Large differences in relation to dental size, number, and morphology among and within modern human populations and between modern humans and other primate species have been observed. Molecular studies have demonstrated that tooth development is under strict genetic control, but, the genetic basis of primate tooth variation remains unknown. The PAX9 gene, which codes for a paired domain-containing transcription factor that plays an essential role in the development of mammal dentition, has been associated with selective tooth agenesis in humans and mice, which mainly involves the posterior teeth. To determine whether this gene is polymorphic in humans, we sequenced Ϸ2.1 kb of the entire four-exon region (exons 1, 2, 3 and 4; 1,026 bp) and exon-intron (1.1 kb) boundaries of 86 individuals sampled from Asian, European, and Native American populations. We provided evidence that human PAX9 polymorphisms are limited to exon 3 only and furnished details about the distribution of a mutation there in 350 Polish subjects. To investigate the pattern of selective pressure on exon 3, we sequenced ortholog regions of this exon in four species of New World monkeys and one gorilla. In addition, orthologous sequences of PAX9 available in public databases were also analyzed. Although several differences were identified between humans and other species, our findings support the view that strong purifying selection is acting on PAX9. New World and Old World primate lineages may, however, have different degrees of restriction for changes in this DNA region. human evolution ͉ tooth agenesis ͉ evolutionary window

Drosophilid communities living in four different physiographical regions of the state of Rio Grande do Sul (27°/34°S; 49.7°/57.5°W), Brazil, were analysed. Ignoring cosmopolitan species, this is about the southern limit of the majority of typically neotropical Drosophila species distribution. Numerical fluctuations of the most frequent species populations from each place were investigated in relation to climatic data and trophic‐resource availability. Of the four locations studied, Turvo is remarkable for being an enormous ecological reserve covered with subtropical perennially rainy forest, and for having stable weather conditions. Guaiba, on the other hand, is a more climatically unstable place, with unpredictable and more scarce resources. In Turvo, the community structure is shaped by the dominance of Drosophila willistoni and a low species diversity throughout the year. Low average niche‐breadth and niche‐overlap indices have also been found at feeding and breeding site levels. Guaíba showed the highest species‐diversity levels and was better exploited by D. simulans, a cosmopolitan species with a well‐known colonizing capacity. High niche breadth and overlap indices were characteristic for most species at this place. Results are discussed in the light of the communities' species composition and of environmental factors.

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Drosophilid communities living in four different physiographical regions of the state of Rio Grande do Sul (27°/34°S; 49.7°/57.5°W), Brazil, were analysed. Ignoring cosmopolitan species, this is about the southern limit of the majority of typically neotropical Drosophila species distribution. Numerical fluctuations of the most frequent species populations from each place were investigated in relation to climatic data and trophic‐resource availability. Of the four locations studied, Turvo is remarkable for being an enormous ecological reserve covered with subtropical perennially rainy forest, and for having stable weather conditions. Guafba, on the other hand, is a more climatically unstable place, with unpredictable and more scarce resources. In Turvo, the community structure is shaped by the dominance of Drosophila willistoni and a low species diversity throughout the year. Low average niche‐breadth and niche‐overlap indices have also been found at feeding and breeding site levels. Guafba showed the highest species‐diversity levels and was better exploited by D. simulans, a cosmopolitan species with a well‐known colonizing capacity. High niche breadth and overlap indices were characteristic for most species at this place. Results are discussed in the light of the communities' species composition and of environmental factors. Zusammenfassung Eine deskriptive und analytische Studie über Artengemeinschaften von Drosophiliden an vier neotropischen Standorten Das Artengefüge wild vorkommender Drosophila‐Arten wurde an vier Standorten des Bundesstaates Rio Grande do Sul (27°/34°S; 49°/57,5°W) von Brasilien untersucht. Mit Ausnahme der kosmopolitischen Arten entspricht dieses Gebiet der Südgrenze des Verbreitungsgebietes der meisten neotropischen Drosophila‐Arten. Die Unterschiede in den Individuenzahlen wurden für die Populationen der häufigsten Spezies an jedem Fangort in Zusammenhang mit den klimatischen Daten und den verfügbaren Nahrungsresourcen betrachtet. Von den vier Standorten ist Turvo als bedeutendes ökologisches Reservat besonders zu nennen, das von einem subtropischen, immergrünen Regenwald bedeckt ist und konstante Wetterbedingungen aufweist; Guaiba, auf der anderen Seite, ist eher ein klimatisch unbeständiges Gebiet mit unvorhersagbaren und ziemlich geringen Resourcen. Das Muster der Artengemeinschaft in Turvo ist bestimmt durch die Dominanz von Drosophila willistoni und einer geringeren Arten‐Diversität während des ganzen Jahres. Es wurden dementsprechend an den Futter‐ un Vermehrungstellen niedrige Werte für Nischenbreite und Nischenüberlappung gefunden. Guaiba zeigte die höchste Arten‐Divergenz bei vorwiegender Besiedlung durch D. simulans, einer kosmopolitischen Art mit auffallender Fähigkeit zur Kolonisation. Große Nischenbreite‐ und Überlappungs Indizes erwiesen sich für die meisten Arten an diesem Standort als charakteristisch. Die Ergebnisse werden in Hinblick auf den Zusammenhang zwischen Zusammensetzung der Artengemeinschaften und Umweltfaktoren diskutiert.