Grasshoppers of azonal riparian corridors and their response to land transformation in the Cape Floristic Region

Pronk, Bianca Mignon (2016-03)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: The Cape Floristic Region (CFR) is a global biodiversity hotspot with high levels of endemism across many taxa, including Orthoptera. Azonal vegetation, a much forgotten component of the CFR, is a unique vegetation type that forms part of the riparian corridor. This is a complex, unique and diverse ecosystem with high levels of local biodiversity that connects the aquatic and terrestrial realms. The riparian corridor is highly disturbed through anthropogenic activities and invasion by alien vegetation causing deterioration of riparian corridors. Most natural riparian corridors are now confined to the mountainous slopes and higher elevations. Grasshopper assemblages are good bioindicators of environmental change and habitat deterioration. In response to this I determined the grasshopper assemblage which characterizes the natural riparian and adjacent terrestrial zone and their dispersion across the two zones. I also investigated how grasshoppers respond to riparian corridor disturbances (land transformation) and if they are viable candidates for bioindication of riparian corridors. In Chapter 2 I investigated the ecology of grasshoppers (Orthoptera: Acridoidea) within a non-biome specific natural riparian zone along an important river in the CFR (Lourens River). Grasshopper sampling took place in the natural riparian and terrestrial zones along seven sampling units (SU‟s) that were 25 m in length and 35 m wide, in both the riparian and terrestrial zones. The riparian sites were along the river in the riparian corridor whereas the terrestrial sites were farther away. I did find a significant difference between the natural riparian and terrestrial grasshopper assemblages, but I indicated that grasshopper abundance and species richness may be more associated with the riparian vegetation. In Chapter 3, I investigated how grasshoppers respond to land transformation along the riparian corridor of an important river in the CFR (Lourens River), whilst investigating the possibility of grasshoppers as bioindicators. Grasshopper sampling took place in different land use types (LUTs) (natural, agricultural, cleared of invasive alien-trees, invaded by alien-trees and an urbanized riparian area) along the riparian corridor. Each LUT had seven SU‟s per site where grasshopper sampling took place (as per Chapter 2). I found that grasshopper diversity is significantly influenced by the different LUTs and no CFR endemic grasshoppers were present within the invaded or urbanized riparian area. I found that the agricultural and cleared riparian areas had the highest abundance of grasshoppers and were most speciose with a great abundance of CFR endemic grasshoppers. I found that the cleared riparian LUTs had the most CFR endemic grasshopper richness and abundance. In general I found that grasshoppers respond to the different LUTs. In conclusion, there exists a riparian grasshopper assemblage in the natural riparian zone of the CFR. Conservation is hereby critical in this area as it adds to the biodiversity of the region. Land uses had significant influences on grasshopper assemblages, especially on CFR endemic grasshoppers along the riparian corridor. The conservation and maintenance of the mixture between riparian and fynbos plants are important for grasshopper assemblages and more so for the persistence of CFR endemic grasshoppers. Riparian corridor conservation and maintenance is critical for the maintenance and enhancement of grasshopper biodiversity in a biodiversity hotspot, the CFR.

AFRIKAANSE OPSOMMING: Die Kaapse Floristiese Streek (KFS) is 'n wêreldwye kuberkol biodiversiteit met hoë vlakke van endemisme oor baie taksons, insluitend Orthoptera. Azonal plantegroei, 'n veel vergete deel van die KFS, is 'n unieke tipe plantegroei. Die azonal plantegroei vorm deel van die rivieroewers gang wat kompleks, uniek en 'n diverse ekosisteem met hoë vlakke van plaaslike biodiversiteit asook „n verbinding is tussen die land- en akwatiese ryke. Die oewergebied gang is hoogs versteur deur menslike aktiwiteite en inval deur indringerplante dit veroorsaak agteruitgang van rivieroewers gange. Mees natuurlike rivieroewers gange is nou beperk tot die berghellings en hoër hoogtes. Sprinkaan versamelinge is goeie bioindicatoren vir omgewing verandering en habitat agteruitgang. In reaksie op hierdie bepaal ek die sprinkaan versameling wat die natuurlike oewereienaars en aangrensende landelike gebied karaktiseer en hulle verspreiding oor die twee sones. Ek ondersoek ook hoe sprinkane reageer op rivieroewers gang versteurings (land transformasie) en as daar lewensvatbare kandidate vir bioindication van rivieroewers gange bestaan. In Hoofstuk 2 ondersoek ek die ekologie van sprinkane (Orthoptera: Acrididoidea) binne 'n nie-bioom spesifieke natuurlike oewersone langs 'n belangrike rivier in die KFS (Lourens River). Sprinkaan monsterneming het plaasgevind in die natuurlike rivieroewers en terrestriële sones langs sewe monsterneming eenhede (US) wat 25 m in lengte en 35 m breed was, in beide die rivieroewers en aardse sone. Die oewergebied terreine is langs die rivier in die rivieroewers gang terwyl die aardse terreine verder weg is. Ek het 'n „n groot verskil tussen die natuurlike en aardse rivieroewers sprinkaan versameling gevind, maar ek toon aan dat sprinkaan oorvloed en sort rykste miskien „n assosiasie het met die plantegroei van die rivieroewers. In Hoofstuk 3 ondersoek ek hoe sprinkane reageer op land transformasie langs die rivieroewers gang van 'n belangrike rivier in die KFS (Lourens River), terwyl ek ondersoek na die moontlikheid van sprinkane as bioindicatoren. Sprinkaan monsterneming het plaasgevind in verskillende tipes grondgebruike (LUTs) (natuurlike, landbou, verwydering van uitheemse bome, binnegeval deur uitheemse bome en 'n verstedelikte rivieroewers area) langs die rivieroewers gang. Elke LUT het sewe US per staanplek waar sprinkaan monsterneming plaasgevind het (soos per Hoofstuk 2). Ek het gevind dat sprinkaan diversiteit aansienlik beïnvloed word deur die verskillende LUTs en geen KFS endemiese sprinkane teenwoordig is in die binnegeval of verstedelikte rivieroewers gebied was. Ek het gevind dat die landbou- en skoongemaak oewergebiede het die hoogste oorvloed van sprinkane en mees soort rykste is met 'n groot menigte van KFS endemiese sprinkane. In die algemeen het ek gevind dat sprinkane reageer op die verskillende LUTs. Ten slotte, is daar 'n spesifieke rivieroewers sprinkaan fauna in die natuurlike oewersone van die KFS. Bewaring is hiermee krities in hierdie gebied as dit voeg om die biodiversiteit van die streek. landgebruike toon „n beduidende invloed op sprinkaan versamelinge, veral op die KFS endemiese sprinkane langs die rivieroewers gang. Die bewaring en instandhouding van die mengsel tussen oewereienaars en fynbos plante is belangrik vir sprinkaan versameling en meer so vir die voortbestaan van die KFS endemiese sprinkane. Rivieroewers gang bewaring en instandhouding is van kritieke belang vir die instandhouding en verbetering van sprinkaan biodiversiteit in 'n biodiversiteit kuberkol, die KFS.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98354
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