Battle of the borders: Is a range-extending fiddler crab affecting the spatial niche of a congener species?

Summary

Climate change is drastically altering environmental conditions and resource availability. Many organisms areshifting their distribution boundaries. Fiddler crabs, for instance, are important ecosystem engineers in coastalenvironments that have been extending their distribution range poleward. In this study, we evaluated the in-fluence of a range-extending species,Leptuca cumulanta, which has recently overlapped the distribution of theresident speciesLeptuca uruguayensis. Through a set offield and laboratory experiments, we characterised thedegree of territorial overlap betweenL.cumulantaandL. uruguayensisfrom the lower to upper intertidal zone in amangrove area. We also analysed whether the presence ofL. cumulantaprevents habitat choosiness or influencesagonistic behaviours inL.uruguayensisin territorialfights. We found that both species overlap territories at thesame level in the intertidal zone. However, we observed that both habitat choice and agonistic behaviours ofL.uruguayensiswere unresponsive to the presence ofL.cumulanta. The low interference between recent hetero-specific neighbours sharing the same space supports coexistence offiddler crabsL. uruguayensisandL. cumulantain the early stage of overlapping