(Cactaceae): Evidence for a Mixed Pollination Syndrome

Flora 205 (2010) 757–763

Contents lists available at ScienceDirect

Flora

journal homepage: www.elsevier.de/flora

Floral biology of Echinopsis chiloensis ssp. chiloensis (Cactaceae): Evidence for a mixed pollination syndrome

Helmut E. Walter

The EXSIS Project: Cactaceae Ex situ & In situ Conservation, Casilla 561, Rancagua, VI, Región, Chile article info abstract

Article history: In this study the flower biology of Echinopsis chiloensis ssp. chiloensis, a columnar cactus occurring in Received 17 September 2009 Central Chile, is investigated, in particular its pollination syndrome, its visitors, their frequencies and Accepted 4 December 2009 behaviors and their pollination efficiencies. As statements on floral anthesis of this species are contradictory, this study also intended to elucidate both its beginning and duration. A pollinator exclusion study Keywords: of a total of 162 flowers from 12 plants was conducted at one of the two study sites. Fruit and seed Chile production as well as seed viability were documented to evaluate pollinator efficiencies. Columnar cacti Anthesis proved to be nocturnal and diurnal, its duration and beginning was inversely proportional to Floral anthesis Hawkmoths maximum day temperatures. The experiment revealed that nocturnal and diurnal pollinator guilds both Pollination biology contributed to fruit set and that nocturnal pollination was more efficient. Yet, the efficiency of each of the Pollinator exclusion members of the three pollinator guilds was limited for different reasons such as scarcity, unpredictability or specific pollination behaviors. Although E. chiloensis has nocturnal flowers, various floral traits where found to differ from the classical hawkmoth pollination syndrome, suggesting a shift from the specialized nocturnal to a more open pollination syndrome, thus adding to fruit set when hawkmoths are locally or temporarily scarce. © 2010 Elsevier GmbH. All rights reserved.

Introduction Friedrich and G.D. Rowley ssp. pasacana (F.A.C. Weber ex Rüm- pler) G. Navarro (Badano and Schlumpberger, 2001; De Viana et The tall Chilean columnar Echinopsis chiloensis ssp. chiloensis al., 2001; Schlumpberger and Badano, 2005), Cereus peruvianus (L.) (Colla) H. Friedrich and G. D. Rowley (in the following abbreviated Miller (Silva and Sazima, 1995) and on the four Venezuelan species as E. chiloensis) occurs between the latitudes of 36◦ S and 30◦ S and Stenocereus griseus (Haworth) Buxbaum, P. moritzianus, Subpilo- is one of the most prominent plants in Central Chile. Its southerly cereus repandus (Linnaeus) Backeberg and Subpilocereus horrispinus habitats lie within the dry spiniferous matorrals and sclerophyl- (Backeberg) Backeberg (Nassar et al., 1997). Both specialized and lous woodlands characterized by a Mediterranean pluvio-seasonal mixed pollination syndromes have been described for columnar bioclimate with average annual precipitations between 250 and cacti in the Americas. Specializations for bat- (Nassar et al., 1997; 800 mm, while the northerly populations growing in the arid Valiente-Banuet et al., 1996), hummingbird- (Valiente-Banuet et desertic matorrals with a xeric-oceanic bioclimate receive average al., 1996), hawkmoth- (Fleming and Holland, 1998; Silva and rainfall between 70 and 200 mm (Luebert and Pliscoff, 2006). Sazima, 1995; Valiente-Banuet et al., 1996) or bee pollination The flowers of columnar cacti are mostly hermaphroditic (Valiente-Banuet et al., 2002) have been reported, but also mixed (Gibson and Nobel, 1986) and xenogamous, though a consider- pollination by bats, diurnal insects and hummingbirds (Sahley, able number of individuals from a population of Weberbauerocereus 1996; Valiente-Banuet et al., 2002), and by bats and hummingbirds weberbaueri (K. Schumann ex Vaupel) Backeberg was reported to be (Dar et al., 2006). Finally, evidence for a mixed pollination by hawk- autogamous (Sahley, 1996), and Nassar et al. (1997) reported par- moths, hummingbirds and diurnal insects has been documented for tial self-compatibility for Pilosocereus moritzianus (Otto ex Pfeiffer) E. atacamensis ssp. pasacana (Schlumpberger and Badano, 2005). Byles and G.D. Rowley. Flower morphology and the duration of floral anthesis in E. Only a few studies on the pollination biology of South Amer- atacamensis ssp. pasacana and E. chiloensis are similar, and Johow ican columnar cacti have been published so far: the studies on (1921) reported visits from the Giant Hummingbird (Patagona W. weberbaueri (Sahley, 1996), Echinopsis atacamensis (Philippi) H. gigas) to flowers of Cereus litoralis Johow (E. chiloensis ssp. litoralis (Johow) Lowry). And, as most columnar cacti in extratropical regions were assumed to have a mixed pollination syndrome (Nassar et al., 1997), a mixed pollination with different portions E-mail address: [email protected].

