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

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.由伯氏疏螺旋体复合群（Borrelia burgdorferi sensu lato）引发的莱姆病（Lyme borreliosis），是北半球分布最广的蜱媒人畜共患病，但目前学界对爬行动物宿主在该病循环中的作用仍知之甚少。本研究于2013至2022年间，在伊比利亚半岛与北非的63个采样点内，采集了隶属于18个正蜥科蜥蜴（lacertid lizard）物种的363份个体样本，对伯氏疏螺旋体感染的发生情况、多样性及其生态驱动因素展开了调查。分子检测结果显示，5.8%的受试个体与22.2%的采样点检出伯氏疏螺旋体DNA，感染现象在10个蜥蜴物种中均有记录。其中，葡萄牙疏螺旋体（Borrelia lusitaniae）为优势基因种，而伽氏疏螺旋体（Borrelia garinii）的检出频率较低——这是该基因种首次在蜥蜴体内被报道。逻辑回归模型分析表明，伯氏疏螺旋体的感染发生同时受大气候条件与脊椎动物群落结构的共同调控。研究发现两类截然不同的生态场景下感染概率显著升高：其一为与鸟类主导群落相关联的暖干环境，其二为与哺乳类主导类群相关联的冷湿环境，这提示存在跨环境梯度的多条病原体传播路径。这种交互作用在环境空间中为病原体传播划定了广阔的基础生态位（fundamental niche）。但在进行地理空间投影后，预测的感染风险呈现明显的空间限制性，且主要集中于伊比利亚半岛北部。这种差异凸显了基础生态位（由气候与宿主群落的多种适配组合所定义）与现实生态位（realized niche）之间的显著错配：后者受两类因子的空间共现性，以及媒介生物与宿主分布的大气候限制所约束。因此，在环境空间中看似适宜的区域，未必会转化为地理空间中的高风险区域。本研究结果证实，正蜥科蜥蜴可维持全身性伯氏疏螺旋体感染，并参与地方性动物循环，尤其对葡萄牙疏螺旋体的循环具有重要意义。从更广泛的研究视角来看，本研究强调，若要理解并预测蜱媒疾病的风险，需整合生物交互作用与非生物约束条件，并明确区分潜在（基础）传播生态位与空间上已实现的传播生态位。