Environmental factors contribute to the formation and maintenance of the contact zone observed in deciduous broad-leaved tree species in Japan

Abstract

Contact zones are defined as areas where populations from different refugia meet during a postglacial expansion and distinct DNA lineages are mixedly distributed. In Japan, contact zones of various plants and animals were reported from the Kinki-Chugoku region. These contact zones appear to be maintained without any drastic topographic barriers such as those observed in the Alps and Pyrenees Mountains. In this study, the mechanisms underlying the formation and/or maintenance of these contact zones were investigated using six deciduous broad-leaved tree species (Carpinus laxiflora, C. tschonoskii, C. japonica, Magnolia obovata, Padus grayana, and Euonymus oxyphyllus). First, the precise location of the contact zones was examined by intensive genetic analysis of the six species. Second, the relationships between the geographic location of the contact zone and various environmental factors, including climate and topography, were investigated by generalized additive models to reveal the mechanisms of the formation and maintenance of the contact zones. As a result, four of the six examined plant species clearly showed a geographically common contact zone in Hyogo Prefecture and its adjacent areas. The results of the generalized additive models indicate that the pattern of low habitat suitability estimated by ecological niche modeling was the most important factor for determining the location of the common contact zone. These results suggest that areas with low habitat suitability in Hyogo Prefecture restrict the migration and gene flow of the four species in this region, and thus, they maintain the pattern of the contact zones. This study suggests that there are major effects of habitat suitability on the formation and maintenance of the contact zones.

Phylogeographic analysis of the East Asian goldenrod (Solidago virgaurea complex, Asteraceae) reveals hidden ecological diversification with recurrent formation of ecotypes

“…4). Reflecting the geographic arrangement of the archipelago, intraspecific lineages of temperate species are often reported to be differentiated along a north-south axis (Okaura et al, 2007;Sakaguchi et al, 2011;Sugahara et al, 2011;Clark et al, 2015;Tono et al, 2015). In the case of S. virgaurea complex, the demographic model, which suggested that the northern and southern lineages split first and then admixed in the central part of the island chain, was selected to account for genetic variation in the Japanese Archipelago.…”

Long-term persisting hybrid swarm and geographic difference in hybridization pattern: genetic consequences of secondary contact between two Vincetoxicum species (Apocynaceae–Asclepiadoideae)

“…The Japanese Archipelago is thought to have been free of massive ice sheets during the last glacial maximum (LGM) with the exception of some high altitude areas [ 23 ]. Previous phylogenetic studies showed that the postglacial range expansion process may have caused secondary contact between formerly isolated lineages of Fagus crenata [ 24 ], Aesculus turbinata [ 25 ], Padus grayana , Euonymus oxyphyllus , Magnolia obovata , Carpinus tschonoskii , C. japonica , C. laxiflora [ 26 ], Platycrater arguta [ 27 ], Rubus palmatus, and R. grayanus [ 28 ]. Two ecologically distinct species of Vincetoxicum (Apocynaceae-Asclepiadoideae), V. atratum (Bunge) Morren et Decaisne and V. japonicum Morren et Decne., provide a suitable study system.…”

2016 Awards in the Journal of Plant Research

“…It is generally accepted that contact zones could be formed due to geographical factors such as the Alps and Pyrenees Mountains, but no such geographical factors have been recognized in the contact zone of Hyogo Prefecture. Tono et al (2015) theoretically address the question about the formation of contact zones in Hyogo Prefecture, using generalized additive models considering various environmental factors including climate and topography. The results indicate that "the pattern of low habitat suitability estimated by ecological niche modeling was the most appropriate for determining the location of the common contact zone", demonstrating its excellence by proposing a new global concept in the field of botanical geography.…”