The interplay between macroclimate and vertebrate community explains the occurrence of Borrelia spp. in Iberian lizards

Description

Lyme borreliosis, caused by Borrelia burgdorferi sensu lato, is the most widespread tick-borne zoonosis in the Northern Hemisphere, yet the role of reptile hosts remains poorly understood. We investigated the occurrence, diversity, and ecological drivers of Borrelia infection in 363 individuals from 18 lacertid lizard species sampled across 63 localities in the Iberian Peninsula and North Africa between 2013 and 2022. Molecular analyses detected Borrelia DNA in 5.8% of individuals and 22.2% of sites, with infections recorded in 10 species. Borrelia lusitaniae was the predominant genospecies, while B. garinii was detected at low frequency, representing the first report of this genospecies in lizards. Logistic models revealed that Borrelia occurrence is jointly driven by macroclimatic conditions and vertebrate community composition. High infection probabilities emerged under two contrasting ecological scenarios: (i) warm, dry environments associated with bird-dominated communities, and (ii) cold, humid environments associated with mammal-dominated assemblages, indicating alternative transmission pathways across environmental gradients. This interaction defines a broad fundamental niche for pathogen transmission in environmental space. However, when projected geographically, predicted infection risk was spatially constrained and largely restricted to northern Iberia. This discrepancy highlights a pronounced mismatch between the fundamental niche –defined by multiple suitable combinations of climate and host community– and the realized niche, which is limited by the spatial co-occurrence of these factors and by macroclimatic constraints on vector and host distributions. Consequently, areas that appear suitable in environmental space do not necessarily translate into high-risk regions in geographic space. Our findings demonstrate that lacertid lizards can sustain systemic Borrelia infections and contribute to enzootic cycles, particularly for B. lusitaniae. More broadly, the study underscores that understanding and predicting tick-borne disease risk requires integrating biotic interactions and abiotic constraints and explicitly distinguishing between potential (fundamental) and spatially realized transmission niches.

Steps to reproduce

Sample collection Blood samples were obtained from 363 adult lizards belonging to 18 lacertid species from April to July between 2013 and 2022. The lizards were sampled at 60 sites in the Iberian Peninsula, two sites in northern Morocco, and one site in the Chafarinas Islands (Figure 2; Table S1). We implemented a cost-effective approach and analysed 3-20individuals per species and sampling site (mode = 5). A blood sample was collected from each lizard using sterile needles (25G, BD Microlance) from the coccygeal vein on the underside of the tail base, avoiding the hemipenal area in males (Megía-Palma et al., 2024). Blood samples were preserved for subsequent molecular analysis on FTA cards that are specially designed to preserve DNA integrity. A binomial variable for tick presence in a site was defined, considering a site as positive if at least one lizard carried at least one tick. This variable is built upon previous surveys (Megía-Palma et al., 2018, 2023, 2024; Hernández-Rojas et al., 2025), which utilized larger sample sizes per site, thereby increasing the probability of detecting tick-infested hosts. Macroclimate mapping Macroclimatic variables were obtained from the TerraClimate dataset, which provides ~4 km-resolution of monthly climate and water balance data from 1958 onwards (Abatzoglou et al., 2018). For each site, monthly climate data were extracted from locally stored NetCDF files corresponding to the previous five years. Data extraction was performed using the terra package in R (Hijmans et al., 2026), ensuring spatial alignment between raster layers and geographic coordinates. The following variables were selected based on their ecological relevance to vector-borne pathogen dynamics: minimum temperature (tmin), maximum temperature (tmax), precipitation (ppt), vapour pressure deficit (vpd), and climatic water deficit (def). Mean temperature (tmean) was calculated as the average of monthly minimum and maximum temperatures. To characterize macroclimatic conditions at each site, monthly values were aggregated across the sampling period to derive summarized variables, including mean temperature, temperature variability (standard deviation), total precipitation, mean vapour pressure deficit, and mean climatic water deficit. Biodiversity mapping We downloaded raster images of vertebrate community richness (i.e., passerine birds, and mammal orders Rodentia, Cetartiodactyla, and Eulipotyphla) from biodiversitymapping.org, based on IUCN (2025) and with a resolution of 10 × 10 km (Jenkins et al., 2013). We rescaled raster images to fit a common reference system. The available raster information did not include data of vertebrate species richness for the Chafarinas Islands. Thus, the final dataset only included sites on the Iberian Peninsula and Morocco.

Institutions

• Universidad Complutense de Madrid

  Madrid, Madrid
• Instituto de Salud Carlos III

  Madrid, Madrid

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