Local plant density,pollination and trait–fitness relationships in a perennial herb

Both differences in local plant density and phenotypic traits may affect pollination and plant reproduction, but little is known about how density affects trait–fitness relationships via changes in pollinator activity. In this study we examined how plant density and traits interact to determine pollinator behaviour and female reproductive success in the self‐incompatible, perennial herb Phyteuma spicatum. Specifically, we hypothesised that limited pollination service in more isolated plants would lead to increased selection for traits that attract pollinators. We conducted pollinator observations and assessed trait–fitness relationships in a natural population, whose individuals were surrounded by a variable number of inflorescences. Both local plant density and plant phenotypic traits affected pollinator foraging behaviour. At low densities, pollinator visitation rates were low, but increased with increasing inflorescence size, while this relationship disappeared at high densities, where visitation rates were higher. Plant fitness, in terms of seed production per plant and per capsule, was related to both floral display size and flowering time. Seed production increased with increasing inflorescence size and was highest at peak flowering. However, trait–fitness relationships were not density‐dependent, and differences in seed production did not appear to be related to differences in pollination. The reasons for this remain unclear, and additional studies are needed to fully understand and explain the observed patterns.     

毛翠雀花花序内的性分配和繁殖成功

两性花植物花序内不同位置的性分配和繁殖成功一般存在差异,通常认为资源竞争、结构效应和交配环境是形成这种差异的主要原因。为了研究雄性和雌性繁殖资源在花序内不同位置间的最优分配问题,该文以青藏高原高寒草甸典型高山植物毛翠雀花为材料,通过比较花序内不同位置的花部特征和种子性状,对其花序内的性分配模式和雌性繁殖成功进行研究,并通过观察传粉者运动特点以及人工去花和补授花粉实验,探讨花序内资源竞争和交配环境对繁殖资源分配的影响。结果表明:(1)不同位置间的雄蕊数、雄蕊鲜重/雌蕊鲜重、花粉数及花粉胚珠比从花序基部到上部显著增加,而雌蕊鲜重和胚珠数逐渐减少,表现出上部花偏雄的性分配;上部花的结籽率显著低于基部花和中部花,不同位置间的发育种子数/果实和发育种子重/果实随着花位置的升高而显著降低,说明基部花具有更佳的雌性繁殖成效。(2)去花处理后,剩余果实的单个种子重/果实显著增加,但发育种子数/果实没有显著增加;而给上部花人工补授异花花粉后,位置间结籽率的差异消失,说明传粉限制而非资源竞争导致了花序内位置依赖的种子生产模式。(3)毛翠雀花雄性先熟的开花特征,以及传粉者苏氏熊蜂从花序基部到上部的定向访花行为,导致了花序内交配环境的变化。综上结果表明,毛翠雀花花序内的性分配和繁殖成功差异是对交配环境适应的结果,对其在高山环境中实现雌雄适合度最优化具有重要意义。     

Analysis of trait–performance–fitness relationships reveals pollinator-mediated selection on orchid pollination traits

Premise

The role of pollinators in evolutionary floral divergence has spurred substantial effort into measuring pollinator-mediated phenotypic selection and its variation in space and time. For such estimates, the fitness consequences of pollination processes must be separated from other factors affecting fitness.

Methods

We built a fitness function linking phenotypic traits of food-deceptive orchids to female reproductive success by including pollinator visitation and pollen deposition as intermediate performance components and used the fitness function to estimate the strength of pollinator-mediated selection through female reproductive success. We also quantified male performance as pollinarium removal and assessed similarity in trait effects on male and female performance.

