Chapter 3: Arthropod diversity, seasonality and ecology of Starlight Cave, western
3.2 M ETHODS
3.3.2 R ESULTS - S PECIES RICHNESS AND ABUNDANCE
A three-dimensional NMS ordination described 83.9% of the variance among the environmental variables (pH, guano deposition and moisture content) for Starlight Cave from all sample periods (Figure 3.9). Axis 1 describes 23.7%, Axis 2 describes 39.8% and Axis 3 describes 20.4% of the variation, demonstrating the most important factor controlling the guano micro- habitat is season. The division between summer and winter can be clearly seen in all three aspects of the ordination with the remaining variation being divided by the position of guano piles within the cave. The ordination shows no division of samples according to Top or Bottom of guano piles indicating that the position within the cave and the season during which sampling occurred are the most influential factors in this system. The two significant environmental variables, pH and moisture content, are both associated with summer, and increase toward the birthing chamber where the largest individual guano pile is located.
Table 3.1. Arthropod and nematode species recorded from of Starlight Cave, Warrnambool, western Victoria. Forty-three arthropod and nematode species from 39 families and 14 orders were recorded from this and previous studies. * Unpublished data from Hamilton-Smith recorded in Moulds (2004).
Class and Order
Family Genus and species
Previous Study Present study
Nematoda ?Rhabditida sp. yes
Crustacea: Isopoda Porcellionidae Porcellio sp. yes
Oniscoidea sp. Hamilton-Smith
unpublished data
no
Arachnida: Araneae Thomisidae Sidymella sp. yes
Acarina Ixodidae Ixodes simplex simplex yes
Macrochelidae Macrocheles penicilliger yes
Laelapidae sp. yes
Parasitidae sp. yes
Spinturnicidae Spinturnix loricata yes
Urodinychidae Uroobovella coprophila yes
Pseudoscorpionida Cheliferidae Protochelifer australis yes
Collembola Entomobryidae Discocyrtus cinctus yes
Hypogastruridae Hypogastrura vernalis yes
Insecta: Orthoptera Rhaphidophoridae sp. yes
Psocoptera sp. yes
Hemiptera Lygaeoidea sp. yes
Thysanoptera Thripidae Thrips imaginis yes
Coleoptera Anobiidae Ptinus exulans Hamilton-Smith 1967 yes
Carabidae Mecyclothorax ambiguus H-S unpublished data* no
Speotarus princeps yes
Cryptophagidae Atomaria sp. Hamilton-Smith 1967 yes
Dermestidae sp. H-S unpublished data* no
Histeridae Saprinus sp. H-S unpublished data* no
Tomogenius ?ripicola yes
Jacobsoniidae Derolathrus sp. Hamilton-Smith 1967 yes Leiodidae Pseudonemadus sp. Hamilton-Smith 1967 yes Silphidae Ptomaphila lachrymosa H-S unpublished data* no Staphylinidae Myotyphlus jansoni Hamilton-Smith and
Adams 1966
yes
Philonthus parcus yes
Diptera Fannidae Fannia sp. H-S unpublished data* no
Nycteribiidae sp. yes
Phoridae sp. yes
Psychodidae sp. yes
Sciaridae sp. yes
Sphaeroceridae Leptocera sp. H-S unpublished data* no
Limosininae sp. yes
Tipulidae sp. yes
Lepidoptera Tineidae Monopis crocicapitella yes
Hymenoptera Braconidae Apanteles ?carpatus yes
Ceraphronidae sp. yes
Diapriidae sp. yes
Formicidae Amblyopone australis H-S unpublished data* no
Ichneumonidae Cryptinae sp. yes
The species richness in Starlight Cave was higher during the second year’s sampling than during the first, and greater at the Tops of guano piles compared with the Bottoms during the second year (Figure 3.11). Species richness at the bottom of guano piles remained almost constant at approximately six species per sample. The Birthing Chamber had the highest average species richness, compared with both the Central Corridor and Terminal Chamber (Figure 3.12). Species richness shows a positive correlation with moisture content and pH, although the fit (r2 = 0.11 and 0.25 respectively) is poor (Figure 3.13 and 3.14).
Table 3.2. Arthropod abundance and percent composition in Starlight Cave. 1Abundances for the two species of Staphylinidae, Myotyphlus jasoni and Philonthus parcus, and the Collembola, Discocyrtus cinctus and Hypogastrura vernalis were grouped as the species were not identified until after the study was complete.
