Abstract

Introduced species can exert disproportionately negative effects on island ecosystems, but their potential role as food for native consumers is poorly studied. Telfair's skinks are endemic omnivores living on Round Island, Mauritius, a globally significant site of biodiversity conservation. We aimed to determine the dietary diversity and key trophic interactions of Telfair's skinks, whether introduced species are frequently consumed, and if diet composition changes seasonally between male and female skinks. We used DNA metabarcoding of skink fecal samples to identify animals (COI) and plants (ITS2) consumed by skinks. There were 389 dietary presence counts belonging to 77 dietary taxa found across the 73 Telfair's skink fecal samples. Introduced taxa were cumulatively consumed more frequently than other categories, accounting for 49.4% of all detections, compared to cryptogenic (20.6%), native (20.6%), and endemic taxa (9.5%). The most frequently consumed introduced species was the ant, Pheidole megacephala, present in 40% of samples. Blue latan palm, Latania loddigesii, was the most frequently consumed endemic species, present in 33% of samples but was only detected in the dry season, when fruits are produced. We found a strong seasonal difference in diet composition explained by the presence of certain plant species solely or primarily in one season and a marked increase in the consumption of animal prey in the dry season. Male and female skinks consumed several taxa at different frequencies. These results present a valuable perspective on the role of introduced species in the trophic network of their invaded ecosystem. Both native and introduced species provide nutritional resources for skinks, and this may have management implications in the context of species conservation and island restoration.

Highlights

  • A novel species introduced into a new ecosystem can interact with taxa already present in a variety of ecological roles, for example, as a mutualist (Kaiser-­Bunbury et al, 2011), competitor (Cole & Harris, 2011), predator (O’Dowd et al, 2003), prey (Li et al, 2011), or parasite (Arbetman et al, 2013)

  • Introduced species are typically associated with disproportionately negative effects on island biodiversity (Sax & Gaines, 2009), but are shown to provide nutritional resources to these endemic species

  • Our study represents one of only a few complete dietary analyses of omnivores using DNA metabarcoding and the first study examining the omnivorous diet of a threatened endemic reptile

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Summary

Introduction

A novel species introduced into a new ecosystem can interact with taxa already present in a variety of ecological roles, for example, as a mutualist (Kaiser-­Bunbury et al, 2011), competitor (Cole & Harris, 2011), predator (O’Dowd et al, 2003), prey (Li et al, 2011), or parasite (Arbetman et al, 2013). Introduced species were consumed frequently by the Ogasawara buzzard, Buteo buteo oyoshim, with 90% of its diet consisting of introduced animals (Kato & Suzuki, 2005) These small oceanic islands harbor high levels of endemism. Introduced species are typically associated with disproportionately negative effects on island biodiversity (Sax & Gaines, 2009), but are shown to provide nutritional resources to these endemic species. This may be more common than currently acknowledged, with introduced species representing a significant dietary element for native consumers

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