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Home , Castilleja, Cota (plant), Erica, Flora of Canada, Flora of China, Flora of Taiwan

Núm. 24, pp. 25-51, ISSN 1405-2768; México, 2007

A COMPARATIVE STUDY OF THE OF AND

Zhiyao Su College of Forestry, Agricultural University, Guangzhou 510642 - P. R. China

J. Hugo Cota-Sánchez Department of Biology, University of , Saskatoon, SK S7N 5E2 - Canada E-mail: [email protected]

ABSTRACT at the generic and specific levels that are correlated with more recent geological and In this study, we investigated the floristic climatic variations and ecoenvironment relationships between China and Canada diversity, resulting in differences in floristic based on comparative analysis of their composition. Overall, western and eastern spermatophyte floras. Floristic lists were Canada have a similar number of shared compiled from standard floras and then genera, which suggests multiple migration subjected to cluster analysis using UPGMA events of floristic elements via the Atlantic and NMS ordination methods. Our data and Pacific connections and corridors that demonstrate that the Chinese spermatophyte existed in past geological times. is considerably more diverse than that of Canada and that the taxonomic richness Keywords: China, Canada, floristic rela- of in the floras of China and tionships, taxonomic richness, shared taxa, Canada shows significant variation at the intercontinental disjunction. specific and generic levels. China contains 272 families, 3 318 genera, and 27 078 RESUMEN (after taxonomic standardization), whereas the spermatophyte flora of Canada En este estudio se investigaron la relaciones includes 145 families, 947 genera, and florísticas entre Canadá y China basados 4 616 species. The results indicate that out en análisis comparativos de las floras de of 553 genera shared by the Chinese and espermatofitas de ambos países. Los listados Canadian floras, 60 of them have an eastern florísticos se compilaron de una extensa Asia-North American disjunct distributional revisión de literatura con respecto a inventa- pattern. These disjunct genera show a simi- rios florísticos, floras y trabajos relacionados lar geographic distribution in both eastern a la fitogeografía y vegetación de China y and . There is a higher de- Canadá. Esto incluyó también varios sitios gree of similarity at higher taxonomic levels de Internet que contienen información re- between the two intercontinental floras, ferente a este tema. La riqueza florística en which suggests ancient floristic relations- las diferentes regiones políticas de China y hips, but there are significant differences 25 Núm. 24: 25-51 Noviembre 2007

Canadá se obtuvo a partir de una serie de contribuido a las diferencias florísticas entre hipótesis nulas usando G-test, con las cuales China y Canadá. Éstos son: clima, migra- se evaluaron las diferencias taxonómicas a ción de especies de regiones circunvecinas, niveles ordinales, genéricos y específicos. stasis, y efectos de refugio. Las listas florísticas se organizaron en taxa compartidos en las diferentes categorías A pesar de que la diferencia en extensión taxonómicas entre ambos países y se tabu- territorial entre China y Canadá no es ex- laron en una matriz de datos binaria. tremadamente marcada, la diversidad en relieve topográfico y tipos climáticos de Posteriormente, después de estandarizar los China han favorecido la existencia de una aspectos nomenclaturales, los datos se so- gran variedad de regiones ecogeográficas metieron a análisis de UPGMA (Unweighted y ambientales en ese país. Estas variables Pair-Group Method with Arithmetic Mean) han contribuido a la formación de patrones y NMS (non-metric multidimensional sca- de vegetación geográficos de distribución ling) para estimar y comparar los índices de y composición taxonómicas más comple- similitud florística entre estos países. jas. En general, la diversidad taxonómica, composición florística y regiones fitogeo- Nuestros resultados indican que la flora gráficas de Canadá son mucho más simples espermatofita de China es mucho más di- que aquellas existentes en ese país oriental. versa que la flora canadiense. Además, la De hecho, China es el único país del mundo riqueza taxonómica de estas floras exhibe donde aún existe una conexión continua diferencias significativas a niveles espe- entre los bosques tropicales, subtropicales, cíficos y genéricos. La flora de China es templados y boreales. De la misma mane- aproximadamente seis veces más rica que su ra, las floras adyacentes del centro, norte contraparte canadiense. China incluye 272 y sur de Asia tienen gran influencia en la familias, 3 318 géneros, y 27 078 especies, composición florística de China dado que mientras que la flora de Canadá abarca 145 eventos migratorios pasados y presentes familias, 947 géneros y 4 616 especies. Estas han permitido el intercambio de elementos estadísticas representan una contribución a florísticos, divergencia de especies y casos nivel mundial estimada en 12% para China y de especiación. A su vez, stasis ha tenido un 1.4-1.5% de Canadá. Asimismo, el número papel importante en los complejos procesos de géneros distribuidos en ambos países es de especiación y diversidad de especies, de 533. Este número representa un valor es decir, que los niveles taxonómicos más estimado de 5.4 veces más elevado en la altos representan los linajes filogenéticos cantidad de especies en la flora de China más ancestrales. Finalmente, la noción de (12 967) comparada con 2 384 en Canadá. áreas de refugio también han contribuido En general, existen 123 taxa que exhiben en los niveles de diversidad y diferencias distribución disjunta entre China y Canadá. taxonómicas así como la existencia de Las provincias de la región este de Canadá especies actuales poco comunes pero con comparten un número de especies más alta distribución disjunta. Esto a su vez sugiere con China, y por lo tanto tienen mayor grado que la ruta migratoria florística de elementos de afinidad florística, comparadas con las a través del Estrecho de Bering contribuyó provincias del lado oeste del país. Conside- significativamente a la distribución de espe- ramos que cuatro factores principales han cies en ambos países. En conclusión, nuestro 26 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada estudio confirma que un buen número de 1972; Wood, 1972), ecological (Ricklefs and especies comunes entre China y Canadá Latham, 1992;), geological (Wu, 1983), and tienen distribución vicariante o disjunta phylogenetic (Wen and Stuessy, 1993; Xiang y comparten historia biogeográfica como et al., 1998) perspectives. The temperate resultado de eventos geológicos pasados, y floristic elements exhibiting intercontinental que las floras de estos países han evolucio- disjunct distribution are considered Tertiary nado independientemente a consecuencia de relicts that were once widely distributed aislamiento geográfico y factores climáticos across Laurasia (Li, 1952; Wolfe and y geológicos, entre otros. Leopold, 1967; Xiang et al., 1998). Other references (Kruckeberg, 1983; Wu, 1983, Palabras claves: China, Canadá, relaciones 1991; Ricklefs and Latham, 1992; Wen, florísticas, riqueza taxonómica, taxa 1999) have focused on compiling taxonomic compartidos, disjunción intercontinental. lists of species with disjunct distribution in eastern Asia and North America, particularly INTRODUCTION China and the United States.

