Predicted fates of ground-nesting bees in soil heated by wildfire: Thermal tolerances of life stages and a survey of nesting depths

Periodic wildfire defines plant community composition and dynamics in many of the world’s semi-arid biomes, whose climates and floras also favor wild bee diversity. Invasive flammable grasses, deforestation, historical fire suppression and human ignition are increasing fire frequency and intensifying its severity, as well as introducing fire to previously fireproof biomes. In many of these habitats, bees are key pollinators. Many, often most of the solitary bee species and individuals in these biomes nest underground (so-called “mining” bees). To evaluate their susceptibility to fire, we tested heat tolerances of bees’ four life stages using an experimental design that mimicked heat conduction dynamics of natural soils. All life stages survived heating of up to 45 °C for 27 min, but none survived heating at 54 °C for 9 min; the pupal stage survived best. At near-lethal temperatures, more prolonged heating caused more mortality. These data were related to published studies of heat penetration depths in soil during fire and an exhaustive compilation of published nesting depths reported for mining bees. We conclude that a small fraction (9%) of the shallowest-nesting mining bee species is likely to die from soil heating by wildfire. Among these, ground-nesting megachilids (Osmia, Megachile) will be most vulnerable, owing to their shallow horizontal nests. Because mining bees prevail in most biomes of the temperate zone, any vegetation rehabilitation efforts should therefore expect that bee communities will largely survive the immediate effects of wildfire, and therefore will need pollen and nectar resources in the year(s) after fire.     

Population decline in the epiphytic orchid Aspasia principissa

The population dynamics of the epiphytic orchid Aspasia principissa, growing in the moist tropical forest of Barro Colorado Island, Panama, were studied from 1997 until 2004. Using growth analysis, projection matrix analysis, elasticity analysis, and different types of simulations, we identified the components of the life cycle with the strongest effect on population growth rate (λ), and related differences in vital rates to environmental variation, mainly in precipitation. Such information, which is almost completely lacking for tropical orchids, is essential for the efficient conservation of these frequently rare and endangered plants. Elasticity analysis indicated that the population growth rate (λ), which averaged 0.92, was primarily affected by survival, and much less affected by growth or by sexual reproduction. Simulations, which included different levels of pollinator limitation, showed that complete pollination would raise λ to such an extent as to allow long-term persistence of the population. Pollinator limitation per se, however, is presumably not responsible for the currently observed population decline. Instead, we discuss a possible link between low λ and (a) a long-term decline in precipitation and (b) recent increases in forest dynamics: variation in annual rainfall significantly affected both recruitment and growth rates of smaller orchid individuals, while the hypothesised increase in the rates of branch and tree falls would increase mortality rates in this epiphyte.     

6个枣品种最佳授粉组合的研究

对壶瓶枣、骏枣、郎枣、板枣、油枣、相枣等 6个山西枣树主栽品种的异花授粉组合试验发现 ,骏枣、壶瓶枣、相枣、油枣异花授粉可以明显地提高坐果率 ,而板枣、郎枣自花授粉坐果率比较高。在新建枣园时 ,骏枣等品种应设置不同品种的授粉树     

Decline of bumble bees (Bombus) in the North American Midwest

Declines in many bumble bee species have been documented in Europe raising several ecological and economic concerns. The nature and extent of bumble bee decline in North America is poorly understood due mainly to a lack of baseline and long-term data. Museum collections provide excellent sources of information on past and current species distributions, which can be used to infer changes in the composition of insect communities. Using the Illinois Natural History Survey’s electronic database of Hymenoptera and a recent biodiversity survey of historically sampled localities, we were able to examine changes in the richness and distribution of the bumble bee fauna of Illinois over the last century. We found that bumble bee species richness declined substantially during the middle of the century (1940-1960). Four species were locally extirpated: Bombus borealis, Bombus ternarius, Bombus terricola and Bombus variabilis. The ranges of Bombus affinis, Bombus fraternus, Bombus pensylvanicus and Bombus vagans have also decreased in Illinois. Our analyses also indicated that current bumble bee diversity is highest in northern Illinois, where conservation efforts would be most productive. Our study demonstrates that half of the bumble bee species found historically in Illinois have been locally extirpated or have suffered declines, supporting observations of broader declines in North America. Major declines in the bumble bee fauna coincided with large-scale agricultural intensification in Illinois between 1940 and 1960. Attempts to conserve bumble bees in Illinois should involve wildlife-friendly approaches to agriculture, such as increasing agricultural land set-asides and hedgerows, and employing integrated pest management.     

