Ecological niche differentiation among six annual Lythrum species in Mediterranean temporary pools.

Antoine Gazaix,John D Thompson,Patrick Grillas,Florent Sabatier,Virginie Pons,Guillaume Papuga,Perrine Gauthier,Hugo Fontes

doi:10.1007/s00442-021-05067-7

Abstract

The ecological niche defines the favourable range of a species in a multidimensional space of ecological factors that determine the presence and function of individuals. This fundamental concept in ecology is widely used to understand plant species coexistence and segregation. In this study, we test for ecological differentiation among six annual Lythrum species that are characteristic of temporary pools in the South of France, where they either coexist or occur separately. We first analysed the co-occurrence of species at two different geographical scales: cluster analyses of species presence in 10km grid cells and coexistence in 0.25 m2 quadrats within populations of each species. Second, for three to nine populations of each species, we quantified a range of biotic and abiotic parameters using point contacts and soil measurements in five 0.25 m2 quadrats per population. We performed PCA on all variables and analysed each variable separately to compare the ecological niche features of the six species. A phenological index was assessed for the plant community of each site. We detected highly localized niche differentiation in terms of soil pH (all species) and for a range of variables among pairs of species. The six species also showed marked differences in the flowering period relative to the mean and variability of flowering time in their local community. These fine-scaled niche differences are associated with phylogenetic distances among species and may contribute to species' coexistence. These results are integrated in a conservation management plan for the habitat of the rarest species in this group.

Highlights

The concept of the ecological niche has long been a central tool in the science of ecology and evidence has steadily grown for the role of niche differentiation in species coexistence (Silvertown 2004)
Three populations of L. hyssopifolia were sampled in all three regions, three populations of L.borysthenicum, L thymifolia and L. tribracteatum were sampled in each of two regions, and L. thesioides and L. portula were sampled in only one region due to their rarity (Gazaix et al 2019)
Our study revealed marked differences in the ecological niche of six studied annual Lythrum species in terms of highly localised spatial variation in ecological parameters and flowering period

Summary

Introduction

The concept of the ecological niche has long been a central tool in the science of ecology and evidence has steadily grown for the role of niche differentiation in species coexistence (Silvertown 2004). The wide range of ecological factors that determine the niche of individual species render niche description a complex issue (Pulliam 2000). They are often used to study niche variation, broad habitat units or vegetation types do not provide the correct scale to identify the precise ecological niche of plants (Hall et al 1997; Lavergne et al 2004; Miller and Hobbs 2007; Papuga et al 2018; Thompson 2020). Among the different parameters involved, soil nutrient content (Paoli et al 2006), pH (Hájková and Hájek 2004) and texture (Tuomisto 2006), hydrology (Silvertown 2004, Silvertown et al 2015) and mineral characteristics (Lavergne et al 2004; Papuga et al 2018) are all well known to contribute to niche differentiation among species and populations

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