Evolutionary Significant Units within Populations of Neotropical Broad-Snouted Caimans ( Caiman latirostris , Daudin, 1802)

Global conservation prioritization areas in three dimensions of crocodilian diversity

Crocodilians are a taxonomic group of large predators with important ecological and evolutionary benefits for ecosystem functioning in the face of global change. Anthropogenic actions affect negatively crocodilians' survival and more than half of the species are threatened with extinction worldwide. Here, we map and explore three dimensions of crocodilian diversity on a global scale. To highlight the ecological importance of crocodilians, we correlate the spatial distribution of species with the ecosystem services of nutrient retention in the world. We calculate the effectiveness of global protected networks in safeguarding crocodilian species and provide three prioritization models for conservation planning. Our results show the main hotspots of ecological and evolutionary values are in southern North, Central and South America, west-central Africa, northeastern India, and southeastern Asia. African species have the highest correlation to nutrient retention patterns. Twenty-five percent of the world's crocodilian species are not significantly represented in the existing protected area networks. The most alarming cases are reported in northeastern India, eastern China, and west-central Africa, which include threatened species with low or non-significant representation in the protected area networks. Our highest conservation prioritization model targets southern North America, east-central Central America, northern South America, west-central Africa, northeastern India, eastern China, southern Laos, Cambodia, and some points in southeastern Asia. Our research provides a global prioritization scheme to protect multiple dimensions of crocodilian diversity for achieving effective conservation outcomes.

Phylogeographical analysis and phylogenetic inference based on the cytochrome b gene in the genus Caiman (Crocodylia: Alligatoridae) in Central and South America

The genus Caiman is one of the most taxonomically conflicted among crocodilians. Caiman crocodilus has four subspecies: Caiman crocodilus crocodilus, Caiman crocodilus fuscus, Caiman crocodilus chiapasius and Caiman crocodilus apaporiensis, but some studies recognize Caiman yacare as a subspecies of C. crocodilus or as a C. crocodilus–C. yacare complex. In Argentina, Caiman latirostris and C. yacare are present and included in sustainable use programmes, although they have hardly been studied at the genetic level. The present study had two main objectives: (1) to study the genetic diversity, structure and phylogeny of C. yacare and C. latirostris in Argentina; and (2) to perform a phylogenetic analysis of the genus Caiman throughout its entire distribution. The results show high haplotype diversity for both species but low nucleotide diversity for C. latirostris. Phylogenetic analysis shows a clear separation between both species but, surprisingly, a well-differentiated clade belonging to the Chaco region was observed. The phylogenetic analysis exhibited clades made up of the sequences of each Caiman species, with some inconsistencies: in the clade of C. crocodilus, one sequence of C. yacare is included, and one clade is observed including sequences from C. c. fuscus and C. c. chiapasius. These data indicate the need to undertake interdisciplinary studies to clarify the taxonomic status of these crocodilian species.

A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity

Dramatic early Cenozoic climatic shifts resulted in faunal reorganization on a global scale. Among vertebrates, multiple groups of mammals (e.g., adapiform and omomyiform primates, mesonychids, taeniodonts, dichobunid artiodactyls) are well known from the Western Interior of North America in the warm, greenhouse conditions of the early Eocene, but a dramatic drop in the diversity of these groups, along with the introduction of more dry-tolerant taxa, occurred near the Eocene–Oligocene boundary. Crocodyliforms underwent a striking loss of diversity at this time as well. Pre-Uintan crocodyliform assemblages in the central Western Interior are characterized by multiple taxa, whereas Chadronian assemblages are depauperate with only Alligator prenasalis previously known. Crocodyliform diversity through the intervening Uintan and Duchesnean is not well understood. The middle Eocene Devil’s Graveyard Formation (DGF) of southwest Texas provides new data from southern latitudes during that crucial period. A new specimen from the middle member of the DGF (late Uintan–Duchesnean) is the most complete cranial material of an alligatorid known from Paleogene deposits outside the Western Interior. We identify this specimen as a caimanine based on notched descending laminae of the pterygoids posterior to the choanae and long descending processes of the exoccipitals that are in contact with the basioccipital tubera. Unlike Eocaiman cavernensis, the anterior palatine process is rounded rather than quadrangular. The relationships and age of this new taxon support the hypothesis that the modern distribution of caimanines represents a contraction of a more expansive early Cenozoic distribution. We hypothesize that the range of caimanines tracked shifting warm, humid climatic conditions that contracted latitudinally toward the hothouse-icehouse transition later in the Eocene.

Modern cryptic species and crocodylian diversity in the fossil record

Advances in molecular biology and genetics are revealing that many recognized crocodylian species are complexes of two or more cryptic species. These discoveries will have a profound impact on interpretation of the crocodyliform fossil record. Our understanding of ranges of intraspecific variation in modern crocodylian morphology may be based on multiple species and thus express both intraspecific and interspecific variation. This raises questions about our ability to recognize modern species in the fossil record, and it also indicates that specimens from disparate localities or horizons may represent not single widespread species, but multiple related species. Ranges of variation in modern species require a thorough re-evaluation, and we may have to revisit previous perceptions of past crocodyliform diversity, rates of evolution or anagenetic lineages in stratigraphic succession. These challenges will not be unique to those studying crocodyliforms and will require sophisticated approaches to variation among modern and fossil specimens.