![]() ![]() The prevalence of north and south temperate genera in the high-altitude Andean flora ( 12) supports the idea that colonization of the emerging high Andes was comparable to colonization of a newly formed island or island archipelago ( 16, 22) ( Fig. Despite this presumption, there are few reliable estimates of species diversification rates for Andean groups because of uncertainty about species numbers and the lack of robust, well resolved, and densely sampled phylogenies ( 20, 21). This recent uplift implies that at least some Andean plant groups must have diversified very recently and rapidly ( 16, 19). The cold upland habitats where much of this rich endemic flora is found today have been available for plant colonization only since the late Pliocene or early Pleistocene 2–4 Myr ago ( 15– 18) after final uplift of the northern Andes ( 15). Endemism is even higher, reaching 60%, in the high-altitude north Andean páramos ( 14). It forms part of the tropical Andean biodiversity hotspot, which contains an estimated 45,000 plant species, 44% of which are endemic ( 13). To compare plant diversification over a similarly short time period to the very recent fish radiations, we examined patterns of species diversification in the high-altitude flora of the northern Andes, which is by far the most species-rich of any tropical mountain massif ( 12). Direct comparisons with the cichlid fish diversification rates have been lacking because few comparably recent radiations have been found in other groups. ![]() If speciation is concentrated in the early phases of radiations ( 3, 7, 10, 11), this could explain the discrepancy between the exceptional rates of species diversification reported for very recent [5 Myr) ( 7). Furthermore, these approaches measure net diversification rates, and the effects of extinction are not assessed. In the absence of such phylogenies, measurements of diversification rates for most radiations are less precise because they average out episodes of faster and slower speciation. Accurate measurement of peak episodes of diversification embedded within older radiations requires fully sampled and resolved phylogenies ( 9). This discrepancy has been attributed in part to the recency of the fish radiations ( 7). ![]() A striking feature of species radiations is the discrepancy between the very high rates of species diversification reported for cichlid fish radiations in east African rift lakes and all bird, arthropod and plant radiations ( 2, 7, 8). Studies of rapid episodes of species diversification or species radiations have provided a continuously rich source of new insights into the evolutionary processes underlying diversification and modern patterns of biodiversity for the last 150 years ( 1– 6). Data from other genera indicate that lupines are one of a set of similarly rapid Andean plant radiations, continental in scale and island-like in stimulus, suggesting that the high-elevation Andean flora provides a system that rivals other groups, including cichlids, for understanding rapid species diversification. Lack of key innovations associated with the Andean Lupinus clade suggests that diversification was driven by ecological opportunities afforded by the emergence of island-like habitats after Andean uplift. Furthermore, it suggests that the high cichlid diversification rates are not unique. This exceeds previous estimates for plants, providing the most spectacular example of explosive plant species diversification documented to date. The age of this clade is estimated to be 1.18–1.76 Myr, implying a diversification rate of 2.49–3.72 species per Myr. ![]() Using DNA sequence data we identify a monophyletic group within the genus Lupinus representing 81 species endemic to the Andes. Because of the recent uplift of the northern Andes, the upland environments where much of this rich endemic flora is found have been available for colonization only since the late Pliocene or Pleistocene, 2–4 million years (Myr) ago. To compare plant diversification over a similar time period to the recent cichlid fish radiations, which are an order of magnitude faster than documented bird, arthropod, and plant radiations, we focus on the high-altitude flora of the Andes, which is the most species-rich of any tropical mountains. Species radiations provide unique insights into evolutionary processes underlying species diversification and patterns of biodiversity. ![]()
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