To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
It is unclear what session frequency is most effective in cognitive–behavioural therapy (CBT) and interpersonal psychotherapy (IPT) for depression.
Compare the effects of once weekly and twice weekly sessions of CBT and IPT for depression.
We conducted a multicentre randomised trial from November 2014 through December 2017. We recruited 200 adults with depression across nine specialised mental health centres in the Netherlands. This study used a 2 × 2 factorial design, randomising patients to once or twice weekly sessions of CBT or IPT over 16–24 weeks, up to a maximum of 20 sessions. Main outcome measures were depression severity, measured with the Beck Depression Inventory-II at baseline, before session 1, and 2 weeks, 1, 2, 3, 4, 5 and 6 months after start of the intervention. Intention-to-treat analyses were conducted.
Compared with patients who received weekly sessions, patients who received twice weekly sessions showed a statistically significant decrease in depressive symptoms (estimated mean difference between weekly and twice weekly sessions at month 6: 3.85 points, difference in effect size d = 0.55), lower attrition rates (n = 16 compared with n = 32) and an increased rate of response (hazard ratio 1.48, 95% CI 1.00–2.18).
In clinical practice settings, delivery of twice weekly sessions of CBT and IPT for depression is a way to improve depression treatment outcomes.
Evaluate the relative bioavailability of single-dose amphetamine extended-release tablet (AMPH ER TAB) 20 mg, swallowed whole or chewed, and amphetamine extended-release oral suspension (AMPH EROS) 2.5 mg/mL; evaluate food effect on AMPH ER TAB.
Healthy volunteers (18–55 years) were randomized to 1 dose of AMPH ER TAB 20 mg swallowed (fasted), chewed (fed/fasted), or 20 mg AMPH EROS (fasted). A crossover study design was used. Plasma samples were collected each period predose and at time points to 60 hours postdose. d- and l-amphetamine were measured and pharmacokinetic (PK) was calculated (90% confidence intervals of the ratios of the plasma levels) for AUC0-t, AUC0-∞, and Cmax. Comparative relative bioavailability between formulations was determined when ratios were within 80% and 125%. Safety was also assessed.
Thirty-two subjects completed the study. AMPH ER TAB swallowed versus AMPH EROS (fasted): for d- and l-amphetamine, the total and peak exposure was similar: d: AUC0-t: 100.68% to 108.08%, AUC0-∞: 101.47% to 109.52%, Cmax: 98.10% to 103.17%; l: AUC0-t: 100.31% to 108.57%, AUC0-∞: 101.27% to 111.09%, Cmax: 98.2% to 103.37%. For d- and l-amphetamine when the tablet is swallowed whole, Tmax was 5.00 hours (with a range of 2.00–9.00 hours). AMPH ER TAB chewed versus AMPH EROS (fasted): for d- and l-amphetamine, the total and peak exposure was similar: d: AUC0-t: 99.23% to 106.62%, AUC0-∞: 99.58% to 107.59%, Cmax: 99.91% to 105.14%; l: AUC0-t: 98.16% to 106.35%, AUC0-∞: 98.44% to 108.11%, Cmax: 99.53% to 104.75%. For d- and l-amphetamine when the tablet has been chewed, Tmax was 5.00 hours (with a range of 3.00-7.00 hours). PK results were similar for patients in the fasted and fed groups, indicative of no presence of food effect. No serious adverse events (AEs) were reported, overall AE profiles between the tablet and oral suspension were comparable without any unanticipated safety concerns.
Single doses of AMPH ER TAB for both d- and l-amphetamine demonstrated comparable bioavailability to a 20 mg dose of AMPH EROS, 2.5 mg/mL under fasted conditions when chewed and swallowed whole, and demonstrated equivalent peak and overall exposure without apparent food effect. AMPH ER TAB was well-tolerated and consistent with adverse events noted in other amphetamine formulations.
Depression is a leading cause of healthcare use and risk for suicide among US military personnel. Depression is not well characterised over the shipboard deployment cycle, and personnel undergo less screening than with land-based deployments, making early identification less likely.
To determine the demographic and behavioural risk factors associated with screening positive for risk of depression (ROD) across the shipboard deployment cycle.
Active-duty ship assigned personnel completed an anonymous assessment using the Center for Epidemiologic Studies Depression Scale (CES-D) in the year prior to deployment, during deployment and in the months following deployment. Longitudinal models were used to determine risk factors.
