Author's personal copy Syst Parasitol (2011) 80:53–66 DOI 10.1007/s11230-011-9311-1 A phylogenetic assessment of the colonisation patterns in Spauligodon atlanticus Astasio-Arbiza et al., 1987 (Nematoda: Oxyurida: Pharyngodonidae), a parasite of lizards of the genus Gallotia Boulenger: no simple answers Fa´tima Jorge • Vicente Roca • Ana Perera • D. James Harris • Miguel A. Carretero Received: 17 February 2011 / Accepted: 10 April 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Parasite taxonomy traditionally relies on required for a more complete interpretation of the morphometric and life-cycle characteristics which evolution of this genus from the Canarian archipelago may not reflect complex phylogenetic relationships. and its closest taxa. Our results emphasise the impor- However, genetic analyses can reveal cryptic species tance of extensive sampling and phylogenetic studies within morphologically described parasite taxa. We at the intrageneric level, and highlight the limitations of analysed the phylogenetic variation within the nema- a morphologically based taxonomy in these parasites. tode Spauligodon atlanticus Astasio-Arbiza, Zapatero- Ramos, Ojeda-Rosas & Solera-Puertas, 1987, a para- site of the Canarian lizard genus Gallotia Boulenger, Introduction inferring the origin of their current association. We also attempted to determine its relationship with other Our knowledge of comparative phylogenies of para- Spauligodon spp. Three different markers, mitochon- sites and their hosts constitutes a key point for drial COI plus nuclear 18S and 28S ribosomal RNA, interpreting their association within an evolutionary were used to estimate the evolutionary relationships context. Determining the origins of such associations between these nematodes. S. atlanticus was found to be (Banks & Paterson, 2005) and the events that have paraphyletic, suggesting that Gallotia spp. were col- shaped their present distribution (Paterson et al., onised by two independent lineages of Spauligodon. 2003), ultimately through a co-evolutionary pathway, Additional analyses of other Spauligodon spp. are has been the aim of numerous studies (Hugot et al., 2001; Johnson et al., 2003; Chilton et al., 2004; Clayton et al., 2004; Banks et al., 2006; Light & Reed, & F. Jorge ( ) Á A. Perera Á D. J. Harris Á M. A. Carretero 2009). Host-parasite associations could arise through CIBIO-UP, Centro de Investigac¸a˜o em Biodiversidade e Recursos Gene´ticos, Campus Agra´rio de Vaira˜o, descendency, when each host species inherited the 4485-661 Vaira˜o, Portugal association from its ancestor, or by colonisation, e-mail: [email protected] where the parasite switches to a new host lineage or species other than the host ancestor (Banks & V. Roca Departament de Zoologı´a, Facultat de Cie`ncies Paterson, 2005). However, several events could shape Biolo`giques, Universitat de Vale`ncia, Dr. Moliner, 50, the current distribution of the parasite-host associa- 46100 Burjassot, Valencia, Spain tions, resulting only rarely in a perfect match between both phylogenies (Page, 2003). Rather than tracking D. J. Harris Departamento de Biologia, Faculdade de Cieˆncias da their host with perfect fidelity, parasites may switch Universidade do Porto, 4099-002 Porto, Portugal lineages, speciate independently of their host, go 123 Author's personal copy 54 Syst Parasitol (2011) 80:53–66 extinct (sorting), fail to colonise all the descendants of 2008). They are located approximately 100 km from a host lineage, or fail to speciate when the host does. the north-western coast of Africa, forming a chain of On the other hand, events other than co-speciation, seven main islands and several islets. The archipelago such as geographical differentiation (Callejo´n et al., was formed in an east-to-west formation during the 2010), may generate ‘‘false’’ congruent host and last 20 million years (Ma) (Guillou et al., 2004; parasite phylogenies (Clayton et al., 2003). Ancochea et al., 2006; Fig. 1). Previous phylogenies Until recently, the taxonomy of parasites had relied also suggest that the colonisation of the archipelago on the analysis of their morphological and life-cycle by some taxa follows a stepping-stone model from traits. However, parasites often present a simplified older to younger islands (Sanmartı´n et al., 2008). morphology, and molecular techniques are starting to However, in the case of lizards of the genus Gallotia show that many presumed single species actually this is not so clear (Cox et al., 2010). The ancestor consist of genetically different parasite lineages, colonised the Canary Islands in the Miocene, between suggestive of cryptic species (Blouin, 2002; Miura 17 to 20 Ma ago (Cox et al., 2010), soon after the et al., 2005; Gutie´rrez-Gutie´rrez et