0367-2530/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.flora.2009.12.038 758 H.E. Walter / Flora 205 (2010) 757–763 from Sphingidae, hummingbirds and diurnal insects was hypothe- bag that was closed at the pericarpel with a wire before the begin- sized for E. chiloensis in the present study. To test this hypothesis, ning of anthesis. The bag was removed at 06:30 h in the morning a pollinator exclusion experiment was conducted at Site 1 of the to allow diurnal pollination. The other portion of flowers was left studied sites and diurnal and nocturnal visitors were recorded. uncovered from the beginning of anthesis at dusk, remaining acces- Published statements on the beginning and duration of the flo- sible to nocturnal pollinators, but the following morning at 06:30 h ral anthesis of E. chiloensis have been contradictory, incomplete they were covered with a bag as described above to avoid pollina- or vague in the past (Anderson, 2001; Eggli and Nyffeler, 2000; tion by diurnal pollinators. Care was taken that at any given period Hunt, 2006; Ritter, 1980). To settle the question, the beginning and 4–6 flowers from at least four individuals were left open synchron- duration of anthesis was documented for the flowers at Site 1. ically. In the middle of January 2009, all mature fruits in the three groups were counted separately to evaluate pollination efficiencies. Materials and methods Apart from the six tagged flowers that had been used for hand- cross-pollination, all flowers at Site 2 were left unmanipulated The species thus serving as an external control group. The plants were numbered and all the flowers appearing during the observation period E. chiloensis is a tall columnar cactus (3–6 m) mainly branch- were counted. After the observation period, the number of success- ing from near the base. It occurs between the latitudes of 30◦30 ful fruit initiations was counted to evaluate pollination efficiency S (Quebrada Choros) and 36◦ S (Maule Valley), mainly at inland under natural conditions. Successful fruit initiation was defined as ≥ habitats from 150 to 1200 m in the southerly and up to 1800 m maturing fruits 2.5 cm with remnants of the abscised perianth. in the northerly range of its distribution; its habitat preferences In mid January 2009, five mature fruits from five different plants are mainly dry north-facing hill sides with a low spiniferous vege- were collected to estimate seed production and compare it to the tation (typically Acacia caven, Puya coerulea or Colliguaja odorifera seed production of the different groups at Site 1. No fruit parasites and other low shrubs; Luebert and Pliscoff, 2006) but also dry river were observed at either site during the observation period. Fruit set valleys and alluvial deposits. among the nocturnal, diurnal, natural and control treatments was analyzed by one-way ANOVA.

Study sites and observation periods Hand cross-pollination at Site 2

For this study, two adjacent sites in different habitats were cho- Six flowers from different plants were tagged and cross- sen. Both are located in the Central Chilean Valley in the Region of pollinated by hand at three different times during the duration of Bernardo O’ Higgins, Prov. Cachapoal, 34◦ S. Rainfall occurs exclu- anthesis – shortly after anthesis at dusk, in the morning and shortly sively during autumn, winter and spring (April to November) and before the end of anthesis around midday – to be able to compare amounts to 450-500 mm per annum (Luebert and Pliscoff, 2006). their fruit production with the ones in the other groups. The flowers Absolute minimum temperatures may fall to −5 ◦C in the early were bagged during these intervals to exclude natural pollination. morning hours in June and July, while summers are long, hot and In mid-January 2009 the resulting fruits were counted. dry. Site 1 is located on the valley floor (18 individuals in an area of about 2000 m2, 520 m above sea level), Site 2 is located at a dis- Hand self-pollination at Site 1 tance of some 700 m north of Site 1, on the north-facing side of a hill (36 individuals in an area of about 3000 m2, 610 m above sea To test E. chiloensis ssp. chiloensis for xenogamy, six flowers from level). The pollinator exclusion study was performed at Site 1 only, different plants were tagged and hand self-pollinated at three dif- while all the flowers at Site 2 were left unmanipulated to study nat- ferent times of the day as described above. ural pollination efficiency and to serve as an external control group. The study period was from the beginning of the flowering period in Seed number and quality early November to peak flower production at the end of November 2008 at Site 1, and from mid November to early December at Site In mid January 2009, five mature fruits from each group at Site 2, respectively. Temperatures were measured during the complete 1 and the same number of mature fruits from non-manipulated observation period; minimum night temperatures varied from 9 ◦C flowers at Site 2 were harvested immediately after their equato- at the beginning to 15◦ C at the end of the study period, while day’s rial splitting to avoid losses caused by foraging ants. The pulp was maxima varied between 15 ◦C and 31 ◦C. A total of 168 flowers from removed, the seeds were cleaned and then weighed with a MIN- 12 plants at Site 1 and 147 flowers from 27 plants at Site 2 were QIAO electronic balance, Model FA21041N (d = 0.1 mg). Mean seed included in the study. masses among the diurnal, nocturnal, natural and control treatments were analyzed using t-test. Duration of floral anthesis To estimate the total seed number of the five fruits per group, a portion of 100 seeds randomly chosen from the total seed mass of The beginning and duration of anthesis was documented for the each group was then weighed separately and related to the total flowers from 12 plants during the complete study period at Site 1. seed mass of this group. To test the quality of the seeds in the four groups, 100 randomly chosen seeds per group were used for Pollination experiments a germination experiment under standardized conditions: a constant temperature of 23 ◦C and permanent artificial light during a Twelve of the 18 individuals at Site 1 flowered during the four period of 21 days; the seeds were sown on a sponge cloth kept weeks of observation. The plants were numbered and all flowers permanently wet in a flat porcelain bowl covered with glass. appearing during this period were tagged and divided into three groups for different treatments: the subapical flowers on the tall Floral visitors and pollinators to E. chiloensis ssp. chiloensis branches were not manipulated, remaining accessible to diurnal and nocturnal pollinators and served as a control group. One part Diurnal visitor counts were performed on three warm days dur- of the remaining flowers were exposed to diurnal pollination only: ing the observation period at Site 1 and on one warm day at Site to avoid nocturnal pollination the buds were covered with a gauze 2. Three to four flowers from five plants were observed around H.E. Walter / Flora 205 (2010) 757–763 759