In total, 598 people were included in the analysis. Over 50% of the study population screened positive for ROD (CES-D score ≥16) and over 25% screened positive for risk of major depressive disorder (CES-D score ≥22) at all time points. Lower age, female gender, alcohol use, stress and prior mental health diagnoses were all associated with greater odds of screening positive for ROD in multivariable models.
Although the risk factors associated with screening positive for ROD are similar to those in other military and civilian populations, the proportion screening positive exceeds previously reported prevalence. This suggests that shipboard deployment or factors associated with shipboard deployment may present particular stressors or increase the likelihood of depressive symptoms.
Declaration of interest
The authors are military service members (or employees of the US Government). This work was prepared as part of the authors' official duties. Title 17, U.S.C. §105 provides the ‘Copyright protection under this title is not available for any work of the United States Government.’ Title 17, USC, §101 defines a US Government work as work prepared by a military service member or employee of the US Government as part of that person's official duties. The views expressed in this research are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of the Army, Department of the Air Force, Department of Veterans Affairs, Department of Defense, or the US Government. Approved for public release; distribution unlimited. Material has been reviewed by the Walter Reed Army Institute of Research. There is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the authors, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense.
Inadequate protein quality may be a risk factor for poor growth. To examine the effect of a macronutrient–micronutrient supplement KOKO Plus (KP), provided to infants from 6 to 18 months of age, on linear growth, a single-blind cluster-randomised study was implemented in Ghana. A total of thirty-eight communities were randomly allocated to receive KP (fourteen communities, n 322), a micronutrient powder (MN, thirteen communities, n 329) and nutrition education (NE, eleven communities, n 319). A comparison group was followed cross-sectionally (n 303). Supplement delivery and morbidity were measured weekly and anthropometry monthly. NE education was provided monthly. Baseline, midline and endline measurements at 6, 12 and 18 months included venous blood draws, diet, anthropometry, morbidity, food security and socio-economics. Length-for-age Z-score (LAZ) was the primary outcome. Analyses were intent-to-treat using mixed-effects regressions adjusted for clustering, sex, age and baseline. No differences existed in mean LAZ scores at endline (−1·219 (sd 0·06) KP, −1·211 (sd 0·03) MN, −1·266 (sd 0·03) NE). Acute infection prevalence was lower in the KP than NE group (P = 0·043). Mean serum Hb was higher in KP infants free from acute infection (114·02 (sd 1·87) g/l) than MN (107·8 (sd 2·5) g/l; P = 0·047) and NE (108·8 (sd 0·99) g/l; P = 0·051). Compliance was 84·9 % (KP) and 87·2 % (MN) but delivery 60 %. Adjusting for delivery and compliance, LAZ score at endline was significantly higher in the KP v. MN group (+0·2 LAZ; P = 0·026). A macro- and micronutrient-fortified supplement KP reduced acute infection, improved Hb and demonstrated a dose–response effect on LAZ adjusting consumption for delivery.
This study aimed to evaluate the risk of suicidal ideation and behavior associated with vortioxetine treatment in adults with major depressive disorder (MDD).
Suicide-related events were evaluated post hoc using 2 study pools: one short-term pool of 10 randomized, placebo-controlled studies (6–8 weeks) and another long-term pool that included 3 open-label extension studies (52 weeks). Evaluation of suicide-related events was performed using Columbia-Suicide Severity Rating Scale (C-SSRS) scores and treatment-emergent adverse events (TEAEs) data.
At baseline, the percentage of patients reporting any C-SSRS ideation or behavior events in short-term studies was similar between placebo (14.7%), vortioxetine (19.8%, 13.0%, 11.2%, and 13.7% for 5-, 10-, 15-, and 20-mg groups, respectively), and duloxetine active reference (13.2%) and did not change throughout the 6- to 8-week treatment period for placebo (17.0%), vortioxetine (19.3%, 13.5%, 12.6%, and 15% for 5-, 10-, 15-, and 20-mg groups, respectively), or duloxetine (11.3%). The incidence of suicide-related events for TEAEs in the short-term pool was 0.4% for placebo, 0.2% or 1.0% for vortioxetine 5 mg or 10 mg, and 0.7% each for vortioxetine 15 mg and 20 mg, as well as duloxetine. After 52-week treatment with vortioxetine, suicidal ideation based on C-SSRS was 9.8%, C-SSRS suicidal behavior was 0.2%, and the incidence of suicide-related events based on TEAEs was <1%. There were no completed suicides in any study.
