Nectar thieves are costlier than robbers to animal-pollinated plants
ID: 613 / 421
Proposed Symposium Title: Nectar thieves are costlier than robbers to animal-pollinated plants
Laura Leal1,2, Matthew Koski2, Rebecca Irwin3 & Judith Bronstein4
Affiliations: 1 Universidade Federal de São Paulo, Diadema, São Paulo, Brazil. Contact: email@example.com 2 Clemson University, Clemson, South Carolina, USA 3 North Carolina State University, Raleigh, North Carolina, USA 4 University of Arizona, Tucson, Arizona, USA
Mutualistic interactions are biological markets where different species exchange commodities to mutual benefit. Because of that, mutualisms are susceptible to exploitation, with individuals taking without reciprocating. While models predict fitness costs inflicted by exploiters, empirical knowledge is limited, highlighting the need for broader quantification. Pollination serves as a case study since animal-pollinated flowers are commonly exploited by larcenists—non-pollinating animals consuming flower rewards without reciprocating. The impact of larcenists on plant reproduction varies widely, indicating differing costs and factors influencing them. In the context of nectar flowers, the behavior of larcenists, classified as robbers or thieves, plays a crucial role. Robbers damage flowers while extracting nectar, potentially affecting flower attractiveness and female reproductive function. Thieves, though not damaging, can disrupt flower visitation patterns. Plant mating systems further mediate these costs, with self-incompatible or strongly selfing plants experiencing greater impacts. The study aims to fill gaps in understanding by employing a meta-analytical approach, focusing on primary nectar robbing and theft and considering different datasets capturing various pollination process steps. We found that both robbers and thieves negatively influence flower visitation patterns, but only thieves impact nectar quality and availability. Surprisingly, robbers have neutral effects on nectar traits and even improve male reproductive success. On the contrary, thieves consistently reduce male and female reproductive performance. Importantly, these effects remain consistent across plant mating systems, challenging previous generalizations. The study provides a comprehensive evaluation of larcenists' costs on animal-pollinated plants, revealing that nectar theft is more detrimental than robbing, regardless of the plant's mating system. This pioneering evidence enhances our understanding of the intricate dynamics of mutualistic interactions in ecological and evolutionary contexts.