Phenotypic plasticity in bighorn sheep reproductive phenology: from individual to population

Consistent within‐individual plasticity is sufficient to explain temperature responses in red deer reproductive traits

“…A lack of substantial difference between females in their response to temperature is interesting, particularly given the range of environmental conditions experienced by individuals in this population over multiple decades. Similarly, a recent study of common terns ( Sterna hirundo ) found little support for individual variation in plasticity of lay date in response to temperatures experienced during the nonbreeding period, despite large sample sizes (Dobson et al., ), and a study of big horn sheep found no variation in plasticity of parturition date in response to autumn temperature or precipitation (Renaud et al., ). These results imply no potential either for genotype–environment interactions (GxE), nor for selection on individual plasticity—both of which would be required for plasticity itself to evolve (Gienapp & Brommer, ).…”

“…Thus, for example in a Canadian population of tree swallows ( Tachycineta bicolor ), within‐individual plasticity in breeding time in response to spring temperatures is equivalent to the population‐level change (Bourret, Bélisle, Pelletier, & Garant, ), and in barn swallows ( Hirundo rustica ) breeding in Denmark, within‐individual plasticity is sufficient to explain overall associations between body condition and vegetation measures (NDVI) in one part of the migration route (Balbontin et al., ). A recent study of bighorn sheep ( Ovis canadensis ) in Alberta, Canada, found that within‐individual plasticity in response to autumn precipitation explained the population‐level association with parturition date (Renaud, Pigeon, Festa‐Bianchet, & Pelletier, ). Other studies have separated within‐ from between‐individual level changes in response to climate, but without explicitly testing whether within‐individual plasticity was sufficient to explain the population‐level responses to changing climate (Dehnhard et al., ; Dobson, Becker, Arnaud, Bouwhuis, & Charmantier, ; Hinke, Polito, Reiss, Trivelpiece, & Trivelpiece, ; Lane, Kruuk, Charmantier, Murie, & Dobson, ; Lane et al., ).…”

“…The phenology of reproduction in long‐lived mammals such as ungulates differs because long gestation periods often create a considerable time lag between conception and parturition (Boutin & Lane, ). Relationships between climate and traits such as calving date may therefore be more complex, acting over longer time frames (Renaud et al., ). Plasticity in these traits may not necessarily be adaptive, but may be simply a consequence of changes in food availability and/or thermoregulatory requirements influencing individual condition at the time of conception (typically in the previous year); this contrasts with avian systems where plasticity in phenology can enable females to coincide offspring hatching with peak food abundance (e.g.…”

“…Similarly, a recent study of common terns (Sterna hirundo) found little support for individual variation in plasticity of lay date in response to temperatures experienced during the nonbreeding period, despite large sample sizes (Dobson et al, 2017), and F I G U R E 4 Power to detect betweenindividual differences in plasticity, IxE (solid lines) and proportion of variance explained by IxE, r IxE (dashed lines) for different values of slope variance (V S ) for a) calving date and b) calf birth weight. The vertical grey lines indicate the value of V S for which power is 80% a study of big horn sheep found no variation in plasticity of parturition date in response to autumn temperature or precipitation (Renaud et al, 2019). These results imply no potential either for genotype-environment interactions (GxE), nor for selection on individual plasticity-both of which would be required for plasticity itself to evolve (Gienapp & Brommer, 2014).…”

Genetic and Environmental Indicators of Climate Change Vulnerability for Desert Bighorn Sheep

“…Of the in situ mechanisms for adaptation to climate change, plastic responses may be at least as important as evolutionary responses for many species (Hoffmann and Sgro, 2011), although these two mechanisms can be difficult to distinguish (Merilä and Hendry, 2014). Experimental or observational studies of plasticity could provide useful information for prioritizing vulnerable desert bighorn populations (e.g., Renaud et al, 2019).…”