Reproductive success and pollinator effectiveness differ in common and rare Persoonia species (Proteaceae)

In plants, understanding the interactions between breeding systems and pollination ecology may enable us to predict the impacts of rarity. We used a comparative approach to test whether rarity is associated with reproductive biology in two closely-related species pairs. This system has been recently altered by changes in fire regimes and the introduction of European honeybees. More than 35% of flowers matured fruits in the common species after natural-pollination compared to <20% of flowers in the rare species. All species were obligate outcrossers in each of the study populations, but only the two rare species were pollen-limited, having significantly lower fruit-set on open-pollinated flowers than those cross-pollinated by hand (mean ± SE; 0.18 ± 0.02 vs. 0.42 ± 0.05; p < 0.001). Native bees (Leioproctus species) and introduced honeybees (Apis mellifera) visited all species. The native bees visited fewer flowers within a plant and moved greater distances between plants while foraging than honeybees, so the native bees are expected to be more effective in promoting outcrossing. While honeybees were the most frequent visitors to flowers of all species, native bees made more visits to common than rare species (0.65 ± 0.20 vs. 0.20 ± 0.09). Our results suggest that the poorer reproductive success in rare Persoonia species is associated with lower pollinator effectiveness, which is exacerbated by frequent fires and introduced honeybees. If this is a causal relationship, this may increase the probability of extinction in populations of these species.     

Nutritional stress due to habitat loss may explain recent honeybee colony collapses

In spite of the tremendous public interest in the recent large honeybee losses attributed to colony collapse disorder, there is still no definitive explanation for the phenomenon. With the hypothesis that nutritional stress due to habitat loss has played an important role in honeybee colony collapse, I analyze the land use data in United States to show that the colony loss suffered by each state is significantly predicted by the extent of its open land relative to its developed land area. I provide further support for this hypothesis by showing that states with the largest areas of open land have a significantly higher honey yield on a per colony basis. I discuss how increasing loss of foraging resources could be synergistically acting with emerging diseases to stress honeybee populations and the importance therefore for preserving natural areas that act as important pollinator habitats.     

Using monitoring data gathered by volunteers to predict the potential distribution of the invasive alien bumblebee Bombus terrestris

We explored the use of ecological niche-modeling from data compiled in a participatory program of thousands of volunteer observers to quantitatively evaluate the spatial risk of invasion by the alien species Bombus terrestris. B. terrestris has been commercially introduced to Japan for the pollination of greenhouse tomato crops since 1991. Recently, naturalized populations of this species have spread rapidly, particularly in Hokkaido, northern Japan. Two niche-based models were constructed from independent data sets (presence-absence and presence-only data sets) and were used to validate one another. Both models performed well and indicated that the data compiled by participatory programs were useful for generating predictive models of the potential distribution of this invasive species. The models also revealed that the potential distribution of B. terrestris is negatively related to the proportion of woodland area, which corresponds to the known biology of this species. In contrast, the effect of the number of colonies introduced for tomato pollination (represented by tomato production) did not significantly affect the distribution of B. terrestris, indicating that its spread is now entering a phase of dispersal from established feral populations and that primary dispersal from commercial colonies in greenhouses is no longer a limiting factor for the distribution of this invasive species.     

滇东南南瓜传粉昆虫密度对生境丧失的差异性响应

响应多样性理论认为不同传粉蜂对环境胁迫的响应尺度和过程在时空上存在差异,然而目前尚不清楚我国重要农林生态系统传粉蜂对环境胁迫的响应规律。试验以云南省文山州广南县南瓜农田生态系统为研究对象,根据农田景观中自然半自然生境数量和面积的变化梯度和离自然半自然生境的距离梯度选择南瓜样地,抽样调查南瓜样地内熊蜂密度和蜜蜂密度。解译卫星影像获取土地类型数据,分析熊蜂密度和蜜蜂密度同自然半自然生境面积百分率和耕地面积百分率的相关系数,在最大相关系数对应的空间尺度下探索蜜蜂密度和熊蜂密度对生境丧失的响应规律。研究发现,熊蜂密度随自然半自然生境面积百分率的增加而显著增加,但蜜蜂密度并不受自然半自然生境面积的影响。同时,熊蜂密度随耕地面积百分率的增加而显著下降,但蜜蜂密度不受耕地面积的影响。此外,熊蜂密度随离自然半自然生境的距离增加而显著下降,但蜜蜂密度不受距离作用的影响。由此可见,云南省文山州南瓜传粉熊蜂和蜜蜂多度对生境丧失表现出多样的响应规律。熊蜂和蜜蜂对生境丧失的差异性响应可能是保障该区域南瓜受粉的重要机制。     

栽培管理方式对黄冠梨生长发育的影响

在对黄冠梨主要植物学特征和生物学特性进行详细观察调查的基础上 ,研究了授粉品种、留果序位、负载量、套袋等因素对黄冠梨生长发育的影响。