Global distribution and richness of terrestrial mammals in tidal marshes

Abstract

Aim: Understanding the determinants of species distribution and richness is key to explaining global ecological patterns. We examined the current knowledge about terrestrial mammals in tidal marshes and evaluated whether species richness increased with the marsh surface area and/or with their proximity to the equator and whether species distribution ranges decreased with latitude. Location: Global. Methods: We reviewed the existing literature on terrestrial mammals in tidal marshes. We examined their ecological characteristics (e.g. habitat specialists, native or alien), predicted their variation in species richness and range size along latitude, and explored factors, such as surface area, underlying the global patterns found. Results: We found 962 records, describing 125 mammalian species using tidal marshes worldwide, also including several alien species. Most species (95%) were not marsh specialized, and some (18%) were of conservation concern. There were information gaps in South America, Africa, Australia and Asia, and a lack of information about mammalian ecological roles worldwide. We found that species richness increased with surface area, and showed a bimodal pattern peaked between 40° and 50° latitude in each hemisphere. We found no relationship between latitude and species range size. Main conclusions: Our worldwide findings revealed a broader range of tidal marshes inhabited by terrestrial mammals, and higher values of species richness than previously reported. The bimodal pattern of species richness was consistent with the species–area hypothesis, but it also suggested that further studies of species distribution in relation to historical and environmental factors will yield significant insights about variables driving richness in tidal marshes. Despite terrestrial mammal ubiquitous distribution in these ecosystems, there are considerable geographic gaps as regards knowledge about their functional importance and the impact of alien species on tidal marsh functioning. Consequently, extending our research efforts is key to planning the conservation of these coastal ecosystems.