A framework for comparing pollinator performance: effectiveness and efficiency

Abstract

Measuring pollinator performance has become increasingly important with emerging needs for risk assessment in conservation and sustainable agriculture that require multi-year and multi-site comparisons across studies. However, comparing pollinator performance across studies is difficult because of the diversity of concepts and disparate methods in use. Our review of the literature shows many unresolved ambiguities. Two different assessment concepts predominate: the first estimates stigmatic pollen deposition and the underlying pollinator behaviour parameters, while the second estimates the pollinator's contribution to plant reproductive success, for example in terms of seed set. Both concepts include a number of parameters combined in diverse ways and named under a diversity of synonyms and homonyms. However, these concepts are overlapping because pollen deposition success is the most frequently used proxy for assessing the pollinator's contribution to plant reproductive success. We analyse the diverse concepts and methods in the context of a new proposed conceptual framework with a modular approach based on pollen deposition, visit frequency, and contribution to seed set relative to the plant's maximum female reproductive potential. A system of equations is proposed to optimize the balance between idealised theoretical concepts and practical operational methods. Our framework permits comparisons over a range of floral phenotypes, and spatial and temporal scales, because scaling up is based on the same fundamental unit of analysis, the single visit.

Insights from measuring pollen deposition: quantifying the pre-eminence of bees as flower visitors and effective pollinators

“…Primack and Silander 1975;Thomson 1991, 1996;Adler and Irwin 2006;Ne'eman et al 2010), rather than just recording visitation frequencies. Achieving this improvement can have a substantial impact on our views of the broader issue of generalisation and specialisation in pollination (Ollerton et al 2009;Willmer 2011;Armbruster 2017).…”

The most effective pollinator revisited: pollen dynamics in a spring-flowering herb

“…318) implies that floral characters should evolve to match ''the most frequent and effective'' visitor. When we look at various metrics used to quantify pollinator performance (presented and/or reviewed in, e.g., Kearns and Inouye 1993;Dafni et al 2005;Fenster et al 2004;Ne'eman et al 2010), we may distinguish between a ''quantitative'' and ''qualitative'' component of animal activity, where quality determines animal's ability to deliver pollen grains to conspecific stigmas, and quantity usually refers to the frequency of visits to a particular plant species (Herrera 1987;Olsen 1997). These two components of insect effectiveness (sensu Willmer 2011) are independent because rare visitors may carry more pollen than the common ones or vice versa (e.g.…”

Per-visit pollinator performance and regional importance of wild Bombus and Andrena (Melandrena) compared to the managed honey bee in New York apple orchards

“…Here, we employ an alternative method that experimentally establishes relationships between stigmatic pollen deposition and fruiting response (Cane and Schiffhauer 2003). Ne'eman et al (2010) distinguish a pollinator's ability to transfer pollen from its ability to initiate a fruiting response as per-visit effectiveness and efficiency, respectively. We adopt these terminologies here and, ultimately, rely on per-visit efficiency as our measure of per-visit performance.…”