Population genetics and molecular identification of Crocodylus acutus and C. moreletii (Crocodilia: Crocodylidae) in captive and wildlife populations / Genética de poblaciones e identificación molecular de Crocodylus acutus y C. moreletii (Crocodilia: Crocodylidae) en poblaciones de cautiverio y de vida libre

Abstract Introduction: There is low evidence of genetic diversity and hybridization processes within Crocodylus acutus and C. moreletii populations. Objetive: To evaluate genetic diversity and some phylogenetic relationships in wild and captive populations of C. acutus and C. moreletii using the Barcode of Life Data System (COX1, cytochrome C oxidase subunit 1 gene). Methods: 28 individuals phenotypically like C. acutus located in the state of Guerrero, Oaxaca and Quintana Roo were sampled, as well as animals belonging to C. moreletii located in the states of Tabasco, Campeche, and Quintana Roo. 641 base pairs of nucleotide sequence from COX1 were used to obtain the haplotype and nucleotide diversity per population, and a phylogenetic and network analysis was performed. Results: Evidence of hybridization was found by observing C. moreletti haplotypes in animals phenotypically determined as C. acutus, as well as C. acutus haplotypes in animals classified as C. moreletti. Low haplotypic diversity was observed for C. acutus (0.455 ± 0.123) and for C. moreletii (0.505 ± 0.158). A phylogenetic tree was obtained in which the sequences of C. acutus and C. moreletii were grouped into two well-defined clades. Organisms identified phenotypically as C. acutus but with C. moreletii genes were separated into a different clade within the clade of C. moreletii. Conclusions: There are reproductive individuals with haplotypes different from those of the species. This study provides a small but significant advance in the genetic knowledge of both crocodile species and the use of mitochondrial markers, which in this case, the COX1 gene allowed the detection of hybrid organisms in wild and captive populations. Conservation efforts for both species of crocodiles should prevent the crossing of both threatened species and should require the genetic identification of pure populations, to design effective conservation strategies considering the possibility of natural hybridization in areas of sympatry.

Resumen Introducción: Existe poca evidencia de la diversidad genética y los procesos de hibridación dentro de las poblaciones de Crocodylus acutus y C. moreletii. Objetivo: Evaluar la diversidad genética y algunas relaciones filogenéticas en poblaciones silvestres y cautivas de C. acutus y C. moreletii utilizando el Sistema de Código de Barras de la vida (COX1, subunidad I del gen del citocromo C oxidasa). Métodos: Se muestrearon 28 individuos fenotípicamente similares a C. acutus ubicados en los estados de Guerrero, Oaxaca y Quintana Roo, así como animales pertenecientes a C. moreletii ubicados en los estados de Tabasco, Campeche y Quintana Roo. Se utilizaron 641 pares de bases de la secuencia de nucleótidos de la subunidad I del gen del citocromo C oxidasa para obtener el haplotipo y la diversidad de nucleótidos por población, y se realizó un análisis filogenético y de redes. Resultados: Se encontró evidencia de hibridación al observar haplotipos de C. moreletti en animales determinados fenotípicamente como C. acutus, así como haplotipos de C. acutus en animales clasificados como C. moreletti. Se observó una baja diversidad haplotípica para C. acutus (0.455 ± 0.123) y para C. moreletii (0.505 ± 0.158). Se obtuvo un árbol filogenético en el que las secuencias propias de C. acutus y C. moreletii se agruparon en dos grandes y bien definidos clados. Los organismos identificados fenotípicamente como C. acutus pero con genes de C. moreletii se separaron en un clado diferente dentro del clado de C. moreletii. Conclusiones: Existen individuos reproductores con haplotipos diferentes a los de la especie. Este estudio aporta un pequeño pero significativo avance en el conocimiento genético tanto de las especies de cocodrilos como del uso de marcadores mitocondriales, que, en este caso, el gen COX1 permitió la detección de organismos híbridos en poblaciones silvestres y cautivas. Los esfuerzos de conservación para ambas especies de cocodrilos deben evitar el cruce de ambas especies amenazadas y deben requerir la identificación genética de poblaciones puras, para diseñar estrategias de conservación efectivas considerando la posibilidad de hibridación natural en áreas de simpatría.

