Plant molecular phylogeography in China and adjacent regions: Tracing the genetic imprints of Quaternary climate and environmental change in the world's most diverse temperate flora.

The diversity of a region reflects both local diversity and the turnover of species (beta diversity) between areas. The angiosperm flora of eastern Asia (EAS) is roughly twice as rich as that of eastern North America (ENA), in spite of similar area and climate. Using province/state-level angiosperm species floras, we calculated beta diversity as the slope of the relationship between the log of species similarity (S) and either geographic distance or difference in climate. Distance-based beta diversity was 2.6 times greater in the north‐south direction in EAS than in ENA and 3.3 times greater in the east‐west direction. When ln S was related to distance and climate difference in multiple regressions, both distance and climate PC1 were significant effects in the north‐south direction, but only geographic distance had a significant, unique influence in the east‐ west direction. The general predominance of distance over environment in beta diversity suggests that history and geography have had a strong influence on the regional diversity of these temperate floras.

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Beta diversity of angiosperms in temperate floras of eastern Asia and eastern North America

China is among the world's richest countries in terms of plant biodiversity. Besides the abundant flora, containing some 33,000 vascular plants (30,000 angiosperms, 250 gymnosperms, and 2600 pteridophytes), there is extraordinary ecosystem diversity, as well as a large pool of both wild and cultivated germplasms. China is also considered one of the main centers of origin and diversification for seed plants on Earth, and is especially profuse in phylogenetically primitive taxa and/or paleoendemics due to the refuge role glaciation played during the Quaternary period. The collision with the Indian subcontinent significantly enriched Chinese flora and led to the formation of many neoendemisms. However, flora distribution remains uneven, and some local floristic hotspots are found across China, such as Yunnan, Sichuan and Taiwan. Unfortunately, this biodiversity faces enormous threats, which have increased substantially over the last 50 years. The combined effects of habitat destruction and/or fragmentation, environmental contamination, over-exploitation of natural resources, and to a lesser extent, introduction of exotic species, have caused irreparable damage to China's plant biodiversity. Burgeoning economic and population growth have also contributed to this deterioration. It is believed that up to 5000 flora species are currently endangered in China, with some taxa having already become extinct. Although in recent years government authorities have made some efforts to preserve biodiversity, much work remains to be done. While China has established an extensive network of nature reserves and protected areas, encompassing more than 16% of the total land area, insufficient budgetary and staffing commitments are common limitations in their management structures. Ex-situ conservation is also deficient, primarily because the botanical gardens are not representative of several local floras, nor are they often of adequate size or representative of endangered species. The lack of effective and efficient environmental legislation and education are also problems that continue to accelerate the loss of plant biodiversity in China.

Plant Biodiversity in China: Richly Varied, Endangered, and in Need of Conservation

What determines large-scale patterns of species richness remains one of the most controversial issues in ecology. Using the distribution maps of 11 405 woody species in China, we compared the effects of habitat heterogeneity, human activities and different aspects of climate, particularly environmental energy, water–energy dynamics and winter frost, and explored how biogeographic affinities (tropical versus temperate) influence richness–climate relationships. We found that the species richness of trees, shrubs, lianas and all woody plants strongly correlated with each other, and more strongly correlated with the species richness of tropical affinity than with that of temperate affinity. The mean temperature of the coldest quarter was the strongest predictor of species richness, and its explanatory power for species richness was significantly higher for tropical affinity than for temperate affinity. These results suggest that the patterns of woody species richness mainly result from the increasing intensity of frost filtering for tropical species from the equator/lowlands towards the poles/highlands, and hence support the freezing-tolerance hypothesis. A model based on these results was developed, which explained 76–85% of species richness variation in China, and reasonably predicted the species richness of woody plants in North America and the Northern Hemisphere.

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Patterns, determinants and models of woody plant diversity in China.

Aim Identify environmental correlates for tropical tree diversity and composition. Location Borneo, Southeast Asia. Methods A GIS-environmental database with 5 arc minute ( c . 10 × 10 km) resolution was combined with tree inventory data. Tree diversity, phylogenetic diversity (PD) and the two main compositional gradients were determined for 46 tree inventories. Akaike’s information criterion and a data jackknifing procedure were used to select 50 explanatory models for diversity and composition gradients. The average of these models was used as our final diversity and compositional model. We applied Moran’s I to detect spatial autocorrelation of residuals. Results Tree diversity, PD and the two main compositional gradients in Borneo were all significantly correlated with the environment. Tree diversity correlated negatively with elevation, soil depth, soil coarseness (texture) and organic carbon content, whereas it correlated positively with soil C:N ratio, soil pH, moisture storage capacity and annual rainfall. Tree PD was correlated positively with elevation and temperature seasonality and was largely determined by gymnosperms. However, angiosperm PD also correlated positive with elevation. Compositional patterns were strongly correlated with elevation but soil texture, cation-exchange-capacity, C:N ratio, C and N content and drainage were also important next to rainfall seasonality and El Nino Southern Oscillation drought impact. Main conclusions Although elevation is the most important correlate for diversity and compositional gradients in Borneo, significant additional variability is explained by soil characteristics (texture, carbon content, pH, depth, drainage and nutrient status) and climate (annual rainfall, rainfall seasonality and droughts). The identified environmental correlates for diversity and composition gradients correspond to those found in other tropical regions of the world. Differences between the regions are mainly formed by differences in the relative importance of the environmental variables in explaining diversity and compositional gradients.

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Environmental correlates for tropical tree diversity and distribution patterns in Borneo

Aim This paper aims at determining how different floristic elements (e.g. cosmopolitan, tropical, and temperate) change with latitude and major climate factors, and how latitude affects the floristic relationships between East Asia and the other parts of the world. Location East Asia from the Arctic to tropical regions, an area crossing over 50� of latitudes and covering the eastern part of China, Korea, Japan and the eastern part of Russia. Methods East Asia is divided into forty-five geographical regions. Based on the similarity of their world-wide distributional patterns, a total of 2808 indigenous genera of seed plants found in East Asia were grouped into fourteen geographical elements, belonging to three major categories (cosmopolitan, tropical and temperate). The 50� -long latitudinal gradient of East Asia was divided into five latitudinal zones, each of c. 10� . Phytogeographical relationships of East Asia to latitude and climatic variables were examined based on the forty-five regional floras. Results Among all geographical and climatic variables considered, latitude showed the strongest relationship to phytogeographical composition. Tropical genera (with pantropical, amphi-Pacific tropical, palaeotropical, tropical Asia‐tropical Australia, tropical Asia‐tropical Africa and tropical Asia geographical elements combined) accounted for c. 80% of the total genera at latitude 20� N and for c. 0% at latitude 55‐60� N. In contrast, temperate genera (including holarctic, eastern Asia‐North America, temperate Eurasia, temperate Asia, Mediterranean, western Asia to central Asia, central Asia and eastern Asia geographical elements) accounted for 15.5% in the southernmost latitude and for 80% at 55‐60� N, from where northward the percentage tended to level off. The proportion of cosmopolitan genera increased gradually with latitude from 5% at the southernmost latitude to 21% at 55‐60� N, where it levelled off northward. In general, the genera present in a more northerly flora are a subset of the genera present in a more southerly flora. Main conclusions The large-scale patterns of phytogeography in East Asia are strongly related to latitude, which covaries with several climatic variables such as temperature. Evolutionary processes such as the adaptation of plants to cold climates and current and past land connections are likely responsible for the observed latitudinal patterns.

Xiaosi Guo

Papers

Large‐scale phytogeographical patterns in East Asia in relation to latitudinal and climatic gradients

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