Multidimensional competition of nematodes affects plastic traits in a beetle ecosystem

Area of Science:

• Evolutionary Biology
• Ecology
• Developmental Biology

Background:

• Resource competition is a significant driver of evolutionary adaptations, leading to novel polyphenisms (multiple phenotypes from a single genotype).
• Necromenic nematodes, such as Diplogastridae, inhabit decaying insect cadavers and compete for bacterial resources, making them ideal models for studying ecological interactions.
• Phenotypic plasticity, including mouth form and developmental pathways, plays a crucial role in nematode survival and fitness within these competitive micro-ecosystems.

Purpose of the Study:

• To investigate the impact of increased competition on the polyphenic strategies of necromenic nematodes.
• To examine how the addition of a third competing nematode species influences the behavioral and developmental responses of existing competitors.
• To understand the evolutionary significance of polyphenisms in mediating interspecific competition in short-lived ecosystems.

Main Methods:

• Utilized a model system involving the cockchafer Gymnogaster bupthalma, and necromenic nematodes Pristionchus mayeri, Acrostichus spp., and introduced Pristionchus pacificus.
• Observed and analyzed the mouth-form polyphenisms (bacterial-feeding vs. omnivorous predation) and developmental polyphenisms (direct development vs. dauer arrest).
• Experimentally manipulated the competitive environment by introducing a third nematode species to assess changes in competitive strategies.

Main Results:

• Pristionchus mayeri exhibited a faster response to increased competition by exiting the dauer stage and engaging in predation.
• Acrostichus spp. adopted a strategy of entering the dauer stage, delaying development until competitors dispersed.
• The addition of a third competitor significantly altered the competitive dynamics and polyphenic expression in the established two-species system.

Conclusions:

• Polyphenisms are critical for navigating complex competitive interactions in resource-limited environments.
• Nematode species display distinct adaptive strategies, such as rapid exploitation or strategic dormancy, in response to varying levels of interspecific competition.
• Short-lived experimental ecosystems provide valuable insights into the evolutionary role of phenotypic plasticity in mediating species interactions.