Data from: Hierarchical behaviour, habitat use and species size differences shape evolutionary outcomes of hybridization in a coral reef fish.

Hybridization is an important evolutionary process, with ecological and behavioural factors influencing gene exchange between hybrids and parent species. Patterns of hybridization in anemonefishes may result from living in highly specialized habitats and breeding status regulated by size-based hierarchal social groups. Here morphological, ecological and genetic analyses in Kimbe Bay, Papua New Guinea examine the hybrid status of Amphiprion leucokranos, a nominal species and presumed hybrid between Amphiprion sandaracinos and Amphiprion chrysopterus. We test the hypothesis that habitat use and relative size differences of the parent species and hybrids determine patterns of gene exchange. There is strong evidence that A. leucokranos is a hybrid of smaller A. sandaracinos and larger A. chrysopterus, where A. chrysopterus is exclusively the mother to each hybrid, based on mtDNA cytochrome b and multiple nDNA microsatellite loci. Overlap in habitat, depth and host anemone use was found, with hybrids intermediate to parents and co-habitation in over 25% of anemones sampled. Hybrids, intermediate in body size, colour and pattern, were classified 55% of the time as morphologically first generation hybrids relative to parents, whereas 45% of hybrids were more A. sandaracinos-like, suggesting back-crossing. Unidirectional introgression of A. chrysopterus mtDNA into A. sandaracinos via hybrid backcrosses was found, with larger female hybrids and small male A. sandaracinos mating. Potential nDNA introgression was also evident through distinct intermediate hybrid genotypes penetrating both parent species. Findings support the hypothesis that anemonefish hierarchical behaviour, habitat use, and species-specific size differences determine how hybrids form and the evolutionary consequences of hybridization.

杂交是一类重要的演化过程，生态与行为因子可影响杂交个体与亲本物种间的基因交流。海葵鱼的杂交模式或源于其栖息于高度特化的生境，以及其繁殖地位受基于体型的层级社会群体调控。本研究于巴布亚新几内亚金贝湾开展形态学、生态学与遗传学分析，以验证白顶双锯鱼（Amphiprion leucokranos）的杂交身份：该物种曾被定为独立名义物种，被推测为桑氏双锯鱼（Amphiprion sandaracinos）与橙鳍双锯鱼（Amphiprion chrysopterus）的杂交后代。我们提出假说：亲本物种与杂交个体的生境利用偏好及体型相对差异，决定了基因交流的模式，并对此进行检验。基于线粒体DNA细胞色素b（mtDNA cytochrome b）序列与多个核DNA微卫星位点（nDNA microsatellite loci）的分析结果，有充分证据表明：白顶双锯鱼为小型桑氏双锯鱼与大型橙鳍双锯鱼的杂交后代，且所有杂交个体的母本均为橙鳍双锯鱼。研究发现杂交个体与亲本在生境、栖息深度及宿主海葵选择上存在重叠：杂交个体的生境特征介于双亲之间，且在25%以上的采样海葵中存在共栖现象。杂交个体的体型、体色与斑纹均介于双亲之间，其中55%的个体经形态学鉴定为F1代杂交个体，剩余45%的个体更接近桑氏双锯鱼，提示存在回交现象。研究发现通过杂交回交，橙鳍双锯鱼的线粒体DNA可单向渐渗至桑氏双锯鱼种群中，该渐渗事件由体型较大的雌性杂交个体与小型雄性桑氏双锯鱼交配所介导。同时，通过可渗入双亲种群的独特中间型杂交基因型，可观察到核DNA潜在渐渗的证据。本研究结果验证了前述假说：海葵鱼的层级社会行为、生境利用偏好以及物种间特有的体型差异，共同决定了杂交的形成方式及其演化后果。