Phylogenetic Systematics of Sacoglossa, Including Solar-Powered Sea Slugs

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Our lab recently published a four-gene phylogenetic hypothesis for Sacoglossa, a clade of herbivorous sea slugs including two lineages of photosynthetic species that retain functional chloroplasts from ingested algal cytoplasm for periods ranging from days to months. We included 202 species in this phylogenetic tree, with six outgroup taxa (related species not belonging to Sacoglossa). Our primary goal for this initial study was to elucidate the effects that changes in larval development mode have had on lineage diversification over the evolutionary history of Sacoglossa. However, this project also resulted in the clearest picture to date of the relationships among species, genera, and higher taxonomic groups. Ongoing work has added a 5th gene and another 100 species, and is focused on determining whether all traditional genera, families, and superfamilies defined by morphology are monophyletic (valid groups in which all species are descended from one common ancestor). Our results to date reveal many genera and families are non-monophyletic, so systematic revision will be a major goal of continuing studies.

 

Click on the two phylogenies below for an expanded view. Horizontal arrows indicate upticks in diversification rate. Genera are indicated to the right of provisional or traditional species identifications. Support values are given above (Bayesian) and below (ML) branches; * = 1.0 or 100% support.

For details, see Krug et al. 2015, Systematic Biology 64: 983–999. For information on individual species or genera, see http://sacoglossa.myspecies.info/