Why parasite communities are uneven? The case study of Microphallus

ALDA P.; BONEL N.

La Habana

Congreso; XXVI Congreso de la Federación Latinoamericana de Parasitología (FLAP); 2022

IPK

Community ecologists have long pondered why a few species are common whereas many are rare. Three causes could explain a skewed species abundance. First, each species can be adapted to specific sets of conditions and species abundances can follow from skewed niche opportunities in the environment. Second, competition among species can favor dominant species if species niches overlap, resulting also in a skewed species abundance. Finally, different recruitment rates among species could also shape species abundances. The hypotheses for explaining species abundance distributions can be tested using parasite communities because host populations are natural replicates that define a community. We estimate the extent to which niche differences, species interactions, and recruitment variability structure a highly skewed trematode component community in a snail host. We collected and dissected the snail Heleobia australis (Cochliopidae) over four seasons from three distinct habitats from the intertidal area of the Bahía Blanca estuary, Argentina. We found that the most abundant trematode species, Microphallus simillimus, is a weak competitor, but has life-history traits and strategies associated with higher colonization ability that could increase its probability of invading the host first, allowing it to preempt the rare species. Rather than segregate by habitat, trematode species aggregated in pans during the summer where dominant trematode species often excluded subordinate ones. Despite losses to competition, and a lack of niche partitioning, M. simillimus ruled this species-rich trematode guild through strong recruitment and (potentially) preemption. Therefore, extremely skewed species abundance distributions, like this one, can derive from extremely skewed colonization abilities.