Leal Laura C, Koski Matthew H, Irwin Rebecca E, Bronstein Judith L
Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Paulo, Diadema, São Paulo, Brazil.
Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA.
Ecology. 2025 Mar;106(3):e70036. doi: 10.1002/ecy.70036.
Mutualistic interactions are biological markets in which different species exchange commodities to mutual benefit. Mutualisms are, however, susceptible to exploitation, with some individuals taking without reciprocating. While it is generally assumed that exploiters will inflict fitness costs, evidence for such costs is mixed and difficult to generalize due to their context-dependent nature. Animal-pollinated flowers are commonly exploited by larcenists, non-pollinating animals that consume floral rewards often without transferring pollen. The impacts of larcenists on plant reproduction vary widely, suggesting they inflict differing costs on plants, but which types of floral larceny are most and least costly, and why, has received little attention. We employed a meta-analytical approach to explore the effects of flower larceny on nectar traits, pollinator visitation, and plant reproduction. We focused on the effects of two contrasting forms of larceny: primary nectar robbing-nectar consumption through holes constructed in the corolla rather than entering flowers legitimately-and nectar theft-nectar consumption by entering flowers but with no pollen transfer. We found that both robbing and theft had negative impacts on nectar quantity and quality, but that only theft negatively affected pollinator visitation rates. Similarly, robbers had no impact on either female or male reproductive success, whereas thieves consistently reduced both male and female reproductive success. These effects were not associated with plant mating systems nor with the identities of robbers and effective pollinators, challenging previous generalizations. This study provides a comprehensive evaluation of larcenists' costs to animal-pollinated plants, revealing that nectar theft is more detrimental to plant reproduction than nectar robbing. These results enhance our understanding of the intricate dynamics of mutualism exploitation in ecological and evolutionary contexts.
互利共生的相互作用是一种生物市场，不同物种在其中交换商品以实现互利共赢。然而，互利共生关系容易受到剥削，一些个体只索取而不回报。虽然通常认为剥削者会带来适合度成本，但由于这些成本具有情境依赖性，关于此类成本的证据并不一致，也难以一概而论。动物传粉的花朵常常被盗窃者利用，这些非传粉动物消耗花朵的花蜜，却往往不传播花粉。盗窃者对植物繁殖的影响差异很大，这表明它们给植物带来的成本各不相同，但哪种类型的花朵盗窃成本最高、哪种最低，以及原因是什么，却很少受到关注。我们采用元分析方法来探究花朵盗窃对花蜜特征、传粉者访花以及植物繁殖的影响。我们重点研究了两种截然不同的盗窃形式的影响：主要的花蜜掠夺——通过在花冠上制造孔洞来消耗花蜜，而不是合法地进入花朵——以及花蜜偷窃——通过进入花朵但不传播花粉来消耗花蜜。我们发现，掠夺和偷窃都对花蜜的数量和质量产生了负面影响，但只有偷窃对传粉者访花率产生了负面影响。同样，掠夺者对雌性或雄性繁殖成功率均无影响，而偷窃者则持续降低了雄性和雌性的繁殖成功率。这些影响与植物的交配系统以及掠夺者和有效传粉者的身份均无关，这对之前的普遍观点提出了挑战。这项研究对盗窃者给动物传粉植物带来的成本进行了全面评估，揭示出花蜜偷窃对植物繁殖的危害比花蜜掠夺更大。这些结果加深了我们对生态和进化背景下互利共生剥削复杂动态的理解。
