Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration has been suggested to be an important source of diversifying selection in the radiation of Lake Victoria cichlid fish. Initial variation in female preference is a prerequisite for diversifying selection; however, it is rarely studied in natural populations. In clear water areas of Lake Victoria, the sibling species Pundamilia pundamilia with blue males and Pundamilia nyererei with red males coexist, intermediate phenotypes are rare, and most females have species-assortative mating preferences. Here, we study a population of Pundamilia that inhabits turbid water where male coloration is variable from reddish to blue with most males intermediate. We investigated male phenotype distribution and female mating preferences. Male phenotype was unimodally distributed with a mode on intermediate color in 1 year and more blue-shifted in 2 other years. In mate choice experiments with females of the turbid water population and males from a clearer water population, we found females with a significant and consistent preference for P. pundamilia (blue) males, females with such preferences for P. nyererei (red) males, and many females without a preference. Hence, female mating preferences in this population could cause disruptive selection on male coloration that is probably constrained by the low signal transduction of the turbid water environment. We suggest that if environmental signal transduction was improved and the preference/color polymorphism was stabilized by negative frequency-dependent selection, divergent sexual selection might separate the 2 morphs into reproductively isolated species resembling the clear water species P. pundamilia and P. nyererei.

Parallel evolution of facial stripe patterns in the Neolamprologus brichardilpulcher species complex endemic to Lake Tanganyika

Colour pattern diversity can be due to random processes or to natural or sexual selection. Consequently, similarities in colour patterns are not always correlated with common ancestry, but may result from convergent evolution under shared selection pressures or drift. Neolamprologus brichardi and Neolamprologus pulcher have been described as two distinct species based on differences in the arrangement of two dark bars on the operculum. Our study uses DNA sequences of the mitochondrial control region to show that relatedness of haplotypes disagrees with species assignment based on head colour pattern. This suggests repeated parallel evolution of particular stripe patterns. The complete lack of shared haplotypes between populations of the same or different phenotypes reflects strong philopatric behaviour, possibly induced by the cooperative breeding mode in which offspring remain in their natal territory and serve as helpers until they disperse to nearby territories or take over a breeding position. Concordant phylogeographic patterns between N. brichardi/N. pulcher populations and other rock-dwelling cichlids suggest that the same colonization routes have been taken by sympatric species and that these routes were affected by lake level fluctuations in the past. (C) 2007 Elsevier Inc. All rights reserved.

Mid-Holocene Climate and Culture Change in the South Central Ande

This chapter reviews the history of study and the current status of Mid-Holocene climatic and cultural change in the South Central Andes, which host a wide range of different habitats from Pacific coastal areas up to extremely harsh cold and dry environments of the high mountain plateau, the altiplano or the puna. Paleoenvironmental information reveals high amplitude and rapid changes in effective moisture during the Holocene period and, consequently, dramatically changing environmental conditions. Therefore, this area is suitable to study the response of hunting and gathering societies to environmental changes, because the smallest variations in the climatic conditions have large impacts on resources and the living space of humans. This chapter analyzes environmental and paleoclimatic information from lake sediments, ice cores, pollen profiles, and geomorphic processes and relates these with the cultural and geographic settlement patterns of human occupation in the different habitats in the area of southern Peru, southwest Bolivia, northwest Argentina, and north Chile and puts in perspective of the early and late Holocene to present a representative range of environmental and cultural changes. It has been found that the largest changes took place around 9000 cal yr BP when the humid early Holocene conditions were replaced by extremely arid but highly variable climatic conditions. These resulted in a marked decrease of human occupation, “ecological refuges,” increased mobility, and an orientation toward habitats with relatively stable resources (such as the coast, the puna seca, and “ecological refuges”).