Embryo to seed length ratio and embryo to seed surface ratio data

To demonstrate the bias of data availability towards non-tropical species, we compiled data on embryo length to seed length ratio and embryo to seed surface ratio for 1295 spermatophyte species. These data were obtained mainly from pictures or drawings available in the main literature sources dealing with the internal morphology of seeds (e.g., Martin, 1946; RBG Kew, 2021 [SID]; Watson & Dallwitz, 1992) and from measurements on living material (Vandelook et al., 2012; Vandelook et al., 2021). Care was taken that the measurements were taken on transversal sections of seeds at the moment of ripeness, which had maximal embryo surface area. The embryo to seed length ratio was calculated by measuring total embryo length and dividing this by the length of the seed, measured from the inside of the seed coat, along the longest axis. The embryo to seed surface area was calculated by dividing the embryo area by the area of the embryo plus endosperm and perisperm. In case of curved or coiled embryos, the lengths of different segments were summed. All occurrence coordinates for these species were downloaded from GBIF (GBIF download DOI:10.15468/dl.mat4zv). Using these coordinates, we calculated the percentage of occurrences in the tropics (between the Tropic of Cancer and the Tropic of Capricorn) and outside of the tropics for each species. Duplicate coordinates within a species were removed prior to calculation.为论证数据可用性对非热带物种的偏向性，我们收集了1295种种子植物（Spermatophyte）的胚长/种子长比值与胚表面积/种子表面积比值数据。上述数据主要来源于针对种子内部形态的核心文献中的图片或绘图（例如Martin, 1946；英国皇家植物园邱园（RBG Kew）, 2021 [SID]; Watson & Dallwitz, 1992），以及活体材料的实测数据（Vandelook等, 2012; Vandelook等, 2021）。研究过程中严格把控测量标准：所有测量均取自成熟时刻的种子横切面，此时胚表面积达到最大值。胚长与种子长的比值通过以下方式计算：测量胚的总长度，再除以从种皮内侧沿最长轴测得的种子长度。胚表面积与种子表面积的比值则通过将胚表面积除以胚、胚乳及外胚乳的总面积计算得到。若胚呈弯曲或盘绕形态，则将各段长度求和后再进行相关比值计算。所有物种的分布坐标均从全球生物多样性信息设施（GBIF, Global Biodiversity Information Facility）下载，下载DOI为10.15468/dl.mat4zv。基于这些分布坐标，我们计算了每个物种在热带（北回归线与南回归线之间）以及非热带区域的出现占比。在计算前，已移除同一物种内的重复分布坐标。