Editing Annual plant (section)

== The evolutionary and ecological drivers of the annual life cycle ==
Traditionally, there has been a prevailing assumption that annuals have evolved from [[perennial]] ancestors. However, recent research challenges this notion, revealing instances where perennials have evolved from annual ancestors.<ref name=":2">{{Cite journal |last1=Hjertaas |first1=Ane C. |last2=Preston |first2=Jill C. |last3=Kainulainen |first3=Kent |last4=Humphreys |first4=Aelys M. |last5=Fjellheim |first5=Siri |date=2023 |title=Convergent evolution of the annual life history syndrome from perennial ancestors |journal=Frontiers in Plant Science |volume=13 |doi=10.3389/fpls.2022.1048656 |pmid=36684797 |pmc=9846227 |issn=1664-462X |doi-access=free}}</ref> Intriguingly, models propose that transition rates from an annual to a perennial life cycle are twice as fast as the reverse transition.<ref name=":1">{{Cite journal |last1=Boyko |first1=James D. |last2=Hagen |first2=Eric R. |last3=Beaulieu |first3=Jeremy M. |last4=Vasconcelos |first4=Thais |date=November 2023 |title=The evolutionary responses of life-history strategies to climatic variability in flowering plants |journal=New Phytologist |language=en |volume=240 |issue=4 |pages=1587–1600 |doi=10.1111/nph.18971 |issn=0028-646X |doi-access=free|pmid=37194450 |bibcode=2023NewPh.240.1587B }}</ref>

The [[Life history theory|life-history theory]] posits that annual plants are favored when adult mortality is higher than seedling (or seed) mortality,<ref>{{Cite journal |last1=Charnov |first1=Eric L. |last2=Schaffer |first2=William M. |date=November 1973 |title=Life-History Consequences of Natural Selection: Cole's Result Revisited |url=https://www.journals.uchicago.edu/doi/10.1086/282877 |journal=The American Naturalist |language=en |volume=107 |issue=958 |pages=791–793 |doi=10.1086/282877 |bibcode=1973ANat..107..791C |s2cid=264255777 |issn=0003-0147}}</ref> i.e., annuals will dominate environments with disturbances or high temporal variability, reducing adult survival. This hypothesis finds support in observations of increased prevalence of annuals in regions with hot-dry summers,<ref name=":0" /><ref name=":1" /><ref>{{Cite journal |last1=Taylor |first1=Amanda |last2=Weigelt |first2=Patrick |last3=Denelle |first3=Pierre |last4=Cai |first4=Lirong |last5=Kreft |first5=Holger |date=November 2023 |title=The contribution of plant life and growth forms to global gradients of vascular plant diversity |journal=New Phytologist |language=en |volume=240 |issue=4 |pages=1548–1560 |doi=10.1111/nph.19011 |pmid=37264995 |issn=0028-646X |doi-access=free|bibcode=2023NewPh.240.1548T }}</ref> with elevated adult mortality and high seed persistence. Furthermore, the evolution of the annual life cycle under hot-dry summer in different families makes it one of the best examples of [[convergent evolution]].<ref name=":0" /><ref name=":1" /><ref name=":2" /> Additionally, annual prevalence is also positively affected by year-to-year variability.<ref name=":0" />

Globally, the prevalence of annual plants shows an upward trend with an increasing human footprint.<ref name=":0" /> Moreover, domestic grazing has been identified as contributing to the heightened abundance of annuals in grasslands.<ref>{{Cite journal |last1=Díaz |first1=Sandra |last2=Lavorel |first2=Sandra |last3=McIntyre |first3=Sue |last4=Falczuk |first4=Valeria |last5=Casanoves |first5=Fernando |last6=Milchunas |first6=Daniel G. |last7=Skarpe |first7=Christina |last8=Rusch |first8=Graciela |last9=Sternberg |first9=Marcelo |last10=Noy-Meir |first10=Imanuel |last11=Landsberg |first11=Jill |last12=Zhang |first12=Wei |last13=Clark |first13=Harry |last14=Campbell |first14=Bruce D. |date=February 2007 |title=Plant trait responses to grazing – a global synthesis |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2006.01288.x |journal=Global Change Biology |language=en |volume=13 |issue=2 |pages=313–341 |doi=10.1111/j.1365-2486.2006.01288.x |bibcode=2007GCBio..13..313D |hdl=11336/42236 |s2cid=84886127 |issn=1354-1013 |hdl-access=free}}</ref> Disturbances linked to activities like grazing and agriculture, particularly following European settlement, have facilitated the invasion of annual species from Europe and Asia into the New World.

In various ecosystems, the dominance of annual plants is often a temporary phase during secondary [[Ecological succession|succession]], particularly in the aftermath of disturbances. For instance, after fields are abandoned, annuals may initially colonize them but are eventually replaced by long-lived species.<ref>{{Cite journal |last1=Clark |first1=Adam Thomas |last2=Knops |first2=Johannes M. H. |last3=Tilman |first3=Dave |date=March 2019 |editor-last=Bardgett |editor-first=Richard |title=Contingent factors explain average divergence in functional composition over 88 years of old field succession |url=https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.13070 |journal=Journal of Ecology |language=en |volume=107 |issue=2 |pages=545–558 |doi=10.1111/1365-2745.13070 |bibcode=2019JEcol.107..545C |issn=0022-0477}}</ref> However, in certain Mediterranean systems, a unique scenario unfolds: when annuals establish dominance, perennials do not necessarily supplant them.<ref>{{Cite journal |last1=Uricchio |first1=Lawrence H. |last2=Daws |first2=S. Caroline |last3=Spear |first3=Erin R. |last4=Mordecai |first4=Erin A. |date=February 2019 |title=Priority Effects and Nonhierarchical Competition Shape Species Composition in a Complex Grassland Community |journal=The American Naturalist |language=en |volume=193 |issue=2 |pages=213–226 |doi=10.1086/701434 |issn=0003-0147 |pmc=8518031 |pmid=30720356|bibcode=2019ANat..193..213U }}</ref> This peculiarity is attributed to [[alternative stable state]]s in the system—both annual dominance and perennial states prove stable, with the ultimate system state dependent on the initial conditions.<ref>{{Cite journal |last1=DeMalach |first1=Niv |last2=Shnerb |first2=Nadav |last3=Fukami |first3=Tadashi |date=2021-08-01 |title=Alternative States in Plant Communities Driven by a Life-History Trade-Off and Demographic Stochasticity |url=https://www.journals.uchicago.edu/doi/10.1086/714418 |journal=The American Naturalist |language=en |volume=198 |issue=2 |pages=E27–E36 |doi=10.1086/714418 |pmid=34260874 |arxiv=1812.03971 |bibcode=2021ANat..198E..27D |s2cid=226191832 |issn=0003-0147}}</ref>