The mesofilter concept and biodiversity conservation in Afro-montane grasslands

[摘要] ENGLISH ABSTRACT: Conservation planners use many traditional biodiversity conservation tools to help alleviatethe global biodiversity crisis. However, ongoing biodiversity loss has stimulated thedevelopment of new and improved methods for conserving biodiversity. One such newconservation tool is the mesofilter approach. Mesofilters are biotic or abiotic ecosystemelements which are critical to the well-being of many species, and therefore could help toexplain spatial heterogeneity in species across a landscape. It is also complementary to moretraditionally used concepts such as coarse- and fine-filter conservation concepts. Applying themesofilter approach in protected area, conservancy, or land-sparing design and management,could optimise biodiversity conservation in a rapidly developing world. For example, thetimber industry has been pro-active in its approach to lessen biodiversity loss, by optimisingdesign and management of the plantation matrix through ecological networks. Here, I explorethe use of mesofilters within highly threatened remnant Afro-montane grasslands inKwaZulu-Natal, South Africa, to optimise biodiversity conservation planning for suchlandscapes. As per anecdotal evidence, I used rockiness in the landscape as a possible driverof species richness and species assemblage variability at the meso-scale, using a multi-taxonand multi-trophic approach. In this montane landscape, I also examined the effect of elevationon spatial heterogeneity of taxa. I further examined the functional responses of taxa torockiness in the landscape. Rockiness in the landscape significantly influenced the speciesrichness and assemblage structure of three key grassland taxa: flora, butterflies, andgrasshoppers. I showed that for plants, this response was due to growth forms such asgeophytes and perennial grasses that were more closely associated with rockiness, andtherefore the main contributors to observed differences in the dispersion patterns of flora.Grasshoppers were not necessarily responding to higher rock exposure per se, but rathertowards the environmental conditions created by rockiness within the landscape, such aslower vegetation density. For butterflies, certain behavioural traits, such as resting, territorialbehaviour and/or mate-locating behaviour, were more typical in areas of higher rockexposure. This suggested that rocks are a definite habitat resource to certain butterflies.Overall, this finding where an abiotic surrogate is representative of key taxa in an ecosystemis interesting, as cross-taxon surrogacy has been shown to be stronger than surrogates basedon environmental data. Furthermore, taxa responded functionally to rockiness in thelandscape. This thesis therefore supports the idea that environmental surrogates are indeeduseful for biodiversity conservation planning. Furthermore, ecosystems can potentially have many attributes or features that would be of conservation interest, and delineating a set ofmesofilters is a useful way of expressing particular attributes to be used in wildlifeconservation evaluation. The concept of the mesofilter as a practical biodiversity conservationtool is therefore validated here. I also argue the importance of habitat heterogeneity forbiodiversity conservation planning in this montane grassland landscape. The potential foroptimising the design of landscape configurations such as ecological networks, throughinformation obtained from the mesofilter, is emphasised. We can safely add another tool inthe biodiversity conservation toolbox of this Afro-montane grassland ecosystem.

[发布机构] Stellenbosch University