Species discovery and description

1b. Species discovery and description

Using integrative approaches, we are committed to clarifying the boundaries of sacoglossan species, discovering unrecognized biodiversity in this group, and naming taxa so that scientists can properly communicate with each other. Our efforts combined data from DNA sequencing with characters from internal and external morphology, as well as reproductive and larval biology, plus host ecology. We have recently pioneered the use of truly integrative Bayesian analyses for marine invertebrates that delimit species using both gene sequence data and continuous morphological characters in one analysis; such approaches hold great promise for more objective evaluation of species hypotheses in soft-bodied animal groups.

Placida cremoniana complex. We described three new species in the colorful Placida cremoniana complex, including one species likely native to the Galapagos and other tropical eastern Pacific sites that recently colonized California's Channel Islands (P. brookae); this range expansion followed recent El Nino events and may have been facilitated by ongoing ocean warming. A second new species was collected from Hawaii, which we named after former

U.S. president Barack Obama to honor his efforts to reduce carbon emissions and mitigate climate change, and for expanding Papahanaumokuakea Marine National Monument in Hawaii. Two of the new species are named for divers to recognize the contributions made by photographers and naturalists who document and collect valuable specimens. (see McCarthy et al. 2017)

Left, P. barackobamai; Right top, P. kevinleei; bottom, P. brookae

family Oxynoidae

Using a Bayesian approach, we recently integrated multilocus genetic data with radular tooth characters to show that shelled genera Oxynoe (6 generally recognized species) and Lobiger (4 species) in fact contained 11 additional pseudocryptic species - that is, species unrecognized by current systematics, yet forming distinct genetic entities that are distinguishable morphologically. Quantitative analyses revealed differences among species in radular tooth characters, which alone were informative for delimiting species. Integrating molecular and trait data fully supported all species hypotheses, and highlighted a previously unappreciated degree of host specialization (or at least preference) among taxa in the green algal genus Caulerpa, which includes highly invasive species. We described seven new Oxynoe species based on external morphology, penial anatomy, radular characters and host ecology. (see Berriman et al., 2018; Krug et al., in press)

Elysia

This hyperdiverse genus contains over a third of described biodiversity in Sacoglossa, with 90 or more recognized species. Our first monographic revision in this genus focused on the Caribbean regional fauna after 15 years of collections and molecular species delimitation that included over 200 sequenced specimens per nominal species. We placed 72 species in a phylogenetic context using molecular data, and provided new data on penial anatomy and radular tooth morphology, larval biology, and host algal associations for as many species as possible, in reviewing all 27 described species from the Caribbean. We described six new Elysia species. Elysia taino is named for an indigenous people of the central and western Caribbean islands, where this sister species to E. papillosa is widely distributed; the two species are easily differentiated by their radular teeth but are externally indistinguishable and feed on the same host alga, Penicillus. Elysia buonoi is known from only one Bahamas island, and externally resembles its sister species E. zuleicae; both feed on Udotea, but can be differentiated by their penial anatomy. The species is named for Thomas Buono, the greatest seafood chef of all time and one of the world's great men who we miss dearly. Elysia christinae is part of the complex including all the above-named species, but eats a different alga (Rhipilia); it was named for my grandmother, named Christine together with my aunt. The large-bodied Caulerpa-feeders include E. zemi, named for a head marking that resembles the ceremonial objects of the Taino; and E. pawliki, named for marine chemical ecologist and colleague Joseph Pawlik, without whom initial studies on Caribbean sacoglossan diversity would not have been possible. (see Krug et al. 2016 part 1; Krug et al. 2016 part 2).