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Scatter-hoarding rodent foraging preference on nutrient content is mediated by seed size
Current Zoology ( IF 2.2 ) Pub Date : 2020-01-03 , DOI: 10.1093/cz/zoz064
Bo Wang 1, 2 , Xiaolan Yang 2
Affiliation  

Seed dispersal and predation by scatter-hoarding rodents play an important role in seedling regeneration, community structure and composition, and species coexistence (Vander Wall 2010; Zhang et al. 2016). Rodents generally exhibit seed species preference during their scatter-hoarding behavioral processes (Xiao et al. 2006; Gong et al. 2015; Zhang et al. 2016), and seed traits are a key factor in explaining rodent foraging preference (Wang and Chen 2009; Vander Wall 2010; Zhang et al. 2016). Numerous studies have explored how the diversity of seed traits influences rodent foraging behavior but have shown inconsistent results (Blate et al. 1998; Moles et al. 2003; Xiao et al. 2006; Wang and Chen 2009). These disparate results are likely because of the complicated interactions among traits (Gong et al. 2015; Zhang et al. 2016). In other words, the effect of a given seed trait on rodent foraging behavior may be influenced by other seed traits. However, few studies have directly targeted the interactive effects among seed traits, possibly because of the lack of nondestructive methods for measuring many seed traits, which makes it difficult to compare among individual seeds. Theoretically, multispecies studies provide a potential way to test the interactive effects of different seed traits on rodent foraging preference, by using the mean values of seed traits for each species. However, until now, few studies have included enough species to perform a statistical analysis of the interactive effects among traits (but see Gong et al. 2015; Zhang et al. 2016). Furthermore, large intraspecific variation often exists in many seed traits (Wang and Ives 2017), which may bias the results of interspecific comparisons by using mean values. Artificial seed experimental systems provide an opportunity to ascertain the joint effects of several seed traits by precisely controlling each target trait individually (Wang and Chen 2009, 2012; Wang and Yang 2014). However, all these studies only pointed out the potential interactive effects among traits, and did not analyze how one seed trait would influence the magnitude or intensity of the effect of another trait on rodent foraging preference. In this study, we used artificial seeds to target two important seed traits—seed size and nutrient content—to further explore how one seed trait influences the effect magnitude of another trait on the foraging preference of scatter-hoarding rodents (see Supplementary Material). Nutrient content showed a positive effect on the probability of seeds being harvested for all seed sizes, with the mean estimate value being 0.183 6 0.061 (standard deviation), and a range from 0.087 to 0.262 (Figure 1A). Seed size showed a positive effect on the magnitude of nutrient effect on seed harvest, with the nutrient effect on seed harvest being much stronger among large-sized than smallsized seeds (Pearson’s correlation, R 1⁄4 0.555, P1⁄40.005; Figure 1A). Of the harvested seeds, nutrient content showed a negative effect on the probability of seeds being removed rather than eaten in situ; however, the significant effect only existed among large seeds (>3 cm in diameter), with the mean estimate value being 0.027 6 0.006, and a range from 0.020 to 0.032 (Figure 1B). Furthermore, a negative correlation was detected between seed size and the magnitude of nutrient effects (R 1⁄4 0.590, P1⁄40.006). No effect was observed between nutrient content and either removal distance or the probability of seeds being cached after removal for all seed sizes, except among the seeds with 3.5 cm diameter, where the nutrient content showed a positive effect on seed removal distance (linear mixed-effects model, t1⁄43.023, P1⁄40.004; Figure 1C). Our study showed that the magnitude of nutrient effects on seed dispersal and predation by rodents was mediated by seed size, although this pattern did not exist during all the scatter-hoarding processes. Our hypothesis was proved that larger seed size could strengthen the effect of nutrient content on rodent foraging preference. A large seed often represents more absolute nutrients (Gong et al. 2015), which may in turn stimulate the rodent’s selection biases during their foraging processes. Decision-making during foraging often costs both time and energy; thus, rodents may show a stronger selection bias among large seeds than among small ones, because of the larger benefit per input cost. In addition, handling large seeds usually requires more foraging investment and involves

