Graham Jason M, Klobusicky Joseph, Hague Michael T J
Mathematics Department University of Scranton Scranton Pennsylvania USA.
Biology Department University of Scranton Scranton Pennsylvania USA.
Ecol Evol. 2025 Aug 17;15(8):e71989. doi: 10.1002/ece3.71989. eCollection 2025 Aug.
Many insects and other animals host heritable endosymbionts that alter host fitness and reproduction. The prevalence of facultative endosymbionts can fluctuate in host populations across time and geography for reasons that are poorly understood. This is particularly true for maternally transmitted bacteria, which infect roughly half of all insect species. For instance, the frequencies of several Mel-like , including Mel in host , fluctuate over time in certain host populations, but the specific conditions that generate temporal variation in prevalence are unresolved. We implemented a discrete generation model in the new R package to evaluate how finite-population stochasticity contributes to fluctuations over time in simulated host populations under a variety of conditions. Using empirical estimates from natural - systems, we explored how stochasticity is determined by a broad range of factors, including host population size, maternal transmission rates, and effects on host fitness (modeled as fecundity) and reproduction (cytoplasmic incompatibility; CI). While stochasticity generally increases when host fitness benefits and CI are relaxed, we found that a decline in the maternal transmission rate had the strongest relative impact on increasing the size of fluctuations. We infer that non- or weak-CI-causing strains like Mel, which often show evidence of imperfect maternal transmission, tend to generate larger stochastic fluctuations compared to strains that cause strong CI, like Ri in . Additional factors, such as fluctuating host fitness effects, are required to explain the largest examples of temporal variation in . The conditions we simulate here using serve as a jumping-off point for understanding drivers of temporal and spatial variation in the prevalence of , the most common endosymbionts found in nature.
许多昆虫和其他动物体内携带着可遗传的内共生体，这些内共生体会改变宿主的健康状况和繁殖能力。兼性内共生体在宿主种群中的流行程度会随时间和地理位置而波动，其原因目前尚不清楚。对于通过母体传播的细菌来说尤其如此，这类细菌感染了大约一半的昆虫物种。例如，几种Mel样细菌，包括宿主中的Mel，在某些宿主种群中的频率会随时间波动，但导致其流行程度随时间变化的具体条件仍未明确。我们在新的R包中实现了一个离散世代模型，以评估在各种条件下，有限种群的随机性如何导致模拟宿主种群中随时间的波动。利用来自自然系统的实证估计，我们探讨了随机性是如何由一系列广泛的因素决定的，包括宿主种群大小、母体传播率以及对宿主健康状况（以繁殖力建模）和繁殖（细胞质不亲和性；CI）的影响。虽然当宿主健康益处和CI减弱时，随机性通常会增加，但我们发现母体传播率的下降对增加波动幅度的相对影响最大。我们推断与导致强CI的菌株（如中的Ri）相比，像Mel这样不引起或弱引起CI的菌株，往往表现出不完全母体传播的证据，倾向于产生更大的随机波动。还需要其他因素，如波动的宿主健康效应，来解释中随时间变化的最大实例。我们在此使用模拟的条件作为理解自然界中最常见的内共生体流行程度随时间和空间变化的驱动因素的起点。
