Department of Marine Science, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
Fenner School of Environment and Society, Australian National University, Acton, ACT, 2601, Australia.
J Phycol. 2020 Feb;56(1):23-36. doi: 10.1111/jpy.12939. Epub 2019 Nov 21.
Long-distance dispersal plays a key role in evolution, facilitating allopatric divergence, range expansions, and species movement in response to environmental change. Even species that seem poorly suited to dispersal can sometimes travel long distances, for example via hitchhiking with other, more intrinsically dispersive species. In marine macroalgae, buoyancy can enable adults-and diverse hitchhikers-to drift long distances, but the evolution and role of this trait are poorly understood. The southern bull-kelp genus Durvillaea includes several non-buoyant and buoyant species, including some that have only recently been recognized. In revising the genus, we not only provide updated identification tools and describe two new species (D. incurvata comb. nov. from Chile and D. fenestrata sp. nov. from the Antipodes Islands), but also carry out biogeographic analyses to determine the evolutionary history of buoyancy in the genus. Although the ancestral state was resolved as non-buoyant, the distribution of species suggests that this trait has been both gained and lost, possibly more than once. We conclude that although buoyancy is a trait that can be useful for dispersal (creating evolutionary pressure for its gain), there is also evolutionary pressure for its loss as it restricts species to narrow environmental ranges (i.e., shallow depths).
长距离扩散在进化中起着关键作用，促进了异域分歧、范围扩张和物种对环境变化的移动。即使是那些似乎不适合扩散的物种，有时也能长途旅行，例如通过与其他更具内在扩散性的物种搭便车。在海洋大型藻类中，浮力可以使成年藻类及其多样化的搭便车者进行长途漂流，但这种特征的进化和作用还知之甚少。南方公牛藻属 Durvillaea 包括几个非浮力和浮力物种，包括一些最近才被发现的物种。在修订该属时，我们不仅提供了更新的鉴定工具，并描述了两个新物种（智利的 D. incurvata comb. nov. 和安蒂波德斯群岛的 D. fenestrata sp. nov.），还进行了生物地理分析，以确定该属浮力的进化历史。尽管祖先状态是非浮力的，但物种的分布表明，这种特征已经被获得和失去，可能不止一次。我们的结论是，尽管浮力是一种有助于扩散的特征（为其获得创造了进化压力），但由于它限制了物种在狭窄的环境范围内（即浅水区）的生存，因此也存在失去浮力的进化压力。
