Spatial and seasonal taxonomic patterns in moth communities of the central Congo peatlands.

Abstract

Tropical insect communities are highly diverse but understudied, limiting understanding of tropical forest ecosystem functioning. This is especially true of the swamp forests of the central Congo peatlands, where peat occurs beneath two widespread forest types dominated by either hardwood trees or Raphia laurentii palms. Here, we describe taxonomic patterns in moth community composition, vertical stratification and seasonality in these two peat swamp forest types and the nearby terra firme forest. From 16 636 specimens, we identified 1110 species/morphospecies. Both swamp forest communities were distinctive and relatively species-poor: the palm swamp supported an estimated 637 species (46-52% of nearby terra firme forest), while the hardwood swamp supported an estimated 828 species (56-67%). Major taxonomic associations for each habitat suggest host plant availability shapes species distributions. Plant defences in the nutrient-limited swamps may further suppress moth abundance. Seasonal patterns of abundance and richness in the swamp forests diverge from the terra firme forest, decreasing rather than increasing in the wet season. This probably reflects different seasonal plant growth patterns in waterlogged ecosystems. Vertical stratification was most pronounced in the palm swamp, indicating particularly inhospitable understory conditions. Our results reveal that distinct ecological pressures shape swamp forest insect communities, highlighting general differences in insect herbivore-mediated ecosystem functioning. A French translation of this abstract is available in the supplementary material. This article is part of the discussion meeting issue 'African tropical peatlands: function, value and vulnerability'.