Taxa Total Abundance % of Total Abundance
Ptinus exulans (Anobiidae) 12 271 84.4%
Tomogenius ?ripicola (Histeridae) 783 5.4%
Laelapidae sp. 350 2.4%
Phoridae sp. 338 2.3%
Monopis crocicapitella (Tineidae) 198 1.4%
Nycteribiidae sp. 123 0.9%
Atomaria sp. (Cryptophagidae) 86 0.6%
Cryptinae sp. (Ichnuemonidae) 68 0.5%
Protochelifer australis (Pseudoscorpionida) 64 0.4%
Staphylinidae spp.1 64 0.4%
Sciaridae sp. 52 0.4%
Limosininae sp. (Sphaeroceridae) 46 0.3%
Uroobovella coprophila (Urodinychidae) 31 0.2%
Macrocheles pencilliger (Macrochelidae) 18 0.1%
Collembola spp.1 17 <0.1%
Spinturnix loricata (Spinturnicidae) 10 <0.1%
Derolathrus sp. (Jacobsoniidae) 8 <0.1%
Lygaeoidea sp. 5 <0.1%
Sidymella sp. (Tnomisidae) 3 <0.1%
Curculionidae sp. 2 <0.1%
Speotarus princeps (Carabidae) 2 <0.1%
Porcellio sp. (Porcellionidae) 1 <0.1%
Pseudonemadus sp. (Leiodidae) 1 <0.1%
Rhaphidophoridae sp. 1 <0.1%
Total Abundance 14542 100%
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Figure 3.10. Rank abundance graph of 24 taxa collected from Starlight Cave presented as a two binding hyperbola fitted to the data. Taxa in ascending order are Ptinus exulans (Anobiidae), Tomogenius ?ripicola (Histeridae), Laelapidae sp., Phoridae sp., Monopis crocicapitella (Tineidae), Nycteribiidae sp., Atomaria sp. (Cryptophagidae), Cryptinae sp.
(Ichneumonidae), Staphylinidae spp., Protochelifer australis (Pseudoscorpionida), Sciaridae sp., Sphaeroceridae sp., Uroobovella coprophila (Urodinychidae), Macrocheles penicilliger (Macrochelidae), Collembola spp., Spinturnix loricata (Spinturnicidae), Derolathrus sp.
(Jacobsoniidae), Lygaeoidea sp., Sidymella sp. (Thomisidae), Speotarus princeps (Carabidae), Curculionidae sp., Porcellio (Porcellionidae), Pseudonemadus sp. (Leiodidae) and Rhaphidophoridae sp.. Abundances were log10 transformed prior to analysis.
Simpson’s diversity index values show the most diverse arthropod assemblages are associated with micro-habitats with higher pH (Figure 3.15).
Quantile regression of the upper 25th quantile showed a significant (p <0.0001) positive linear relationship between pH and Simpson’s diversity index (r2 = 0.90). The relationship remains significant (p <0.0001) when using the upper 50th quantile (r2 = 0.62). Moisture content and amount of fresh guano show no significant relationship between with Simpson’s diversity index (Figures 3.16 &
3.17).
Figure 3.11. Average species richness from Tops and Bottoms of guano piles from 4 sample periods in Starlight Cave. Error bars are standard errors.
Figure 3.12. Average species richness for three areas of Starlight Cave, for Tops and Bottoms of all sample periods combined. Error bars are standard errors.
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Figure 3.13. Moisture content of in situ guano plotted against species richness from 40 pitfall traps and four sample periods in Starlight Cave. The data show a significant correlation (p<0.05) although r2 values for linear regression is 0.11.
Figure 3.14. pH plotted against species richness from 40 pitfall traps and four sample periods in Starlight Cave. The data show a significant correlation (p<0.001) although r2 values for linear regression is 0.25.
Figure 3.15. pH plotted against Simpson’s diversity index from all pitfall traps from all four sample periods combined for Starlight Cave. Quantile regression estimates for upper 25th (y = 0.85x-2.95) and 50th (y = 0.66x-2.21) percentile bands in descending order.
Figure 3.16. Moisture content of in situ guano plotted against Simpson’s diversity index from 40 pitfall traps and four sample periods, combined for Starlight Cave. A five site binding hyperbola fitted the data with an r2 value of 0.42 although the result was not significant.
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Figure 3.17. Fresh guano deposition plotted against Simpson’s diversity index from 40 pitfall traps and four sample periods combined for Starlight Cave. The data show no significant linear correlation (p=0.19) with an r2 value of 0.04.