Interspecific Hybridization in Pilot Whales and Asymmetric Genetic Introgression in Northern Globicephala melas under the Scenario of Global Warming

Pilot whales are two cetacean species (Globicephala melas and G. macrorhynchus) whose distributions are correlated with water temperature and partially overlap in some areas like the North Atlantic Ocean. In the context of global warming, distribution range shifts are expected to occur in species affected by temperature. Consequently, a northward displacement of the tropical pilot whale G. macrorynchus is expected, eventually leading to increased secondary contact areas and opportunities for interspecific hybridization. Here, we describe genetic evidences of recurrent hybridization between pilot whales in northeast Atlantic Ocean. Based on mitochondrial DNA sequences and microsatellite loci, asymmetric introgression of G. macrorhynchus genes into G. melas was observed. For the latter species, a significant correlation was found between historical population growth rate estimates and paleotemperature oscillations. Introgressive hybridization, current temperature increases and lower genetic variation in G. melas suggest that this species could be at risk in its northern range. Under increasing environmental and human-mediated stressors in the North Atlantic Ocean, it seems recommendable to develop a conservation program for G. melas.

领航鲸（Pilot whales）包含两个鲸类物种：长肢领航鲸（*Globicephala melas*）与短肢领航鲸（*G. macrorhynchus*），二者的分布格局与水温密切相关，在北大西洋等部分区域存在分布重叠。在全球变暖的背景下，受温度调控的物种预计将发生分布范围迁移，其中热带型短肢领航鲸大概率向北扩散，最终导致两类物种的二次接触区域扩大，种间杂交的机会随之增多。本研究报道了东北大西洋海域领航鲸间反复发生杂交的遗传证据：基于线粒体DNA（mitochondrial DNA）序列与微卫星位点（microsatellite loci）的分析结果显示，短肢领航鲸的基因向长肢领航鲸发生了不对称渗入。针对长肢领航鲸的分析发现，其历史种群增长率估算值与古温度振荡存在显著相关性。结合基因渗入（introgression）杂交现象、当前全球气温上升趋势以及长肢领航鲸较低的遗传变异水平，该物种在其北部分布范围内或面临生存风险。鉴于北大西洋地区环境压力与人类活动介导的胁迫持续加剧，为长肢领航鲸制定系统性保护计划实属必要。