Fig. 2. Duration of anthesis during a 48-h period on two different days. (A) On a hot day (25.11.2008). (B) On two consecutive cool, cloudy days (14–15.11.2008). Bold lines = duration of anthesis.

Beginning and duration of ﬂoral anthesis

During the whole observation period, the vast majority of the flowers of E. chiloensis began to open around dusk and all remained Fig. 1. A hawkmoth (Manduca sexta) was caught in this position inside a E. chiloensis fully open during the night. All flowers stayed open during the com- ssp. chiloensis flower. Scale bar = 10 mm. plete duration of anthesis: after having closed once, none of them re-opened again. The results of this study show that the begin- 08:00 h (the beginning of the diurnal visitors’ activity), around ning and duration of floral anthesis in E. chiloensis are inversely 10:30 h (their peak activity) and around 14:00 h (shortly before the proportional to day temperatures. On cool days with maximum ◦ end of floral anthesis). Four of the plants chosen grew in the core of temperatures ≤15 C the majority of the flowers opened around the population, while the fifth one grew farther away on the edge 19:00 h, while the majority opened around 21:00 h on hot days, ◦ of the population. Each count lasted for 5 min and included visits as when temperatures fell below 20 C(Fig. 2). Only 7 flowers from well as approaches. The total observation time at Site 1 was 225 min 5 plants were observed to open even later (between 22:00 h and ◦ and 75 min at Site 2. The average number of approaches and visits 23:00 h). On days with maximum midday temperatures <25 C, of the three 5-min-counts on three days (one day respectively) was anthesis lasted up to 42 h without interruption, on hot days with ◦ then converted into the average number of visits per hour for prac- maximum midday temperatures >26 C it lasted only up to 17 h tical reasons. When studying diurnal visitor behavior, two different (Figs. 2 and 3). On hot days, flowers closed around 14;00 h and on ways of touching the stigma were observed and therefore counted cooler days around 16:00 h (Fig. 2). separately: stigma contact may basically occur either when landing or when leaving the flower (or on both occasions). Diurnal inver- Pollinator exclusion study: fruit production tebrate visitors were determined by José Montalva, Universidad de Chile. The 29 flowers that were excluded from nocturnal pollination Nocturnal visits by Lepidoptera were expected for E. chiloensis. showed the lowest pollinator efficiency, yielding 5 mature fruits The population at Site 1 was therefore observed between 22:00 h (17%, Table 2). The 45 flowers in the diurnally excluded group and 01:00 h during three nights in the middle of the observation yielded 11 mature fruits (24%) and the 88 non-manipulated flow- ◦ period with night temperatures around 15 C. No artificial lights or ers produced 31 mature fruits (35%). In contrast to that, the 141 light traps were used in order not to attract visitors that would oth- unmanipulated flowers from 27 plants at Site 2 (Table 2) yielded erwise not approach columnar cactus flowers. Nocturnal visitors 82 fruits (58%). Differences in fruit set among the four treatments were determined by Ian Kitching, Natural History Museum, Lon- F3,299 = 10.79; p < 0.001. don, Jean Haxaire and Thierry Vaglia, both Insectarium Montreal Two of the six flowers chosen for the test for xenogamy initi- and Marcela Moré, University of Cordoba, Argentinia. ated a fruit that was aborted, however, after reaching a diameter of 1.5 cm. The other four flowers did not initiate a fruit (Table 2). The Results results of the test support the hypothesis that the breeding system of E. chiloensis ssp. chiloensis is xenogamic. Floral morphology and phenology All the six flowers reserved for hand cross-pollination yielded mature fruits (100%; Table 2). At the two study sites, E. chiloensis flowers from November to mid January, while the populations north of 32◦ S may flower up to Seed number, mass and quality six weeks earlier. The hermaphroditic flowers measure 14–16(–20) cm in length, The average seed mass (3.1446 g) and estimated seed number the hypanthium is elongated and narrow funnel-shaped (diameter (2560) per fruit were found to be highest in the group that was ca. 30 mm at the superior end). The long, slender style positioned exclusively nocturnally pollinated, while the lowest average seed in the centre of the wide open white corolla is surrounded by two mass (2.5553 g) and estimated seed number (2223) per fruit was series of numerous green stamens (Fig. 1). The style tends to incline observed in the exclusively diurnally pollinated group. The low sideward towards the hypanthium wall, thus leaving a wide open average seed mass (2.7485 g) and estimated seed number (2327) circular throat at the centre. The large, white stigma lobes some- in the non-manipulated group at Site 1 might be explained by the what exceeding the anthers, are clasped together at the beginning fact that not necessarily all of the flowers in the non-manipulated of anthesis, but begin to spread during the night. The distance from group had been pollinated diurnally and nocturnally. The average the stigma lobes to the floor of the large nectar chamber is approx- seed mass (2.7083 g) and the estimated seed number (2291) per imately 10 cm (Fig. 1). A faint, not unpleasant scent was noticed fruit in the naturally pollinated plants from Site 2 was only slightly especially during the night and the early morning hours (H. E. Wal- lower than the one at Site 1 (Table 3). Differences in mean seed ter, unpublished data). masses among the four groups t = 22.21; p < 0.1. 760 H.E. Walter / Flora 205 (2010) 757–763

