Factors restraining the population growth of Varroa destructor in Ethiopian honey bees (Apis mellifera simensis)

Worldwide, the ecto-parasitic mite Varroa destructor has been assigned as an important driver of honey bee (Apis mellifera) colony losses. Unlike the subspecies of European origin, the honey bees in some African countries such as Uganda and Ethiopia may not be as threatened or suffer less from mite-infestations. However, only little is known about the factors or traits that enable them to co-exist with the mite without beekeepers’ intervention. Hence, this study was designed to investigate these factors or traits that limit the Varroa mite population in Ethiopian honey bees (Apis mellifera simensis). The study was conducted in the primary honey producing region of Ethiopia, i.e. Tigray. Mite infestation levels were shown to be lower in traditional hives (when compared to framed hives) and when colonies were started up from swarm catching (when compared to colony splitting). However, the influence of the comb cell size on mite infestation was not observed. With respect to the bee biology, the hygienic behavior was shown to be high (pin-test: 92.2% removal in 24 hours) and was negatively correlated with phoretic mite counts (Pearson; r = -0.79; P P Varroa mite reproductive capacity were seriously hampered by an extremely low brood infestation level. From the 133 founder mites found (in 6727 capped brood cells) only 18.80% were capable of producing a reproductive progeny. Failure to produce adult male progeny was unexpectedly high (79.70%). We have suggested a few adaptations to the test protocols allowing to estimate the protective traits of honey bee colonies under very low Varroa pressure. Apart from that, this study demonstrates that the honey bees from Ethiopia are suitable targets to further decipher the genetic predisposition of resistance against V. destructor. It is still unclear to what extent simensis differs from the more common scutellata subspecies.在全球范围内，狄斯瓦螨（Varroa destructor）已被认定为引发西方蜜蜂（Apis mellifera）蜂群损失的关键驱动因素。与欧洲起源的西方蜜蜂亚种不同，乌干达、埃塞俄比亚等部分非洲国家的西方蜜蜂受该螨类侵染的威胁程度更低，或受害程度更轻。然而，目前学界对这类蜜蜂无需养蜂人干预即可与螨类共存的相关机制与特性仍知之甚少。因此，本研究旨在探究限制埃塞俄比亚西方蜜蜂（Apis mellifera simensis）体内狄斯瓦螨种群数量的相关因素与特性。 本研究于埃塞俄比亚主要蜂蜜产区提格雷地区开展。研究结果表明，传统蜂箱中的螨类侵染水平低于活框蜂箱；通过自然分蜂收捕组建的蜂群，其螨害程度也低于人工分蜂组建的蜂群。但未观察到巢房尺寸对螨类侵染水平存在显著影响。 就蜜蜂生物学特性而言，其卫生行为表现优异（针插测试（pin-test）：24小时内巢房清理率达92.2%），且与寄螨（phoretic mite）的成蜂体表附着数量呈显著负相关（Pearson相关分析：r = -0.79；P < 0.001）。此外，狄斯瓦螨的繁殖能力因封盖子侵染水平极低而受到严重抑制：在6727个封盖幼虫房中发现的133只繁殖雌螨（founder mites）中，仅18.80%能够产生可育后代；无法产生雄性成虫后代的比例高达79.70%，这一结果超出预期。 我们提出了若干测试方案优化建议，以便在极低狄斯瓦螨侵染压力下准确评估蜂群的抗螨特性。此外，本研究证实埃塞俄比亚西方蜜蜂是进一步解析其抗狄斯瓦螨遗传倾向的理想研究对象。目前仍不明确埃塞俄比亚蜜蜂亚种（simensis）与更为常见的东非蜜蜂亚种（scutellata）之间的差异程度。