Abstract
Aim Tapinoma melanocephalum is listed as one of the most important invasive pest species in China. Information regarding the patterns of invasion and effects of geographic isolation on the population genetics of this species is largely lacking.LocationSouth China.MethodsTo address this problem, we genotyped 39 colonies (two colonies were collapsed due to genetic similarity) using microsatellite markers and mitochondrial DNA sequencing to compare colony genetic structure of T. melanocephalum on the mainland and islands of South China.ResultsAn analysis of the colony genotypes showed that the genetic diversity of the mainland population was slightly higher than that of the island populations but not significantly so. However, the observed heterozygosity on Shangchuan Island (SCD) was significantly lower than that of the other colonies. We also found six haplotypes in 111 mitochondrial DNA COI sequences. The relatedness (r) value between colonies of SCD was 0.410, higher than that of the other populations. The genetic clusters among colonies were not related to geographic locations and exhibited admixture likely due to frequent human‐mediated dispersal associated with trade between the mainland population and the islands. Pairwise F STs between populations showed differentiation among mainland populations, while SCD displayed high levels of divergence (FST > 0.15) from most mainland populations. There was no significant isolation by distance among colonies. Most populations showed signs of a bottleneck effect.Main conclusionsOur study suggests that there was no significant difference in the genetic diversity among the islands and the mainland; however, the lower genetic diversity, the higher degree of genetic divergence from other colonies, and the higher relatedness among nestmates made the SCD population stand out from all the others.
Highlights
Biological invasions are considered a threat to global biodiversity, and invasive ants are among the most successful invaders (Ross &Keller, 1995)
T. melanocephalum is a household-infesting ant (Nickerson, Bloomcamp, & Fasulo, 2004), and an agriculture pest associated with hemipteran species, such as mealybugs and scales (Fowler, Bernardi, Delabie, Forti, & Pereira-da-Silva, 1990; Venkataramaiah & Rehman, 1989)
It was first known to invade China in ca. 1929. It is frequently found in disturbed habitats where it nests in old branches, dry grass clumps, moist grass, and plant stems
Summary
Biological invasions are considered a threat to global biodiversity, and invasive ants are among the most successful invaders It is likely to be found in rotten wood, soil, and decayed parts of trees or beneath bark as well as in the walls of houses and in plant pots It has successfully spread through several provinces in South China and some areas of North China through human assistance (Wetterer, 2009). Lower genetic variability may result in a change in the nestmate recognition system, leading to decreased aggression (Bourke & Franks, 1995; Tsutsui et al, 2000; Vásquez & Silverman, 2008) Another mechanism for unicolonial formation has been proposed for Linepithema humile by “genetic cleansing.”. We explore the genetic and environmental (geographic isolation) factors in introduced areas to determine and compare the population genetic structure and colony characteristics of T. melanocephalum between island and mainland regions using six microsatellite loci and COI sequence data, and examine the relationship between two levels of population structure. The aim of this study is to characterize the breeding structure of the colonies and to investigate the relationships among populations and the mechanism of population spread
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