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Abstract
Heat production in male cones is a trait known to be widespread in the modern cycad floras of Africa, Australia, and the New World; however, little data is available for this phenomenon in the Asian cycad flora. In this paper, heat production is documented in male cones of seven Asian Cycas species that are either restricted to China or have ranges that extend into China. These species belong in the sections Asiorientales, Stangerioides, and Indosinenses within the genus Cycas. Six of the seven species displayed temperatures that peak at 3–15°C above ambient in the late afternoon to early evening between 1730 and 2200 h. One species, C. revoluta, displayed weak but constant heat production at temperatures typically 2–3°C above ambient without a clear daily temperature spike. Temperature patterns may be related to the type of insect visitor or pollinator associated with the cones of each Cycas species. Most of those with daily peaks have curculionid and/or erotylid beetle cone visitors, while the one with no peak is pollinated by nitidulid beetles. The presence of thermogenesis in male cones of all seven Asian Cycas species investigated is additional evidence that cone thermogenesis is present throughout modern cycad floras and is observed in all extant cycad genera except for Stangeria.
Keywords: thermogenesis, cycad, Cycas, cones
