Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT 0909, Australia.
Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
Biol Open. 2023 Feb 15;12(2). doi: 10.1242/bio.059641. Epub 2023 Feb 6.
Bacterial assemblages on amphibian skin may play an important role in protecting hosts against infection. In hosts that occur over a range of environments, geographic variation in composition of bacterial assemblages might be due to direct effects of local factors and/or to evolved characteristics of the host. Invasive cane toads (Rhinella marina) are an ideal candidate to evaluate environmental and genetic mechanisms, because toads have evolved major shifts in physiology, morphology, and behavior during their brief history in Australia. We used samples from free-ranging toads to quantify site-level differences in bacterial assemblages and a common-garden experiment to see if those differences disappeared when toads were raised under standardised conditions at one site. The large differences in bacterial communities on toads from different regions were not seen in offspring raised in a common environment. Relaxing bacterial clustering to operational taxonomic units in place of amplicon sequence variants likewise revealed high similarity among bacterial assemblages on toads in the common-garden study, and with free-ranging toads captured nearby. Thus, the marked geographic divergence in bacterial assemblages on wild-caught cane toads across their Australian invasion appears to result primarily from local environmental effects rather than evolved shifts in the host.
两栖动物皮肤上的细菌组合可能在保护宿主免受感染方面发挥重要作用。在宿主分布于多种环境的情况下，细菌组合组成的地理差异可能是由于局部因素的直接影响和/或宿主进化特征所致。入侵的甘蔗蟾蜍（Rhinella marina）是评估环境和遗传机制的理想候选者，因为蟾蜍在澳大利亚的短暂历史中已经进化出了生理学、形态学和行为的重大转变。我们使用来自自由放养蟾蜍的样本来量化细菌组合的现场水平差异，并进行了一项常见的花园实验，以观察当蟾蜍在一个标准地点下饲养时，这些差异是否消失。在常见环境中饲养的后代中，并未看到来自不同地区的蟾蜍的细菌群落存在较大差异。放宽细菌聚类为操作分类单位而不是扩增子序列变体，同样揭示了常见花园研究中蟾蜍的细菌组合以及附近自由放养蟾蜍的细菌组合之间的高度相似性。因此，野生捕获的甘蔗蟾蜍在澳大利亚入侵过程中细菌组合的明显地理分化似乎主要是由局部环境效应引起的，而不是宿主的进化转变。
