Egan Joshua P, Buser Thaddaeus J, Burns Michael D, Simons Andrew M, Hundt Peter J
Department of Biological Sciences, Western Michigan University, 2375 West Michigan Ave, Kalamazoo, MI 49006, USA.
Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, 2820 SW Campus Way, Corvallis, OR 97331, USA.
Integr Org Biol. 2021 Mar 16;3(1):obab004. doi: 10.1093/iob/obab004. eCollection 2021.
Marine intertidal zones can be harsher and more dynamic than bordering subtidal zones, with extreme and temporally variable turbulence, water velocity, salinity, temperature, and dissolved oxygen levels. Contrasting environmental conditions and ecological opportunities in subtidal versus intertidal habitats may generate differing patterns of morphological diversity. In this study we used phylogenetic comparative methods, measurements of body length, and two-dimensional landmarks to characterize body shape and size diversity in combtooth blennies (Ovalentaria: Blenniidae) and test for differences in morphological diversity between intertidal, subtidal, and supralittoral zones. We found that subtidal combtooth blennies have significantly higher body shape disparity and occupy a region of morphospace three times larger than intertidal lineages. The intertidal morphospace was almost entirely contained within the subtidal morphospace, showing that intertidal combtooth blennies did not evolve unique body shapes. We found no significant differences in body size disparity between tidal zones, no correlations between body shape and tidal zone or body size and tidal zone, and no body shape convergence associated with tidal zone. Our findings suggest that a subset of combtooth blenny body shapes are suitable for life in both subtidal and intertidal habitats. Many species in regions of morphospace unique to subtidal combtooth blennies exhibit distinct microhabitat use, which suggests subtidal environments promoted morphological diversification via evolutionary microhabitat transitions. In contrast, limited intertidal body shape diversity may be due to strong selective pressures that constrained body shape evolution and environmental filtering that prevented colonization of intertidal zones by certain subtidal body shapes.
海洋潮间带可能比相邻的潮下带更加严酷和多变，具有极端且随时间变化的湍流、水流速度、盐度、温度和溶解氧水平。潮下带与潮间带栖息地截然不同的环境条件和生态机遇可能会产生不同的形态多样性模式。在本研究中，我们使用系统发育比较方法、体长测量和二维地标来表征梳齿鳚（Ovalentaria：鳚科）的体型和大小多样性，并测试潮间带、潮下带和潮上带之间形态多样性的差异。我们发现，潮下带梳齿鳚的体型差异显著更高，占据的形态空间区域比潮间带谱系大三倍。潮间带的形态空间几乎完全包含在潮下带的形态空间内，这表明潮间带梳齿鳚没有进化出独特的体型。我们发现不同潮汐带之间的体型差异没有显著差异，体型与潮汐带之间、体型大小与潮汐带之间没有相关性，并且没有与潮汐带相关的体型趋同现象。我们的研究结果表明，梳齿鳚的一部分体型适合在潮下带和潮间带栖息地生存。在潮下带梳齿鳚特有的形态空间区域中的许多物种表现出独特的微生境利用方式，这表明潮下带环境通过进化微生境转变促进了形态多样化。相比之下，潮间带有限的体型多样性可能是由于强烈的选择压力限制了体型进化，以及环境过滤阻止了某些潮下带体型在潮间带的定殖。
