From Pavement to Population Genomics: Characterizing a Long-Established Non-native Ant in North America Through Citizen Science and ddRADseq

Abstract

Clarifying the population structure and introduction history of non-native species is essential to preventing and mitigating effects of invasion, yet the invasion history of many long-established non-native species remain poorly understood. This study characterized the population structure of one of the most commonly encountered urban ants in North America using public participant-collected specimens and double-digest restriction-site associated DNA sequencing (ddRADseq). Based on this genomic approach we confirm the identity of populations ranging across the continent as Tetramorium immigrans Santschi, and report low genetic diversity across its range, suggesting that this entire population resulted from the establishment of one single, or a few closely related ant colonies, approximately 200 years ago. The absence of strong population structure suggests that this ant's spread across North America has been repeatedly aided by human-assisted dispersal. We find no evidence of inbreeding in T. immigrans; this contrasts with the inbreeding and unicoloniality of many other invasive ants. These results demonstrate how collections-based public participatory science and emerging highthroughput sequencing techniques each have the potential to vastly improve the amount of data available to researchers. Together, these techniques can be deployed to address ecological and evolutionary questions, including questions about invasion biology, in nonmodel organisms. We suggest that this model is particularly well-suited for research on common taxa that are ecologically important but poorly understood.

Effect of social structure and introduction history on genetic diversity and differentiation

“…Both the number of introduction events and the number of introduced queens influence the amount and geographical distribution of genetic diversity in the invasive range. One or few introduction events have been proposed for T. immigrans due to weak genetic structuring and also for T. tsushimae because of reduced dispersal in the invasive range (Table S1; Reuther, 2009;Zhang et al, 2019). In T. immigrans, we found three mitochondrial haplotypes and two structure clusters in North America and a different haplotype and cluster in Argentina (Figures 1 and 7a).…”

Divide and conquer: Multicolonial structure, nestmate recognition, and antagonistic behaviors in dense populations of the invasive ant Brachymyrmex patagonicus

“…Interestingly, a growing number of ant species are reported as successful invaders despite exhibiting large supercolonies . This includes other multicolonial species, such as S. invicta (Kjeldgaard et al, 2020) or Tetramoriun immigrans (Zhang et al, 2019). It also includes species where invasive colonies are large and made of several interconnected nests, but their size does not exceed 1 km in length, such as Myrmica rubra (Chen et al, 2018), Brachyponera chinensis (Eyer, Matsuura, et al, 2018), and Technomyrmex albipes (Yamauchi et al, 1991).…”

Public Engagement Provides First Insights on Po Plain Ant Communities and Reveals the Ubiquity of the Cryptic Species Tetramorium immigrans (Hymenoptera, Formicidae)

“…However, it is now considered a cryptic complex of 10 different taxa in the region whose distribution data are often scarce [ 53 , 54 , 80 ]. Among the species of this complex, only T. immigrans is known to possess a notable invasive potential, as it has colonized large areas of North America, gaining since the 19th century the nickname of “pavement” ant due to its extreme success in urban environment (e.g., [ 81 , 82 , 83 , 84 ]). Tetramorium immigrans is certainly native in the Anatolia and Caucasus regions, where it shows a comparatively high haplotype diversity and inhabits natural mountain habitats [ 53 , 85 ].…”

“…It is remarkable that about 80% of the sampling sites reported by Wagner and colleagues [ 53 ] was in natural or seminatural environments and T. immigrans was never collected there. To better understand the status of T. immigrans in Italy and Europe, more detailed phylogeographic data (see also [ 84 ]) and even greater sampling efforts in natural habitats could be meaningful. However, there is currently no evidence suggesting to consider T. immigrans as native to the Po Plain or other Italian regions.…”