Intraspecific functional variability associated to mangrove forest zonation in West-Central Mexico

Abstract

Functional diversity and the contribution of functional traits in mangrove ecosystems dynamics in western México remain unknown. In this study, we assessed intraspecific trait variation in three different mangrove zones. We developed and tested the following hypothesis: i. mangrove species vary along trait axes associated with plant size and leaf economics. ii. there is intraspecific trait variation (ITV) in leaf traits related to economic aspects of plant function among mangrove zones. iii. the presence of functional variation in plant traits among mangrove zones is related to physicochemical ground-water gradients. We used 65 permanent plots, distributed across three contrasting mangrove zones to assess morphological functional traits: leaf area, specific leaf area (SLA), leaf dry-matter content (LDMC), tree height (H) and wood density; salinity, dissolved oxygen, pH and temperature were recorded in each plot. Principal Component Analysis (PCA) examined how mangrove and mangrove-associated species were assembled in the functional trait space; General Linear Models (GLM) to compare mean trait values for each species among mangrove zones and Redundancy Analysis (RDA) to identify the interstitial water variables explaining functional composition. Laguncularia racemosa and Rhizophora mangle were mainly explained by SLA, LDMC and H; both species were associated to a bigger tree height, great leaf dry matter content, and small SLA values. GLM suggested ITV among mangrove zones with spatial patterns related to interstitial water variables. Our findings suggested mangrove species exhibited significant ITV mainly in SLA and H; salinity and pH were relevant to the functional ecology in mangrove ecosystems.