Abstract
Grasslands in southern South America are extensive ecosystems which harbor a unique biodiversity; however, studies on the evolution of their taxa are scarce. Here we studied the phylogeography and population history of the Correndera Pipit (Anthus correndera), a grassland specialist bird with a large breeding distribution in southern South America, with the goals of investigating its phylogeographic history and relate it to the historical development of South American grasslands. The mitochondrial NADH dehydrogenase subunit II gene (ND2) was sequenced in 66 individuals from 19 localities and the intron 9 of the sex-linked gene for aconitase (ACOI9) was sequenced from a subset of those individuals, including all five subspecies of A. correndera, as well as the closely related A. antarcticus. Phylogenetic analysis revealed two distinct lineages within the complex: the first (A) corresponding to Andean subspecies A. c. calcaratus and A. c. catamarcae and the second (B) including birds traditionally assigned to A. c. correndera, A. c. chilensis, A. c. grayi and some individuals of A. c. catamarcae. A. antarcticus is nested within this second lineage. These results were also supported by evidence of niche divergence for variables associated with precipitation. The oldest split between clade A and B was estimated at c. 0.37 Mya, during the middle Pleistocene. Species distribution models for the present and the Last Glacial Maximum (LGM) suggest that grassland areas in southern South America remained relatively stable, in contrast to the general view of a reduction in grassland cover in South America since the LGM. Recent divergences and low phylogeographic structure (for lowland vs. highland geographic groups, intra-population genetic variance was greater than inter-groups; e.g., for ACOI9: 95.47% and ND2: 51.51% respectively), suggest widespread gene flow between lowland populations.
Highlights
Geological processes and past climatic changes have been determining factors in generating complex patterns of genetic diversity (Hewitt, 1996)
Considering the complex history and geography of the habitat of A. correndera in southern South America and the uncharacterized evolutionary relationships within the species, the aim of this study is to evaluate the phylogeographic structure of A. correndera across most of its distributional range in order to test the following hypothesis predictions: (i) The degree of phylogeographic differentiation across the distribution of the species is not related to current morphology-based subspecific designations; (ii) the genetic structure is associated with environmental differences as represented by climatic variables; and (iii) the demographic history of lineages is related to the development of different types of grasslands across the South American landscape
Clade A included individuals that belong to the Andean Altiplano or Highlands subspecies A. c. calcaratus and A. c. catamarcae (Fig. 2), with a lack of internal structure in relation to subspecies monophyly
Summary
Geological processes and past climatic changes have been determining factors in generating complex patterns of genetic diversity (Hewitt, 1996). In Patagonia a series of refugia have been described in glacial valleys, lowlands, and periglacial zones (e.g., Sérsic et al, 2011; Breitman et al, 2012; Cosacov et al, 2013) These areas maintained high levels of genetic diversity and worked as reservoirs for post-glacial colonization (Sérsic et al, 2011; Birks, 2015). Our knowledge of the historical processes driving diversity patterns in southern South America has increased in recent decades, mostly based on phylogeographic studies of organisms associated with temperate forest (Beheregaray, 2008; Sérsic et al, 2011). This has limited our understanding about the role of other important ecosystems, like grasslands, in generating biodiversity patterns and processes. Studying grassland specialist species will increase our understanding of the processes acting across different environments and their relative importance in causing regional patterns of biodiversity
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