Gene flow throughout the evolutionary history of a colour polymorphic and generalist clownfish.

Even seemingly homogeneous on the surface, the oceans display high environmental heterogeneity across space and time. Indeed, different soft barriers structure the marine environment, which offers an appealing opportunity to study various evolutionary processes such as population differentiation and speciation. Here, we focus on Amphiprion clarkii (Actinopterygii; Perciformes), the most widespread of clownfishes that exhibits the highest colour polymorphism. Clownfishes can only disperse during a short pelagic larval phase before their sedentary adult lifestyle, which might limit connectivity among populations, thus facilitating speciation events. Consequently, the taxonomic status of A. clarkii has been under debate. We used whole-genome resequencing data of 67 A. clarkii specimens spread across the Indian and Pacific Oceans to characterize the species' population structure, demographic history and colour polymorphism. We found that A. clarkii spread from the Indo-Pacific Ocean to the Pacific and Indian Oceans following a stepping-stone dispersal and that gene flow was pervasive throughout its demographic history. Interestingly, colour patterns differed noticeably among the Indonesian populations and the two populations at the extreme of the sampling distribution (i.e. Maldives and New Caledonia), which exhibited more comparable colour patterns despite their geographic and genetic distances. Our study emphasizes how whole-genome studies can uncover the intricate evolutionary past of wide-ranging species with diverse phenotypes, shedding light on the complex nature of the species concept paradigm.

Recurrent gene flow events occurred during the diversification of clownfishes of the skunk complex.

Clownfish (subfamily Amphiprioninae) are an iconic group of coral reef fish that evolved a mutualistic interaction with sea anemones, which triggered the adaptive radiation of the clade. Within clownfishes, the "skunk complex" is particularly interesting. Besides ecological speciation, interspecific gene flow and hybrid speciation are thought to have shaped the evolution of the group. We investigated the mechanisms characterizing the diversification of this complex. By taking advantage of their disjunct geographical distribution, we obtained whole-genome data of sympatric and allopatric populations of the three main species of the complex (Amphiprion akallopisos, A. perideraion and A. sandaracinos). We examined population structure, genomic divergence and introgression signals and performed demographic modelling to identify the most realistic diversification scenario. We excluded scenarios of strict isolation or hybrid origin of A. sandaracinos. We discovered moderate gene flow from A. perideraion to the ancestor of A. akallopisos + A. sandaracinos and weak gene flow between the species in the Indo-Australian Archipelago throughout the diversification of the group. We identified introgressed regions in A. sandaracinos and detected in A. perideraion two large regions of high divergence from the two other species. While we found that gene flow has occurred throughout the species' diversification, we also observed that recent admixture was less pervasive than initially thought, suggesting a role of host repartition or behavioural barriers in maintaining the genetic identity of the species in sympatry.

Lessons learned from the conduct of a multisite cluster randomized practical trial of decision aids in rural and suburban primary care practices.

BACKGROUND: The decision aids for diabetes (DAD) trial explored the feasibility of testing the effectiveness of decision aids (DAs) about coronary prevention and diabetes medications in community-based primary care practices, including rural clinics that care for patients with type 2 diabetes. METHODS: As originally designed, we invited clinicians in eight practices to participate in the trial, reviewed the patient panel of clinicians who accepted our invitation for potentially eligible patients, and contacted these patients by phone, enrolling those who accepted our invitation. As enrollment failed to meet targets, we recruited four new practices. After discussing the study with the clinicians and receiving their support, we reviewed all clinic panels for potentially eligible patients. Clinicians were approached to confirm participation and patient eligibility, and patients were approached before their visit to provide written informed consent. This in-clinic approach required study coordinators to travel and stay longer at the clinics as well as to screen more patient records for eligibility. The in-clinic approach was associated with better recruitment rates, lower patient retention and outcome completion rates, and a better intervention effect. RESULTS: We drew four lessons: 1) difficulties identifying potentially eligible patients threaten the viability of practical trials of DAs; 2) to improve the recruitment yield, recruit clinicians and patients for the study at the clinic, just before their visit; 3) approaches that improve recruitment may be associated with reduced retention and survey response; and 4) procedures that involve working closely with the practice may improve recruitment and may also affect the quality of the implementation of the interventions. CONCLUSION: Success in practice-based trials in usual primary care including rural clinics may require the smallest possible research footprint on the practice while implementing a streamlined protocol favoring in-clinic, in-person interactions with clinicians and patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT01029288.