The study of the floristic relationships In order to address the floristic relationship between eastern Asia and North America of eastern Asia and North America, previous is an example of long-standing research studies (Cheng, 1983; Hou, 1983; Hsu, focusing on biogeograpical floristic affinities 1983; Wu, 1983; Ying, 1983; Xiang et and intercontinental disjunctions. According al., 1998; Qian, 1999) have compared to Wood (1972), the eastern Asia North the with that of the United American floristic relationships were first States as representative elements of eastern mentioned by Linnaeus in 1750 and later Asia and North America, respectively. in a series of publications between 1840 The geographical and environmental and 1878 by Asa Gray, who brought this similarities and the remarkable interest topic to the attention of other American in disjunctions between China and and European scientists. More recently, a the United States have justified such number of sources (Li, 1952; Boufford and comparisons (Qian, 1999). In spite of Spongberg, 1983; White, 1983; Wu, 1983; the progress made in understanding the Tiffney, 1985; Guo et al., 1998; Xiang et intercontinental disjunctions between al., 1998; Qian, 1999, 2001) have provided eastern Asia and North America, additional evidence that the two floras have similarities floristic and monographic work is needed to in taxonomic diversity and geographic complete a catalogue of species. The Flora distribution patterns. of China project is an ongoing collaborative study with completion estimated in 2010 The occurrence of intercontinental (reviewed in Heywood, 2001; see also Flora disjunction in plants stands as one of the of China Website available at: http://flora. most intriguing circumstances regarding the huh. harvard.edu/china/). floristic relationships between eastern Asia and North America. In fact, the distributional The flora of Canada, on the other hand, has pattern and affinities of the North American received relatively little attention despite and eastern Asia floristic elements has been the historical floristic migrations and extant explained from biogeographical (Raven, examples of disjunt species mediated 27 Núm. 24: 25-51 Noviembre 2007 by past hypothetical land bridges between tasheet, and 3) the shared genera datasheet. northern North America and Eurasia across In addition to data matrices produced from the Atlantic and the Pacific Oceans. In these datasheets, we used Microsoft Access general, the Canadian flora is diverse due utilities to generate a series of queries, to topographic variation and a wide range such as sorting and filtering. Data sources of ecoregions with particular climatic and for tabulation were mainly from published environmental conditions. Canada’s plant literature, including national and provincial biodiversity is primarily found in the wet floras, as well as floristic checklists and west coast temperate forests, the warmer monographs. The main sources for the flora temperate broad- forests in southern in China included the Institute of of , the central deserts and grasslands, the Chinese Academy of Sciences (1987), the tundra plains, and the northern arctic the Flora of China (FOC) project (Wu and plains (Scoggan, 1978). Raven, 1994) web site, Flora of Editorial Board (1979), Hou (1986), and Wu In order to investigate plant disjunct patterns, (1991). Once the taxonomic tabulation was we have undertaken this study to address completed, the scientific name distribution issues concerning the taxonomic richness, of some dubious Chinese genera was veri- distribution, and floristic relationships fied using the FOC. between the extant spermatophyte floras of China and Canada. The objectives of this Checklists and web sites available at http:// research include 1) to compare the floristic mobot.mobot.org/W3T/Search/FOC/projs- richness of the Chinese and Canadian floras foc.html. The primary data sources for the and to determine the dominant plant groups Canadian flora included Scoggan (1957, or families in these areas, 2) to establish 1978), Baldwin (1958), Erskine (1960), a correlation of the affinity of Canadian Roland and Smith (1969), Porsild and Cody and Chinese plants distributed in similar (1980), Moss (1983), Looman and Best phytogeographical areas, and 3) to provide (1987), Douglas et al. (1989-1991), Cody a taxonomic list of elements shared between (1996), and Hinds (1999). the two floras. For standardization purposes the MATERIAL AND METHODS used in this study follows that of Mabberley (1998) at the generic level and Kubitzki’s Our study is primarily based on a com- proposed modifications to Cronquist’s pilation of published data. We conducted 1981 system (listed in Mabberley 1998, extensive literature research to compile pp. 771-781) for higher taxa. Other biblio- information and provide data regarding graphic sources, such as Hou (1986) and species composition, taxonomic richness, Kartesz (1994), were consulted to confirm distribution, and affinities between the questionable taxa. Our floristic databases Chinese and Canadian spermatophyte floras. also include the names as proposed Our searches included library and on-line by the Angiosperm Phylogeny Group (APG, references. The floristic data were tabulated 1998; also see Judd, et al., 2002), reflecting in three Microsoft Access datasheets: 1) the the most recent phylogenetic scheme. China taxa datasheet, 2) the Canada taxa da-

