Phylogeny explains why less therapeutically redundant plant species are not necessarily facing greater use pressure

Understanding which factors influence medicinal plant species selection
and harvest or use pressure can provide valuable insights for sustainable
management of natural resources and conservation efforts. The utilitarian
redundancy model, a theoretical framework in ethnobotany, suggests that
species that are therapeutically redundant or fulfill similar therapeutic
functions within traditional ethnomedicine are less likely to be under
greater use pressure. However, species’ evolutionary relatedness and the
preference of certain species over others to treat a given illness can
directly affect how use pressure is diffused across several groups of
species. These factors may alter the strength of the therapeutic
redundancy-use pressure relationship. Medicinal plant species that fulfill
the same therapeutic functions may experience greater use pressure despite
their level of therapeutic redundancy because they are preferred—where
most people select these species preferably over other species that are
equally available for a given treatment. Further, species that are closely
related evolutionarily may be more likely to be harvested not because they
are therapeutically unique but because they share evolutionary traits such
as secondary chemistry with other medicinally important species which may
make them more prone to being harvested. We investigate the effects of
species therapeutic redundancy, use value, preference, and evolutionary
relatedness on species use pressure in the Shipibo-Konibo community of
Paoyhan in the Peruvian Amazon region. We used phylogenetic generalized
least squares models to identify significant predictors of species use
pressure for 62 medicinal plant species cited by 30 participants and
fulfilling 31 therapeutic functions in Shipibo-Konibo ethnomedicine. Our
model controlling for species’ shared evolutionary history indicated that
therapeutically redundant medicinal plants experienced greater levels of
use pressure. However, as preference increased, the effect of
therapeutic redundancy on species use-pressure became less positive.
Contrary to predictions, species preference by local people alone did not
predict use pressure. Further, when we control for species’ shared
evolutionary history, the effect of preference on species use pressure was
dependent on therapeutic redundancy. Our study illustrates the importance
of controlling for evolutionary relatedness between species in studying
plant-human interactions and the complexity involved in employing the
utilitarian redundancy model to inform management and conservation
efforts.

探明哪些因素会影响药用植物物种的选择、采收或利用压力，可为自然资源可持续管理与保护工作提供重要参考。功利性冗余模型（utilitarian redundancy model）是民族植物学（ethnobotany）中的一种理论框架，该模型提出：在传统民族医药中，具有治疗冗余性或执行相似治疗功能的物种，承受更高利用压力的可能性更低。然而，物种的进化亲缘关系，以及在治疗特定疾病时部分物种相较于其他物种更受青睐的情况，会直接影响利用压力在多个物种类群间的扩散方式。这些因素可能会改变治疗冗余性与利用压力之间关联的强度。即便具备一定的治疗冗余性，执行相同治疗功能的药用植物物种仍可能承受更高的利用压力，原因在于这类物种更受青睐：多数人在针对某一病症进行治疗时，会优先选择这类物种，而非其他可同等获取的替代物种。此外，进化亲缘关系较近的物种更易被采收，这并非因为它们具备独特的治疗价值，而是因为它们与其他具有药用价值的物种共享次生代谢性状等进化特征，这一特性使其更易被采收。我们以秘鲁亚马逊地区帕奥扬（Paoyhan）的希皮博-科尼博（Shipibo-Konibo）族群社区为研究对象，探讨了物种治疗冗余性、利用价值、受青睐程度以及进化亲缘关系对物种利用压力的影响。我们基于30名受访者记录的、在希皮博-科尼博民族医药中承担31种治疗功能的62种药用植物物种，采用系统发育广义最小二乘模型（phylogenetic generalized least squares models）筛选出对物种利用压力具有显著预测作用的因子。在控制物种共享进化历史的模型中，具备治疗冗余性的药用植物承受了更高的利用压力。然而，随着物种受青睐程度的提升，治疗冗余性对物种利用压力的正向影响会逐渐减弱。与预设假设相反，当地民众对物种的单一偏好程度无法预测该物种的利用压力。此外，在控制物种共享进化历史的前提下，物种受青睐程度对利用压力的影响取决于其治疗冗余性。本研究表明，在探讨植物-人类互作关系时，控制物种间进化亲缘关系的重要性，以及运用功利性冗余模型指导管理与保护工作所涉及的复杂性。