Population structure and dispersal of the coral excavating sponge Cliona delitrix

Some excavating sponges of the genus Cliona compete with live reef corals, often killing and bioeroding entire colonies. Important aspects affecting distribution of these species, such as dispersal capability and population structure, remain largely unknown. Thus, the aim of this study was to determine levels of genetic connectivity and dispersal of Cliona delitrix across the Greater Caribbean (Caribbean Sea, Bahamas and Florida), to understand current patterns and possible future trends in their distribution and effects on coral reefs. Using ten species-specific microsatellite markers, we found high levels of genetic differentiation between six genetically distinct populations: one in the Atlantic (Florida-Bahamas), one specific to Florida and four in the South Caribbean Sea. In Florida, two independent breeding populations are likely separated by depth. Gene flow and ecological dispersal occur among other populations in the Florida reef tract, and between some Florida locations and the Bahamas. Similarly, gene flow occurs between populations in the South Caribbean Sea, but appears restricted between the Caribbean Sea and the Atlantic (Florida-Bahamas). Dispersal of C. delitrix was farther than expected for a marine sponge and favoured in areas where currents are strong enough to transport sponge eggs or larvae over longer distances. Our results support the influence of ocean current patterns on genetic connectivity, and constitute a baseline to monitor future C. delitrix trends under climate change.

部分隶属于穿贝海绵属（Cliona）的钻孔海绵可与活造礁珊瑚形成竞争关系，通常会致死珊瑚群体并对其实施生物侵蚀。目前，影响该类群分布的关键生态学特征，如扩散能力与种群结构等，仍未得到充分探明。因此，本研究以大加勒比海区（涵盖加勒比海、巴哈马群岛与佛罗里达海域）内的蚀绵穿贝（Cliona delitrix）为研究对象，旨在明确其遗传连通性与扩散水平，以解析该物种当前的分布格局及未来潜在的分布变化趋势，及其对珊瑚礁生态系统的影响。本研究采用10个物种特异性微卫星标记（microsatellite markers），在6个遗传分化显著的种群间检测到较高水平的遗传分化：1个大西洋种群（佛罗里达-巴哈马种群）、1个佛罗里达特有种群，以及4个南加勒比海种群。在佛罗里达海域，存在两个受水深分隔的独立繁殖种群。佛罗里达礁区内的其他种群之间，以及部分佛罗里达采样点位与巴哈马之间，存在基因流与生态扩散事件。同理，南加勒比海的种群间同样存在基因流，但加勒比海与大西洋（佛罗里达-巴哈马）种群间的基因流似乎受到显著限制。研究发现，蚀绵穿贝的扩散距离远超海洋海绵的预期水平，且在洋流足以长距离输送海绵卵或幼虫的区域，其扩散更为活跃。本研究结果证实了洋流模式对遗传连通性的调控作用，并可为未来气候变化背景下蚀绵穿贝种群动态的长期监测提供基准基线。