28 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada Abbreviations are as Tianjin; HeN = Henan; SX Shanxi; JX Tianjin; = Xizang; QH Qinghai; NX Ningxia; XJ Xinjiang. GD = Guangdong; GX = Guangxi; HN = ; TW = Taiwan; FJ = Fujian; JS Jiangsu + Shanghai; ZJ Zhejiang; SD Taiwan; = TW GD = Guangdong; GX Guangxi; HN Hainan; China and Canada maps showing the political regions (mainly provinces) considered in this floristic analysis. China: Fig. 1. Shandong; SC = Sichuan + Chongqing; HuB Hubei; HuN Hunan; HeB Hebei Beijing follow: Jiangxi; SSX = Shaanxi; AH = Anhui; LN = Liaoning; JL = Jilin; HLJ = Heilongjiang; NMG = Neimenggu; GZ = Guizhou; YN = ; XZ Yunnan; YN = = Jilin; HLJ Heilongjiang; NMG Neimenggu; GZ Guizhou; Anhui; LN = Liaoning; JL AH = Jiangxi; SSX = Shaanxi;

29 Núm. 24: 25-51 Noviembre 2007 PEI = . BC = ; YT = Territory; NWT = + ; AB = ; AB = + Nunavut; Territories = Northwest NWT Territory; Yukon = YT BC = British Columbia; SK = Saskatchewan; MB ; ON Ontario; QUE ; NB ; NS ; NF Newfoundland; Continuación Fig. 1. Canada:

30 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada

However, the corresponding ordinal cate- (NMS) (Legendre and Legendre, 1998). As gories of the latter treatment were not used an ordination method, NMS provides supe- in our analysis because of the ambiguous rior results compared to analytical methods and/or unassigned position of some species used in ecological and biogeographical in different plant families, which would studies (Rohlf, 1972; Clarke, 1993). Addi- have made the overall floristic comparison tionally, the Bray-Curtis distance measure more difficult. (McCune and Mefford, 1999) was applied to both the cluster analysis and NMS, which The floristic richness and generic distribu- were performed using the multivariate sta- tion in the political regions or provinces tistical package PC-ORD 4.20 (McCune and between China and Canada were generated Mefford, 1999). The G-test analyses were based on the construction of a series of conducted using PopTools (Hood, 2002). null hypotheses. Foremost, we used the G- The remaining calculations were performed test (Sokal & Rohlf, 1995) to evaluate the using the Statistica software (Statsoft, Inc., difference between the floras of China and 1997) package. Canada at different taxonomic levels (order, family, , and species) for both the RESULTS Gymnospermae and the Angiospermae. We used the same approach to determine the ge- Taxonomic Richness: China’s Flora ver- neral distribution patterns of cosmopolitan, sus Canada’s Flora tropical, temperate, and eastern Asia-North American disjunct species. Finally, we used The taxonomic richness of seed plants in the

G-statistics to test our null hypothesis: H0 floras of China and Canada exhibits consi- = the general distribution patterns of the derable variation at the generic and specific shared genera between eastern and western levels. According to Polhill (1990) and He- Canada are similar.The shared genera bet- ywood (2001), the Flora of China project, ween the floras of China and Canada were which includes an estimated 29 500 species, tabulated in the form of a binary data matrix formally published 8 256 species from its based on their distribution in the political beginning in the mid-1980s up to 2001 (less regions of both countries (Fig. 1). that 50% of its flora). Meanwhile, the Flora of China web site reports that China is home This data matrix was then subjected to clus- to approximately 31000 species representing ter analyses (Legendre and Legendre, 1998) about 12% of the world’s flora. Of these, ca. using the Unweighted Pair-Group Method 10 000 are endemic, at least 8 000 species with Arithmetic Mean (UPGMA) algorithm are of economical and medicinal uses, and based on the overall similarity among the po- roughly 3 000 are in danger of . litical regions. In order to produce a second Overall, the Flora of China is much larger matrix, the genera shared between China and than the 20 000 native species representing Canada underwent additional grouping into the combined flora of Canada and U.S.A. particular distribution patterns, specifically the areal types of seed plants proposed by There are discrepancies regarding the Wu (1991). We used this second matrix to number of species in Canada. According map the interrelationships in an ordination to Heywood and Davis (1994), Canada’s by non-metric multidi-mensional scaling estimated number of species 31 Núm. 24: 25-51 Noviembre 2007 is 3 270, of which 147 (4.5%) are endemic. between the floras of China and Canada (Fig. The Natural Heritage Information Centre 2). The species richness of seed plants in (NHIC) lists 4 839 plant species (1 431 China is quite remarkable and is approxi- non-vascular and 3 408 vascular). Based on mately six-fold higher (29 500 to 31 000) the most recent estimate of 320 000 plant compared to that of Canada (ca. 4 000). The species worldwide (Prance, 2001), Canada’s divergence is less significant at the generic flora makes up an estimated 1% of the level, with an estimated four-fold difference world’s plant species diversity and roughly (ca. 1 100 genera in Canada and ca. 4 000 24% relative to the continental flora of the in China). U.S.A., which is estimated to be 20 000 species (Heywood and Davis, 1994). From The taxonomic richness of the Chinese flora a taxonomic perspective, our bibliographic relative to the Canadian flora shows some of research indicates that Canada’s flora con- similarities but also some important diffe- tributes about 1.4 to 1.5% to the world flora: rences (Fig. 3) at different taxonomic ranks. 3 990 to 4 153 to 4 839 species in 154 to 179 The G-test values (Table 1) indicate that the families and 842 to 934 genera (Fig. 3). taxonomic distribution in Gymnospermae There is a marked contrast in the total num- ber of taxa (after taxonomic standardization)

Fig. 2. Total number of taxa in the spermatophyte floras of China and Canada. Number of orders includes Angiospermae only.

