Rare gecko's DNA reveals clues to its survival on Reunion Island

Jim Crocker
14th December, 2025

Rare gecko's DNA reveals clues to its survival on Reunion Island

This assessment of the critically endangered Phelsuma inexpectata (E) across its narrow distribution on Reunion Island (A, B) highlights the species' low mitochondrial diversity (C) and significant fine-scale genetic structuring (D).

Image adapted from: Gomard et al. / CC BY (Source)

Key Findings

  • This Reunion Island gecko, Phelsuma inexpectata, has surprisingly low genetic diversity compared to related species, potentially increasing extinction risk
  • Gecko populations show genetic differences based on geographic location, with limited movement between sites due to habitat fragmentation and the gecko’s limited dispersal ability
  • While overall genetic diversity is low, natural habitats harbor slightly more diversity than areas altered by humans, highlighting the importance of conserving remaining pristine environments
The Manapany day gecko ( Phelsuma inexpectata ) is a reptile found only on the island of Reunion in the Indian Ocean, and is currently considered critically endangered. Its existence is precarious, limited to a small coastal area. Understanding the genetic health of such a restricted population is vital for effective conservation, as low genetic diversity can lead to reduced ability to adapt and increased risk of extinction. A recent study by researchers at Université de La Réunion, Association Nature Océan Indien, and State Museum of Natural History[1] aimed to provide a detailed look at the gecko’s genetic makeup and how populations are connected across its range. The study focused on analyzing the genetic variation within and between gecko populations. Researchers collected samples from 452 geckos, examining both those living in relatively undisturbed natural environments and those in areas altered by human activity – termed ‘anthropized’ sites. They used two types of genetic markers: mitochondrial genes and microsatellites. Mitochondrial genes are inherited from the mother and are useful for tracing broader historical relationships, while microsatellites – repetitive DNA sequences – provide information about genetic differences between individuals. The findings revealed surprisingly low genetic diversity compared to other similar gecko species. Only nine different versions (haplotypes) of the mitochondrial genes were found, indicating a limited gene pool. The microsatellite analysis showed an average of 2.8 different versions (alleles) per site, with observed and expected levels of genetic variation (heterozygosity) reaching a maximum of around 35%. Importantly, the study found that most populations were not significantly different from what would be expected under random mating conditions (Hardy-Weinberg equilibrium), suggesting a relatively stable genetic structure. However, despite this overall stability, the study detected a clear pattern of ‘isolation-by-distance’. This means that gecko populations further apart geographically were more genetically distinct from each other, with limited movement (migration) between sites. This isolation is likely due to a combination of historical factors, such as the original fragmentation of gecko habitat, and more recent human-caused changes, including the colonization of new areas. The research highlighted that the limited dispersal capacity of the Manapany day gecko further contributes to this vulnerability, making it difficult for geckos to move between fragmented habitats and maintain genetic connectivity. These findings align with broader concerns about reptile conservation globally[2]. Comprehensive assessments have shown that a significant proportion of reptiles are threatened with extinction, and reptiles often face unique challenges due to their diversity in arid regions and secretive nature. While previous studies have suggested that birds, mammals, and amphibians can serve as useful indicators for reptile conservation efforts[2], this study underscores the importance of directly assessing the genetic health of individual reptile species, especially those with limited ranges. The study also builds on the increasing use of genetics in amphibian and reptile conservation[3]. The use of both mitochondrial DNA and microsatellites allowed for a detailed understanding of both historical relationships and current population structure. This approach is particularly valuable for cryptic species like the Manapany day gecko, where identifying distinct populations can be difficult based on physical characteristics alone. The results of this study have direct implications for conservation management. The fragmentation and loss of habitat, coupled with low genetic diversity, make local gecko populations particularly vulnerable. The researchers emphasize the need to prioritize conservation efforts in natural sites that still harbor high levels of genetic diversity. Furthermore, the study suggests that interventions like assisted migration or captive breeding programs might be necessary to restore genetic diversity in isolated populations, as seen in conservation efforts for the Indian star tortoise (Geochelone elegans)[4], which also faces threats from habitat loss and trade. The genetic screening of founder individuals, as recommended for the star tortoise, could be a valuable tool for managing the Manapany day gecko’s genetic diversity.

WildlifeGeneticsEvolution

References

Main Study

1) First evaluation of genetic diversity and population structure of Phelsuma inexpectata (Gekkonidae), a critically endangered gecko endemic to Reunion Island

Published 12th December, 2025

https://doi.org/10.1371/journal.pone.0338217

Related Studies

2) A global reptile assessment highlights shared conservation needs of tetrapods.

https://doi.org/10.1038/s41586-022-04664-7

3) Conservation genetics and genomics of amphibians and reptiles.

https://doi.org/10.1146/annurev-animal-022114-110920

4) Mitochondrial DNA and Distribution Modelling Evidenced the Lost Genetic Diversity and Wild-Residence of Star Tortoise, Geochelone elegans (Testudines: Testudinidae) in India.

https://doi.org/10.3390/ani13010150


Related Articles

An unhandled error has occurred. Reload 🗙