The Rapoport effect and the climatic variability hypothesis in Early Jurassic ammonites

The increase of species range size towards high latitudes, known as the Rapoport’s rule, remains one of the most debated and poorly understood macroecological patterns. Numerous studies have challenged both its universality and the main mechanism originally proposed to explain it, i.e. the climatic variability hypothesis. Here we study this pattern on a group of fossil marine organisms: the early Pliensbachian ammonites of the western Tethys. We further take into account the influence of the marked provincialism prevailing at that time, with a Mediterranean province (MED) and a Northwest European province (NWE) located on each side of a latitudinally-oriented palaeobiogeographic barrier. We find that only species from the NWE province display a Rapoport effect, whereas species from the more tropical MED province show a boundary effect and have larger range sizes in average. This dual pattern can be explained by an alternative climatic variability hypothesis that better captures latitudi...

物种分布范围大小向高纬度递增的现象，被称为拉波波特法则（Rapoport’s rule），仍是宏观生态学领域最具争议且尚未被充分阐明的格局之一。诸多研究既对其普适性提出了质疑，也对最初用以解释该现象的核心机制——气候变异性假说——发起了挑战。本研究针对一类化石海洋生物展开分析：西特提斯洋域早普林斯巴阶的菊石。我们进一步纳入了当时盛行的显著生物地理分区性的影响因素，彼时存在一道沿纬度走向的古生物地理屏障，将海域分隔为地中海生物省（MED）与西北欧生物省（NWE）。研究结果表明，仅西北欧生物省的物种呈现拉波波特效应；而来自更具热带特征的地中海生物省的物种则表现出边界效应，且平均分布范围更大。这种二元分布格局可通过修正后的气候变异性假说来解释，该假说更能贴合纬度……