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title: "Cover Letter"
author: "Douglas Lawton"
format:
  pdf:
    documentclass: article
---

Dear Editors,

We are submitting our manuscript titled "Exploring Nutrient Availability and Herbivorous Insect Population Dynamics Across Multiple Scales" for consideration in *Oikos*. This study examines how variations in nutrient availability, specifically nitrogen and phosphorus, influence herbivorous insect populations across spatial scales, from local environments to continental landscapes.


Nitrogen and phosphorus are generally assumed to be limiting for herbivores, leading to the prediction that herbivore population dynamics should generally be positively correlated with environmental nitrogen and phosphorus. However, to our knowledge this relationship has not been tested from local to continental scales. In contrast, to nutrient limitation hypotheses, our study reveals that high environmental nitrogen suppresses population growth of a dominant insect herbivore - the Australian Plague Locust (*Chortoicetes terminifera*). Moreover, phosphorus shows a non-linear relationship, where its influence peaks at around 4% soil concentration before declining. These findings suggest that nutrient impacts on population dynamics are context-dependent, varying not only across trophic levels but also across spatial scales.

Using field observations, field cages over fertilized grasslands, and historical locust outbreak data from Australia, we demostrate the across-scale correlations between nutrient availability and herbivorous insect outbreaks. This integrative approach offers predictive potential for insect pest management by identifying key nutrient thresholds that could signal outbreaks. While locusts are our focal species, the implications of this work extend to other herbivorous insects globally, particularly migratory species, highlighting how nutrient-driven population dynamics can inform broader ecological patterns.

This research aligns strongly with Oikos' mission to publish work that advances our understanding of ecological mechanisms and patterns. By addressing the effects of nutrient availability on population dynamics across scales, our study challenges the traditional view that nutrient availability always drives positive population growth. Instead, we highlight the complex and sometimes suppressive roles nutrients like nitrogen and phosphorus can play, offering new insights into population regulation.Further, this work crosses disciplinary boundaries by integrating population ecology, nutrient cycling, and soil science, making it relevant not just for ecologists but also for those involved in agroecology, land management, and environmental modeling. 

We believe our study’s novel insights, combined with its practical applications, make it a strong fit for *Oikos*. Thank you for considering our submission.

Sincerely,
The Authors