Rapid changes in eastern Himalayan alpine flora with climate change.

PREMISE OF THE STUDY: With biodiversity and rates of climate change among the highest, the eastern Himalaya are critical for understanding the interaction of these two variables. However, there is a dearth of longitudinal data sets that address the effects of climate change on the exceptional alpine biodiversity of the Himalaya. METHODS: We established permanent alpine vegetation monitoring plots in three mountain chains of the Hengduan Mountains, the easternmost Himalaya, which have warmed 0.03-0.05°C yr-1 since 1985. Recently, we resampled plots (176 1-m2 quadrat plots and 88 sections of 11 summits in three Hengduan mountain chains) to measure changes in vegetation after 7 years. KEY RESULTS: Over 7 years, Tibetan alpine vegetation increased in number of species (+8 species/summit; +2.3 species/m2 ), in frequency (+47.8 plants/m2 ), and in diversity (+1.6 effective species/m2 ). Stepwise regressions indicated that warmer temperatures, southerly aspects, and higher elevations were associated with greater increases in these vegetation metrics. Unexpectedly, Himalayan endemic species increased (+1.4 species/m2 ; +8.5 plants/m2 ), especially on higher-elevation summits. In contrast, the increase in relative abundance of non-alpine species was greater at lower-elevation summits. Plants used by local Tibetans also increased (+1.3 species/m2 ; +32 plants/m2 ). CONCLUSIONS: As in other alpine areas, biodiversity is increasing with climate change in the Himalaya. Unlike other areas, endemic species are proliferating at the highest summits and are indicators of change.

Fast and Cheap in the Fall: Phylogenetic determinants of late flowering phenologies in Himalayan Rhododendron.

PREMISE OF THE STUDY: Biotic and abiotic pressures affect the beginning and end of phenologies differently, but little is known about how these temporal components may be determined by phylogeny. We tested for phylogenetic signal in the phenological components and related traits among Himalayan Rhododendron species. METHODS: We constructed a phylogeny with trnL-trnL-trnF, atpH-I, RPB2-I (3F-4R), and ITS 4-5, and examined it in combination with trait data recorded for a nine-species assemblage on Mt. Yulong, Yunnan, China. KEY RESULTS: Uniquely among phenological traits, 'last flowering day' had a significant phylogenetic signal. Last flowering day was latest in the clade with the smallest fruits. A similar association between the end of flowering and reproductive investment existed in data from Flora of China (Wu et al., 2005) for 160 Yunnan Rhododendron species, for which last flowering month was correlated with fruit size. CONCLUSIONS: Phylogenetic determinants of last flowering day and fruit size may be driven by limited time for fruit development before the onset of cold temperatures in autumn-a temporal niche that only small-fruited species can occupy. This strategy is analogous to 'fast and cheap' spring ephemerals. More may be gained from late-phenology studies, both within and among species and across seasons.

Herbarium specimens show contrasting phenological responses to Himalayan climate.

Responses by flowering plants to climate change are complex and only beginning to be understood. Through analyses of 10,295 herbarium specimens of Himalayan Rhododendron collected by plant hunters and botanists since 1884, we were able to separate these responses into significant components. We found a lack of directional change in mean flowering time over the past 45 y of rapid warming. However, over the full 125 y of collections, mean flowering time shows a significant response to year-to-year changes in temperature, and this response varies with season of warming. Mean flowering advances with annual warming (2.27 d earlier per 1 °C warming), and also is delayed with fall warming (2.54 d later per 1 °C warming). Annual warming may advance flowering through positive effects on overwintering bud formation, whereas fall warming may delay flowering through an impact on chilling requirements. The lack of a directional response suggests that contrasting phenological responses to temperature changes may obscure temperature sensitivity in plants. By drawing on large collections from multiple herbaria, made over more than a century, we show how these data may inform studies even of remote localities, and we highlight the increasing value of these and other natural history collections in understanding long-term change.

Genetic variation in walnuts (Juglans regia and J. sigillata; Juglandaceae): Species distinctions, human impacts, and the conservation of agrobiodiversity in Yunnan, China.

Walnuts are a major crop of many countries and mostly cultivated in large-scale plantations with few cultivars. Landraces provide important genetic reservoirs; thus, understanding factors influencing the geographic distribution of genetic variation in crop resources is a fundamental goal of agrobiodiversity conservation. Here, we investigated the role of human settlements and kinship on genetic variation and population structure of two walnut species: Juglans regia, an introduced species widely cultivated for its nuts, and J. sigillata, a native species cultivated locally in Yunnan. The objectives of this study were to characterize sympatric populations of J. regia and J. sigillata using 14 molecular markers and evaluate the role of Tibetan villages and kin groups (related households) on genotypic variation and population structure of J. regia and J. sigillata. Our results based on 220 walnut trees from six Tibetan villages show that although J. regia and J. sigillata are morphologically distinct, the two species are indistinguishable based on microsatellite data. Despite the lack of interspecific differences, AMOVAs partitioned among villages (5.41%, P = 0.0068) and kin groups within villages (3.34%, P = 0.0068) showed significant genetic variation. These findings suggest that village environments and familial relationships are factors contributing to the geographic structure of genetic variation in Tibetan walnuts.

Human-induced dwarfing of Himalayan snow lotus, Saussurea laniceps (Asteraceae).

Because evolutionary processes such as genetic drift and natural selection play a crucial role in determining the response that species will have to human-induced disturbances, there is increasing interest in the evolutionary aspects of conservation biology. Harvesting select individuals in natural plant populations can bring about unforeseen impacts that may negatively affect fitness. We analyzed how human harvesting affects two congeners known as snow lotus. Over a period of 100 years, there was a negative trend in plant height (r2= 0.4361, P < 0.001) for the intensely collected and rare species, Saussurea laniceps, but not in the less intensely collected species, Saussurea medusa. Additionally, S. laniceps were significantly smaller in areas of high harvest than in areas with low harvest (Z = 4.91, P < 0.0001), but this was not so for S. medusa. Humans can unconsciously drive evolution and must be considered when managing threatened species.