DNA metabarcoding the diet of Podarcis lizards endemic to the Balearic Islands

Dietary studies are essential to unravel the functioning of ecosystems and ultimately to understand biodiversity.This task,which at first may seem simple,becomes especially complex in those cases of omnivorous species with highly variable diets.In this regard,the emergence of next-generation DNA sequencing methodologies represents a powerful tool to address the problem.Here we implement a high-throughput metabarcoding strategy based on the analysis of four molecular markers aimed at sequencing both mitochondrial(animal prey)and chloroplast(diet plants)genome fragments from fecal samples of two lizard species endemic to the Balearic Archipelago(Podarcis lilfordi and P.pityusensis)obtained through non-invasive methods.The results allowed for the characterization of their diets with a high degree of taxonomic detail and have contributed a large number of new trophic records.The reported diets are based mainly on the consumption of arthropods,mollusks and plants from a diversity of taxonomic orders,as well as carrion and marine subsidies.Our analyses also reveal inter-and intra-specific differences both in terms of seasonality and geographical distribution of the sampled lizard populations.These molecular findings provide new insights into the trophic interactions of these threatened endemic lizards in their unique and isolated ecosystems.

Diet composition of the lizard P odarcis lilfordi (Lacertidae) on 2 small islands: an individualresource network approach

Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes,this level of information has only recently been included into network analysis of species/population interactions.When done,it has revealed non-random patterns in the distribution of trophic resources.Nestedness in resource use among individuals is the most recurrent observed pattern,often accompanied by an absence of modularity,but no previous studies examine bipartite modularity.We use network analysis to describe the diet composition of the Balearic endemic lizard Podarcis lilfordi in 2 islets at population and individual levels,based on the occurrence of food items in fecal samples.Our objectives are to 1)compare niche structure at both levels,2)characterize niche partition using nestedness and modularity,and 3)assess how size,sex,season,and spatial location influence niche structure.At population-level niche width was wide,but narrow at the level of the individual.Both islet networks were nested,indicating similar ranking of the food preferences among individuals,but also modular,which was partially explained by seasonality.Sex and body size did not notably affect diet composition.Large niche overlap and therefore possibly relaxed competition were observed among females in one of the islets and during spring on both islets.Likewise,higher modularity in autumn suggests that higher competition could lead to specialization in both populations,because resources are usually scarce in this season.The absence of spatial location influence on niche might respond to fine-grained spatio-temporally distribution of food resources.Behavioral traits,not included in this study,could also influence resource partitioning.

Collapse of the endemic lizard Podarcis pityusensis on the island of Ibiza mediated by an invasive snake

The invasive snake Hemorrhois hippocrepis colonized the island of Ibiza(Balearic Islands)in 2003 as stowaways inside trunks of olive trees imported for gardening.It has quickly spread since 2010,posing a threat to the island’s only remaining endemic vertebrate,the Ibiza wall lizard Podarcis pityusensis.We map the yearly expansion rate of the snake and estimate via transect surveys how severely it affects the distribution and abundance of the endemic lizard.As well,we surveyed 9 of 30 small lizard populations on islets surrounding Ibiza that have been isolated since the Last Glacial Maximum.Snakes had invaded 49%of Ibiza’s land area by 2018,and censuses show a critical contrast in lizard abundance between areas with and without snakes;almost all censuses in areas without snakes show lizard presence whereas nearly all censuses in areas with H.hippocrepis lack lizard sightings.Moreover,at least one subspecies previously thriving on one of the offshore islets has become extinct,and there have been several snakes recorded swimming between Ibiza and the surrounding islets.Therefore,lizard populations have been dramatically reduced or have vanished within the range of the snake,and our results quantitatively support upgrading this species’threat level for extinction.This study can inform to programs to manage invasive snake populations and to conservation actions to recover the endemic lizard.