Results

The proportion of plants visited at least once by an effective pollinator was moderate to high, ranging from 53.7% to 85.1%. Tall, many-flowered plants were often more likely to be visited and pollinated. Given effective pollination, pollen deposition onto stigmas tended to be more likely for taller plants. Pollen deposition further depended on traits affecting the physical fit of pollinators to flowers (flower size, spur length), though the exact relationships varied in time and space. Using the fitness function to assess pollinator-mediated selection through female reproductive success acting on multiple traits, we found that selection varied detectably among taxa after accounting for sampling uncertainty. Across taxa, selection on most traits was stronger on average and more variable when pollination was less reliable.

Conclusions

These results support pollination-related trait–performance–fitness relationships and thus pollinator-mediated selection on traits functionally involved in the pollination process.     

Allocation to reproduction following experimental defoliation in Platanthera bifolia (Orchidaceae)

The roles of herbivory and pollination success in plant reproduction have frequently been examined, but interactions between these two factors have gained much less attention. In three field experiments, we examined whether artificial defoliation affects allocation to attractiveness to pollinators, pollen production, female reproductive success and subsequent growth in Platanthera bifolia L. (Rich.). We also recorded the effects of inflorescence size on these variables. We studied the effects of defoliation on reproductive success of individual flowers in three sections of inflorescence. Defoliation and inflorescence size did not have any negative effects on the proportion of opened flowers, spur length, nectar production or the weight of pollinia. However, we found that hand-pollination increased relative seed production and defoliation decreased seed set in most cases. Interactions between hand-pollination and defoliation were non-significant indicating that defoliation did not affect female reproductive success indirectly via decreased pollinator attraction. Plants with a large inflorescence produced relatively more seeds than plants with a small inflorescence only after hand-pollination. The negative effect of defoliation on relative capsule production was most clearly seen in the upper sections of the inflorescence. In addition to within season effects of leaf removal, defoliated P. bifolia plants may also have decreased lifetime fitness as a result of lower seed set within a season and because of a lower number of reproductive events due to decreased plant size (leaf area) following defoliation. Our study thus shows that defoliation by herbivores may crucially affect reproductive success of P. bifolia.     

Pollen transfer efficiency and its effect on inflorescence size in deceptive pollination strategies

Pollination systems differ in pollen transfer efficiency, a variable that may influence the evolution of flower number. Here we apply a comparative approach to examine the link between pollen transfer efficiency and the evolution of inflorescence size in food and sexually deceptive orchids. We examined pollination performance in nine food‐deceptive, and eight sexually deceptive orchids by recording pollen removal and deposition in the field. We calculated correlations between reproductive success and flower number (as a proxy for resources allocated during reproductive process), and directional selection differentials were estimated on flower number for four species. Results indicate that sexually deceptive species experience decreased pollen loss compared to food‐deceptive species. Despite producing fewer flowers, sexually deceptive species attained levels of overall pollination success (through male and female function) similar to food‐deceptive species. Furthermore, a positive correlation between flower number and pollination success was observed in food‐deceptive species, but this correlation was not detected in sexually deceptive species. Directional selection differentials for flower number were significantly higher in food compared to sexually deceptive species. We suggest that pollination systems with more efficient pollen transfer and no correlation between pollination success and number of flowers produced, such as sexual deception, may allow the production of inflorescences with fewer flowers that permit the plant to allocate fewer resources to floral displays and, at the same time, limit transpiration. This strategy can be particularly important for ecological success in Mediterranean water‐deprived habitats, and might explain the high frequency of sexually deceptive species in these specialised ecosystems.     

Spatially inconsistent direct and indirect effects of herbivory on floral traits and pollination success in a tropical shrub

