Nurse plants promote taxonomic and functional diversity in an arid Mediterranean annual plant community

Aims Research in the last decades supports the idea that certain species, namely ‘nurse species’, can enhance ecosystem function and species diversity in their vicinity through amelioration of the abiotic environment. However, few studies have explored whether nurse plants can promote functional diversity at the microhabitat level. Here, we evaluated the hypothesis that nurse plants can increase functional diversity in the beneficiary annual plant assemblage at the microhabitat level. Location Sayeret Shaked Park, the Negev desert (Israel). Results The nurse species examined, two shrubs and one large annual, had a negligible or even negative influence on annual above‐ground biomass production. Nonetheless, they increased functional diversity in terms of specific leaf area (SLA), maximum plant height (MPH), seed weight (SW), and reproductive ratio (RR) at the microhabitat level. Conclusions These findings reinforce the idea that, even if there is not a typical nurse syndrome related to enhanced plant performance, nurse plants might induce a portfolio effect on annual plant assemblages by promoting functional diversity in key functional traits associated to plant survival and reproduction under a set of different microhabitat conditions. Nurse shrubs and a large annual plant, even if they do not have any positive influence on biomass production, are shown to increase functional diversity (computed using direct measurements of specific leaf area [SLA], maximum plant height [PH], seed weight [SW], and reproductive ratio [RR]) of surrounding annual plant assemblages in the Negev Desert.