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Abstract Interconduit pit membranes, which are permeable regions in the primary cell wall that connect to adjacent conduits, play a crucial role in water relations and the movement of nutrients between xylem conduits. However, how pit membrane characteristics might influence water‐carbon coupling remains poorly investigated in cycads. We examined pit characteristics, the anatomical and photosynthetic traits of 13 cycads from a common garden, to determine if pit traits and their coordination are related to water relations and carbon economy. We found that the pit traits of cycads were highly variable and that cycads exhibited a similar tradeoff between pit density and pit area as other plant lineages. Unlike other plant lineages (1) pit membranes, pit apertures, and pit shapes of cycads were not coordinated as in angiosperms; (2) cycads exhibited larger pit membrane areas but lower pit densities relative to ferns and angiosperms, but smaller and similar pit membrane densities to non‐cycad gymnosperms; (3) cycad pit membrane areas and densities were partially coordinated with anatomical traits, with hydraulic supply of the rachis positively coordinated with photosynthesis, whereas pit aperture areas and fractions were negatively coordinated with photosynthetic traits; (4) cycad pit traits reflected adaptation to wetter habitats for Cycadaceae and drier habitats for Zamiaceae. The large variation in pit traits, the unique pit membrane size and density, and the partial coordination of pit traits with anatomical and physiological traits of the rachis and pinna among cycads may have facilitated their dominance in a variety of ecosystems from the Mesozoic to modern times.
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Ecology and evolution of cycad‐feeding Lepidoptera
Abstract Cycads are an ancient group of tropical gymnosperms that are toxic to most animals – including humans – though the larvae of many moths and butterflies (order: Lepidoptera) feed on cycads with apparent immunity. These insects belong to distinct lineages with varying degrees of specialisation and diverse feeding ecologies, presenting numerous opportunities for comparative studies of chemically mediated eco‐evolutionary dynamics. This review presents the first evolutionary evaluation of cycad‐feeding among Lepidoptera along with a comprehensive review of their ecology. Our analysis suggests that multiple lineages have independently colonised cycads from angiosperm hosts, yet only a few clades appear to have radiated following their transitions to cycads. Defensive traits are likely important for diversification, as many cycad specialists are warningly coloured and sequester cycad toxins. The butterfly family Lycaenidae appears to be particularly predisposed to cycad‐feeding and several cycadivorous lycaenids are warningly coloured and chemically defended. Cycad–herbivore interactions provide a promising but underutilised study system for investigating plant–insect coevolution, convergent and divergent adaptations, and the multi‐trophic significance of defensive traits; therefore the review ends by suggesting specific research gaps that would be fruitfully addressed in Lepidoptera and other cycad‐feeding insects.
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- Award ID(s):
- 1906333
- PAR ID:
- 10452106
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 23
- Issue:
- 12
- ISSN:
- 1461-023X
- Page Range / eLocation ID:
- p. 1862-1877
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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