Removal Effects on Nectar Production in Bat‐pollinated Flowers of the Brazilian Cerrado

We tested the removal effect on nectar production in four bat‐pollinated cerrado flowers. We compared the amount of nectar after 7–12 removals with the accumulated nectar in non‐manipulated flowers after 12 h. In all, but one species, removals increased volume by 1.5–4.6 times and sugar content by 1.6–4 times, which may affect flower visitation by bats, pollen flow, and reproduction. Abstract in Portuguese is available in the online version of this article.     

Reproductive biology of a hummingbird‐pollinated Billbergia: light influence on pollinator behaviour and specificity in a Brazilian semi‐deciduous forest

• Ornithophily has evolved in parallel several times during evolution of angiosperms. Bird pollination is reported for 65 families, including Bromeliaceae. One of the most diverse bromeliad is Billbergia, which comprises species pollinated mainly by hummingbirds.
• Based on investigations on flowering phenology, morpho‐anatomy, volume and concentration of nectar, pollinators and breeding system, this paper explores the reproductive biology and pollinator specificity of B. distachia in a mesophytic semi‐deciduous forest of southeastern Brazil.
• The results have show that B. distachia is pollinated by a single species of hermit hummingbird, Phaethornis eurynome, which search for nectar produced by a septal nectary, where the secretory tissue is located above the placenta. The species is self‐incompatible. The combination of pollinator specificity, due to long corolla tubes that exclude visitation of short‐billed hummingbirds, complete self‐incompatibility and non‐territorial behaviour of pollinators, it is very important to reduce pollen loss and increase gene flow within population.
• Our results indicate that studies on pollination biology and reproduction are essential to understand the evolutionary history of pollination systems of plants since, at least in Billbergia, variation in the pollinator spectrum has been recorded for different habitats among Brazilian forests. Furthermore, according to our data, foraging of Phaethornis on flowers is independent of air temperature and humidity, while the main factor influencing hummingbird visitation is daylight. Considering current knowledge on climatic parameters influencing hummingbird foraging, pollination and reproductive biology of Neotropical flora and environment of the hermit hummingbird in tropical forests, new insights on plant–pollinator interaction are provided.

     

Floral antagonists counteract pollinator‐mediated selection on attractiveness traits in the hummingbird‐pollinated Collaea cipoensis (Fabaceae)

Pollinator‐mediated selection toward larger and abundant flowers is common in naturally pollen‐limited populations. However, floral antagonists may counteract this effect, maintaining smaller‐ and few‐flowered individuals within populations. We quantified pollinator and antagonist visit rates and determined a multiplicative female fitness component from attacked and non‐attacked flowers of the Brazilian hummingbird‐pollinated shrub Collaea cipoensis to determine the selective effects of pollinators and floral antagonists on flower size and number. We predicted that floral antagonists reduce the female fitness component and thus exert negative selective pressures on flower size and number, counteracting the positive effects of pollinators. Pollinators, mainly hummingbirds, comprised 4% of total floral visitation, whereas antagonist ants and bees accounted for 90% of visitation. Nectar‐robbers involved about 99% of floral antagonist visit rates, whereas florivores comprised the remaining 1%. Larger and abundant flowers increased both pollinator and antagonist visit rates and the female fitness component significantly decreased in flowers attacked by nectar‐robbers and florivores in comparison to non‐attacked flowers. We detected that pollinators favored larger‐ and many‐flowered individuals, whereas floral antagonists exerted negative selection on flower size and number. This study confirms that floral antagonists reduce female plant fitness and this pattern directly exerts negative selective pressures on flower size and number, counteracting pollinator‐mediated selection on floral attractiveness traits.     

Confirmed mixed bird–insect pollination system of Scrophularia trifoliata L., a Tyrrhenian species with corolla spots

