The Iberian and North African Podarcis

The Podarcis group that inhabits the Iberian Peninsula and North Africa region, except for Podarcis muralis (Laurenti, 1768), form a monophyletic group (Harris & Arnold, 1999; Oliverio et al., 2000) which has been described as the Podarcis hispanicus (Steindachner, 1870) complex. Several evolutionary lineages have been identified in this species complex, following numerous molecular, morphological, and ecological studies (e.g., Harris et al., 2002; Harris & Sá-Sousa, 2002; Sá-Sousa & Harris, 2002; Pinho et al., 2006, 2008; Geniez et al., 2007, 2014; Lima et al., 2009; Renoult et al., 2009, 2010; Kaliontzopoulou et al., 2011, 2012). Currently, seven lineages are recognized as full species in this species complex (Uetz et al., 2020): Podarcis liolepis (Boulenger, 1905), Podarcis bocagei (Lopez-Seoane, 1885), Podarcis carbonelli (Perez-Mellado, 1981), Podarcis vaucheri (Boulenger, 1905), Podarcis guadarramae (Boscá, 1916), Podarcis virescens (Geniez et al., 2014), and the nominal taxon Podarcis hispanicus (Steindachner, 1870). The latter is a paraphyletic group that could include three different mitochondrial DNA (mtDNA) lineages: Valencia lineage, Galera lineage (Pinho et al., 2006, Geniez et al., 2007, Kaliontzopoulou et al., 2011), and Albacete/Murcia lineage (Kaliontzopoulou et al., 2011).

The taxonomy and classification of this group of species is still under review. The most recent geographical distribution (Caeiro-Dias et al., 2018) (Figure 2) of these species indicates that P. bocagei inhabits the northwest Iberian Peninsula and P. carbonelli has a fragmented distribution along the western Iberian Peninsula. Podarcis guadarramae includes two subspecies, P. g. lusitanicus, which inhabits northwest and central Iberia; and P. g. guadarramae, which occupies the central area of the Peninsula. P. virescens is found in central and southwest Iberia overlapping with P. guadarramae, although with different ecological affinities (altitude and temperature). Podarcis vaucheri inhabits the southern part of the Iberian Peninsula and northern regions of African territories such as Morocco and Algeria. Podarcis liolepis occupies the northeast of the Peninsula and southern regions of France. The lizards that inhabit the Columbretes Islands (Castellón, Spain) belong to this species (Harris & Sousa, 2002; Renoult et al., 2010).

The paraphyletic group of P. hispanicus includes the forms that have not yet been elevated to species rank or assigned to one of the other recognized species. The forms that comprise this group (Galera, Valencia, and Albacete/Murcia lineages) inhabit the southeast (SE) Iberian Peninsula.

The actual phylogeny of this group based on mtDNA alignment of 2,291 bp (corresponding to fragments from 12S rRNA, 16S rRNA, control region, cytochrome b, and ND4) (Kaliontzopoulou et al., 2011) differentiates three groups. On the one hand, i) a group made up of two lineages from eastern Iberia (P.

liolepis in the northeast and southern France, including the Columbretes Islands, and Galera lineage in the SE) that occupies a basal position in the phylogeny. On the other hand, two sister subclades: ii) one in west and central Iberia (P. bocagei, P. guadarramae, P. carbonelli and P. virescens); and iii) the other in SE Iberia and northwest Africa (Valencia lineage, Albacete/Murcia lineage and P. vaucheri) (Figure 3). The cluster of western and central forms and the southern and African clade diverged approximately 8.98-11.71 Ma, according to Kaliontzopoulou et al. (2011). This dating coincides with the formation of the cluster (P. liolepis and Galera lineage) at 9.15-10.09 Ma. In this period, the Betic marine corridor opened (Figure 4) and the fragmentation of the area which gave rise the Betic region took place (8-10 Ma). This region remained as an archipelago not colonisable by land until the end of the Tortonian (7.2 Ma) when the Betic Strait was closed (Duggen et al., 2003).

