Rodríguez-Barreras Ruber, Cuevas Elvira, Cabanillas-Terán Nancy, Branoff Benjamin
Rev Biol Trop. 2016 Jun;64(2):837-48. doi: 10.15517/rbt.v64i2.19366.
The species Echinometra lucunter, Echinometra viridis, Lytechinus variegatus, Tripneustes ventricosus, and Diadema antillarum are the most common sea urchins of littoral habitats in the Caribbean. T. ventricosus and L. variegatus are associated with seagrass beds, while the other three species usually inhabit hardground substrates. Food preferences of these species are well documented and they are commonly accepted as being primarily herbivorous-omnivorous; nevertheless, few of them have previously been characterized isotopically. We used this approach for assessing the isotopic characterization of five echinoids. We established the trophic position of two groups of co-occurring species and quantified the contribution of food resources in the diet of Echinometra lucunter, considered the most common sea urchin in the Caribbean region. The species T. ventricosus and D. antillarum showed the highest values of δ15N. Sea urchins exhibited similar values of δ13C varying from -11.6 ± 0.63 to -10.4 ± 0.99%. The echinoid E. lucunter displayed the lowest values of carbon, from -15.40 ± 0.76%. Significant differences among species were found for δ15N and δ13C. Seaweed communities exhibited no differences among sites for overall δ15N (F= 1.300, df= 3, p= 0.301), but we found spatial differences for δ13C (F= 7.410, df= 3, p= 0.001). The ellipse-based metrics of niche width analysis found that the hardground biotope species (D. antillarum, E. lucunter, and E. viridis) did not overlap each other. Similar results were obtained for the co-occurring species of the seagrass biotope; however, the distance between these species was closer than that of the hardground biotope species. The Bayesian mixing models run for E. lucunter at all four localities found differences in food resources contribution. The algae D. menstrualis, C. crassa and B. triquetrum dominated in CGD; whereas C. nitens, Gracilaria spp., and D. caribaea represented the main contributor algae to the diet of E. lucunter at LQY. In Culebra Island, no dominance of any particular algae was detected in TMD, where six of the eight species exhibited a similar contribution. Similarities in δ15N between D. antillarum and T. ventricosus may hint towards a similar trophic level for these species, although T. ventricosus is widely accepted as an omnivore, while D. antillarum is considered a generalist herbivore. The lack of overlap among species in the two biotopes seems to indicate a resource partitioning strategy to avoid niche competition among co-occurring species.
刺冠海胆、绿海胆、花斑刺参、大肚海胆和白棘三列海胆是加勒比海沿岸栖息地最常见的海胆。大肚海胆和花斑刺参与海草床有关，而其他三种海胆通常栖息在硬底基质上。这些物种的食物偏好已有充分记录，它们通常被认为主要是食草 - 杂食性的；然而，此前很少有物种通过同位素进行特征描述。我们采用这种方法来评估五种海胆的同位素特征。我们确定了两组共存物种的营养级，并量化了食物资源在刺冠海胆（加勒比地区最常见的海胆）饮食中的贡献。大肚海胆和白棘三列海胆的δ15N值最高。海胆的δ13C值相似，范围从 -11.6 ± 0.63% 到 -10.4 ± 0.99%。刺冠海胆的碳值最低，为 -15.40 ± 0.76%。在δ15N和δ13C方面，物种间存在显著差异。海藻群落的总体δ15N在各地点之间没有差异（F = 1.300，自由度 = 3，p = 0.301），但我们发现δ13C存在空间差异（F = 7.410，自由度 = 3，p = 0.001）。基于椭圆的生态位宽度分析指标发现，硬底生物群落物种（白棘三列海胆、刺冠海胆和绿海胆）之间没有重叠。海草生物群落的共存物种也得到了类似的结果；然而，这些物种之间的距离比硬底生物群落物种之间的距离更近。在所有四个地点对刺冠海胆运行的贝叶斯混合模型发现食物资源贡献存在差异。在CGD地区，月形藻、粗枝软骨藻和三棱藻占主导；而在LQY地区，细基江蓠、 Gracilaria属藻类和加勒比江蓠是刺冠海胆饮食的主要藻类贡献者。在库莱布拉岛，在TMD地区未检测到任何特定藻类占主导，八个物种中的六个表现出相似的贡献。白棘三列海胆和大肚海胆在δ15N上的相似性可能暗示这些物种处于相似的营养级，尽管大肚海胆被广泛认为是杂食性动物，而白棘三列海胆被认为是一般的食草动物。两个生物群落中物种之间缺乏重叠似乎表明存在一种资源分配策略，以避免共存物种之间的生态位竞争。
