Determinants of local abundance and range size in forest vascular plants

Abstract

Aim For a large set of forest herbs we tested: (1) whether there is a positive relationship between local abundance and geographical range size; (2) whether abundance or range size are affected by the niche breadths of species or niche availability; and (3) whether these are affected by the species life‐history traits. Location Northwestern Germany. Methods We measured abundance as mean density in 22 base‐rich deciduous forests and recorded range size as area of occupancy on four different spatial scales (local to national). Niche breadth was expressed in terms of habitat specificity (specialists, generalists) and of the ability to grow across a broad range of soil pH. The species’ pH niche position was used as a measure of the importance of habitat availability. As life‐history traits we used diaspore mass and number, plant height, seed longevity, lifespan/clonality, pollination mode, dispersal capability and flowering time. Results There were mainly no positive relationships between the abundance of species and their range size, as tested across species and across phylogenetically independent contrasts. Forest specialists were generally distributed less widely than generalists, but habitat specificity was not related to local abundance. Species with a broader pH niche breadth were more common, but the positive relationships between niche breadth and abundance or range size disappeared when accounting for sample size effects. Clonal species with few and heavy diaspores were most abundant, as well as early‐flowering species and those lacking dispersal structures. Local and regional range size were determined largely by habitat availability, while national range was positively affected by plant height and diaspore mass. Main conclusions Different processes determine the local density of species and their range size. Abundance within habitat patches appears to be related mainly to the species life histories, especially to their capacity for extensive clonal reproduction, whereas range size appears to be determined strongly by the availability of suitable habitat.

Plant attributes determining the regional abundance of weeds on central European arable land

“…species largely depend on the geographical and environmental context and the taxonomic or functional species assemblages studied (Lahti et al, 1991;Kelly, 1996;Hegde & Ellstrand, 1999;Cadotte & Lovett-Doust, 2002;Murray et al, 2002;Kolb et al, 2006;Pocock et al, 2006).…”

Effects of Detectability on Estimates of Geographic Range Size in Bignonieae

“…3) between estimated area of occupancy and detectability would have been obtained despite the bias, providing strong evidence against the hypothesis. Yet a positive relationship between true geographic range size and average local abundance has not been well established for plants (Kolb et al 2006). Particularly scarce are the analyses most relevant to our study, those encompassing estimates of both the full geographic range of species Figure 3.…”

Rarity as a life‐history correlate inDudleya(Crassulaceae)

“…Random dispersal would be a less plausible reason for a difference in range size in a contiguous landscape where each species would seem to be free to expand its range to the extent that it is ecophysiologically capable of doing so ( Kimball et al, 2004 ). The type of rarity that is a life-history correlate involves the rare and common species differing in niche breadth; the rare species does poorly in ecological settings where it does not live, whereas the common species does well in those settings and perhaps also does well in what is prime habitat for the rare species ( Debussche and Thompson, 2003 ;Kolb et al, 2006 ). In other words, there is a certain sort of habitat dependence , an interaction between habitat and rarity as it affects components of success in the species ' life history ( Thompson et al, 1999 ).…”

“…A species may be rare because it requires a habitat that is rare ( Burgman, 1989 ;Gaston, 1994 ;Kolb et al, 2006 ). A species will increase its range until it no longer fi nds the environmental conditions it needs given its traits ( Levin, 2000 ).…”