Guest essay by Eric Worrall
h/t The Register – A study published in Science claims that global warming is shortening the tongues of Bumble Bees, which may impact the ability of their tongues to reach the bottom of deep tube flowers.
The abstract of the study;
Functional mismatch in a bumble bee pollination mutualism under climate change
Ecological partnerships, or mutualisms, are globally widespread, sustaining agriculture and biodiversity. Mutualisms evolve through the matching of functional traits between partners, such as tongue length of pollinators and flower tube depth of plants. Long-tongued pollinators specialize on flowers with deep corolla tubes, whereas shorter-tongued pollinators generalize across tube lengths. Losses of functional guilds because of shifts in global climate may disrupt mutualisms and threaten partner species. We found that in two alpine bumble bee species, decreases in tongue length have evolved over 40 years. Co-occurring flowers have not become shallower, nor are small-flowered plants more prolific. We argue that declining floral resources because of warmer summers have favored generalist foraging, leading to a mismatch between shorter-tongued bees and the longer-tubed plants they once pollinated.
The full study suggests that Theoretical and empirical studies alike suggest that with lower floral resources, fitness advantages of long-tongued specialist phenotypes have diminished, potentially driving the rapid evolution of shorter-tongued bees.
Even if we accept the premise of the study, that harsher conditions are strongly selecting for bees with shorter tongues, it seems curious that the alleged shortage of bees with long tongues, and the implicit inability of available bees to satisfactorily pollinate deep tube flowers, doesn’t seem to be forcing deep tube flowers to evolve shorter tubes.