32 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada

Fig. 3. Number of taxa at the ordinal, familial, generic, and specific levels in Gymnospermae and the subclasses of Angiospermae in the floras of China and Canada. Gymnospermae families are not grouped into orders.

33 Núm. 24: 25-51 Noviembre 2007 , and (b) comparison of relative frequency. Frequencies of major genera in the floras China and Canada (a) comparison frequency Fig. 4.

34 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada of shared genera. (See Fig. 1 for abbreviations and locations political regions.) Dendrogram showing degree of similarity among the political regions China and Canada based on presence/absence Fig. 5.

35 Núm. 24: 25-51 Noviembre 2007 and all the subclasses of Angiospermae southern China provinces distinguished by in both floras is similar at the ordinal and numerous tropical floristic elements; Group familial levels, significant at the generic 2 (TW, FJ, JS, ZJ, and SD) includes the level (p = 0.00089), and very significant eastern and southeastern coastal provinces (p = 0) at the specific level (Table 1). The characterized by humid subtropical forest contrast in the total number of species bet- environments; Group 3 (HuB, HuN, JX, ween the two countries also reflects a major and AH) corresponds to approximately the difference in number of genera (Fig. 4). The central to floristic region; Group generic incidence in an artificially divided 4 (SC, GZ, YN, and XZ) characterizes the species class limit is significantly different flora in western and southwestern China; between China and Canada (G­adj = 78.87, Group 5 (HeB, HeN, SX, and SSX) repre- G-critical = 21.03, p = 6.77×10 ÿ12) (Fig. 4a). sents the provinces from central to north However, the relative frequencies of genera China dominated by deciduous broad-leaf of the two floras have similar distributions forest; Group 6 (LN, JL, HLJ, and NMG) is (G-adj = 4.17, G-critical = 21.03, p = 0.98), the northern and northeastern floristic region indicating that their distributions correlate in of China characterized by the dominance proportion to the number of species of the of coniferous forests; Group 7 (GS, QH, two floras (Fig. 4b). NX, and XJ) includes the provinces in nor- thwestern China, the floras of which consist Shared Genera and Geographic Patterns of many arid, ephemeral elements. These groups are in agreement with the ecological We identified a total of 553 shared genera regions (Wu, 1980) and floristic zonation of between the Chinese and Canadian floras. China (Wu and Wu, 1998). Although other These 553 genera include an estimated subgroups can be distinguished in the den- number of species 5.4 times higher in China drogram, they do not correspond to any of (12 967) relative to Canada (2 384). A den- the recognized Chinese ecological regions dogram indicating the floristic relationships between the political regions of China and The large cluster representing the Canadian Canada (Fig. 5) was generated from a matrix elements consists of three groups separated containing binary data (presence/absence) by similar distance coefficients, with the based on the distribution of all shared ge- BC group being the most distant. Group nera between the two countries. All shared 1 includes YT and NWT (including the genera were weighted equally in the cluster semiautonomous territory of Nunavut), analysis. As expected, the floras of China mainly characterized by arctic and subarctic and Canada form two large, distinct clusters elements; Group 2 represents the prairie and (Fig. 5). boreal forest elements and consists of the provinces of AB, MB, and SK; and Group These two major groups reflect the diffe- 3 includes all the eastern Canadian provin- rence in generic composition in the two ces (ON, QUE, PEI, NF, NB, NS), which floras. In the China cluster, seven groups of form the eastern Canadian floristic region. floristically similar regions can be identified, Further, the Canadian provinces of Ontario, each with a different coefficient distance. New Brunswick, and Quebec have a high Group 1 (GD, GX, and HN) represents the proportion of shared genera (Fig. 7).

36 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada

Fig. 6. Two-dimensional ordination plots from non-metric multidimensional scaling, showing relationships of the political regions between the floras of China and Canada as determined by the richness of shared genera grouped by areal-types.

37 Núm. 24: 25-51 Noviembre 2007

Fig. 7. Number of genera with an eastern Asia-North American disjunction pattern in provinces and territories of Canada.

Within Group 3, the ON-QUE subgroup is temperate, and eastern Asia-North Ameri- clearly distinguished as it represents part of can disjunct. Further, we treated the eastern the temperate broad-leaf forests. Asia-North American disjunct pattern as a separate geographical element in parallel Geographic Elements of Shared Genera with cosmopolitan, tropical, and temperate elements because of its relative importance Our data were arranged in generic areal in providing insight regarding the biogeo- types, including number of species/genus graphical link between the two floras. based on the areal types concept (Table 2) of Wu (1991), who grouped the Chinese Based on the areal types obtained from seed plant genera into 15 areal types and 35 shared taxa, we generated a second matrix subtypes. Our data indicate that the shared to map the generic interrelationships among genera of seed plants between China and the political regions in both floras using an Canada can be grouped into 24 areal types ordination analysis employing NMS. In and subtypes following Wu’s (1991) con- this analysis, each of the shared genera had cept. These areal types and subtypes can be different weights relative to the equal weight subdivided into four general geographical used in the areal types, which resulted in elements, namely, cosmopolitan, tropical, different groupings of the political regions

