Diversity of North American map and sawback turtles (Testudines: Emydidae: Graptemys)

Abstract

Map turtles of the genus Graptemys are native to North America, where a high degree of drainage endemism is believed to have shaped current diversity. With 14 species and one additional subspecies, Graptemys represents the most diverse genus in the family Emydidae. While some Graptemys species are characterized by pronounced morphological differences, previous phylogenetic analyses have failed yet to confirm significant levels of genetic divergence for many taxa. As a consequence, it has been debated whether Graptemys is taxonomically inflated or whether the low genetic divergence observed reflects recent radiations or ancient hybridization. In this study, we analysed three mt DNA blocks (3228 bp) as well as 12 nuclear loci (7844 bp) of 89 specimens covering all species and subspecies of Graptemys . Our analyses of the concatenated mt DNA sequences reveal that the widespread G. geographica constitutes the sister taxon of all other Graptemys species. These correspond to two clades, one comprised of all broadheaded Graptemys species and another clade containing the narrow-headed species. Most species of the broad-headed clade are reciprocally monophyletic, except for G. gibbonsi and G. pearlensis , which are not differentiated. By contrast, in the narrow-headed clade, many currently recognized species are not monophyletic and divergence is significantly less pronounced. Haplotype networks of phased nuclear loci show low genetic divergence among taxa and many shared haplotypes. Principal component analyses using coded phased nuclear DNA sequences revealed eight distinct clusters within Graptemys that partially conflict with the terminal mt DNA clades. This might be explained by malemediated gene flow across drainage basins and female philopatry within drainage basins. Our results support that Graptemys is taxonomically oversplit and needs to be revised.

Phylogenetic and spatial distribution of evolutionary diversification, isolation, and threat in turtles and crocodilians (non-avian archosauromorphs)

“…For instance, [ 65 ] showed that the eight traditionally recognized species of Pseudemys reduced to only three species-level lineages in their molecular analyses. Similarly, [ 72 ] showed that the 14 currently recognized species of Graptemys, long noted for their low levels of molecular divergence [ 95 ], appeared to represent eight or nine species-level lineages at most. These findings were confirmed [ 73 ] by authors who nevertheless continued to recognize 14 species.…”

A new slider turtle (Testudines: Emydidae: Deirochelyinae:Trachemys) from the late Hemphillian (late Miocene/early Pliocene) of eastern Tennessee and the evolution of the deirochelyines

“…1–5). In a recent study on the intrageneric phylogenetic relationships of Graptemys based on molecular data, Praschag et al (2017 , fig. 2) found Graptemys geographica as sister to two main clades, including one with mainly “broad-headed” species and one with “narrow-headed” species.…”

“…Indeed, most previous studies that have looked at the intrageneric relationships of Graptemys have found G. geographica as sister to other Graptemys species ( McKown, 1972 ; Lamb et al, 1994 ; Lamb & Osentoski, 1997 ; Stephens & Wiens, 2003 ; Wiens, Kuczynski & Stephens, 2010 ). Praschag et al (2017) determined Graptemys was taxonomically oversplit and suggested revision of its species was needed, particularly members of their “narrow-headed” species group. The present study uses a member of their broad-headed group ( Graptemys barbouri ) and a member of their narrow-headed group ( Graptemys pseudogeographica ), along with G. geographica .…”

In quest of contact: phylogeography of helmeted terrapins (Pelomedusa galeata,P. subrufasensu stricto)

“…One locus, the intron 1 of the RNA fingerprint protein 35 gene (R35) has been previously shown to be species-diagnostic for P. galeata and P. subrufa ( Vargas-Ramírez et al, 2010 ). The other locus, including coding and non-coding parts of the ornithine decarboxylase gene (ODC), is relatively variable in chelonians ( Fritz et al, 2012 ; Praschag et al, 2017 ) and therefore looked promising to be also species-specific. Laboratory procedures for the nuclear loci followed Praschag et al (2017) except that we applied newly designed internal primers for sequencing the R35 gene (forward: GCAAGGAAAAATGTTTG, reverse: ACGCTGACTCCATGCACA).…”