• Both bird and mixed vertebrate–insect (MVI) pollination systems are very rare in Europe and the Mediterranean region. Because MVI can ensure reproduction over a wider range of environmental conditions than when insects are the sole pollinators, under certain circumstances such systems are highly advantageous to plants. Here, we investigated the pollination and some reproductive traits of the Tyrrhenian Scrophularia trifoliata, the only species of the genus possessing two showy dark spots inside the corolla, for which MVI pollination system had been inferred on the basis of limited censuses.
• We conducted field experiments to study MVI pollination and some reproductive traits and elucidate the role of corolla spots, analysing their ultraviolet pattern, histology and pigments versus the rest of the corolla.
• The primary pollinators were wasps and passerine birds. Corolla spots absorb UV light, present abundant anthocyanins and are histologically identical to the rest of the corolla. Control flowers had higher visitation frequency than flowers without spots. S. trifoliata is self‐compatible, with efficient intrafloral protogyny and herkogamy that prevent self‐pollination but not geitonogamy.
• We confirmed the existence of a mixed bird–insect pollination system in S. trifoliata. This system is found in three other Scrophularia species with large, showy flowers – two Mediterranean (S. grandiflora and S. sambucifolia) and one Macaronesian (S. calliantha). Unlike those species, S. trifoliata has two large spots inside the corolla. These likely operate as nectar guides and their dark colouration is related to abundant anthocyanin content.

     

Pollinator‐mediated selection in a specialized hummingbird–Heliconia system in the Eastern Caribbean

Phenotypic matches between plants and their pollinators often are interpreted as examples of reciprocal selection and adaptation. For the two co‐occurring plant species, Heliconia bihai and H. caribaea in the Eastern Caribbean, we evaluated for five populations over 2 years the strength and direction of natural selection on corolla length and number of bracts per inflorescence. These plant traits correspond closely to the bill lengths and body masses of their primary pollinators, female or male purple‐throated carib hummingbirds (Eulampis jugularis). In H. bihai, directional selection for longer corollas was always significant with the exception of one population in 1 year, whereas selection on bract numbers was rare and found only in one population in 1 year. In contrast, significant directional selection for more bracts per inflorescence occurred in all three populations of the yellow morph and in two populations of the red morph of H. caribaea, whereas significant directional selection on corolla length occurred in only one population of the red morph and one population of the yellow morph. Selection for longer corollas in H. bihai may result from better mechanical fit, and hence pollination, by the long bills of female E. jugularis, their sole pollinator. In contrast, competition between males of E. jugularis for territories may drive selection for more bracts in H. caribaea. Competitive exclusion of female E. jugularis by territorial males also implicates pollinator competition as a possible ecological mechanism for trait diversification in these plants.     

Pollen analogues are transported across greater distances in bee‐pollinated than in hummingbird‐pollinated species of Justicia (Acanthaceae)

Several hummingbird‐pollinated plant lineages have been demonstrated to show increased rates of diversification compared to related insect‐pollinated lineages. It has been argued that this pattern is produced by a higher degree of specialization on part of both hummingbirds and plants. We here test an alternative hypothesis: The often highly territorial hummingbirds may on average carry pollen over shorter distances than other pollinators and drive diversification by reducing gene flow distances. We present experimental data from pollen analogue tracking showing shorter dispersal distances in hummingbird‐pollinated than in bee‐pollinated species among ten Neotropical species of Justicia (Acanthaceae). Abstract in Spanish is available with online material.     

Sexual dimorphism in the andromonoecious Euphorbia nicaeensis: effects of gender and inflorescence development

BACKGROUND AND AIMS: In andromonoecious taxa with separate floral types along the inflorescence, architectural or plastic effects can simulate floral sexual dimorphism. Both the primary and secondary sexual characteristics of the cyathia of the protogynous andromonoecious species Euphorbia nicaeensis were analysed according to their sex and arrangement on the inflorescence. METHODS: The production of male and hermaphrodite cyathia at each inflorescence level was surveyed in two natural populations. The longevity, size, pollen production and viability, and nectar secretion of both types of cyathia were checked between inflorescence levels and between sexes at the only level at which they occur together. This sampling method makes it possible to know whether differences between cyathia types are based on sex or are attributable to inflorescence development. KEY RESULTS: Male cyathia were produced predominantly at the first and second inflorescence levels, whereas at levels 3-5, the cyathia were almost exclusively hermaphrodite. Viable pollen production by male cyathia at the second inflorescence level was higher than that of hermaphrodite cyathia at the third level but, when males and hermaphrodites at the same level were compared, their pollen production was similar. Male and hermaphrodite cyathia were similar in size, irrespective of the inflorescence level, although the exclusively hermaphrodite cyathia of the last level were smaller. Both cyathium types produced similar amounts of sugar. However, male cyathia produced nectar during their whole lifespans, whereas hermaphrodites produced it exclusively during their male phase. Moreover, the nectary activity of male cyathia started earlier in the day than that of hermaphrodites. CONCLUSIONS: An apparent floral dimorphism exists in the primary sexual characteristics of Euphorbia nicaeensis because differences in pollen production between cyathium types are due to theirs positions. Similarly, differences affecting most secondary sexual characteristics are only apparent between the two cyathium types. However, E. nicaeensis shows a true but slight floral dimorphism in some of the secondary sex characters related to nectar secretion. The lack of nectar production by the female phase of the hermaphrodite cyathia of E. nicaeensis indicates that this is a deceit-pollinated species.     

