Argiope bruennichi (Puts, 1989)

Wawer, Wioletta & Wytwer, Jolanta, 2020, Abundance changes in orb-weaver spider communities at the edge of the Argiope bruennichi expansion range, Zootaxa 4899 (1), pp. 363-373 : 365-367

Argiope bruennichi in the structure of orb-weaver spider communities

In this study, 1717 spider individuals from 16 species were collected in two regions: the Sandomierz Basin (SAN) in the south and the Mazury Lake District (MAZ) in the north of Poland ( Table 2). The number of species was the same in both regions, but the composition of each community was different. Araneus alsine (Walckenaer, 1802) and Cercidia prominens (Westring, 1851) were present only in the southern SAN, while Cyclosa oculata (Walckenaer, 1802) and Metellina segmentata (Clerck, 1757) were present only in the northern MAZ.

Between 6 and 13 spider species were found per site in SAN, while in MAZ the species number was between 8 and 11 per site. Generally, the number of spiders was higher on sites in MAZ (from 145 to 307 ind./ 150 m 2) than in SAN (from 32 to 139 ind./ 150 m 2). Also, diversity according to the Shannon-Wiener index (H’) reached higher values in MAZ (between 0.84 to 1.86) than in SAN (from 0.76 to 1.63). The same highest value (1.86) of the Shannon-Wiener index (H’) was recorded on two sites, where the level of abundance was lowest in the region. These were an unused agricultural land with Conyza canadensis (site MAZ5), where 11 species were recorded, and an unused pasture (MAZ6) where 9 species were found and where the highest evenness (J’) was noted, too. The lowest value of the Shannon-Wiener index refers to the site with dominant Juncus effusus and Deschampsia caespitosa (SAN4), where the lowest values of H’, J’ and abundance (N) were also noted ( Table 3).

In the SAN and the MAZ, A. bruennichi was not only the most frequent species (occurring on all studied sites), but it was also entirely dominant in all study sites ( Table 2). Its percentage contribution in the spider communities of both regions ranged from almost 40 % to even over 80 % in 10 out of 12 study sites; on the remaining two sites, it was a subdominant with at least 22% contribution. A. quadratus was the subdominant species in at least half of the examined sites. This species occurred with lower frequency than A. bruennichi in SAN (55 %), and with similar frequency as in MAZ (97 %).

According to the ANOSIM test, the communities of orb-weaver spider species differed significantly (P=0.0267, R=0.2926)—although partly overlapped (0.25<R<0.5)—between studied regions. A SIMPER test revealed that A. bruennichi was responsible for almost 40 % of the observed difference in the domination structure and A. quadratus was responsible for less than 26 %. Both species were responsible for the dissimilarity of community structures of 65 % ( Table 4).