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Energetic scaling across different host densities and its consequences for pathogen proliferation
Functional Ecology ( IF 5.2 ) Pub Date : 2020-11-28 , DOI: 10.1111/1365-2435.13721
Louise Solveig Nørgaard 1 , Giulia Ghedini 1 , Ben L. Phillips 2 , Matthew D. Hall 1
Affiliation  

  1. The spread of infectious disease is determined by the ability of a pathogen to proliferate within and spread between susceptible hosts. Processes that limit the performance of a pathogen thus occur at two scales: varying with both the availability of energy within a host, and the number of susceptible hosts in a patch. When the rate at which a host intakes and expends energy is density‐dependent, these two processes are intimately linked.
  2. By modifying how hosts compete for and expend resources, a shift in population density may contribute to differences in the flow of energy in a host–pathogen system, both in terms of the energy available for a host to grow, reproduce and fight infection, as well as the energy available for a pathogen to exploit. Energy flux, therefore, connects the two contrasting scales of within‐ and between‐host dynamics by directly linking the proliferation of a pathogen to the number of hosts circulating within a patch.
  3. We use the host Daphnia magna to explore the relationship between energy intake and expenditure at various population densities, as estimated by feeding and metabolic rates respectively. By infecting hosts with the bacterial pathogen Pasteuria ramosa, we then explore how infection changes the relative balance of energy intake and expenditure, and how this energy scope translates into production of transmission spores.
  4. Our work demonstrates that energy intake declines at a faster rate with density than does metabolic rate, leaving more excess energy (i.e. discretionary energy) available for both hosts and their dependent pathogens at low population densities. This energetic advantage translates positively into host and pathogen growth, with the production of mature transmission spores benefiting most from correlated changes in host body size, as well as a direct connection between energy scope and spore loads.
  5. Our findings reinforce how patch quality for a pathogen operates at two contrasting scales, with the within‐host proliferation of a pathogen being optimised in energy rich, low density host populations and opportunities for between‐host transmission likely maximised in dense populations.


中文翻译:

不同宿主密度的能量扩展及其对病原体增殖的影响

  1. 传染病的传播取决于病原体在易感宿主内增殖以及在易感宿主之间传播的能力。因此,限制病原体性能的过程发生在两个方面:随着宿主体内能量的可用性以及贴片中易感宿主的数量而变化。当宿主摄取和消耗能量的速率取决于密度时,这两个过程紧密相关。
  2. 通过改变宿主竞争和消耗资源的方式,种群密度的变化可能会导致宿主-病原体系统中能量流动的差异,无论是在宿主生长,繁殖和抵抗感染的可用能量方面。以及病原体可利用的能量。因此,能量通量通过将病原体的增殖与斑块内循环的宿主数量直接联系起来,将宿主内部和宿主之间动态的两个相对尺度联系起来。
  3. 我们使用寄主蚤(Daphnia magna)来探索各种人口密度下能量摄入与消耗之间的关系,分别通过摄食和代谢率进行估算。通过用细菌性病原体巴斯德氏菌感染宿主,我们然后探索感染如何改变能量摄入和消耗的相对平衡,以及这种能量范围如何转化为传播孢子的产生。
  4. 我们的工作表明,能量吸收的密度下降速度快于新陈代谢速度,从而在低人口密度下为宿主及其依赖病原体留下更多的多余能量(即自由能)。这种有力的优势可以肯定地转化为宿主和病原体的生长,成熟的传播孢子的产生最受益于宿主体大小的相关变化,以及能量范围和孢子负荷之间的直接联系。
  5. 我们的发现加强了病原体的斑块质量如何在两个相反的规模上运作,病原体的宿主内增殖在能量丰富,低密度的宿主种群中得到优化,并且在致密种群中宿主间传播的机会可能最大化。
更新日期:2021-02-04
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