Fig. 3. Duration of anthesis and maximum midday temperatures ( ) = duration of anthesis (h, left scale) ( ) = maximum midday temperatures (◦C, right scale).

Germination experiments reached the top of the perianth segments, where they rested for a while before flying away. Only 36% at Site 1 and 40% of the Germination rates of seeds derived from the diurnally, noctur- bees at Site 2 happened to crawl out on the side of the wall to nally and naturally pollinated groups at Site 1, as well as from the which the style had inclined and touched the stigma when leaving naturally pollinated group at Site 2, were all high (85–91%); the (Table 1). differences were not statistically significant (Table 3). The non-native honeybee Apis mellifera visited the flowers during 74% of all approaches at Site 2 (Table 1) and its stigma contact Observation of floral visitors to E. chiloensis rates when landing were high (70%). Many arriving honeybees at Site 2 were observed to carry non-conspecific pollen discernible by Various invertebrate visitors like undetermined hoverflies, bee- its golden yellow color (the pollen of E. chiloensis is whitish). This tles and ants were observed in or on the flowers, but were not non- flower constant behavior was also directly observed at Site counted, as they were not observed to be visiting flowers of differ- 1: the two honeybees recorded at that site flew from flowers of E. ent plants in a row. The most frequent diurnal invertebrate visitor chiloensis to flowers of a Yucca spec. (Agavaceae) growing nearby observed at both sites was a solitary, small (1.3–1.6 cm), grey bee and vice versa. The low number of its visits at Site 1 can be explained (Colletes spec.) that visited the flowers mainly to harvest pollen, but by the absence of apicultural activities near this site. was also found close to the nectar chamber (Fig. 1), from where it Neofidelia profuga, a large bee generally associated with cactus could possibly reach the nectar with its approximately 10 mm long flower visits, was only occasionally observed visiting flowers at Site −1 proboscis. The low percentage of visits compared to approaches 1 (60 approaches h ), but not at Site 2 (Table 1). Due to its size, it (20% at Site 1 and 21% at Site 2; Table 1) can be explained by the high is a dominant visitor when present, chasing away competitors and average approach frequency that resulted in a permanent queue- deterring them from visits while inside the flower. It was observed ing for access to the flowers (Table 1). Approach frequencies varied visiting the flowers during 70% of the approaches, touching the considerably during the day (Fig. 4): during the peak activity, up to stigma in nearly 90% of its visits (52% when landing) and flying 28 approaches per minute to a flower of a plant from the core of the from plant to plant. population were counted, while a plant from the edge of the pop- In neither of the three 3-h observation periods were nocturnal ulation was approached significantly less (Fig. 4). One single visit visitors observed, which indicates a low visitation frequency. Yet lasted 1–2 min, but up to six individuals of Colletes had been found on one occasion, a live hawkmoth (Manduca sexta) was detected by visiting one and the same flower simultaneously. chance inside one of the open flowers reserved for natural pollina- A specific landing technique was observed in the majority of tion in the early morning. The hawkmoth was found in a downright Colletes visits: the bees only rarely used the stigma as a landing position halfway down the hypanthium (Fig. 1), obviously to get platform (15% at Site 1 and 13% at Site 2; Table 1), but rather nearer to the nectary, as the average distance between the stigma dived directly into the flower’s wide open throat, as the floral style is usually inclined towards the side. When leaving the flower, the majority crawled up the inner hypanthium wall until they

Table 1 Pollination frequency and counts of stigma contacts of the three invertebrate diurnal pollinators at Site 1 and Site 2 (all plants from core of population).

