Recovery of Endemic Dragonflies after Removal of Invasive Alien Trees

Samways, Michael J.; Sharratt, Norma J.

doi:10.1111/j.1523-1739.2009.01427.x

Cited by 104 publications

(66 citation statements)

References 17 publications

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“…This suggests that recovery of sensitive, endemic taxa is delayed after clearing, and only occurs after recovery of indigenous Prionium and fynbos. Tolerant, widespread taxa therefore appear to be the first to recover, as with dragonflies in the region (Samways and Sharratt 2010). King and Schael (2001) noted that disturbed rivers lost their signature identities, perhaps through the loss of sensitive species.…”

Section: Response Of Endemic Taxamentioning

confidence: 96%

“…Temporally varying environments also favour generalists over specialists in relative fitness (Suhling et al 2006), so that increased diurnal and seasonal fluctuations in temperature and insolation in exposed, cleared sites, favours more tolerant generalists. Rare, endemic or stenotopic species generally take longer to return, as shown by Odonata in the region (Samways and Sharratt 2010).…”

Section: Environmental Responses To Alien Disturbancementioning

confidence: 99%

“…Using the South African Scoring System, a biotic index based on sampling macroinvertebrates, a score was assigned to each family, based on known sensitivity/tolerance of that family to changes in water condition (Dickens and Graham 2002). Sensitive invertebrate taxa used in macroinvertebrate scores include Ephemeroptera, Plecoptera, Trichoptera (EPT taxa) (Rosenberg and Resh 1993) and the Odonata (Dickens and Graham 2002;Smith et al 2007;Samways 2009, 2010;Samways and Sharratt 2010) (EPTO taxa), and were therefore a focus here.…”

Section: Benthic Macroinvertebrate Samplingmentioning

confidence: 99%

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Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

2010

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Invasive alien trees along river banks can reduce indigenous biodiversity, while their removal can restore it. We assessed here family-and specieslevel responses of river benthic macroinvertebrate assemblages to three riparian vegetation types (natural, alien trees, cleared of alien trees) in the Cape Floristic Region biodiversity hotspot. High species beta diversity of this highly endemic fauna meant that between-river, as well as seasonal effects, dominated assemblage patterns. SASS5, a qualitative, rapid bioassessment technique, based on the sensitivity of the families present, was used as a measure of river health and, indirectly, of water quality. SASS indicated a decline in water quality conditions after alien clearing, a likely response to the greater insolation and apparent erosion of cleared banks, resulting in elevated temperatures and suspended solids and lowered oxygen levels. Overall, cleared and natural sites were more similar to each other than to alien sites, suggesting some post-clearing recovery. However, many sensitive, endemic taxa survived in alieninvaded sites, and more than in the natural sites. These endemic species made use of shady, cool, highoxygen levels under the alien tree canopy. However, endemics declined in overall abundance in sites cleared of aliens, being replaced by more tolerant, widespread taxa. Clearance of the alien trees opened up the rivers to sunny conditions, which had a major impact on community composition. Vegetation types, oxygen levels and river width were important environmental variables affecting these macroinvertebrate responses. Re-establishment of invertebrate biodiversity matched that of indigenous vegetation, with the most sensitive endemic taxa only recovering after establishment of bushy indigenous and shadeproducing fynbos. Therefore, for biodiversity conservation objectives to be achieved, it is essential that indigenous plants are maintained and encouraged during and after clearing to ensure the recovery of endemic and sensitive taxa.