38 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada in relation to their floristic components (Fig. China are confined to the western part of 6) as compared with cluster analysis. All the Canada, e.g., Achlys D.C. and Glehnia F. regions of southern and southeastern China, Schmidt ex Miq. occur only in BC; Oplo- which represent the tropical rain forest and panax (Torrey & A. Gray) Miq. occurs only subtropical evergreen broad-leaved forest in BC, YT, and AB; Boschniakia C. Meyer zones, formed a cluster in the lower part ex Bong. is only found in BC, YT, AB, and of the box plot, whereas the northern, nor- NWT. These four genera have an eastern theastern, and northwestern regions of China Asia-western or northwestern American clustered with Canadian regions in the disjunct distribution pattern (Table 3), which upper part of the plot as a result of temperate can be explained from a historical floristic affinities (Fig. 6). These floristic similarities point of view. Graphical representation of suggest that mainland China and southern NMS ordination (Fig. 6) also shows the Canada share comparable latitudinal ranges close floristic relationship between western and climatic characteristics. These groups, Canada and China. directly related to variations in climate and vegetation types, may provide useful infor- DISCUSSION mation to infer historical links between the two floras in forthcoming studies. Although Canada is slightly larger than China, China’s topographic relief and more Shared Genera with an Eastern Asia- diverse climate favour a greater diversity North American Disjunct Distribution of eco-environments/regions, resulting in complex patterns of vegetation with much Overall, our data indicate that there are 123 greater taxonomic richness at the generic spermatophyte genera with the China-North and specific level of seed plants. There are American disjunct distribution pattern. Sixty four major factors that may account for the of these genera are represented in the flora significant differences at the generic and of Canada (Table 3). A number of the genera specific categories in seed plants between extend their distribution beyond the area of China and Canada. First, climate and the study. For instance, Mutis ex L. resulting eco-environment may play a major extends to Europe and Central America, and role modelling distribution and different (Antoine) Carrière ranges to southern types of vegetation, while similar latitude Vietnam. Although most of the 60 disjunct and climatic zones determine floristic affi- genera occur in the eastern provinces of nities. In general, the taxonomic complexity, Canada, a number of them are also found floristic composition, and phytogeographic in the western provinces. regions of the vegetation of Canada are much simple compared with those of China. The eastern Canadian provinces share a re- In fact, China is the only place on Earth latively higher number of genera with China where there is an unbroken connection bet- than the western provinces (Fig. 7; Tables ween tropical, subtropical, temperate, and 4 and 5). However, there is little difference boreal forests. This vegetational continuum in the generic distribution by geographical has resulted in associations of plants that elements between three western and three are rarely seen in other parts of the world, eastern Canadian provinces (Table 5). Fur- many of which are relicts of a once wides- thermore, some of the genera shared with pread flora. In China, tropical rain forests, 39 Núm. 24: 25-51 Noviembre 2007 subtropical evergreen broad-leaf forests, count for differences in species diversity. It temperate deciduous broad-leaf forests, and has been reported that numerous taxa that boreal forest, harbour the country’s mega- occurred in both eastern Asia and North diversity of species from south to north. America in past geological times became Further, from east (at about 30°N) to west extinct from the modern flora of North Ame- and northwest, vegetation types change from rica due to Quaternary glacial events (Wolfe broad-leaf forests, grassland, and steppe to and Leopold, 1967; Xiang et al., 1998). For desert. Conversely, the vegetation of Canada example, fossil records of is characterized by high arctic tundra and L. have been found in Canada (Scoggan, polar desert, low arctic tundra, boreal forest 1978). In contrast, during the Quaternarty or taiga from coast to coast, pacific coast China was relatively warm and served as forest, and western mountain conifer refugia for numerous temperate species, as forest (Barbour and Christensen, 1993). evidenced by the many taxa presumed ex- tinct that were later found in China, notable Second, the adjacent floras of central, nor- examples being L. and thern, and southern Asia largely influence Miki ex Hu & W. C. (Chinese redwood), two the Chinese flora. In all likelihood past and famous genera of ‘‘living fossils’’ found in current plant migration events have allowed the modern flora of China. the interchange of floristic elements and promoted species divergence and specia- When it comes to the historical floristic links tion. We believe that the different migration between eastern Asia and North America, rates and dispersal capacity of species have our study shows that both western and eas- a landscape effect and reflect variation in tern Canada is floristically closely related taxonomic patterns and colonization rates to China. This indicates that the migration in different geographic areas of China and route of floristic elements through the Bering Canada. Strait had a major influence in facilitating species distribution. In addition, there is Statis, the third factor, may also play a role in well-supported evidence that floristic ele- complex patterns of diversity and speciation. ments of eastern Asia migrated to North Ricklefs and Latham (1992) suggested that America through Europe in past geological time is stasis in ecological traits of relict times, resulting in eastern North America genera of temperate perennial herbs. In being more similar to eastern Asia in geo- our view, taxonomic levels represent the graphical elements (Raven, 1972; Tiffney, phylogeny of seed plants, i.e., higher levels 1985; Wen, 1999). On the other hand, the represent older phylogenetic lineages. Ac- migration route through the Bering Strait cordingly, the similarity in higher-level taxa has been a matter of discussion because versus the great difference at the generic and the history of Beringia needs further con- specific levels suggests stasis in the seed sideration in light of plate tectonics (see plants of the Canadian flora. Nonetheless, Raven, 1972). However, other studies have the extreme divergences are consistent with suggested the existence of the Bering Land morphological stasis at lower hierarchical Bridge (e.g., Cox, 1974; Kruckeberg, 1983; ranks, i.e., the specific level. McKenna, 1983; Lindstrom, 2001), thus Lastly, availability of refugia may also ac-

