Phylogenetic and Spatial Distribution of Evolutionary Isolation and Threat in Turtles and Crocodilians (Non-Avian Archosauromorphs)

Abstract

12The origin of turtles and crocodiles and their easily recognized body forms dates to the Triassic. 13Despite their long-term success, extant species diversity is low, and endangerment is extremely 14 high compared to other terrestrial vertebrate groups, with ~ 65% of ~25 crocodilian and ~360 15 turtle species now threatened by exploitation and habitat loss. Here, we combine available 16 molecular and morphological evidence with machine learning algorithms to present a 17 phylogenetically-informed, comprehensive assessment of diversification, threat status, and 18 evolutionary distinctiveness of all extant species. In contrast to other terrestrial vertebrates and 19 their own diversity in the fossil record, extant turtles and crocodilians have not experienced any 20 mass extinctions or shifts in diversification rate, or any significant jumps in rates of body-size 21 evolution over time. We predict threat for 114 as-yet unassessed or data-deficient species and 22 identify a concentration of threatened crocodile and turtle species in South and Southeast Asia, 23 western Africa, and the eastern Amazon. We find that unlike other terrestrial vertebrate 24 groups, extinction risk increases with evolutionary distinctiveness: a disproportionate amount 25 of phylogenetic diversity is concentrated in evolutionarily isolated, at-risk taxa, particularly 26 those with small geographic ranges. Our findings highlight the important role of geographic 27 determinants of extinction risk, particularly those resulting from anthropogenic habitat-28 disturbance, which affect species across body sizes and ecologies. 29

The Amazonian Red Side-Necked Turtle Rhinemys rufipes (Spix, 1824) (Testudines, Chelidae) Has a GSD Sex-Determining Mechanism with an Ancient XY Sex Microchromosome System

“…The side-necked turtles of the Chelidae family are phylogenetically related to Pelomedusidae (Africa) and Podocnemididae (Amazonia and Madagascar) turtle lineages, forming a monophyletic group (Pleurodira), predominantly widespread in the southern hemisphere [ 2 , 40 , 41 , 42 , 43 ]. Most Podocnemididae species (7 out of 8) exhibit 28 Mac , whereas Pelomedusidae species (for those with known karyotypes) present 34 and 36 chromosomes with the presence of Mac and mic [ 4 , 44 , 45 , 46 ].…”

“…Interestingly, as revealed here in our study, even with ancient origin, they can also be found practically intact in recent lineages, where the X and Y of R. rufipes are undistinguished from each other, with the Y sex chromosome being identified solely by comparative genomic hybridization and recruitment of several SSR motifs. The sex chromosomes may remain undifferentiated for many reasons, for example, transitions and turnovers involving XY and ZW, evolutionary advantages promoted by the recombination between XY and/or Z and W, as well as shifts involving autosomes [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , …”