Data from: A biting commentary: integrating tooth characters with molecular data doubles known species diversity in a lineage of sea slugs that consume “killer algae”

Predicting biotic resistance to highly invasive strains of “killer algae” (Caulerpa spp.) requires understanding the diversity and feeding preferences of native consumers, including sea slugs in family Oxynoidae. Past studies reported low algal host specificity for Oxynoe (6 spp.) and Lobiger (4 spp.), but these taxonomically challenging slugs may represent species complexes of unrecognized specialists that prefer different Caulerpa spp. Here, we assess global diversity of these genera by integrating gene sequences with morphological data from microscopic teeth and internal shells, the only hard parts in these soft-bodied invertebrates. Four delimitation methods applied to datasets comprising mtDNA and/or nuclear alleles yielded up to 16 species hypotheses for samples comprising five nominal taxa, including five highly divergent species in Lobiger and five in Oxynoe. Depending on the analysis, a further four to six species were recovered in the O. antillarum-viridis complex, a clade in which mitochondrial divergence was low and nuclear alleles were shared among lineages. Bayesian species delimitation using only morphological data supported most candidate species, however, and integrative analyses combining morphological and genetic data fully supported all complex members. Collectively, our findings double the recognized biodiversity in Oxynoidae, and illustrate the value of including data from traits that mediate fast-evolving ecological interactions during species delimitation. Preference for Caulerpa spp. and radular tooth characteristics covaried among newly delimited species, highlighting an unappreciated degree of host specialization and coevolution in these taxa that may help predict their role in containing outbreaks of invasive algae.预测高入侵性“杀手海藻”（Caulerpa属，Caulerpa spp.）种群的生物抗性，需明确本土消费者的多样性与取食偏好，其中包括鞘海牛科（Oxynoidae）的海蛞蝓。既往研究显示，鞘海牛属（Oxynoe，共6个物种）与叶海牛属（Lobiger，共4个物种）对海藻宿主的特异性较低，但这类分类学上颇具挑战的海蛞蝓类群，实则可能包含未被识别的特化物种复合群，各特化物种偏好不同的Caulerpa属海藻。本研究通过整合基因序列与这类软躯体无脊椎动物仅有的硬结构——显微齿舌及内部贝壳的形态学数据，评估了这两个属的全球物种多样性。我们对包含线粒体DNA（mtDNA）和/或核等位基因的数据集应用4种物种界定方法，在涵盖5个命名分类单元的样本中，最多得到16个物种假说，其中叶海牛属与鞘海牛属各含5个高度分化的物种。针对不同分析方法，在安的列斯鞘海牛-绿色鞘海牛复合群（O. antillarum-viridis complex）这一演化支中，还可检出4至6个物种；该演化支的线粒体分化程度较低，且不同谱系间共享核等位基因。不过，仅基于形态学数据的贝叶斯物种界定方法支持了绝大多数候选物种，而结合形态学与遗传学数据的整合分析则完全支持该复合群的所有成员。综上，本研究的发现使鞘海牛科的已知生物多样性翻倍，同时阐明了在物种界定过程中纳入介导快速演化生态互作的性状数据的重要价值。新界定的物种中，对Caulerpa属海藻的取食偏好与齿舌特征共变异，这凸显了这类类群中未被认知的宿主特化程度与协同演化关系，或有助于预测它们在抑制入侵藻类暴发中所发挥的作用。