Meeting Abstract
The Phoenix Islands Protected Area (PIPA) and Jarvis, a protected US territory, in the central Equatorial Pacific host vibrant coral assemblages safeguarded from direct human impacts, yet remain vulnerable to heat stress. During 2014-16 El Niño, Jarvis experienced >90% coral mortality after a year of high temperatures. Connectivity between healthy and affected reefs can facilitate recovery; however, patterns of gene flow among coral populations in this region are still understudied. We quantified levels of gene flow for the major reef-building coral, Porites lobata, across PIPA and Jarvis using thirteen microsatellite markers. We find significant differentiation among reefs (global FST = 0.02, p<0.0001), with pairwise FST ranging from 0.007-0.09. Principal component analysis and Bayesian clustering methods find that the PIPA is subdivided into two subpopulations: the northeastern (NE) islands of Kanton, Birnie, Enderbury, and Rawaki and the southwestern (SW) islands of Orona, Manra, McKean, and Nikumaroro. During El Niño events, the NE islands can experience strong temperature anomalies and high levels of bleaching and mortality. Our results suggest the SW islands, which experience milder temperature stress and likely lower mortality, may have limited potential to re-populate the NE. The NE may therefore be dependent on self-seeding or dispersal through the equatorial current from reefs further east such as the Line Islands, El Niño events, however, often cause mortality in these reefs also. Region-wide monitoring of El Niño impacts combined with gene flow estimates will improve management of these diverse and remote reefs.
