Seasonal flooding decreases fruit‐feeding butterfly species dominance and increases spatial turnover in floodplain forests of central Amazonia

Abstract

The seasonal flood pulse in Amazonia can be considered a primary driver of community structure in floodplain environments. Although this natural periodic disturbance is part of the landscape dynamics, the seasonal inundation presents a considerable challenge to organisms that inhabit floodplain forests. The present study investigated the effect of seasonal flooding on fruit‐feeding butterfly assemblages in different forest types and strata in central Amazonia. We sampled fruit‐feeding butterflies in the canopy and the understory using baited traps in adjacent upland (unflooded forests—terra firme), white and blackwater floodplain forests (várzea and igapó, respectively) during the low‐ and high‐water seasons. Butterfly abundance decreased in the high‐water season, especially of dominant species in várzea, but the number of species was similar between seasons in the three forest types. Species composition differed between strata in all forest types. However, the flood pulse only affected butterfly assemblages in várzea forest. The β‐diversity components also differed only in várzea. Species replacement (turnover) dominated the spatial β‐diversity in igapó and terra firme in both seasons and várzea in the high‐water season. Nonetheless, nestedness was relatively higher in várzea forests during the low‐water season, mainly due to the effect of dominant species. These results emphasize the importance of seasonal flooding to structure butterfly assemblages in floodplain forests and reveal the idiosyncrasy of butterfly community responses to flooding in different forest types. Our results also suggest that any major and rapid changes to the hydrological regime could severely affect floodplain communities adapted to this natural seasonal hydrological cycle, threatening the existence of these unique environments.

Butterfly Assemblages Differ among Vegetation Types in Southern Amazonia

“…(Euphorbiaceae) in a floodplain forest at the Teles Pires river, not far from the Cristalino Lodge [94]. Both this and previous studies have found satyr species to be indicators of or particularly common in floodplain forests, probably because these butterflies feed on fast-growing grasses that occur in such forests during the dry season [36][37][38]. Finally, it is interesting to note that the genus Calycopis belongs to a group of detritivorous Lycaenidae, whose larvae are capable of feeding on dead leaves on the ground [95][96][97].…”

“…Butterfly assemblages have been shown to differ between floodplain and terra firme forests in Amazonia, with the flooding acting as an environmental filter [36][37][38]. Contrary to várzea forests, which receive nutrient input from the inundation by muddy water and therefore are highly productive, igapó forests are flooded by poor, acidic black-waters, and are comparatively species-poor and unproductive [91][92][93].…”

“…The existence of this variety of vegetation types is one of the reasons behind Amazonia's great diversity, and this vegetation diversity has been shown to affect the assemblages of several animal taxa, including anurans [31], bats [32], primates [33], and birds [34,35]. Recent studies regarding butterflies have found different assemblages between terra firme and floodplain forests in Central Amazonia [36][37][38], and taxonomic and functional responses to an environmental gradient between terra firme and white-sand habitats in Northern Amazonia [39]. Butterflies are considered an especially good model to test assemblage associations to environmental characteristics, since they are a relatively well-known group of invertebrates, easy to collect, and many are largely dependent on specific host plants and habitats [40][41][42][43].…”