Interglacial genetic diversification of Moussonia deppeana (Gesneriaceae), a hummingbird‐pollinated,cloud forest shrub in northern Mesoamerica

Recent empirical work on cloud forest‐adapted species supports the role of both old divergences across major geographical areas and more recent divergences attributed to Pleistocene climate changes. The shrub Moussonia deppeana is distributed in northern Mesoamerica, with geographically disjunct populations. Based on sampling throughout the species range and employing plastid and nuclear markers, we (i) test whether the fragmented distribution is correlated with main evolutionary lineages, (ii) reconstruct its phylogeographical history to infer the history of cloud forest in northern Mesoamerica and (iii) evaluate a set of refugia/vicariance scenarios for the region and demographic patterns of the populations whose ranges expanded and tracked cloud forest conditions during the Last Glacial Maximum. We found a deep evolutionary split in M. deppeana about 6–3 Ma, which could be consistent with a Pliocene divergence. Comparison of variation in plastid and nuclear markers revealed several lineages mostly congruent with their isolated geographical distribution and restricted gene flow among groups. Results of species distribution modelling and coalescent simulations fit a model of multiple refugia diverging during interglacial cycles. The demographic history of M. deppeana is not consistent with an expanding–contracting cloud forest archipelago model during the Last Glacial Maximum. Instead, our data suggest that populations persisted across the geographical range throughout the glacial cycles, and experienced isolation and divergence during interglacial periods.     

Effects of Inbreeding,Outbreeding, and Supplemental Pollen on the Reproduction of a Hummingbird‐pollinated Clonal Amazonian Herb

Understory herbs are an essential part of tropical rain forests, but little is known about factors limiting their reproduction. Many of these herbs are clonal, patchily distributed, and produce large floral displays of nectar‐rich 1‐d flowers to attract hummingbird pollinators that may transport pollen over long distances. The aim of this study was to investigate the effects of clonality, cross‐proximity, and patchy distribution on the reproduction of the hummingbird‐pollinated Amazonian herb Heliconia metallica. We experimentally pollinated flowers within populations with self‐pollen and with pollen of different diversity, crossed flowers between populations, and added supplemental pollen to ramets growing solitarily or in conspecific patches. Only flowers pollinated early in the morning produced seeds. Selfed flowers produced seeds, but seed number and mass were strongly reduced, suggesting partial sterility and inbreeding depression after selfing. Because of pollen competition, flowers produced more seeds after crosses with several than with single donor plants. Crosses between populations mostly resulted in lower seed production than those within populations, suggesting outbreeding depression. Ramets in patches produced fewer seeds than solitary ramets and were more pollen‐limited, possibly due to geitonogamy and biparental inbreeding in patches. We conclude that high rates of geitonogamy due to clonality and pollen limitation due to the short receptivity of flowers and patchy distribution constrain the reproduction of this clonal herb. Even in unfragmented rain forests with highly mobile pollinators, outbreeding depression may be a widespread phenomenon in plant reproduction.     

Species‐specific responses to combined water stress and increasing temperatures in two bee‐pollinated congeners (Echium,Boraginaceae)

1. Water stress and increasing temperatures are two main constraints faced by plants in the context of climate change. These constraints affect plant physiology and morphology, including phenology, floral traits, and nectar rewards, thus altering plant–pollinator interactions.
2. We compared the abiotic stress responses of two bee‐pollinated Boraginaceae species, Echium plantagineum, an annual, and Echium vulgare, a biennial. Plants were grown for 5 weeks during their flowering period under two watering regimes (well‐watered and water‐stressed) and three temperature regimes (21, 24, 27°C).
3. We measured physiological traits linked to photosynthesis (chlorophyll content, stomatal conductance, and water use efficiency), and vegetative (leaf number and growth rate) and floral (e.g., flower number, phenology, floral morphology, and nectar production) traits.
4. The physiological and morphological traits of both species were affected by the water and temperature stresses, although the effects were greater for the annual species. Both stresses negatively affected floral traits, accelerating flower phenology, decreasing flower size, and, for the annual species, decreasing nectar rewards. In both species, the number of flowers was reduced by 22%–45% under water stress, limiting the total amount of floral rewards.
5. Under water stress and increasing temperatures, which mimic the effects of climate change, floral traits and resources of bee‐pollinated species are affected and can lead to disruptions of pollination and reproductive success.

