Plant–pollinator interactions and phenological change: what can we learn about climate impacts from experiments and observations?

Abstract

Climate change can aff ect plant -pollinator interactions in a variety of ways, but much of the research attention has focused on whether independent shifts in phenology will alter temporal overlap between plants and pollinators. Here I review the research on plant -pollinator mismatch, assessing the potential for observational and experimental approaches to address particular aspects of the problem. Recent, primarily observational studies suggest that phenologies of co-occurring plants and pollinators tend to respond similarly to environmental cues, but that nevertheless, certain pairs of interacting species are showing independent shifts in phenology. Only in a few cases, however, have these independent shifts been shown to aff ect population vital rates (specifi cally, seed production by plants) -but this largely refl ects a lack of research. Compared to the few long-term studies of pollination in natural plant populations, experimental manipulations of phenology have yielded relatively optimistic conclusions about eff ects of phenological shifts on plant reproduction, and I discuss how issues of scale and frequency-dependence in pollinator behaviour aff ect the interpretation of these ' temporal transplant ' experiments. Comparable research on the impacts of mismatch on pollinator populations is so far lacking, but both observational studies and focused experiments have the potential to improve our forecasts of pollinator responses to changing phenologies. Finally, while there is now evidence that plant -pollinator mismatch can aff ect seed production by plants, it is still unclear whether this phenological impact will be the primary way in which climate change aff ects plant -pollinator interactions. It would be useful to test the direct eff ects of changing climate on pollinator population persistence, and to compare the importance of phenological mismatch with other threats to pollination.

The influence of El Niño and edge effects on the reproductive phenology and floral visitors of Eschweilera tetrapetala Mori (Lecythidaceae), an endemic species of the Atlantic Forest of northeastern Brazil

“…Changes in the reproductive phenologies of plants can result in the temporal asynchrony of plant-pollinator interactions, with plant species flowering when pollinator activities have already concluded, or not yet initiated (Bartomeus et al 2011;Forrest 2015). Such asynchrony can negatively affect plant and/or animal populations, reducing resource availability for animals and/or reducing the reproductive potentials of plants (Rusterholz & Erhardt 1998;Kudo et al 2004;Thomsom 2010).…”

Examining plant physiological responses to climate change through an evolutionary lens

“…Climate change effects on plant and pollinator physiology also may result in mismatches between flowering time and pollinator activity (Forrest, 2015). Many plant species are emerging and reproducing earlier in the year due to increasing temperature and [CO 2 ] (Amano et al, 2010;Ward et al, 2012;CaraDonna et al, 2014), while some species are delaying phenological events or are unresponsive to climate change (Sherry et al, 2007;Cook et al, 2012).…”

“…Climate change may alter such cues, resulting in dramatic shifts in flowering time (Springer et al, 2008;Wahl et al, 2013). If plants and their pollinators differ in their environmental sensitivities, then climate change could induce asynchronous phenologies, which could modify patterns of gene flow (Elzinga et al, 2007), alter coevolutionary dynamics between pollinators and plants (Gilman et al, 2012), reduce seed production (Forrest, 2015), and limit resource availability for pollinators (Memmott et al, 2007; but see Forrest and Thomson, 2011). Predicting the extent of temporal asynchrony under future climates will require physiological studies that determine the specific environmental cues that elicit life history transitions in plants and pollinators.…”

“…Our understanding of climate change effects on species interactions has grown considerably in recent years (Kiers et al, 2010;Robinson et al, 2012;Forrest, 2015); however, the potential for climate change to affect plant physiological evolution through species interactions is not well understood. Given the complexity of plant-species interactions and their potential to drive evolution, studies that simulate climate change under realistic natural conditions with a full complement of interacting species could reveal plant physiological and evolutionary responses to direct and indirect effects of novel climates (Barton et al, 2009).…”

Population-level genetic variation and climate change in a biodiversity hotspot

“…The loss of generalist pollinators such as E. propertius at a large scale has the potential to be devastating to plant taxa dependent on outcrossing. Specialist pollinators are expected to be the most vulnerable to extinction when plant-pollinator phenologies are decoupled, but further experimentation is necessary to make more accurate predictions (Forrest, 2015).…”