Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA; Ecology Center, Utah State University, 5205 Old Main Hill, Logan, UT 84322, USA.
Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA; Ecology Center, Utah State University, 5205 Old Main Hill, Logan, UT 84322, USA.
Gen Comp Endocrinol. 2023 Jun 1;337:114258. doi: 10.1016/j.ygcen.2023.114258. Epub 2023 Mar 3.
Urbanization can cause innumerable abiotic and biotic changes that have the potential to influence the ecology, behavior, and physiology of native resident organisms. Relative to their rural conspecifics, urban Side-blotched Lizard (Uta stansburiana) populations in southern Utah have lower survival prospects and maximize reproductive investment via producing larger eggs and larger clutch sizes. While egg size is an important predictor of offspring quality, physiological factors within the egg yolk are reflective of the maternal environment and can alter offspring traits, especially during energetically costly processes, such as reproduction or immunity. Therefore, maternal effects may represent an adaptive mechanism by which urban-dwelling species can persist within a variable landscape. In this study, we assess urban and rural differences in egg yolk bacterial killing ability (BKA), corticosterone (CORT), oxidative status (d-ROMs), and energy metabolites (free glycerol and triglycerides), and their association with female immune status and egg quality. Within a laboratory setting, we immune challenged urban lizards via lipopolysaccharide injection (LPS) to test whether physiological changes associated with immune system activity impacted egg yolk investment. We found urban females had higher mite loads than rural females, however mite burden was related to yolk BKA in rural eggs, but not urban eggs. While yolk BKA differed between urban and rural sites, egg mass and egg viability (fertilized vs. unfertilized) were strong predictors of yolk physiology and may imply tradeoffs exist between maintenance and reproduction. LPS treatment caused a decrease in egg yolk d-ROMs relative to the control treatments, supporting results from previous research. Finally, urban lizards laid a higher proportion of unfertilized eggs, which differed in egg yolk BKA, CORT, and triglycerides in comparison to fertilized eggs. Because rural lizards laid only viable eggs during this study, these results suggest that reduced egg viability is a potential cost of living in an urban environment. Furthermore, these results help us better understand potential downstream impacts of urbanization on offspring survival, fitness, and overall population health.
城市化会导致无数的非生物和生物变化，这些变化有可能影响本地居民生物的生态、行为和生理机能。犹他州南部的城市斑点鬣蜥（Uta stansburiana）种群与农村同物种相比，生存前景较差，通过产更大的卵和更大的卵窝来实现最大的生殖投资。虽然卵的大小是后代质量的重要预测指标，但卵黄内的生理因素反映了母体环境，并可以改变后代的特征，特别是在繁殖或免疫等能量消耗大的过程中。因此，母体效应可能代表了一种适应机制，使城市居住物种能够在多变的景观中生存。在这项研究中，我们评估了城市和农村在卵黄细菌杀伤能力（BKA）、皮质酮（CORT）、氧化状态（d-ROMs）和能量代谢物（游离甘油和甘油三酯）方面的差异，以及它们与雌性免疫状态和卵质量的关系。在实验室环境中，我们通过脂多糖（LPS）注射对城市蜥蜴进行免疫挑战，以测试与免疫系统活动相关的生理变化是否会影响卵黄投资。我们发现，城市雌性的螨虫负荷高于农村雌性，但螨虫负担与农村卵黄的 BKA 有关，而与城市卵黄无关。虽然卵黄 BKA 在城市和农村之间存在差异，但卵质量和卵活力（受精卵与未受精卵）是卵黄生理学的有力预测指标，这可能意味着维护和繁殖之间存在权衡。LPS 处理导致卵黄 d-ROMs 相对于对照处理减少，支持了之前研究的结果。最后，城市蜥蜴产下的未受精卵比例较高，与受精卵相比，其卵黄 BKA、CORT 和甘油三酯存在差异。由于在这项研究中农村蜥蜴只产下了可育的卵，因此这些结果表明，在城市环境中生存的潜在代价是降低卵的活力。此外，这些结果有助于我们更好地了解城市化对后代生存、适应度和整体种群健康的潜在下游影响。
