rich chromosomal inversion polymorphism and the largest recombinational map so far reported in the Drosophila genus, extensive genetic structure of nucleotide variation was detected in the segment affected by the O(3) inversion, a moderately sized inversion at Muller's element E. Indeed, a strong genetic differentiation all over O(3) and no evidence of a higher genetic exchange in the center of the inversion than at breakpoints were detected. In order to ascertain, whether other polymorphic and differently sized inversions of D. subobscura also exhibited a strong genetic structure, nucleotide variation in 5 gene regions (P236, P275, P150, Sxl, and P125) located along the A(2) inversion was analyzed in A(st) and A(2) chromosomes of D. subobscura. A(2) is a medium-sized inversion at Muller's element A and forms a single inversion loop in heterokaryotypes. The lower level of variation in A(2) relative to A(st) and the significant excess of low-frequency variants at polymorphic sites indicate that nucleotide variation at A(2) is not at mutation-drift equilibrium. The closest region to an inversion breakpoint, P236, exhibits the highest level of genetic differentiation (F(ST)) and of linkage disequilibrium (LD) between arrangements and variants at nucleotide polymorphic sites. The remaining 4 regions show a higher level of genetic exchange between A(2) and A(st) chromosomes than P236, as revealed by F(ST) and LD estimates. However, significant genetic differentiation between the A(st) and A(2) arrangements was detected not only at P236 but also in the other 4 regions separated from the nearest breakpoint by 1.2-2.9 Mb. Therefore, the extent of genetic exchange between arrangements has not been high enough to homogenize nucleotide variation in the center of the A(2) inversion. A(2) can be considered a typical successful inversion of D. subobscura according to its relative length. Chromosomal inversion polymorphism of D. subobscura might thus cause the genome of this species to be highly structured and to harbor different gene pools that might contribute to maintain adaptations to particular environments.

Wolbachia (Alphaproteobacteria: Rickettsiales) Infections in Isolated Aphid Populations from Oceanic Islands of the Azores Archipelago: Revisiting the Supergroups M and N.

Aphids (Hemiptera: Aphididae) have provided a suitable model to study endosymbionts, their community, and dynamics since the discovery of the obligate endosymbiont Buchnera aphidicola in these organisms. In previous studies, Wolbachia was found in some aphid species. In the present study, we report the prevalence of Wolbachia in aphids sampled from a geographically isolated region (Azores Islands), aiming at a better understanding and characterization of the two newly reported supergroups, M and N. The description of the supergroup M was based on 16S rRNA as well as some protein-coding genes. However, the assignment of the supergroup N was according to 16S rRNA gene sequences of a very few samples. We collected aphid samples and performed phylogenetic analysis of 16S rRNA gene as well as four protein-coding genes (gatB, ftsZ, coxA, and hcpA). The results demonstrate that the 16S rRNA gene data can unambiguously assign the strain supergroup and that the two supergroups, N and M, are equally prevalent in Azorean aphids. The available sequence data for the protein-coding markers can identify supergroup M but the status of supergroup N is inconclusive, requiring further studies. The data suggest that horizontal transmission of Wolbachia (Hertig and Wolbach) between two phylogenetically distant aphid species cohabiting the same plant host.

Population genetics of Ochlerotatus eatoni (Diptera: Culicidae) endemic species to two Macaronesian Islands.

Analyses of 11 isoenzyme loci of Ochlerotatus eatoni (Edwards, 1916), endemic to two Macaronesian Islands (Madeira and Tenerife, Canary Islands), revealed substantial genetic structure in the study populations. Samples from sites on the south and north of Madeira displayed a significant reduction of variability compared with those from central Madeira and Tenerife. The Tenerife population exhibited a severe deficit of heterozygosity with similar magnitude across all the loci examined. The complex pattern of variation in Oc. eatoni is because of interplay of breeding structure, genetic drift, and geographical and historical factors. From these findings, we concluded that island colonization by Oc. eatoni was not marked by founder effect.

Larval cestodes infecting the deep-water fish, Cataetyx laticeps (Pisces: Bythitidae) from Madeira Archipelago, Atlantic Ocean.

Parasites of deep-water fishes are less known in comparison to the parasites of fishes living in the demersal and epipelagic ocean zones. In the present research note we report the occurrence of larval trypanorhynch cestodes in a rare deep-water fish, the deep-water brotula, Cataetyx laticeps. Based on the 28S rDNA (region D1-D3) sequence homology and the phylogenetic analysis, the larval cestodes are putatively assigned to the genus Grillotia. It is suggested that the definitive host of this trypanorhynch is a batoid.