Functional diversity exhibits a diverse relationship with area, even a decreasing one

TLDR

The relationship between species richness and area is a well‑established ecological law, yet few studies have examined whether a similar pattern holds for trait‑based functional diversity (FDAR). The study aims to examine the Functional Diversity‑Area Relationship by constructing species and functional diversity accumulation curves. Using plant diversity data from nested plots (1–128 m²) on the volcanic islands of Santorini Archipelagos, Greece, the authors calculated six multidimensional FD indices from 26 traits. Four FDAR typologies emerged: a strong positive relationship for range indices, a negative correlation for evenness indices, no clear pattern for similarity indices, and idiosyncratic patterns for divergence, and as area increases, trait range expands but abundance does not, causing certain traits to dominate and functional reliance to shift toward central or peripheral trait space.

Abstract

Abstract The relationship between species richness and area is one of the few well-established laws in ecology, and one might expect a similar relationship with functional diversity (FD). However, only a few studies investigate the relationship between trait-based FD and area, the Functional Diversity - Area Relationship (FDAR). To examine FDAR, we constructed the species accumulation curve and the corresponding FD curve. We used plant diversity data from nested plots (1–128 m 2 ), recorded on the Volcanic islands of Santorini Archipelagos, Greece. Six multidimensional FD indices were calculated using 26 traits. We identified a typology of FDARs depending on the facet of FD analyzed: (A) strongly positive for indices quantifying the range of functional traits in the community, (B) negative correlation for indices quantifying the evenness in the distribution of abundance in the trait space, (C) no clear pattern for indices reflecting the functional similarity of species and (D) idiosyncratic patterns with area for functional divergence. As area increases, the range of traits observed in the community increases, but the abundance of traits does not increase proportionally and some traits become dominant, implying a reliance on some functions that may be located in either the center or the periphery of the trait space.