Approaches Visits Stigma contact Stigma landing contact exit

Site 1 Colletes spec. 1020 204 31 73 Neoﬁdelia profuga 60 42 22 14 Apis mellifera 2221

Site 2 Colletes spec. 652 136 18 55 Neoﬁdelia profuga 0000 Apis mellifera 163 120 84 48

Number of approaches, visits and stigma contacts are averages of all counts h−1. Fig. 4. Average number of approaches per hour by Colletes spec. ( ) = plant from Total observation time at Site 1 = 225 min and at Site 2 = 75 min. core of population ( ) = plant from the edge of population. H.E. Walter / Flora 205 (2010) 757–763 761 and the nectar chamber in E. chiloensis flowers at Site 1 was mea- population size of the former site in combination with the reduced sured to be 10 cm (Fig. 1). number of synchronically open flowers caused by the exclusion experiment. The very low fruit production rates in both excluded groups at Site 1 (17% in the nocturnally excluded and 24% in the Discussion diurnally excluded group) might on the one hand be explained by the even lower number of synchronically open flowers. On the other Floral anthesis hand, Dar et al. (2006) reported even lower fruit set percentages both in nocturnal (8.33%) and diurnal (2.8%) pollination treatments The majority of the studies on the floral biology of columnar that were obviously not caused by a low number of synchronically cacti mentioned the beginning and duration of floral anthesis, but open flowers, as the number of plants at their study site was much only a few hinted at variations in its duration (Johow, 1921; Sahley, higher. Thus the very low fruit set in the nocturnal and diurnal pol- 1996). The present study documents considerable variation in the lination treatments at Site1 appears mainly as a result of pollen duration of anthesis in E. chiloensis (17–42 h, Figs. 2 and 3), and limitation caused by the exclusion of one (respectively two) of the shows it to be correlated to day temperatures. Invertebrate polli- pollinator guilds. nator activities may be affected by low temperatures (e. g., Abrol, Compared to the six hand cross-pollinated flowers’ fruit produc- 1993; Schlumpberger and Badano, 2005), but in E. chiloensis this is tion (100%), natural fruit production in the external control group balanced by the extra anthesis time of up to 22 h the following day. at Site 2 was low (58%), but higher than the one reported by Dar et Johow (1921) reports duration of anthesis of four to five days for E. al. (2006) for their naturally pollinated control group (45.4%) and chiloensis ssp. litoralis. I have not been able to corroborate this up to Badano and Schlumpberger (2001) at their Site 1 (50%). now but, as the duration of anthesis was shown to be a function of temperature in the present study, it seems possible that the lower Pollination efficiency temperatures at this subspecies’ coastal habitats and the generally lower temperatures during its earlier flowering period (August to Lee (1984), Winsor et al. (1987) and Parker (1997), all cited November) might cause a longer duration of anthesis. in Badano and Schlumpberger, 2001) showed that an increase in The point of time at which flowers open, defines the type of the number of [conspecific] pollen grains deposited on the stigma anthesis: flowers opening in the morning are generally called diur- results in an increased number of seeds in many-seeded fruits. nal and those opening at dusk nocturnal. Yet, many columnar cacti With xenogamic plants like E. chiloensis, this means, of course, that with nocturnal flowers extend their anthesis into the following only an increase in the number of exogamous conspecific pollen morning or even afternoon, and Polaskia chichipe has been reported results in a higher number of seeds and/or fruits. As stigmata may to extend its diurnal flowers being open into the night (Otero- hold an only limited number of pollen grains, it is important for Arnaiz et al., 2003, cited in Dar et al., 2006). Extending floral anthesis the plant’s reproductive success that the limited stigma surface to the following day or night adds the possibility of visits by new becomes charged with as many exogamous conspecific pollen as guilds of pollinators at little extra cost to the plant, thus adding to possible. seed production at times when the original pollinators are scarce and/or unpredictable (Dar et al., 2006; Sahley, 1996). Such mixed Diurnal pollinators pollination syndromes are considered to be a common reproductive strategy in extratropical columnar cacti with diurnal and nocturnal With respect to day-time pollination, the generalist A. mellifera flowers (Nassar et al., 1997). might be considered a poor pollinator of E. chiloensis flowers despite The classical floral syndrome for hawkmoth pollination is char- its high rate of stigma contacts when landing. Its missing flower acterized by nocturnal flowers with an anthesis beginning around constancy might favor non-conspecific pollen transfer provoking a dusk, highly reflective (white or pale pink) flowers with a long and competition for the stigmatic surface (Badano and Schlumpberger, narrow hypanthium, strong and sweet nocturnal scent and a usu- 2001). This is supported by the fact that natural fruit production ally low number of short stamina (Fenster et al., 2004; Gibson, 2001; at Site 2 was low (58%) compared to the fruit production of man- Riffell et al., 2008). Although E. chiloensis is visited by hawkmoths, ually hand-crossed flowers (100%). Site 2 is located in the close not all of its floral traits match the standard hawkmoth pollination vicinity of beekeeping activities and a comparably high number syndrome: their scent is much weaker, their hypanthia are longer of visits of A. mellifera were counted at this site (120 visits h−1). than the hawkmoths’ proboscises and are more funnel-form and An even lower fruit production rate (50%) was reported by Badano the number of stamens is by far higher. Mainly pollen harvesting and Schlumpberger (2001) for the naturally pollinated flowers of E. bees profit from the high total number of stamens, and humming- atacamensis ssp. pasacana at one of their sites that was also located birds select for wider corolla tubes, which allow them to enter in the vicinity of areas with apicultural activities, while the natu- the flowers more effectively (Campbell, 1996). On the other hand, rally pollinated flowers at their other site yielded 100% of fruits in hawkmoths are flexible enough to cope with these floral modifi- the absence of apicultural activities. Together with the results of cations, as they are known to explore and learn to utilize novel the present study, this supports the assumption that the efficient resources despite innate odour preferences (Riffell et al., 2008)or pollen harvesting behavior of the introduced honey-bee A. mellifera pollination behavior. might result in a lower fruit production of the cactus in populations at sites with a high Apis abundance. Pollinator exclusion study N. profuga’s stigma contacts when landing and its flower constancy were found to be high, but the low number of visits to flowers Although the pollinator exclusion study had been conducted at of E. chiloensis makes it less likely to be an efficient pollinator. only one site, it provides good evidence that E. chiloensis has a mixed The type of the stigma contact during visits of invertebrate pol- pollination, as initially hypothesized. Diurnal pollination produced linators to flowers of E. chiloensis was found to vary (Table 1) and 40% less fruit set than nocturnal, although the invertebrate diur- might be directly related to the visitor’s efficiency in plants with nal visitors had been permanently present during the observation xenogamic flowers: when landing on the stigma before harvest- period. Fruit production in the naturally pollinated group at Site 1 ing, the probability of discharging exogamous pollen previously was lower (35%) than the one in the naturally pollinated control collected from a flower of a different conspecific individual is group at Site 2 (58%). This may partly be explained by the smaller high. When, however, the pollinator touches the stigma only 762 H.E. Walter / Flora 205 (2010) 757–763

