Ever since Ernst Mayr (1942) called ring species the 'perfect demonstration of speciation', they have attracted much interest from researchers examining how two species evolve from one. In a ring species, two sympatric and reproductively isolated forms are connected by a long chain of intermediate populations that encircle a geographic barrier. Ring species have the potential to demonstrate tha...

Since Darwin published the "Origin," great progress has been made in our understanding of speciation mechanisms. The early investigations by Mayr and Dobzhansky linked Darwin's view of speciation by adaptive divergence to the evolution of reproductive isolation, and thus provided a framework for studying the origin of species. However, major controversies and questions remain, including: When i...

Hybrid zones are a valuable tool for studying the process of speciation and for identifying the genomic regions undergoing divergence and the ecological (extrinsic) and nonecological (intrinsic) factors involved. Here, we explored the genomic and geographic landscape of divergence in a hybrid zone between Papilio glaucus and Papilio canadensis. Using a genome scan of 28,417 ddRAD SNPs, we ident...

The genetic similarity among individuals or populations can be ascertained using a number of statistical techniques (reviewed by Bohonak 1999; Neigel 1997; Roderick 1996; Slatkin 1985). When populations can be defined a priori, one option is to analyze genetic ‘‘isolation by distance’’ (sensu Wright 1943) by plotting the genetic similarity (or distance) among population pairs as a function of t...

Understanding the factors determining genetic diversity and structure in peripheral populations is a long-standing goal of evolutionary biogeography, yet little empirical information is available for tropical species. In this study, we combine information from nuclear microsatellite markers and niche modelling to analyse the factors structuring genetic variation across the southernmost populati...

Background: Chronic nursing shortages have plagued rural communities for many years. It is therefore important to highlight the specific challenges confronting rural areas in regards to recruiting and retaining nurses. One challenging factor associated with recruitment and retention of rural nurses is professional isolation. Purpose: This paper reports the findings of an integrative review cond...

EDRS PRICE MF01/PC01 Plus Postage. DESCRIPTORS *Alcohol Education; Community Cooperation; *Community Involvement; Cultural Isolation; Drinking; *Drug Education; Drug Use; Ethnic Groups; Health Education; *Hispanic Americans; Marijuana; *Rural Areas; Rural Schools; Secondary Education; Secondary School Students; Small Schools IDENTIFIERS *Health Promotion; Isolation (Geographic); *New Mexico (Mo...

Studies of postzygotic isolation often involve well-differentiated taxa that show a consistent level of incompatibility, thereby limiting our understanding of the initial stages and development of reproductive barriers. Dendroctonus ponderosae provides an informative system because recent evidence suggests that distant populations produce hybrids with reproductive incompatibilities. Dendroctonu...