Spatial extent, regional specificity and metacommunity structuring in lake macrophytes

Abstract

Aim Spatial extent is inherently related to the potential roles of the main mechanisms structuring metacommunities. We examined the effects of varying spatial extent (ecological province, region and subregion) on the environmental and spatial components of variation in lake macrophyte communities. We also studied these effects separately for three macrophyte functional groups.

Diversity patterns of Pampean stream vegetation at different spatial scales

“…This is particularly relevant in the case of macrophytes, given their high dispersal rate (Santamaría, 2002). In some cases, and even between isolated bodies of water such as lakes, the spatial processes explain an important part of the macrophyte communities' structure (Capers et al, 2010;Alahuhta & Heino, 2013). However, in some other cases, community composition is explained by environmental factors and not by dispersal limitations (Sarneel et al, 2011).…”

Species sorting determines variation in the community composition of common and rare macrophytes at various spatial extents

“…Rare species probably respond to a narrower environmental spectrum than common macrophytes and may be affected by environmental factors similar to those affecting common species, but perhaps do so in a different manner (Lennon et al, 2011). Rare species may be specialised to extreme values (both low and high end of an environmental gradient), thus being less well represented in a metacommunity than common species with broad niches (Alahuhta and Heino, 2013). Rare species are also more vulnerable than common species to stochastic processes (Gaston, 1994;Fagan et al, 2005), which may also influence how well rare species are represented in a metacommunity.…”

“…This was illustrated by the differences in rare species across regions, and the finding that only one species (Lycopus americanus) was among the rarest species found in different regions (provinces 222 and 251). Such regional specificity in rarity is likely due to the fact that the underlying environmental gradients vary among the regions, and therefore have different effects on biotic communities in different regions (Heino et al, 2012;Alahuhta and Heino, 2013). In addition, the rarest species at the state extent were the emergents Agrostis stolonifera, Decodon verticullatus, Mimulus ringens and Ranunculus gleminii, and the hydrophytes Myriphyllum trifoliata, Myriophyllum farwellii, Najas guadalupensis and Utricularia gibba (Appendix S3).…”

“…Rare species are also more vulnerable than common species to stochastic processes (Gaston, 1994;Fagan et al, 2005), which may also influence how well rare species are represented in a metacommunity. Thus, a higher degree of unexplained variation for rare species may partly be due to stochastic processes (Capers et al, 2010;Alahuhta and Heino, 2013).…”

“…Extensive quality control efforts were used to reveal species that were difficult to identify or were identified to genus level; these were excluded from the database. Compared to the study of Alahuhta and Heino (2013), we focussed on all species instead of individual functional groups, which are only superficially discussed in the present study.…”