2.1.2. Analysis of the Components of the Families
Based on the species (including infraspecific taxa) richness of families, 5 family levels have been classified: large families containing more than or equal to 100 species; secondary large families containing from 50 to 99 species; medium families containing from 10 to 49 species; small families containing from 2 to 9 species; and single-species families containing only one species.
Among the 225 families recognized in Northeast Asia, 24 large families have particularly high species and infraspecific taxa richness, representing 68.55% of the total species. These families are Asteraceae (1133), Poaceae (706), Cyperaceae (643), Fabaceae (585), Rosaceae (439), Ranunculaceae (390), Lamiaceae (310), Aspleniaceae (305), Polypodiaceae (292), Orchidaceae (291), Brassicaceae (241), Caryophyllaceae (215), Apiaceae (209), Ericaceae (187), Polygonaceae (166), Amaranthaceae (145), Orobanchaceae (142), Salicaceae (131), Plantaginaceae (123), Boraginaceae (115), Rubiaceae (115), Violaceae (114), Saxifragaceae (112), Caprifoliaceae (100).
As in Northeast Asia, large families are the most contributing in Mongolia, Northeast China, and Japan, accounting for 52.84%, 48.16%, and 50.45% of the total, respectively (
Figure 2). In Mongolia, 7 large families are Asteraceae (435), Fabaceae (327), Poaceae (224), Brassicaceae (158), Rosaceae (148), Ranunculaceae (129), and Cyperaceae (122). In Northeast China, 8 large families are Asteraceae (456), Poaceae (309), Cyperaceae (255), Fabaceae (215), Ranunculaceae (190), Rosaceae (173), Caryophyllaceae (121), and Lamiaceae (118). Additionally, in Japan 12 large families are Asteraceae (542), Cyperaceae (451), Poaceae (418), Polypodiaceae (281), Aspleniaceae (280), Orchidaceae (260), Rosaceae (221), Fabaceae (192), Ranunculaceae (169), Ericaceae (160), Lamiaceae (152), and Apiaceae (100).
In contrast, in North Korea and South Korea, the medium families contribute the most species and infraspecific taxa, accounting for 42.67% and 37.93% of the total, respectively. The number of large families is relatively small, with only three in North Korea and South Korea, accounting for as low as 27.49% and 24.38% of the total, respectively. They are Cyperaceae (233), Asteraceae (188), and Poaceae (160) in North Korea while Cyperaceae (245), Asteraceae (189), and Poaceae (165) in South Korea.
Dominant family (genus) refers to the family (genus) which contains relatively more species and is typical taxa of particular regions. The main body of the flora of a region usually consists of dominant families (genera), so these families (genera) play important roles in the species origin and floristic research of the region. In this paper, we have defined the top ten largest families as the dominant families in each region, given that they all contribute about half of the species and infraspecific taxa in their respective regions. In terms of the similarity of the dominant families in these five regions, there are six dominant families shared by Japan, North Korea, South Korea, Northeast China, and Mongolia; they are Asteraceae, Cyperaceae, Poaceae, Rosaceae, Fabaceae, Ranunculaceae. Lamiaceae is shared by four other regions except Japan. The common dominant families in the three regions are as follows: North Korea, Northeast China, and Mongolia share Caryophyllaceae; Japan, North Korea, and South Korea share Orchidaceae. Three dominant families are shared by both countries, and Polypodiaceae and Aspleniaceae are shared by Japan and South Korea; Brassicaceae are shared by Northeast China and Mongolia. Ericaceae are the dominant family in Japan but not in other regions, Apiaceae are the dominant family in Northeast China while not in other areas, Amaranthaceae are the dominant family in Mongolia but not in other regions; Polygonaceae are the dominant family in North Korea but not in the other regions. The dominant families in South Korea are also dominant families in other regions, and South Korea does not have any unique dominant families that differ from other areas (
Figure 3).
In this article, “locally endemic” refers to taxa that are unique to a single region within Northeast Asia, although they may also occur outside the area. For the families that compose the flora of Northeast Asia, 94 families are common to the five regions, accounting for 41.04% of the total families. Japan has the largest number of locally endemic families, at 45, accounting for 20.83% of the total number of families in Japan, including 113 species and infraspecific taxa, accounting for 1.77% of the total. Among them, 17 families are single-species families, and the remaining 28 families are small families. There is one locally endemic family in Northeast China, namely Cistaceae (1), accounting for 0.67% of the total families in China. There is one locally endemic family in Mongolia, Biebersteiniaceae (1), accounting for 0.93% of the total families in Mongolia. Neither North Korea nor South Korea has a locally endemic family (
Figure 4).
2.1.3. Analysis of the Components of the Genera
Based on the species (including infraspecific taxa) richness of genera, five genus levels have been classified: ultra-large genera containing more than or equal to 50 species; large genera containing 20 to 49 species; medium genera containing from 10 to 19 species; small genera containing from 2 to 9 species; and single-species genera containing only one species. The 1782 genera in Northeast Asia are classified according to the above levels (
Table 2).
