Historical interactions are predicted to be disrupted under future climate change: The case of lace lichen and valley oak

Abstract

ABSTRACTAimThe distributions and interactions of co‐occurring species may change if their ranges shift asymmetrically in response to rapid climate change. We aim to test whether two currently interacting taxa, valley oak (Quercus lobata) and lace lichen (Ramalina menziesii), have had a long‐lasting historical association and are likely to continue to associate in the future.LocationCentral western California, western United States of AmericaMethodsUsing population genetic analyses and MaxEnt software for ecological niche modelling, we estimate species’ distributions during the Last Interglacial, the Last Glacial Maximum, present, and future periods. Mantel and vertex (genetic connection) tests were used to examine the spatial congruence among taxa. To compare the modelled response to climate change, we estimated migration speed between respective time periods using vector analysis.ResultsWe found significant genetic congruence between valley oak and the lichen's green algal photobiont, independent of geographic isolation and habitat isolation, which is consistent with long‐term association. Ecological niche models under past and future climate scenarios indicate that overlap of climatic niche sharing between valley oak and lace lichen might decrease in the future. Our models indicate that the speed of shifts in climate niches between these two taxa differed significantly in past periods from that of the present period.Main conclusionsOur findings reveal that historical interactions between valley oak and lace lichen correlate with long‐term sharing of past climate niches. However, the future association of lace lichen with valley oak may be disrupted in parts of its current distribution due to differential discordance of climate niche shifts, species’ movements and generation times. This study illustrates the processes and patterns that allow long‐term association during historic climate change and how they are likely to change during rapid climate change.