Population structure of the expansive wasp spider (Argiope bruennichi) at the edge of its range

Abstract

Abstract. The wasp spider Argiope bruennichi (Scopoli, 1772) is of Mediterranean-Pontian origin, but for decades it has been expanding northwards, including into the territory of Poland. Based on well-documented expansion records, we can distinguish ''old'' (south-eastern and south-western) and ''new'' populations (north-eastern), respectively, from the 1930s to the 2000s. In Poland, some populations of A. bruennichi were expected to be more genetically isolated from others, due to distance effects or differential times of arrival. We evaluated whether the oldest populations were in a state of HardyWeinberg equilibrium (HWE), and whether recently founded populations were in an expansion phase. Specimens of A. bruennichi (n ¼ 184) were collected at six localities in Poland and single sampling sites in Italy and Japan. Nine microsatellite loci were amplified although only five were useful in the final analyses. Based on the genotypes obtained, we estimated basic measures of genetic diversity and tested for deviation from HWE. The results showed a low level of polymorphism amongst the investigated markers, and accordingly, we found a low genetic diversity in populations. Only populations from Italy and Japan, and one population from Poland, were in HWE. The level of genetic differentiation among sampling sites from Poland was also very low. The high dispersal ability of the wasp spider appears to have facilitated high gene flow among populations. The peripheral and recently settled populations were characterized by the highest heterozygosity and the lowest inbreeding coefficient (F IS ) . The remaining Polish populations are therefore still in the expansion phase, as indicated by deviations from HWE.

Rapid ecological and evolutionary divergence during a poleward range expansion

“…We will henceforth refer to the number of days between collection and oviposition as "oviposition latency." In the field, A. bruennichi females lay their eggs into round flask-shaped egg sacs, placed ~20 cm above the ground, in the grass (Wawer et al, 2017;MM Sheffer, personal observation). Females do not guard or tend their egg sacs for extended periods of time, and a single female can produce multiple egg sacs; we refer to the eggs in each egg sac as a "clutch."…”

“…Argiope bruennichi is an orb-weaving spider species with a Palearctic distribution, which has undergone a rapid latitudinal range expansion within Europe in the last century (Follner & Klarenberg, 1995;Algo, 2010;Krehenwinkel & Tautz, 2013;Krehenwinkel, Rödder & Tautz, 2015;Wawer et al, 2017). Krehenwinkel & Tautz (2013) attributed the range expansion to climate-mediated adaptive introgression, with individuals from eastern Asia mixing with the European gene pool via Russia, providing genetic variation that enabled rapid adaptation to the colder, previously unsuitable conditions in northern Europe.…”

Morphological and molecular evidence supports <I>Argiope chloreis</I> Thorell 1877 and <I>A. chloreides</I> Chrysanthus 1961 (Araneidae: Argiopinae) as distinct species

“…It would be worthwhile to investigate the genetic patterns of Argiope spp. with relatively extensive distributions, e.g., A. bruennichi (Wawer et al 2017), A. lobata (Lindecke & Wall 2016), A. trifasciata (Levi 1983;, and their influence on taxonomic inference. The paraphyly of Argiope with respect to Gea and Neogea nocticolor was also evident as reported by Tan et al (2016).…”

Identification of sex chromosomes using genomic and cytogenetic methods in a range-expanding spider,Argiope bruennichi(Araneae: Araneidae)

“…With this chromosome-level genome, we can employ the coverage depth approach to identify sex chromosome sequences in this species. A. bruennichi is a sexually dimorphic species with a Palearctic distribution, which has rapidly expanded its range in Europe over the course of the last century (Krehenwinkel & Tautz, 2013;Krehenwinkel, Rödder, & Tautz, 2015;Wawer et al, 2017). Sex differences in early life stages of these spiders are particularly interesting since juveniles perform aerial dispersal with silk (ballooning), a behavior which is restricted to the first few instars (Krüger, 2014) and might be sex biased (Krehenwinkel et al, 2016).…”