Data from: Geographic variation of parasitic and predatory traces on mollusks in the northern Adriatic Sea, Italy: implications for the stratigraphic paleobiology of biotic interactions

Parasitic trematode worms leave characteristic pits in their bivalve mollusk hosts and represent an ideal system for analyzing parasite-host interactions through space and time with statistically meaningful sample sizes. Previous work in Late Pleistocene–Holocene sequences from the Po plain revealed significant long-term fluctuations in trematode prevalence values: higher prevalence in retrogradational environments (TST) and negligible prevalence in progradational environments (HST). Here we expand upon this work by investigating traces of parasitism, kleptoparasitism, and predation on mollusk death assemblages from two domains along the northern Adriatic coastline. The domain north of the Po delta (TST-like) and the southern domain (including the Po delta; HST-like) comprise environments comparable to those recovered in late Holocene (<6 Kyr) subsurface progradational deposits. We collected 17,299 specimens representing 111 species from 11 locations on the northern Adriatic coast of Italy. Our results reveal high predation pressure, a high diversity of host taxa, and widespread presence of trematode infestation in starved, oligotrophic, environmentally more stable (i.e., TST-like) settings north of the Po delta. Immediately south of the Po delta, in settings with strong and variable sedimentary input, almost no infestation is recorded. The reappearance of infestation is evident in the southern portion of the study area (i.e., Cattolica-Montemarciano), relatively far from the highly stressed environments south of the Po River. There is no significant difference in trematode prevalence values between fossil and modern samples. The distribution of spionid traces (an indicator of stressed environments) was nearly the opposite of that displayed by trematodes. Drilling frequency is highest in TST-like environments and is not correlated with diversity indices. These results suggest that temporal trends of trematode prevalence (and possibly also other biotic interactions) in sedimentary successions are controlled by environmental changes driven by glacio-eustatic dynamics, and reaffirm the importance of interpreting temporal trends in the context of spatial variation.

寄生吸虫（Parasitic trematode worms）会在其双壳类软体动物宿主壳体上留下特征性凹陷，是开展时空尺度下寄生-宿主相互作用研究的理想模型体系，且可获得具备统计学意义的样本量。此前针对波河平原（Po Plain）晚更新世-全新世沉积序列的研究显示，吸虫感染率存在显著的长期波动：在退积环境（TST）中感染率较高，而在进积环境（HST）中感染率可忽略不计。本研究在此前工作的基础上，对亚得里亚海北部沿岸两个区域的软体动物死亡组合中的寄生、盗寄生及捕食痕迹展开研究。波河三角洲以北区域（类TST环境）与南部区域（包含波河三角洲；类HST环境）的沉积环境，可与全新世晚期（<6 Kyr）地下进积沉积的环境相类比。我们在意大利亚得里亚海北部沿岸的11个采样点共收集到17299件标本，隶属于111个物种。研究结果显示，在波河三角洲以北的寡营养、环境更为稳定（即类TST环境）的生境中，捕食压力较高、宿主类群多样性丰富，且吸虫感染广泛存在。在波河三角洲以南紧邻区域，由于沉积输入强烈且不稳定，几乎未记录到感染现象。在研究区南部（即卡托利卡-蒙特马尔恰诺区域），远离波河以南的高压力生境处，感染现象再次出现。化石样品与现代样品的吸虫感染率并无显著差异。帚毛虫科（Spionidae）痕迹（作为高压力生境的指示标志）的分布格局与吸虫的分布几乎完全相反。捕食钻孔频率在类TST环境中最高，且与多样性指数无相关性。本研究结果表明，沉积序列中吸虫感染率的时间变化趋势（或许还包括其他生物相互作用）受冰盖-全球海平面变动动力学驱动的环境变化所调控，同时再次证实了在空间变异背景下解释时间变化趋势的重要性。