A recovery network leads to the natural recolonization of an archipelago and a potential trailing edge refuge

Rapid environmental change is reshaping ecosystems and driving species loss globally. Carnivore populations have declined and retracted rapidly and have been the target of numerous translocation projects. Success, however, is complicated when these efforts occur in novel ecosystems. Identifying refuges, locations that are resistant to environmental change, within a translocation framework should improve population recovery and persistence. American martens (Martes americana) are the most frequently translocated carnivore in North America. As elsewhere, martens were extirpated across much of the Great Lakes region by the 1930s and, despite multiple translocations beginning in the 1950s, martens remain of regional conservation concern. Surprisingly, martens were rediscovered in 2014 on the Apostle Islands of Lake Superior after a putative absence of >40 yr. To identify the source of martens to the islands and understand connectivity of the reintroduction network, we collected genetic data on martens from the archipelago and from all regional reintroduction sites. In total, we genotyped 483 individual martens, 43 of which inhabited the Apostle Islands (densities 0.42-1.46 km^-2 ). Coalescent analyses supported the contemporary recolonization of the Apostle Islands with progenitors likely originating from Michigan, which were sourced from Ontario. We also identified movements by a first-order relative between the Apostle Islands and the recovery network. We detected some regional gene flow, but in an unexpected direction: individuals moving from the islands to the mainland. Our findings suggest that the Apostle Islands were naturally recolonized by progeny of translocated individuals and now act as a source back to the reintroduction sites on the mainland. We suggest that the Apostle Islands, given its protection from disturbance, complex forest structure, and reduced carnivore competition, will act as a potential refuge for marten along their trailing range boundary and a central node for regional recovery. Our work reveals that translocations, even those occurring along southern range boundaries, can create recovery networks that function like natural metapopulations. Identifying refuges, locations that are resistant to environmental change, within these recovery networks can further improve species recovery, even within novel environments. Future translocation planning should a priori identify potential refuges and sources to improve short-term recovery and long-term persistence.

Biopsy of pediatric brain stem tumors

26 patients, average age of 7.3 years, has biopsies of a brain stem tumor. 62% of the patients presented with hydrocephalus, and ventriculoperitoneal shunts were placed 7-10 days prior to biopsy. The midbrain was biopsied 13 times, the pons 3 and the medulla 12 times. Tissue for histopathologic examination was obtained at each operation and demonstrated astrocytoma in 13 patients, glioblastoma in 6, 'no tumor seen' in 5 and ependymoma in 2. Astrocytomas were usually located in the upper brain stem, and all of the glioblastomas were located in the medulla. The operative mortality was zero, and the morbidity was largely related to increased cranial nerve deficit. All the astrocytoma patients were treated with radiation only; whereas, 4 patients with glioblastoma were treated with vincristine, CCNU and methylprednisone in addition to radiation as described by the Children's Cancer Study Group (CCG-944). 3 patients with 'no tumor' were not treated and are alive and well 15-41 months following operation. 2 patients with no tumor were treated, one as a glioblastoma multiforme, subsequently verified at postmortem examination, and one as a midbrain astrocytoma. 1 patient with astrocytoma died 3 months following operation, all the remainder are living and well 4-51 months following operation. Irrespective of the treatment, all 7 patients with glioblastoma expired within 9 months of diagnosis. The prognosis for survival for patients with brain stem astrocytoma is superior to those with glioblastoma multiforme. Specific histopathologic correlation with clinical management may lead to improved and prolonged survival for patients with brain stem glioma.

Posterior fossa extraaxial cyst: diagnosis with metrizamide CT cisternography

This study describes a new technique for the study of posterior fossa extraaxial cysts. Using metrizamide (Amipaque) CT cisternography, a rapid, simple, low morbidity method is now available which gives both anatomic and physiologic information that may obviate the need for pneumoencephalography and angiography. Two cases are reported; in a third the diagnosis was definitively excluded. By doing serial CT scans following the intrathecal introduction of metrizamide, data concerning the diffusion characteristics of these cysts as well as the accompanying hydrocephalus are obtained.