Vortioxetine is not associated with increased risk of suicidal ideation or behavior in MDD patients.
Schizophrenia is associated with robust hippocampal volume deficits but subregion volume deficits, their associations with cognition, and contributing genes remain to be determined.
Hippocampal formation (HF) subregion volumes were obtained using FreeSurfer 6.0 from individuals with schizophrenia (n = 176, mean age ± s.d. = 39.0 ± 11.5, 132 males) and healthy volunteers (n = 173, mean age ± s.d. = 37.6 ± 11.3, 123 males) with similar mean age, gender, handedness, and race distributions. Relationships between the HF subregion volume with the largest between group difference, neuropsychological performance, and single-nucleotide polymorphisms were assessed.
This study found a significant group by region interaction on hippocampal subregion volumes. Compared to healthy volunteers, individuals with schizophrenia had significantly smaller dentate gyrus (DG) (Cohen's d = −0.57), Cornu Ammonis (CA) 4, molecular layer of the hippocampus, hippocampal tail, and CA 1 volumes, when statistically controlling for intracranial volume; DG (d = −0.43) and CA 4 volumes remained significantly smaller when statistically controlling for mean hippocampal volume. DG volume showed the largest between group difference and significant positive associations with visual memory and speed of processing in the overall sample. Genome-wide association analysis with DG volume as the quantitative phenotype identified rs56055643 (β = 10.8, p < 5 × 10−8, 95% CI 7.0–14.5) on chromosome 3 in high linkage disequilibrium with MOBP. Gene-based analyses identified associations between SLC25A38 and RPSA and DG volume.
This study suggests that DG dysfunction is fundamentally involved in schizophrenia pathophysiology, that it may contribute to cognitive abnormalities in schizophrenia, and that underlying biological mechanisms may involve contributions from MOBP, SLC25A38, and RPSA.
Age at sexual debut is known to have implications for future sexual behaviours and health outcomes, including HIV infection, early pregnancy and maternal mortality, but may also influence educational outcomes. Longitudinal data on schooling and sexual behaviour from a demographic surveillance site in Karonga district, northern Malawi, were analysed for 3153 respondents between the ages of 12 and 25 years to examine the association between sexual debut and primary school dropout, and the role of prior school performance. Time to dropout was modelled using the Fine and Gray survival model to account for the competing event of primary school completion. To deal with the time-varying nature of age at sexual debut and school performance, models were fitted using landmark analyses. Sexual debut was found to be associated with a five-fold increase in rate of subsequent dropout for girls and a two-fold increase in dropout rate for boys (adjusted hazard ratio [aHR] of 5.27, CI 4.22–6.57, and 2.19, CI 1.77–2.7, respectively). For girls who were sexually active by age 16, only 16% ultimately completed primary schooling, compared with 70% aged 18 or older at sexual debut. Prior to sexual debut, girls had primary completion levels similar to those of boys. The association between sexual debut and school dropout could not be explained by prior poor school performance: the effect of sexual debut on dropout was as strong among those who were not behind in school as among those who were overage for their school grade. Girls who were sexually active were more likely to repeat a grade, with no effect being seen for boys. Pathways to dropout are complex and may differ for boys and girls. Interventions are needed to improve school progression so children complete primary school before sexual debut, and to improve sex education and contraception provision.
This article explores the growing interface between social media and academic publishing. We discuss how the British Journal of Psychiatry (BJPsych) and other scientific journals are engaging with social media to communicate in a digital world. A growing body of evidence suggests that public visibility and constructive conversation on social media networks can be beneficial for researchers and clinicians, influencing research in a number of key ways. This engagement presents new opportunities for more widely disseminating information, but also carries risks. We note future prospects and ask where BJPsych should strategically place itself in this rapidly changing environment.
Declaration of interest
J.R.H., J.F.H. and D.T. are on the editorial board of the BJPsych. D.T. runs its social media arm.
