Phylogenetic relationships and biogeography of midwife toads (Discoglossidae: Alytes)

Abstract

Aim To devise a robust phylogenetic hypothesis for midwife toads (Alytes: Anura: Discoglossidae) and to discuss its implications for the reconstruction of the biogeographical history of the group. Location Western Palearctic. Methods Analysis of sequences of mitochondrial DNA (cytochrome b and 16S RNA, 861 bp) and 29 characters of cranial osteology of all species and subspecies within Alytes. Results Phylogenetic analyses support a sister group relationship between Alytes dickhilleni and A. muletensis, and of this clade with A. maurus. The monophyly of A. obstetricans is controversial; in particular, the phylogenetic position of A. obstetricans almogavarii is uncertain. The estimated dates for the cladogenetic events within Alytes are congruent with those derived from independent analyses (allozymes), except for the differentiation of A. o. almogavarii and the split between A. dickhilleni and A. muletensis. Main conclusions The phylogeny based on the analysis of morphological and mtDNA data differs from previous hypotheses in the positions of A. o. almogavarii and A. maurus. Events associated with the radiation of Alytes are the formation of large inland saline lakes in Iberia c. 16 Ma and the 11 ° C dramatic decrease in average annual temperature during the Middle–Late Badenian transition c. 14–13.5 Ma (A.cisternasii vs. the ancestor of the remaining clades), the structuring of the Neo‐Pyrenees and the reopening of the Betic Strait c. 10–8 Ma(A. o. almogavarii vs. A. obstetricans and vs. the subgenus Baleaphryne), the opening of the Gibraltar Strait at the end of the Messinian Salinity Crisis at c. 5.3 Ma (A. maurus vs. the ancestor of the A. dickhilleni A. muletensis clade) and a transmarine colonization event at c. 3 Ma (the ancestor of A. muletensis vs. A. dickhilleni). Following the new hypothesis, A. maurus, previously considered a subspecies of A. obstetricans, deserves species status. Second, A. o. almogavarii is a well‐differentiated lineage that was isolated from other A. obstetricans more than c. 5 Ma, but later lost its genetic and specific identity following secondary contact, hybridization and introgression with the main stock. The presence of a marked morphological and genetic diversity within A. obstetricans renders reconstruction of the evolutionary history of the genus more complicated than previously appreciated.

The rediscovered Hula painted frog is a living fossil

“…This is in full agreement with a previous time-tree analysis of Alytes, which inferred a diversification of the A. dickhillenii/maurus/muletensis clade between 2.7 and 5.6 mya 36 . We therefore constrained the divergence between the two transMediterranean pairs of sister species, each with lower bounds of 5 mya and higher bounds of 7 mya (ACR) and with a normal prior at 5 mya with 2 mya s.d.…”

β-fibrinogen intron 7 variation in Discoglossus (Anura: Discoglossidae): implications for the taxonomic assessment of morphologically cryptic species

“…Additionally, Gonçalves et al (2007) found significant levels of variation at both intra-and interspecific levels in the 634 bp-long sequences of midwife toads (Alytes) analyzed in their study. Pairwise Kimura-2 parameter-corrected genetic distances between species pairs in Alytes are 2.5 to 7.6 times higher in mtDNA (cob, data from Martínez-Solano et al, 2004) than in β-fibint7 (Gonçalves et al, 2007), and the corresponding values in Discoglossus are similar, 3.7-5 times higher in mtDNA than in β-fibint7 (this study).…”

Diversity and conservation of Algerian amphibian assemblages

“…BUSACK (1986), for example, demonstrated significant differences in genetic distances between some species considered vicariant from one side to the other of the Strait of Gibraltar. Other workers (ARANO et al, 1998;CARRANZA & WADE, 2004;FROMHAGE et al, 2004;MARTÍNEZ-SOLANO et al, 2004;VEITH et al, 2004) have also discovered genetic discontinuities of the same order of magnitude. BARBADILLO et al (1997), and later CARRANZA & WADE (2004) and PAULO et al (2008), presented very convincing hypotheses based on fragmentation of basal populations, before and during the Messinian Crisis, to explain discontinuities.…”

“…Each of these islands could, over a long period of time, harbour isolated populations of amphibians currently represented in the region by allopatric species. ARANO et al (1998), CARRANZA & ARNOLD (2004), FROMHAGE et al (2004, MARTÍNEZ-SOLANO et al (2004), andRECUERO et al (2007) have described genetic discontinuity considered appropriate for supporting taxonomic changes among North-African amphibians in the genera Pelophylax, Alytes, Discoglossus, Pleurodeles, and Hyla. Mountainous massifs of Edough, connected for a few thousand years to the mainland, remained totally isolated over a period of several millions of years and represent the last of the islands of the Alkapeca complex; the newt from Edough represents one additional example of allopatric speciation (CARRANZA & ARNOLD, 2004;CARRANZA & WADE, 2004).…”