The openness of a flower and its number of flower‐visitor species

Abstract

Using a sample of 1,403 flowering plant species, we tested the hypothesis that flower openness and flower‐visitor generalization level of a plant species correlate positively. The “flower‐visitor generalization level” Ln of a flowering plant species n, here defined as number of flower‐visiting animal species attracted to the flowers of n in a given study site, varied enormously among plant species. Its frequency distribution was extremely skewed. Within a study site, L also increased with number of flower‐visitor species A. In order to correct for this, we expressed L relatively, as the proportion of the total flower‐visitor fauna in a study site that visited a given plant species (relative generalization level, L/A). We listed the top‐10 most generalized species (both according to L and L/A) in the “world”, i.e., out of our sample of 1,403 plant species. Flower openness is defined as accessibility to the interior of the flower. We placed the blossom classes of Fægri & van der Pijl along a gradient, albeit not very well defined, of decreasing flower openness (dish‐bowl, bell‐funnel, head‐brush, tube, gullet, flag) and tested for any relationship to their generalization level. The classes differed slightly but significantly in their level of L/A. Tube, bell‐funnel, and dish‐bowl had the highest generalization level and flag, gullet, and head‐brush the lowest. Thus, flower openness and generalization level were not correlated. We discuss other factors influencing generalization level such as accessibility to pollen and nectar, morphology and behavior of visitor, and species diversity of the different functional types of visitors.

Myophily in the critically endangered umbelliferous plant Ostericum palustre Besser (Apiaceae)

“…Different letters placed above the mean indicate statistically significant differences at P \ 0.05 (Kruskal-Wallis tests for multiple comparisons). Vesp Vespidae, LS large Syrphids, SS small Syrphids, LM large Muscoid flies, MM medium Muscoid flies (Faegri and van der Pijl 1966), and, as such, may be easily visited by a wide spectrum of insects, and are thus phenotypically generalized (Ollerton et al 2007). Indeed, our study showed that they are attractive to over 81 species of anthophilous insects, a result comparable to that found in many other members of the family (Knuth 1898; Corbet 1970; Grace and Nelson 1981;Ellis and Ellis-Adam 1993;Zych 2002Zych , 2007Zych et al 2007;Niemirski and Zych 2011).…”

“…Although umbellifers are generally regarded as generalists in terms of their floral visitors (Corbet 2006;Olesen et al 2007;Ollerton et al 2007), fly-pollination [myophily, as described in Willmer (2011), p. 308], is probably typical of Apiaceae (Proctor et al 1996;Zych 2004) and, to date, has been reported for many other European members of this family (Grace and Nelson 1981;Zych 2002Zych , 2007Niemirski and Zych 2011), including O. palustre. Diptera are also important pollinators of umbellifers on remote islands (Pérez-Bañón et al 2007), and on other continents (e.g.…”

“…Ollerton et al 2007;Zych 2007;Jacobs et al 2010;Niemirski and Zych 2011) is characterized by a high apparent generalization, but by low realized generalization, and is an example of a functional specialist (see Fenster et al 2004;Ollerton et al 2007 for discussion), since it is pollinated by a relatively small group of potential pollinators grouped together on morphological grounds into visitor guilds. Thus, O. palustre is one more example of Apiaceae being masters of the ''bethedging'' pollination strategy (sensu Willmer 2011) in that, although its flowers are mainly pollinated by large Syrphid and Muscoid flies, they nonetheless remain attractive to many pollinator groups (wasps in this case).…”

“…It is generally described as zoogamous (Czarna and Załuski 2001;Załuski 2004), but we failed to find any information relating to its pollination system in the literature. Being a member of the Apiaceae and producing open and unrestricted flowers that are easily accessible to a vast array of potential pollinators, this plant can perhaps, based on its pollination systems, be considered as an ecological and functional generalist (Ollerton et al 2007). In fact, many umbelliferous plants are reported to be visited by dozens or even hundreds of anthophilous insect species (Knuth 1898; Ellis-Adam 1993, 1994;Zych et al 2007), and according to Corbet (2006), the whole family could be regarded as ''morphologically specialized for ecological generalization''.…”

Non-naturalized alien plants receive fewer flower visits than naturalized and native plants in a Swiss botanical garden

“…Therefore, we also tested among our naturalized alien species, whether the ones that occur more frequently in Switzerland attract more flower visitors. Because effective pollen transfer is most likely determined by the number of insect visits, the duration of each visit and the diversity of flower visitors (Herrera, 1989;Ollerton et al, 2007;Vázquez et al, 2005), we assessed these different parameters.…”