Ticks are a diverse group of arachnids that are obligate ectoparasites of vertebrates, and in many cases, serve as vectors of pathogens with significant public health implications. While most tick species parasitize warm-blooded vertebrates, some exhibit specialized host associations with reptiles and tortoises (Guglielmone et al., 2023). Climate has long been recognized as a major determinant of tick distribution (e.g., Nuttall, 2022). However, the transmission cycles of tick-borne pathogens depend on specific ecological interactions between ticks and vertebrate communities, including competent reservoir hosts (Kiewra and Lonc, 2012, Estrada-Peña et al., 2015). The role of climate in shaping tick distributions has been widely studied using various descriptive variables and modelling frameworks. Land use, livestock movements, and habitat alterations may be driven by human actions (Vanwambeke et al., 2024) and are among others potential confounding effects that could obscure the results of modelling efforts (Diuk-Wasser et al., 2021, Mysterud et al., 2021). Similarly, projections of pathogen ranges have frequently relied solely on climatic predictors, overlooking the essential role of vertebrate hosts (e.g., Zhao et al., 2021). Although several studies have demonstrated the influence of key vertebrate species and host communities structure at regional scales (e.g., Tijsse-Klasen et al., 2010; Rocha et al., 2022), an interpretation of the epidemiological significance incorporating such biotic factors for large territories remains missing. A community-based approach is necessary; however, representations of communities for ticks and hosts remain restricted at the regional scale of field studies.

The delineation of biogeographical regions has traditionally relied on taxonomic information. Advances in phylogenetic inference and biogeographical analysis have facilitated refined modelling approaches, enabling the reconstruction of evolutionary relationships across entire taxonomic assemblages (Daru et al., 2020; Holt et al., 2013; Wang et al., 2023). Phylogenetic bioregionalization allows the identification of historical connections among regions based on shared evolutionary history, which is often shaped and maintained by climatic factors (Edler et al., 2017). Unlike traditional bioregionalization, which typically relies on species presence-absence, phylogenetic bioregionalization incorporates phylogenetic distances to identify regions that share lineages with common evolutionary histories (Holt et al., 2013; Daru et al., 2020). This method provides a more nuanced understanding of historical biotic connections and diversification processes, offering insights into how regions have accumulated and retained distinct evolutionary lineages (Mishler et al., 2014). It is particularly valuable in revealing cryptic patterns of biodiversity and in identifying regions of high phylogenetic endemism, which may not align with patterns detected using taxonomic data alone. Metrics of phylogenetic ß-diversity (e.g., turnover and nestedness) are commonly used to quantify similarities among regions, allowing the identification of phylogenetically coherent clusters (Daru et al., 2017; Rosauer et al., 2009). Phylogenetic bioregionalization thus strengthens biogeographical analyses by integrating evolutionary history into spatial biodiversity patterns, supporting both macroecological research and conservation planning.

The concept of chorotype was originally introduced by De Lattin (1967) and later refined by other authors (e.g., Fattorini, 2015, Passalacqua, 2015). In biogeography, a chorotype represents a group of species that co-occur, often reflecting shared ecological adaptations, dispersal barriers, or evolutionary histories. Traditionally, the concept has been used for biogeographical descriptions, as chorotypes define patterns of co-occurrences of taxa. This ecological information may also be applied to the epidemiological description of a territory. If suitable hosts for tick vectors and competent reservoirs for pathogens do not overlap spatially, pathogen persistence is likely to be compromised (e.g., Ewen et al., 2012, Clark and Clegg, 2015, Ellis et al., 2015). Given that a chorotype provides a rigorous definition of co-occurring organisms, an explicit statistical comparison among chorotypes would allow the identification of territories where tick-borne pathogens may circulate, because it would recognize the community composition. Thus, the chorotype would accommodate the varying contributions of different vertebrate hosts and ticks for pathogen transmission.

Conventional approaches that focus on individual interactions among hosts, vectors, and pathogens are insufficient to capture complex dynamics. Instead, the chorotype framework, by identifying geographically coherent groups of co-occurring ticks and vertebrates, may reveal how phylogenetic relationships and climate jointly shape epidemiological patterns. This approach may be particularly well suited for understanding the spatial distribution of tick-borne pathogens, as it simultaneously considers climatic constraints, overlap between and among groups of taxa, and host phylogenetic structure. The availability of critical hosts can influence tick life cycles, particularly for species with narrow host preferences or those that switch host groups across developmental stages (Guglielmone et al., 2023). Ticks may be phylogenetically constrained to some hosts; such restrictions may limit the establishment of the pathogens they transmit because the lack of resources necessary for pathogen circulation. Since pathogen presence ultimately depends on the ecological requirements and distributional overlaps of the vectors, reservoirs, and hosts, its niche must be understood as an emergent property driven by the joint responses to abiotic conditions of all actors (Estrada-Peña et al., 2015).

This study investigates the regionalization of tick–vertebrate associations across the Western Palearctic and Afrotropical regions, with a focus on climatic influences. By analyzing the co-occurrence patterns of 82 tick species and 121 vertebrate genera, we aim to assess how climate influences tick endemism and ß-diversity across the study area. The main aim is the building of statistically homogeneous groups of co-occurring ticks that share environmental niches, and its homologous counterpart in the available hosts.