The specificity of ambrosia beetle-fungus relationships is unknown for the vast majority of ambrosia symbioses, yet has important implications for the success of these beetles and fungi in their surrounding environments. The polyphagous shot hole borer and the Kuroshio shot hole borer (Euwallacea spp.) are invasive ambrosia beetles that exist sympatrically in California, and together with their fungi cause Fusarium Dieback in a variety of hosts. The potential for the two beetle species to exchange symbionts is unknown, but has important ecological consequences. Here we perform symbiont switching experiments, to determine if the polyphagous and Kuroshio shot hole borers can survive and reproduce on each other’s symbiotic fungi in their invasive range in California. Aposymbiotic foundresses were assessed on their ability to reproduce on each of the beetles’ primary (Fusarium spp.) and auxiliary (Graphium spp., Paracremonium pembeum) fungal symbionts, grown on sawdust-based artificial media. Offspring were collected to confirm which fungi were present in the different sexes and life stages. Additionally, the ability of aposymbiotic and non-aposymbiotic foundresses to survive and reproduce on non-ambrosial Fusarium species was tested. We found that reproduction is maximized on the beetles’ primary Fusarium symbionts, regardless of whether a beetle was paired with its own Fusarium symbiont or its congener’s, indicating that there is potential for symbiont switching in natural populations of these beetles. The addition of auxiliary fungi to treatments containing Fusarium spp. had no effect on overall offspring production, and females that were fed solely on auxiliary fungi produced significantly fewer offspring. Females that were fed non-ambrosial Fusarium species produced significantly fewer offspring than when reared on symbiotic Fusarium, and this was especially pronounced in aposymbiotic females. From our experiments, the putative roles of the primary versus auxiliary fungal symbionts, as well as the implications of these roles for beetle reproduction and development in their surrounding environment, are discussed.

中文翻译：

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加利福尼亚州的多食性和黑潮子hole孔虫（鞘翅目：Scolytinae，Euwallacea spp。）的真菌共生体可以在人工培养基上支持两种失窃甲虫系统

绝大部分菌类共生体尚不知道菌类甲虫-真菌关系的特异性，但对这些甲虫和真菌在其周围环境中的成功具有重要意义。多食性shot孔钻和黑潮shot孔钻（Euwallacea属（spp。）是在加利福尼亚州同时存在的入侵性沙棘甲虫，与它们的真菌一起在多种宿主中引起镰刀菌（Fusarium Dieback）。两种甲虫交换共生体的潜力尚不清楚，但具有重要的生态后果。在这里，我们进行共生菌转换实验，以确定多食性和黑潮子shot虫能否在加利福尼亚州的入侵范围内存活并在彼此的共生真菌上繁殖。对Aposymbiotic的建立者进行了评估，以评估它们在甲虫的初级（镰刀菌属）和辅助性（石墨菌属，副creemmonium pembeum）中的繁殖能力）真菌共生体，生长在基于木屑的人工培养基上。收集后代以确定哪些真菌存在于不同性别和生命阶段。另外，测试了非共生和非共生代种在非镰刀镰刀菌种上存活和繁殖的能力。我们发现，无论甲虫是与其自身的镰刀菌共生体还是其同系物种配对，甲虫的初级镰刀菌共生体均能获得最大繁殖，这表明这些甲虫的自然种群中存在共生体转换的潜力。在含有镰刀菌的治疗中添加辅助真菌spp。对整体后代的生产没有影响，仅靠辅助真菌喂养的雌性产生的后代要少得多。与非共生镰刀菌相比，饲喂非镰刀菌镰刀菌的雌性产生的后代要少得多，这在非共生菌的雌性中尤为明显。从我们的实验中，讨论了主要和辅助真菌共生体的假定角色，以及这些角色对甲虫在其周围环境中繁殖和发育的影响。