     

Reproduction in an Orchid Can Be Resource‐Limited over its Lifetime1

Most orchids studied thus far show long‐term resource adjustments to increases in fruit production within a flowering season, but none of these offers rewards to their potential pollinators. If nectar production is energetically expensive, then resources utilized to produce fruits and seeds may be even more limited in pollinator‐rewarding orchids than in non‐rewarding ones. Thus, resource adjustments may be more dramatic or entirely different in nectar producing plants. In this study, we performed artificial hand‐pollinations for two consecutive flowering seasons in die nectar producing orchid Comparettia falcata, and tested whether or not fruit set, seed set, and seed viability were limited by the quantity of pollinations or by resources. In addition, we compared mechanisms of short‐term (fruit abortion within seasons) and long‐term consequences (percent change in leaf length and change in flower number per plant between seasons, probability of shoot and inflorescence production, and mortality) between hand‐ pollinated and unmanipulated plants. The relationships among plant traits related to vegetative size and reproduction also were examined. Hand‐pollinations showed some negative effects. Fruit set was higher in hand‐pollinated plants in the first season but was similar to the controls in the second. Seed set was significantly lower and abortions were higher than in unmanipulated plants. On the other hand, some of our measurements were unaffected by die hand‐pollination treatment. Unexpectedly, there were no significant differences between groups in percent change in leaf length, change in flower number per plant between seasons, or die probability of shoot and inflorescence production. Although there was a strong correlation between leaf size and die number of flowers produced within a season, associations between leaf size and traits related to current or future reproduction were not consistent. Like other epiphytic orchids, pollination limitation occurred within a single season in C. falcata., but increases in fruit production also resulted in reduced lifetime fitness as estimated by a compounded fitness index. Contrary to all other epiphytic orchids studied, long‐term adjustments to increased fruit production in C. falcata through reduction in future growth or flower and inflorescence production were either minor or lacking. Our results suggest that the nature of plant strategies associated with resource constraints during sexual reproduction may be dependent on whether or not plants have evolved traits that are costly.     

Mixed hummingbird: Long‐proboscid‐fly pollination in ‘ornithophilous’Embothrium coccineum (Proteaceae) along a rainfall gradient in Patagonia,Argentina

Abstract The pollination ecology of eight populations of the tree Embothrium coccineum was studied along a steep rainfall gradient in NW Patagonia, Argentina. The showy red flowers suggest an ornithophilous pollination syndrome and they have been reported to attract hummingbirds in Argentina and hummingbirds and passerines in Chile. At each population, flower visitors were recorded and floral rewards were analysed. We found a highly significant increase in nectar concentration towards the drier end of the gradient, but this change was not related to the turnover of species in the flower‐visitor assemblage of E. coccineum. In addition to the hummingbird Sephanoides sephaniodes (Green‐Backed Firecrown, Trochilidae) which is widespread throughout the temperate forest at this latitude, other species seem to be locally important as pollinators of E. coccineum in some sites in Argentina (e.g. two long‐tongued tanglewing flies (Nemestrinidae) of the genus Trichophthalma). The long‐dated occurrence of tanglewing flies in South America, relative to the more modern hummingbirds, suggests that ornithophily may be a derived character in E. coccineum, the ancestral condition being pollination by Nemestrinidae.     