Investigations on plant–animal interactions have traditionally focused on single interactions at a time (e.g. herbivory, pollination), yet plant fitness is generally influenced in complex ways by several interactions operating concurrently, and very little is known on the degree of spatial consistency of the direct and indirect effects that link different interactions. This paper evaluates experimentally whether direct and indirect effects of herbivory on male and female flower size and pollination success of the monoecious tropical shrub Cnidoscolus aconitifolius (Euphorbiaceae) remain consistent at three distant regions in Yucatan (southeastern Mexico). Plants were subjected to different levels of leaf defoliation, and treatment effects on floral traits (corolla area, corolla tube length, pollen production), and male and female components of pollination success (percent pollen removal, number of pollen tubes) were subsequently measured to evaluate the indirect effect of herbivory on plant reproductive success via pollination. Defoliation had significant direct effects on floral traits, but its indirect effects differed between the male and female components of pollination success. Moreover, the relationships between defoliation, floral traits and male and female pollination success varied spatially (i.e. between regions), although they were frequently more spatially‐consistent for male success than for female success. Results from this study stress the importance of explicitly testing for spatial variation in direct and indirect effects arising from plant‐animal interactions.     

Influence of inflorescence size on sexual expression and female reproductive success in a monoecious species

Sex allocation theory forecasts that larger plant size may modify the balance in fitness gain in both genders, leading to uneven optimal male and female allocation. This reasoning can be applied to flowers and inflorescences, because the increase in flower or inflorescence size can differentially benefit different gender functions, and thus favour preferential allocation to specific floral structures. We investigated how inflorescence size influenced sexual expression and female reproductive success in the monoecious Tussilago farfara, by measuring patterns of biomass, and N and P allocation. Inflorescences of T.?farfara showed broad variation in sex expression and, according to expectations, allocation to different sexual structures showed an allometric pattern. Unexpectedly, two studied populations had a contrasting pattern of sex allocation with an increase in inflorescence size. In a shaded site, larger inflorescences were female-biased and had disproportionately more allocation to attraction structures; while in an open site, larger inflorescences were male-biased. Female reproductive success was higher in larger, showier inflorescences. Surprisingly, male flowers positively influenced female reproductive success. These allometric patterns were not easily interpretable as a result of pollen limitation when na?vely assuming an unequivocal relationship between structure and function for the inflorescence structures. In this and other Asteraceae, where inflorescences are the pollination unit, both male and female flowers can play a role in pollinator attraction.     

NATURAL SELECTION ON FLORAL TRAITS IN TWO SPECIES OF LOBELIA WITH DIFFERENT POLLINATORS

Using both multivariate and univariate regression techniques, I measured selection acting through female reproductive success in two hermaphroditic species with precise pollen placement but different pollinators: hummingbird-pollinated Lobelia cardinalis and bumblebee-pollinated L. siphilitica. Six traits were analyzed in two populations of L. cardinalis and one population of L. siphilitica: flower number, mean number of flowers open per day, inflorescence height, number of days in flower, median-flower date and nectar-stigma distance. In another study it was found that female reproductive success in one population of L. cardinalis was much less pollen limited than in the other two populations, and it was therefore expected that selection of female reproductive traits in this population would be weaker. In the univariate analyses correlations caused nearly all traits to have significant directional selection coefficients. However, in the multivariate analyses no traits in L. siphilitica experienced directional or quadratic selection. Selection acted differently in the two L. cardinalis populations. The less pollen-limited population experienced positive directional selection on flower number and median-flower date, while in the other L. cardinalis population there was positive directional selection on flower number and nectar-stigma distance and both positive directional and positive quadratic selection on height. The functional significance of floral traits in these two species and the probable effect of increased sample sizes are discussed.     

The independent and combined effects of floral traits distinguishing two pollination ecotypes of a moth‐pollinated orchid

