Hummingbirds and their flowers
About: This article is published in Journal of Ecology.The article was published on 1970-03-01. It has received 174 citations till now.
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TL;DR: It is shown that pollination syndromes provide great utility in understanding the mechanisms of floral diversification and the importance of organizing pollinators into functional groups according to presumed similarities in the selection pressures they exert.
Abstract: ▪ Abstract Floral evolution has often been associated with differences in pollination syndromes. Recently, this conceptual structure has been criticized on the grounds that flowers attract a broader spectrum of visitors than one might expect based on their syndromes and that flowers often diverge without excluding one type of pollinator in favor of another. Despite these criticisms, we show that pollination syndromes provide great utility in understanding the mechanisms of floral diversification. Our conclusions are based on the importance of organizing pollinators into functional groups according to presumed similarities in the selection pressures they exert. Furthermore, functional groups vary widely in their effectiveness as pollinators for particular plant species. Thus, although a plant may be visited by several functional groups, the relative selective pressures they exert will likely be very different. We discuss various methods of documenting selection on floral traits. Our review of the literatur...
1,813 citations
TL;DR: Honeybees and pollination guildes offer new means of assessing ecosystemic health because the species diversity and abundance relationship is changed from the log-normal standard expected from ecological principles and niche theory.
442 citations
Cites background from "Hummingbirds and their flowers"
...…flowers that are effectively pollinated by a wide diversity of animals (Waser et al., 1996) along with many that are special, with restricted assemblages of potential pollinators (Grant and Grant, 1965, 1968; Hurd and Linsley, 1975; Faegri and van der Pijl, 1979; Vogel, 1990; Proctor et al., 1996)....
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TL;DR: The results do not support the hybrid origin of P. spectabilis, but do support the hypothesis that P. clevelandii is a diploid hybrid species derived from P. centranthifolius, and demonstrate that pollen‐mediated gene flow via hummingbird vectors is prevalent in the hybrid complex.
Abstract: Inferences regarding hybridization rely on genetic markers to differentiate parental taxa from one another. Intersimple sequence repeat (ISSR) markers are based on single-primer PCR reactions where the primer sequence is derived from di- and trinucleotide repeats. These markers have successfully been used to assay genetic variability among cultivated plants, but have not yet been tested in natural populations. We used genetic markers generated from eight ISSR primers to examine patterns of hybridization and purported examples of hybrid speciation in Penstemon (Scrophulariaceae) in a hybrid complex involving P. centranthifolius, P. grinnellii, P. spectabilis and P. clevelandii. This hybrid complex has previously been studied using three molecular data sets (allozymes, and restriction-site variation of nuclear rDNA and chloroplast DNA). These studies revealed patterns of introgression involving P. centranthifolius, but were unsuccessful in determining whether gene flow occurs among the other species, and support for hypotheses of diploid hybrid speciation was also lacking. In this study, we were able to fingerprint each DNA accession sampled with one to three ISSR primers and most accessions could be identified with a single primer. We found population- and species-specific markers for each taxon surveyed. Our results: (i) do not support the hybrid origin of P. spectabilis; (ii) do support the hypothesis that P. clevelandii is a diploid hybrid species derived from P. centranthifolius and P. spectabilis; and (iii) demonstrate that pollen-mediated gene flow via hummingbird vectors is prevalent in the hybrid complex.
416 citations
Cites background from "Hummingbirds and their flowers"
...The pattern of pollen-mediated gene flow discussed previously (Wolfe & Elisens 1995) matches hummingbird migrational patterns throughout southern California (Grant & Grant 1968), which are largely along an elevational gradient as the flowering season progresses....
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...A distance matrix was generated from the raw data matrix of 1s and 0s by using a computer program written by Vera Ford (unpublished; University of California, Davis)....
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...Background on Penstemon hybrid complex Two examples of diploid hybrid speciation proposed by Straw (1955a,b, 1956a,b) involved four species of Penstemon with distributions in southern California....
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TL;DR: Unequivocal examples of dominance-mediated niche relationships are thus far confined to certain vertebrate and arthropod groups, although evidence available suggests that they are more widely spread.
Abstract: If one species is socially dominant to another, the subordinate usually narrows its niche when they occur together. When one species is dominant in some circumstances and a second in others, both narrow their niches when together. Subordinates usually have a larger fundamental niche than their dominants. The presence of dominants should result in selection for enlarged (or changed) fundamental niches by the subordinate species. Linear hierarchies of species should result in guilds whose members have different-sized fundamental and realized niches. Though large mobile species often have greater fundamental niches than small similar species, an inverse relationship between size and niche breadth usually occurs where clear dominance hierarchies exist, suggesting that social dominance has more than counteracted the effect of body size. The presence of dominants is a factor making conditions uncertain for subordinates. Limits to the niche breadth of dominants are in some cases directly set by physical factors ...
330 citations
TL;DR: 13 nonexclusive hypotheses that may contribute to the observed frequency distribution of fruit colors are presented and a preliminary assessment of these hypotheses is made, in a preliminary way, using existing information.
Abstract: Red and black are the most common colors of bird-dispersed fruits in all regions of the world for which information is available; other colors occur, but at lower frequencies. We present 13 nonexclusive hypotheses that may contribute to the observed frequency distribution of fruit colors and assess them, in a preliminary way, using existing information. Five hypotheses relate fruit colors directly to avian foraging: (1) birds prefer red and black (weak support at best); (2) red and black displays are more readily discovered by foraging birds (mixed evidence); (3) fruit colors indicate fruit maturity (mixed evidence); (4) fruit colors facilitate quick recognition of food (little evidence); (5) nutritionally poor fruits mimic nutrient-rich fruits (no data). Three hypotheses relate fruit colors to defense against natural enemies: (6) red fruits are inconspicuous to fruit-foraging arthropods (limited applicability); (7) fruit colors exclude poor dispersal agents (few data); (8) fruit pigments defend fruits ag...
311 citations
Cites background from "Hummingbirds and their flowers"
...Grant (1966) and Grant and Grant (1968) suggested that the red coloration of hummingbird flowers is favored because of the advantages of quick identification, especially by migrant hummingbirds....
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...…situation appears to occur in flower-visiting birds: although many hummingbird flowers are red, hummingbirds do not seem to prefer red (Grant 1966; Grant and Grant 1968) and can readily be trained to visit flowers of other colors (Grant and Grant 1968; Stiles 1976; Goldsmith and Goldsmith 1979)....
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