Abstract.-Unlike populations of many terrestrial species, marine populations often are not separated by obvious, permanent barriers to gene flow. When species have high dispersal potential and few barriers to gene flow, allopatric divergence is slow. Nevertheless, many marine species are of recent origin, even in taxa with high dispersal potential. To understand the relationship between genetic structure and recent species formation in high dispersal taxa, we examined population genetic structure among four species of sea urchins in the tropical Indo-West Pacific that have speciated within the past one to three million years. Despite high potential for gene flow, mtDNA sequence variation among 200 individuals of four species in the urchin genus Echinometra shows a signal of strong geographic effects. These effects include (1) substantial population heterogeneity; (2) lower genetic variation in peripheral populations; and (3) isolation by distance. These geographic patterns are especially strong across scales of 5000-10,000 km, and are weaker over scales of 2500-5000 km. As a result, strong geographic patterns would not have been readily visible except over the wide expanse of the tropical Pacific. Surface currents in the Pacific do not explain patterns of gene flow any better than do patterns of simple spatial proximity. Finally, populations of each species tend to group into large mtDNA regions with similar mtDNA haplotypes, but these regional boundaries are not concordant in different species. These results show that all four species have accumulated mtDNA differences over similar spatial and temporal scales but that the precise geographic pattern of genetic differentiation varies for each species. These geographic patterns appear much less deterministic than in other well-known coastal marine systems and may be driven by chance and historical accident.

Unlike populations of many terrestrial species, marine populations often are not separated by obvious, permanent barriers to gene flow. When species have high dispersal potential and few barriers to gene flow, allopatric divergence is slow. Nevertheless, many marine species are of recent origin, even in taxa with high dispersal potential. To understand the relationship between genetic structure and recent species formation in high dispersal taxa, we examined population genetic structure among four species of sea urchins in the tropical Indo-West Pacific that have speciated within the past one to three million years. Despite high potential for gene flow, mtDNA sequence variation among 200 individuals of four species in the urchin genus Echinometra shows a signal of strong geographic effects. These effects include (1) substantial population heterogeneity; (2) lower genetic variation in peripheral populations; and (3) isolation by distance. These geographic patterns are especially strong across scales of 5000-10,000 km, and are weaker over scales of 2500-5000 km. As a result, strong geographic patterns would not have been readily visible except over the wide expanse of the tropical Pacific. Surface currents in the Pacific do not explain patterns of gene flow any better than do patterns of simple spatial proximity. Finally, populations of each species tend to group into large mtDNA regions with similar mtDNA haplotypes, but these regional boundaries are not concordant in different species. These results show that all four species have accumulated mtDNA differences over similar spatial and temporal scales but that the precise geographic pattern of genetic differentiation varies for each species. These geographic patterns appear much less deterministic than in other well-known coastal marine systems and may be driven by chance and historical accident.

Bilaterally symmetrical, "regular" sea urchins in the Family Echinometridae (Class Echinoidea; Phylum Echinodermata) were found to lack a locomotor anterior. Heterocentrotus mammillatus and Echinometra mathaei were observed while locomoting. Members of both ellipsoidal species were found to proceed with their short or long axis foremost with statistically equivalent frequencies. This finding demonstrates that the evolution of bilateral symmetry is not always accompanied by the evolution of a locomotor "anterior" end. The elliptical echinometrid sea urchins provide a particularly appropriate study group for investigating the relationship between the evolution of body form and locomotor behavior. Although the radially symmetrical regular sea urchins, from which the echinometrids sprang, lack a locomotor anterior, all "irregular" echinoids, which are also derived from a regular ancestor but are bilaterally symmetrical, possess an "obligate" locomotor anterior. The symmetry and behavior exhibited by the elliptical echinometrid sea urchins therefore demonstrates that the first irregular echinoids (which exhibit bilateral symmetry by definition) need not have possessed a locomotor anterior as they do today.

Abstract.-Bilaterally symmetrical, "regular" sea urchins in the Family Echinometridae (Class Echinoidea; Phylum Echinodermata) were found to lack a locomotor anterior. Heterocentrotus mammillatus and Echinometra mathaei were observed while locomoting. Members of both eIlipsoidal species were found to proceed with their short or long axis foremost with statistically equivalent frequencies. This findingdemonstrates that the evolution of bilateral symmetry is not alwaysaccompanied by the evolution of a locomotor "anterior" end. The elliptical echinometrid seaurchinsprovidea particularlyappropriate studygroupfor investigatingthe relationshipbetween the evolution of body form and locomotor behavior. Although the radially symmetrical regular sea urchins, from which the echinometrids sprang, lack a locomotor anterior, all "irregular" echinoids, which are also derived from a regular ancestor but are bilaterally symmetrical, possess an "obligate" locomotoranterior. The symmetryand behavior exhibitedby the eIlipticalechinometrid sea urchins therefore demonstrates that the first irregular echinoids (which exhibit bilateral symmetry by definition) need not have possesseda locomotor anterior as they do today.

Experiential learning (EL) can offer a high impact educational opportunity that benefits students from diverse backgrounds, creating an inclusive learning environment. Barriers to the generalization of EL can include a lack of institutional support, risk avoidance, time, and faculty instructional ability. As well EL require additional efforts from students, which can include a non-traditional perspective of cognitive, psychomotor and affective domains. The authors have experienced success in optimizing three important EL components: preparation, customization and on-site triage. We report results from a quasiexperimental qualitative study of 102 students who responded to a post-event perception survey of their comfort levels, understanding, preparation and instructor’s role. We found that students were generally positive about their EL, however; most positive of the instructor helping them feel more comfortable during the EL (x̅=3.80 on a 4.00 scale) and their feelings afterward (x̅=3.75). Students were very positive in their belief that they learned more from the EL than in a traditional class (x̅=3.75). There were positive and significant changes in students attitudes, perceptions and beliefs in the time prior to the event compared to the time during and after. Students were significantly more likely to exhibit higher comfort levels after the event than prior (t =-3.459, p < .001).