Tracking Sandfly Spread and Evolution with Climate and Genetic Tools

Jim Crocker
28th March, 2025

Tracking Sandfly Spread and Evolution with Climate and Genetic Tools

Climate models support a recent post-glacial expansion for the sand fly Phlebotomus simici, showing its suitable habitat remained largely restricted after the last ice age before expanding significantly northward through the Holocene and into the current Anthropocene era.

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

Key Findings

  • In Austria, researchers identified three distinct genetic groups of Phlebotomus simici sand flies, highlighting their adaptability to different climates
  • These separate lineages demonstrate that Ph. simici is expanding into new regions previously considered unsuitable for their presence
  • Climate models predict further spread of these sand flies, raising concerns for the potential increase in leishmaniasis cases
Phlebotomine sand flies are crucial in the transmission of Leishmania parasites, which cause leishmaniasis, a disease affecting millions worldwide. Understanding the distribution and diversification of these vectors is essential for controlling the spread of the disease. A recent study conducted by researchers at the Medical University of Vienna, Austria[1], delves into the phylogenetic relationships and climatic adaptability of the subgenus Adlerius, which includes several species known to transmit different forms of leishmaniasis. The subgenus Adlerius encompasses around 20 species distributed from eastern Asia to southeastern Europe. Some of these species are confirmed or suspected vectors of Leishmania donovani/infantum, L. major, and L. tropica, making them highly relevant to public health[2]. Despite their importance, the taxonomy within Adlerius is complex, leading to challenges in accurately identifying and classifying these sand flies. One notable species within this subgenus is Phlebotomus simici. A single occurrence of Ph. simici was recorded in Austria in 2018, marking its northernmost and westernmost presence to date. The origin of this finding remains unclear, raising questions about the species' spread and adaptability to different climates. To address these questions, the study employed phylogenetic analyses combined with climatic suitability modeling to trace the diversification and post-glacial expansion of Ph. simici. The researchers discovered three distinct genetic and geographic lineages of Ph. simici, each supported by both phylogenetic data and climatic models. This differentiation suggests that Ph. simici has adapted to various climatic conditions, enabling its spread into regions previously considered unsuitable. The findings align with earlier research highlighting the difficulty in distinguishing between closely related sand fly species. For instance, a study on Chinese Adlerius phlebotomine sandflies revealed significant taxonomic challenges, particularly in differentiating Phlebotomus chinensis from Phlebotomus sichuanensis[3]. The current study further emphasizes the need for precise taxonomic classification to understand the distribution and vectorial capacity of these species. Additionally, the study highlights the role of climate in shaping the distribution of sand fly species. By modeling climatic suitability, the researchers were able to predict potential habitats for Ph. simici, providing insights into how changing climate conditions may facilitate the spread of this and other Adlerius species. This approach is reminiscent of recent efforts in Turkey, where DNA barcode reference libraries have been developed to enhance the identification and monitoring of sand fly populations across diverse biogeographical regions[4]. Such comprehensive genetic and climatic analyses are crucial for anticipating shifts in sand fly distributions and implementing effective disease control measures. The phylogenetic analysis revealed that the current geographic distribution of Adlerius species is well-supported by divergence time estimates, suggesting that historical climatic events have significantly influenced their spread. This is particularly relevant in the context of post-glacial periods, where changing climates would have enabled sand flies like Ph. simici to migrate and establish populations in new areas. Understanding these patterns is vital for predicting future changes in sand fly distributions, especially in light of ongoing climate change. Furthermore, the study uncovered several taxonomic challenges within the Adlerius subgenus, underscoring the complexity of sand fly classification. Accurate taxonomy is essential not only for scientific understanding but also for public health strategies aimed at controlling leishmaniasis. Misidentification of vector species can lead to ineffective control measures and hinder efforts to monitor disease transmission. The comprehensive phylogenetic framework established by this research enhances our understanding of Adlerius diversification and its relation to climatic factors. By delineating distinct lineages of Ph. simici and assessing their climatic suitability, the study provides valuable insights into the mechanisms driving the distribution of these important disease vectors. These findings have significant epidemiological implications, as they highlight areas that may become new hotspots for leishmaniasis transmission due to the expanding range of vector species. In conclusion, the study by the Medical University of Vienna offers a detailed analysis of the phylogenetic relationships and climatic adaptability of Adlerius sand flies, particularly Ph. simici. By integrating genetic data with climatic models, the research sheds light on the factors influencing the spread of these vectors and underscores the importance of accurate taxonomic classification. Building on previous studies[2][3][4], this work advances our understanding of sand fly biodiversity and distribution, providing a foundation for improved disease control and prevention strategies.

GeneticsEcologyEvolution

References

Main Study

1) Combining phylogeography and climate models to track the diversification and spread of Phlebotomus simici

Published 25th March, 2025

https://doi.org/10.1038/s41598-025-94601-1

Related Studies

2) Sand flies: Basic information on the vectors of leishmaniasis and their interactions with Leishmania parasites.

https://doi.org/10.1038/s42003-022-03240-z

3) Chinese phlebotomine sandflies of subgenus Adlerius nitzulescu, 1931 (Diptera: Psychodidae) and the identity of Phlebotomus sichuanensis Leng & Yin, 1983. Part I--Taxonomical study and geographical distribution.

Journal: Parasite (Paris, France), Issue: Vol 8, Issue 1, Mar 2001

4) Revision of the species composition and distribution of Turkish sand flies using DNA barcodes.

https://doi.org/10.1186/s13071-019-3669-3


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