Читать книгу Ecology - Michael Begon - Страница 32

While plant scientists have tended to be keener on classifying floras than animal scientists on classifying faunas, an analogous approach can be of use to resource managers. For example, agriculture in the catchment area of streams can have profound impacts on the invertebrate communities they contain, and just as with Raunkiaer's classification of plants, the patterns may be more closely related to species traits (paralleling Raunkiaer's life form spectra) than to taxonomic composition. Doledec et al. (2006) found that traits associated with population resilience (the ability to bounce back following perturbations), including short generation time and hermaphroditic reproduction, became more prevalent with increasing agricultural intensity in the catchment, reflecting more frequent and intense variations in stream nutrient concentrations (Figure 1.25). There was also a shift away from laying eggs at the water surface and a decrease in gill respiration, reflecting the increasing likelihood of smothering by sediment introduced as a result of ploughing or disturbance of soil and stream banks by grazing animals. The representation of these and other species traits can be used to devise indexes and thresholds of stream health that managers can aspire to attain or restore (Serra et al., 2017).

Figure 1.25 Species traits in streams. Relationships between the representation of species traits of stream invertebrates (% of individuals possessing the trait in the multispecies community as a whole) and the intensity of agriculture in the catchment area of the stream. None, ungrazed native tussock grassland; low, grazed native tussock grassland; medium, extensively grazed pasture; high, dairy or deer farming. Plurivoltine, more than one generation per year; short lives, 10–30 days; hermaphroditism, one individual possessing both sexes; surface eggs, laying unattached eggs at the stream surface; gill respiration, having external gills.

Source: From Doledec et al. (2006).