Abstract
Competition is rampant across kingdoms, arising over potential mates, food resources, and space availability. When faced with opponents, phenotypic plasticity proffers organisms indispensable advantageous strategies to outcompete rivals. This tactic is especially crucial on decaying insect hosts as myriad microbes and numerous nematodes struggle to establish thriving populations and ensure resource availability for future generations. Scarab beetles and their associated nematode symbionts on La Réunion Island have provided exceptional systems to study complicated cross-phylum interactions in soil, and recently we have identified a previously unexplored beetle host, Gymnogaster bupthalma, to be reliably co-infested with diplogastrids Pristionchus mayeri and Acrostichus spp. These nematodes maintain the capacity to plastically respond to environmental conditions by developing disparate mouth forms, a strict bacterial-feeding morph or an omnivorous morph that enables predation on other nematodes. In addition, under stressful settings these worms can enter an arrested development stage called dauer, non-feeding dispersal larvae that resume development into reproducing adults when conditions improve. By investigating this beetle-nematode system in a natural context, we uncovered a novel Pristionchus strategy, wherein dauer dispersal from the carcass is gradual and a reproducing population is sustained. Remarkably, usually preferential-bacterial morph P. mayeri develop as predators in populations dense with competitors.
Highlights
Competition is rampant across kingdoms, arising over potential mates, food resources, and space availability
Time of worm emergence from the carcasses varied among the time points: at t = 0, decapitated carcasses were immediately plated on nematode growth medium (NGM) agar, and nematodes emerged from 1 to 2 weeks after
At earlier time points (t = 0 through t = 2 weeks), in co-infested carcasses, Acrostichus was more prevalent in numbers of worms than P. mayeri, but the two equalized after 1 month on the carcasses
Summary
Competition is rampant across kingdoms, arising over potential mates, food resources, and space availability. Phenotypic plasticity proffers organisms indispensable advantageous strategies to outcompete rivals This tactic is especially crucial on decaying insect hosts as myriad microbes and numerous nematodes struggle to establish thriving populations and ensure resource availability for future generations. Scarab beetles and their associated nematode symbionts on La Réunion Island have provided exceptional systems to study complicated crossphylum interactions in soil, and recently we have identified a previously unexplored beetle host, Gymnogaster bupthalma, to be reliably co-infested with diplogastrids Pristionchus mayeri and Acrostichus spp. Named “infective juvenile” (IJ) in pathogenic worms and “dauer” in others, this alternative developmental pathway is often the dispersal stage; intraspecific density can result in continued dauer persistence (Sommer and Ogawa, 2011; Nermut’ et al, 2012; Artyukhin et al, 2013) and on crowded insect cadavers, worms enter IJ when food has been depleted in search of a new host (Koppenhöfer et al, 1997; Rolston et al, 2006)
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