The spatial distributional pattern of seed plants and its future advances

The geographic distribution of organisms has been a central theme in biology since the time of Darwin and Wallace (Darwin, 1859; Wallace, 1876; Good, 1974; Raven and Axelrod, 1974; Wen et al., 2013). As biogeography advances, increasing attention has been paid to understanding distributional patterns and the processes shaping them (Wen et al., 2010; Ficetola et al., 2017; You et al., 2024). In phytogeography, two major frameworks have emerged: the flora-based approach, which focuses on assemblages of species in defined regions, and the taxon-based approach, which centers on individual lineages and their spatial evolution. While the flora-based approach has recently gained grounds as a tool for regionalization (Liu et al., 2023; Minev-Benzecry and Daru, 2024), the taxon-based method—originally reliant on morphological traits and geographic distributions (Raven and Axelrod, 1974; Wu, 1991; Wu et al., 2003)—has expanded greatly through molecular phylogenetics and phylogenomics. This expansion has enabled detailed biogeographic reconstructions at the family, genus, and species levels, shedding light on vegetation evolution (Hai et al., 2022), floristic formation (Nie et al., 2016; Chen et al., 2018), and broader Earth history reconstruction (Ding et al., 2020). Nevertheless, large-scale, taxon-based analyses at higher taxonomic levels remain comparatively under-explored. In a recent issue of the Journal of Integrative Plant Biology, Huang et al. (2025) addressed this gap by assembling the most comprehensive global dataset to date on extant seed plant families. By integrating current taxonomic frameworks with distribution, biogeographic origins, and formation time and mechanisms, they constructed SSES. This novel framework is built upon unsupervised machine learning methods—most notably K-means clustering—and for the first time classifies 429 seed plant families into 18 distribution types, six distribution supertypes, and three major floristic elements: cosmopolitan, tropical, and temperate. The SSES offers a systematic synthesis that captures macro-scale distributional regularities, providing new insight into how similar spatial patterns may have arisen from comparable formation processes and mechanisms. This study also offers a new paradigm for conducting biogeographic research by combining computational techniques with large-scale evolutionary data. From a spatial patterning perspective, Huang et al. (2025) integrated species richness of 429 spermatophyte families across continents and proposed the SSES, a novel framework grounded in family-level distribution centers and origin locations, while minimizing anthropogenic influences. The resulting three-tiered classification—comprising distribution types, supertypes, and floristic elements—sets a new standard for macro-scale floristic analyses. Although the SSES provides a foundational topology for exploring the spatial patterns of global spermatophytes, further refinement is needed to enhance its resolution. Regarding the spatial evolution, spermatophyte families were sampled in the most comprehensive manner to date with respect to their place of origin, formation time, and formation factors across the six distribution supertypes based on Huang et al. (2025) (Figure 1). Nevertheless, the number of families sampled for each distribution supertype or type remains relatively low compared with the global total for each category (also see Figure 2). Given that family-level sampling is generally more complete than that at the genus level, this data gap underscores the urgent need to expand biogeographic studies at both levels, particularly for underrepresented groups. Huang et al. (2025) also investigated the origin and formation of corresponding distribution types of 429 extant spermatophyte families, involving relevant fossil evidence. For certain families—such as Juglandaceae, Nelumbonaceae, and Zamiaceae—fossil-based analyses were conducted. Yet a more comprehensive understanding of global spermatophyte spatial evolution will require the incorporation of extensive fossil or palaeobotanical data within a multidisciplinary framework of geology, ecology, phylogenomics, and computational methods, especially with the utilization of the model clades (Donoghue and Edwards, 2019) in the future. The SSES by Huang et al. (2025) sets the important foundation for testing the global floristic and biogeographic assembly of plants and represents a major step forward in global biodiversity synthesis of seed plant evolution. Number of spermatophyte families with known origin location, formation time, and formation factors of 18 distribution types, based on Huang et al. (2025) The family number in parentheses is three times the actual number of families in the category, as the number on the left represents the sum of the numbers on formation factor, formation time, and origin location. The 18 distribution types are: Ⅰ. Cosmopolitan, Ⅱ. Pantropic, Ⅲ. Tropical Asia and tropical America disjuncted, Ⅳ. Old World Tropics, Ⅴ. Tropical Asia to tropical Australasia, Ⅵ. Tropical Asia to tropical Africa, Ⅶ. South Atlantic disjuncted, Ⅷ. Tropical Asia, Ⅸ. New World Tropics, Ⅹ. Tropical Australasia, Ⅺ. Tropical Africa, Ⅻ. North temperate, XIII. East Asia and North America disjuncted, XIV. Pan-Mediterranean diffused, XV. East Asia, XVI. North America, XVII. South temperate, XVIII. North and South temperate disjuncted. I thank Professor Hang Sun and Dr. Xianhan Huang for their discussions. The author declares no conflicts of interest. The author J.W. is solely responsible for all content in this article.