Stable isotopes and radiocarbon assess variable importance of plants and fungi in diets of arctic ground squirrels
Stable isotopes and radiocarbon assess variable importance of plants and fungi in diets of arctic ground squirrels
复制标题
DOI：
10.1657/aaar0016-062
复制
发表时间：
2017-08-01
影响因子：
2
通讯作者：
Barnes, Brian M.
中科院分区：
文献类型：
--
作者：
Hobbie, Erik A.;Shamhart, Julee;Barnes, Brian M.
北极地松鼠（Urocitellus parryii）在冬眠期间主要依靠来自植物的膳食蛋白质来促进糖异生，然而真菌孢子可能是一个重要的，但被忽视的蛋白质来源。真菌水平取决于孢子体生产力，孢子体生产力因优势植物种类而异，在酸性土壤中比在非酸性土壤中更高。为了测试这些因素是否改变了真菌的消耗，我们使用稳定同位素研究了阿拉斯加北部Toolik（主要是潮湿的酸性冻土带）和Atigun（主要是潮湿的非酸性冻土带）两个地点的北极地松鼠饮食。放射性碳估计也可以表明真菌水平，因为外生菌根真菌吸收来自土壤的有机氮，其C-14水平高于目前的光合作用。我们测量了头发中的放射性碳，以及头发、粪便、外生菌根孢子囊、类谷粒和玉米粒中的δ C-13和δ N-15。图立克的粪便δ C-13和δ N-15含量高于阿提根，8月份图立克的粪便δ N-15含量增加，与产孢和粪便真菌孢子一致。混合模型表明，禾草素对Atigun毛发蛋白的贡献为64%，果穗为35%，孢子实为1%，而禾草素对Toolik毛发蛋白的贡献为37%，果穗为16%，孢子实为47%。酸性土壤在图利克比在阿提根与更高的孢子果产量和真菌有关。Atigun毛发的碳-14含量与大气中的二氧化碳相似，而Toolik毛发的碳-14含量较高，这与Toolik毛发的真菌消耗量较大一致。晚季孢子囊可能是某些松鼠的重要蛋白质来源，并可能提供外生菌根真菌吸收土壤有机氮的综合信号。
Arctic ground squirrels (Urocitellus parryii) rely primarily on dietary protein derived from plants to fuel gluconeogenesis during hibernation, yet fungal sporocarps may be an important, yet overlooked, protein source. Fungivory levels depend on sporocarp productivity, which varies with the dominant plant species and is higher on acidic than on non-acidic soils. To test whether these factors altered fungal consumption, we used stable isotopes to investigate arctic ground squirrel diets at two sites in northern Alaska, Toolik (primarily moist acidic tundra) and Atigun (primarily moist non-acidic tundra). Radiocarbon estimates can also indicate fungivory levels because ectomycorrhizal fungi assimilate soil-derived organic nitrogen whose C-14 levels are higher than current photosynthesis. We measured radiocarbon in hair and delta C-13 and delta N-15 in hair, feces, ectomycorrhizal sporocarps, graminoids, and dicots. Feces were higher in delta C-13 and delta N-15 at Toolik than at Atigun, and fecal delta N-15 increased in August at Toolik, coincident with sporocarp production and fungal spores in feces. Mixing models indicated that graminoids contributed 64%, dicots 35%, and sporocarps 1% to Atigun hair protein, whereas graminoids contributed 37%, dicots 16%, and sporocarps 47% to Toolik hair protein. Acidic soils appeared to correlate with higher sporocarp production and fungivory at Toolik than at Atigun. Atigun hair resembled atmospheric CO2 in C-14, whereas Toolik hair had higher C-14, consistent with greater fungal consumption at Toolik. Late-season sporocarps may be a key protein source for some squirrels and may provide an integrated signal of the soil organic nitrogen assimilated by ectomycorrhizal fungi.