al., 2010). The lack formation of the easternmost islands. Gallotia is the of morphological differentiation between related only endemic lacertid genus in the archipelago, with parasite species may be due to similar selective seven recognised living species (Maca-Meyer et al., pressures promoting morphological convergence in 2003; Cox et al., 2010), three of which are considered species that are not closely related (Banks & Paterson, threatened. The Gallotia spp. can be grouped in two 2005). This event, although difficult to recognise well-differentiated size groups, one formed by small using traditional morphological traits, is easily char- to medium-sized lizards (maximum snout-vent acterised using a molecular approach. The existence length, SVL, 67-136 mm) including G. atlantica, of unidentified cryptic species can result in erroneous G. galloti and G. caesaris, and a second group of interpretations of parasite-host associations, such as giant lizards (SVL 201-232 mm) formed by the other the assignment of parasites as multi-host species. four species (G. bravoana, G. simonyi, G. intermedia Multi-host parasites may still result from other events, and G. stehlini) plus the extinct G. goliath (see such as misclassified (over-split) hosts, recent host- Barahona et al., 2000). In contrast to most lacertid switches, failures to speciate or incomplete host- lizards, Gallotia spp. are generally considered omniv- switches (Banks & Paterson, 2005). Thus, an assess- orous but with a high trend towards herbivory (Martı´n ment of the genetic diversity of parasites can enlighten et al., 2005; Roca et al., 2005; Carretero et al., 2006; various aspects of host-parasite relationships. Rodrı´guez et al., 2008). This trend is confirmed Spauligodon Skrjabin, Schikhobalova & Lag- in their helminth communities (Roca et al., 2005). odovskaja, 1960 (Oxyurida) is a cosmopolitan genus S. atlanticus is part of the nematode evolutionary of intestinal nematodes that comprises at least 46 lineage that typically parasitises carnivorous lizards described species (Binh et al., 2007; Bursey et al., (Roca, 1999; Roca et al., 2005). The prevalence of 2007; Monks et al., 2008), with 20 of them occurring S. atlanticus in Gallotia spp. varies between 5.6% (in in the Palaearctic region (Bursey et al., 2005). G. atlantica laurae Castroviejo, Mateo & Collado S. atlanticus Astasio-Arbiza, Zapatero-Ramos, Oje- from Lanzarote) and 59.3% (in G. galloti palmae da-Rosas & Solera-Puertas, 1987 was described as an Boettger & Mu¨ller from La Palma) (Martı´n, 2005). obligate parasite specific to lacertid lizards of the Considering its distribution and morphological diag- genus Gallotia Boulenger endemic to the Canary nosis, S. atlanticus appears to be a multi-host Islands (Martı´n & Roca, 2005). This nematode parasite, restricted to different Gallotia spp. belongs to the Family Pharyngodonidae, members Our current knowledge, therefore, gives rise to of which infect reptiles (Roca, 1999; Roca et al., several intriguing questions: (i) does S. atlanticus 2005). Since it has a monoxenus life-cycle with no constitute a single evolutionary lineage or does it free-living stages (Sa´nchez, 1996), parasite gene flow comprise multiple cryptic species; (ii) is there is strictly dependent on movements and contacts co-differentiation between the parasite and its between hosts which display low dispersal abilities. host; and (iii) what are the relationships between The Canary Islands are one of the most studied S. atlanticus and other members of the genus. In view volcanic archipelagos in the world (Sanmartı´n et al., of these, we assessed for the first time the phylogeny of 123 Author's personal copy Syst Parasitol (2011) 80:53–66 55 Fig. 1 Map of the Canary Islands with the approximate ages of the islands (from Carracedo et al., 1998; Guillou et al., 2004) and the geographical localities of Spauligodon samples included in the analyses (See Table 1 for details). (a) South Europe, North Africa and Caucasus. (b) Canary Islands. (c) Armenia. Abbreviation: Ma, million years S. atlanticus and related species using three different (Table 1; Fig. 1). Two of them are endangered and genes with different rates of evolution, the mitochon- could not be sampled due to conservation restrictions. drial cytochrome oxidase subunit I and two nuclear The third, Gallotia stehlini Schenkel from Gran ribosomal genes, the 18S rRNA and the 28S rRNA. Canaria was sampled, but the nematode species could not be found. Nematodes were extracted by necropsy (lizard vouchers are deposited in the Herpetological Materials and methods collection of CIBIO, University of Porto, Portugal) or from fresh pellets dropped by lizards collected in the Specimen collection field but subsequently released. Similarly,