Maternal stress can have long-term adverse consequences on immunocompetence and disease risk of off spring, and winter survival is a crucial demographic parameter in the life-history of an individual that can substantially aff ect northern rodent population dynamics. An understanding of the eff ects of maternal stress on winter survival of off spring may help identify mechanisms driving population fl uctuations of northern small mammals. Th us, we assessed the eff ects of maternal stress, resulting from high population densities, on winter survival of fi rst generation (F 1 ) and second generation (F 2 )
in root voles Microtus oeconomus . Replicate high- and low-density enclosed parental populations were established, from which we obtained F 1 generation that were used to establish new enclosed, equal-density populations. Th e adults of the high-density parental populations had higher corticosterone levels, an indication of physiological stress, than did those of the low-density parental populations. Over-winter survival of the F 1 generation voles from the low-density parental populations was greater than that of those from the high-density parental populations. Over-winter survival of F 2 generation
voles did not diff er between the two treatments. Our results suggest that maternal stress aff ected over-winter survival of fi rst generations but not second generations. Reduced immunocompetence, resulting from high population density stresses, transferred to off spring may be a factor in annual (winter) population declines. Because the eff ect is transitory, i.e. immunocompetence of F 2 voles is not aff ected, reduced immunocompetence resulting from high density stresses would not contribute to lengthy periods of low population densities that are characteristic of multi-annual population fl uctuations.
in root voles Microtus oeconomus . Replicate high- and low-density enclosed parental populations were established, from which we obtained F 1 generation that were used to establish new enclosed, equal-density populations. Th e adults of the high-density parental populations had higher corticosterone levels, an indication of physiological stress, than did those of the low-density parental populations. Over-winter survival of the F 1 generation voles from the low-density parental populations was greater than that of those from the high-density parental populations. Over-winter survival of F 2 generation
voles did not diff er between the two treatments. Our results suggest that maternal stress aff ected over-winter survival of fi rst generations but not second generations. Reduced immunocompetence, resulting from high population density stresses, transferred to off spring may be a factor in annual (winter) population declines. Because the eff ect is transitory, i.e. immunocompetence of F 2 voles is not aff ected, reduced immunocompetence resulting from high density stresses would not contribute to lengthy periods of low population densities that are characteristic of multi-annual population fl uctuations.
Th e minimum number known to be alive (MNKA) per
o.15 ha of (A) F 1 and (B) F 2 generations and (C) off spring populations
in root voles ( Microtus oeconomus ). Abbreviations for off -
spring populations are as in Values are means ( 1 SE) for the two
replicates within an off spring population. Repeated-measures
ANOVA showed statistically signifi cant eff ect of parental density
on F 1 generation from December to April (F 1,1 24.12,
p 0.039) .
o.15 ha of (A) F 1 and (B) F 2 generations and (C) off spring populations
in root voles ( Microtus oeconomus ). Abbreviations for off -
spring populations are as in Values are means ( 1 SE) for the two
replicates within an off spring population. Repeated-measures
ANOVA showed statistically signifi cant eff ect of parental density
on F 1 generation from December to April (F 1,1 24.12,
p 0.039) .
(Picture by Jiang-hui Bian)
The research has been published on Oikos,Volume 120, Issue 1, pages 47–56, January 2011.
Li Guoliang, Shi Junyou, Suo Yourui, Sun Zhiwei, Xia Lian, Zheng Jie, You Jinmao, Liu Yongjun