Many populations are spatially-structured and exist as metapopulations, with distinct patches connected through movement and exchange of individuals. Understanding the dynamics of metapopulations and how they are connected and persist is particularly challenging in the marine environment, where much of the connectivity takes place through tiny larvae. A metapopulation can persist either by individual patches retaining enough of their own offspring to exist in isolation – termed self-persistence – or through exchange among patches that provides sufficient recruits for a patch to persist within the network – called network persistence. Though there has been much theoretical development of persistence mechanisms, they have not been well tested in empirical systems.
We use a model system of yellowtail clownfish (Amphiprion clarkii) in the Philippines to understand connectivity and persistence in an empirical marine metapopulation. Clownfish are particularly well-suited to metapopulation studies because they have limited movement as adults, a relatively short pelagic larval duration, and distinct habitat patches at a range of scales in our study site. Using mark-recapture and genetic parentage methods, we seek to estimate survival, reproduction, and dispersal within this system to understand and characterize persistence mechanisms.
Results/Conclusions
The 17 subpopulations at our study site have persisted throughout seven sampling years with stable abundance and similar size distributions throughout that time, suggesting the overall metapopulation is persistent. Our preliminary estimates from mark-recapture suggest that adult fish have an approximately 23% survival rate from year to year, and that we have about a 42% probability of recapturing a fish each year, though confidence bounds remain wide. Based on the genetic parentage analyses, we find only a few juveniles that return to their patch of origin after pelagic dispersal, though about a third of the recruits in the entire metapopulation are either half or full siblings. This finding supports the potential for self-persistence for some of the larger subpopulations, but network persistence is likely required for overall metapopulation persistence in this system.