Primo dato genetico per il fratino (Charadrius alexandrinus) in Italia e confronto su scala continentale

The Kentish Plover (Charadrius alexandrinus, Charadriformes) is a shorebird with a huge range including beaches and salt pans across northern temperate to subtropical latitudes of Europe, Asia, and Africa. In the last decades, the availability of breeding sites for this species has been greatly reduced through direct destruction or functional loss of dune areas due to a remarkable expansion of coastal tourism. Altogether this has often prevented the Kentish Plover from settling along the shore and, wherever possible, its reproductive success has in any case been negatively impacted by human disturbance. In Italy, the species is in sharp decline and reported as Endangered in the national Red List of vertebrates. Three well-established nuclei are known in Tuscany, with one occurring in the municipality of Castagneto Carducci (Province of Livorno). In this area, after a strong storm a cracked egg was recovered in 2020 on the beach of the Special Area of Conservation/Special Protection Area Padule di Bolgheri. A 523 bp-long fragment of the mitochondrial DNA Control Region was amplified by PCR. The sequence was aligned with those available (n = 198) in the GenBank (i) to determine relationships between the Italian representative and conspecifics from the entire range based on both their geographical origin and affiliation to mainland/island populations, (ii) to identify genetically homogeneous clusters, and (iii) to test a hypothesis of sudden demographic expansion across the entire range of the species. Overall, the haplotypic diversity (h) was 0.86 ± 0.02 while the nucleotide diversity (π, %) was 0.46 ± 0.28, with the island populations holding higher values than the mainland ones (except Azores: h = 0.12 ± 0.11, π = 0.24 ± 0.43). Thirty-five (e.g., Taiwan, 8; Ukraine, 7; Russia, 5) over a total of 47 haplotypes (H) turned out to be private, while all the remaining ones were shared by several populations. Of these, two (H3, H14) showed up with a remarkably high frequency (18.5% and 31.6%, respectively): H3 occurred almost exclusively in Europe while H14 across the whole Eurasia (more to the East than to the West). The Median Joining network reflected a double-star structure with most of the haplotypes being a single-mutational step away from H3 and H14, a pattern that did not change when the birds from the mainland and island populations were investigated separately. The single Italian representative was assigned to H3 as well as most of the individuals from the Iberian Peninsula and Macaronesia. The Analysis of the Molecular Variance indicated that the 25.53% of the genetic diversity was partitioned among populations and the 74.47% among individuals within populations (φST = 0.25; P < 0.001). The values of Fs and D statistics of Fu’s and Tajima tests were - 26.782 (P < 0.001) and 1.680 (P = 0.016), respectively, and the curve of Mismatch Distribution showed a markedly unimodal trend (Harpending index: r = 0.027, P = 0.45). Therefore, the hypothesis of a sudden demographic expansion across the whole species’ range could not be rejected. A Bayesian clustering analysis of the 199 investigated sequences pointed to the occurrence of three genetic groups. Clusters 1 (red, n = 86; mean membership value, 0.43) and 3 (green, n = 83, with the Italian representative: mean membership value, 0.46) occurred mostly across Europe and in the eastern part of the species’ range, respectively, whereas cluster 2 (yellow, n = 30: mean membership value, 0.11) included birds from Cape Verde, Russia, and the United Arab Emirates. However, these groups did not reflect a significant spatial genetic structure across the Kentish Plover’s range, thus confirming the well-known high levels of intraspecific gene flow. In conclusion, while this study provided the first contribution to the knowledge of genetic relationships of the Italian Kentish Plover population, a national scale investigation of this species to draw up more adequately informed conservation strategies cannot be delayed any longer.