Moretti (et al 2009) examined bee communities in response to fire as a model of animal function trait response to environmental change. The study took place in two different regions; a temperate climate on a mountainside in Switzerland, and a Mediterranean climate in Israel. The climate in Switzerland was wet/warm in the summer, and dry/cool in the winter, while Israel was hot /dry in the summer, and cool/wet in the winter. Both areas are prone to fire but they occur more frequently, of higher intensity/extent, and during the summer in the Mediterranean climate, while in the temperate climate they are of low-medium intensity and quick spreading, furthermore they mainly occur in the winter (coinciding with vegetation dormancy).
Bees were collected at 21 sites in each of the study areas. These sites were located in a range of habitats in different succession stages following fire (e.g. from recently experienced fire, to no fires for 20-30 years, to unburnt areas). Bees were identified and functional traits were described. Functional traits, listed in Table 2, are such things as nesting specialization (in the mud, in wood, snail shells etc.), dispersion (measured as ITD, inter-tegula distance, i.e., distance between wings), or other characteristics of an organism which has demonstrable links to the organism’s functions. Functional traits were calculated into mT, an average for a given trait weighted by species abundance, and a measure of functional diversity (FD). *this may be a rough definition, but I understand functional diversity as the diversity or range of things that an organism, or an organisms traits, do in a community*.
The hypotheses of this study were: “(i) fire affects both species and functional composition of bees at both taxonomic and functional levels, that is, through extinctions, immigrations, or dominance redistribution within the community; (ii) the response of bee communities to fire is smaller in the Mediterranean region because of the longer history of fire in arid conditions”.
Following fire disturbance, a greater number of species were present than pre-fire conditions in both climates. However, this diversity of species decreased quickly following fire, likely because habitats immediately following fire support the highest floral diversity compared to later successional stages.
Functional traits selected by fire were similar in both countries, but some traits were identified which were affected differently between the two regions (Table 4). This differentiation in trait responses highlights the effects of the regional climates and fire regime on the functional components within the regional species pool. This can be further explained by looking at Figure 2, which displays the variance of mean traits and functional diversity in each climate. Overall, mean traits and functional diversity change more dramatically in Switzerland than in Israel (Figure 1). Changes in functional diversity in Israel due to fire were not significant, while they were Switzerland (albeit, only be 21.9%).
What this tells us, is that the responses of bee traits to fires are not exclusively a result of the fire regime in the area, rather, the climate of the region as a whole, including landscape structure. The climate and landscape influence the diversity of traits present. In Israel, the landscape is highly heterogeneous as a result of land use, vegetation type, and fire, resulting in higher heterogeneity in species and trait assemblage. Switzerland, on the other hand, dominated by quickly establishing chestnut trees, is less heterogeneous, and therefore, there is less heterogeneity in bee species and trait assemblage. So, despite results showing a significant shift in species composition with fire in both regions, the functional composition of the bees present in the Mediterranean remained stable, likely as a result of the regions characteristics and functions and higher diversity of traits in the system.
Below is a link to a presentation by Moretti. It discusses some of his other work, but the 2009 paper is presented beginning at slide 51. I recommend looking through the entire presentation as it’s pretty interesting/helpful. Also, note page 58, it has a figure of the species response to fire in both the Mediterranean and temperate climates (I think this would have been good to show in the paper, but I guess if he had to cut a figure, this would be the best one).
I’ll update this if any issues/questions arise in class. See ya in a few hours!
http://www.eurac.edu/NR/rdonlyres/836134A5-3468-4888-979C-C32A14370A06/0/Moretti_Marco.pdf
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