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Synopsis Understanding the processes that shaped the distribution of species richness across the Tree of Life is a central macroevolutionary research agenda. Major ecological innovations, including transitions between habitats, may help to explain the striking asymmetries of diversity that are often observed between sister clades. Here, we test the impact of such transitions on speciation rates across decapod crustaceans, modeling diversification dynamics within a phylogenetic framework. Our results show that, while terrestrial lineages have higher speciation rates than either marine or freshwater lineages, there is no difference between mean speciation rates in marine and freshwater lineages across Decapoda. Partitioning our data by infraorder reveals that those clades with habitat heterogeneity have higher speciation rates in freshwater and terrestrial lineages, with freshwater rates up to 1.5 times faster than marine rates, and terrestrial rates approximately four times faster. This averaging out of marine and freshwater speciation rates results from the varying contributions of different clades to average speciation rates. However, with the exception of Caridea, we find no evidence for any causal relationship between habitat and speciation rate. Our results demonstrate that while statistical generalizations about ecological traits and evolutionary rates are valuable, there are many exceptions. Hence, while freshwater and terrestrial lineages typically speciate faster than their marine relatives, there are many atypically slow freshwater lineages and fast marine lineages across Decapoda. Future work on diversification patterns will benefit from the inclusion of fossil data, as well as additional ecological factors. 

Influencing adolescent interest in computing is key to engaging diverse teens in computer science learning. Prior work suggests that informal mentorship may be a powerful way to trigger and maintain interest in computing, but we still know little about how mentoring relationships form, how mentors trigger and maintain interest, or what qualities adolescents value in informal mentors. In a 3-week career exploration class with 18 teens from underrepresented groups, we had students write extensively about their informal computing mentors. In analyzing their writing, we found that most teens had informal computing mentors, that mentors were typically teachers, friends, and older siblings (and not parents or school counselors), and that what teens desired most were informal mentors that were patient, helpful, inspiring, and knowledgeable. These findings suggest that computing mentors can come in many forms, that they must be patient, helpful, and inspiring, but that they also require content knowledge about computing to be meaningful. Future work might explore what knowledge of computing is sufficient to empower teachers, parents, peers, and family to be effective computing mentors. 

Prior work on adolescent interest development shows that mentorship can promote interest in a subject while reshaping beliefs about the subject. To what extent do these same effects occur in computing, where interest and beliefs have traditionally been negative? We conducted two studies of the Puget Sound region in the United States, surveying and teaching 57 diverse adolescents with interests in computing. In the first study, we found that interest in computing was strongly related to having a mentoring relationship and not to gender or socioeconomic status. Teens with mentors also engaged in significantly more computing education and had more diverse beliefs about peers who engaged in computing education. The second study reinforced this finding, showing that teens who took a class from an instructor who aimed to become students' teacher-mentor had significantly greater positive changes in interest in computing than those who already had a mentor. These findings, while correlational, suggest that mentors can play a key role in promoting adolescent interest in computing. 

Analyses of morphological disparity have been used to characterize and investigate the evolution of variation in the anatomy, function and ecology of organisms since the 1980s. While a diversity of methods have been employed, it is unclear whether they provide equivalent insights. Here, we review the most commonly used approaches for characterizing and analysing morphological disparity, all of which have associated limitations that, if ignored, can lead to misinterpretation. We propose best practice guidelines for disparity analyses, while noting that there can be no ‘one-size-fits-all’ approach. The available tools should always be used in the context of a specific biological question that will determine data and method selection at every stage of the analysis.