Phylogeography of a mountain lizard species: an ancient fragmentation process mediated by riverine barriers in the Liolaemus monticola complex (Sauria: Liolaemidae)

Abstract

Liolaemus monticola is a mountain lizard species, with a widespread distribution from central Chile that displays several highly polymorphic chromosomal races. Our study determined the phylogeographic structuring and relationships among three chromosomal races of L. monticola in Chile. Mitochondrial DNA (mtDNA) sequences of the cytochrome b gene were examined using the following phylogenetic methods: maximum parsimony, maximum likelihood, Bayesian inference and nested clade phylogeographic analyses (NCPAs). These methods revealed two major monophyletic clades (north and south) in the L. monticola species, with non-overlapping geographical locations separated by the Maipo and Yeso rivers (except one hybrid, from a zone of secondary contact). The NCPA showed that a past fragmentation process likely resulted in the separation of the two clades. The southern clade includes all samples of the ÔSouthern, 2n ¼ 34Õ race; the northern clade is comprised of all remaining derived chromosomal races: the ÔNorthern, 2n ¼ 38-40 and the Multiple Fission, 2n ¼ 42-44Õ races. Our results support the hypothesis of a geographical and genetic split resulting from allopatric processes caused by riparian barriers acting over a long time period. The inferred biogeographical scenario shows that populations have moved from the south to the north using the Andean mountains as the primary corridor for dispersal.

Molecular phylogenetic analyses reveal the importance of taxon sampling in cryptic diversity: Liolaemus nigroviridis and L. monticola (Liolaeminae) as focal species

“…The focal species L. monticola was recovered within an unsupported clade together with L. nitidus. However, all sequences from the northern distribution of L. monticola (northern race, see [38] Table S1 EU22083) was placed closer to all L. monticola from the northern race (Fig. 2).…”

“…Strikingly, the eight haplotypes of L. nitidus from the locality of Cantillana were placed in two divergent clades: six haplotypes (haplotypes 35,38,41,42,43,44; Fig. 4) were closer to the clade that included the L. monticola northern race, and two other haplotypes (Haplotypes 36, 37; Fig.…”

“…2 and 4). Haplotypes of L. monticola were placed in two divergent clades (northern and southern races; [37,38], with several haplotypes of L. nitidus within L. monticola clades. Eight haplotypes of L. nitidus were sister (and supported; clade B1) to a clade that included all L. monticola haplotypes that belong to the northern race plus one (supported) additional L. nitidus haplotype (H96; Fig.…”

“…A fragment of 775bp of the mtDNA region encoding the cyt-b gene was amplified via polymerase chain reaction (PCR) using the light strand primer GLUDG (5′-TGACTTGAARAACCAYCGTTG-3′) and the heavy strand primer CB3 (5′ GGCAAATAGGAARTATC ATTC-3′) previously used [40]. The thermocycling conditions were previously documented [27]; amplification reactions were carried out in 11.5 μl reaction mixture containing 1.5μl template DNA (1-50 ng), 2μl 5X Taq buffer, 1.2 μl 25 mM MgCl 2 , 0.2 μl dNTPs (10 mM), [38] 0.124 μl each primer (10 mM) and 0.1 μl Taq polymerase (5 U/μl Promega Corp.). Double-stranded PCRamplified products were checked by electrophoresis on a 1% agarose gel in 1x Tris-Borate-EDTA (TBE) TBE running buffer and stained with Gel Red (Biotum, Inc., Hayward CA, USA).…”

“…A previous study reported at least four major lineages allowing to infer strong phylogeographic structure within L. nigroviridis [27]; therefore, an increase taxon sampling seems recommendable to determine the position of the new proposed taxon (L. uniformis) related to its sister species (L. nigroviridis). The second model, L. monticola, is a saxicolous lizard species from the mediterranean Andes [32,33] and the Coast Range [34] in central Chile from between 600 m to 1900 m. This species displays an extensive variation and complexity in chromosome number in a latitudinal gradient [35,36], with riverine barriers playing a major role in the divergence of populations [37,38]. Phylogenetic inferences show that L. nitidus is sister to L. monticola [3,39].…”