| Alytes obstetricans lusitanicus Ambu, Martínez-Solano & Dufresnes, 2024 photo: Christophe Dufresnes |
Abstract
The mapping, delimiting and naming of biodiversity forge the links between academic research, conservation efforts and communication about wildlife. Midwife toads from the subgenus Alytes are a group of high conservation concern widely popular among European naturalists, but for which the taxonomy remains unsettled. Six phylogeographic lineages that diversified during the Pliocene and the Pleistocene epochs have been identified and delimited in two species (A. obstetricans and A. almogavarii), but only five subspecies are presently recognized (A. o. obstetricans, A. o. pertinax and A. o. boscai; A. a. almogavarii and A. a. inigoi). Accordingly, two distinct lineages found in northwestern and western Iberia are still regrouped under the same taxon A. o. boscai. Contrary to the discordant findings of earlier studies based on a few genes, phylogenomic analyses of thousands of nuclear markers have confirmed their independent evolution, estimated to exceed two million years. In this article, we detail molecular, morphological and behavioral variation in the subgenus Alytes to provide a taxonomic description for the previously unnamed western Iberian lineage. Like other taxa of this subgenus, the new taxon is supported by robust evidence for genetic divergence despite little external differentiation. It is designated as a subspecies of A. obstetricans, as per its phylogenetic placement and young evolutionary age, which compares to freely admixing Alytes subspecies. Combining genetic barcoding and distribution information, we provisionally define its range in central Portugal and western central Spain, and prompt to evaluate its potentially worrisome conservation status. Our study highlights how phylogeographic diversity can be acknowledged in zoological systematics, even when phenotypic differences are subtle, and illustrates the advantages of genomic approaches to overcome the limitations of single-gene analyses when implementing taxonomic revisions.
Keywords: Alytes obstetricans; Iberian Peninsula; integrative taxonomy; species delimitation
| The holotype MNCN 50839 of Alytes obstetricans lusitanicus ssp. nov., depicted live photo: Christophe Dufresnes |
Alytes obstetricans lusitanicus ssp. nov.
Diagnosis: A midwife toad from the subgenus Alytes, which becomes the fourth subspecies of A.
obstetricans. According to phylogenomic analyses, A. o. lusitanicus ssp. nov. is the sister
taxon of A. o. boscai, from which it diverged around the Plio-Pleistocene transition ca. 2.5
Mya (Ambu et al. 2023). It features 0.19 % of sequence divergence at ~ 282 kb of nuclear
(RAD) loci from that subspecies. The mitochondrial diversity of A. o. lusitanicus ssp. nov. is
counter-intuitive. The Spanish populations feature a “ghost” lineage different from the regular
A. o. lusitanicus ssp. nov. mtDNA predominantly found in Portugal (Ambu 2024b).
Accordingly, the mtDNA of A. o. lusitanicus ssp. nov. differs from the mtDNA of A. o.
boscai by 0.93 % (Portuguese lineage) or 0.99 % (Spanish ghost lineage) at 16S, and by 5.2
% (Portuguese lineage) or 3.3 % (Spanish ghost lineage) at ND4 (Table 1) – again noting that
these mtDNA distances do not reflect the true divergence between taxa due to a past
mitochondrial capture in A. o. boscai (Ambu et al. 2023). According to MOLD, the new
subspecies can be distinguished from all other taxa from subgenus Alytes by the following
diagnostic nucleotides in the ND4 gene ...
Etymology: The nomen lusitanicus refers to the ancient Roman Province of Lusitania, which encompassed central and southern Portugal (south of the Douro River) and western central Spain (Extremadura, Castilla la Mancha and Castilla y León), thus broadly matching the distribution of the new taxon.
Johanna Ambu, ĺñigo Martínez-Solano, Christophe Dufresnes. 2024. A New Subspecies of Midwife Toad (Anura, Alytidae, Alytes Wagler, 1829) supported by Genomic Taxonomy. Alytes. 2024, 41 (1–4): 18–39. biotaxa.org/Alytes/article/view/85334