Does density-induced stress promote density-dependent reproduction in root voles? Two field experiments
Guozhen Shang1, 2,#, Shouyang Du3, #, Yanbin Yang4, #, Yan Wu5, Yifan Cao1, 2, Jianghui Bian1, 2
1 Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810001, China
2 Qinghai Key Laboratory of Animal Ecological Genomics, Xining,810001, China
3 College of Animal Science and Veterinary Medicine, Henan Institute of Science and Technology, Xinxiang 453003, China
4 College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450002, Henan 45000, China
5 School of Life and Environment Sciences, Hangzhou Normal University, Hangzhou 310012, China.
# These authors contributed equally to this paper.
Running Head: Density dependence and density stress
Correspondence authors: Jianghui Bian, Email: bjh@nwipb.cas.cn; Yan Wu, Email: wuyanqh@163.com.
Abstract: Density dependence in reproduction plays an important role in stabilising population dynamics via immediate negative feedback from population density to reproductive output. Although previous studies have shown that density dependence is associated with strong spacing behaviour and social interaction between individuals, the proximal mechanism for generating density-dependent reproduction remains unclear. In this study, we investigated the effects of density-induced stress on reproduction in root voles. Founder population enclosures were established by introducing six (low density) and 30 (high density) adults per sex into per enclosure (four enclosures per density in total) during the breeding season from April to July 2012 and from May to August 2015. Faecal corticosterone metabolite (FCM) levels, reproductive traits (recruitment and the proportion of reproductive condition), and founder population numbers were measured following repeated live-trapping in both years. The number of founders was negatively associated with recruitment rates and the proportion of reproductive conditions, displaying a density-dependent reproduction. FCM level was positively associated with the number of founders. The number of founder females indirectly affected the proportion of reproductive females in 2012 and recruitment in 2015 through their FCM levels; the effect of the number of male founders on the proportion of reproductive condition was mediated by their FCM level in 2012, but the effect was not found in 2015. Our results showed that density-induced stress affected density-dependent reproduction and that density-induced stress is one ecological factor generating density-dependent reproduction.
Keywords: density-dependence, density, stress, FCM level, reproduction, root vole