Variabilidad genética de poblaciones en cautiverio de Crocodylus moreletii (Crocodylia: Crocodylidae) mediante el uso de marcadores microsatelitales / Genetic variability in captive populations of Crocodylus moreletii (Crocodylia: Crocodylidae) using microsatellites markers

Genetic variability in captive populations of Crocodylus moreletii (Crocodylia: Crocodylidae) using microsatellites markers. Crocodylus moreletii, an extinction threatened species, represents an emblem for tropical ecosystems in Mexico. Surprisingly, there is a lack of information about their genetic constitution, which should be evaluated for a proper management ex situ and for making decisions on the release of crocodiles into natural habitats. The aim of this study was to characterize and compare the genetic variability of four populations of C. moreletii (two wild versus two born ex situ). Through PCR were amplified seven microsatellite polymorphic loci, however a heterozygote deficit, diminished by the presence of null alleles, was found in the populations (average H O=0.02). The AMOVA indicated that the highest proportion of genetic variability is within populations, and a limited genetic differentiation among populations (average F ST=0.03), probably due to high inbreeding index (average F IS=0.97). When comparing the genetic variability between and within other crocodilian species, we found that in C. moreletii is well below those reported. We concluded that the limited genetic variability in ex situ born populations is probably due to a founder effect derived from the social structure of their progenitors, and by the bottleneck effect, inferred by the limited effective population size, that historically characterizes their natural distribution in wild populations.

Crocodylus moreletii representa un emblema para los ecosistemas tropicales de México pero actualmente está amenazada por extinción. Sorprendentemente, hay una falta de información de su constitución genética, que debe ser evaluada para un manejo apropiado ex situ y para toma de decisiones en la liberación de cocodrilos a su hábitat natural. El objetivo del estudio fue caracterizar y comparar la variabilidad genética de cuatro grupos poblacionales de C. moreletii (dos silvestres y dos nacidas ex situ). Mediante PCR se amplificaron siete loci de microsatélites polimórficos, sin embargo se encontró déficit de heterocigotos en las poblaciones (promedio H O=0.02) mermado por la presencia de alelos nulos. El AMOVA indicó que la mayor proporción de variabilidad genética se encuentra dentro de las poblaciones y una limitada diferenciación genética entre poblaciones (promedio F ST =0.03), probablemente debida al alto índice de endogamia (promedio F IS=0.97). Al comparar la variabilidad genética inter e intra especies de cocodrilianos, encontramos que en C. moreletii está muy por debajo de los reportados. Se concluye que la limitada variabilidad genética de las poblaciones nacidas ex situ probablemente se debe al efecto fundador derivado de la estructura social de sus progenitores, y de las poblaciones silvestres, por el efecto cuello de botella, inferido por el limitado tamaño efectivo de población que presentó históricamente en su distribución natural.

Variación genética y flujo de genes entre poblaciones de Crocodylus acutus (Crocodylia: Crocodylidae) en tres ríos del Pacífico Central, Costa Rica

The crocodylid Crocodylus acutus is found in the Central Pacific of Costa Rica only in small populations, and the species is protected by law. RAPD was used to analyze 70 DNA samples of Crocodylus acutus from the rivers Jesus Maria, Tarcoles and Tusubres in the Central Pacific of Costa Rica in order to estimate genetic diversity, differentiation among populations, gene flow and genetic distance between them. Genetic diversity was low in the three rivers, H = 0.2201 in the Jesus Maria river, 0.2358 in the Tarcoles river and 0.2589 in the Tusubres river. Among the three populations there is a metapopulational dynamic (GST = 0.0367), mainly between the populations of the Jesus Maria and Tarcoles rivers. The value of gene flow (Nm = 13.1361) and the number of individuals reported for each river in 2004 suggests that the population of the Tarcoles river is the source and those from Jesus Maria and Tusubres are the drains. There was a direct relationship between the genetic distance and the geographical distance (z =1.1449, r =0.9731, p< 0.0010). A conservation strategy for these crocodiles must consider the existence of the metapopulation between the three rivers and the importance of studying the genetics of the American Crocodile in the rest of the Pacific coast of Costa Rica, as well as over the entire distribution range of this species. Rev. Biol. Trop. 56 (3): 1471-1480. Epub 2008 September 30.