Table 2 2005). Johow (1921) even considered P. gigas the main pollinator Pollinator exclusion experiment: fruit production for six different pollination treat- of the ﬂowers of E. chiloensis ssp. litoralis. ments of 315 ﬂowers from 39 plants.

Pollination treatment No. of plants No. of No. of Fruit Nocturnal pollinators flowers fruits set (%) Diurnal 7 29 5 17.2 Schumann (1899, cited in Johow, 1921) supposed that Lepi- Nocturnal 8 45 11 24.4 doptera might play a role in the pollination of cacti [sic!], but Johow Control 12 88 31 35.2 (op. cit.) was unable to corroborate either diurnal or nocturnal Lepi- Control external 27 141 82 58.2 Hand-self 6 6 0 0 dopteran visits to the flowers of E. chiloensis ssp. litoralis. This study, Hand-cross 6 6 6 100 however, documented a visit of a member of the Sphingidae to a Chilean columnar cactus for the first time. Five species of sph- Diurnal, nocturnal, natural and control treatments: F3,299 = 10,79; p < 0.001. ingids are reported to be common, but not abundant in Chile (Ureta and Donoso, 1956) and might be considered potential pollinators Table 3 of E. chiloensis flowers, as their geographic occurrence coincides Pollinator exclusion experiment: seeds produced by four different pollination treatments (5 fruits per group) and germination rates. with its distribution and they are locally and temporarily resident at its habitats during its flowering period: Agrius cingulatus, Hyles Pollination treatment Seed mass (g) No. of Germination (%; 100 annei, Hyles lineata, M. sexta and Hyles euphorbiana (Angulo and (d = 0.1 mg) seeds seeds per group) Antezana, 2001; Perez, 2005; Ureta and Donoso, 1956). Despite of Diurnal 2.5553 2223 91 their scarcity, Sphingidae were considered to be highly efficient Nocturnal 3.1446 2560 85 nocturnal pollinators of columnar cacti for their size and pollination Control 2.7485 2327 88 Control external 2.7083 2291 87 behavior (Raguso et al., 2003; Schlumpberger and Badano, 2005), favoring stigma contacts when landing. They have to crawl into the Seed numbers and seed masses stated are averages per fruit; seed masses among the four groups: t = 22.21; p < 0.1. long flowers of E. chiloensis in search of nectar reward, as their proboscis is not long enough (the proboscis of the collected Manduca measured approx. 6 cm) to reach all the way down to the nectary while leaving the flower it had just been harvesting, the proba- when hovering in front of the flower or perching on the perianth bility of discharging exogamous pollen on the stigma is far lower, segments or the style. Gibson (2001) also mentioned that foraging as the insect’s legs and abdomen are thickly covered with a hawkmoths do not always hover in front of flowers without landing layer of endogamous pollen that (supposedly) overlies the exog- on the stigma, but enter certain types of flowers (like the broadly amous pollen previously harvested from a flower of a different open trumpet-shaped Echinopsis flowers), and are then thickly cov- individual. ered with pollen. A further observation supports the assumption of The low fruit production rate in the exclusively diurnally pol- their high pollination efficiency: as the beginning of anthesis occurs linated group at Site 1 (Table 2) can thus be partly explained by at dusk, hawkmoths enjoy the ius primae noctis, enabling them to the finding that the most frequent diurnal visitor Colletes spec. had load their head, breast and abdomen with large amounts of pollen by far the lowest stigma contacts when landing—caused by its pre- from still untouched anthers and deposit them on a virgin stigma. ferred landing technique described above. This pollination behavior No visits from nocturnal insect families other than Sphingidae could leads to smaller amounts of exogamous pollen discharged on the be observed in the present study, and Gibson (2001) stated that stigma and is only partly compensated by the insect’s high visita- other moth families, such as Noctuidae and Geometridae utilize tion frequency and flower constancy. different groups of flowers, making it probable that hawkmoths Colletes spec. may be considered to be a possibly opportunis- are the main nocturnal pollinators of E. chiloensis. tic pollen thief specialized in E. chiloensis flowers for the following Hawkmoths are highly migratory in search of food and during reasons: (i) it was observed to be highly flower constant, visiting their pre-reproductive phases (Gibson, 