Temporal variability of nestedness and idiosyncratic species in stream insect assemblages

• Published in: Diversity and Distributions
• Main Authors: Heino, Jani, Mykrä, Heikki, Muotka, Timo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Northern Finland
• Online Access: http://dx.doi.org/10.1111/j.1472-4642.2008.00513.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1472-4642.2008.00513.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1472-4642.2008.00513.x

ABSTRACT Aims The nested subset pattern has been widely studied in the last 20 years, and recent syntheses have challenged the prevalence of this pattern in nature. We examined the degree of nestedness, its temporal variability and its environmental correlates in stream insects of a boreal drainage system. We also examined differences between nested and idiosyncratic species in site occupancy, niche position and niche breadth. Location Koutajoki drainage basin in northern Finland. Methods We used (i) nestedness analyses with three null models for testing the significance of nestedness; (ii) Spearman rank correlation to examine the correlates of nestedness; (iii) outlying mean index analysis to analyse the niche characteristics of species; (iv) and t ‐test to examine differences in niche breadth, niche position and site occupancy of idiosyncratic and other nested species. Results Stream insect assemblages were significantly nested in each of the three study years. The maximally packed matrices were significantly nested according to the nestedness calculator based on null models I (species frequencies and site richness equiprobable) and II (species frequencies fixed and site richness equiprobable), but non‐significant based on a conservative null model III (species frequencies and site richness fixed to those of the observed matrix). The most important correlate of nestedness was stream size, whereas isolation, productivity (total phosphorus) and habitat heterogeneity exhibited non‐significant relationship with nestedness. Idiosyncratic species occurred, on average, at more sites than nested species, mirroring the restricted distributions of several nested species that were inclined towards species‐rich sites. Idiosyncratic and nested species also differed in niche position and niche breadth, with idiosyncratic species having, on average, less marginal niche positions and wider niches than nested species. Main conclusions Stream size correlated with nestedness, possibly because small streams were inhabited only by ...