Editing Coevolution (section)

====Birds and bird-pollinated flowers====
{{Further|Ornithophily}}
[[File:Purple-throated carib hummingbird feeding.jpg|thumb|left|[[Purple-throated carib]] feeding from and pollinating a flower]]

[[Hummingbird]]s and [[Ornithophily|ornithophilous]] (bird-pollinated) flowers have evolved a [[mutualism (biology)|mutualistic]] relationship. The flowers have [[nectar]] suited to the birds' diet, their color suits the birds' vision and their shape fits that of the birds' bills. The blooming times of the flowers have also been found to coincide with hummingbirds' breeding seasons. The floral characteristics of ornithophilous plants vary greatly among each other compared to closely related insect-pollinated species. These flowers also tend to be more ornate, complex, and showy than their insect pollinated counterparts. It is generally agreed that plants formed coevolutionary relationships with insects first, and ornithophilous species diverged at a later time. There is not much scientific support for instances of the reverse of this divergence: from ornithophily to insect pollination. The diversity in floral phenotype in ornithophilous species, and the relative consistency observed in bee-pollinated species can be attributed to the direction of the shift in pollinator preference.<ref>{{cite journal |last1=Kay |first1=Kathleen M.|last2=Reeves |first2=Patrick A. |last3=Olmstead |first3=Richard G. |last4=Schemske|first4=Douglas W. |s2cid=2991957|title=Rapid speciation and the evolution of hummingbird pollination in neotropical Costus subgenus Costus (Costaceae): evidence from nrDNA ITS and ETS sequences |journal=American Journal of Botany |date=2005 |volume=92 |issue=11|pages=1899–1910 |doi=10.3732/ajb.92.11.1899 |pmid=21646107|doi-access= }}</ref>

Flowers have converged to take advantage of similar birds.<ref name="Brown">{{cite journal |last1=Brown |first1=James H. |last2=Kodric-Brown |first2=Astrid |title=Convergence, Competition, and Mimicry in a Temperate Community of Hummingbird-Pollinated Flowers |s2cid=53604204 |journal=Ecology |year=1979 |volume=60 |issue=5 |pages=1022–1035 |doi=10.2307/1936870|jstor=1936870|bibcode=1979Ecol...60.1022B }}</ref> Flowers compete for pollinators, and adaptations reduce unfavourable effects of this competition. The fact that birds can fly during inclement weather makes them more efficient pollinators where bees and other insects would be inactive. Ornithophily may have arisen for this reason in isolated environments with poor insect colonization or areas with plants which flower in the winter.<ref name="Brown"/><ref>{{cite journal |last1=Cronk |first1=Quentin |last2=Ojeda |first2=Isidro |title=Bird-pollinated flowers in an evolutionary and molecular context |journal=Journal of Experimental Botany |date=2008 |volume=59 |issue=4 |pages=715–727 |doi=10.1093/jxb/ern009|pmid=18326865|doi-access=free }}</ref> Bird-pollinated flowers usually have higher volumes of nectar and higher sugar production than those pollinated by insects.<ref name="Stiles">{{cite journal |last=Stiles |first=F. Gary |title=Geographical Aspects of Bird Flower Coevolution, with Particular Reference to Central America |journal=Annals of the Missouri Botanical Garden |year=1981 |volume=68 |issue=2 |pages=323–351 |doi=10.2307/2398801 |jstor=2398801 |bibcode=1981AnMBG..68..323S |s2cid=87692272 |url=https://www.biodiversitylibrary.org/part/38387 }}</ref> This meets the birds' high energy requirements, the most important determinants of flower choice.<ref name="Stiles"/> In ''[[Mimulus]]'', an increase in red pigment in petals and flower nectar volume noticeably reduces the proportion of pollination by bees as opposed to hummingbirds; while greater flower surface area increases bee pollination. Therefore, red pigments in the flowers of ''Mimulus cardinalis'' may function primarily to discourage bee visitation.<ref>{{cite journal |last1=Schemske |first1=Douglas W. |last2=Bradshaw |first2=H.D. |title=Pollinator preference and the evolution of floral traits in monkeyflowers (''Mimulus'') |journal=Proceedings of the National Academy of Sciences |date=1999 |volume=96 |issue=21 |pages=11910–11915 |doi=10.1073/pnas.96.21.11910|pmid=10518550 |bibcode=1999PNAS...9611910S |pmc=18386|doi-access=free }}</ref> In ''[[Penstemon]]'', flower traits that discourage bee pollination may be more influential on the flowers' evolutionary change than 'pro-bird' adaptations, but adaptation 'towards' birds and 'away' from bees can happen simultaneously.<ref>{{cite journal |last1=Castellanos|first1=M. C. |last2=Wilson |first2=P. |last3=Thomson |first3=J.D. |title='Anti-bee' and 'pro-bird' changes during the evolution of hummingbird pollination in Penstemon flowers |journal=Journal of Evolutionary Biology |date=2005 |volume=17 |issue=4 |pages=876–885 |doi=10.1111/j.1420-9101.2004.00729.x |pmid=15271088|doi-access=free }}</ref> However, some flowers such as ''[[Heliconia angusta]]'' appear not to be as specifically ornithophilous as had been supposed: the species is occasionally (151 visits in 120 hours of observation) visited by ''[[Trigona]]'' stingless bees. These bees are largely pollen robbers in this case, but may also serve as pollinators.<ref>{{cite journal |last1=Stein |first1=Katharina |last2=Hensen |first2=Isabell |title=Potential Pollinators and Robbers: A Study of the Floral Visitors of Heliconia Angusta (Heliconiaceae) And Their Behaviour |journal=Journal of Pollination Ecology |date=2011 |volume=4 |issue=6 |pages=39–47|doi=10.26786/1920-7603(2011)7|doi-access=free }}</ref>

