Search

Body size has a long history of study in paleobiology and underlies many important phenomena in macroevolution. Body-size patterns in the fossil record are often examined by utilizing size data alone, which hinders our ability to describe the biological meaning behind size change on macroevolutionary timescales. Without data reflecting the biological and geologic factors that drive size change, we cannot assess its mechanistic underpinnings. Existing frameworks for studying ontogeny and phylogeny can remedy this problem, particularly the classic age–size–"shape" space originally developed for studies of heterochrony. When evaluated based on metrics for age, size, and phenotype in populations, proposed mechanisms for size change can be outlined theoretically and tested empirically in the record. Using this framework, we can compare ontogenetic trajectories within and between species and determine how changes in size emerge. Here, we outline ontogenetic mechanisms for evolutionary size change, such as heterochrony, as well as how geologic factors can drive apparent, non-biological size change (e.g., taphonomic size sorting). To demonstrate the utility of this framework in actual paleobiological problems, we apply it to the Lilliput effect, a compelling and widely documented pattern of size decrease during extinction events. However, little is known about the mechanisms underlying this pattern. We provide a brief history of the Lilliput effect and refine its definition in a framework that can be mechanistically tested. Processes that likely produce Lilliput effects include allometric and sequence repatterning (including heterochrony) and evolutionary size-selective sorting. We describe these mechanisms and highlight relevant examples of the Lilliput effect for which feasible empirical tests are possible. [ABSTRACT FROM AUTHOR]

Introduction: Lesbian, gay, bisexual, and questioning (LGBQ) adolescents are particularly at risk for suicidal ideation; however, little clinical research is focused on treating this population. Attachment‐based family therapy (ABFT) is among the few empirically supported youth suicide treatments adapted for LGBQ adolescents. The purpose of this exploratory study is to determine the differential treatment effects and rates of change for LGBQ and heterosexual adolescents with depression and suicidal ideation receiving either ABFT or family enhanced nondirective supportive therapy (FE‐NST). Method: The sample included 129 adolescents (31% LGBQ), ages 12–18 randomized to the two treatment groups. Multilevel modeling was used to examine individual changes in depression and suicidal ideation over the 16‐week treatment. Results: Results revealed that LGBQ adolescents in the ABFT condition showed a greater rate of reduction in depressive symptoms over treatment, slope = −0.94, p < 0.001, than did LGBQ adolescents in the NST condition, slope = −0.41, p = 0.12. Heterosexual adolescents showed symptom reduction in both treatment conditions (ABFT slope = −0.47, p < 0.001; NST slope = −0.79, t (113) = −7.48, p < 0.001). Changes in suicidal ideation were found across time, but not across conditions. Conclusion: LGBQ adolescents in the ABFT condition had a sharper decrease in depressive symptoms and better outcomes at week 16. [ABSTRACT FROM AUTHOR]