What are the sympatric mechanisms for three species of terrestrial hermit crab (Coenobita rugosus, C. brevimanus, and C. cavipes) in coastal forests?

Chi-Chang Liu,Marinus L Otte,Wei-Ta Fang,Chia-Hsuan Hsu,Jui-Yu Chou

doi:10.1371/journal.pone.0207640

Abstract

Terrestrial hermit crabs play a significant role in coastal ecology. For example, as seed dispersers and debris scavengers in coastal forests, they accelerate the decomposition of organic substances. In the Indo-Pacific Ocean, Coenobita rugosus, C. brevimanus, and C. cavipes are the three most common species of terrestrial hermit crab. Because the mechanisms that contribute to the sympatry of these three species of crab have not been identified, this study investigated the three most likely explanations: niche differences, competition, and predation. The results showed that the three species displayed niche differences in terms of seasonal activity, habitat, utilization of shells, and food preference, suggesting that competition for resources is avoided. The habitat of terrestrial hermit crabs in Taiwan is closely associated with that of humans. Our study helps improve our understanding of the ecology of terrestrial hermit crabs and their conservation.

Highlights

Terrestrial hermit crabs are widely distributed in tropical and subtropical regions
We investigated the importance of different mechanisms that may explain the sympatry of the terrestrial hermit crabs, Coenobita rugosus, C. brevimanus, and C. cavipes, regarding (1) ecological niche
The same applied to C. rugosus and C. brevimanus, and again C. rugosus was significantly closer to the sea shore (χ2 = 1271.5, p < 0.001)

Summary

Introduction

Terrestrial hermit crabs are widely distributed in tropical and subtropical regions. They play major roles in ecosystems and substantially contribute to nutrient cycling and seed dispersal in coastal forests [1, 2]. We investigated the importance of different mechanisms that may explain the sympatry of the terrestrial hermit crabs, Coenobita rugosus, C. brevimanus, and C. cavipes, regarding (1) ecological niche. Different foraging behaviors or olfactory abilities are sufficient to cause ecological niche differences and ensure the joint survival of multiple species [11] They are scavengers and have seemingly unselective food choices, they exhibit clear preferences [3, 10, 12]. Several studies have shown that different species of hermit crabs will exhibit different preferences for shells as well [20, 23,24,25], which reduces competition for this resource. The aim of our study was to investigate the sympatric mechanisms for three species of terrestrial hermit crab (C. rugosus, C. brevimanus, and C. cavipes). We expected that differences between the species regarding seasonal activity, habitat preference, availability and type of shells, and food preferences would all to some extent contribute to the sympatry of these species

Materials and methods

2–1 Field surveys

2–2 Seasonal activity

2–3 Habitat

2–4 Shell preference

2–5 Food preference

Results and discussion 3–1 Seasonal activity

3–2 Niche differences for habitat

3–3 Niche differences for shell resource

Niche differences for food preference

Findings

Conclusion