5

Introduction

5

Introduction

The transformation of the Betic marine corridor into a shallow sea level environment led to the Tortonian Salinity Crisis (TSC) (Krijgsman et al., 2000) which caused the formation of land bridges between the Peninsula and islets in what is now the Betic region. These areas may have been colonized by lizards and become a speciation hotspot (Paulo et al., 2001). The final closing of the Betic Strait was responsible for the Messinian Salinity Crisis (MSC) (5.6-5.3 Ma) causing the drying of the Mediterranean Sea, allowing for the connection between the continents, and enabling the possible colonisation of these lizards to North Africa. The opening of the Strait of Gibraltar at the end of the MSC (5.3 Ma) caused the rapid refilling of the Mediterranean and isolation of North African populations. This scenario would explain the greater similarity between lizards from south Spain and North African forms than between southern Iberian and other regions in the Peninsula (Álvarez et al., 2000; Paulo et al., 2002; Batista et al., 2004, Carranza et al., 2004a; Harris et al., 2004; Veith et al., 2004).

Figure 2. Distribution of main Podarcis mtDNA lineages from the Iberian Peninsula and North Africa. Source:

Caerio-Dias et al. (2018) with modifications.

Podarcis bocagei Podarcis carbonelli

Podarcis guadarramae lusitanicus Podarcis guadarramae guadarramae Podarcis virescens

Podarcis liolepis Galera lineage Valencia lineage Albacete/Murcia lineage Podarcis vaucheri

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Introduction

1.1.1.1. Southeast Iberian Peninsula: Podarcis hispanicus

Lizards that inhabit the SE Iberian Peninsula are the paraphyletic group called Podarcis hispanicus.

Numerous studies have been carried out with the aim of defining taxonomic units and evolutionary relationships inside this group. Pinho et al. (2006) in a phylogenetic analysis of the Podarcis from the Iberian Peninsula and North African described, using a long fragment of mtDNA sequences (2,425 bp), the new form of Galera, represented by a unique sample, from the Baza Depression of SE Spain, as a sister taxon to all other Iberian and North African Podarcis. The clustering between this new lineage and P. liolepis with high support led to the Galera lineage being considered as a relic of the common ancestor distribution (Pinho et al., 2006). Later work using allozyme markers (Pinho et al., 2007) largely corroborated the subdivisions reported for mtDNA. Reciprocal monophylia of Galera could not be evaluated, because although more individuals from Galera lineage were included, these came from a single location. The genetic differentiation measured based on F_ST values between the two forms of P.

hispanicus (Galera and Valencia lineage) and all the other species showed values comparable with those found between recognized species. One of the phylogenetic relationships well supported in this analysis was the separation between Galera lineage and P. vaucheri, with regard to Valencia lineage and P. liolepis.

Pinho et al. (2007) considered these findings contradictory, because each pair was composed of forms that do not share ancestors according to previous mtDNA phylogeny (Pinho et al., 2006). Nuclear genealogies of two nuclear introns (beta-fibint7 and 6-Pgdint7) failed to define species as monophyletic, and the results obtained suggested that there exists gene flow between forms that are sympatric at least in part of their distribution, such as Galera and Valencia lineages (Geniez et al., 2007; Pinho et al., 2008). Even though gene flow events have been found between P. vaucheri and Valencia lineage, these two species still have poorly studied distribution limits, so it is as yet unknown whether they establish contact zones or whether they are completely allopatric. Although gene flow among forms may have occurred, the main cause for species polyphyly is Incomplete Lineage Sorting (ILS), implying that most forms have been isolated since their divergence. Renoult et al. (2009) suggested that three evolutionary lineages could be identified in eastern Iberia using morphological characters and nuclear loci (P. virescens, P. liolepis and P. hispanicus (Galera lineage)), whereas analysis of mtDNA data revealed four lineages (P. virescens, P.

hispanicus (Valencia lineage), P. liolepis and P. hispanicus (Galera lineage)).

The last and currently accepted phylogeny, which includes SE Iberian forms, is the one elaborated by Kaliontzopoulou et al. (2011). In this study, a second individual belonging to Galera lineage was introduced in the phylogenetic tree and a new lineage was discovered in the SE region of Iberia (Albacete/Murcia lineage). Galera and P. liolepis clustered together. Valencia lineage was considered the nominotypical taxon (P. h. sensu stricto) and formed a second cluster together with forms from North Africa and SE region of Iberian Peninsula, including the new lineage from Albacete/Murcia. Western and central Iberia forms grouped in the third cluster (Kaliontzopoulou et al., 2011) (Figure 3).

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Introduction

Figure 3. Current phylogeny of Podarcis lineages from the Iberian Peninsula and North Africa. Source:

Kaliontzopoulou et al. (2011) with modifications.

Figure 4. Paleographic maps showing changes in connections between the Iberian Peninsula and North Africa from the early Tortonian to the late Messinian. Source: Achalhi et al. (2016).