Identifying traits and agents of selection involved in local adaptation is important for understanding population divergence. In southern Sweden, the moth‐pollinated orchid Platanthera bifolia occurs as a woodland and a grassland ecotype that differ in dominating pollinators. The woodland ecotype is taller (expected to influence pollinator attraction) and produces flowers with longer spurs (expected to influence efficiency of pollen transfer) compared to the grassland ecotype. We examined whether plant height and spur length affect pollination and reproductive success in a woodland population, and whether effects are non‐additive, as expected for traits influencing two multiplicative components of pollen transfer. We reduced plant height and spur length to match trait values observed in the grassland ecotype and determined the effects on pollen removal, pollen receipt, and fruit production. In addition, to examine the effects of naturally occurring variation, we quantified pollinator‐mediated selection through pollen removal and seed production in the same population. Reductions of plant height and spur length decreased pollen removal, number of flowers receiving pollen, mean pollen receipt per pollinated flower, and fruit production per plant, but no significant interaction effect was detected. The selection analysis demonstrated pollinator‐mediated selection for taller plants via female fitness. However, there was no current selection mediated by pollinators on spur length, and pollen removal was not related to plant height or spur length. The results show that, although both traits are important for pollination success and female fitness in the woodland habitat, only plant height was sufficiently variable in the study population for current pollinator‐mediated selection to be detected. More generally, the results illustrate how a combination of experimental approaches can be used to identify both traits and agents of selection.     

Flowering dynamics in Arum italicum (Araceae): relative role of inflorescence traits, flowering synchrony, and pollination context on fruit initiation

We studied the relative role of inflorescence traits, flowering synchrony, and pollination context for infructescence and fruit initiation in two Spanish populations of Arum italicum, a species in which inflorescences are the pollination unit. In this species, a specialized inflorescence organ, the appendix, is important for pollinator attraction. However, the short floral longevity and the production of mostly one inflorescence per plant make its pollination potentially dependent on strong flowering synchrony and on external factors not controlled by the plant (the pollination context). The flowering period in both sites lasted >3 mo. Day-to-day variation in simultaneous antheses was high, and 11-50% of antheses occurred on days during which no pollen donor was present. Inflorescence traits, flowering synchrony, and between-plant distance all influenced infructescence and fruit initiation, but their relative importance differed between sites. In one large population, infructescence initiation was positively related to inflorescence traits; in a smaller population infructescence initiation increased with the number of donor inflorescences. In both sites, percentage of fruits initiated per infructescence was dependent on a combination of inflorescence traits, flowering synchrony, and between-plant distance. Plants producing 2-4 inflorescences had higher probability of infructescence initiation and overlapped their antheses with more plants than single-inflorescence ones.     

Herbivores and plant defences affect selection on plant reproductive traits more strongly than pollinators

Pollinators and herbivores can both affect the evolutionary diversification of plant reproductive traits. However, plant defences frequently alter antagonistic and mutualistic interactions, and therefore, variation in plant defences may alter patterns of herbivore‐ and pollinator‐mediated selection on plant traits. We tested this hypothesis by conducting a common garden field experiment using 50 clonal genotypes of white clover (Trifolium repens) that varied in a Mendelian‐inherited chemical antiherbivore defence—the production of hydrogen cyanide (HCN). To evaluate whether plant defences alter herbivore‐ and/or pollinator‐mediated selection, we factorially crossed chemical defence (25 cyanogenic and 25 acyanogenic genotypes), herbivore damage (herbivore suppression) and pollination (hand pollination). We found that herbivores weakened selection for increased inflorescence production, suggesting that large displays are costly in the presence of herbivores. In addition, herbivores weakened selection on flower size but only among acyanogenic plants, suggesting that plant defences reduce the strength of herbivore‐mediated selection. Pollinators did not independently affect selection on any trait, although pollinators weakened selection for later flowering among cyanogenic plants. Overall, cyanogenic plant defences consistently increased the strength of positive directional selection on reproductive traits. Herbivores and pollinators both strengthened and weakened the strength of selection on reproductive traits, although herbivores imposed ~2.7× stronger selection than pollinators across all traits. Contrary to the view that pollinators are the most important agents of selection on reproductive traits, our data show that selection on reproductive traits is driven primarily by variation in herbivory and plant defences in this system.     

