No abstract

Invasive populations are often associated with low levels of genetic diversity owing to population bottlenecks at the initial stages of invasion. Despite this, the ability of invasive species to adapt rapidly in response to novel environments is well documented. Epigenetic mechanisms have recently been proposed to facilitate the success of invasive species by compensating for reduced levels of genetic variation. Here, we use methylation sensitive-amplification fragment length polymorphism and microsatellite analyses to compare levels of epigenetic and genetic diversity and differentiation across 15 sites in the introduced Australian house sparrow population. We find patterns of epigenetic and genetic differentiation that are consistent with historical descriptions of three distinct, introductions events. However unlike genetic differentiation, epigenetic differentiation was higher among sample sites than among invasion clusters, suggesting that patterns of epigenetic variation are more strongly influenced by local environmental stimuli or sequential founder events than the initial diversity in the introduction population. Interestingly, we fail to detect correlations between pairwise site comparisons of epigenetic and genetic differentiation, suggesting that some of the observed epigenetic variation has arisen independently of genetic variation. We also fail to detect the potentially compensatory relationship between epigenetic and genetic diversity that has been detected in a more recent house sparrow invasion in Africa. We discuss the potential for this relationship to be obscured by recovered genetic diversity in more established populations, and highlight the importance of incorporating introduction history into population-wide epigenetic analyses.

This study used microsatellite loci to provide evidence of isolation by distance and an effect of artificial impoundments on the genetic diversity of Channel Catfish Ictalurus punctatus from the Wabash and Ohio rivers. The Wabash River is the longest free‐flowing river east of the Mississippi River in the USA, and the Ohio River is highly impounded, yet both rivers support large Channel Catfish fisheries. There was a significant positive relationship between genetic differentiation and geographic distance indicating isolation by distance. Clustering with the programs, STRUCTURE and GENELAND, and principal component analysis revealed multiple genetic clusters, and several sites had results consistent with adults existing as mixtures of genetic groups. These results suggest that the rate of straying among reproductive sites or dispersal is dependent on geographic distance. Channel Catfish from the unimpounded Wabash River had higher genetic diversity (Ho and He) than that from the impounded Ohio River. The impoundments had discordant effects on genetic structure; two site comparisons across a dam were differentiated more strongly than would be expected by geographic distance, whereas genetic differentiation was not detected in another comparison across a dam. Thus, the effect of artificial impoundments on Channel Catfish biology may be affected by river or site‐specific characteristics, and the presence of genetic differentiation may be minimized by large population sizes.

Wildfires are highly variable and can disturb habitats, leading to direct and indirect effects on the genetic characteristics of local populations. Florida scrub is a fire-dependent, highly fragmented, and severely threatened habitat. Understanding the effect of fire on genetic characteristics of the species that use this habitat is critically important. We investigated one such lizard, the Six-lined Racerunner (Aspidoscelis sexlineata), which has a strong preference for open areas. We collected Six-lined Racerunners (n = 154) from 11 sites in Highlands County, FL, and defined 2 time-since-last-fire (TSF) categories: recently burned and long unburned. We screened genetic variation at 6 microsatellites to estimate genetic differentiation and compare genetic diversity among sites to determine the relationship with TSF. A clear pattern exists between genetic diversity and TSF in the absence of strong genetic differentiation. Genetic diversity was greater and inbreeding was lower in sites with more recent TSF, and genetic characteristics had significantly larger variance in long unburned sites compared with more recently burned sites. Our results suggest that fire suppression increases variance in genetic characteristics of the Six-lined Racerunner. More generally, fire may benefit genetic characteristics of some species that use fire-dependent habitats and management efforts for such severely fragmented habitat will be challenged by the presence of multiple species with incompatible fire preferences.