OBJECTIVES/SPECIFIC AIMS: We aimed to explore the impact of leadership training on student’s abilities to work in interprofessional research teams successfully. The Translational Research Design and Interprofessional Skills Development Course (shortened, Interprofessional Research Design) brings together students from different disciplines (science & medicine) and education tracks (PhD, MD, MD/PhD training) in a seven-week course to learn interprofessional collaborative skills and leadership styles that support success in translational research environments, while undertaking a research grant writing project. Part of the course involves a two-day leadership training workshop (12 hours) with the goal of understanding leadership styles and how to develop productive working relationships with team members to help students work more effectively in high-performance, interprofessional team environments. The course incorporates personality testing to develop self-awareness, with various exercises meant to build empathy, as well as knowledge of project management and effective leadership. METHODS/STUDY POPULATION: Nine teams of 32 students (23 MD; 9 Ph.D.) who took part in the Interprofessional Research Design course in 2017 and 2018 were required to write a reflective essay at the end of the course. We used an inductive thematic analysis to evaluate the essays. Reflective essays were coded openly by one study member. Codes were rationalized; then codes were collaboratively developed into themes by the study authors. We identified issues of integration between student groups that functioned well together and those that did not. Reflective writing responses were grouped into overall positive experiences and negative experiences. RESULTS/ANTICIPATED RESULTS: Seven of the nine teams collectively described their experiences positively. Themes related to positive team experience were “empathizing with group members”, “sophisticated communication” and “collaborative workflow/styles.” We found that those who had a positive experience utilized knowledge and skills learned during leadership training to better understand and communicate with their teammates leading to a more collaborative and dynamic workflow. These groups had higher degrees of communication both between their task assignments and within task completion periods. They also showed more awareness of others’ needs in work and communication styles. For those that had a negative experience, themes were related to “basic communication”, “poor integration” and “theory-practice gap of leadership training.” Those who struggled showed much less in- and between-task communication and showed an inability to address the personal needs of other members in communication and workflow (while still often being able to identify them). DISCUSSION/SIGNIFICANCE OF IMPACT: These findings demonstrate the usefulness of leadership training that facilitates student self-awareness and empathy, as well as effective communication, leading to collaborative high-functioning interprofessional teams. Further work incorporating conflict management and exercises to overcome the theory/practice gap of leadership and teamwork training are recommended.
Report the efficacy of open-label amphetamine extended-release oral suspension (AMPH EROS) for the treatment of children with ADHD.
AMPH EROS has a 1-hr onset of effect and a duration of action of 13hours and was approved by FDA for treatment of ADHD in children aged 6–17 years based on a double-blind, placebo-controlled efficacy and safety study in children aged 6–12 years with ADHD. A significant treatment difference in change from pre-dose SKAMP-combined score was observed at the primary endpoint of 4hours post-dose (p<0.0001) and each post-dose time point assessed (1, 2, 4, 6, 8, 10, 12, 13hours).
Data reported here are from the 5-week, open-label dose optimization period. These efficacy data support the primary endpoint result.
Males and females aged 6 to 12 years with ADHD enrolled and began open-label treatment with 2.5 mg or 5mg/day of AMPH EROS titrated in 2.5–10mg/day increments until optimal dose (maximum 20mg/day). Doses could be decreased for tolerability. Subjects took morning AMPH EROS for 5weeks. Other efficacy outcomes during the open-label dose optimization phase: ADHD-RS (ADHD-Rating Scale), CGI-S (Clinical Global Impression of Severity), CGI-I (CGI-of Improvement) and CPRS (Conners’ Parent Rating Scale). All subjects were assessed for safety.
For the ITT population (n=99): treatment with AMPH EROS was associated with a mean change in ADHD-RS-IV (baseline to end of the open-label dose optimization; week 6) of 28.2 (±9.03) (Baseline score = 41.3±7.95). 90.9% of subjects had a change from baseline to open-label week 6 of ≥50% in the ADHD-RS-IV total score and were defined as responders. The CGI-S scores decreased continuously from baseline, with a high 4.8 at baseline to a low of 2.0 at open-label week 6. The percentage of subjects classified as moderately ill or greater correspondingly decreased from 97% at Baseline to 1% at open-label week 6. The decrease in the CGI-I over the study was similar to the change in CGI-S scores. CPRS for most categories decreased continuously from Baseline to open-label week 6. Mean change from baseline to open-label week 6 on the CPRS inattention T-score subscale was –25.3 (±14.38) and –24.4 (±13.87).
