Pheidole pallidula (Nylander, 1849)

Schär, Sämi, Menchetti, Mattia, Schifani, Enrico, Hinojosa, Joan Carles, Platania, Leonardo, Dapporto, Leonardo & Vila, Roger, 2020, Integrative biodiversity inventory of ants from a Sicilian archipelago reveals high diversity on young volcanic islands (Hymenoptera: Formicidae), Organisms Diversity & Evolution (New York, N. Y.) 20 (3), pp. 405-416 : 413

Pheidole pallidula

The maximal divergence of intraspecific mtDNA found within this taxon (12.4% within greater Sicily and 12.2% within the Aeolian archipelago) is unmatched by any other taxon investigated here ( Table 2, Figs. 2 and 4). Three highly derived mitochondrial lineages were found, one of which only on Filicudi and another one on both Stromboli and Vulcano. The third deep lineage was collected in Milazzo ( Fig. 2 ). Finding such a high divergence of mtDNA barcodes within a species is uncommon. Double peaks or stop codons, which are typical of numts, were not found in these sequences. Sometimes such findings are suggestive of cryptic species, hybridization/introgression or populations separated by large geographical distances ( Hosoishi and Ogata 2019). Remarkably, the distinct mitochondrial lineages of P. pallidula identified here occur in a geographically very small area, situated as little as 30 km from each other ( Fig. 1 ). Furthermore, we did not observe any particular morphological or ecological differences between them (ESM 1). The hypothesis that P. pallidula contains cryptic species has already been raised by a very detailed morphometric study (Seifert 2016). However, the latter work suggests relatively clear geographic separation of the proposed four cryptic taxa, with the only geographical area of co-occurrence being the Eastern Mediterranean. In the reference area of Sicily and the Aeolian Islands, only the type form (type locality: Messina) should theoretically occur (Seifert 2016). Alternatively, the deep lineages may be explained by some of the processes already discussed above. Thus, the study of nuclear markers is required to assess the implications of our findings in mtDNA.

Figures

Fig. 2 Maximum likelihood tree of 143 DNA barcodes belonging to 44 ant taxa. The scale bar indicates the number of changes per site. The colours given at nodes show % node support from 1000 bootstrap replicates.

Fig. 1 Map of the sampling locations for the specimens used in this study.