Editing Rubiaceae (section)

==Ecology==

===Flower biology===
Most members of the Rubiaceae are [[zoophily|zoophilous]], pollinated mainly by insects. [[Entomophily|Entomophilous]] species produce nectar from an [[epigynous]] disk at the base of the [[corolla tube]] to attract insects. [[Ornithophily]] is rare and is found in red-flowered species of ''[[Alberta magna|Alberta]]'', ''[[Bouvardia]]'', and ''[[Burchellia]]''. [[Anemophily|Anemophilous]] species are found in the tribes [[Anthospermeae]] and [[Theligoneae]] and are characterized by hermaphroditic or unisexual flowers that exhibit a set of specialized features, such as striking sexual dimorphism, increased receptive surface of the [[stigma (botany)|stigmas]] and [[pendulous]] [[anthers]].<ref name="Robbrecht1988"/>

Although most Rubiaceae species are hermaphroditic, [[outbreeding]] is promoted through [[proterandry|sequential hermaphroditism]] and spatial isolation of the reproductive organs. More complex reproductive strategies include secondary pollen presentation, [[heterostyly]], and unisexual flowers.

Secondary pollen presentation (also known as stylar pollen presentation or ixoroid pollen mechanism) is especially known from the [[Gardenieae]] and related tribes. The flowers are proterandrous and the pollen is shed early onto the outside of the stigmas or the upper part of the style, which serve as a pollen receptacle. Increased surface area and irregularity of the pollen receptacle, caused by swellings, hairs, grooves or ridges often ensure a more efficient pollen deposition. After elongation of the style, animals transport the pollen to flowers in the female or receptive stage with exposed stigmatic surfaces. A pollen catapult mechanism is present in the genera ''[[Molopanthera]]'' and ''[[Posoqueria]]'' (tribe [[Posoquerieae]]) that projects a spherical pollen mass onto visiting [[Sphingidae|hawk moths]].<ref name="Delprete2009"/>

Heterostyly is another mechanism to avoid inbreeding and is widely present in the family Rubiaceae.<ref name="Anderson1973"/> The tribes containing the largest number of heterostylous species are [[Spermacoceae]] and [[Psychotrieae]]. Heterostyly is absent in groups that have secondary pollen presentation (e.g. [[Vanguerieae]]).

Unisexual flowers also occur in Rubiaceae and most taxa that have this characteristic are [[dioecy|dioecious]]. The two flower morphs are however difficult to observe as they are rather morphologically similar; male flowers have a [[pistillode|rudimentary pistil]] with the ovaries empty and female flowers [[staminode|sterile or rudimentary stamens]] with empty anthers.<ref name="Robbrecht1988"/> Flowers that are morphologically hermaphrodite, but functionally dioecious occur in ''[[Pyrostria]]''.<ref name="Bridson1987"/>

=== Fruit biology ===
The dispersal units in Rubiaceae can be entire fruits, syncarps, mericarps, pyrenes or seeds. Fleshy fruit taxa are probably all (endo)zoochorous (e.g. tribes [[Pavetteae]], [[Psychotrieae]]), while the dispersal of dry fruits is often unspecialized (e.g. tribes [[Knoxieae]], [[Spermacoceae]]). When seeds function as [[Diaspore (botany)|diaspores]], the dispersal is either anemochorous or hydrochorous. The three types of wind-dispersed diaspores in Rubiaceae are dust seeds (rare, e.g. ''[[Lerchea]]''), plumed seeds (e.g. ''[[Hillia (plant)|Hillia]]''), and winged seeds (e.g. ''[[Coutarea]]''). Long-distance dispersal by ocean currents is very rare (e.g. the seashore tree ''[[Guettarda speciosa]]''). Other dispersal mechanisms are absent or at least very rare. Some [[Spermacoceae]] having seeds with [[elaiosome]]s are probably myrmecochorous (e.g. ''[[Spermacoce hepperiana]]''). Epizoochorous taxa are limited to herbaceous Rubiaceae (e.g. ''[[Galium aparine]]'' fruits are densely covered with hooked bristly hairs).

=== Associations with other organisms ===
The genera ''[[Anthorrhiza]]'', ''[[Hydnophytum]]'', ''[[Myrmecodia]]'', ''[[Myrmephytum]]'', and ''[[Squamellaria]]'' are succulent [[epiphyte]]s that have evolved a [[mutualism (biology)|mutualistic]] relationship with ants. Their [[hypocotyl]] grows out into an ant-inhabited tuber.<ref name="Kapitany2007"/> Some shrubs or trees have ant holes in their stems (e.g. ''[[Globulostylis]]'').<ref name="Verstraete2013b"/> Some Rubiaceae species have domatia that are inhabited by mites (viz. [[acarodomatia]]; e.g. ''[[Plectroniella armata]]'').<ref name="Tilney2012"/>

An intimate association between bacteria and plants is found in three rubiaceous genera (viz. ''[[Pavetta]]'', ''[[Psychotria]]'', and ''[[Sericanthe]]'').<ref name="Lemaire2011"/> The presence of endophytic bacteria is visible by eye because of the formation of dark spots or nodules in the leaf blades. The endophytes have been identified as ''[[Burkholderia]]'' bacteria. A second type of bacterial leaf symbiosis is found in the genera ''[[Fadogia]]'', ''[[Fadogiella]]'', ''[[Globulostylis]]'', ''[[Rytigynia]]'', and ''[[Vangueria]]'' (all belonging to the tribe [[Vanguerieae]]),<ref name="Verstraete2011"/><ref name="Verstraete2013a"/><ref name="Verstraete2013c"/> and in some species of ''[[Empogona]]'' and ''[[Tricalysia]]'' (both belonging to the tribe [[Coffeeae]]),<ref name="Verstraete2023"/> where ''[[Burkholderia]]'' bacteria are found freely distributed among the mesophyll cells and no leaf nodules are formed. The hypothesis regarding the function of the symbiosis is that the endophytes provide chemical protection against herbivory by producing certain toxic secondary metabolites.<ref name="Sieber2015"/>