Se utilizó la técnica de ADN Polimórfico Amplificado al Azar (RAPD) para analizar muestras de ADN de 70 individuos de C. acutus provenientes de los ríos Jesús María, Tárcoles y Tusubres en el Pacífico Central de Costa Rica para estimar la diversidad genética, la diferenciación entre poblaciones, el flujo genético y la distancia genética. La diversidad genética fue baja en los tres ríos H = 0.2201 en el río Jesús María, 0.2358 en el río Tárcoles y 0.2589 en el río Tusubres. La diversidad genética para el total de los individuos también fue baja, H = 0.2452. Entre las tres poblaciones hay una dinámica metapoblacional (G ST = 0.0367) principalmente en las poblaciones de los ríos Jesús María y Tárcoles. El valor de flujo genético (Nm = 13.1361) y el número de individuos registrado para cada río por Porras (2004) sugieren que la población del río Tárcoles está cumpliendo el papel de fuente y las de Jesús María y Tusubres constituyen los sumideros. Hubo relación directa entre la distancia genética y la distancia geográfica (z = 1.1449, r = 0.9731, p< 0.0010). Estos resultados indican la necesidad de diseñar una estrategia para la conservación de estos cocodrilos que considere la existencia de la metapoblación entre los tres ríos y también es importante realizar un estudio genético en el resto de la costa Pacífica del Costa Rica y en todo el ámbito de distribución de esta especie.

Cross-species microsatellite amplification in South American Caimans ( Caiman spp and Paleosuchus palpebrosus )

Microsatellite DNA markers have been used to assess genetic diversity and to study ecological behavioral characteristics in animals. Although these markers are powerful tools, their development is labor intensive and costly. Thus, before new markers are developed it is important to prospect the use of markers from related species. In the present study we investigated the possibility of using microsatellite markers developed for Alligator mississipiensis and Caiman latirostris in South American crocodilians. Our results demonstrate the use of microsatellite markers for Paleosuchus palpebrosus, Caiman crocodilus and Caiman yacare.

Population genetic analysis of Caiman crocodilus (Linnaeus, 1758) from South America

The genetic structure of Caiman crocodilus was investigated using a 1085 bp mtDNA fragment of the cytochrome b gene. Inferences were based on 125 individuals from nine localities in Peru, Brazil and French Guiana. With the exception of Mamirauá Lake, Anavilhanas Archipelago and the Tapará Community which show a signal of demographic expansion, the sampled localities are in a mutation-drift genetic equilibrium. Divergence between the Amazon basin and extra-Amazon basin localities is significant; however, inference from Nested Clade Analysis cannot distinguish between continuous range expansion, long distance colonization or past fragmentation; however, past fragmentation is unlikely due to low number of mutational steps separating these two regions. The divergence is probably maintained by the reduced ability of C. crocodilus to cross salt water barriers. Within the Amazon basin, continuous range expansion without isolation-by-distance is the most likely process causing genetic structuring. The observed genetic patterns are compatible with the ecology of C. crocodilus, and history of human exploitation. As commercial hunting depleted more valuable species, C. crocodilus expanded its range and ecological niche, prompting hunters to harvest it. Following a period of intense hunting, C. crocodilus is now experiencing recovery and a second population expansion especially in protected areas.

Biometria, hematologia e genética de Ciman Latirostris (Daudin, 1801) na Região de Bauru (SP) / Biometry, hematology and genetic of the Caiman Latirstris (Daudin, 1801) in Bauru (SP)

O jacaré de papo amarelo (Caiman latirostris) representa a única espécie de crocodiliano cuja distribuição geográfica abrange o Estado de São Paulo. É um animal importante na manutenção de nossos ecossistemas aquáticos, daí a necessidade de através do conhecimento gerado por intermédio da pesquisa científica, preservá-lo. Neste trabalho, foram determinados parâmetros biométricos externos hematólogicos de 22 espécimes e caracterização o padrão eletroforético dashemoglobinas. Em relação à biometria, foram obtidas 2 medidas de comprimento co´rpóreo e 8 medidas de comprimento da cabeça dos animais.