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Accurate species delimitation is crucial to understanding biodiversity. In the northern Gulf of Mexico, recent genetic evidence has suggested that the tricolor Luidia lawrencei is not a species distinct from the gray Luidia clathrata. We collected Luidia specimens from Apalachee Bay, Florida, and morphologically identified 11 as L. clathrata and 16 as L. lawrencei. We sequenced 1074 bp of the cytochrome c oxidase subunit I (COI) and found ~14% divergence between L. clathrata and L. lawrencei , suggesting two distinct species (within-species divergence was <1%). Two specimens were phenotypically L. lawrencei (i.e. , tricolor morph) but mitochondrially were L. clathrata. Our findings lend support to maintaining L. clathrata and L. lawrencei as distinct species. However, the species boundary between these two taxa may be porous, and ongoing hybridization may occur when the two species are found in sympatry. Future work with nuclear markers is warranted to determine the frequency of hybridization and the extent of introgression. Clarifying the genetic relationship between these species will provide a baseline for assessing ongoing changes in connectivity of these two highly abundant sea stars in the rapidly warming northern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Ecological and evolutionary processes differ depending on how genetic diversity is organized in space. For clonal organisms, the organization of both genetic and genotypic diversity can influence the fitness effects of competition, the mating system, and reproductive mode, which are key drivers of life cycle evolution. Understanding how individual reproductive behavior contributes to population genetic structure is essential for disentangling these forces, particularly in species with complex and plastic life cycles. The widespread sea anemone, Diadumene lineata , exhibits temperature-dependent fission, which contributes to predictable variation in clonal rate along the Atlantic coast of the United States, part of its non-native range. Because warmer conditions lead to higher rates of clonality, we expected to find lower genotypic and genetic diversity in lower versus higher latitude populations. We developed primers for 11 microsatellite loci and genotyped 207 anemones collected from 8 sites ranging from Florida to Massachusetts. We found clonal influence at all sites, and as predicted, the largest clones were found at lower latitude sites. We also found genetic signatures of sex in the parts of the range where gametogenesis is most common. Evidence of sex outside the native range is novel for this species and provides insights into the dynamics of this successful invader. Our findings also illustrate challenges that partially clonal taxa pose for eco-evolutionary studies, such as difficulty sampling statistically robust numbers of genets and interpretating common population genetic metrics. For example, we found high among-locus variation in F IS , which makes the meaning of mean multilocus F IS unclear. [ABSTRACT FROM AUTHOR]