Spatial distribution of rare species in lotic habitats

Abstract

Abstract. 1. Species rarity is a common phenomenon in the biological world. Although rare species have always interested biologists, the meaning of 'rare' has not always been clear with the definition of rarity often arbitrary.2. In the current study, we investigate rarity in stream ecosystems using black flies (Diptera: Simuliidae). We defined rare species a priori as those species found ≤ 10% of stream sites examined (n = 111 streams for 'summer collections'; n = 88 collection for 'spring' collections). Hence, we are exploring only one axis of rarity, restricted range.3. We first consider the distribution of each rare species separately to determine if the mean (euclidian) distance among streams (habitats) for each rare species differs from a random model. We next took a collective approach by pooling all rare species to determine the influence of stream conditions, niche breadth, and distance among habitats on rarity.4. Even within this biologically uniform group of flies, dispersal, range limits, and stream conditions all might play a role in rarity, and the importance of each of these factors appear to vary among species. Rather than looking for broad causes of rarity, future studies might be more fruitful if they looked at species-specific causes.

Deconstructing occupancy frequency distributions in stream insects: effects of body size and niche characteristics in different geographical regions

“…Furthermore, frequent local extinctions and colonisation are certainly important for the dynamics of species in highly disturbed systems such as streams, although there is a deficit of such direct information for stream insects in general (Heino & Peckarsky, 2014; but see Hildrew, 2009). However, the assumption of habitat homogeneity definitely does not hold for stream systems because they are highly heterogeneous environments at a range of spatial scales, with both physical habitat conditions and water chemistry varying widely among streams (Malmqvist & Mäki, 1994;McCreadie & Adler, 2008;Heino, 2013;McCreadie & Bedwell, 2013). This is where the niche characteristics come into play.…”

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

“…We assumed that the degree of rarity is probably region-specific at the species level (see also McCreadie and Adler, 2008). 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).…”

Biotope prioritisation in the Central Apennines (Italy): species rarity and cross-taxon congruence

“…Arita et al 1990;Kattan 1992;Dobson and Yu 1993;Mills and Schwartz 2005;Santoul et al 2005;Flather and Sieg 2007;McCreadie and Adler 2008). Thus, we are faced with two problems in biotope prioritisation: (1) crosstaxon incongruence and (2) species prioritisation.…”