Colony discrimination and competition in the eusocial trematode, Himasthla rhigedana

The California horn snail (Cerithideopsis californica) hosts a diverse community of trematode parasite species, yet these species rarely co-occur in the same host. Some trematodes in this community competitively exclude conspecifics and heterospecifics using a soldier caste. How these trematodes can distinguish colonymates from competitors is unknown. Here we examine patterns of colony discrimination in Himasthla rhigedana, a marsh-dwelling species of parasitic trematode that possesses a soldier caste in their intermediate snail hosts. Aggression assays pairing colonies against multiple opponents demonstrate that H. rhigedana distinguish between conspecific colonies, consistently directing more attacks towards colonies collected from a distant marsh. We demonstrate that conspecific interactions between colonies are predominantly symmetrical (both colonies attack during encounters), and that the likelihood of aggression is the same whether the attacker soldier is “sterile” (soldier redia..., Methodology can be found in the corresponding pre-printed manuscript., , # Colony discrimination and competition in the eusocial trematode, *Himasthla rhigedana*

ONLINE RESOURCE 1 (.zip) ##################################################

*Decription:* A zip file of videos (.wmv) of cercariae collected from each colony used in our manuscript. Cercariae are how morphological species claims are made for our trematode species, so we include these videos as reference for how we identified each species used in our experiments. These videos comply with the CC0 license waiver required by Dryad for publication, and we allow any readers to make their own morphospecies claims as desired from these videos. Within the zip file is two folders, one for each assay (ABC, ABX). Each file name indicates the colony the cercariae were collected from. For example, \"A1_Cercs_1.wmv\" in the ABC folder shows the cercariae from colony A1 in the ABC assays.

ONLINE RESOURCE 2 (.txt) ##################################################

*Description:* A text file showing the final ali...