Boyd Bret M, Seitz Jason C
Center for Biological Data Science, Virginia Commonwealth University, Richmond, VA, 23284, USA.
ANAMAR Environmental Consulting, Inc, 2106 NW 67th Place, Suite 5, Gainesville, FL, 32653, USA.
BMC Ecol Evol. 2021 Oct 21;21(1):192. doi: 10.1186/s12862-021-01922-6.
The evolutionary processes that shape patterns of species richness in marine ecosystems are complex and may differ between organismal groups. There has been considerable interest in understanding the evolutionary processes that led to marine species richness being concentrated in specific geographical locations. In this study we focus on the evolutionary history of a group of small-to-medium sized sharks known as carpet sharks. While a few carpet shark species are widespread, the majority of carpet shark species richness is contained within a biodiversity hotspot at the boundary of the Indian and Pacific oceans. We address the significance of this biodiversity hotspot in carpet shark evolution and speciation by leveraging a rich fossil record and molecular phylogenetics to examine the prehistoric distribution of carpet sharks.
We find that carpet sharks species richness was greatest in shallow seas connected to the Atlantic Ocean during the Late Cretaceous, but that there was a subsequent loss of biodiversity in Atlantic waters. Fossil evidence from sites in close geographic proximity to the current center of carpet shark diversity are generally restricted to younger geologic strata.
From this data we conclude that (1) center of carpet shark biodiversity has shifted during the last 100 million years, (2) carpet sharks have repeatedly dispersed to nascent habitat (including to their current center of diversity), and (3) the current center of carpet shark biodiversity conserves lineages that have been extirpated from this prehistoric range and is a source of new carpet shark species. Our findings provide insights into the roles of marine biodiversity hotspots for higher-tropic level predators and the methods applied here can be used for additional studies of shark evolution.
塑造海洋生态系统物种丰富度模式的进化过程十分复杂，不同生物类群可能存在差异。人们对导致海洋物种丰富度集中在特定地理位置的进化过程颇感兴趣。在本研究中，我们聚焦于一类中小型鲨鱼——毯鲨的进化历史。虽然少数毯鲨物种分布广泛，但大多数毯鲨物种丰富度集中在印度洋和太平洋交界处的一个生物多样性热点地区。我们通过利用丰富的化石记录和分子系统发育学来研究毯鲨的史前分布，探讨这个生物多样性热点在毯鲨进化和物种形成中的重要性。
我们发现，在晚白垩世期间，与大西洋相连的浅海地区毯鲨物种丰富度最高，但随后大西洋水域的生物多样性有所丧失。与当前毯鲨多样性中心地理位置相近的地点的化石证据，通常仅限于较年轻的地质层。
基于这些数据，我们得出以下结论：（1）在过去的1亿年里，毯鲨生物多样性中心发生了转移；（2）毯鲨多次扩散到新生栖息地（包括其当前的多样性中心）；（3）当前毯鲨生物多样性中心保存着已从这个史前分布范围中灭绝的谱系，并且是新毯鲨物种的来源。我们的研究结果为海洋生物多样性热点对高营养级捕食者的作用提供了见解，这里应用的方法可用于鲨鱼进化的其他研究。
