Genetic Diversity and Population Genetics in Crocodilian Species

Crocodilian species, including true crocodiles, alligators, caimans and gharials, exhibit a complex tapestry of genetic variation shaped by evolutionary history, habitat fragmentation and human intervention. Studies employ mitochondrial markers and nuclear microsatellites to quantify heterozygosity, allelic richness and effective population size, revealing both deep phylogeographic splits and recent connectivity driven by dispersal corridors. Hybridisation events, whether ancient or recent, have produced cases of introgression that challenge species boundaries and complicate management strategies. Conservation programmes rely increasingly on genetic assessments to guide reintroduction, translocation and captive‐breeding initiatives, aiming to maintain adaptive potential in the face of environmental change. Metapopulation dynamics have been documented in isolated desert populations and major riverine systems, emphasising the role of seasonal waterways in sustaining genetic flow. As genome‐scale approaches become more accessible, comparative linkage maps and single‐nucleotide polymorphism panels promise finer resolution of adaptive loci and demographic history. Integrating molecular data with ecological modelling and long‐term monitoring underpins robust conservation units, ensuring that global crocodilian diversity is preserved for future generations.

Research from Nature Portfolio

Recent studies have assessed the genetic status of key crocodylian populations under active management regimes. In a tropical river sanctuary, population surveys and microsatellite analysis revealed that the generalist mugger (Crocodylus palustris) has rapidly colonised protected stretches, displaying moderate genetic diversity that exceeds that of the resident specialist gharial. Such findings underscore the need for adaptive management to mitigate interspecific competition and secure long‐term recovery of specialist taxa. In another case, managed populations of the critically endangered gharial (Gavialis gangeticus) were shown to harbour low allelic richness and heterozygosity, with bottleneck signatures in both major breeding rivers. This work highlights the urgency of expanding genetic monitoring into wild and captive stocks to inform future translocation and genetic rescue strategies.

Genetic Diversity and Population Genetics in Crocodilian Species publication trend

The graph below shows the total number of articles in genetic diversity and population genetics in crocodilian species across all publications each year (not limited to Nature Index journals).

Technical terms

Microsatellite marker: Short tandem repeats in nuclear DNA used to assess genetic variation and relatedness.

Mitochondrial control region (D‐loop): Non‐coding mtDNA segment with high mutation rate, informative for population history.

Heterozygosity: Proportion of individuals carrying two different alleles at a given locus.

Allelic richness: Number of distinct alleles present in a population, standardised for sample size.

Effective population size (Ne): The number of breeding individuals contributing genetically to subsequent generations.

Introgression: Incorporation of genetic material from one species into the gene pool of another through hybridisation.

Genetic bottleneck: Sharp reduction in population size leading to loss of genetic diversity.

References

1. Population status and genetic assessment of mugger (Crocodylus palustris) in a tropical regulated river system in North India. Scientific Reports (2024).
2. Microsatellite analysis reveals low genetic diversity in managed populations of the critically endangered gharial (Gavialis gangeticus) in India. Scientific Reports (2021).
3. Should the Identification Guidelines for Siamese Crocodiles Be Revised? Differing Post-Occipital Scute Scale Numbers Show Phenotypic Variation Does Not Result from Hybridization with Saltwater Crocodiles. Biology (2023).
4. Should I Stay or Should I Go? Dispersal and Population Structure in Small, Isolated Desert Populations of West African Crocodiles. PLOS ONE (2014).
5. Genetic evidence supports a distinct lineage of American crocodile (Crocodylus acutus) in the Greater Antilles. PeerJ (2018).
6. Phylogeography, genetic diversity, and population structure of Nile crocodile populations at the fringes of the southern African distribution. PLOS ONE (2019).
7. Ancestral Hybridization Yields Evolutionary Distinct Hybrids Lineages and Species Boundaries in Crocodiles, Posing Unique Conservation Conundrums. Frontiers in Ecology and Evolution (2018).