Molecular phylogeography reveals an antitropical distribution and local diversification of Solenogyne (Asteraceae) in the Ryukyu Archipelago of Japan and Australia

Abstract

An antitropical distribution represents an intriguing disjunction, in which a given species or sister lineages occupy regions north and south of the tropics but are absent from the intervening areas. Solenogyne mikadoi endemic to the Ryukyu Archipelago is regarded as an Australian element. Testing the phylogenetic relationship with Australian congeners and discussing the onset timing and causes of the disjunction would potentially enhance the understanding of antitropical distribution. A nuclear ribosomal DNA phylogeny was reconstructed using Bayesian and most parsimonious criteria with allied genera. Solenogyne was monophyletic and clustered with Lagenophora huegelii endemic to Australia, indicating the antitropical distribution and Australian origin of Solenogyne. Multispecies coalescent analysis based on nuclear ribosomal DNA and chloroplast DNA indicated the divergence of S. mikadoi and Australian congeners in the Plio-Pleistocene. Phylogenetic network analyses suggested that the ancestral lineage of S. mikadoi first colonized the southernmost island in the archipelago and then dispersed northward. The migration to the archipelago likely followed the flourishing of Solenogyne in open vegetation communities that radiated in south-eastern Australia during the late Pliocene. This disjunction might arise through long-distance dispersal across the tropics or, alternatively, through extinction in the tropics as a result of unsuitably high temperatures during climate oscillation and/or competitions from diverse tropical flora surviving since the early Tertiary.

A new family placement for Australian blue squill, Chamaescilla: Xanthorrhoeaceae (Hemerocallidoideae), not Asparagaceae

“…Anti-tropical relationships (where the same or sister taxa are absent from tropical regions, but are found to the north and south) are less common, but some examples occur between temperate Australia and mainland Asia-Japan. Among these taxa, older dispersal events are inferred in Sapindaceae (30-60 mya; Buerki et al 2011) and Apiaceae (46-71 mya; Calviño et al 2016); more recent dispersal events are inferred in Cucumis Linnaeus (1753bLinnaeus ( : 1011 in Cucurbitaceae (2-10 mya; Sebastian et al 2010), Solenogyne Cassini in Cuvier (1828: 174) in Asteraceae (0.9-4 mya; Nakamura et al 2012) and within Australian Poa sect. Brizoides Pilger ex Potztal (1969: 472) (1.4-6 mya; Birch et al 2014).…”

Demographic histories of adaptively diverged riparian and non-riparian species of Ainsliaea (Asteraceae) inferred from coalescent analyses using multiple nuclear loci

“…macroclinidioides , which coexist on Okinawa, had no fixed nucleotide differences, and they were not clustered separately. A previous study demonstrated the origin of the flood-resistant riparian species Solenogyne mikadoi , an endemic species in the Ryukyu Islands (Nakamura et al [31]). It showed that the divergence between Solenogyne mikadoi and the other Solenogyne species with disjunct distributions in southeastern Australia dated back several million years.…”

Nuclear and plastid DNA data confirm that Sedum tosaense (Crassulaceae) has a disjunct distribution between Pacific mainland Japan and Jeju Island, Korea

“…Several disjunct distributions in seed plants have been confirmed by molecular evidence, such as between North and South America (e.g., Spalik et al 2010;Popp et al 2011), between East Asia and North America (e.g., Huang et al, 2013), between Japan and Australia (e.g., Nakamura et al 2012;Kokubugata et al 2012), and between the Japanese Mainland and Taiwan (e.g., Mitsui et al 2008).…”