40 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada supporting paleodistribution patterns of Acknowledgements plants and animals. The authors thank Theodore Cochrane for In view of the close similarity between reviewing this manuscript and providing western Canada and China, it is unlikely valuable comments. The China Scholarship that the western floristic elements originated Council provided a fellowship to Z. Su to from Europe via the Atlantic connections but conduct floristic research at the University rather from Beringia. In fact, it has been pro- of Saskatchewan, which in turn funded field- posed that the floristic disjunction involving work of JHCS in China. The assistance of eastern Asia and eastern and western North the staff of the Herbarium of the University America probably arose at different geolo- of Saskatchewan (SASK) is also greatly gical times in different genera (Li, 1952), an appreciated. idea supported by Xiang et al. (1998), who proposed that some of the most remarkable Literature Cited examples of intercontinental disjunction are those between eastern Asia and eastern and APG (Angiosperm Phylogeny Group), western North America. 1998. “An ordinal classification for the families of flowering plants”. Annals In summary, this study confirms that while a of the Missouri , 85: number of shared taxa exhibiting intercon- 531-553. tinental disjuntion share biogeographic his- tory, the floras of China and North America Baldwin, W. K. W., 1958. Plants of the have evolved independently due in part to Clay Belt of Northern Ontario and geographical isolation and climatic patter- Quebec. Ottawa: National Museum ns, among other factors. Similarly, Xiang of Canada. et al. (1998) propose that intercontinental disjunct taxa share historical biogeogra- Barbour, M. G., and N. L. Christensen, 1993. phic patterns and their current vicariant “Vegetation”. In: Flora of North Ame- distribution represents a fragmentation of rica Editorial Committee, Eds. Flora of a past more continuous mixed mesophytic North America, 1: 97-131. New York: forest. Overall, the general information on Oxford Univ. Press. the taxonomy and distribution of plants in China and Canada provided here along Boufford, D. E. and S. A. Spongberg, 1983. with palaeobotanical and geological data “Eastern Asian-eastern North Ameri- can assist in the understanding of migratory can phylogeographical relationships: routes and in estimating times of disjunction A history from the time of Linnaeus between eastern Asian and North America to the twentieth century”. Annals of and taxonomic diversification in regards the Missouri Botanical Garden, 70: with geological events. 423-439.

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44 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada

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Recibido: 20 septiembre 2006. Aceptado: 21 junio 2007.

45 Núm. 24: 25-51 Noviembre 2007

Table 1. Results of the G-tests conducted to examine the difference between the floras of China and Canada at the ordinal, familiar, generic, and specific levels of the Gymnospermae and Angiospermae.

Taxonomic df G-adj value G-critical P value level value Order 10 1.30337 18.30703 0.99943 Family 11 16.69475 19.67515 0.11723 Genus 11 31.56298 19.67515 0.00089 Species 11 931.02550 19.67515 0

46 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada 8 4 9 1 3 6 3 4 0 0 1 8 8 8 4 1 3 3 4 6 3 3 1 4 1 2 4 1 a 8 5 1 8 9 1 2 1 2 1 3 1 5 2 9 8 s e 1 1 2 3 1 9 1 3 d i a c 1 1 2 n e a p s C f o r 8 5 8 4 6 2 5 1 8 2 1 9 6 0 6 3 2 6 7 8 9 3 4 3 8 6 7 e 8 1 2 2 3 8 8 0 6 6 2 6 7 2 7 3 5 6 a b 2 3 4 1 8 4 1 8 3 9 n i m 3 1 1 6 7 2 h 1 u C N a r r e e b 4 5 3 n 8 9 0 6 8 8 0 3 1 3 4 6 7 9 1 1 8 1 7 8 1 2 2 1 1 3 5 e m 8 5 7 4 4 2 6 1 3 5 g u f N o ) 1 9 e 9 0 0 0 2 2 2 3 3 8 8 8 8 8 d 1 0 2 1 1 1 1 1 1 1 1 1 - - - - - 1 2 3 4 6 7 8 9 o ------1 1 1 , 1 2 3 4 5 1 2 3 2 3 5 3 4 u C W ( a c i r n e ) n o A 1 i a o m t S i c 9 c t i A n , 9 n r U n c n . a o o 1 e n o n i u i i o i j t N , t o s t t u m i s n c j c u c t i c A s o o n i A n c i n i d l c f t u u W n d i i u a j h j n c a j t c u x t s s c o c s a o j n i i i a u e e i i i t c s t u d r d p o i b i P d j c i g e r a M o s S d a a e e r d i n c n i T c t t ) m i i d a a d s d n u i - r a i 4 m j d r n y d a f n e r A - s s a A e t a n a r a i e i A l 3 c l . A a a A o i a d . a p ) a m a r 1 e l t r E . i c c t S a l 7 e a a e - i s m c A a m C y d p c c i e e p r A o . a i i a A 8 t t m t n - ( e o e o l r ( m H p . a N . t a t a r a p e A e r 2 l t e o a y . . n S C t ( d . e r d a r p s m a m a m t t d n l e p S i l n d o o c W W e y e o e a t t n i a A t a a p t o n t , , t a n t H d m a t p . i . i l a a b a n n n n n o e . m m n s n o r a t r S a a a t i a a a a a a u e N e e a r r t a i i i r e b s e t l t t e e e e e A t W n s s s a e H d d i p d i a r u l a t n n n n n n n l e i e A d d n n r i o s A A A p n o a a t a a a o t o o l l c s t o A m l a a e t i r r r r r d i a i l r l l l r o a a p a t t e a r r r r r p t p e r r l a a a a a p o o t a a - a c c a i e e e e e o i i e e m a i c c c c i o t t t t t c c s m n n i i i i s s r l M s h i i i i i i i s r p p W W u t t m t t t e - a a u u p p p p a d d d d d A c t s r j j s A r r c c A t d d n m n m o o o o r List of the generic areal types and number species shared genera between China Canada. e e e e e . s s l o r r . l u o i . u u . r r r r o a e a e i i C P T O T T T N C A A N E d O M M E T M M M A P W C d T E T Table 2. Table

