本文报道了在美国华盛顿州西部发现的半侧海带附着器化石,表明自最早的渐新世以来,海藻就存在于太平洋东北部。这与提出的北太平洋海藻起源于始新世—渐新世过渡时期的全球变冷说法一致。这些化石也支持在复杂的海藻中,其祖先的状态为发育有半环附着器而不是盘状附着器这一假说,并表明早期的海藻可能有一种灵活的而不僵硬的茎杆。
早期的海藻可能被像desmostylians这样的哺乳动物啃食,但缺乏现存的海藻丛中已知的复杂生态相互作用的化石证据。化石记录进一步表明,如今,多层海藻丛最晚是在中新世中期气候最佳期之后才开始发育。总之,这些化石表明北太平洋海藻生态系统的逐步演化,可能是由海洋气候系统的变化造成的。
据悉,海藻丛是世界范围内,特别是在北太平洋的高产且具有重要经济价值的生态系统。然而,目前关于它们进化起源的假设依赖于稀少的化石记录。
附:英文原文
Title: Early Oligocene kelp holdfasts and stepwise evolution of the kelp ecosystem in the North Pacific
Author: Kiel, Steffen, Goedert, James L., Huynh, Tony L., Krings, Michael, Parkinson, Dula, Romero, Rosemary, Looy, Cindy V.
Issue&Volume: 2024-1-16
Abstract: Kelp forests are highly productive and economically important ecosystems worldwide, especially in the North Pacific Ocean. However, current hypotheses for their evolutionary origins are reliant on a scant fossil record. Here, we report fossil hapteral kelp holdfasts from western Washington State, USA, indicating that kelp has existed in the northeastern Pacific Ocean since the earliest Oligocene. This is consistent with the proposed North Pacific origin of kelp associated with global cooling around the Eocene–Oligocene transition. These fossils also support the hypotheses that a hapteral holdfast, rather than a discoid holdfast, is the ancestral state in complex kelps and suggest that early kelps likely had a flexible rather than a stiff stipe. Early kelps were possibly grazed upon by mammals like desmostylians, but fossil evidence of the complex ecological interactions known from extant kelp forests is lacking. The fossil record further indicates that the present-day, multi-story kelp forest had developed at latest after the mid-Miocene climate optimum. In summary, the fossils signify a stepwise evolution of the kelp ecosystem in the North Pacific, likely enabled by changes in the ocean-climate system.
DOI: 10.1073/pnas.2317054121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2317054121