title: Population expansions shared among coexisting bacterial lineages are revealed by genetic evidence.
abstract: Comparative population studies can help elucidate the influence of historical events upon current patterns of biodiversity among taxa that coexist in a given geographic area. In particular, comparative assessments derived from population genetics and coalescent theory have been used to investigate population dynamics of bacterial pathogens in order to understand disease epidemics. In contrast, and despite the ecological relevance of non-host associated and naturally occurring bacteria, there is little understanding of the processes determining their diversity. Here we analyzed the patterns of genetic diversity in coexisting populations of three genera of bacteria (Bacillus, Exiguobacterium, and Pseudomonas) that are abundant in the aquatic systems of the Cuatro Cienegas Basin, Mexico. We tested the hypothesis that a common habitat leaves a signature upon the genetic variation present in bacterial populations, independent of phylogenetic relationships. We used multilocus markers to assess genetic diversity and (1) performed comparative phylogenetic analyses, (2) described the genetic structure of bacterial populations, (3) calculated descriptive parameters of genetic diversity, (4) performed neutrality tests, and (5) conducted coalescent-based historical reconstructions. Our results show a trend of synchronic expansions across most populations independent of both lineage and sampling site. Thus, we provide empirical evidence supporting the analysis of coexisting bacterial lineages in natural environments to advance our understanding of bacterial evolution beyond medical or health-related microbes.
authors.affiliation: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México.
authors.forename: Morena
authors.initials: M
authors.lastname: Avitia
authors.affiliation: Departamento de Ecología de la Biodiversidad, Laboratorio Nacional de Ciencias de la Sostenibilidad, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México.
authors.forename: Ana E
authors.initials: AE
authors.lastname: Escalante
authors.affiliation: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México ; Biology Department, James Madison University , Harrisonburg VA , USA.
authors.forename: Eria A
authors.initials: EA
authors.lastname: Rebollar
authors.affiliation: Division of Biology, Imperial College London, Silwood Park Campus , Ascot, Berkshire , UK.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Moreno-Letelier
authors.affiliation: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Eguiarte
authors.affiliation: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México , México DF , México.
authors.forename: Valeria
authors.initials: V
authors.lastname: Souza
keywords: Bacterial population genetics; Coalescence; Cuatro cienegas; Historical demography; MLST