2001; Southwood, 1962), exclusively the flowers of E. chiloensis, flying from plant to plant in generally considered to be locally and temporally scarce (Dar et a trap-line pattern. After the end of its anthesis in the afternoon, al., 2006; Raguso et al., 2003; Schlumpberger and Badano, 2005; Colletes bees have not been observed to visit flowers of plants from Ureta and Donoso, 1956), and, together with low flower numbers other families. (ii) Its residence at both sites coincided with the [in small populations] this might lead to low pollination effi- flowering period of E. chiloensis from November to mid January. It ciency rates (Raguso et al., 2003). The presence and abundance had not been observed visiting other flowers before or after that of hawkmoths in a certain area may be influenced by between- period. (iii) At both sites all the nests of Colletes were found in close year variations in temperatures and precipitation (Sahley, 1996; proximity to E. chiloensis. A specialization of Colletes spec. on this Schlumpberger and Badano, 2005). Although the between-year cactus, however, can only be proven with certainty after analyses variation of precipitation in the study areas (200–550 mm) is lower of pollen load or pollen stored in the nests cells. than at the northerly more arid habitats of E. chiloensis (10–120 mm, Although it is resident but not abundant in Central Chile dur- Luebert and Pliscoff, 2006), it may influence nocturnal pollinator ing the flowering period of E. chiloensis (Jaramillo et al., 2003), we presence and abundance. Temperatures at the study areas usually were unable to observe the shy Giant Hummingbird (P. gigas) vis- do not much vary from year to year (Luebert and Pliscoff, 2006), iting the flowers of E. chiloensis at the two study sites during the but the exceptionally cold and long winter of 2007 might have had observation period. But it happened to observe one individual vis- a detrimental effect, at least on the larvae of hawkmoths. iting flowers of E. chiloensis at Site 1 after the observation period, Although the pollination efficiency of each of the members near the end of the flowering period mid January 2009 and also in from the different guilds was shown to be limited for different the past such visits were observed on various occasions at Site 1. reasons such as temporal and spatial scarcity, unpredictability The low fruit production rate (Table 2) and seed mass in the exclu- or pollination behavior, E. chiloensis is a widespread, abundant sively diurnally pollinated group (Table 3) may be partly explained plant whose conservation status was categorized as “least con- by this year’s scarcity of P. gigas at both study sites. When present, cern” (IUCN Red List Categories: Version 3.1, 2001) by Hoffmann however, it is reported to be an efficient pollinator, being highly and Walter (2004) and Hunt (2006). Yet, when one of the guilds flower constant, touching the stigma [when landing] at every visit was excluded experimentally, this led to a drastic decrease in fruit and carrying vast amounts of pollen (Schlumpberger and Badano, set indicating that only the contribution of both the nocturnal and H.E. Walter / Flora 205 (2010) 757–763 763 diurnal guilds guarantees the overall reproductive success of E. Hunt, D. (assisted by Taylor, N., Charles, G.), 2006. The New Cactus Lexicon. dh books, chiloensis. Unfortunately enough, this also means that the repro- Milborne Port, UK. Jaramillo, A., Burke, P., Beadle, D., 2003. Birds of Chile. Christopher Helm, London. ductive success of this still abundant plant will be severely affected Johow, F., 1921. Las Cactáceas de los alrededores de Zapallar. Rev. Chil. Hist. Nat. 15, if the fragile pollination balance is disturbed by ever increasing 152–166. human encroachments. Lee, T.D., 1984. Patterns of fruit maturation: a gametophyte competition hypothesis. Am. Nat. 123, 427–432. Luebert, F., Pliscoff, P., 2006. Sinopsis Bioclimática y Vegetacional de Chile. Editorial Acknowledgement Universitaria, Santiago de Chile. Nassar, J.M., Ramirez, N., Linares, O., 1997. Comparative pollination biology of Venezuelan columnar cacti and the role of nectar-feeding bats in their sexual I am grateful to Dr. Urs Eggli, Städtische Sukkulentensammlung reproduction. Am. J. Bot. 84, 918–927. Zürich, for his valuable comments and the revision of an earlier Otero-Arnaiz, A., Casas, A., Bartolo, C., Perez-Negrón, E., Valiente Banuet, A., 2003. version