Abstract. Habitat fragmentation often arises from human-induced alterations to the matrix that reduce or eliminate dispersal between habitat patches. Elimination of dispersal increases local extinction and decreases recolonization. These phenomena were observed in the eastern collared lizard (Crotaphytus collaris collaris), which lives in the mid-continental highland region of the Ozarks (Missouri, USA) on glades: habitats of exposed bedrock that form desert-like habitats imbedded in a woodland matrix. With the onset of woodland fire suppression, glade habitats degenerated and the woodland matrix was altered to create a strong barrier to dispersal. By 1980, lizard populations in the Ozarks were rapidly going extinct. In response to this decline, some glades were restored by clearing and burning. Starting in 1984, collared lizard populations were translocated onto these restored habitats. The translocated populations persisted but did not colonize nearby glades or disperse among one another. In 1994 prescribed woodland fires were initiated, which unleashed much dispersal and colonizing behavior. Dispersal was highly nonrandom by both intrinsic variables (age, gender) and extrinsic variables (overall demography, glade population sizes, glade areas, landscape features), resulting in different classes of lizards being dominant in creating demographic cohesiveness among glades, colonizing new glades on a mountain, and colonizing new mountain systems. A dramatic transition was documented from isolated fragments, to a nonequilibrium colonizing metapopulation, and finally to a stable metapopulation. This transition is characterized by the convergence of rates of extinction and recolonization and a major alteration of dispersal probabilities and pattern in going from the nonequilibrium to stable metapopulation states.

Habitat fragmentation is one of the more important contributors to species endangerment, but one form of fragmentation, here called dispersal fragmentation, can often go unobserved for many years after it has occurred. Many species live in naturally fragmented habitats, but the local populations are interconnected genetically and demographically by dispersal through the environmental matrix in which the habitats are embedded. Because of dispersal, the local populations are not truly fragmented evolutionarily or ecologically. However, when human activities alter the environmental matrix such that dispersal is no longer possible, the population does indeed become fragmented even though they initially are present in the same habitats. An example of dispersal fragmentation via an altered environmental matrix is provided by the eastern collared lizard (Crotaphytus collaris collaris). This lizard lives on open, rocky habitats, called glades, that are embedded in the forests of the Ozarks, a highland region located primarily in Missouri and Arkansas in the USA. Forest fire suppression has reduced this habitat, resulting in severe habitat fragmentation, disruption of gene flow, loss of genetic variation within glade populations, and local extinction without recolonization. Beginning in 1982, glade habitats were restored by clearing and burning in the Peck Ranch area of the Missouri Ozarks, a region where the lizards had gone extinct. Starting in 1984, lizard populations were translocated from other Missouri glades onto restored glades at the Peck Ranch. Although these translocated populations survived well on the restored glades, no movement was detected between glades, some just 50 m apart, and no colonization of nearby restored glades, some just 60 m away, occurred between 1984 and 1993. Fragmentation, lack of colonization, no gene flow, and loss of genetic variation still persisted despite translocation reversing some of the local extinction. Fire scar data from trees and tree stumps indicated that forest fires were common in this area prior to European settlement, so in 1994 a new management policy of prescribed burning of both the glades and their forest matrix was initiated. Once the forest had been burned, the lizards could disperse kilometers through the forest, thereby reestablishing the processes of dispersal, gene flow, colonization, and local extinction followed by recolonization. This resulted in a dramatic increase in population size and inhabited area. By incorporating a landscape perspective into the management strategy, the eastern collared lizard has been successfully reestablished in a region of historic extirpation.

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Although the prevalence of malignancy in average risk women under age 40 presenting with a palpable breast abnormality is low, the management of benign‐appearing palpable abnormalities remains controversial. This study assesses the imaging evaluation, subsequent management, and outcomes of women under age 40 presenting with a palpable area of concern. This study also evaluates the costs, utility, and outcomes of BI‐RADS 3 assessment in this patient population. A single institution retrospective case review from July 2010 through June 2013 identified women under age 40 presenting with a new palpable breast abnormality. Diagnostic imaging evaluation was performed. BI‐RADS assessments and recommendations were recorded prospectively. Outcome was determined by tissue diagnosis, 2 years of surveillance, or search of the hospital tumor registry. Performance measures were calculated. Among 1440 cases, 1052 were initially assessed as BI‐RADS 1 or 2 (73.1%), 184 as BI‐RADS 3 (12.8%), 182 as BI‐RADS 4 (12.6%), and 22 as BI‐RADS 5 (1.5%). In all, 30 breast malignancies were diagnosed (cancer yield 2.1%). All 30 cancers were initially categorized as BI‐RADS 4 or 5. No BI‐RADS 1, 2, or 3 findings proved malignant. The imaging evaluation sensitivity was 100%, specificity was 87.7%, and accuracy was 87.9%. The negative predictive value was 100% and the positive predictive value was 14.7%. Average risk women under age 40 presenting with a palpable abnormality have a low prevalence of breast cancer. Imaging evaluation has a high sensitivity and negative predictive value, thereby allowing for confident characterization and appropriate management recommendations. For palpable solid masses with benign imaging features in women under age 40, short‐term interval follow‐up with subsequent periodic imaging or clinical examination for a total of 2 years is a cost‐effective and safe alternative to biopsy.