We studied monogenean communities of 11 populations of Astyanax aeneus (Günther) separated
by small geographical distances along 60 km of the Lacantún river in Chiapas, Mexico,
in February and August 2012. We found 12 monogenean taxa. Amongst these, five species
specialist for Astyanax were widely distributed regionally, constituting 90% of the
total collected monogeneans, with one of these species dominating most component communities.
The high similarities in terms of composition between the component communities (SJaccard > 60%)
as well as in terms of the abundance and composition between infracommunities (SBray
Curtis > 40%), provide empirical evidence that transmission, both between hosts at
the same location and between component communities, is high and effective. No resemblance
pattern was detected between locations in terms of their spatial distribution. The
composition of these communities was spatially and temporally consistent over the
two very different weather periods sampled. These communities were not saturated.
Our analysis suggests that the potential richness of the infracommunities is proportional
to the number of monogenean species available in the component community. We found
aggregation in the populations and between monogenean species. Intraspecific aggregation
is density dependent, suggesting that intraspecific competition for space is not a
limiting factor for the development of the population. We evaluated the associations
for each species pair and detected 77% negative interactions (134/177 associations),
suggesting that interspecific competition plays an important role in shaping these
communities. The negative correlations of abundance between pairs of species contributes
to confirmation of competition. Intraspecific aggregation increased relative to interspecific
aggregation with richness in the component community, facilitating coexistence of
the species. Our results suggest that these are interactive communities, where monogeneans
disperse efficiently from a common source, colonize patches (hosts) together, and
compete with other species even at low population densities. Finally, the coexistence
of these species is favored by the unpredictable recruitment and aggregated use of
fragmented resources.