Maize streak virus (MSV; family Geminiviridae, genus Mastrevirus) is the most important virus of maize (Zea mays L.) in sub-Saharan Africa. The relatedness of this virus to others showing streak symptoms from grasses on or near maize... more
Maize streak virus (MSV; family Geminiviridae, genus Mastrevirus) is the most important virus of maize (Zea mays L.) in sub-Saharan Africa. The relatedness of this virus to others showing streak symptoms from grasses on or near maize fields from five ecological areas of Nigeria was studied using genetic scanning analyzer. The relationship dendogram showed 50-95% variations as the 30 isolates were grouped into two main clusters at 0.50 coefficient of variation, five subgroups at 0.06 and 25 at 0.95 coefficient of variation, respectively. The dendogram suggests five family trees at 60% similarity. Split decomposition data showed three clusters implying three evolutionary trees among the streak isolates in Nigeria, as indicated by the three major groupings. The first cluster had four subgroups. MSV (IITA) is within the first tree, which also had 14 other grass isolates. The second tree comprised only three isolates, which were all transmissible to maize and produced typical or severe symptoms in their grass hosts. The third tree had 12 isolates, which were diverse from each other. Despite basic differences in the theoretical background of UPGMA cluster analysis and Split Decomposition, these two approaches of phylogeny reconstruction yielded similar results.
In what way can demographic research, a field of study that aims to analyze population change, benefit from studying outlying groups, countries, or events? Our analytic work suggests that three types of outliers might emerge in... more
In what way can demographic research, a field of study that aims to analyze population change, benefit from studying outlying groups, countries, or events? Our analytic work suggests that three types of outliers might emerge in demographic transitions: 1) Vanguards – the initiators of the transition; 2) Laggards - late adopters of the innovative behavior; and 3) Isolates - those who never joined the transition. We discuss the advantages of analyzing outliers, the barriers that impede such research, and the implications of failing to identify them. Identifying vanguard groups might help demographers locate the onset of a demographic transition, make more accurate projections, and better anticipate the potential trajectory that other groups will experience. Studying laggard populations allows exploring the mechanisms that facilitate or impede the adoption of new behavior. Isolates can help demographers learn about the essentials of demographic processes before they were affected by other changes.
