Extremes: understanding flower-visitor interactions in a changing climate

Abstract

We argue here that climate change studies which focus only on single species will be inadequate to address the complexity of causal mechanisms, as climate effects will percolate through entire ecological communities. Changes in species distributions may be considered as: 1) fully independent, in which case each species will respond directly to environmental factors; 2) dependent upon a set of biological interactions among species; or 3) of a combination of both environmental and biological factors. Our second point is that climate extremes will drive substantial change beyond any changes in averages-and that it is these rare outlier events that are most likely to be relevant for Australia and for the arid zone in particular. A corollary of this point is that at present, the extremes, e.g. rainfall in the arid zone, are currently unpredictable and this unpredictability is likely to further increase as the extremes increase. This could lead to events of greater severity, more frequent extreme events of current magnitude, or a combination of both. It is not known to what extent the Southern Oscillation Index and the El Niño/ La Niña cycles will be altered. We illustrate our case by considering the interactions among flowering plants and their floral visitors in the Simpson Desert.

Extreme climatic events drive mammal irruptions: regression analysis of 100‐year trends in desert rainfall and temperature

“…; Bellard et al. ; Popic and Wardle ). Finally, the risk of wildfires increases after two consecutive years of rainfall that exceeds the 91st quantile in the study region (Letnic and Dickman ; Greenville et al.…”

“…Top-down processes then may become stronger and more pervasive, reducing small mammal populations to very low levels during droughts ( Letnic et al 2011 ). Third, other novel interactions may develop; these include extended floral–pollinator networks that can be supported during periods of high productivity, and hyperpredation of seeds, green vegetation, and invertebrates that can arise when rodent populations are high ( Brown et al 1997 ; Bellard et al 2012 ; Popic and Wardle 2012 ). Finally, the risk of wildfires increases after two consecutive years of rainfall that exceeds the 91st quantile in the study region ( Letnic and Dickman 2006 ; Greenville et al 2009 ).…”

“…), with extreme rainfall events (>90th quantile) driving interactions most strongly (Holmgren et al. ; Letnic and Dickman ; Smith ; Popic and Wardle ). These pulse events are variable in time and space and often short lived (1–2 years), yet the resources they generate drive population “booms” in consumer organisms such as small mammals through bottom‐up processes, provide prey for predators, and increase fuel loads that result in wildfires (Letnic and Dickman ; Pavey et al.…”

“…For example, temperatures exceeding 42°C cause death of flying foxes due to heat stress ( Welbergen et al 2008 ); hot conditions during drought can even cull populations of many specialist desert organisms ( Low 2011 #1305; McKechnie, 2012 #1382; Fensham, 1999 #1385). In arid environments rainfall stimulates increases in primary productivity ( Noy-Meir 1973 ; Morton et al 2011 ), with extreme rainfall events (>90th quantile) driving interactions most strongly ( Holmgren et al 2006 ; Letnic and Dickman 2006 ; Smith 2011b ; Popic and Wardle 2012 ). These pulse events are variable in time and space and often short lived (1–2 years), yet the resources they generate drive population “booms” in consumer organisms such as small mammals through bottom-up processes, provide prey for predators, and increase fuel loads that result in wildfires ( Letnic and Dickman 2006 ; Pavey et al 2008 ; Greenville et al 2009 ; Letnic et al 2011 ).…”

Desert mammal populations are limited by introduced predators rather than future climate change

“…Climate change may have different effects if the interactions or processes are positive or negative, leading to unpredictable changes in the composition of species assemblages. Identifying the importance of particular biotic interactions and other processes within broader networks is difficult, particularly when multiple trophic levels are involved, but can be useful for detecting the first evidence of environmental change [ 12 ]. For example, small shifts in plant phenology may have large effects on mutualisms, such as plant–pollination networks [ 13 ].…”