Coming out of your shell or crawling back in: multiple interphylum host switching events within a clade of bivalve- and ascidian-associated shrimps (Caridea: Palaemonidae)

Abstract Marine symbiotic Palaemonidae, comprising over 600 species, live in association with marine invertebrates of different phyla, like Cnidaria, Echinodermata, Mollusca, Porifera, and Tunicata. A phylogenetic study is performed on a clade bivalve- ascidian-associated endosymbiotic shrimp species (Caridea: Palaemonidae), using morphological molecular data. Total Evidence approach used order to include all currently known ingroup an evolutionary framework. Ancestral state reconstruction analyses are identify host-switching events ancestral ranges. The clade, including Ascidonia, Conchodytes, Dactylonia, Odontonia , Pontonia various smaller genera, recovered as monophyletic, host state. At least six interphylum switches tentatively identified, members Notopontonia switching back ascidian affiliation after the switch related from ascidian- bivalve host. Ascidonia was have ancestor East Pacific/Atlantic distribution. other studied genera remained original Indo-West Pacific range. We hypothesize that similar internal environments hosts phyla will function hot spots for lineages symbionts.