Native insect herbivory overwhelms context dependence to limit complex invasion dynamics of exotic weeds

Abstract

Understanding the role of consumers in density-dependent plant population dynamics is a long-standing goal in ecology. However, the generality of herbivory effects across heterogeneous landscapes is poorly understood due to the pervasive influence of context-dependence. We tested effects of native insect herbivory on the population dynamics of an exotic thistle, Cirsium vulgare, in a field experiment replicated across eight sites in eastern Nebraska. Using hierarchical Bayesian analysis and density-dependent population models, we found potential for explosive low-density population growth (λ > 5) and complex density fluctuations under herbivore exclusion. However, herbivore access drove population decline (λ < 1), suppressing complex fluctuations. While plant-herbivore interaction outcomes are famously context-dependent, we demonstrated that herbivores suppress potentially invasive populations throughout our study region, and this qualitative outcome is insensitive to environmental context. Our novel use of Bayesian demographic modelling shows that native insect herbivores consistently prevent hard-to-predict fluctuations of weeds in environments otherwise susceptible to invasion.

Release from natural enemies mitigates inbreeding depression in native and invasive Silene latifolia populations

“…The latter can occur, since the investment in reproduction by the end of a growing season is highly dependent on an individual's cumulative performance and thus on the cumulative effects of inbreeding and stress (natural enemies) on performance throughout the season (Orr, 2009). Our finding supports that the release from coevolved native enemies in the invaded habitat has the potential to mitigate detrimental inbreeding and stressful conditions should thus ideally quantify seed output, viability, and germination as well as demographic rates in order to parameterize models that estimate population growth and spread rates (Normand, Zimmermann, Schurr, & Lischke, 2014;Schultz, Eckberg, Berg, Louda, & Miller, 2017).…”

“…Moreover, the effect sizes for I × E interaction effects on fruit number in our study were low, and thus, it remains to be investigated whether they can indeed impact population growth rates. Future studies comparing estimates of inbreeding depression in plant invaders under benign and stressful conditions should thus ideally quantify seed output, viability, and germination as well as demographic rates in order to parameterize models that estimate population growth and spread rates (Normand, Zimmermann, Schurr, & Lischke, ; Schultz, Eckberg, Berg, Louda, & Miller, ).…”

Take me for a ride: Herbivores can facilitate plant reinvasions

“…In accordance with existing theory, we find that in many syndromes herbivores slow spreading speed, primarily through impacts on plant demography (Fagan et al, 2005; Fagan & Bishop, 2000; Holt & Barfield, 2009; Owen & Lewis, 2001; Radny & Meyer, 2018). Empirical evidence demonstrates that herbivores either consume plant tissue that subsequently decreases seed production (Foster & Ackerman, 2021; Hrafnkelsdottir et al, 2020; Miller et al, 2009; Schultz et al, 2017), or fully consume adult plants (Auberson‐Lavoie & Vellend, 2020; Kuijper et al, 2004; Rivest & Vellend, 2018), both which in turn slow spatial spread. Our findings that stage‐specific consumption by herbivores can cause different effects on plant spread rate fits with the broad literature using structured models (Caswell, 2000) to target certain stages for the conservation of endangered species (e.g., alterations to adult stages are often the most critical; Crouse et al, 1987) and control of invasive species (Buckley et al, 2005).…”

