Dataset Information

Mitochondrial DNA analysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia.

ABSTRACT: Identification of units within species worthy of separate management consideration is an important area within conservation. Mitochondrial DNA (mtDNA) surveys can potentially contribute to this by identifying phylogenetic and population structure below the species level. The American crocodile (Crocodylus acutus) is broadly distributed throughout the Neotropics. Its numbers have been reduced severely with the species threatened throughout much of its distribution. In Colombia, the release of individuals from commercial captive populations has emerged as a possible conservation strategy that could contribute to species recovery. However, no studies have addressed levels of genetic differentiation or diversity within C. acutus in Colombia, thus complicating conservation and management decisions. Here, sequence variation was studied in mtDNA cytochrome b and cytochrome oxidase I gene sequences in three Colombian captive populations of C. acutus. Two distinct lineages were identified: C. acutus-I, corresponding to haplotypes from Colombia and closely related Central American haplotypes; and C. acutus-II, corresponding to all remaining haplotypes from Colombia. Comparison with findings from other studies indicates the presence of a single "northern" lineage (corresponding to C. acutus-I) distributed from North America (southern Florida), through Central America and into northern South America. The absence of C. acutus-II haplotypes from North and Central America indicates that the C. acutus-II lineage probably represents a separate South American lineage. There appears to be sufficient divergence between lineages to suggest that they could represent two distinct evolutionary units. We suggest that this differentiation needs to be recognized for conservation purposes because it clearly contributes to the overall genetic diversity of the species. All Colombian captive populations included in this study contained a mixture of representatives of both lineages. As such, we recommend against the use of captive-bred individuals for conservation strategies until further genetic information is available.

SUBMITTER: Bloor P

PROVIDER: S-EPMC4298440 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Mitochondrial DNA analysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia.

Bloor Paul P Ibáñez Carolina C Viloria-Lagares Thomas A TA

Ecology and evolution 20141208 1

Identification of units within species worthy of separate management consideration is an important area within conservation. Mitochondrial DNA (mtDNA) surveys can potentially contribute to this by identifying phylogenetic and population structure below the species level. The American crocodile (Crocodylus acutus) is broadly distributed throughout the Neotropics. Its numbers have been reduced severely with the species threatened throughout much of its distribution. In Colombia, the release of ind ...[more]

PMID: 25628870

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Project description:Four species of true crocodile (genus Crocodylus) have been described from the Americas. Three of these crocodile species exhibit non-overlapping distributions-Crocodylus intermedius in South America, C. moreletii along the Caribbean coast of Mesoamerica, and C. rhombifer confined to Cuba. The fourth, C. acutus, is narrowly sympatric with each of the other three species. In this study, we sampled 113 crocodiles across Crocodylus populations in Cuba, as well as exemplar populations in Belize and Florida (USA), and sequenced three regions of the mitochondrial genome (D-loop, cytochrome b, cytochrome oxidase I; 3,626 base pair long dataset) that overlapped with published data previously collected from Colombia, Jamaica, and the Cayman Islands. Phylogenetic analyses of these data revealed two, paraphyletic lineages of C. acutus. One lineage, found in the continental Americas, is the sister taxon to C. intermedius, while the Greater Antillean lineage is most closely related to C. rhombifer. In addition to the paraphyly of the two C. acutus lineages, we recovered a 5.4% estimate of Tamura-Nei genetic divergence between the Antillean and continental clades. The reconstructed paraphyly, distinct phylogenetic affinities and high genetic divergence between Antillean and continental C. acutus populations are consistent with interspecific differentiation within the genus and suggest that the current taxon recognized as C. acutus is more likely a complex of cryptic species warranting a reassessment of current taxonomy. Moreover, the inclusion, for the first time, of samples from the western population of the American crocodile in Cuba revealed evidence for continental mtDNA haplotypes in the Antilles, suggesting this area may constitute a transition zone between distinct lineages of C. acutus. Further study using nuclear character data is warranted to more fully characterize this cryptic diversity, resolve taxonomic uncertainty, and inform conservation planning in this system.

Project description:The American crocodile (Crocodylus acutus) is considered a vulnerable species by the International Union for Conservation of Nature (IUCN) Red List across its range and classified as locally threatened in several countries. There is a lack of knowledge involving hematological and physiological parameters in American crocodile populations, limiting our understanding of what are considered "normal" blood analyte results for the species and how to link them with health assessments. In this study, we analyzed 40 hematological and biochemical parameters and estimated reference intervals (RIs) for 35 of them based on 436 clinically healthy wild American crocodiles caught in South Florida between 2015 and 2021. Crocodiles were captured across three areas with different levels of human influence [low = Everglades National Park (ENP), medium = Biscayne Bay Estuary (BBE), and high = Turkey Point Nuclear Power Plant (TP)]. There was very strong-to-strong evidence for an effect of where animals were caught on five analytes: basophils %, phosphorus, proportion of (pr) alpha-2 globulins, absolute count (abs) of gamma globulins, and corticosterone, so no reference values were estimated but general statistics are presented and discussed. From the remaining analytes, we found no evidence that sex or size class had an effect on red blood cell (RBC), azurophils and monocytes abs, triglycerides, and albumin abs. However, we did find moderate-to-strong evidence that sex influenced azurophils % and size class influenced white blood cell (WBC), heterophils %, monocytes %, basophils abs, creatine phosphokinase (CPK), potassium, glucose, bile acids, alpha-1 globulin abs, and alpha-2 globulin pr and abs. Finally, there was strong evidence that both sex and size class influenced PCV, lymphocytes % and abs, eosinophils % and abs, aspartate aminotransferase (AST), calcium, sodium, chloride, total protein, albumin/globulin (A/G) ratio, albumin pr, alpha-1 globulin, and beta globulin abs. Intraspecific analysis showed that size is the variable that most influenced analytes explaining up to 29% of the variation, which relates to our findings based on intraindividual analysis. We compared our results with blood parameters reported for conspecifics as well as closely related species and discussed implication of those results for clinical diagnosis and American crocodile conservation.

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Dataset Information

Mitochondrial DNA analysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia.

Publications

Mitochondrial DNA analysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia.

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