Adverse events (>5%) reported during dose optimization were decreased appetite, insomnia, affect lability, upper abdominal pain, mood swings and headache.
AMPH EROS was effective in reducing symptoms of ADHD in this open-label dose optimization. The AE profile of AMPH EROS was consistent with those of other amphetamine products.
Funding Acknowledgements: This work was funded by Tris Pharma, Inc.
The proprietary, immediate and extended drug delivery technologyLiquiXR® utilizes an ion-exchange resin that complexes with amphetamine or any active moiety that can be protonated and is water-soluble. The active ingredient of the drug product forms a complex with an ion exchange polymer of the resin resulting in micron-sized particles. A portion of these particles is then coated with an aqueous, pH-independent polymer designed to provide sustained release of drug product. The polymer coating applied to the ion-exchange resin particles is of varying thickness, allowing for extended release of active drug while uncoated particles provide for immediate release of drug.
The micron-sized particles lend themselves to being formulated into an appropriate dosage form: solid/chewable tablet, liquid suspension, orally disintegrating tablet, film, or capsules. Active ingredient of drug product is subsequently released from the dosage form in millions of particles, with release driven by a combination of ion exchange and diffusion. After drug release, the ion-exchange resin particles are excreted in the feces.
The release characteristics of LiquiXR allow for customized, sustained release of active drug ∼24hours post dose. Mechanistically, drug particles enter the gastrointestinal (GI) tract. As positively-charged ions from GI fluids diffuse across the coating, it displaces drug ions from product and they diffuse through the coating and into the GI fluids for absorption. As the coating is of variable thickness, some drug product takes longer to diffuse and absorb, providing for the delayed drug release characteristics.
The LiquiXR drug delivery technology has already been successfully utilized in the development of treatment options (liquid suspension and chewable tablet) that offer rapid absorption and sustained plasma levels after once-daily dosing. LiquiXR is utilized in Dyanavel® XR (amphetamine extended-release oral suspension; AMPH EROS), which is indicated for treatment of ADHD. It comprises 2.5mg/mL amphetamine base and uses LiquiXR technology to provide an immediate release component followed by an extended-release profile.
Efficacy of AMPH EROS was established in children 6 to 12 yr in a Phase 3, placebo-controlled laboratory classroom study. In that study, ADHD symptoms in children on an individually optimized dose of amphetamine (range 10–20mg/day) were statistically significantly improved compared with symptoms in children treated with placebo. For children treated with AMPH EROS, onset of effect was demonstrated at 1hour after dosing, and efficacy was observed through 13hr post-dose. The effect size (ES) was comparable to ES demonstrated for other psychostimulants tested in studies using a similar design. The efficacy data reported for AMPH EROS provides an excellent example of the potential utility and clinical application for other active drug products requiring an immediate and extended release profile.
Funding Acknowledgements: Support provided by Tris Pharma, Inc.
The proprietary immediate and extended drug delivery technology LiquiXR™ utilizes an ion-exchange resin that complexes with amphetamine or any other active moiety that can be protonated and is water-soluble. The active drug product forms a complex with ion-exchange polymers contained in the resin, which is then formed into micron-sized particles. Some of these particles are coated with an aqueous, pH-independent polymer designed to provide immediate or sustained release of active drug product. The polymer coating applied to the ion-exchange resin particles is of varying thickness, allowing for programmed, extended release of active drug product. Solid, coating-free particles provide for immediate release of active drug product.
The micron-sized particles are formulated into an appropriate dosage form (solid or chewable tablet, liquid suspension, orally disintegrating tablet, film, or capsules). Active drug product is subsequently released from the dosage form in millions of particles, with the release driven by a combination of ion exchange and diffusion. After drug release, the ion-exchange resin is excreted in the feces.
The release characteristics of LiquiXR™ are programmable and allow for a customized, sustained release of active drug product for up to 24hours post-dose. Mechanistically, drug particles enter the gastrointestinal tract. As positively-charged ions from gastrointestinal (GI) fluids diffuse across the coating, ionically-charged drug product diffuses through the coating and into the GI fluids for absorption. As the coating is of variable thickness, some drug product takes longer to diffuse and absorb, providing for the programmable delayed drug release characteristic.