Effects of forest fragmentation on male and female reproductive success in<Emphasis Type="Italic"> Cestrum parqui</Emphasis> (Solanaceae)

In this paper we evaluate the effects of forest fragmentation on male (pollen removal, pollen load, and pollen tubes) and female reproductive success (fruit- and seed-set) of Cestrum parqui, a self-incompatible, pollination-specialist plant species. We also measure focal individual conspecific density to account for possible density-related effects that could influence the response variables. We calculate an index which incorporates male and female fitness and gives an integrated assessment of overall reproductive success. Forest fragmentation strongly affected the amount of pollen grains on stigmas and number of pollen tubes as well as seed-set, decreasing from continuous forest to small forest fragments, whereas focal individual conspecific density failed to explain any of the variability for the studied variables. Declines in overall reproductive success (i.e. male and female) in small forest fragments are ascribed to decreases in both the quality and quantity of pollination. Self-incompatibility coupled with a specialist pollination system may be particularly important traits determining the negative fragmentation effects observed in C. parqui. Logarithmic regression models described the behaviour of the variables along the fragmentation size gradient, allowing us to detect a threshold below which the effects of fragmentation begin to negatively affect reproductive success in C. parqui. Our results emphasize the importance of evaluating both components of the total plant fitness, as well as including simultaneously several aspects of pollination and reproduction processes when assessing the effects of forest fragmentation on plant reproductive success.     

Male-biased sex allocation in late-blooming flowers driven by resource limitation in the clonal perennial Aconitum kusnezoffii (Ranunculaceae)

Flowering phenology and clonal growth are known to affect resource and pollen availability, and therefore select for adaptive or constrained sex allocation strategies to some degree. However, the consequences of temporal sex allocation patterns for reproductive fitness across the flower, inflorescence, and genet levels have rarely been examined. Moreover, experimental tests of the underlying regulatory mechanisms are scarce. We examined the association of flowering phenology and inflorescence position with temporal sex allocation and reproductive success in the protandrous perennial clonal herb, Aconitum kusnezoffii, over four consecutive growing seasons by examining more than 39 000 flowers. We also conducted controlled experiments to test the effects of resource and pollen limitation on the female reproductive success of lateral inflorescences. We found that some male functions were positively correlated with flowering phenology, whereas female reproductive success was negatively correlated with flowering phenology and inflorescence position. Lateral inflorescences invested more in male function than terminal inflorescences and therefore yielded fewer and smaller seeds. Resource limitation may serve as the key mechanism underlying this differentiated pattern. Decreased female reproductive success was consistently observed at the flower and inflorescence levels as flowering occurred later in the growth season. Late-blooming lateral inflorescences specialized in the male function, and their female reproductive success was constrained by early-blooming terminal inflorescences. This might be the first attempt to systematically demonstrate sex allocation strategy differentiation in a protandrous plant species at the inflorescence level. In addition, our study provides empirical evidence of dichogamy selecting for specialized sex allocation strategies among inflorescences.     

Sexual selection in a hermaphroditic plant through female reproductive success

Sexual selection is well accepted as a mechanism of shaping traits in animals. However, whether and how floral traits are sexually selected in hermaphroditic plants remains less clear. Here, we use Passiflora incarnata to address how floral traits that affect pollination success are selected via female function. We manipulated the ecological context by limiting pollination and adding resources to expand the phenotypic distribution and alter the intensity of sexual selection. Total sexual selection favoured lower style deflexion because of its impact on pollen receipt and subsequent seed number. However, total selection on style deflexion was not significant, indicating additional selection on style deflexion through routes other than mating. Limited pollination and enhanced resources were expected to alter the distribution of pollen deposition and seed production and therefore intensify the Bateman gradient – the relationship between pollen receipt and seed production. Indeed, the Bateman gradient was strongest when pollination was limited, suggesting potential for sexual selection to influence floral trait evolution under these conditions. Overall, we found floral traits may be shaped by sexual selection through female reproductive success in this hermaphroditic plant. These results support manipulations to enhance the variance in mating as a mechanism to understand patterns of sexual selection.     

