The effect of volatile compounds from the mashed fresh, fallen, and dried leaves of Murraya exotica on the behavior of red imported fire ant (Solenopsis invicta, RIFA) workers was investigated by fumigation toxicity bioassay. The volatile compounds from different mashed leaves (fresh, fallen, and dried leaves) of M. exotica were collected by solid-phase microextraction and identified by gas chromatography–mass spectrometry. β-Caryophyllene, α-cedrene, α-copaene, β-cubebene, and germacrene D were identified as major components of the volatile compounds. In exposure time from 1 d to 9 d, the mortality of RIFA increased from 5.00% to 100.00% (fresh leaves), 11.67% to 93.33% (fallen leaves), and 15.00% to 83.33% (dried leaves) in minor workers, whereas in major workers, the increases were from 13.33% to 93.33% (fresh leaves), 6.67% to 83.33% (fallen leaves), and 10.00% to 60.00% (dried leaves). The volatile compounds reduced the walking and grasping abilities and aggregation rate of RIFA workers. Results indicate that mashed leaves of M. exotica have potential for controlling RIFA.

No abstract

Quantifying the palaeoclimates of Qinghai-Tibetan Plateau is vital for understanding the uplift history of plateau and the evolution of Asian monsoon since Cenozoic. Recently, the Coexistence Approach (CA) has been employed to reconstruct the palaeoelevation and palaeoclimate of the plateau by several studies. However, the application of CA in mountainous areas and the realism of climate reconstructions via this method are seldom discussed, although the complexity of reconstructions is speculated. Here we reevaluated the realism of climate reconstruction using the CA with modern pollen samples from the Qinghai-Tibetan Plateau, and try to explore the possible factors influencing the precipitation and temperature reconstructions by CA. We suggest that the long-distance transport pollen as a result of the Asian summer monsoon potentially significantly affects the reconstructions both for precipitation and temperature. The precipitation complexly interacting with snowmelt and permafrost thaw leads to the discrepancy between the reconstructed precipitation and the real value. The response temperature for blossoming of dwarfed plants on the plateau is mostly likely higher than the air temperature (usually measured at 1.5 m above ground) due to energy flux or morphological adaptation of inflorescences during the growing season, causing the distortion of temperature reconstructions. Precipitation reconstruction is notoriously difficult as the establishers of CA have already suggested, but reconstructing the low temperatures may be even more challenging on Qinghai-Tibetan Plateau. Though all of the explorations in current paper are in a qualitative way, it offers an inspiration of how appropriately interpret the disagreements between CA results and the observations, and of how to obtain a reasonable reconstruction of palaeoclimate of the plateau.

No abstract

Previous studies have discovered arboreal pollen in non-forested areas on the Tibetan Plateau, which are mostly anemophilous type and regarded as a result of the Asian summer monsoon. However, the relationship between the spatial distribution of wind-pollinated pollen and monsoon has seldom been illustrated quantitatively. Here, we used 676 surface samples (647 compiled, 29 new samples) to examine the characteristics of the spatial distribution patterns of 13 anemophilous pollen taxa on the southeastern Tibetan Plateau, by employing the spatial interpolation technique. Then, we quantified the correlation between the distributions of these taxa and monsoon wind via Mantel test. The results show that the anemophilous pollen represents at least half percentage of the total pollen assemblages in most areas of the study region. Anemophilous tree pollen mainly distributes in the south and southeastern part, while anemophilous non-tree pollen does in the opposite and perpendicular direction. The distributional pattern of non-anemophilous pollen reflects that their corresponding plants most likely constitute the understory components of different forests or the minorities of non-forests communities. Mantel tests indicate that the anemophilous tree pollen has a highest correlation with the Asian summer monsoon. Anemophilous pollen, overall pollen assemblages and anemophilous pollen with air sacs have higher correlations with summer monsoon. Contrarily, non-anemophilous pollen has relatively weak correlation. Furthermore, we found that the relationships between various pollen groups or separate taxa and the Asian summer monsoon are dependent on sample types. The lake sediment surface samples had the strongest signal of the Asian summer monsoon among the different sample types. Our findings provide the strong evidence of the Asian summer monsoon influencing the pollen distribution patterns. More importantly, the quantification of this correlation between anemophilous tree pollen and the Asian summer monsoon offers the fundamentally theoretical basis of reconstructing paleo-monsoon by the proxy of windborne pollen taxa.