Osmia emerging time

<em>Osmia cornifrons</em> was imported from Japan in 1976 to Maryland, US, for orchard pollination and since then is expanded to almost all Eastern US. Their impacts on native species are unknown. The invader <em>O. cornifrons</em> and the native <em>Osmia lignaria</em> <em>lignaria</em> have now a very similar distribution, they have a similar biology and nest in the same nest structures. Niche overlap may lead to competition between both species. Here, I analyzed the phenological overlap of <em>O. cornifrons</em> with the native species <em>O. lignaria</em> at Hutchington Memorial Forest, New Jersey, USA. I monitored 125 cocoons of each species that wintered exposed to the same natural conditions. Emergence of both species was monitored along 35 days during spring 2011. As showed in the figure, the invader,<em> O. cornifrons</em>, emerged earlier than the native bee (Cox survival analysis: z = -4.9; p &lt; 0.001). I speculate that this can give to the invader an advantage when choosing nesting sites, but at the same time could increase the risk of the invader to late spring frosts.

角额壁蜂（Osmia cornifrons）于1976年从日本引入美国马里兰州，用于果园授粉，此后其分布范围已扩张至美国东部绝大多数区域。目前该入侵物种对本土物种的影响尚不明确。

如今，入侵种角额壁蜂（Osmia cornifrons）与本土的蓝壁蜂指名亚种（Osmia lignaria lignaria）的分布范围高度重合，二者生物学特性相似且营巢结构一致，生态位重叠可能引发两物种间的竞争。

本研究针对美国新泽西州哈钦顿纪念森林（Hutchington Memorial Forest）内的角额壁蜂与该本土壁蜂的物候重叠情况展开分析：研究人员对各125枚在相同自然环境条件下越冬的两种壁蜂的茧进行了监测，于2011年春季连续35天跟踪记录二者的羽化动态。结果如图所示，入侵种角额壁蜂的羽化时间早于本土壁蜂（Cox生存分析：z = -4.9；p < 0.001）。本研究推测，该特性可使入侵种在选择营巢位点时获得竞争优势，但同时也会增加其遭遇晚春霜冻的风险。