Patterns of MHC‐dependent mate selection in humans and nonhuman primates: a meta‐analysis

Genes of the major histocompatibility complex (MHC) in vertebrates are integral for effective adaptive immune response and are associated with sexual selection. Evidence from a range of vertebrates supports MHC‐based preference for diverse and dissimilar mating partners, but evidence from human mate choice studies has been disparate and controversial. Methodologies and sampling peculiarities specific to human studies make it difficult to know whether wide discrepancies in results among human populations are real or artefact. To better understand what processes may affect MHC‐mediated mate choice across humans and nonhuman primates, we performed phylogenetically controlled meta‐analyses using 58 effect sizes from 30 studies across seven primate species. Primates showed a general trend favouring more MHC‐diverse mates, which was statistically significant for humans. In contrast, there was no tendency for MHC‐dissimilar mate choice, and for humans, we observed effect sizes indicating selection of both MHC‐dissimilar and MHC‐similar mates. Focusing on MHC‐similar effect sizes only, we found evidence that preference for MHC similarity was an artefact of population ethnic heterogeneity in observational studies but not among experimental studies with more control over sociocultural biases. This suggests that human assortative mating biases may be responsible for some patterns of MHC‐based mate choice. Additionally, the overall effect sizes of primate MHC‐based mating preferences are relatively weak (Fisher's Z correlation coefficient for dissimilarity Zr = 0.044, diversity Zr = 0.153), calling for careful sampling design in future studies. Overall, our results indicate that preference for more MHC‐diverse mates is significant for humans and likely conserved across primates.     

Euphorbiasteroid,a component of Euphorbia lathyris L., inhibits adipogenesis of 3T3‐L1 cells via activation of AMP‐activated protein kinase

The purpose of this study is to investigate the effects of euphorbiasteroid, a component of Euphorbia lathyris L., on adipogenesis of 3T3‐L1 pre‐adipocytes and its underlying mechanisms. Euphorbiasteroid decreased differentiation of 3T3‐L1 cells via reduction of intracellular triglyceride (TG) accumulation at concentrations of 25 and 50 μM. In addition, euphorbiasteroid altered the key regulator proteins of adipogenesis in the early stage of adipocyte differentiation by increasing the phosphorylation of AMP‐activated protein kinase (AMPK) and acetyl‐CoA carboxylase. Subsequently, levels of adipogenic proteins, including fatty acid synthase, peroxisome proliferator‐activated receptor‐γ and CCAAT/enhancer‐binding protein α, were decreased by euphorbiasteroid treatment at the late stage of adipocyte differentiation. The anti‐adipogenic effect of euphorbiasteroid may be derived from inhibition of early stage of adipocyte differentiation. Taken together, euphorbiasteroid inhibits adipogenesis of 3T3‐L1 cells through activation of the AMPK pathway. Therefore, euphorbiasteroid and its source plant, E. lathyris L., could possibly be one of the fascinating anti‐obesity agent. Copyright © 2015 John Wiley & Sons, Ltd.     

Nectary and gender‐biased nectar production in dichogamous Chamaenerion angustifolium (L.) Scop. (Onagraceae)

In dichogamous plants, nectar characteristics (i.e. nectar amount and its composition) can differ between sexual phases. In the present study, we investigated the structural organization of the floral nectary, nectar production and carbohydrate composition in the protandrous Chamaenerion angustifolium (L.) Scop. (Onagraceae). The receptacular nectary consisted of an epidermis with numerous nectarostomata, several layers of photosynthetic secretory parenchyma, and subsecretory parenchyma. Nectariferous tissue was not directly vascularized and starch grains were rarely observed in the secretory cells, occurring exclusively in the guard cells of modified stomata. The nectar was released via nectarostomata. The floral nectar was hexose rich (32.8/39.1/28.1% glucose/fructose/sucrose) and the total concentration was constant throughout the anthesis (47% on average). However, contrasting patterns in nectar amount and carbohydrate composition between the floral sexual phases were observed. On average, female‐phased flowers produced 1.4‐fold more nectar than male‐phased flowers, and although the nectar was sucrose rich during the male phase, it was hexose rich during the female phase, suggesting sucrose hydrolysis.     

Ejaculate investment and attractiveness in the stalk‐eyed fly,Diasemopsis meigenii

The phenotype‐linked fertility hypothesis proposes that male fertility is advertised via phenotypic signals, explaining female preference for highly sexually ornamented males. An alternative view is that highly attractive males constrain their ejaculate allocation per mating so as to participate in a greater number of matings. Males are also expected to bias their ejaculate allocation to the most fecund females. We test these hypotheses in the African stalk‐eyed fly, Diasemopsis meigenii. We ask how male ejaculate allocation strategy is influenced by male eyespan and female size. Despite large eyespan males having larger internal reproductive organs, we found no association between male eyespan and spermatophore size or sperm number, lending no support to the phenotype‐linked fertility hypothesis. However, males mated for longer and transferred more sperm to large females. As female size was positively correlated with fecundity, this suggests that males gain a selective advantage by investing more in large females. Given these findings, we consider how female mate preference for large male eyespan can be adaptive despite the lack of obvious direct benefits.     

