Commercial pistachio orchards in the Northern Cape Province, South Africa, maintain a lower abundance and diversity of epigeic spiders than undisturbed Nama Karoo grassland (Arachnida: Araneae)

摘要

Epigeic spider (Araneae) populations were studied in three commercial pistachio orchards ( REM, GVN 1, GVN 19) and in a natural undisturbed Nama Karoo grassland site in the Prieska district of the Northern Cape Province, South Africa. A total of 2814 spiders was collected, representing 25 families and 80 species. The grassland site supported a significantly greater abundance and diversity of spiders (n = 1112, 56 spp.) than the three pistachio orchards, viz. REM ( n = 704, 35 spp.), GVN 1 ( n = 560, 26 spp.) and GVN 19 ( n = 428, 25 spp.). Five families (Agelenidae, Ammoxenidae, Cyrtaucheniidae, Gnaphosidae and Philodromidae) dominated the epigeic fauna of the grassland, whereas the orchard stands were dominated by Linyphiidae, Lycosidae and Salticidae. Overall, species composition was more even in the grassland than in the orchards. These results indicate that establishment of the pistachio orchards and subsequent management disturbances had a negative impact on the abundance and diversity of epigeic spider communities. Interestingly, the epigeic spider fauna of the orchards was quite similar to that in central and northern Europe, but the fauna of the grassland differed completely from that in undisturbed European habitats.