62.4 Saturday, Jan. 5 The effects of rare events on climate-driven range expansion/contraction in marine communities ROGNSTAD, R.L.*; WETHEY, D.S.; HILBISH, T.J.; Univ. of South Carolina, Columbia; Univ. of South Carolina, Columbia; Univ. of South Carolina, Columbia firstname.lastname@example.org
Species’ distributions are frequently determined by temperature and thus species’ range limits experience expansions and contractions as climate changes. Shifts in range limits are not always linear and rare climatic events can potentially counteract or exacerbate the effects of climate change on species’ distributions. Temperature affects range limits via multiple mechanisms, both direct, such as heat-induced mortality, and indirect, such as reducing growth or inhibiting reproduction. We assessed the effects of recent extraordinarily cold winters on the southern range limit of the arctic acorn barnacle, Semibalanus balanoides, in Southwestern England. Additionally, we examined the historical frequency of such events to determine whether rare cold events could be responsible for observed historical and contemporary oscillations in the density and southern range limit of S. balanoides. We found that recent cold winters have led to a range expansion of S. balanoides, likely because temperatures are now meeting the critical temperature for reproduction of this species. However, the frequency of such cold winters, which are necessary for S. balanoides persistence in the area, has declined over the past thirty years. If repeated cold events occur within the lifespan of S. balanoides, there is potential for a storage effect and the species could persist in an area, even when faced with unsuitable years caused by warming. We also investigate the interplay between cold winters, which promote reproduction, and cold summers, which reduce mortality. This study demonstrates the importance of considering the role of rare events in controlling species’ distributions, particularly when they oppose the overall trend of climate change.