Niche breadth, rarity and ecological characteristics within a regional flora spanning large environmental gradients

Abstract

Aim Species specialization, which plays a fundamental role in niche differentiation and species coexistence, is a key biological trait in relation to the responses of populations to changing environments. Species with a limited niche breadth are considered to experience a higher risk of extinction than generalist species. This work aims to measure the degree of specialization in the regional flora of the French Alps and test whether species specialization is related to species rarity and ecological characteristics.Location This study was conducted in the French Alps region, which encompasses a large elevational gradient over a relatively limited area (26,000 km 2 ).Methods Specialization was estimated for approximately 1200 plant species found in the region. Given the inherent difficulty of pinpointing the critical environmental niche axes for each individual species, we used a co-occurrencebased index to estimate species niche breadths (specialization index). This comprehensive measurement included crucial undetermined limiting niche factors, acting on both local and regional scales, and related to both biotic and abiotic interactions. The specialization index for each species was then related to a selection of plant typologies such as Grime strategies and Raunkiaer life-forms, and to two measurements of plant rarity, namely regional area of occupancy and local abundance.Results Specialist species were mainly found in specific and harsh environments such as wetlands, cold alpine habitats and dry heathlands. These species were usually geographically restricted but relatively dominant in their local communities. Although none of the selected traits were sufficient predictors of specialization, pure competitors were over-represented amongst generalist species, whereas stress-tolerant species tended to be more specialized.Main conclusions Our results suggest that co-occurrence-based indices of niche breadth are a satisfactory method for inferring plant specialization using large species samples across very heterogeneous environments. Our results are an empirical validation of the tolerance-dominance trade-off and also provide interesting insights into the long-standing question of which biological properties characterize species with narrow niche breadth that are potentially threatened by global changes in the environment.

Niche-breadth of freshwater macrophytes occurring in tropical southern African rivers predicts species global latitudinal range

“…Some can be applied to all organisms, whilst others (e.g., food-web based studies) are appropriate for animals, but much less so, or not at all, for plants. Some studies have used individual niche-axis traits to quantify species niche-breadth (e.g., Luna and Moreno, 2010;Boulangeat et al, 2012). Other approaches aim to determine species niche-breadth in terms of the proportion of populations found in, or using, the individual states of given resources (e.g., Carrillo-Angeles et al (2016), who utilised a resource-state niche-breadth index developed by Hulbert (1978), in a study of the cactus genus Astrophytum).…”

Improving plant functional groups for dynamic models of biodiversity: at the crossroads between functional and community ecology

“…The National Alpine Botanical Conservatory (CBNA) provided the vegetation-plot database of flora in the surrounding region, including 11,628 community-plots and 1,579 species sampled between 1980 and 2009 ( Fig. 3 and see Boulangeat et al, 2012). Within each community-plot, species cover (in its strata) was recorded in six classes (1: less than 1%; 2: 1 to 5%; 3: 5 to 25%; 4: 25 to 50%; 5: 50 to 75%; 6: up to 75%) (Braun-Blanquet, 1946).…”

Environmental tolerances of rare and common mangroves along light and salinity gradients

“…Among the hypothesized explanations for the restricted distributions of rare endemics compared to common widespread species is that the former have smaller fundamental niches, possessing more limited ranges of physiological tolerance or more specialized resource or other habitat requirements (Kruckeberg and Rabinowitz 1985;Boulangeat et al 2012;Slatyer et al 2013). If these requisite conditions and resources are of limited spatial extent, or are otherwise difficult to access, then the distribution and abundance of a species that depends on them will be constrained as well.…”

“…Species whose populations are typically sparse and patchily distributed tend to have narrower geographical ranges than common species (Hanski 1982;Gotelli and Simberloff 1987;Collins and Glenn 1990;Gaston and Lawton 1990;Hanski et al 1993;Boulangeat et al 2012). Among the hypothesized explanations for the restricted distributions of rare endemics compared to common widespread species is that the former have smaller fundamental niches, possessing more limited ranges of physiological tolerance or more specialized resource or other habitat requirements (Kruckeberg and Rabinowitz 1985;Boulangeat et al 2012;Slatyer et al 2013).…”