Short flowers for long tongues: Functional specialization in a nocturnal pollination network of an asclepiad in long‐tongued hawkmoths

Abstract

Since Darwin, very long and narrow floral tubes have been known to represent the main floral morphological feature for specialized long‐tongued hawkmoth pollination. However, specialization may be driven by other contrivances instead of floral tube morphology. Asclepiads are plants with a complex floral morphology where primary hawkmoth pollination had never been described. We detailed here the intricate pollination mechanism of the South American asclepiad Schubertia grandiflora, where functional specialization on long‐tongued hawkmoth pollinators occurs despite the short floral tube of this species. We studied two plant populations in the Brazilian Cerrado and recorded floral visitors using different approaches, such as light‐trapped hawkmoths for pollen analysis, direct field observations, and IR motion‐activated cameras. Finally, using a community‐level approach we applied an ecological network analysis to identify the realized pollinator niche of S. grandiflora among the available niches in the pollinator community. Throughout a period of 17 years, long‐tongued hawkmoths were consistently recorded as the main floral visitors and the only effective pollinators of S. grandiflora. Flowers rely on highly modified corona and gynostegium, and enlarged nectar chambers, to drive visitors and pollination mechanism. Despite its relative short‐tube, network analysis placed S. grandiflora in the module including exclusively long‐tongued hawkmoth pollinators and the most phenotypically specialized sphingophilous plants in the community. These results represent the first example of functional specialization in long‐tongued hawkmoths in an asclepiad species. However, this specialization is uncoupled from the long floral tubes historically associated with the sphingophily syndrome. Abstract in Portuguese is available with online material.

Pollination of Chamaepentas nobilis (Rubiaceae) by long‐proboscid hawkmoths in south‐central Africa: Trait mismatching and floral scent chemistry

“…The floral mechanism thus explains the unusual mismatch in traits, with the corolla tube being shorter than the proboscis of the pollinators. Similar mismatches where the tube is shorter than the hawkmoth pollinator proboscis have been recorded in other plants with proboscis placement of pollen such as Erica cylindrica (Ericaeae) (Van der Niet & Cozien, 2022) and Harveya speciosa (Orobanchaceae) (Johnson & Raguso, 2016), Mandevilla laxa (Apocynaceae) (Moré et al., 2007) and Schubertia grandiflora (Apocynaceae) (Amorim et al., 2022). Some authors have attributed flower depth‐pollinator proboscis trait mismatches to degree of specialization or ecological dependency of interactions (Anderson, Terblanche, et al., 2010), but a much simpler explanation is that flowers with proboscis placement of pollen are not functionally required to precisely match or exceed the length of the proboscis of their pollinators.…”

“…Mandevilla laxa (Apocynaceae) (Moré et al, 2007) and Schubertia grandiflora (Apocynaceae) (Amorim et al, 2022). Some authors have attributed flower depth-pollinator proboscis trait mismatches to degree of specialization or ecological dependency of interactions (Anderson, Terblanche, et al, 2010), but a much simpler explanation is that flowers with proboscis placement of pollen are not functionally required to precisely match or exceed the length of the proboscis of their pollinators.…”

“…Plants with flowers that place pollen on the head of hawkmoths have been shown to undergo strong selection for floral tubes that exceed the length of the proboscis of visiting hawkmoths as this results in effective pollen transfer (Alexandersson & Johnson, 2002; Nilsson, 1988). However, evolutionary adjustment of floral tube length appears to be different for plants with flowers that place pollen on the proboscis of their pollinators (Amorim et al., 2022; Moré et al., 2007). Although such plants may benefit from having tubes that are nearly as long as the pollinator proboscis, as the basal part of the proboscis is broader with greater pollen carrying capacity, they do not usually gain any advantage from exceeding the proboscis length of their pollinators.…”

Opossums and birds facilitate the unexpected bat visitation to the ground‐flowering Scybaliumfungiforme

“…During the flowering seasons of S. fungiforme (from May to August) in 2020 and 2021, we used four IR motion‐activated cameras (as in Amorim, Marino, et al, 2022) to record the floral visitors of S. fungiforme . We focused on three remnants of the Seasonal Atlantic Forest in the state of São Paulo, Brazil (Appendix S1: Figure S1).…”

Shooting area of infrared camera traps affects recorded taxonomic richness and abundance of ground‐dwelling invertebrates

“…Therefore, employing ICTs with a time‐lapse trigger is an effective and practical approach toward monitoring ground‐dwelling invertebrates in fields with a precise temporal ecological niche across diverse monitoring durations (Burks et al., 2022 ; Johnson et al., 2020 ). In recent years, researchers have recommended the use of ICTs to survey ectothermic animals (Corva et al., 2023 ), including invertebrates (Amorim et al., 2022 ) in fields.…”