Successional changes in trophic interactions support a mechanistic model of post-fire population dynamics
Models based on functional traits have limited power in predicting how animal populations respond to disturbance because they do not capture the range of demographic and biological factors that drive population dynamics, including variation in trophic interactions. I tested the hypothesis that successional changes in vegetation structure, which affected invertebrate abundance, would influence growth rates and body condition in the early-successional, insectivorous gecko Nephrurus stellatus. I captured geckos at 17 woodland sites spanning a succession gradient from 2 to 48 years post-fire. Body condition and growth rates were analysed as a function of the best-fitting fire-related predictor (invertebrate abundance or time since fire) with different combinations of the co-variates age, sex and location. Body condition in the whole population was positively affected by increasing invertebrate abundance and, in the adult population, this effect was most pronounced for females. There was strong support for a decline in growth rates in weight with time since fire. The results suggest that increased early-successional invertebrate abundance has filtered through to a higher trophic level with physiological benefits for insectivorous geckos. I integrated the new findings about trophic interactions into a general conceptual model of mechanisms underlying post-fire population dynamics based on a long-term research programme. The model highlights how greater food availability during early succession could drive rapid population growth by contributing to previously reported enhanced reproduction and dispersal. This study provides a framework to understand links between ecological and physiological traits underlying post-fire population dynamics.
KeywordsDisturbance Fire management Functional traits Habitat accommodation model Pyrodiversity
This paper is dedicated to the memory of Professor C. Michael Bull (1947–2016) and Mr Dale Burzacott (1958–2017) who ran a productive, honest and friendly research laboratory together for over 30 years. They made substantial contributions to lizard population ecology and will be missed as mentors and friends. Don Driscoll and C. Michael Bull were involved in the design of a broader project during which data for this project were collected. Over 40 volunteers were involved in field work, particularly Samantha Blight, Simone Dalgairns, Juliana Lazzari, Kevin Mayes and Catherine Whitehead. Joe Tilley and the South Australian Department of Environment, Water and Natural Resources (DEWNR) provided field support. The research was funded by the Australian Research Council (LP0776604), Native Vegetation Council of South Australia, DEWNR, Wildlife Conservation Fund, Sir Mark Mitchell Research Foundation, Lirabenda Endowment Fund, Ecological Society of Australia and Australian National University.
Author contribution statement
ALS conceived, designed and executed this study and wrote the manuscript. No other person is entitled to authorship.
Compliance with ethical standards
All applicable institutional and national guidelines for the care and use of animals were followed. I followed the Australian code for the care and use of animals for scientific purposes and worked under scientific (S25589 Government of South Australian) and animal ethics (E256 Flinders University) permits.
Data supporting this article have been uploaded as part of the Electronic Supplementary Material.
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