Molecular and Morphological Diversity of Heterodesmus Brady and Its Phylogenetic Position within Cypridinidae (Ostracoda)

Sexual Signals Persist over Deep Time: Ancient Co-option of Bioluminescence for Courtship Displays in Cypridinid Ostracods

Although the diversity, beauty, and intricacy of sexually selected courtship displays command the attention of evolutionists, the longevity of these traits in deep time is poorly understood. Population-based theory suggests sexual selection could either lower or raise extinction risk, resulting in high or low persistence of lineages with sexually selected traits. Furthermore, empirical studies that directly estimate the longevity of sexually selected traits are uncommon. Sexually selected signals-including bioluminescent courtship-originated multiple times during evolution, allowing the empirical study of their longevity after careful phylogenetic and divergence time analyses. Here, we estimate the first transcriptome-based molecular phylogeny and divergence times of Cypridinidae. We report extreme longevity of bioluminescent courtship, a trait important in mate choice and probably under sexual selection. Our relaxed-clock estimates of divergence times coupled with stochastic character mapping show luminous courtship evolved only once in Cypridinidae-in a Sub-Tribe, we name Luxorina-at least 151 millions of years ago from cypridinid ancestors that used bioluminescence only in antipredator displays, defining a Tribe we name Luminini. This time-calibrated molecular phylogeny of cypridinids will serve as a foundation for integrative and comparative studies on the biochemistry, molecular evolution, courtship, diversification, and ecology of cypridinid bioluminescence. The persistence of luminous courtship for hundreds of millions of years suggests that sexual selection did not cause a rapid loss of associated traits, and that rates of speciation within the group exceeded extinction risk, which may contribute to the persistence of a diverse clade of signaling species. [Ancestral state reconstruction; Biodiversity; co-option; divergence time estimates; macroevolution; Ostracoda; phylogenomics; sexual selection.].

Diversification of the shell shape and size in Baikal Candonidae ostracods inferred from molecular phylogeny

Ostracod shells are used extensively in paleontology, but we know little about their evolution, especially in ancient lakes. Lake Baikal (LB) is the world's most important stronghold of Candonidae diversity. These crustaceans radiated here rapidly (12-5 Ma) and with an unprecedented morphological diversity. We reconstruct their molecular phylogeny with 46 species and two markers (18S and 16S rRNA), and use it to estimate the evolution of the shell shape and size with landmark-based geometric morphometrics (LBGM). High posterior probabilities support four major clades, which differ in node depth and morphospace clustering. After removing a significant allometry, the first three principal components (PCs) describe about 88% of total variability, suggesting a strong integration. Reconstructed ancestral shapes are similar for all four clades, indicating that diversification happened after colonization. Major evolutionary changes occurred from trapezoidal to elongated shapes. Sister species are separated in morphospace, by centroid size, or both, as well as by vertical and horizontal distributions in LB. Ostracod shell is a strongly integrated structure that exhibits high evolvability, with some extreme shapes, although mostly along the first PC. This is the first study that combines molecular phylogeny and LBGM for ostracods and for any LB group.

Four new Parasterope (Ostracoda, Myodocopina) from the Northwest Pacific and their phylogeny based on 16S rRNA

Parasterope Kornicker, 1975 is a marine ostracod genus with 49 species described so far, which makes it the most diverse representative of the subfamily Cylindroleberidinae, as well as the entire family Cylindroleberididae. Despite its global distribution no species are reported from South Korea. Three new species collected from the Korean coast of the Sea of Japan (Parasteropebusanensissp. nov., P.singulasp. nov., and P.sohisp. nov.), and one from the Japanese coast of the Pacific Ocean (P.sagamisp. nov.) are described. A taxonomic key to all named species from East Asia is provided. A phylogenetic tree is reconstructed based on partial 16S rRNA sequences of the four new species and other Cylindroleberidinae available from GenBank. Monophyly of Parasterope is supported by high posterior probabilities, but the phylogenetic analyses also indicate that some of the GenBank data attributed to this genus are probably misidentifications. A map of distribution and a checklist of all described Parasterope species are also provided.