Resource use by and trophic variability of Armases cinereum (Crustacea, Brachyura) across human-impacted mangrove transition zones

Abstract

In Florida, resource use patterns by Armases cinereum ( Armases ), a highly abundant crab in coastal habitats, may serve as important indicators of habitat condition. Here we investigated feeding patterns of Armases in coastal palm scrub forest to intertidal mangrove forest transition zones (transitions) as well as the relationship between habitat disturbance and Armases’ trophic position across three pairs of geographically separated populations in Tampa FL, USA. Each pair of sites represented an unmodified “natural” location as well as a “disturbed” location lacking upland terrestrial palm scrub forested habitat. Laboratory experiments established a baseline understanding of feeding preference of Armases offered strictly mangrove material as well as sources abundant at the transition. In-situ feeding behavior was examined using MixSIAR mixing models with δ 13 C and δ 15 N stable isotope tracers. Armases showed a strong preference for consuming partially-decomposed mangrove material from Avicennia germinans and an equally strong preference for Iva frutescens . Armases also displayed predatory behavior under laboratory conditions, confirming omnivory in the presence of mangrove material. Stable isotopes revealed a pattern of elevated trophic position of Armases in disturbed habitats over paired natural locations. Diet reconstruction provided coarse resolution of in-situ feeding and results show high spatial variation: in natural habitats, Armases appears to rely heavily upon upland plant material compared to disturbed habitats where it may consume more animal prey. Combined, these findings support that Armases trophic position and diet may indicate habitat quality in mangrove transitions in the southeastern United States.

Metabolic rates in the squareback marsh crab Armases cinereum

“…Given the widespread distribution and high abundance of this species, understanding its energy budget could aid in understanding the overall energy flow in upper saltmarsh ecosystems, and its quantitative role as a vector of spatial subsidies within this system (Hübneṙ et al, 2015). The majority of data needed for a bioenergetics model for A. cinereum are now available (consumption: Ho & Pennings, 2008;Hübneṙ et al, 2015;Kiskaddon, 2016;Kiskaddon et al, 2019;growth: Buck et al, 2003;Zimmer et al, 2004;reproduction: Figueiredo et al, 2008, respiration: this study). Additional data needs for constructing such a model include estimates of assimilation and of the energy content of eggs.…”

“…Additional data needs for constructing such a model include estimates of assimilation and of the energy content of eggs. Finally, while previous research demonstrates the feeding patterns of A. cinereum (Ho & Pennings, 2008;Hübneṙ et al, 2015;Kiskaddon, 2016;Kiskaddon et al, 2019), the amount of food consumed by this species has yet to be quantified.…”

Survival of lizard eggs varies with microhabitat in the presence of an invertebrate nest predator

“…Given the abundance of marsh crabs in the southeastern United States (Teal 1958;Seiple 1979;Buck et al 2003) and across our study islands, depredation rates of anole eggs by these predators may also be relatively high. Indeed, the marsh crab is considered a critical component of terrestrial food webs in coastal habitat (Ho and Pennings 2008), and although these scavengers forage primarily on partially-decomposing plant matter, they also readily consume animal prey when available (Buck et al 2003;Kiskaddon et al 2019). Consequently, marsh crabs may be a major source of lizard egg mortality where they coexist and also impose significant pressure on nest site choices of female anoles.…”

Potential impact of land‐use change on habitat quality in the distribution range of crocodile lizards in China

“…Land use types, intensities and patterns alter the condition of natural resources and thus affect the survival and reproduction of wildlife (Dai et al, 2019 ; Whittington et al, 2019 ). Biogeochemical cycles and habitat quality for animals and plants are changed because of increased human disturbance (Abbott et al, 2019 ; Kiskaddon et al, 2019 ; Lin et al, 2020 ; Powers & Jetz, 2019 ). And changes in these cycling processes may have adverse effects on the structure and function of ecosystems.…”