The contributions of biological control to reduced plant size and biomass of water hyacinth populations
- Authors: Jones, Roy W , Hill, Jaclyn M , Coetzee, Julie A , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68803 , vital:29326 , https://0-doi.org.wam.seals.ac.za/10.1007/s10750-017-3413-y
- Description: Water hyacinth is invasive in many countries, where it reduces aquatic biodiversity and limits water resource utilisation. Biological control of water hyacinth has been successful in South Africa, but has suffered from a lack of empirical data to prove causation. Insect exclusion trials were conducted to quantify the contribution of Neochetina eichhorniae and N. bruchi to the integrated control of water hyacinth on the Nseleni River, South Africa. Insecticide was not expected to induce phytotoxicity, but would prevent weevil damage in water hyacinth plants; and weevil herbivory was predicted to reduce plant petiole length, and above/below surface biomass. Results showed that insecticide had no phytotoxic effects and excluded weevils for 3 weeks, providing a baseline for field applications. Biological control on the Nseleni River directly affected water hyacinth biomass and petiole length, but did not affect plant cover. Plants subject to weevil herbivory demonstrated reductions in above and below surface biomass and had shorter petioles compared to insect-free plants. Dead biomass was also higher in biological control treatments. Biological control strongly affects plant size, biomass and vigour; however, further integrated control is required to facilitate reduction in mat cover, which is the goalpost for successful control of floating aquatic plants.
- Full Text: false
- Date Issued: 2018
The abundance of an invasive freshwater snail Tarebia granifera (Lamarck, 1822) in the Nseleni River, South Africa
- Authors: Jones, Roy W , Hill, Jaclyn M , Coetzee, Julie A , Hill, Martin P , Avery, T S , Weyl, Olaf L F
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69077 , vital:29382 , https://doi.org/10.2989/16085914.2017.1298984
- Description: The invasive freshwater snail Tarebia granifera (Lamarck, 1822) was first reported in South Africa in 1999 and it has become widespread across the country, with some evidence to suggest that it reduces benthic macroinvertebrate biodiversity. The current study aimed to identify the primary abiotic drivers behind abundance patterns of T. granifera, by comparing the current abundance of the snail in three different regions, and at three depths, of the highly modified Nseleni River in KwaZulu-Natal, South Africa. Tarebia granifera was well established throughout the Nseleni River system, with an overall preference for shallow waters and seasonal temporal patterns of abundance. Although it is uncertain what the ecological impacts of the snail in this system are, its high abundances suggest that it should be controlled where possible and prevented from invading other systems in the region.
- Full Text: false
- Date Issued: 2017
Comparisons of isotopic niche widths of some invasive and indigenous fauna in a South African river
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015
Using a unified invasion framework to characterize Africa’s first loricariid catfish invasion
- Authors: Jones, Roy W , Weyl, Olaf L F , Hill, Martin P , Swartz, Ernst R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418081 , vital:71507 , xlink:href="https://doi.org/10.1007/s10530-013-0438-7"
- Description: This paper presents evidence of establishment of a loricariid population in the Nseleni River in South Africa and uses a unified framework to determine its invasion stage. Specimens were identified morphologically as Pterygioplichthys disjunctivus (Weber 1991), but genetic barcoding results indicated close association with specimens that may have a hybrid history. The species was introduced into South Africa via the pet trade and the first record of introduction into the wild was in 2004. Samples collected in 2011 and 2012 demonstrated that there were multiple length cohorts in the population including juveniles (12–130 mm total length TL) and large (>300 mm TL) adult fish. Gonadal assessment of adults demonstrated the presence of reproduction capable specimens. The concurrent occurrence of mature adults and juvenile fish demonstrated establishment. Locality records indicate that P. disjunctivus has already spread between two rivers through an inter basin water transfer. Using a unified framework for invasions this invasion was categorized as a self-sustaining population in the wild with individuals surviving and reproducing a significant distance from their original point of introduction. Containment is suggested as potential management strategy.
- Full Text:
- Date Issued: 2013