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Introduction

1.1.1.2. Columbretes Islands: Podarcis liolepis

The Columbretes archipelago (named in the past Columbraira or Ophiusa, terms that allude to the large amount of snakes that populated them until the 19th century, when intensive extermination campaigns started) consists of a group of small islets located to the east of the Iberian Peninsula in the Mediterranean Sea with an approximate area of 19 ha (Castilla et al., 2005).

These uninhabited islets are located between Castellón (Comunitat Valenciana) and Ibiza (Balearic Islands), at 51 and 100 km of distance, respectively (Castilla et al., 1998a) (Figure 5). The geological origin of this archipelago is dated between 1-0.3 Ma, which corresponds to the period after Pleistocene volcanic episodes (Aparicio et al., 1991). These islands have not always been isolated from the mainland, because during the last glaciations, in particular the Würm (mid and low Pleistocene), the Mediterranean Sea level dropped approximately 120 m. The channel between the Iberian Peninsula and the Columbretes appears to have a depth of approximately 90-100 m, hence both territories are likely to have been connected (CLIMAP, 1976).

Figure 5. Location of the Columbretes Islands and the principal islets that compose the archipelago.

1

2

3

4

1

Grossa

Columbretes Islands

Mancolibre

Senyoreta Mascarat

2 3

Ferrera Espinosa Bauzá Navarrete

Foradada Lobo

Méndez Núñez 4 Carallot

Cerquero

Churruca Baleato Valdés

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Introduction The archipelago comprises four different groups of islets (Figure 5): 1) Grossa (13 ha), Mascarat, Senyoreta and Mancolibre, 2) Ferrera (1.5 ha), Espinosa, Bauzá, Valdés and Navarrete; 3) Foradada (1.6 ha), Lobo (0.5 ha) and Méndez Núñez; 4) Carallot (0.1 ha), Cerquero, Churruca and Baleato. The archipelago remained uninhabited, except for 1855 to 1975, when lighthouse keepers were present. Some islands (Foradada, Ferrera and Carallot) were used for military exercises that used live ammunition, with effects on the flora and fauna of the islands. Some examples of human impact are the extermination of vipers (Vipera latasti) and dramatic reduction of scorpions (Buthus occitanus), burning of natural vegetation, and the introduction of domestic species such as pigs, rabbits, cats, and goats. The Columbretes archipelago was declared a nature reserve in 1988 and marine reserve in 1990. Thereby, the conservation and preservation of endemic species became the main goal (Castilla & Bauwens, 1991a, 1991b). The extant terrestrial vertebrate fauna consists of some breeding bird species (Falco eleonorae, Larus audouinii orHydrobates pelagicus) and the endemic lizard first named as Podarcis atrata and subsequently considered conspecific with Podarcis liolepis (Harris et al., 2002, Harris & Sá-Sousa, 2002, Pinho et al., 2006, 2007, 2008, Renoult et al., 2010, Kaliontzopoulou et al., 2011). The Columbretes Podarcis ancestor could have arrived from the mainland, during the last glaciation (Würm) about 20,000 years ago. Only in four small islets of the archipelago (Grossa, Mancolibre, Foradada and Lobo) can we find this lizard species, probably because of the limited food resources and the small area of the other islets (Castilla & Bauwens, 1991a, 1991b, 2000).

The conservation status of this endemic species is still not well defined, following its recent taxonomic change, although it was considered vulnerable for the national institutions. Habitat fragmentation and the low number of individuals making up these populations are important aspects that influence the survival of this species, which could lead it to extinction (Castilla, 2002; Castilla et al., 2006).

Figure 6. Morphology of P. liolepis specimens from the Columbretes Islands (left) and the Iberian Peninsula (Peñagolosa) (right). Source: Valentín Pérez-Mellado.

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Introduction

Individuals from the Columbretes islands were firstly considered part of the Podarcis hispanicus complex but were then raised to species rank with the name Podarcis atrata (Castilla et al., 1998b). Currently, the Podarcis from Columbretes is considered conspecific with P. liolepis (Harris & Sá-Sousa, 2002, Renoult et al., 2010, Geniez et al., 2014). Consequently, the status of P. atrata as endemism is considered doubtful.

The morphologic divergence between P. liolepis (Figure 6) from the mainland and from the Columbretes islands is attributable to local adaptation that arose in a very short period (end of the last glacial period) (Castilla & Bauwens, 1997; Harris & Sá-Sousa, 2002; Arntzen & Sá-Sousa, 2007).