Concordance and Discordance: Variable Phylogeographic Outcomes in a Multi‐Species Symbiosis From the Tropical Western Atlantic
Benjamin M. Titus, Marymegan DalyABSTRACT
Aim
Comparative phylogeographic studies ask the question ‘do ecological communities co‐diversify?’ Symbioses generate a priori expectations for phylogeographic concordance, yet few empirical comparative phylogeographic studies use symbiotic communities to interrogate this question. Here we conduct a comparative phylogeographic study spanning the entire geographic ranges of six co‐occurring species that form a complex symbiosis on coral reefs in the Tropical Western Atlantic. We further test the hypothesis that similar demographic processes are responsible for structuring this symbiosis where members share common phylogeographic barriers, both spatially and temporally.
Location
Coral reefs in the Tropical Western Atlantic Ocean.
Taxa
Corkscrew sea anemone,
Methods
We collected > 1300 individuals from 13 localities and generated a phylogeographic dataset using mtDNA barcodes and double digest restriction site associated DNA sequencing (ddRADseq). We used genetic clustering analyses and phylogeographic concordance factors to identify shared barriers to dispersal. We conducted modelling in fastsimcoal2 to test the demographic processes structuring communities across shared phylogeographic barriers.
Results
We find that no symbionts are spatially, temporally, or demographically concordant with their host anemone. This indicates that symbiotic association has a minimal role in generating concordant phylogeographic histories for these taxa. However, some members of this system share phylogeographic barriers at the Mona Passage and Florida Straits. Where co‐occurring taxa do share phylogeographic barriers, modelling in fastsimcoal2 implicates similar demographic processes in generating concordant structure, yet on different timescales.
Main Conclusions
Taken together, our analyses highlight the variable evolutionary outcomes within a single multi‐level symbiosis—a complicated collection of phylogeographic histories where both concordance and discordance prevail.