Stable isotope analyses suggest Mus musculus occupies the place of the “possibly extinct” Peromyscus guardia in Angel de la Guarda Island, (Mexico)

Abstract

According the IUCN Red List criteria, species must be tagged as “possibly extinct” when there is a small chance that they may be extant. This means that the formal acceptance of the extinction is very dependent on search effort. Here, we report two unsuccessful attempts to detect the critically endangered (possibly extinct) Peromyscus guardia on Angel de la Guarda Island (Gulf of California, Mexico). Instead, we found that invader house mice seem to be very abundant just at the same habitat (beaches) where P. guardia were lastly reported. We analyzed the isotopic niche of the house mice, confirming that the species is currently occupying the presumed trophic niche (common use of marine resources: stranded remains and littoral invertebrates) of the last known populations of P. guardia. The apparent replacement of the specialized endemic species by the ubiquitous house mouse is a new evidence of the current trend towards global biodiversity homogenization.