Despite their recent origin, NA deserts contain a diverse and endemic flora and fauna endowed with striking abilities to escape or tolerate their harsh, arid climate whose origins have been a topic of debate among evolutionary biologists for decades ( 6, 7). and northern Mexico ( 4) and appeared for the first time in scattered, ephemeral pockets as recently as the late-Miocene during Neogene uplift (5 to 7 Ma) and then expanded during the Pliocene (2.4 to 5 Ma) ( 5). North American (NA) deserts cover most of the southwest U.S. Compared with other biomes, many deserts emerged recently on a geological timescale ( 3) therefore, their endemic biota provides an ideal system for understanding the organismal potential to fill novel environments created by future climate change. Yet, we still have much to learn about the potential for biotic communities to adapt to new levels of increased aridity.

That the insular radiation of desert rock daisies stemmed from ancestors preadapted for dry conditions as edaphic endemics in otherwise densely vegetated tropical deciduous forests in northwest Mexico underscores the crucial role of exaptation and dispersal for shifts into arid environments.ĭesert biomes cover nearly a fifth of earth’s surface and are predicted to expand as a result of climate change ( 1, 2). Estimates of life history and micro-habitat in the rock daisies reveal a correlation between a suffrutescent perennial life history and edaphic endemism onto rocky outcrops, an ecological specialization that evolved prior to establishment and diversification in deserts. The earliest shift occurred out of tropical deciduous forests and led to an extensive radiation throughout North American deserts that accounts for the majority of extant desert rock daisies. We infer biome shifts using Bayesian inference with paleobiome-informed models and find evidence for seven independent shifts into desert habitats since the onset of aridification in the late Miocene. We sample rock daisies across two separate contact zones between tropical deciduous forest and desert biomes in western North America and infer a time-calibrated phylogeny based on target capture sequence data. In a comprehensive clade-based study, we investigate recent shifts into North American deserts in the rock daisies (tribe Perityleae), a diverse tribe of desert sunflowers (Compositae). Understanding the processes that enable organisms to shift into more arid environments as they emerge is critical for gauging resilience to climate change, yet these forces remain poorly known.

Ephemeral definition in biology