Insect Conservation and Diversity (2017) 10, 193–199 doi: 10.1111/icad.12219 FORUM & POLICY Coextinction dilemma in the Galapagos Islands: Can Darwin’s finches and their native ectoparasites survive the control of the introduced fly Philornis downsi? 1 2 MARIANA BULGARELLA and RICARDO L. PALMA 1School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand and 2Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand Abstract. 1. The survival of parasites is threatened directly by environmental alter- ation and indirectly by all the threats acting upon their hosts, facing coextinction. 2. The fate of Darwin’s finches and their native ectoparasites in the Galapagos Islands is uncertain because of an introduced avian parasitic fly, Philornis downsi, which could potentially drive them to extinction. 3. We documented all known native ectoparasites of Darwin’s finches. Thir- teen species have been found: nine feather mites, three feather lice and one nest mite. No ticks or fleas have been recorded from them yet. 4. Management options being considered to control P. downsi include the use of the insecticide permethrin in bird nests which would not only kill the invasive fly larvae but the birds’ native ectoparasites too. 5. Parasites should be targeted for conservation in a manner equal to that of their hosts. We recommend steps to consider if permethrin-treated cotton sta- tions are to be deployed in the Galapagos archipelago to manage P. downsi. Key words. Chewing lice, coextinction, Darwin’s finches, dilemma, ectoparasites, feather mites, Galapagos Islands, permethrin, Philornis downsi. Introduction species have closely associated species which are also endangered (Dunn et al., 2009). The same threats affecting Coextinction refers to the loss of one species as the result of free-living species such as global warming and ecosystem the extinction of another species it depends on (Stork & disturbance, reduce the abundance and diversity of parasites Lyal, 1993). This is a process with cascading effects across as well (Bradley & Altizer, 2007; Bush et al., 2013). Thus, trophic levels (Dunn et al., 2009); losing one species from parasites are directly threatened by environmental alteration the ecosystem may imply losing others consequently and indirectly by all the threats acting upon their hosts (Col- because organisms are interconnected (Koh et al., 2004). well et al., 2012; Gomez & Nichols, 2013). A compounded Coextinctions represent a loss of evolutionary history (Pur- effect of the threats experienced by avian hosts, for example, vis et al., 2000), and they might be the most common form would mean that climate change poses a serious threat to the of biodiversity loss, according to different mathematical smaller parasite fauna on polar and temperate regions, while models (Koh et al., 2004; Dunn, 2005, 2009). Documented habitat destruction would be the main threat to parasites in cases of coextinction are, however, extremely scarce (Dunn tropical regions (Dobson et al., 2008). et al., 2009). Either coextinctions are common but happen Until recently, the idea of protecting parasites has not undetected or, they are rare because parasites adapt quickly been a priority for conservation efforts (Durden & Keir- and are more plastic than it is thought (Dunn et al., 2009). ans, 1996) because there is a bias towards conserving free- Tens of thousands of parasites are likely to have disap- living species (Windsor, 1990, 1995) to whom humans can peared due to coextinction and many endangered host put an emotional or recreational value. As an example, the IUCN Red List of Threatened Species only includes one parasite species as endangered (Whiteman & Parker, Correspondence: Mariana Bulgarella, School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 2005; Dunn et al., 2009). Parasitic organisms form great 6140, New Zealand. E-mail: [email protected] part of biodiversity (Price, 1980). Besides having Ó 2017 The Royal Entomological Society 193 194 Mariana Bulgarella and Ricardo L. Palma Table 1. List of ectoparasites recorded from Darwin’s finches in the Galapagos Islands (Records due to natural straggling or contamina- tion by human agency have not been included). Common name Order Family Species Host species References Feather Sarcoptiformes Psoroptoididae Mesalgoides geospizae Geospiza conirostris Mironov and Perez (2002) mite Geospiza fortis O’Connor et al. (2005) Geospiza fuliginosa Villa et al. (2013) Geospiza magnirostris Geospiza scandens Camarhynchus parvulus Camarhynchus pallidus Camarhynchus psittacula Platyspiza crassirostris Certhidea olivacea Feather Sarcoptiformes Xolalgidae Xolalgoides palmai Geospiza fortis Mironov and Perez (2002) mite Geospiza fuliginosa O’Connor et al. (2005) Geospiza