Elevational Changes in Bacterial Microbiota Structure and Diversity in an Arthropod-Disease Vector

Area of Science:

• Microbial ecology
• Vector biology
• Ecology

Background:

• Environmental conditions vary significantly along elevational gradients, impacting macroscopic taxa diversity.
• Microbial community responses to elevation, particularly in disease vectors, remain largely uncharacterized.
• The within-vector microbiota influences vector competence for zoonotic pathogens.

Purpose of the Study:

• To investigate the impact of elevational gradients on the bacterial microbiota structure and diversity in the sheep tick, Ixodes ricinus.
• To understand how environmental factors shape microbial communities within ectotherm vectors.
• To determine if microbial diversity in ticks changes with elevation, season, life stage, or sex.

Main Methods:

• Characterized bacterial microbiota using 16S rRNA sequencing in Ixodes ricinus nymphs and adults.
• Analyzed microbial alpha and beta diversity along replicated elevational gradients in the Swiss Alps (630-1673 m).
• Assessed variations in microbial diversity based on elevation, season, tick life stage, and sex.

Main Results:

• Microbial alpha diversity (Faith's phylogenetic diversity) decreased with increasing elevation.
• Beta diversity analyses indicated lower variation in microbial community composition at higher elevations.
• Microbial diversity was higher later in the season and differed significantly among tick life stages and sexes, with adult females showing the lowest alpha diversity.

Conclusions:

• Tick bacterial microbiota diversity systematically changes along elevational gradients.
• Observed patterns in tick microbiota diversity mirror those in macroscopic taxa, suggesting a strong role for environmental factors.
• Environmental factors play a key role in shaping within-host microbial communities in ectotherms like ticks.