A comparative study of life history and gene flow in darters (Pisces: Percidae)

Gene flow, or the exchange of genes between populations, is important because it determines the evolutionary trajectory of a species, including the relative influences of genetic drift and natural selection in the process of population differentiation. Gene flow differs among species because of variation in dispersal capability and abundances across taxa, and historical forces related to geological or lineage history. Both history and ecology influence gene flow in potentially complicated ways, and accounting for their effects remains an important problem in evolutionary biology. This research is a comparative study of gene flow and life-history in a monophyletic group of stream fishes, the darters. As a first step in disentangling historical and ecological effects, I reconstructed the phylogenetic relationships of the study species from nucleotide sequences in the mtDNA control region. I then used this phylogeny and regional glaciation history to infer historical effects on life-history evolution and gene flow in 15 species of darters. Gene flow was estimated indirectly, using information from 20 resolvable and polymorphic allozyme loci. When I accounted for historical effects, comparisons across taxa revealed that gene flow rates were closely associated with differences in clutch sizes and reproductive investment patterns. I hypothesized that differences in larval dispersal among taxa explained this relationship. Results from a field study of larval drift were consistent with this hypothesis. Finally, I asked whether there was an interaction between species' ecology and genetic differentiation across biogeographically distinct regions. Information from allozymes and mtDNA sequences revealed that life history plays an important role in the magnitude of species divergence across biogeographic boundaries. These results suggested an important association between life histories and rates of speciation following an allopatric isolation event. This research, along with other studies from the literature, further illustrates the enormous potential of North American freshwater fishes as a system for studying speciation processes. ^

Armed Groups and Violence in Paraguay

Armed violence in Paraguay is not a recent phenomenon. During the second half of the XX Century, Paraguay saw the rise of a larger number of underground, revolutionary movements that sought the overthrow of the Alfredo Stroessner’s (1954-1989) government. From among those movements emerged the Partido Patria Libre (or, Free Fatherland, also known for its acronym PPL), made up of a two branches: one legal and the other one, operational. The latter was based on people’s power, as represented by “Ejército del Pueblo Paraguayo” (or, the Paraguayan People’s Army, with acronym EPP). After EPP broke with PPL in March 2008, this Marxist-oriented revolutionary project, which was apparently oriented to put an end to the social, political and economic inequalities in Paraguay, began to carry out markedly criminal activities, which included bank robberies, kidnappings, assassinations, terrorist attacks and armed confrontations. Its strategies and modus operandi utilized by the Armed Revolutionary Forces of Colombia (FARC). Paraguay features a farm sector in a state of crisis, in which cattle-ranchers, peasants and agro-exporting companies live in a constant strife. The Paraguayan Departments that are the most affected by this situation are Concepciόn, San Pedro, Canindeyú y Caazapá, which also suffer from a weak government presence. This deficiency has made these departments ripe for drug-trafficking activity by Brazilian groups such as Primer Comando Capital (i.e., First Capital command), also PCC and Comando Vermelho, (i.e., The Red Command). That is why many peasants, now recruited by EPP, have joined the drug-trafficking business and that, not only as marihuana growers but as “campanas” (i.e., early warning sentinels) for the organization. This helps shape their attitudes for their future involvement in all areas of drug-trafficking. Paraguayan society is the result of social inequity and inequality, such as those resulting from a lack of opportunity. Although Paraguay has successfully recovered from the last world economic crisis, economic growth, by itself, does not ensure an improvement in the quality of life. As long as such economic and social gaps persist and the government fails to enact the policies that would result in a more just society and toward EPP neutralization or containment, the latter is bound to grow stronger. In this context, the situation in Paraguay calls for more research into the EPP phenomenon. It would also seem necessary for Paraguay to promote an open national debate that includes all sectors of society in order to raise consciousness and to induce society to take actual steps to eliminate the EPP, as well as any other group that might arise in the immediate future. EPP has strong connections with the Frente Patriόtico Manuel Rodríguez in Chile and other armed groups and peasant movements in other countries of this region. Although most governments in the region are aware that the armed struggle is not a solution to current problems, it might be worth it to hold a regional debate about armed or insurgent groups in Latin American to seek common strategies and cooperation on dealing with them since the expansion of these armed groups is a problem for all.