Assessing the ecological vulnerability of Western Atlantic marine benthic gastropods

Assessing the extinction risk in marine invertebrates poses serious challenges to conservation biology, due to the magnitude of marine biodiversity, the inaccessibility of most of the marine realm, and the lack of appropriate data on population dynamics and ecology for most species. However, simple life history traits have a huge potential for preliminary screening criteria for assessing large numbers of species whose status is harsh or impossible to evaluate. Body size and trophic position could be strong predictors of extinction risk providing a general framework for the assessment of species vulnerability. We analyzed the Body Size-Trophic Position (BS-TP) relationship along 1,067 genera representing 4,256 nominal species of western Atlantic benthic gastropods. We found that a carnivore diet characterizes 67% of the genera and that, supporting theoretical predictions, the probability of being carnivores as a function of size showed a unimodal trend. For species with adult body sizes larger than 5 cm, a negative association between trophic position and body size was detected. This result points to an energetic restriction for the viability of large species, implying that organisms placed near the BS-TP boundary are extremely vulnerable to environmental changes. With this result, 109 genera from 42 families of carnivore gastropods and 33 genera from 19 families of herbivore gastropods that may be more vulnerable from the analyzed perspective were identified and ranked. Supporting these results, while the most vulnerable genera are not represented in global IUCN assessments, all our ‘top 10’ vulnerable families are being considered in National or Regional Red Lists. Prior to conducting regional or global conservation assessments for invertebrate taxa, screening methods should be strongly considered.