Evaluation of methods and approaches for surveying savanna invertebrates.
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Date
2006
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Abstract
The savanna is an important biome, which is under threat from land transformation, and it is therefore a
focus for conservation planning. Yet, the invertebrate fauna of this biome is poorly documented and
hence there is a need to provide baseline data for this component of biodiversity. This project aimed to
provide relevant information that can be used by conservation planners and ecologists, by recommending
a sampling strategy for the collection of specific taxa for savanna invertebrate surveys.
The effectiveness and efficiency of a sampling strategy using passive and active sampling methods was
assessed to provide recommendations for a multi-taxa approach to sampling invertebrates in a savanna
ecosystem. In the collection of data, volunteers assisted and they were evaluated in comparison with
experienced researchers to assess the effectiveness, efficiency and benefits of using volunteers to carry
out multi-taxa invertebrate surveys. In addition, cross-taxon congruency and congruency across
taxonomic levels were assessed between nine invertebrate taxa, to select potential surrogates to reduce
biodiversity survey costs for conservation planning.
Fieldwork was carried out in the Mkhuze Game Reserve (27.67°S:32.27°E, 400km2
), Phinda Private
Game Reserve (27.78°S:32.35°E, 140km2
) and False Bay Park (27.94°S:32.38°E, 25km2
) in north-eastern
Kwazulu-Natal, South Africa. Forty-three different sites were sampled between November 2002 and
March 2005 (summer months). Twenty of these sites were re-sampled across years and in different
months during the summer season, giving 77 sampling events. Fifty-four volunteers recruited by the
Earthwatch Institute assisted in the collection of data.
Lepidoptera, Hymenoptera (Apoidea), Diptera (Asilidae, Bombyliidae), Neuroptera, Odonata, Hemiptera
(Cicadellidae), Coleoptera (Cetoniinae, Scarabaeinae), Orthoptera, Blattodea, Isoptera, Araneae
(Araneidae, Thomisidae, Oxyopidae), Scorpionida, Myriapoda (Diplopoda, Chilopoda), Mollusca and
Annelida were sampled using four active searching methods (transects, tree beating, leaf litter and sweep
sampling) and two passive methods (pan traps and baited traps).
In its entirety, this project sampled 50 558 individuals from 797 invertebrate species and an extensive
database consisting of 33 257 records now exists. A standardised sampling protocol is described for the
effective sampling of multiple invertebrate taxa in a savanna biome and recommendations are made for
improving the efficacy and completeness of invertebrate surveys based on the application of species
accumulation models. Restrictive active searching methods (quadrats) were found to be more effective for
sampling epigaeic invertebrates and should be used in conjunction with leaf litter samples. Flying and
plant-dwelling invertebrates should be sampled using a range of sampling methods which include baited,
malaise and pan traps, active searching along transects and vacuum sampling. I suggest over 75% of the
Lovel/, s.1. - MSc. Thesis i ii
total estimated fauna to be a satisfactory and realistic level of inventory completeness for making valid
comparisons between regions and across sites.
Volunteers sampled lower rates of species accumulation, species richness and unique species when using
timed, active search methods. Nevertheless, volunteers and researchers were shown to perform equally
well when using un-timed, active searching methods. Previous experience or knowledge of scientific
method was beneficial when researchers assessed the perceived usefulness of volunteers to researchers for
carrying out fieldwork. The project experience raised the volunteers' environmental awareness,
knowledge about biodiversity, invertebrates and conservation research, and enabled volunteers to
participate in or design locally relevant conservation based projects on their return home.
Cross-taxon congruencies were observed. However, relationships were weak and potential surrogates
could not be selected. The use of higher taxonomic levels to represent species shows good potential as a
surrogate but only in species-poor genera or families. The use of species density to determine congruency
and select surrogates is likely to produce different results to those produced by community similarity.
Furthermore, when selecting surrogates from congruency assessments an optimal p-value greater than
0.75 should be required. Below this value, the relationship is likely to be weak and if used as a surrogate
misinterpretation may occur.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
Keywords
Invertebrates--KwaZulu-Natal., Savanna ecology., Invertebrate populations--Research--Methodology., Habitat conservation--Planning., Biodiversity conservation., Surveys--Methodology., Volunteers., Sampling., Invertebrates--Conservation., Savannas., Indicators (Biology)., Theses--Zoology.