Skip to main content
Dryad logo

Spiders sampled during student excursions at Bankfontein farm

Citation

Haddad, Charles (2021), Spiders sampled during student excursions at Bankfontein farm, Dryad, Dataset, https://doi.org/10.5061/dryad.v15dv41w1

Abstract

As part of an undergraduate Entomology module, field excursions were undertaken to a mixed livestock farm in central South Africa, during March-April 2015, 2016 and 2018–2020. The aim was for groups to determine and compare terrestrial arthropod biodiversity in three strata of three contrasting biotopes, with particular emphasis on insects. To determine the contributions such excursions make to documenting biodiversity of a non-target taxon, the spider (Arachnida: Araneae) data generated by students was compared with the local species richness (LSR) for the area. The LSR for the farm Bankfontein included a total of 242 species, representing 40 families. Over the five years, student groups sampled a total of 158 spider species, representing 65.3 % of the LSR. The number of species sampled per year ranged between 57 and 94 for undergraduate students (1–3 groups), and was 119 species for the final year of the study carried out by the author and two post-graduate students (2 groups), which could be attributed to collector experience and modification of the sorting process for beat sampling, particularly. This study emphasises the importance of utilizing students as a valuable resource to generate biodiversity data, particularly where financial and human resources may be limited.

Methods

Each student group was required to implement a standardised sampling protocol in each of the three biotopes. Considering the paucity and low growth of grasses in the Nama Karoo veld, no sweep-net sampling was undertaken. This contrasts with the regular practical assignments, which rely exclusively on sweep-net sampling. Three methods were employed in each biotope by each group to sample arthropods:

1) 10 pitfall traps (6 cm diameter 250 ml bottles) were set out 5 m apart in a line transect. Ethanediol (50 ml) was added to each pitfall trap as a preservative, with traps kept open for 4 days (96 hours) before being removed. Where multiple student groups sampled in a single year, trapping transects were separated by at least 10 m to minimise interference. Arthropods were sorted from the collected material in white plastic trays and preserved in 70 % ethanol in separate vials for each sample;

2) 10 leaf litter samples were taken by filling 5 l plastic freezer bags with litter from beneath woody plants. The collected material was sifted over a large white sheet using a round steel sieve with a diameter of 45 cm, height of 10 cm and mesh spacing of 8 mm. Specimens sampled by litter sifting were collected with forceps or clean glass vials and put into separate vials containing 70 % ethanol for each sample. For this method, either the author or one senior post-graduate student assisted each student group with collecting specimens from the sheet; and  

3) 10 beating samples were taken by striking the branches of woody foliage 50 times over a standard sweep-net with a diameter of 40 cm. Each of the 50 beat units comprised striking a single branch at the same point three times before moving onto the next unit. Once 50 units had been completed, the sampled material was transferred to a 5 l plastic freezer bag until sorting in the laboratory. Beat samples were euthanised using toilet paper doused in ethyl acetate, which was added to each bag on return to the field laboratory. This was to ensure that flying insects could not escape during sorting. The material was then emptied into large white plastic trays, and the arthropods removed using forceps and transferred to vials containing 70 % ethanol.

The number of samples per habitat and method was determined by the number of student groups on each trip: 30 (2015), 20 (2016), 10 (2018), 30 (2019) and 20 (2020). In all of the years, students were responsible for all sampling and processing of material, except for 2020, when the University of the Free State closed in the week prior to the proposed excursion due to the COVID-19 pandemic. The author and two post-graduate students (one Ph.D and one M.Sc level) consequently undertook the sampling before national government imposed a national lockdown on 27 March 2020, and executed collecting for the two student groups that would have undertaken the excursion.

Usage Notes

This dataset is a summary of five years' sampling using three methods (beating B, litter sifting L and pitfall trapping P) in three biotopes (Nama Karoo veld N, riparian woodland R and hillside grassland H) in central South Africa. The raw data can be requested from Charles Haddad (haddadcr@ufs.ac.za).

Funding

University of the Free State

University of the Free State