Biology subjects

Scaccabarozzi, D.

Publications and source records attributed to Scaccabarozzi, D..

4 recordsLinked to original sources

bioRxiv2025

Do sun orchids mimic buzz-pollinated plants? An experimental test of the adaptive significance of false anthers

O_LIMimicry implies that an organism gains fitness by resembling a model species, and one example is rewardless plants that attract pollinators by resembling co-flowering species that provide rewards. While trait matching between mimic and model has been characterised in many cases of putative floral mimicry, few have demonstrated that resemblance is adaptive and dependent on model presence. C_LIO_LISun orchids (Thelymitra) are believed to mimic flowers of buzz-pollinated rewarding plants by displaying false anthers. To test the adaptive value of the false anthers we examined whether fruit production of T. crinita and T. macrophylla was reduced when anthers were experimentally removed or obscured, and whether the reduction was stronger when putative model plants were abundant. We also assessed visual flower similarity of both orchids and their putative model plants according to bee colour perception and identified shared pollinators and whether their behaviour on T. crinita was similar to that on co-flowering rewarding plants. C_LIO_LIFruit production of both sun orchids was strongly reduced (60-71%) by removal or painting of false anthers but was not affected by the abundance of model plants. Sun orchid flowers closely matched flower colour of co-flowering pollen-rewarding species, and T. crinita shared pollinators with the rewarding species. Visiting bees attempted to buzz and manipulate the false anther, with a behaviour similar to that observed on model plants. C_LIO_LIThe experimental results demonstrate that the false anther is an important adaptation to pollination in sun orchids. Striking visual flower similarity and shared pollinators between orchids and models suggest that sun orchids are pollinated by bees that mistake orchids for buzz-pollinated rewarding plants. The adaptive value of the false anther did not depend on model plant abundance in the local population, indicating that the relevant spatial scale is larger, or that the effects of the model species are weak in comparison to effects of other rewarding species, i.e., that magnet effects of nectar-rewarding species are dominating. C_LIO_LIFalse anthers are widespread in the genus Thelymitra, and this "mimicry trait" seems to represent an evolutionary novelty that offers unique opportunities to explore adaptations to pollination in deceptive plants. C_LI

ecology↗

bioRxiv2025

Nuances of floral mimicry in Queen of Sheba orchids

O_LIBackground and Aims Floral deception can range from finely tuned mimicry of specific rewarding plants (Batesian mimicry) to a general resemblance of the rewarding community (generalised food deception). We focused on two species in the deceptive Thelymitra variegata complex (Queen of Sheba orchids) to examine whether pollination is consistent with generalised food deception or with specific mimicry of co-flowering buzz-pollinated tinsel lilies (Calectasia spp.). C_LIO_LIMethods We assessed i) overlap in flower colour and scent between orchids, tinsel lilies, and other flowers in the rewarding community, ii) pollinator sharing between orchids, tinsel lilies and other species, and ii) quantified orchid reproductive success in relation to abundance of tinsel lilies and other rewarding species. C_LIO_LIKey Results We found that T. speciosa matches flower colour and scent of its co-flowering tinsel lily, C. gracilis, while T. porphyrosticta partly overlaps with co-flowering C. demarzii in both traits. The orchids and tinsel lilies shared flower visitors, and the only visitor observed to transfer orchid pollen was Anthoglossa plumata bee (Colletidae) that displayed a behaviour associated with buzz pollination. This species was also observed to buzz-pollinate tinsel lilies. In T. speciosa, fruit production increased with abundance of both tinsel lilies and other rewarding species with similar flower colour, suggesting a combination of mimicry and magnet effects. However, relationships were driven by a single population. There was no association between rewarding community and reproductive success in T. porphyrosticta. C_LIO_LIConclusions The results are partly consistent with mimicry towards the co-flowering tinsel lily for both orchids. Specific mimicry is strongly supported by a close resemblance involving multiple floral traits, and by bee behaviour associated with the buzz-pollinated model. However, this contrasts with the lack of consistent effects of tinsel lily abundance on orchid reproductive success. The findings further suggest that shared floral scent may reinforce visual similarity and highlight that scent may be important in food mimicry systems. More generally, the T. variegata complex offers an interesting system for studying nuances between specific mimicry and generalised deception. C_LI

ecology↗

bioRxiv2022

Mimicking orchids lure bees from afar with exaggerated ultraviolet signals

O_LIFlowers have many sensory traits to appeal to pollinators, including ultraviolet (UV) absorbing markings, which are well known for attracting bees at close proximity (e.g. < 1 m). While striking UV signals have been thought to attract pollinators also at greater distances of meters, how the signals impact the plant pollination success over distance remains unknown. Here we report the case of the Australian orchid Diuris brumalis, a non-rewarding species, pollinated by bees via mimicry of rewarding pea plant Daviesia decurrens. When distant from the pea plant, Diuris brumalis was hypothesized to enhance pollinator attraction by exaggerately mimicking the floral ultraviolet (UV) reflecting patterns of its model. C_LIO_LIBy experimentally modulating floral UV reflectance with a UV screening solution, we quantified the orchid pollination success at variable distance from the model plants. C_LIO_LIWe demonstrate that the deceptive orchid Diuris brumalis attracts bee pollinators by emphasizing the visual stimuli, which mimic the floral UV signalling of the rewarding model D. decurrens. Moreover, the exaggerated UV reflectance of D. brumalis flowers impacted pollinators visitation at an optimal distance from D. decurrens, and the effect decreased when orchids were too close or too far away from the model. C_LIO_LIOur findings show that salient UV flower signalling plays a functional role in visual floral mimicry, likely exploiting perceptual gaps in bee neural coding, and mediates the plant pollination success at much greater spatial scales than previously expected. C_LI

ecology↗

bioRxiv2021

Trick or Treat? Pollinator attraction in Vanilla pompona (Orchidaceae)

Natural pollination of species belonging to the pantropical orchid genus Vanilla remains poorly understood. Based on sporadic records, euglossine bees have been observed visiting flowers of Neotropical Vanilla species. Our research aimed at better understanding the pollinator attraction mechanism of the Neotropical species Vanilla pompona, a crop wild relative with valuable traits for vanilla crop improvement programs. Using video footage, we identified floral visitors and examined their behavior. The flowers of V. pompona attracted Eulaema cingulata males, which distinctively displayed two behaviors: floral scent collection and nectar search; with the latter leading to pollen removal. Morphological measurements of floral and visitor traits showed that other Eulaema species may also act as potential pollinators. Additionally, we recorded natural fruit set in three populations and over a period of two years, tested for nectar presence and analyzed floral fragrances through gas chromatography - mass spectrometry. We observed a low natural fruit set (2.42%) and did not detect nectar. Twenty floral volatile compounds were identified, with the dominant compound trans-carvone oxide previously found to attract Eulaema cingulata males. We hypothesize a dual attraction of Eulaema cingulata males to V. pompona flowers, based on floral fragrance reward as the primary long-distance attraction, and food deception for successful pollen removal. Further research confirming this hypothesis is recommended to develop appropriate conservation policies for Vanilla crop wild relatives, which are the primary reserves of this crops genetic variation.

plant biology↗