47 Núm. 24: 25-51 Noviembre 2007 m A m m m m n N A A A o A i m m m m m m m m m m m m m m E t N N N A A A A A A A A A A A A A A N u N - b N N W N W N s N N N N N W N N N E N N i ------r A s s s s s s s s s s s s s s s s s s t s A A A A A A A A A A A A A A A A A A i E D E E E E E E N E E E E E E E E E E E E d 5 l ± 4 r 5 5 0 2 1 8 - 8 5 6 5 2 1 3 3 6 7 2 4 o 1 1 1 2 1 1 0 s 1 e 3 W i c e p s f a o d r a 1 2 1 3 2 1 1 1 1 1 4 2 4 1 8 3 1 3 4 e n b a m C u N a n 2 3 0 i ± - 2 2 5 1 1 1 1 1 1 1 3 3 1 7 1 1 1 5 h 1 C s s o i s m r p x u r a u a i r p a p g t d r c y s u y i a m a c l u a m s r s p i u c t e e a n u i a o s i a n m n s o y o a r s e s s i p l h o n y o u i u h l d o p a d a l u n t i m p p r c o j r l c l a u p g a t n a n a l m t o y g u o a s e m i m e i u z g e i h l a a c r l p s h o h i i y r y s G C T P T P A S B Z A Z C D P T A C C S e e e e e a e a a e a a e a e a e e e e c e e e a e c c e c c a c a a e a i e c a a e e e e a a a e e e e l c i i e s s a e a a a a a a a n n n a o y c s s n n e a e e e e i i d l e e r f y e e a i i o o i a e c c c c c c e i c r r r m m t c c h a a a a l n n a a o l p p i i i i m p s a a c a a g g i l l l l n n r r r r r p u u i i a a o i i i i r i i F C C P P Z A A G G L L L L O T A B B C s e n a e e e o a m a a s d r d d m e e n c i i l e r a i o n n y p e d i i d e e e e t i e e s l l m p p e a a a a o t a a e e e e e e e e o l o s u c a d d d d a a a a a a y d d i i i i n n o o o t i i m m r r r r i d d d d d d m o r c c i i i i i i o n e e e e m g s i i i i i i m m x t t t t e e c i o l l l l l l y G n i l r r s s s s o o a i i i i i i T G A M A A A C C L L L L L L D A A A A Generic list of seed plants with an eastern Asia-North American disjunction pattern recorded in the floras of China and Canada. Asia-North Generic list of seed plants with an eastern America, W N Am = western North America, NE N Am = northeastern North America, NW N Am = northwestern North America. Am = northwestern North N America, NW Am = northeastern North America, NE N Am = western North N W America, Abbreviations for distributions are: E As = eastern Asia, NE As = northeastern Asia, N Am = North America, E N Am = eastern North America, E N Am = North Asia, N As = northeastern Asia, NE As = eastern Abbreviations for distributions are: E Table 3. Table

48 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada m m m A A m m o o m A m m t t C A A m m m m m m m n N A A A o N d A A A A A A A m i m m m m m m N N E E n t N N A A A A A A A a N N N N N N N u W E N E N l - - - - b e a N N N E N s N W s N E E E W s s N E E E i p - - - - - c ------r i A A A A s s s s s s s s s s s s s s s s o t p r s A A A A A A A A A A A A A A A A i E E E E o u r D E E E E E t N E E E N E E E E E N N E E E E d l ± ± 2 r 0 7 0 5 0 0 - 9 3 2 1 6 3 3 2 2 2 3 5 0 o 1 1 9 2 2 2 1 s 1 9 e W i c e p s f a o d r a 3 0 2 4 2 1 1 1 1 1 1 7 1 1 1 1 4 1 1 1 e n 3 1 b a C m u N a n ± 2 5 i - 3 1 2 1 1 1 1 1 2 4 2 1 1 1 2 1 1 0 1 h 1 3 C s m m n s u u u a o u i h r s a r t t i m e k p s i l s s d n a a r a r m h a y e n j i l a a i t a n e a a a l u c l e r a i o l i c r e n m p l c t e s e o a i f s s p l a t s a d t h m a o m n r h i y n u n a i s o s h t y l c o y e e c h s u g o n n m i o s p r f a s t t l r p h s c r i f i r a e e r y a i e a a g o c d h i r e a e G T A B P C M C O V H H C S A J A D L M M ) ) e e e e e e e a a a a a a a e e e e e e e ) e e a e e e e c c c c c a e e c c a a e a a a a a a e e a e a a a a e c i i i e e e e a a d l l c r r r e e a c c a i l l c c m e e e e e a c a a a l c e a a e r h y y a a c c i l l l a a a a e a i i c l e c a d d e a a h h e e u u u l l e e i i a d i i o a e y n p l c c m r r p p c o o h h h t r r l f c n s a c a a e e i i a a o o m a a a n n i p p p i i a a r i b r u b b y l d d g g n o o o c b b m m p r r o r a m m b u r r r i g o o a a e r a a u u e e a r a a h c c c u u u N P P F C L O P R ( R S S S E H J L B ( B ( F F M M M e e a a e e e e e e e e c d d a a a a a a a a e i i i d d d d d d d d l l a e e e e e e e e e i i i i i i i i e e m i i i i i i i i d p a a a a a a a a a l l l l l l l l Continuación. i o i u d d d d d d d d d m m o o o o o o o o i i i i i i i i i n n o a a r r r r r r r r r n n n n n n n n o e r e e e e e e e e e g g g g g g g g l m m x t t t t t t t t t l a a a a a a a a G i a a s s s s s s s s s a T A A A A A A A A A D H H M M M M M M M M Table 3. Table

