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