Influence of hydrogeographic history and hybridization on the distribution of genetic variation in the pupfishesCyprinodon atrorusandC. bifasciatus

Abstract

The evolutionary importance of hybridization in animals has been subject of much debate. In this study, we examined the influence of hydrogeographic history and hybridization on the present distribution of nuclear and mitochondrial DNA variation in two pupfish species, Cyprinodon atrorus and Cyprinodon bifasciatus. Results presented here indicate that there has been limited introgression of nuclear genes; however, mtDNA introgression has been substantial, with complete replacement of the C. bifasciatus mitochondrial genome by that of C. atrorus. Subsequent to this replacement, there has been diversification of mitochondrial haplotypes along major geographic regions in the basin. Evidence was also found that mitochondrial replacement follows a predictable, cyclical pattern in this system, with isolation and diversification followed by re-contact and replacement of C. bifasciatus mitochondrial haplotypes by those of C. atrorus. This pattern is best explained by a combination of a numeric bias towards C. atrorus and mating site selection rather than selection for C. atrorus mitochondrial genome. These results demonstrate the important role hybridization can play in evolution.

Evolutionary history and population genetics of a cyprinid fish (Iberochondrostoma olisiponensis) endangered by introgression from a more abundant relative

“…Any demographic or preference differences between the hybridizing groups could result in a complete replacement of the mitochondrial genome in the ancient C. olisiponensis (Chan and Levin 2005). Such patterns of mitochondrial replacement have been detected in other taxa, including fish (Carson and Dowling 2006;Good et al 2008;Barbanera et al 2009;Nevado et al 2009;Tang et al 2012). The nuclear loci examined here indicate that different genomic regions share different common ancestors, as would be expected from a species of hybrid origin (Mallet 2005).…”

Antagonism influences assembly of a Bacillus guild in a local community and is depicted as a food-chain network

“…The Churince system consists of three main zones connected by small water causeways, including a spring, an intermediate lagoon and a desiccation lagoon (Johannesson et al, 2004;Carson and Dowling, 2005). Sampling was done only in the intermediate lagoon, which experiences seasonal flooding with minimal flow.…”

The Cuatro Ciénegas Basin in Coahuila, Mexico: An Astrobiological Precambrian Park

“…Rather than islands of land surrounded by water, the CCB is an oasis where islands of water are surrounded by desert, all contained in a mountain-ringed basin. These biogeographic barriers have likely been the driver for speciation and diversification of the over 70 endemic species, including diatoms (Winsborough et al, 2009), snails ( Johnson, 2005, fish (Carson and Dowling, 2006;Tobler and Carson, 2010), and more recently bacteria (Escalante et al, 2009;Cerritos et al, 2011). It is intriguing to postulate that endemism is present in the microbiota of the CCB, but an isolate of Bacillus, B. coahuilensis, appears to have adaptive elements unique to the CCB in its genome .…”

“…Heterogeneity can be understood not only at spatial scales but also at temporal scales by the imposition of dramatic seasonal changes that exert strong selective pressures on microbial populations. Heterogeneous patterns among drainage systems within the area are seasonal (Carson and Dowling, 2006), and diurnal fluctuations may maintain high overall levels of diversity. We conducted one study focused on the role of seasonal fluctuations in the diversity of Pseudomonas populations.…”