升温对北草蜥雌体繁殖、卵孵化及幼体特征的影响

在围栏条件下,比较升温和对照处理北草蜥(Takydromus septentrionalis)繁殖、卵孵化及幼体特征的差异,以揭示升温对其繁殖生活史特征的作用。升温处理对北草蜥母体体温有显著影响,但并不影响其繁殖输出。升温显著影响卵孵化期和幼体的运动能力,但不影响幼体大小等形态特征。升温条件下孵出的幼体运动能力较弱。结果表明,北草蜥母体能耐受短期的环境增温,维持相对恒定的繁殖输出;升温能影响幼体的功能表现,进而可能改变后代适合度。

The effects of warming on female reproduction, egg incubation and hatchling traits in the northern grass lizard, Takydromus septentrionalis

Abstract: The potential influence of climate warming on organisms has long been acknowledged, but experimental tests of climate on life history traits of vertebrates are rare. Here we carried out an experiment to test the effects of increased ambient temperature on reproductive life history and hatchling traits of the northern grass lizard (Takydromus septentrionalis, Lacertidae). Adult northern grass lizards (60 females and 28 males) were captured from Wenzhou County of eastern China in early April, the beginning of reproductive season. After the lizards were measured (snout-vent length and body mass), they were randomly assigned and maintained in warming or control outdoor enclosures (1.5m diameter). We provided two additional 100w infrared lamps in each warming enclosure to increase the ambient temperature. Ambient temperatures in the enclosures were recorded using temperature data-loggers (ibuttons, MAXIM Integrated Products Ltd, USA). Body temperatures of the females were monitored once a week using an electronic contact thermometer. Clutches of eggs laid by the females were collected to determine female reproductive traits including clutch frequency, clutch size, clutch mass, and egg mass. Eggs from the females were incubated at warming or control treatments in a split-clutch design. Young lizards were weighed and measured (snout-vent length, tail length and head width) within 24 h of hatching and their locomotor performance was then measured at 30 C. Repeated measures ANOVA was used to compare the between-treatment difference in body temperatures. ANOVA or ANCOVA was applied to examine the influence of the warming treatment on reproductive traits (with a covariate of female snout-vent length) and hatchling traits (with a covariate of initial egg mass). The mean ambient temperature in warming enclosures was 2 oC higher than that in control enclosures during the experimental period. Similarly, the mean temperature of egg incubation in the warming treatment was 2.5 oC higher than that of the control. Body temperatures were significantly affected by the warming treatment, and were 1.1 oC higher for females in the warming enclosures than in the control enclosures. All female reproductive traits measured in the current study were unaffected by the warming treatment. Hatchlings from eggs incubated in the warming treatment hatched sooner, but had decreased locomotor performance than their siblings from the control treatment. However, hatching success and hatchling body size did not differ between the treatments. These results indicate that (1) female T. septentrionalis can regulate body temperature to alleviate the impact of warming, given that the difference of body temperature between the treatments was smaller than that of ambient temperature, (2) females can maintain a relatively constant reproductive output relatively constant when facing short-term temperature increases; (3) temperature increases may decrease the functional performance of hatchlings, and potentially impose negative effects on offspring fitness.