2026-10-28 テキサス大学オースティン校（UT Austin）
米テキサス大学オースティン校の研究者らは、北極圏のツンドラに生息するコモリグモの食物源が、季節や生息環境、生物の大きさによって変化することを明らかにした。研究チームは、アラスカ北部の複数地点で調査を行い、必須アミノ酸の炭素安定同位体フィンガープリンティングという手法を用いて、クモの体内に取り込まれた炭素が植物、菌類、細菌など、どの由来のエネルギーに結びつくかを追跡した。その結果、植生の生産性が低い場所や夏の初期には、クモは菌類に由来するエネルギーにより強く依存する一方、夏の盛りには植物由来のエネルギーへの依存が高まることが分かった。また、大型のクモほど植物由来の炭素への依存度が高かった。北極圏では温暖化によって夏が長くなり、クモの成長や繁殖、個体数が変化する可能性がある。こうした食性の変化は、植食者や分解者を介した食物網に影響し、植物の成長や有機物の分解など、生態系の機能を変える可能性がある。
＜関連情報＞
- https://news.utexas.edu/2026/10/28/spooky-science-arctic-wolf-spiders-eating-habits-are-shifting-over-time/
- https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.70362
季節変動の激しい生態系では、広食性捕食者への炭素の流れは、植物由来資源と菌類由来資源の間で変化する en
Nevo Sagi, Philip J. Manlick, Anejelique J. Martinez, Leslie J. Potts White, Seth D. Newsome, Amanda M. Koltz
Journal of Animal Ecology Published: 21 October 2026
DOI:https://doi.org/10.1111/1365-2656.70362
Abstract
- Animals influence biogeochemical processes by consuming other organisms, transferring energy from basal resources up the food chain. Energy is routed through plant, fungal and bacterial channels, and the relative importance of these pathways can shift across space and time. Variation in these pathways may be particularly pronounced in highly seasonal environments where resource availability fluctuates throughout the year.
- Spatiotemporal variation in the transfer of plant- versus microbial-derived energy to higher trophic levels is poorly understood but can affect bottom-up and top-down processes. For example, seasonal shifts in herbivore versus microbivore availability (bottom-up) may alter prey choice by generalist-feeding predators and lead to changes in top-down predator control on primary production and decomposition.
- We tested how spatiotemporal variation in primary production influences the use of different energy channels by a widely distributed generalist invertebrate predator in the Arctic tundra. We sampled wolf spiders across four sites spanning a productivity gradient in the Alaskan Arctic during peak summer and on a weekly basis at one focal site throughout the growing season. Using essential amino acid (EAA) carbon isotope (δ13C) fingerprinting, we traced the flow of plant-, bacterial- and fungal-derived EAAs to spiders and quantified the use of plant- versus microbe-based energy channels between sites and across summer.
- Wolf spiders were associated with more plant- and less fungal-derived carbon assimilation when larger or collected from sites with higher normalized difference vegetation index (NDVI). Across the growing season, spiders shifted from primarily assimilating fungal-based resources in early summer to plant-derived resources in late summer, aligning with seasonal increases in NDVI.
- These patterns demonstrate spatiotemporal variation in carbon flow through different energy channels and suggest subsequent top-down predator effects may also vary with basal resource availability. Our findings also suggest wolf spider body size may predict whether predation indirectly influences primary production or decomposition. As climate change alters seasonality, resource dynamics and invertebrate body sizes, these insights provide a basis for predicting spatiotemporal variation in predator impacts on ecosystem processes. Finally, our work demonstrates the utility of compound-specific stable isotope analysis for integrating ecological and biogeochemical theory through the conceptual lens of zoogeochemistry.
