Acoustic monitoring and response of katydids (Orthoptera: Tettigoniidae) to the landscape mosaic in a Biosphere Reserve

Thompson, Aileen Celeste (2017-03)

Thesis (MScConsEcol)--Stellenbosch University, 2017.

Thesis

ENGLISH SUMMARY: A charismatic group within the Orthoptera, katydids can be found in a variety of habitat types world-wide due to their excellent bark and leaf mimicry skills. Most male katydids produce species-specific calls to attract female mates. If katydids, like their close relatives the grasshoppers, can function as effective biological indicators, then acoustic monitoring of katydid songs may result in a novel and non-invasive method to rapidly assess local biodiversity. Furthermore, information regarding threat statuses, distributions and life history traits can be inferred for all South African katydid species, leading to the development of a Katydid Biotic Index (KBI) based on the highly effective Dragonfly Biotic Index. If proven effective, the KBI would allow for biodiversity assessments to account for detailed aspects of katydid species composition in addition to the diversity measures normally utilized for biodiversity assessment (e.g. species richness and abundance). In this thesis, I provide the first steps towards determining whether the KBI could be an effective assessment technique. First I assess the utility of the KBI at a coarse-scale by determining its ability to identify regions of high conservation priority. Secondly, I conduct a fine scale study to determine the response of the katydid assemblage to habitat quality. And lastly, the first two aims are combined to determine whether the KBI is an appropriate method to assess habitat quality at a fine-scale. In Chapter 2, by using a subset of museum records, I investigate the distribution of the katydids within the Cape Floristic Region (CFR), a global biodiversity hotspot. The katydids found within the CFR follow the same trends with regards to threat status, endemism and life history traits to the overall South African katydid assemblage. The KBI assessment method was able to select, at this coarse-scale, the ecosystems of conservation priority. For Chapters 3 and 4, the Kogelberg Biosphere Reserve (KBR) was selected as a study area as it allowed for the acoustic monitoring and direct comparison of katydid assemblages and responses across the core, buffer and transition zones through the use of passive recordings. In Chapter 3 I found that the katydids of the KBR are not complementary across the zones. However, they respond positively in terms of abundance to measured habitat quality when the entire assemblage is considered. In Chapter 4 I found that katydids responded towards coarse-scale habitat quality and they were not as sensitive towards habitat change as was expected. By including abundances of the katydid species in to the KBI calculations, the sensitivity of the KBI as an assessment method was improved. For this reason, katydids in the fynbos biome are likely to not be effective indicators of habitat change on a small scale, likely due to the surprisingly low diversity of katydid species in the KBR. However, if the KBI were to be tested out in forest patches or areas with higher diversity, the KBI may prove more promising. For these reasons, a rapid assessment technique based on the KBI is likely to be more appropriate for some habitat types over others.

AFRIKAANSE OPSOMMING: ‘n Charismatiese groep binne die Orthoptera, sabel sprinkane, kan gevind word in 'n verskeidenheid van habitat tipes wêreldwyd as gevolg van hul uitstekende bas en blaar nabootsing vermoë. Die meeste manlike sabel sprinkane produseer spesie-spesifieke geluide om wyfies te lok. Indien sabel sprinkane, soos hul naasbestaandes die sprinkane, effektief as biologiese aanwysers funksioneer, kan akoestiese monitering van sabel sprinkaan geluide lei tot 'n unieke en nie-indringende metode om plaaslike biodiversiteit vinnig te evalueer. Verder, kan inligting rakende bedreiging statusse, verspreiding en lewensgeskiedenis eienskappe afgelei word vir alle Suid-Afrikaanse sabel sprinkaan spesies, wat kan lei tot die ontwikkeling van 'n Sabel Sprinkaan Biotiese Indeks (SBI) gebaseer op die hoogs doeltreffende Naaldekoker Biotiese Indeks (NBI). Indien dit as doeltreffend bewys word, sou die SBI voorsiening maak vir ‘n biodiversiteit assesseringsmetode om rekenskap te gee aan gedetailleerde aspekte van sabel sprinkaan spesiesamestelling bykomend tot die diversiteit maatreëls wat normaalweg gebruik word vir biodiversiteit assessering (bv. spesierykheid en volopheid). In hierdie tesis, wend ek die eerste poging aan om te bepaal of die SBI 'n effektiewe assessering tegniek kan wees. Ek het aanvanklik die gebruiklikheid van die SBI op 'n growwe skaal beoordeel deur die bepaling van die indeks se vermoë om areas van hoë prioriteit vir bewaring te identifiseer. In die tweede plek, doen ek 'n studie op ‘n fyn skaal om die reaksie van sabel sprinkaan spesiesamestelling tot habitat kwaliteit te bepaal. Laastens, is die eerste twee doelwitte gekombineer om te bepaal of die SBI 'n geskikte metode is om habitat kwaliteit te evalueer op 'n fyn skaal. In Hoofstuk 2, met die gebruik van ‘n gedeelte van museum rekords, ondersoek ek die verspreiding van sabel sprinkane binne die Kaapse Floristiese Streek (KFS), 'n globale biodiversiteit brandpunt. Die sabel sprinkane in die KFS volg dieselfde tendense met betrekking tot bedreiging status, endemisme en lewensgeskiedenis eienskappe in vergelyking met die algehele Suid-Afrikaanse sabel sprinkaan versameling. Die SBI assesseringsmetode was in staat, op hierdie growwe skaal, om die ekosisteme van prioriteit vir bewaring te selekteer. Vir Hoofstukke 3 en 4, is die Kogelberg Biosfeerreservaat (KBR) as studiegebied gekies omdat dit akoestiese monitering en direkte vergelyking van sabel sprinkaan spesiesamestelling en reaksies oor die kern, buffer en oorgang sones met gebruik van passiewe opnames toegelaat het. In Hoofstuk 3 het ek gevind dat die sabel sprinkane van die KBR nie aanvullende is oor die sones nie, maar hulle reageer positief in terme van volopheid gemeet teenoor habitat kwaliteit wanneer die hele spesiesamestelling in ag geneem word. In Hoofstuk 4 het ek bevind dat sabel sprinkane gereageer het teenoor growwe skaal habitat kwaliteit en hulle was nie so sensitief teenoor habitat verandering as wat verwag is nie. Deur die insluiting van volopheid van die sabel sprinkaan spesies in die SBI berekeninge is die sensitiwiteit van die SBI as 'n assesseringsmetode verbeter. Vir hierdie rede, is sabel springkane in die fynbos bioom geneig om nie doeltreffende aanduidings van habitat verandering op 'n klein skaal, waarskynlik as gevolg van die merkwaardige lae diversiteit van sabel sprinkaan spesies in die KBR. Maar, indien die SBI getoets sou wees in bos fragmente of gebiede met hoër diversiteit van sabel springkane, kan die SBI as meer belowend bewys word. As gevolg van laasgenoemde redes, is 'n vinnige assessering tegniek gebaseer op die SBI geneig om meer gepas vir sommige tipes habitat teenoor ander te wees.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101376
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