Range-size, local abundance and germination niche-breadth in Mediterranean plants of two life-forms

Abstract

The relationships between rarity (i.e., range-size, local abundance) and niche-breadth can be important to assess the risks the species face under global change, namely those resulting from fire regime change. In fire areas, germination is critical for establishing after fire for many species. We examined the relationships between rarity and germination niche-breadth for 53 plant species of two life-forms (chamaephytes and hemicryptophytes) growing in Eastern Spain. Rarity was measured as geographic range-size and as local abundance. Local abundance was evaluated at two sites differing in their post-fire successional status (a recently burned area and a long-unburned one). Germination niche-breadth was measured as the mean germination evenness index from four germination experiments that subjected the seeds to various germinating conditions characteristics of fire environments. Correlations between rarity (range-size, local abundance) and niche-breadth were calculated in cross-species mode or by way of phylogenetically independent contrasts, and either for the 53 species (all-species set) or for each of two life-form groups (chamaephytes, hemicryptophytes). In general, no significant correlations were found between the rarity measures and germination nichebreadth for the all-species set. However, significant correlations emerged when the analyses were done separating species by life-forms. Germination nichebreadth was positively correlated with range-size for chamaephytes, and negatively for hemicryptophytes. In addition, germination niche-breadth was uncorrelated, or negatively so, with local abundance for chamaephytes and hemicryptophytes, respectively. While no correlation between range-size and local abundance was found for chamaephytes, a negative one was obtained for hemicryptophytes. We conclude that rarity/germination-niche relationships varied by life-form. This pattern of relationships was obscured when all species were joined in a single group. Based on the contrasting patterns of correlations obtained for each life-form we argue that the changes in the germinating environment caused by alterations in fire regime are likely to differentially affect these two groups of species.

What can routine germination tests in seed banks tell us about the germination ecology of endemic and protected species?

“…By preparing for the subsequent stages of establishment, further growth and development, germination is fundamental for plant adaptation (Donohue et al 2010). The range of conditions eliciting germination of a plant determines the breadth of its niche and geographic range (Donohue et al 2010;Luna and Moreno 2010). Among the factors which define the germination niche, temperature is of paramount importance, frequently regulating seed germination (Baskin and Baskin 1998;Probert 2000).…”

“…Despite the large number of publications characterizing germination niches of individual species or groups of species (e.g. Baskin and Baskin (1998) and references therein; Luna and Moreno (2010)), the available information is often limited for most rare and threatened species, and specific to certain floras (Crawford et al 2007;Godefroid et al 2010). The Secretariat of the Convention on Biological Diversity (2009) has even highlighted that ex situ conservation is often constrained by the absence and/or limited accessibility of data, tools and technologies.…”

“…On the contrary, species-specific requirements for germination are prevalent, which is frequently attributed to the specific habitats in which those species occur (e.g. high mountain habitats, specific microclimates) (Herranz et al 2002;Giménez-Benavides et al 2005;Lorite et al 2007;Luna and Moreno 2010). Therefore, a thorough understanding of the germination ecology is critical to optimise conservation efforts, and to contribute to a better understanding of potential species responses to climate change.…”

Plant recruitment and range size: Transition probabilities from ovule to adult in two Ipomoea

“…Indeed, as the lower probability of successfully establishing in narrowly distributed species may be related to narrower regeneration niches (e.g., Brändle et al, 2003;Luna and Moreno, 2010), future experimental studies of the regeneration niche of these Ipomoea species (sensu Grubb, 1977) might be of particular importance to disentangling the mechanisms limiting the distribution of I. rubriflora. The lower local abundance of I. rubriflora at the study sites seems to support the idea of a lower regeneration niche, as hypothesized for narrowly distributed species (Gaston, 2003).…”

“…Although the study of the causes of plant range size has long history (Stebbins, 1942;Rabinowitz et al, 1987;Gaston, 2003;Lavergne et al, 2004;Van der Veeken et al, 2007;Luna and Moreno, 2010), a general explanation for narrow distributions in plants has yet to emerge and thus more comparative studies are still needed (Murray et al, 2002;Gaston, 2009). In this sense, studies considering several pairs of closely related species with contrasting distributions may be particularly valuable (e.g., Lavergne et al, 2004;Van der Veeken et al, 2007).…”