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).