The complexity of mating decisions in stalk‐eyed flies

All too often, studies of sexual selection focus exclusively on the responses in one sex, on single traits, typically those that are exaggerated and strongly sexually dimorphic. They ignore a range of less obvious traits and behavior, in both sexes, involved in the interactions leading to mate choice. To remedy this imbalance, we analyze a textbook example of sexual selection in the stalk‐eyed fly (Diasemopsis meigenii). We studied several traits in a novel, insightful, and efficient experimental design, examining 2,400 male–female pairs in a “round‐robin” array, where each female was tested against multiple males and vice versa. In D. meigenii, females exhibit strong mate preference for males with highly exaggerated eyespan, and so we deliberately constrained variation in male eyespan to reveal the importance of other traits. Males performing more precopulatory behavior were more likely to attempt to mate with females and be accepted by them. However, behavior was not a necessary part of courtship, as it was absent from over almost half the interactions. Males with larger reproductive organs (testes and accessory glands) did not make more mating attempts, but there was a strong tendency for females to accept mating attempts from such males. How females detect differences in male reproductive organ size remains unclear. In addition, females with larger eyespan, an indicator of size and fecundity, attracted more mating attempts from males, but this trait did not alter female acceptance. Genetic variation among males had a strong influence on male mating attempts and female acceptance, both via the traits we studied and other unmeasured attributes. These findings demonstrate the importance of assaying multiple traits in males and females, rather than focusing solely on prominent and exaggerated sexually dimorphic traits. The approach allows a more complete understanding of the complex mating decisions made by both males and females.     

Context‐dependent female preference for multiple ornaments in the bearded reedling

While it is well established that females prefer to mate with well‐ornamented males, the influence of perceptive and cognitive processes on the expression of female mate choice is still poorly known. It has been suggested that the female perception of a male's attractiveness is not absolute, but depends on the other males with which he is compared that have been previously encountered (comparative evaluation). We investigated whether mate preference in bearded reedlings (Panurus biarmicus) is dependent on or independent of social context in relation to two different traits: beard and tail lengths. Each female had a choice between two to three males with different modifications of beard and tail. For each female, three different experiments were conducted (one binary and two trinary tests). We found that when females are presented with options that vary antagonistically with respect to two ornaments (binary test), some individuals prefer one trait while others the other trait. This indicates that in our bearded reedlings population exists a mate preference polymorphisms. Moreover, we found that the presence of a third stimulus, irrespective of the initial preference, reduced the strength of the initial preference – what we can call a “preference dilution effect.” Our results suggest that the female's choice may be constrained by her cognitive abilities when she is simultaneously presented with several options varying for two uncorrelated traits.     

Spatiotemporal mating pattern variation in a wind‐pollinated Mediterranean shrub

Spatiotemporal variation in mating patterns is poorly known in wind‐pollinated plant species. Here, we analysed mating patterns of the wind‐pollinated dioecious shrub Pistacia lentiscus by genotyping 904 seeds from 30 mother plants with eight microsatellite markers in a high‐density population in two consecutive flowering seasons. We found significant differences in some mating system estimates between years, particularly in the levels of correlated paternity. Overall, within‐mothers correlated paternity was higher in 2007 than in 2006 (r_pWM = 0.085 and 0.030), which translated into an effective number of fathers (N_ep) of 11.8 and 33.6 respectively. Using a smoothing interpolation technique, we show that the effective pollen cloud was spatially structured in patches of high‐ and low‐genetic diversity, which do not remain constant from year to year. In 2006, the among‐mothers correlated paternity (r_pAM) showed no trend with distance, suggesting no restriction of pollen dispersal. However, in 2007, r_pAM was greater than zero at short distances, revealing the existence of small‐scale patterns of pollen dispersal. The fact that the studied seasons were climatically homogeneous during the flowering time suggested that the observed differences might be ascribed to between‐year phenological variation of individuals in the studied population or other (unknown) factors. Numerical simulations, based on the real data set, indicated that the clumping of males and decreasing plant density, which is related to different types of pollen limitation, greatly increase correlated mating in this wind‐pollinated species, which is of relevance under the frame of the continuous anthropogenic habitat disturbance suffered by Mediterranean ecosystems.