magnirostris Villa et al. (2013) Geospiza scandens Camarhynchus parvulus Camarhynchus psittacula Platyspiza crassirostris Certhidea olivacea Feather Sarcoptiformes Trouessartiidae Trouessartia geospiza Geospiza fortis O’Connor et al. (2005) mite Geospiza fuliginosa Lindstrom€ et al. (2009) Geospiza magnirostris Villa et al. (2013) Geospiza scandens Camarhynchus parvulus Camarhynchus pallidus Camarhynchus psittacula Platyspiza crassirostris Certhidea olivacea Feather Sarcoptiformes Proctophyllodidae Proctophyllodes darwini Geospiza fortis O’Connor et al. (2005) mite Geospiza fuliginosa Villa et al. (2013) Geospiza magnirostris Geospiza scandens Camarhynchus parvulus Camarhynchus pallidus Camarhynchus psittacula Platyspiza crassirostris Certhidea olivacea Feather Sarcoptiformes Proctophyllodidae Amerodectes atyeoi Geospiza difficilis O’Connor et al. mite Geospiza fortis (2005, as Pterodectes) Geospiza fuliginosa Villa et al. (2013) Geospiza magnirostris Geospiza scandens Camarhynchus parvulus Camarhynchus pallidus Camarhynchus psittacula Platyspiza crassirostris Certhidea olivacea Feather Sarcoptiformes Analgidae Strelkoviacarus sp. Geospiza fortis O’Connor et al. (2005) mite Geospiza fuliginosa Villa et al. (2013) Camarhynchus parvulus Certhidea olivacea Feather Sarcoptiformes Analgidae Analges sp. Certhidea olivacea Villa et al. (2013) mite Feather Sarcoptiformes Dermoglyphidae Dermoglyphus sp. Geospiza fortis O’Connor et al. (2005) mite Geospiza fuliginosa Villa et al. (2013) Geospiza scandens (continued) Ó 2017 The Royal Entomological Society, Insect Conservation and Diversity, 10, 193–199 Conserving native ectoparasites of Darwin’s finches 195 Table 1. (continued) Common name Order Family Species Host species References Camarhynchus pallidus Platyspiza crassirostris Nest Parasitiformes Dermanyssidae Dermanyssus sp. Geospiza fuliginosa O’Connor et al. (2005) mite Feather Phthiraptera Menoponidae Myrsidea darwini Geospiza fuliginosa Palma and Price (2010) louse Geospiza magnirostris Palma and Peck (2013) Camarhynchus psittacula Feather Phthiraptera Philopteridae Brueelia chelydensis Geospiza conirostris Palma and Peck (2013) louse Geospiza difficilis Geospiza fortis Geospiza fuliginosa Geospiza magnirostris Camarhynchus pallidus Camarhynchus parvulus Camarhynchus psittacula Certhidea olivacea Feather Phthiraptera Philopteridae Brueelia interposita Geospiza difficilis Palma and Peck (2013) louse Geospiza fortis Geospiza fuliginosa Geospiza magnirostris Camarhynchus psittacula Platyspiza crassirostris Feather Phthiraptera Philopteridae Philopterus insulicola Certhidea olivacea Palma and Peck (2013) louse extraordinary species richness (Windsor, 1998) and biomass Thraupidae. They evolved from a single group of ances- (Kuris et al., 2008), parasites contribute to important tors that colonised the Galapagos Islands 2–3 million ecosystems functions and services as they occupy key roles years ago from Central or South America (Farrington & in food webs (Hudson et al., 2006; Strona, 2015), they may Petren, 2009). One of these, the Cocos Island finch be indicators of ecosystem health (Marcogliese, 2005), and (Pinaroloxias inornata) occurs only on Cocos Island. are relevant in increasing genetic diversity of natural popu- Therefore, the Galapagos radiation would comprise 15 lations (Coltman et al., 1999; O’Brien, 2000). In addition, finch species that include seven ground finches (Geospiza parasite population genetics is a useful tool to infer host’s spp.), five tree finches (Camarhynchus spp.), the vegetarian population history (Whiteman & Parker, 2005). finch (Platyspiza crassirostris) and two warbler finches The relevance of parasites in natural ecosystems leaves (Certhidea spp.). We follow the avian taxonomic classifi- us with an important dilemma that needs to be addressed cation of the Cornell University (2016) Neotropical Birds and dealt with: should native parasites be saved when a website (http://neotropical.birds.cornell.edu/) where the free-living species is managed for its conservation? (Perez vampire finch, Geospiza septentrionalis, is not recognised et al., 2013). The case of a host specific louse living on as a separate species. Most of Darwin’s finches occur on the Californian condor, which became extinct because of more than one island of the Galapagos archipelago but the conservation efforts to save its host, is a classic there are two species of major conservation concern. The example of that dilemma (Windsor, 1990; Stork & Lyal, mangrove finch (Camarhynchus heliobates) with <100 indi- 1993; Anonymous, 2006). Here, we are concerned viduals is restricted to Isabela Island (Lawson et al., about the fate of the Darwin’s finches and their native 2017), and the medium tree finch (Camarhynchus