Conservation Implications
One of the most conspicuous examples of ’defaunation in the Anthropocene’ (Dirzo et al., 2014) is the extinction of Galápagos giant tortoises, such as Chelonoidis abingdoni , which became extinct with the death of Lonesome George in 2012. As in other islands, most species extinctions within the Galápagos have been caused by humans (Steadman, Stafford, Donahue, & Jull, 1991). Holocene vertebrate extinctions in Floreana, an island about the size of Washington DC with the most local extinctions in the Galápagos, include two species of reptiles, and 11 birds (Dvorak et al., 2017; Island Conservation, 2013; Steadman, 2006).
Eradication of invasive mammals from islands has proved to be an important tool to prevent extinctions, recover endangered populations, and restore ecosystem processes (Rueda et al., 2019; Russell & Holmes, 2015). As such the Galápagos National Park has eradicated dozens of invasive species populations around the archipelago (Campbell et al., 2013; Carrion et al., 2007; Carrion et al., 2011). Upcoming invasive mammal eradication projects include Floreana Island (Island Conservation, 2013) to prevent extinctions of endemic species such as the Medium tree-finch (Camarhynchus pauper ), Floreana lava lizard, and Floreana leaf-toed gecko. Unfortunately, invasive mammal eradication efforts may result in non-target species mortality; therefore, it is important to identify appropriate mitigation actions (e.g., captive holding in situ , translocation) for species at higher risk, or species for which any risk is unacceptable. In this context, populations unexposed to the eradication process that are identified as the same evolutionary significant unit (ESU) as exposed populations are a great source for future reintroductions if necessary. Our results show that both lava lizard and leaf-toed gecko populations from Champion can be considered the same ESU as populations from Floreana (Fig. 3). Champion lacks introduced mammals and will therefore not be included in Floreana´s eradication program. Consequently, populations of lava lizards and leaf-toed geckos from Champion can be considered as safeguard populations for both species. Finally, if one of the goals is to use a population that was likely part of the same ESU, Champion or other islets with possible Pleistocene land connections to Floreana might be good sources for reintroducing other terrestrial organisms, such as the racer snake Pseudalsophis biserialis , which became extinct in Floreana over a century ago. Nonetheless, we recognize that other factors like the viability of source populations (e.g., Bozzuto, Hoeck, Bagheri, & Keller, 2017) should also be considered as part of any reintroduction plan (Robert et al., 2015).