Comparative genetic structure betweenSedum ussurienseandS. kamtschaticum(Crassulaceae), two stonecrops co‐occurring on rocky cliffs

Abstract

• Premise of the study: Geographic isolation due to discontinuities of suitable habitat may have significant effects on the genetic structure of plant populations. Even within a few kilometers, physical barriers to gene flow may lead to considerable genetic differentiation among populations.• Methods: Sedum ussuriense is a boreal species that in Korea occurs only in four valleys separated by mountain ranges in Juwangsan National Park and its vicinity (a range of ∼15 km). Its congener S. kamtschaticum, by contrast, co-occurs in the four valleys but also on the intervening mountains. Using 12 allozyme loci, we comparatively assessed genetic variability and structure in 12 population pairs of the two stonecrops.• Key results: While we found high and comparable levels of within-population genetic variation for the two species, among-population divergence was significantly higher in S. ussuriense (F = 0.261 vs. F = 0.165). Sedum ussuriense also showed a much higher percentage of among-valley variation (19%) than S. kamtschaticum (4%).• Conclusions: High levels of genetic diversity in the two Sedum species are consistent with the previous hypothesis that mountains of the Korean Peninsula served as glacial refugia for many boreal species. Given that the two congeners have similar life-history traits, the lower among-population differentiation in S. kamtschaticum is attributable to its higher abundance and more continuous distribution in the study area. This study confirms the central role of geographic isolation in the genetic structure of plant species even at very small scales.

Notes on genetic variation in Sedum sarmentosum (Crassulaceae): Implications for the origin of southern Korean populations

“…With this in mind, we selected Sedum polytrichoides Hemsl., an additional stonecrop that is also present in the study area, to get additional insights into the previous results by Chung et al (2014b). The species is somewhat common along the four valleys, but several populations also occur on rocks in mountains and hillsides between valleys.…”

“…The species is somewhat common along the four valleys, but several populations also occur on rocks in mountains and hillsides between valleys. The three species are insect-pollinated (Ku et al, 2011;Chung et al, 2014b;M. Y. Chung, pers.…”

“…We collected samples from 10 populations of S. polytrichoides (n = 243 samples) (Table 1) at the same sites studied by Chung et al (2014b) with the exception of two populations (JW-3 and HO-2) in JNP and its vicinity ( Fig. 1).…”

“…Note that S. polytrichoides does not occur at the two populations enclosed by boxes (JW-3 and HO-2), but S. kamtschaticum and Hylotelephium ussuriense grow there (Chung et al, 2014b).…”

“…co-occurs in the four valleys but also on the intervening mountains in JNP and its vicinity. To understand better the effects of physical isolation on the genetic structure of plant populations in the study area, recently we comparatively assessed genetic variability and structure in 12 population pairs (three sympatric populations per valley for each species) of the two stonecrops (Chung et al, 2014b). The authors found high and comparable levels of within-population genetic variation for the two species, although among-population difference was significantly higher in H. ussuriense than in S. kamtschaticum (F S T = 0.261 vs. F S T = 0.165).…”