Enhanced reproductive success revealed key strategy for persistence of devastated populations in Himalayan food‐deceptive orchid,Dactylorhiza hatagirea

Anthropogenic disturbances adversely affect populations of rare and endemic plants, resulting in reduction of their population size and performance. Among different plant groups, deceptive terrestrial orchids are vulnerable and possess greater extinction risks because of rarity in occurrence. To understand the response of food‐deceptive terrestrial orchids to disturbances, we selected Dactylorhiza hatagirea as our representative species, which is endemic to Himalaya, and studied its natural populations. This species is rare for being habitat specific, pollination limited and threatened in its natural habitats. We tested the hypothesis that disturbances lead to reduction in population size and plant performance of food‐deceptive terrestrial orchids. For assessing the impact of disturbance, two contrasting groups, heavily devastated (HD) and lightly devastated (LD), were identified on the basis of frequency and intensity of disturbance (harvesting of plant for tubers) by interviewing local people, medicinal plant extractors and shepherds. HD sites, in comparison to LD sites, were found to have smaller population sizes, but showed an increase in plant growth traits (plant height, specific leaf area, leaf N and specific shoot length). Similarly, plants at HD sites were found to have invested less in inflorescence (inflorescence size, inflorescence length, inflorescence length fraction and flowers per length), but despite that showed higher reproductive success. This was a clear indication of enhanced performance of its populations driven by disturbances. Our findings suggested that food‐deceptive species in small populations tend to reduce the probability of population extinction and have the capability to recover rapidly if conserved in time.     

Evolution of the selfing syndrome: Anther orientation and herkogamy together determine reproductive assurance in a self‐compatible plant

Capacity for autonomous self‐fertilization provides reproductive assurance, has evolved repeatedly in the plant kingdom, and typically involves several changes in flower morphology and development (the selfing syndrome). Yet, the relative importance of different traits and trait combinations for efficient selfing and reproductive success in pollinator‐poor environments is poorly known. In a series of experiments, we tested the importance of anther–stigma distance and the less studied trait anther orientation for efficiency of selfing in the perennial herb Arabis alpina. Variation in flower morphology among eight self‐compatible European populations was correlated with efficiency of self‐pollination and with pollen limitation in a common‐garden experiment. To examine whether anther–stigma distance and anther orientation are subject to directional and/or correlational selection, and whether this is because these traits affect pollination success, we planted a segregating F2 population at two native field sites. Selection strongly favored a combination of introrse anthers and reduced anther–stigma distance at a site where pollinator activity was low, and supplemental hand‐pollination demonstrated that this was largely because of their effect on securing self‐pollination. The results suggest that concurrent shifts in more than one trait can be crucial for the evolution of efficient self‐pollination and reproductive assurance in pollinator‐poor habitats.     

Is the magnitude of pollen limitation in a plant community affected by pollinator visitation and plant species specialisation levels?

Pollen limitation on a plant community level has received little attention, although it might show which pollination-related traits may cause pollen limitation to vary among species. To address several central questions in plant reproductive biology, we investigated pollen limitation in 11 plant species, including visitation and specialisation levels of all species. The female reproductive success of most species within the studied plant community was not pollen limited, but a general tradeoff between seed production and seed weight occurred as a response to supplemental pollination. In contrast to general notion, we did not find that less visited species were most pollen limited. Instead, it appears that species with high visitation rates were most pollen limited. Our study provided conflicting evidence to whether specialisation levels may affect the degree of pollen limitation within the study community. We discuss these findings in the context of recent reviews on the occurrence, causes and consequences of pollen limitation in plants. In particular, we propose that, although pollen limitation is an important phenomenon, 1) the majority of species within a plant community may not experience pollen limitation at a given moment, 2) that common notions of which plant species should experience pollen limited reproductive success do not hold true in the studied plant community, and 3) that offspring quality is as likely affected by surplus pollen loads as is the number of offspring.     