49 Núm. 24: 25-51 Noviembre 2007 m A S m m o A A t m m m m m n m o N N A A A A A i A m m m m m m m m m m m m m t A A A A A A A A A A A A A N N N N N u W N W - - b E E E N N N N N E N N N N s N E N N s N N i ------r A A s s s s s s s s s s s s s s s s s s s t s A A A A A A A A A A A A A A A A A A A i E E D E E E E E E E E E E E E E N E E E E N E E d 5 l 0 + ± 1 2 r 0 4 0 0 0 5 5 5 - - 2 3 2 3 8 5 3 9 5 6 0 o 1 1 9 1 1 2 1 1 0 1 s 4 3 8 1 e W i c e p s a f o d a 3 5 r 1 1 1 4 1 2 1 1 1 7 1 1 2 1 1 2 1 5 2 n 1 1 e a b C m u N a 0 n + 2 3 5 0 5 i 1 - - 1 2 1 1 6 6 5 3 6 1 2 1 1 1 0 - 4 1 6 h 1 1 3 9 C s u s s r a s m u e i m x a i p a u p m c a e u r a h r z r s i z u i o a o g a c a n o i a r e u i d a h n c b n a n a s h c i r s i o r d n e o t x a a n a p i p i o n u a m e s h h o u i h l r e a k m s t r l o s o t d h o u p p e r n l l d s s i y m l n y r n u a e e s e a y p y l e l s e y r m p m e o a h a e a i t G N S S A O P N H G D L A A P A P B T G O P e e ) a a e e e e e e e e e e e e e e a a a a c a a a a a a e c a a e e e e a e s s s s s r r a a c e e e c c c e n c e e o o o o o e e a a a a a a a a e e f f o a c r n n n n n g i i e e e e r g g g e a a i i i i i b l l a o a y c c c n e c a a a l l e e r l r h r r e a a a a m m m m m a c c e e m v i u t f f f i i i r c a a a r u u u u u i i i l l l n b b u n a d l m r s s a a a g g g g g p u x x x t e y e m m r r r o o o i a e e e e e a a a a a P F N P S A A A C H L L L L L R R S ( S S U U V e e e c a a a i d d d i i i m i i i p l l l e e e e e e e e e e e e e e e e e e Continuación. o u o o o a a a a a a a a a a a a a a a a a a n o n n n d d d d d d d d d d d d d d d d d d o r i i i i i i i i i i i i i i i i i i g g g s s s s s s s s s s s s s s s s s s x a a a G o o o o o o o o o o o o o o o o o o a T M M M R R R R R R R R R R R R R R R R R R Table 3. Table

50 Zhiyao Su and J.H. Cota-Sánchez: A comparative study of the Floras of China and Canada I 1 6 6 9 2 7 2 8 1 0 E 1 3 P 2 1 7 8 8 S 8 3 4 2 8 N 2 3 2 2 0 6 0 B 4 5 8 2 2 e 8 4 5 3 1 N 0 2 7 3 9 2 4 u l 7 0 7 4 0 a 9 3 6 2 3 v 6 0 7 1 3 . . . . . 7 7 0 9 3 F P 0 0 0 0 0 6 1 6 1 6 N 2 3 l 5 0 9 4 8 E a 8 8 8 8 8 6 3 0 3 3 c U 4 4 4 4 4 2 3 i t 1 1 1 1 1 Q i 9 9 9 9 9 r 9 9 9 9 9 c . . . . . - 5 5 5 5 5 G 5 9 0 2 6 N 6 3 2 4 6 O 2 3 e u l 3 0 2 3 3 5 8 0 3 6 a 8 3 5 8 7 5 1 1 8 T v 1 6 8 9 1 2 2 1 2 9 2 6 j W 2 7 9 5 1 d N . . . . . a 2 0 6 0 4 - G 4 1 3 6 4 B 7 3 4 2 7 2 3 M e u l a 2 5 6 5 8 2 2 2 2 2 K v 6 2 8 1 8 S 1 2 f d 1 5 5 1 2 B 7 2 5 2 7 A 2 3 s t n n o i e t c 0 7 4 6 7 m 6 1 0 1 9 T n e 2 2 l u Y j e -tests conducted to examine the generic distribution according geographical s l Distribution of shared genera according to areal types in Canada. i G a D c 6 1 4 4 5 i C n 5 2 3 2 3 a h m B 2 3 t p i A l e a t o r l a N Table 4. Table p r - g a o e c a o i i l p e l s m p a a s t m o G A c o s r o e i n t a h C T T E T m A summary of A t n p i e A l e a t o r m l a N p r e - g a l o e c a o e i i l p e m s p a s elements between three western (BC, YT, AB) and three eastern (ON, QUE, NF) Canadian provinces. YT, elements between three western (BC, t m o G A o r o e Table 5. Table C T T E T

51