| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（口頭発表） N02-03 （Oral presentation）

#### 非対称な気候応答に基づく祖先ニッチの再構築：マカク属（Macaca）の事例研究
Ancestral niche reconstructions with asymmetric climatic responses: a case study for the genus Macaca

*高根太朗, Jamie M. KASS（東北大学）
*Taro TAKANE, Jamie M. KASS（Tohoku Univ.）

Reconstructing how species’ geographic distributions responded to past climate change is essential for understanding macroevolutionary diversification. This is because lineages diversify, persist, or go extinct within the bounds of the environments that were historically available to them. The monkey genus Macaca provides an ideal system to explore this problem: major Asian lineages diversified around the late Pliocene, but fossil occurrences from southern China and adjacent regions are strikingly sparse. This “fossil gap” raises a key question that is common in deep-time studies more broadly—did Macaca truly have a restricted late Pliocene distribution, or does the apparent absence mainly reflect uneven sampling and preservation rather than genuine biogeographic limits? A major obstacle to hindcasting past distributions is that ancestral niche reconstruction often assumes symmetric (Gaussian) environmental responses, despite the prevalence of asymmetric tolerance and performance curves. Symmetry assumptions can be especially consequential for reconstructing range limits, because distribution edges are frequently determined by steep, one-sided constraints (e.g., cold- or heat-limited boundaries) rather than by gradual declines around an optimum. Recent methods have attempted to accommodate asymmetry by treating distribution “shape parameters” (e.g., skewness) as evolving traits, but such parameters can be unstable to estimate and are often difficult to interpret ecologically across taxa. To address this, I developed an ecologically interpretable workflow that represents asymmetric niche structure using biologically meaningful summaries. For each extant species, I derive predicted niche occupancy (PNO) profiles from ecological niche models (ENMs), fit skew-normal curves to these profiles, and summarize each response with three values: the mode and the lower and upper bounds of the 80% highest-density interval (HDI). This representation preserves key information about asymmetric limits while remaining comparable across species and amenable to phylogenetic reconstruction and paleoclimate projection. Applying this approach to Macaca indicates a persistent late Pliocene corridor of climatic suitability extending from northern India into China. This corridor remains highly suitable under both a warm phase (mid-Pliocene Warm Period; mPWP) and a cold phase (M2). This pattern highlights the possibility that long-term habitat persistence in this region through to the present supported the divergence of major Asian lineages, and that the scarcity of late Pliocene fossils in southern China may reflect uneven sampling and preservation rather than true absence of the genus.

日本生態学会