Research advances of plant invasion ecology over the past 10 years

“…Kalisz et al, 2014)。然而, 越来越 多研究发现入侵地一些植食性天敌的采食行为也 可能阻抗外来植物入侵(Kempel & Chrobock et al, 2013;Schultz et al, 2017;Zhang et al, 2018;Christianen et al, 2019)。例如 ,& Vilà, 2001;Huang et al, 2010; Schaffner et al, , 2017;Mariotte et al, 2018;Zhang X et al, 2021)。菌根真菌在外来植物入侵中的作用近年 来得到了关注(Suding et al, 2013;Bunn et al, 2015;Dickie et al, 2017;Chen et al, 2020)。 "共生促进"假说 (enhanced mutualisms hypothesis)认为, 外来植物在 入侵地与当地一些高效的共生真菌形成新的相互 作 用 , 促 进 其 入 侵Baynes et al, 2012;Tian et al, 2021;Sheng et al, 2022;Yu et al, 2022)。 例 如 , 与原产地种群相比, 乌桕与小 飞蓬(Conyza canadensis)的入侵地种群的菌根真菌 寄生率更高、植物生物量更大(Yang et al, 2015;Sheng et al, 2022), 这种更强的"共生促进"关系主要 是由根系分泌物中类黄酮的变化驱动的(Tian et al, et al, 2013;Stricker et al, 2016), 也可能通过溢出效应对邻近植物产生抑制, 从而促进入侵 al, 2020b)。同理, 本地植物也会募集一些病原微生物 抑制外来植物入侵(Zhang et al, 2020a)。另外, 本地 植物募集的病原微生物对外来植物的抑制作用通 常高于外来植物募集的病原微生物对外来植物的 抑制作用(Zhang et al, 2020b), 时发生(Waller et al, 2020; Allen et al, 2021)。自 Bennett (2013)综述并强调了这种复杂多类群互作 (Liu et al, 2017), 并且这种促 进效应 在水 生系 统 更加明显 (Sorte et al, 2013)。增温(Haeuser et al, 2017, 2019) 与 大 气 CO 2 浓 度 上 升 (Blumenthal et al, 2013; Mozdzer & Caplan, 2018)驱动外来植物入侵的现象 也不断被证实。一项基于全球13个国家64片草地的 养分添加实验发现, 养分增加显著提高了外来植物 优势度(Seabloom et al, 2015)。同样, 水分和光照等 资 源 的 增 加 也 可 能 加 速 外 来 植 物 的 入 侵 过 程 (Davidson et al, 2011; Sorte et al, 2013)。最新的研究 暗示城市化进程中路灯建设引起的夜间光污染促 进了一些外来植物的入侵(Speißer et al, 2021; Liu YJ et al, 2022; Murphy et al, 2022)。另外, 与单一的 光照或养分增加相比, 光照与养分同时增加更能加 剧外来入侵植物对本地植物的竞争排斥(Zhang et al, 2022)。因此 , Richards等(2006)指出许多外来入侵植 物在应对生存条件变优越、资源增加的环境变化时 "专家型策略" (master of some)。最新的研 究显示干旱(Copeland et al, 2016; Liu et al, 2017; Valliere et al, 2019)与臭氧胁迫(Wang LC et al, 2022) Zhang et al, 2020a; Li YJ et al, 2022)。 这也解释了为 什 么 个 别 研 究 发 现 资 源 波 动 不 影 响 (Frevola & Hovick, 2019; Shi et al, 2021)甚至抑制外来植物入 侵(Liu et al, 2018), 群 落 (novel community) 或 新 型 生 态 系 统 (novel ecosystem, Richardson & Gaertner, 2013)。这 2017 年 , Journal of Ecology 发 表 了 关 于 "Long-Term Dynamics and Impacts of Plant Invasions" species role), 对传粉网络的嵌套性 (nestedness) 、 连 通 度 (connectance) 和 稳 健 性 (robustness) 等 可 能 无 显 著 影 响 (Bartomeus et al, 2008; Stouffer et al, 2014; Parra-Tabla et al, 2019; Corcos et al, 2020)。 目前, WW et al, 2020; Qiu et al, 2020; Xu et al, 2022b), 以及植食动物(Xu et al, 2022a)和致病 微生物(Li et al, 2014)等介导的间接影响, 显著改变 了我国南方红树林和中、北部盐沼生态系统的植物 群落组成与结构(Wang et al, 2019; Ren et al, 2021), 导致依赖于本地生产者为营养源或栖息生境的昆 虫(Sun KK et al, 2020)、土壤生物(Zhang YZ et al, et al, 2019), 不仅能够改变其新占据生 境的植物群落组成(Alexander et al, 2015)和地上昆 虫群落(Bezemer et al, 2014), 还可以改变这些区域 的土壤线虫群落(Wilschut et al, 2016)和微...…”