DOI: 10.5061/dryad.jsxksn0df
title: Towards a mechanistic understanding of variation in aquatic food chain length revealed by meta-analysis

description: Ecologists have long sought to understand the forces determining food
 chain lengths (FCLs). Multiple hypotheses have proposed a diverse array of
 potential environmental determinants of FCL, typically including ecosystem
 size, resource productivity, and disturbance. Yet, many empirical studies
 have found that FCL responses to these environmental variables can be
 positive as well as negative. To explain such mixed responses, we develop
 a simple yet comprehensive, site-occupancy dynamic framework for complex
 food webs by integrating multiple environmental drivers. With the
 competition-colonization tradeoff among basal species, our model shows
 that increasing ecosystem size results in a monotonic increase in FCL as a
 whole, while FCL displays a non-linear, oscillatory response to resource
 productivity or disturbance in benign environments. These predictions are
 generally supported by our meta-analysis of an empirical dataset compiled
 from diverse aquatic ecosystems. Therefore, this unifying framework offers
 a novel mechanistic explanation for observed variation in FCLs driven by
 multiple environmental factors.
description: We collected a large empirical dataset of changes in food chain
 length (FCL) in response to ecosystem size, resource productivity, and
 disturbance respectively, compiled from 30 published papers (see
 "References.docx"). This data set includes 36 empirical cases
 relating to ecosystem size, 36 cases relating to resource productivity,
 and 16 cases relating to disturbance. We measure the FCL response to these
 variables using the log response ratio (LRR). All these LRR values are
 listed in the file "Empirical dataset": namely
 "LRR_Ecosystem size.xlsx", "LRR_Resource
 productivity.xlsx" and "LRR_Disturbance.xlsx". 
 We also compiled the empirical data (see
 "Empirical_food_chain_data.csv") for both one- and two-way model
 analysis, where three variables are included: ecosystem size (size),
 resource productivity (resource), and distrubance (dist). The units for
 these variables are listed in "Variable_unit.xlsx". 
description: R programs
description: # Towards a mechanistic understanding of variation in aquatic food chain
 length revealed by meta-analysis
 ## Description of the data
 and file structure We collected a large empirical dataset of changes in
 food chain length (FCL) in response to ecosystem size, resource
 productivity and disturbance respectively, compiled from 30 published
 papers (see "References.docx"). This data set includes 36
 empirical cases relating to ecosystem size, 36 cases relating to resource
 productivity, and 16 cases relating to disturbance. We measure the FCL
 response to these variables using the log response ratio (LRR). All these
 LRR values are listed in the file "Empirical dataset": namely
 "LRR_Ecosystem size.xlsx", "LRR_Resource
 productivity.xlsx" and "LRR_Disturbance.xlsx". We also
 compiled the empirical data (see
 "Empirical_food_chain_data.csv") for both one- and two-way model
 analysis, where three variables are included: ecosystem size (size),
 resource productivity (resource), and disturbance (dist). The units for
 these variables are listed in "Variable_unit.xlsx". ##
 Sharing/Access information n/a ## Code/Software n/a