Department of Ecology and Evolution, Le Biophore, University of Lausanne, 1015 Lausanne, Switzerland.
J Therm Biol. 2022 Feb;104:103197. doi: 10.1016/j.jtherbio.2022.103197. Epub 2022 Jan 26.
A variety of responses to climate seasonality have evolved by small mammals, including adjustments of the basal rate of metabolism (BMR) and the use of daily or seasonal torpor (here referred to as short-bout and long-bout torpor). The seasonal variation of their BMR is known to depend mainly on the concurrent variation of body mass, but it should also be affected by structural and functional changes occurring within the body that could depend on the expression of torpor. Thus it was hypothesized that BMR seasonality is related to the expression of torpor at an interspecific level. Seasonal BMR and body mass data were gathered from the literature and phylogenetic comparative analyses were done to test this hypothesis among mammals of less than 1 kg. BMR seasonality (dBMR) was quantified as the log-transformed ratio of the mean whole-animal BMR reported for the period P (autumn-winter) over that for the period P (spring-summer). Predictors were the seasonal body mass adjustment (dm), mean body mass (m) and torpor expression (TO, a three-level factor: no torpor, short-bout torpor, long-bout torpor). The seasonal variation of BMR was significantly related to dm but also to TO. Accounting for dm, species expressing long-bout torpor, but not those entering short-bout torpor, collectively exhibited a lower dBMR than species not entering torpor. Fat storage and use by species entering long-bout torpor, alone, could not explain their lower dBMR, as the TO:dm interaction was not significant. The low dBMR of species entering long-bout torpor may result from their collective tendency to down-regulate more strongly costly visceral organs during P. The dBMR of the different TO categories overlapped appreciably, which highlights our still limited knowledge of the BMR seasonality among small mammals.
各种对气候季节性的反应已经在小型哺乳动物中进化出来，包括基础代谢率（BMR）的调整和日常或季节性休眠（这里称为短期和长期休眠）的使用。已知它们的 BMR 季节性主要取决于体重的同时变化，但它也应该受到体内发生的结构和功能变化的影响，这些变化可能取决于休眠的表达。因此，有人假设 BMR 季节性与种间休眠的表达有关。从文献中收集了季节性 BMR 和体重数据，并进行了系统发育比较分析，以检验这一假说在体重小于 1 公斤的哺乳动物中是否成立。BMR 季节性（dBMR）被量化为报告的整个动物 BMR 在季节 P（秋冬）期间的对数与季节 P（春夏）期间的对数之比。预测因子是季节性体重调整（dm）、平均体重（m）和休眠表达（TO，一个三水平因子：无休眠、短期休眠、长期休眠）。BMR 的季节性变化与 dm 显著相关，但也与 TO 相关。在考虑 dm 的情况下，表现出长期休眠的物种，而不是那些进入短期休眠的物种，其 dBMR 比不进入休眠的物种低。仅进入长期休眠的物种的脂肪储存和利用，不能解释其较低的 dBMR，因为 TO:dm 相互作用不显著。进入长期休眠的物种的低 dBMR 可能是由于它们在 P 期间集体倾向于更强烈地下调昂贵的内脏器官。不同 TO 类别的 dBMR 重叠明显，这突出表明我们对小型哺乳动物中 BMR 季节性的了解仍然有限。