Following their respective breeding seasons, several species of hummingbirds occur at the same locations in [[North America]], and several hummingbird flowers bloom simultaneously in these habitats. These flowers have [[convergent evolution|converged]] to a common [[morphology (biology)|morphology]] and color because these are effective at attracting the birds. Different lengths and curvatures of the [[petal#Corolla|corolla]] tubes can affect the efficiency of extraction in hummingbird species in relation to differences in bill morphology. Tubular flowers force a bird to orient its bill in a particular way when probing the flower, especially when the bill and corolla are both curved. This allows the plant to place [[pollen]] on a certain part of the bird's body, permitting a variety of morphological [[co-adaptation]]s.<ref name="Stiles"/>

Ornithophilous flowers need to be conspicuous to birds.<ref name="Stiles"/> Birds have their greatest spectral sensitivity and finest hue discrimination at the red end of the [[visual spectrum]],<ref name="Stiles"/> so red is particularly conspicuous to them. Hummingbirds may also be able to see ultraviolet "colors". The prevalence of ultraviolet patterns and nectar guides in nectar-poor entomophilous (insect-pollinated) flowers warns the bird to avoid these flowers.<ref name="Stiles"/> Each of the two subfamilies of hummingbirds, the [[Phaethornithinae]] (hermits) and the [[Trochilinae]], has evolved in conjunction with a particular set of flowers. Most Phaethornithinae species are associated with large [[monocotyledon]]ous herbs, while the Trochilinae prefer [[dicotyledon]]ous plant species.<ref name="Stiles"/>
<!-- could extend examples of mutualism indefinitely - might mention fish/anemone [[cleaning symbiosis]] etc.
[[File:Common clownfish curves dnsmpl.jpg|thumb|[[Ocellaris clownfish]] and [[Heteractis magnifica|Ritter's sea anemones]] live together in a [[mutualism (biology)|mutual]] service-service symbiosis, the fish driving off butterfly fish and the anemone's tentacles protecting the fish from predators.]]
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