Allozyme Variation and the Genetic Structure of Populations of Trochodendron aralioides, a Monotypic and Narrow Geographic Genus

Abstract

Allozyme diversity was analyzed to determine the genetic structure of populations of Trochodendron araliokles Siebold 81 Zucc., a primitive angiosperm that is insectpollinated, has wind-dispersed seeds and grows only in eastern Asia. Nineteen populations were analyzed, including 16 from Ta'wan, two from the main islands of Japan and one from lriomote island in the Ryukyu Islands. Genetic variability (0.133) at the species level was more similar to that of a narrow geographic species than an endemic species. Based on genotype frequencies, mating within populations was non-random (Fs=O.O65) and there was significant genetic differentiation (FsT= 0.164) among populations. Genetic diversity was largely within, rather than among, populations (Hs= 0.132, 85;14°h). Bisexual flowers of T, araliohs exhibit synchronized dimorphism. The protogynous and protandrous morphs are self-incompatible, which probably promotes outcrossing and contributes to the huh levels of heterozygosity within populations. Using a maximum likelihood tree, populations of T. aralioMes were separated into two distinct clusters Japan and Taiwan/ lriomote island. Populations of T, aralioicbs on lriomote island and in northern Taiwan exhibited a high degree of genetic similarity. The isolation-by-distance model does not fit populations in Taiwan, but suitably describes the relationship between populations of T. ara/ioides in Japan and Taiwan.

Genetic population structure of the wind‐pollinated, dioecious shrub Juniperus communis in fragmented Dutch heathlands

“…2001). In species that are insect‐pollinated, but have wind‐dispersed seeds, the differentiation among populations is, in general, more pronounced (Fore & Guttman 1999; Wu et al . 2001; Rusanen et al .…”

Phylogeography of Trochodendron aralioides (Trochodendraceae) in Taiwan and its adjacent areas

“…Trochodendron aralioides , the only extant member of Trochodendron , is distributed in Japan, the Ryukyus and Taiwan (Wu et al. , 2001).…”

“…The flowers are dichogamous, self‐incompatible and obligatorily xenogamous (Chaw, 1992). Two main population groups were distinguished in T. aralioides based on the analyses of genetic variation of allozyme and sequence of internal transcribed spacer nrDNA (Wu et al. , 2001; Wu, 2001).…”

Cytological studies on the eastern Asian family Trochodendraceae

“…, 2007), embryology (Pan et al. , 1993) and allozymes (Wu et al. , 2001), but their systematic position is still disputed.…”

“…The position of Trochodendron and Tetracentron is pivotal in angiosperm phylogeny and many different types of research have been conducted on them including phylogeography (Huang et al, 2004;Huang & Lin, 2006), chemical components (Wu et al, 2000), anatomy (Wu, Lin & Li, 1993;Chen et al, 2007), embryology (Pan et al, 1993) and allozymes (Wu et al, 2001), but their systematic position is still disputed. As two independent families, the Tetracentraceae and Trochodendraceae were placed between the magnoliids and the hamamelids, although the two genera Trochodendron and Tetracentron were considered to be closely related (Chen et al, 2007).…”