In Northeastern Asia, there are 8 ultra-large genera that each have a minimum of 100 species and infraspecific taxa, which are Carex (420), Artemisia (158), Astragalus (146), Saussurea (128), Salix (117), Oxytropis (117), Cirsium (115), and Viola (114). Japan and Northeast China are characterized by the presence of Carex (275), Cirsium (100), and Carex (173) Artemisia (106), respectively. While North Korea, Mongolia, and South Korea are each host to only one such genus, which are Carex (153), Astragalus (118), and Carex (160), respectively.
The large genera contribute the second most to the flora of Northeast Asia, with 27 genera, accounting for 25.31% of total species, after the small genera, which contain 748 genera, accounting for 27.15% of total species. Single-species genera contribute the least with the highest number of genera, that is 792 genera, accounting for 7.55% of total species. While large genera and medium genera contribute differently, which are 83 genera, accounting for 23.43% of total species, and 132 genera, accounting for 16.55% of total species, respectively.
In contrast, in the five regions of Northeast Asia, small genera contributed the largest number of species to their respective flora. Furthermore, with different genus levels together, the small genera constitute the main composition of their floras. In North Korea and South Korea, it is medium genera that together with the small genera contribute 67.52% and 68.36% of the flora, respectively. In Japan and Northeast China, it is large genera that together with the small genera contribute 55.31% and 60.64%; while in Mongolia, it is the ultra-large genera that together with the small genera contribute 61.58% of the total.
In this paper, we define the top 100 largest genera as the dominant genera in each region, given that the number of species contained in these genera is much higher than the average number of species contained in each genus in their respective regions. Among these dominant genera, thirty-four genera are common to all five regions, and
Carex is the ultra-large genus with a high number of species across all five regions. Other commonly found genera include
Artemisia,
Salix,
Viola,
Saussurea,
Poa,
Potentilla, and
Galium. Some genera, such as
Adenophora,
Iris,
Equisetum,
Festuca,
Lathyrus,
Elymus, and
Ligularia, are small to medium in size in Japan but are dominant in four of the five regions in Northeast Asia. Similarly,
Euphorbia is dominant in four regions except for North Korea (whereas small), as are
Primula (small) and
Stellaria (small) in South Korea (
Figure 5).
The dominant genera in Mongolia differ greatly from those in the other four regions. In the remaining four regions, 18 genera are dominant, while in Mongolia they are either small genera, such as Vincetoxicum, Rhododendron, Dryopteris, Rubus, Cyperus, Asplenium, Persicaria, Angelica, Prunus, Lonicera, Polygonatum, Lilium, Anemone, Betula, and Lespedeza, single-species genera like Euonymus or have no distribution like Quercus and Acer.
Dryopteris, which have a high number of species in North Korea, South Korea, and Japan, are considered medium genera in China and small genera in Mongolia, respectively. Astragalus (118) and Oxytropis (97) are the largest genera in Mongolia and are also considered the large genus and middle genus in Northeast China, with 51 and 36 species and infraspecific taxa, respectively. However, they are considered medium genus and small genus in Japan, with eleven and six species and infraspecific taxa, respectively, and both are small genera in North Korea, with five and two species and infraspecific taxa, respectively. Finally, in South Korea, Astragalus is a small genus with four species and infraspecific taxa, while Oxytropis has no distribution.
The floras of the five regions exhibit a high degree of similarity in terms of the genera that compose them, with 339 genera shared among all the regions. Except for the common genera in these five regions, among the four regions excluding Mongolia, Japan, Northeast China, North Korea, and South Korea exhibit the highest level of similarity, with as many as 231 genera shared. However, the remaining number of genera shared among the 4 regions is significantly lower, with 27, 13, 7, and 3, respectively (
Figure 6).
The local endemism of genera across the five regions is characterized by significant variations. Japan has the highest number of locally endemic genera, with 547, accounting for 37.39% of the total genera in Japan. Mongolia follows, with 16.72% of its total genera being locally endemic which is 112 genera. Northeast China has 54 locally endemic genera, which constitute 6.16% of the total genera. In contrast, South Korea has only three locally endemic genera, namely Abeliophyllum, Mankyua, and Triadica, representing a mere 0.35% of the total genera in the country. North Korea, on the other hand, has no locally endemic genera.
Upon examining the distribution of shared genera in pairs of regions, South Korea and Japan exhibit a noteworthy number of shared genera, with 136 genera accounting for 16.08% and 9.30% of the total genera present in their respective regions. Meanwhile, Northeast China and Mongolia exhibit a substantial presence of shared genera, with 106 genera representing 12.10% and 15.82% of their total genera. There is a modest sharing of genera between Northeast China and Japan, with 24 genera accounting for 2.74% and 1.64% of their total genera. Additionally, Mongolia and Japan share 13 genera, while North Korea and South Korea share 3 genera, including Megaleranthis, Hanabusaya, and Pentactina. The shared genera are limited between North Korea and Northeast China, with only two genera being shared, Carlesia and Physocarpus. Bergenia are shared between Mongolia and North Korea; Platycladus are shared between South Korea and Northeast China; Andromeda and Honckenya are shared between North Korea and Japan. However, no common genera are shared between Mongolia and South Korea.