Data from: Water and fish select for fleshy fruits in tropical wetland forests

Adjacent floodplain and upland tropical forests experience the same temperature and precipitation regimes, but differ substantially in plant species composition and biotic interactions because of extensive flooding. We hypothesize that flooded forests filter fruiting traits linked to seed dispersal by water and fishes, such that selection by water and fish led to (1) trees that synchronize the timing of fruiting with annual floods, and (2) the evolution of fleshy tissues on fruits to improve buoyancy and increase fruit consumption rates by fish. To test this hypothesis, we compared plant communities in seasonally flooded forests and adjacent upland forest in terms of fruiting phenology, the frequency of trees bearing fleshy-fruit, and the role of fleshy tissues in buoyancy and seed viability. Beta-diversity in this system is high, with significant differences in species composition across habitats. As predicted, the production of ripe fleshy fruits was significantly greater in flooded than upland forests during the flood season. Furthermore, we found that trees with fleshy fruit were significantly more abundant in flooded forests even though species richness of fleshy-fruit bearing trees was proportionally similar in flooded and upland forests. Additionally, fleshy pulp increased buoyancy. Likewise, time afloat decreased for denser fruit and those with high seed to pulp ratios. In concert, these results suggest that fleshy fruits in Neotropical floodplain forests facilitated hydrochory and ichthyochory. Once established, water and fish became important agents of selection on fruiting traits.

相邻的泛滥平原热带林与丘陵热带林具有一致的温度与降水格局，但因长期淹水的影响，二者在植物物种组成与生物相互作用方面存在显著差异。本研究提出如下假说：淹水森林会筛选出与水、鱼类介导的种子传播相关的结实性状，即水与鱼类的选择压力会催生两类演化特征：其一，乔木的结实时序与年度淹水周期同步；其二，果实演化出肉质组织，以提升果实浮力并提高鱼类取食果实的频率。为验证该假说，本研究针对季节性淹水森林及其相邻丘陵林的植物群落展开对比分析，从结实物候、结肉质果乔木的占比，以及肉质组织对果实浮力与种子活力的作用三个维度开展研究。该研究体系内的β多样性（beta-diversity）较高，不同生境间的物种组成存在显著差异。正如假说预测，在淹水季，淹水森林中成熟肉质果的产量显著高于丘陵林。此外，本研究发现，即便结肉质果乔木的物种丰富度在淹水林与丘陵林间比例相近，但淹水林中结肉质果乔木的个体丰度显著更高。同时，果肉可显著提升果实浮力。同理，果实密度越高、种子与果肉质量比越大，其漂浮时长越短。综合上述结果可知，新热带区（Neotropical）泛滥平原森林中的肉质果实可促进水媒传播（hydrochory）与鱼媒传播（ichthyochory）。该传播策略确立后，水与鱼类便成为调控结实性状演化的关键选择压力来源。