菊科12种外来植物的有性繁殖特征和入侵风险研究

菊科植物具有极强的有性繁殖能力,对外来菊科观赏植物的引进存在极高的入侵风险。本研究以武汉常见的菊科12种外来观赏植物为对象,通过有性繁殖特征调查,研究植株的花部特征、花粉活力、传粉系统、种子产量,分析各物种有性繁殖能力的差异,评估其入侵能力。结果显示,多数物种可在隔绝传粉者情况下结实;访花昆虫类型多样,共观察到26种访花昆虫,其中膜翅目蜂类是主要的传粉者;结实情况具有一定差异。综合考虑花粉活力、传粉情况和结实情况,认为黑心金光菊(Rudbeckia hirta L.)、松果菊(Echinacea purpurea(L.)Moench)、大花金鸡菊(Coreopsis grandiflora Hogg.)、蛇目菊(Sanvitalia procumbens Lam.)的有性繁殖竞争力较高,对本地传粉环境可能有较大影响。本研究对近缘物种有性繁殖特征的综合分析结果可为评估外来物种的入侵风险提供一定的参考。     

Fruit production and floral traits: correlated evolution in <Emphasis Type="Italic">Govenia</Emphasis> (Orchidaceae)

The most common estimate of reproductive success in orchids is usually fruit set. Factors such as resource limitation and certain floral traits may influence reproductive success in animal-pollinated plants. Correlated evolution of reproductive success vs. seven floral traits (inflorescence length, flower number, flower distribution along inflorescence, dorsal sepal length, lateral sepal length, flower color, and column position) was studied in eight species of Govenia. Taxa represented three lineages in the genus. Independent contrasts were calculated on a phylogeny inferred from chloroplast (trnL-F IGS) DNA sequences, and a correlation test and multiple regression were then performed. Two data sets were evaluated, one including all eight species and another excluding G. utriculata, which is autogamous. The historical analyses showed that there is a correlation between reproductive success and dorsal sepal length, column position, and flower number, these correlations suggest that changes in these floral traits usually accompany evolutionary shifts in reproductive success. Multiple regression tests suggest that changes in reproductive success can be explained by shifts in flower number, inflorescence length, column position and by dorsal sepal length. When phylogeny is taken into account, our analyses showed that evolutionary shifts in these floral traits were correlated with changes in reproductive success. Evolutionary correlation between reproductive success and floral traits might be explained by the natural selection of certain floral phenotypes by pollinators.     

Reproductive success in fragmented habitats: do compatibility systems and pollination specialization matter?

Abstract. This paper explores whether plant breeding system and pollination specialization influence the reproductive response of plants to habitat fragmentation. It is meaningful for conservation to predict a plant species’ extinction risk. We found 25 studies in the literature assessing the effects of habitat fragmentation on either pollination or reproductive success of 46 plant species to answer the following questions: 1. Are pollination and reproductive success of self‐incompatible species more likely to decline with habitat fragmentation than the pollination and reproductive success of self‐compatible species? Although most of the species showed statistically significant negative effects, the pollination and reproduction of self‐incompatible species were as likely to decline with fragmentation as those of self‐compatible species. 2. Are pollination and reproductive success of specialist plants more affected than the pollination and reproduction of generalist plants? Comparisons of fragmentation‐related changes in pollination and reproductive success between specialists and generalists do not support the hypothesis that specialization in pollination increases the risk of plant extinction. 3. Can self‐incompatible species offset their expected higher vulnerability to fragmentation by being, on average, more pollination generalist than self‐compatible species? In a larger data set on 260 species, we did not find significant differences in either the mean number or frequency distribution of numbers of flower‐visiting species or orders between self‐compatible and self‐incompatible species. Our review suggests that no generalizations can be made on susceptibility to fragmentation based on compatibility system and pollination specialization.