The LiquiXR™ drug delivery technology is utilized in Dyanavel® XR (amphetamine extended-release oral suspension; AMPH EROS), which is indicated for the treatment of attention-deficit hyperactivity disorder. It comprises 2.5mg/mL amphetamine base complexed with LiquiXR technology to provide an immediate release component followed by an extended-release profile. The efficacy of AMPH EROS was established in children ages 6 to 12 years in a Phase 3, placebo-controlled laboratory classroom study. In that study, attention-deficit/hyperactivity disorder (ADHD) symptoms in children on an individually optimized dose of amphetamine (range 10–20mg/day) were statistically significantly improved compared with symptoms in children treated with placebo. For children treated with AMPH EROS, onset of effect was demonstrated at 1hour after dosing, and efficacy was observed through 13hours post-dose. The effect size was comparable to effect sizes demonstrated for other psychostimulants tested in studies using a similar design. The efficacy data reported for AMPH EROS provides an excellent example of the potential utility and clinical application for other active drug products requiring an immediate release and extended release profile.
Funding Acknowledgements: This work was funded by Tris Pharma, Inc.
To determine whether amphetamine extended-release oralsuspension (AMPH EROS) has an onset of effect at 30minutes postdose inchildren with ADHD.
This randomized, double-blind, 2-treatment, 2-sequence, placebo-controlled crossover pilot study enrolled subjects aged 6 to 12 years withattention-deficit/hyperactivity disorder (ADHD) and ADHD-Rating Scale-5 scores of ≥90th percentile for sex and age. A dose of 5 to 20mg/day of AMPH EROS was determined during a 1-week open-label phase based on medication history, symptom control, and tolerability. Subjects completed a practice laboratory classroom then received one day of double-blind active drug or placebo each in random sequence during 2 double-blind laboratory classroom days. Subjects completed the first double-blind laboratory classroom session, returned to open label drug for 5days then crossed over on day 6 during a second double-blind laboratory classroom session. DB dose was fixed at AMPH EROS 15, 17.5, or 20mg . The primary endpoint was change from predose in the Swanson, Kotkin, Agler, M-Flynn, Pelham rating scale-combined score (SKAMP-C) at 30minutes postdose on two DB days. The key secondary endpoint was change from predose in the SKAMP-C score at 3hours postdose for AMPH EROS compared with placebo. Safety assessments included vital signs and adverse events.
Eighteen subjects were enrolled in the study (14 males and 4 females) with a mean age of 9 years. At both 30minutes and 3hours postdose, changes from baseline in SKAMP-C for AMPH EROS vs. placebo were statistically significant (p<0.01 and p=0.0002, respectively) with corresponding effect sizes of 0.96 and 1.57. Adverse events (>10%) during the open-label phase included upper respiratory tract infection, fatigue, upper abdominal pain, headache, decreased appetite, and affect lability.
AMPH EROS was effective in reducing ADHD symptoms at 30minutes postdose. AEs were mild or moderate and consistent with those of other extended-release amphetamines.
Funding Acknowledgements: Support was provided by Tris Pharma, Inc.
Mass extinctions affect the history of life by decimating existing diversity and ecological structure and creating new evolutionary and ecological pathways. Both the loss of diversity during these events and the rebound in diversity following extinction had a profound effect on Phanerozoic evolutionary trends. Phylogenetic trees can be used to robustly assess the evolutionary implications of extinction and origination.
We examine both extinction and origination during the Late Ordovician mass extinction. This mass extinction was the second largest in terms of taxonomic loss but did not appear to radically alter Paleozoic marine assemblages. We focus on the brachiopod order Strophomenida, whose evolutionary relationships have been recently revised, to explore the disconnect between the processes that drive taxonomic loss and those that restructure ecological communities.
A possible explanation for this disconnect is if extinction and origination were random with respect to morphology. We define morphospace using principal coordinates analysis (PCO) of character data from 61 Ordovician–Devonian taxa and their 45 ancestral nodes, defined by a most parsimonious reconstruction in Mesquite. A bootstrap of the centroid of PCO values indicates that genera were randomly removed from morphospace by the Late Ordovician mass extinction, and new Silurian genera were clustered within a smaller previously unoccupied region of morphospace. Diversification remained morphologically constrained throughout the Silurian and into the Devonian. This suggests that the recovery from the Late Ordovician mass extinction resulted in a long-term shift in strophomenide evolution. More broadly, recovery intervals may hold clues to understanding the evolutionary impact of mass extinctions.