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Section: Response Of Endemic Taxamentioning

confidence: 96%

Section: Environmental Responses To Alien Disturbancementioning

confidence: 99%

Section: Benthic Macroinvertebrate Samplingmentioning

confidence: 99%

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Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

2010

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“…Even though fynbos was much more species rich than vineyards, their assemblages nevertheless grouped close together, suggesting that the conversion to vineyards was much more faithful in maintaining indigenous ecological integrity than was conversion caused by alien trees. Why this is so is not clear but shading might play a role, because shade from alien trees is the key factor affecting some aerial insects in the same area (Samways and Sharratt 2010). However, as the arthropods here are living in, and dependent on, the litter and soil, there is likely to be a whole host of chemical and physical factors, not measured here, playing a role at various spatial scales from a meter or two to several hundreds of kilometres.…”

Section: Arthropods Restricted To Particular Vegetation Typesmentioning

confidence: 95%

Comparative footprint of alien, agricultural and restored vegetation on surface-active arthropods

Magoba

Samways

2011

Biol Invasions

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Both invasive alien trees and agricultural conversion have major impacts on biodiversity. We studied here the comparative impact of these two types of land transformation on a wide range of surface-active arthropod species using pitfall traps, with evergreen sclerophyllous natural vegetation (fynbos) as the control. The study was in the Cape Floristic Region, a global biodiversity hotspot, where alien trees are of major concern and where vineyards replace natural fynbos vegetation. Surface-active arthropods were selected as they are species rich, relatively immobile, and occur in high abundance. We hypothesized that the impact of the two types of land cover transformation would produce similar qualitative and quantitative effects on the arthropods. We also compared the results in the transformed and natural areas with those in areas cleared of alien trees. Arthropod species richness in cleared areas was higher than in vineyards and more similar to that in natural fynbos, while alien trees had the lowest. Overall abundance scores were highest in cleared areas, closely followed by fynbos, then vineyards and lowest in alien trees. Several species were restricted to each vegetation type, including alien trees. In terms of assemblage composition, all vegetation types were significantly different, although fynbos and vineyards grouped, suggesting that vineyards have less impact on the arthropod community than do alien trees. When rare species were excluded, vineyards and cleared sites grouped, indicating some recovery but only involving those species that were common and habitat tolerant. Our results suggest that vineyards retain a greater complement of indigenous species than alien trees, but that clearing of these aliens soon encourages establishment of indigenous species. Although there were significant differences in soil moisture and litter depth within and between vegetation types, we did not record them as significantly affecting species richness or abundance, even in alien vegetation, an encouraging sign for restoration.

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“…While the majority appear to be having negative consequences for diversity, this is not always the case. One demonstration thereof is the return of endangered species following clearing of riparian invasive trees (Samways & Sharratt 2010). Moreover, few investigations have been made of how changing climate may reduce the impacts of currently invasive species, or diseases, though obviously this has to be the case in some instances (Bradley et al 2009;Lafferty 2009).…”

Section: Discussionmentioning

confidence: 99%

Temporal biodiversity change in transformed landscapes: a southern African perspective

Chown

2010

Phil. Trans. R. Soc. B

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Landscape transformation by humans is virtually ubiquitous, with several suggestions being made that the world's biomes should now be classified according to the extent and nature of this transformation. Even those areas that are thought to have a relatively limited human footprint have experienced substantial biodiversity change. This is true of both marine and terrestrial systems of southern Africa, a region of high biodiversity and including several large conservation areas. Global change drivers have had substantial effects across many levels of the biological hierarchy as is demonstrated in this review, which focuses on terrestrial systems. Interactions among drivers, such as between climate change and invasion, and between changing fire regimes and invasion, are complicating attribution of change effects and management thereof. Likewise CO 2 fertilization is having a much larger impact on terrestrial systems than perhaps commonly acknowledged. Temporal changes in biodiversity, and the seeming failure of institutional attempts to address them, underline a growing polarization of world views, which is hampering efforts to address urgent conservation needs.

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Recovery of Endemic Dragonflies after Removal of Invasive Alien Trees

Cited by 104 publications

References 17 publications

Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

Effect of alien riparian vegetation and its removal on a highly endemic river macroinvertebrate community

Comparative footprint of alien, agricultural and restored vegetation on surface-active arthropods

Temporal biodiversity change in transformed landscapes: a southern African perspective

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