Genomic recovery lags behind demographic recovery in bottlenecked
populations of the Channel Island fox, Urocyon littoralis
Abstract
With continued global change, recovery of species listed under the
Endangered Species Act is increasingly challenging. One rare success was
the recovery and delisting of the Channel Island fox (Urocyon
littoralis) after 90-99% population declines in the 1990s. While their
demographic recovery was dramatic, less is known about their genetic
recovery. To address genetic changes we conducted the first
multi-individual and population-level direct genetic comparison of
samples collected before and after the recent bottlenecks. Using whole
exome sequencing, we found that already genetically depauperate
populations were further degraded by the 1990s declines and remain low,
particularly on San Miguel Island which underwent one of the most severe
bottlenecks. The three other islands that experienced recent bottlenecks
(Santa Rosa, Santa Cruz, and Santa Catalina islands) showed mixed
results based on multiple metrics of genetic diversity. Previous island
fox genomics studies showed low genetic diversity before the declines
and no change after the demographic recovery, thus this is the first
study to show a decrease in genetic diversity over time in U.
littoralis. Additionally, we found that divergence between populations
consistently increased over time, complicating prospects for using
inter-island translocation as a conservation tool. The Santa Catalina
subspecies is now federally listed as threatened, yet other de-listed
subspecies are still recovering genetic variation which may limit their
ability to adapt to changing environmental conditions. This study
further demonstrates that species conservation is more complex than
population size and that some island fox populations are not yet “out
of the woods”.