Propagule pressure and colony social organization are associated with the successful invasion and rapid range expansion of fire ants in China

Abstract

We characterized patterns of genetic variation in populations of the fire ant Solenopsis invicta in China using mitochondrial DNA sequences and nuclear microsatellite loci to test predictions as to how propagule pressure and subsequent dispersal following establishment jointly shape the invasion success of this ant in this recently invaded area. Fire ants in Wuchuan (Guangdong Province) are genetically differentiated from those found in other large infested areas of China. The immediate source of ants in Wuchuan appears to be somewhere near Texas, which ranks first among the southern USA infested states in the exportation of goods to China. Most colonies from spatially distant, outlying areas in China are genetically similar to one another and appear to share a common source (Wuchuan, Guangdong Province), suggesting that long-distance jump dispersal has been a prevalent means of recent spread of fire ants in China. Furthermore, most colonies at outlier sites are of the polygyne social form (featuring multiple egg-laying queens per nest), reinforcing the important role of this social form in the successful invasion of new areas and subsequent range expansion following invasion. Several analyses consistently revealed characteristic signatures of genetic bottlenecks for S. invicta populations in China. The results of this study highlight the invasive potential of this pest ant, suggest that the magnitude of international trade may serve as a predictor of propagule pressure and indicate that rates and patterns of subsequent range expansion are partly determined by the interplay between species traits and the trade and transportation networks.

Invasion genetics of the Pacific oyster Crassostrea gigas in the British Isles inferred from microsatellite and mitochondrial markers

“…It is generally accepted that introduction events can be accompanied by founder events and that associated loss of genetic diversity may result in inbreeding depression, which could reduce ability of the invasive species to adapt to its new environment. However, there have been several cases of introduced populations with low genetic diversity (genetic bottlenecks) that have been successful (ant Linepithema humile: Tsutsui et al 2000;Yang et al 2012;mosquitofish Gambusia affinis: Purcell et al 2012 (Weir and Cockerham 1984). Below diagonal: D est , bias-corrected differentiation index (Jost 2008 c Bayesian individual clustering of Crassostrea gigas performed in STRUCTURE, using the admixture model with correlated allele frequencies, and using sample group information (Hubisz et al 2009).…”

Invasion history of Solenopsis invicta (Hymenoptera: Formicidae) in Fujian, China based on mitochondrial DNA and its implications in development of a control strategy

“…In Longyan city, H36 was much less common than H5 (23% and 77%, respectively) (Fig. , also see previous research data in China from Yang et al ., ).…”

“…Our results, being consistent with conclusions of recent works that reconstructed invasion pathways of S. invicta (Ascunce et al ., ; Yang et al ., ), showed that S. invicta populations in China most likely originated from the USA but not from its native range. Importantly, the fact that no new haplotypes were detected in China likely suggests that the expanding distribution of S. invicta within China, at least to Fujian Province, mainly resulted from spreads from existing populations.…”

“…LY3 is the only population bearing haplotype H36, suggesting that the source area of this population might be different from others. As Guangdong Province was the first place that S. invicta invaded in mainland China (Zeng et al ., ), and an early investigation, as well as ours, showed that the source of carriage was from Guangdong Province (Chen, ; Zhang, ; Hou et al ., ), the existence of this fire ant both in mountain areas and coastal areas in Fujian indicates human‐aided transport promoted long‐distance movement of S. invicta , and repeated introductions from Guangdong Province amplified the bridgehead effect of S. invicta spreading throughout south‐eastern China (Lombaert et al ., ; Yang et al ., ). Overall, our data indicate that, rather than one spreading to another, populations of S .…”

“…Newly invaded populations only harbored three mitochondrial haplotypes, such as H5, H22 and H36, which are the most common among US populations (Ascunce et al, 2011). In Asia, Taiwan was found to harbor these three haplotypes resulting from at least two separate introductions (Yang et al, 2008), while in mainland China at least two different introductions have also been suggested (Ascunce et al, 2011;Yang et al, 2012). These studies have shown that newly introduced areas of S. invicta harbor only three mitochondrial cytochrome oxidase subunit I (cox I) haplotypes, thus that while the information pointing to the expansion of the invasion is very limited, it is still relevant as a first step to understand the route and manner it invades.…”