中文翻译:

分散囤积啮齿动物对营养成分的觅食偏好由种子大小介导

分散囤积啮齿动物的种子传播和捕食在幼苗再生、群落结构和组成以及物种共存方面发挥着重要作用(Vander Wall 2010;Zhang et al. 2016)。啮齿动物在其分散囤积行为过程中通常表现出种子物种偏好(Xiao et al. 2006; Gong et al. 2015; Zhang et al. 2016),而种子性状是解释啮齿动物觅食偏好的关键因素(Wang and Chen 2009) ;Vander Wall 2010;Zhang 等人 2016)。许多研究探索了种子性状的多样性如何影响啮齿动物的觅食行为,但结果不一致(Blate 等,1998;Moles 等,2003;Xiao 等,2006;Wang 和 Chen,2009)。这些不同的结果很可能是因为性状之间复杂的相互作用(Gong 等人,2015 年;Zhang 等人,2016 年)。换句话说,给定种子性状对啮齿动物觅食行为的影响可能会受到其他种子性状的影响。然而,很少有研究直接针对种子性状之间的交互作用,可能是因为缺乏测量许多种子性状的无损方法,这使得很难在单个种子之间进行比较。从理论上讲,多物种研究提供了一种通过使用每个物种种子性状的平均值来测试不同种子性状对啮齿动物觅食偏好的交互影响的潜在方法。然而,直到现在,很少有研究包括足够的物种来对性状之间的交互效应进行统计分析(但见龚等人。2015;张等人。2016)。此外,许多种子性状通常存在较大的种内变异(Wang and Ives 2017),这可能会通过使用平均值来偏向种间比较的结果。人工种子实验系统通过单独精确控制每个目标性状,为确定多个种子性状的联合效应提供了机会(Wang and Chen 2009, 2012; Wang and Yang 2014)。然而,所有这些研究都只指出了性状之间潜在的交互作用,并没有分析一种种子性状如何影响另一种性状对啮齿动物觅食偏好影响的大小或强度。在这项研究中,我们使用人造种子来针对两个重要的种子性状——种子大小和营养含量——进一步探索一种种子性状如何影响另一种性状对散播啮齿动物觅食偏好的影响程度(见补充材料)。营养成分对所有种子大小的种子收获概率都有积极影响,平均估计值为 0.183 6 0.061(标准偏差),范围为 0.087 至 0.262(图 1A)。种子大小对种子收获的养分作用大小呈正影响,大粒种子对收获的养分作用比小粒种子强得多(Pearson 相关系数,R 1⁄4 0.555,P1⁄40.005;图 1A) . 在收获的种子中,营养成分对种子被移除而不是原地食用的可能性有负面​​影响;然而,仅在大种子(直径> 3 cm)中存在显着影响,平均估计值为0.027 6 0.006,范围为0.020至0.032(图1B)。此外,在种子大小和养分效应的大小之间检测到负相关 (R 1⁄4 0.590, P1⁄40.006)。对于所有大小的种子,营养含量与移除距离或移除后种子被缓存的概率之间没有观察到影响,除了直径为 3.5 cm 的种子,其中营养含量对种子移除距离显示出积极的影响(线性混合 -效应模型,t1⁄43.023,P1⁄40.004;图 1C)。我们的研究表明,养分对啮齿动物种子传播和捕食的影响程度受种子大小的影响,尽管这种模式在所有分散囤积过程中都不存在。我们的假设被证明,较大的种子大小可以加强营养成分对啮齿动物觅食偏好的影响。一颗大种子通常代表更多的绝对营养(Gong et al. 2015),这可能反过来刺激啮齿动物在觅食过程中的选择偏差。觅食过程中的决策往往既耗费时间又耗费精力;因此,啮齿动物在大种子中的选择偏差可能比在小种子中更强,因为单位投入成本的收益更大。此外,处理大种子通常需要更多的觅食投资并涉及
更新日期:2020-01-03
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