Language and ethnobiological skills decline precipitously in Papua New Guinea, the world's most linguistically diverse nation.

Papua New Guinea is home to >10% of the world's languages and rich and varied biocultural knowledge, but the future of this diversity remains unclear. We measured language skills of 6,190 students speaking 392 languages (5.5% of the global total) and modeled their future trends using individual-level variables characterizing family language use, socioeconomic conditions, students' skills, and language traits. This approach showed that only 58% of the students, compared to 91% of their parents, were fluent in indigenous languages, while the trends in key drivers of language skills (language use at home, proportion of mixed-language families, urbanization, students' traditional skills) predicted accelerating decline of fluency to an estimated 26% in the next generation of students. Ethnobiological knowledge declined in close parallel with language skills. Varied medicinal plant uses known to the students speaking indigenous languages are replaced by a few, mostly nonnative species for the students speaking English or Tok Pisin, the national lingua franca. Most (88%) students want to teach indigenous language to their children. While crucial for keeping languages alive, this intention faces powerful external pressures as key factors (education, cash economy, road networks, and urbanization) associated with language attrition are valued in contemporary society.

The towering orogeny of New Guinea as a trigger for arthropod megadiversity.

Early studies on Melanesian mountain systems provided insights for fundamental evolutionary and ecological concepts. These island-like systems are thought to provide opportunities in the form of newly formed, competition-free niches. Here we show that a hyperdiverse radiation of freshwater arthropods originated in the emerging central New Guinea orogen, out of Australia, about 10 million years ago. Further diversification was mainly allopatric, with repeated more recent colonization of lowlands as they emerged in the form of colliding oceanic island arcs, continental fragments and the Papuan Peninsula, as well as recolonization of the central orogen. We unveil a constant and ongoing process of lineage accumulation while the carrying capacity of the island is about to be reached, suggesting that lineage diversification speed now exceeds that of landmass/new ecological opportunity formation. Therefore, the central orogeny of New Guinea acts as a motor of diversification for the entire region.