Isozyme analysis at 24 loci was carried out on anisakid nematodes of the Anisakis simplex complex, recovered from various intermediate/paratenic (squid, fish) and definitive (marine mammals) hosts from various parts of the world. A number of samples were found to belong to A. simplex sensu stricto and Anisakis pegreffii, widely extending the geographic ranges and the number of hosts of these 2 species. In addition, a new distinct gene pool was detected, showing different alleles with respect to A. simplex s. str and A. pegreffii at 5 diagnostic loci (99% level). Samples with this gene pool were assigned to a new species, provisionally labeled A. simplex C. Reproductive isolation between A. simplex C and the other 2 Anisakis species was directly assessed by the lack of hybrid and recombinant genotypes in mixed samples from sympatric areas, i.e., Pacific Canada for A. simplex C+A. simplex s. str., South Africa and New Zealand for A. simplex C+A. pegreffii, even when such samples were recovered from the same individual host. Similar levels of genetic divergence were observed among the three species (DNei from 0.36 to 0.45). At the intraspecific level, Canadian Pacific and Austral populations of A. simplex C were found to be genetically rather differentiated from one another (average DNei = 0.08), contrasting with the remarkable genetic homogeneity detected within both A. simplex s. str. and A. pegreffii (average DNei about 0.01). Accordingly, a lower amount of gene flow was estimated within A. simplex C (Nm = 1.6) than within the other 2 species (Nm = 5.4 and 17.7, respectively). Anisakis simplex C showed the highest average values of genetic variability with respect to both A. simplex s. str. and A. pegreffii, e.g., expected mean heterozygosity. Hr = 0.23, 0.16, and 0.11, respectively, in the 3 species. Data on geographic distribution and hosts of the 3 members so far detected in the A. simplex complex are given. Their ecological niche is markedly differentiated, with a low proportion of hosts shared. Intermediate and definitive hosts of A. simplex s. str. and A. pegreffii appear to belong to distinct food webs, benthodemersal, and pelagic, respectively; this would lead to different transmission pathways for the parasites.

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Three taxa were detected by allozyme markers within the mealy aphids of the Hyalopterus pruni complex, having different cultivated Prunus species as main primary hosts. The genetically closer H. pruni and H. amygdali A (DNei= 0.10) never share primary hosts, whereas H. amygdali A and B (DNei= 0.32) may occasionally share them, producing few F1 hybrids. The three species proved reproductively isolated in the field, with no gene exchange. Their speciation seem to have occurred long before the agricultural revolution, crop colonization representing a host range expansion rather than a host shift, as in sympatric speciation.

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Discordance between mitochondrial and nuclear patterns of population genetic structure is providing key insights into the eco-evolutionary dynamics between and within species, and their assessment is highly relevant to biodiversity monitoring practices based on DNA barcoding approaches. Here, we investigate the population genetic structure of the fire salamander Salamandra salamandra in peninsular Italy. Both mitochondrial and nuclear markers clearly identified two main population groups. However, nuclear and mitochondrial zones of geographic transition between groups were located 600 km from one another. Recent population declines in central Italy partially erased the genetic imprints of past hybridization dynamics. However, the overall pattern of genetic variation, together with morphological and fossil data, suggest that a rampant mitochondrial introgression triggered the observed mitonuclear discordance, following a post-glacial secondary contact between lineages. Our results clearly show the major role played by reticulate evolution in shaping the structure of Salamandra salamandra populations and, together with similar findings in other regions of the species’ range, contribute to identify the fire salamander as a particularly intriguing case to investigate the complexity of mechanisms triggering patterns of mitonuclear discordance in animals.

No abstract

The hybrid origin of the western Mediterranean orchid Dactylorhiza insularis was demonstrated by genetic markers. Allozyme data showed that throughout its range I). insularis has an allotriploid constitution and reproduces apomictically. The parental species of D. insularis were identified as D. romana and D. sambucina; they contributed 2 alleles and 1 allele, respectively, at the allozyme loci studied. The maternal species of D. insularis was D. romana, as inferred from cpDNA (trnL(UAA) intron). High genetic similarities were found when comparing present populations of D. romana and D. sambucina with their respective genomes 'frozen' in D. insularis. Dactylorhiza insularis showed fixed (or nearly fixed) heterozygosity at 11 out of the 19 loci studied, and poor genetic variation: eight multilocus genotypes were detected at allozyme level. No multilocus genotype differs from the most similar one by more than one allele substitution. All D. insularis individuals showed the same cpDNA haplotype (I), regardless of their geographic origin and multilocus genotype. The I haplotype is similar, but not identical to that found in D. romana (R). No recurrent formation of D. insularis was observed in hybrid zones between D. romana and D. sambucina, where diploid sexual hybrids (F-1, F-n, backcrosses) were detected. Available data agree with a single origin for D. insularis, which possibly occurred in the present postglacial, when L). romana and D. sambucina, expanding from their glacial refugia, came into contact. The genetic homogeneity found between D. romana and D. markusii, both from their locus classicus, indicates that the latter is a junior synonym of D. romana; on the other hand, D. romana and D. sambucina are well differentiated species(D-Nei=0.59)

The Forest Dormouse (Dryomys nitedula) is a small rodent with a wide, albeit severely fragmented distribution, ranging from central Europe to central Asia. Within the Italian region, D. nitedula populations are restricted to forested mountain areas of two largely disconnected regions, the eastern Alps and the Calabria region, where two distinct subspecies (D. nitedula intermedius and D. nitedula aspromontis, respectively) have been described on the basis of phenotypic characters (i.e., fur colour). Here we analysed D. nitedula samples from both regions, to investigate patterns of genetic divergence and phylogenetic relationship among these two populations. Genetic variation was studied at the level of one mitochondrial (cytochrome b gene) and three nuclear gene fragments (exon1 of the interstitial retinoid-binding protein, exon 10 of the growth hormone receptor, and recombination activating gene 1). Phylogenetic analyses were performed using Maximum Likelihood and Bayesian inference methods. D. n. aspromontis and D. n. intermedius were found to be reciprocally monophyletic in all the phylogenetic analyses, and the genetic divergence observed between them at the mitochondrial CYTB gene was conspicuous (HKY: 0.044) when compared to previously observed values among many sister species of rodents. Our results clearly show that D. nitedula aspromontis is a deeply divergent, narrow endemic evolutionary lineage, and its conservation needs should be carefully evaluated in the near future. Moreover, such deep genetic divergence, together with phenotypic differentiation between D. n. intermedius and D. n. aspromontis, suggest that D. nitedula populations in southern Italy might belong to a distinct, previously unrecognized species.