of the manuscript. Evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacan Valley, Central Mexico: reproductive biology. Am. J. Bot. 90, 593–602. Parker, I.M., 1997. Pollinator limitation of Cytisus scoparius (scoth broom), an inva- References sive exotic shrub. Ecology 78, 1457–1470. Perez, V., 2005. Agrius cingolatus (Hübner, 1839) e Hyles lineata (Fabrizius, 1775) Abrol, D.P., 1993. Insect pollination and crop production in Jammu and Kashmir. (Lepidoptera: Sphingdae), Primeros registros de esphingidos para la Region de Curr. Sci. 65, 265–269. Magallanes. An. Inst. Patag. (Chile) 33, 59–61. Anderson, E.F., 2001. The Cactus Family. Timber Press, Portland, Oregon. Raguso, R.A., Henzel, C., Buchmann, S.L., Nabhan, G.P., 2003. Trumpet flowers of the Angulo, A., Antezana, T., 2001. Vuelo de mariposas nocturnas frente a la costa de Sonoran Desert: floral biology of Peniocereus cacti and sacred Datura. Int. J. Plant Chile. Rev. Biol. Trop. 49, 1265–1266. Sci. 164, 877–892. Badano, E.I., Schlumpberger, B.O., 2001. Sistema de cruzamiento y estimaciones Riffell, J.A., Ruben, A., Abrell, L., 2008. Floral trait associations in hawkmoth- en la eficiencia de polinización sobre Trichocereus pasacana (Cactaceae) en dos specialized and mixed pollination systems. Datura wrightii and Agave spp. in poblaciónes del noroeste Argentino. Gayana Bot. 58, 115–122. the Sonoran Desert. Comm. Integr. Biol. 1, 6–8. Campbell, D.R., 1996. Mechanisms of hummingbird-mediated selection for flower Ritter, F., 1980. Kakteen in Südamerika, vol. 3, Selbstverlag, Spangenberg, Germany. width in Ipomopsis aggregata. Ecology 77, 1462–1472. Sahley, C.T., 1996. Bat and hummingbird pollination of an autotetraploid columnar Dar, S., Del Coro Arizmendi, M., Valiente-Banuet, A., 2006. Diurnal and nocturnal cactus. Weberbauerocereus weberbaueri (Cactaceae). Am. J. Bot. 83, 1329–1336. pollination of Marginatocereus marginatus (Pachycereeae: Cactaceae) in Central Schlumpberger, B.O., Badano, E.I., 2005. Diversity of floral visitors to Echinopsis ata- Mexico. Ann. Bot. 97, 423–427. camensis subsp. pasacana (Cactaceae). Haseltonia 11, 18–26. De Viana, M.I., Ortega Baes, T., Saravia, M., Badano, E.I., Schlumpberger, B.O., 2001. Schumann, K., 1897–1899. Gesamtbeschreibung der Kakteen. J. Neumann, Neu- Floral biology and pollination of Trichocereus pasacana (Cactaceae) in the Los damm, Germany. Cardones National Park. Rev. Biol. Trop. 49, 279–285. Silva, W.R., Sazima, M., 1995. Hawkmoth pollination in Cereus peruvianus, a columnar Eggli, U., Nyffeler, R., 2000. Similarity is only skin-deep: the use of comparative plant cactus from southeastern Brazil. Flora 190, 339–343. anatomy as illustrated by a study of columnar cacti from Chile (Eulychnia and Southwood, T.R.E., 1962. Migration of terrestrial arthropods in relation to habitat. Echinopsis, Cactaceae). Bot. Helv. 110, 1–10. Biol. Rev. Camb. Phil. Soc. 37, 171–214. Fenster, C.B., Armbruster, W.S., Wilson, P., Dudash, M.R., Thomson, J.D., 2004. Ureta, E., Donoso, R., 1956. Revisión de la familia Sphingidae (Lep. Het.) en Chile. Bol. Pollination syndromes and floral speciation. Annu. Rev. Ecol. Evol. Syst. 35, Mus. Nac. Hist. Nat., Chile 26, 237–256. 375–403. Valiente-Banuet, A., Arizmendi, M.C., Rojas, A., Dominguez, L., 1996. Ecological rela- Fleming, T.H., Holland, J.N., 1998. The evolution of obligate mutualisms: the senita tionships between columnar cacti and nectar-feeding bats in Mexico. J. Trop. cactus and senita moth. Oecologia 114, 368–375. Ecol. 11, 1–17. Gibson, A.C., 2001. The plants that love hawkmoths. Newsletters of the Valiente-Banuet, A., Rojas-Martínez, A., Casas, A., Silva, C., Dávila-Aranda, P., 2002. Mildred E. Mathias Botanical Garden 4. http://www.botgard.ucla.edu/ Biotic interactions and population dynamics of columnar cacti. In: Fleming, T.H., Theplantsthatlovehawkmoths. Valiente-Banuet, A. (Eds.), Columnar Cacti and their Mutualists: Evolution, Ecol- Gibson, A.C., Nobel, P.S., 1986. The Cactus Primer. Harvard University Press, Cam- ogy and Conservation. The University of Arizona Press, Tucson, pp. 225–240. bridge, MA, USA. Winsor, J.A., Davis, L.E., Stephenson, A.G., 1987. The relationships between pollen Hoffmann, A.E., Walter, H.E., 2004. Cactáceas en la flora silvestre de Chile, 2nd ed. load and fruit maturation and the effect of pollen load on offspring vigour in Ediciónes Fundación Claudio Gay, Santiago de Chile. Cucurbita pepo. Am. Nat. 129, 643–656.