Uncovering the significance of the ratio of food K:Na in bee ecology and evolution

Abstract

Bees provide important ecological services, and many species are threatened globally, yet our knowledge of wild bee ecology and evolution is limited. While evolving from carnivorous ancestors, bees had to develop strategies for coping with limitations imposed on them by a plant‐based diet, with nectar providing energy and essential amino acids and pollen as an extraordinary, protein‐ and lipid‐rich food nutritionally similar to animal tissues. Both nectar and pollen display one characteristic common to plants, a high ratio of potassium to sodium (K:Na), potentially leading to bee underdevelopment, health problems, and death. We discuss why and how the ratio of K:Na contributes to bee ecology and evolution and how considering this factor in future studies will provide new knowledge, more accurately depicting the relationship of bees with their environments. Such knowledge is essential for understanding how plants and bees function and interact and is needed to effectively protect wild bees.

Wild Bee is an Important Contributor to the Nutrient Cycle, as Shown by Biogeochemical Niche Analysis of Osmia Bicornis

“…However, the contribution of Ranunculus to dietary Na may be interpreted considering plant-pollinator interaction. Plants in the genus Ranunculus are insectpollinated, and perhaps the high Na content of their pollen is the result of a strategy to increase the likelihood of pollination, as suggested by (Finkelstein et al 2022) and described by Filipiak et al (2023). This hypothesis requires further research.…”

“…Oak and maple additionally contributed the most to the dietary proportions of two essential trace elements, i.e., Cu, and Zn. Wind-pollinated grasses contributed highly to the Na proportion, which is crucial for bees because of the generally high K:Na in plant tissues, which is harmful for herbivores (Filipiak et al 2023;Kaspari 2020).…”

“…Another particularly interesting element is Na, since herbivores cope with a generally high K:Na ratio in their food, potentially causing health problems, underdevelopment and reduced fitness (Filipiak et al 2023;Kaspari 2020Kaspari , 2021. Given current knowledge, it is not clear why grasses contribute to the Na concentration in the bee's diet: grasses are anemophilous, it is therefore not expected that grasses interact with pollinators regulating the nutritional composition of pollen.…”

Sodium‐enriched nectar shapes plant–pollinator interactions in a subalpine meadow

“…Thus, our observation that nearly all pollinator species in the experiment appear to prefer flowers with sodium‐enriched nectar is consistent with the “salty nectar hypothesis” (Figure 1b ; Kaspari, 2020 ). Pollinators depend heavily on nectar (and pollen) for their nutrient demands, and most pollinators lack strategies to supplement sodium ( but see : Bänziger et al., 2009 , Dorian & Bonoan, 2021 ), which might have been a significant hurdle in the evolution of pollen‐ and nectar‐eating bees (Filipiak et al., 2023 ). The importance of sodium intake is likely linked to maintaining digestive, excretory, and neuromuscular systems (Molleman, 2010 ).…”

“…Addressing these areas will have implications as sodium availability shifts because of altered ungulate distributions and their urine inputs (McNaughton et al., 1997 ), runoff from road salts (Mattson & Godfrey, 1994 ), and broad‐scale patterns from changing precipitation (Hassani et al., 2021 ). Especially in sodium‐poor regions far from the coast (e.g., Kaspari, 2020 ; Kaspari et al., 2014 ), changes in sodium availability may alter plant physiology, the abundance of invertebrate consumers (Filipiak et al., 2023 ; Kaspari & Welti, 2023 ), and ultimately the frequency and structure of plant–pollinator interactions.…”