Oral Presentation Freshwater Sciences 2023

Role of pool geomorphology and rock traits on tropical stream insect oviposition patterns of Puerto Rico (#196)

Mariely Vega Gómez 1 , Alonso Ramírez 1
  1. Department of Applied Ecology, North Carolina State University, Raleigh, N.C., U.S.

Oviposition by aquatic insects is a process that is important for population and assemblage dynamics. For the Caribbean region, climate change projections indicate that geomorphology-altering disturbances are expected to become more intense or frequent. Our objective was to understand the role that geomorphological variables and rock traits play in oviposition patterns on small montane streams at El Yunque National Forest, Puerto Rico. We expected to find 1) a greater number of egg masses on exposed rocks given the greater visible area for females to land and reduced drowning or predation risks. We also expected to find a greater number of egg masses in smaller pools because they were shallower representing a lower predation risk. We placed 28 boulder-sized rocks (approximately the size of a fist) along six small and large pools in sections where the rocks would be either submerged or exposed. We monitored the abundance, morphotype, and location of egg masses for four weeks. During the mid-point, the rocks were relocated within each pool into opposite water level conditions. We recorded rock traits such as color, texture, visible area, and depth in the pools. We found that oviposition seems to occur on specific rocks, as over half the rocks with masses before the switch also had masses after relocation. However, none of the characteristics examined here explained patterns in the abundance of masses, their morphotypes, or their location on the substrates. We found that rock placement in pools, but not pool size, had a significant effect on the cumulative abundance of masses. Under the threat of a projected increase in disturbance frequency and intensity in the Caribbean, it is important to assess how the structure of the aquatic biota might change as a response to events that alter the geomorphology and substrate composition of stream environments.